the extent of arsenic and of metal uptake by aboveground ... · the extent of arsenic and of metal...

The Extent of Arsenic and of Metal Uptake by AbovegroundTissues of Pteris vittata and Cyperus involucratus Growingin Copper- and Cobalt-Rich Tailings of the Zambian Copperbelt

Bohdan Krıbek • Martin Mihaljevic •

Ondra Sracek • Ilja Knesl • Vojtech Ettler •

Imasiku Nyambe

Received: 1 April 2010 / Accepted: 1 September 2010 / Published online: 15 October 2010

� Springer Science+Business Media, LLC 2010

Abstract The extent of arsenic (As) and metal accumula-

tion in fronds of the As hyperaccumulator Pteris vittata

(Chinese brake fern) and in leaves of Cyperus involucratus,

which grow on the surface of an old flotation tailings pond in

the Zambian Copperbelt province, was studied. The tailings

consist of two types of material with distinct chemical

composition: (1) reddish-brown tailings rich in As, iron (Fe),

and other metals, and (2) grey-green tailings with a lower

content of As, Fe, and other metals, apart from manganese

(Mn). P. vittata accumulates from 2350 to 5018 lg g-1 As

(total dry weight [dw]) in its fronds regardless of different

total and plant-available As concentrations in both types of

tailings. Concentrations of As in C. involucratus leaves are

much lower (0.24–30.3 lg g-1 dw). Contents of copper (Cu)

and cobalt (Co) in fronds of P. vittata (151–237 and

18–38 lg g-1 dw, respectively) and in leaves of C. invo-

lucratus (96–151 and 9–14 lg g-1 dw, respectively) are

high, whereas concentrations of other metals (Fe, Mn, and

zinc [Zn]) are low and comparable with contents of the given

metals in common plants. Despite great differences in metal

concentrations in the two types of deposited materials,

concentrations of most metals in plant tissues are very sim-

ilar. This indicates an exclusion or avoidance mechanism

operating when concentrations of the metals in substrate are

particularly high. The results of the investigation show that

Chinese brake fern is not only a hyperaccumulator of As but

has adapted itself to high concentrations of Cu and Co in

flotation tailings of the Zambian Copperbelt.

Although most metals and metalloids are toxic to plants, a

number of plants have been identified as metallophytes or

hyperaccumulators, which grow preferentially or exclu-

sively in soils containing high levels of toxic elements.

Hyperaccumulators (Salt et al. 1995; Brooks 1998; Boyd

2007) have attracted particular interest. Not only are they

able to grow in soils with high concentrations of toxic

elements, but they also accumulate these elements in their

stems and foliage in amounts that may be higher than the

levels lethal for other living organisms. This tolerance and

the capacity to accumulate metalloids and metals have

fueled the concept of remediating contaminated soils by

cultivating such plants and harvesting the aboveground

parts with their accumulated contaminants so that they can

be removed. This is the process of phytoremediation or,

more exactly, phytoextraction (Wenzel et al. 1999; Tu et al.

2002).

The recent discovery of an arsenic (As) hyperaccumu-

lator, the Chinese brake fern, Pteris vittata L., (Ma et al.

2001) has offered the hope that phytoextraction might be

B. Krıbek (&) � I. Knesl

Czech Geologic Survey, Klarov 3, 118 21 Praha 1,

Czech Republic

e-mail: [email protected]

M. Mihaljevic � V. Ettler

Institute of Geochemistry, Mineralogy and Mineral Resources,

Faculty of Science, Charles University, Albertov 6, 128 43 Praha

2, Czech Republic

O. Sracek

OPV s.r.o. (Protection of Groundwater Ltd.), Belohorska 31,

169 00 Praha 6, Czech Republic

O. Sracek

Department of Geology, Faculty of Science, Palacky University,

17. listopadu 12, 771 46 Olomouc, Czech Republic

I. Nyambe

Department of Geology, School of Mines, University of Zambia,

P.O. Box. 32 379, Lusaka, Zambia

123

Arch Environ Contam Toxicol (2011) 61:228–242

DOI 10.1007/s00244-010-9604-4

developed into an efficient, environmentally friendly, and

cost-effective technology for As decontamination (Tu et al.

2002). This fern can accumulate B22.6 g kg-1 As (dry

weight [dw]) in its fronds, that is, 2% As in the above-

ground biomass. The As in the aboveground tissues of this

fern is much higher than that found in most common plant

species (\10 mg kg-1; Matschullat 2000). The biocon-

centration factor (a ratio of frond As concentration to soil

As concentration) is[10 (Ma et al. 2001; Zhao et al. 2002).

Knowledge of the mechanisms of As uptake and

detoxification in Chinese brake fern may contribute to

optimization of phytoremediation processes (Clemens et al.

2002). Recent advances in understanding the mechanisms

of As absorption, translocation, and compartmentalization

within the vacuoles of P. vitatta cells have provided novel

insights into plant physiology and the molecular biology of

phytoremediation (Meharg and Hartley-Whitaker 2002;

Tripathi et al. 2007; Zhao et al. 2009; Xie et al. 2009).

Recently, many As hyperaccumulators have been iden-

tified in different regions of China, Southern Thailand,

Scotland, Australia and North America. The majority of

them are ferns of the genus Pteris (Meharg et al. 1994; Ma

et al. 2001; Chen et al. 2002a; Du et al. 2005; Srivastava

et al. 2006; Wang et al. 2007; Koller et al. 2007). Although

great progress in understanding the uptake, transport, and

detoxification of As in P. vittata has been made (Xie et al.

2009), data on the uptake of metals by this species, espe-

cially in heavily contaminated environment, are limited.

In the area of the Zambian Copperbelt, P. vittata grows

not only in contaminated soils but also in copper (Cu)- and

cobalt (Co)-rich tailings dumped in numerous tailings

ponds. Therefore, the main objectives of the current

investigation were as follows:

1. Collect information on the characteristics of the

tailings and conditions governing growth of P. vittata

in tailings deposited in the Copperbelt impoundments.

2. Determine the amount of As, Cu, Co, and other metals

in P. vittata relative to the contents of these metals in

two different types of tailings.

Although most studies have been focused on the mecha-

nism of As uptake by P. vittata, a few studies have directly

compared As uptake by this plant with As uptake by other

plants growing at the same sites. Therefore, the accumulation

of As and metals by P. vittata in Zambia was compared with

that by Cyperus involucratus Rottb. growing together with

P. vittata in tailings of the Copperbelt impoundments.

Site Description

Mining has shaped the landscape of the Zambian Copper-

belt during several centuries. The area hosts one of the

world’s highest-grade resources of Cu and Co ore and is

estimated to contain 34% and 10% of global Co and Cu

reserves, respectively (United States Geological Survey

[USGS] 2010). As a result, the Copperbelt supports one of

the highest densities of large-scale commercial mining

operations in the world (Krıbek et al. 2010). The Copper-

belt sediment-hosted strata-bound and stratiform deposits

are characterized by finely disseminated Cu, Co, and iron

(Fe) sulphides. The principal minerals are chalcopyrite,

Co-rich pyrite, and bornite ± carrolite. The host rocks

include quartzite (arkose), shale, and dolomite. The grades

average 3 wt% Cu and 0.18% Co in ore deposits from

which both metals are extracted. Trace amounts of gold

(Au), platinum (Pt), and silver (Ag) are recovered from the

Cu slimes during the refining process. Approximately 30

million metric tonnes of Cu metal have been produced

since large-scale mining operations began in 1930

(Kamona and Nyambe 2002). The extracted ore is pro-

cessed by flotation or by chemical treatment. The flotation

tailings are usually dumped in tailings ponds constructed

mostly in areas of wetland, locally called ‘‘dambos.’’ The

dambos are usually the source of streams and rivers. Such

systems are ubiquitous throughout the Copperbelt, forming

6–10% of the land surface (Mendelsohn 1961; Limpitlaw

2002). Active tailings ponds are usually entirely free of

vegetation. However, the surface areas of old tailings

ponds have gradually become partly or entirely colonised

by Cu- and Co-tolerant plants.

Field Survey

Numerous flotation tailings ponds can be found in the

Chambishi region of the Zambian Copperbelt (Fig. 1a, d).

One of these is an old tailings pond north of Chambishi

(‘‘Chambishi-North’’) and is described in this study. A field

survey on the old Chambishi-North pond (E 28�01034.000 to

28�01053.200, S 12�37032.700 to 12�37035.500, total area

352.5 ha), located approximately 1 km west of Chambishi

town in the Copperbelt province of Zambia, was under-

taken during June to July in 2002, 2008, and 2009. Based

on the results of this survey, the area of old impoundment

can be subdivided into four vegetation zones (Fig. 1d) as

follows:

1. Reed swamp zone: The central part of the tailings pond

around the lagoon is dominated by dense growth cover

of Phragmites mauritianus Kunth, but Typha doming-

ensis Pers. is a common associate. Individual plants of

Phragnites and Typha reach almost 2 m in height. In

some places, Phragmites and Typha monoculture is

fringed by stands of Eleocharis dulcis (Burm. F.)

Hensch.

Arch Environ Contam Toxicol (2011) 61:228–242 229

123

2. Tailings essentially without vegetation: A great part of

the tailings impoundment, between the reed swamp

and peripheral papyrus and fern zone, is essentially

free of vegetation apart from some isolated stands of

P. mauritianus. Individual plants of Phragmites reach up

to 1 m in height. This zone is fully exposed to sunlight.

3. Papyrus and fern zone: The peripheral zone of the

tailings pond is dominated by stands of C. involucratus

and P. vittata together with minor P. mauritianus

and T. domingensis. In some places, clusters of

C. involucratuss and P. vittata give way to patches

that are entirely free of vegetation. The surface of the

tailings in this zone is partly covered with efflores-

cences of gypsum, which indicate strong capillary

action of groundwater during the dry season. On many

stands, P. vittata is associated with the vigorous

perennial sedge Bulbostylis pseudoperenis Goetgh.

Toward the banks of the impoundment, the vegeta-

tion cover becomes denser, and C. involucratus and

P. vittata form thickets together with other common

species, such as C. imbricatus Retz., E. dulcis,

Lagarosophon ilicifolius Oberm. and Kotschya Afri-

cana Endl. Dense vegetation cover is usually clustered

around extensive stands of C. papyrus L., which partly

overshadows this zone. Individual plants of C. papyrus

reach up to 3 m in height.

4. Mixed semideciduous tree forest zone: The transition

from the papyrus and fern zone of the peripheral parts

of the tailings impoundment to the mixed semidecid-

uous tree forest zone at the banks of the impoundment

is gradual. The fern- and papyrus-dominated vegeta-

tion is within a distance of 5 m replaced with Acacias

COPPERBELT

CONGO DR

ZAMBIA

Chililabombwe

Chingola

Chambishi

Kalulushi

Kitwe

Mufulira

Luanshya

Ndola

Kafue river

Kafue river

50 km

Old tailings pondChambishi-North

South Africa

Lesotho

Swaziland

BotswanaNamibia

Zimbabwe

Zambia Malawi

Angola

DR CongoTanzania

Chambishi MineComplex

CHAMBISHI

0 km 10 km

Kafue


New tailings pondChambishi-North

Musakashi

Cham

beshi

Lukashi

New tailingspond CambishiSouth (TD6)

Chambishi-Southwetland

1 km

N


Lagoon

12

Dischargepoint

Reed swamp Tailings without vegetation

Papyrus and fern swamp

Tree mixed semi-deciduous forest

Road

plot1 Sampling

A

C D

B

Fig. 1 Position of Zambian Copperbelt within Central Africa (a),

synoptic map of the Copperbelt (b), lay of the old Chambishi-North

and other tailings ponds in the Chambishi region (c), and distribution

of vegetation zones with sampling sites within the old Chambishi-

North tailings pond (d)

230 Arch Environ Contam Toxicol (2011) 61:228–242

123

and shrubby species. The most common species

include Acacia polyacantha Willd. and A. sieberana

DC together with Albizia versicolor Welw. Ex Oliv.

and Manilkara obovata (Sabine & G.Don) J. H. Hemsl.

Among the most important shrubby species are

Craterispermum laurinum (Poir.) Benth., Garcinia

smeathmannii (Planch. & Triana) Oliv. and Gardenia

imperialis K. Schum. Within the forest zone, P. vittata

locally forms dense stands in shady places spoiled by

escapes of the slurry from pipelines used in the past for

transporting tailings material to the impoundment.

Four sampling plots of 1 m 9 1 m were located in the

papyrus and fern zone (Fig. 1d). For each plot, tailings

samples were taken randomly from the top 20 cm to deter-

mine their physical and chemical properties. At least three

individuals of selected plants, together with tailings samples

taken closely to the root system, were collected from indi-

vidual plots. Moreover, groundwater was collected from a

shallow trench (30-cm deep) excavated in the central part of

the papyrus and fern zone (sampling plot 1; Fig. 1d).

Water, Tailings, and Plant Analysis

A sample of groundwater was taken from a shallow trench

excavated in the papyrus and fern zone using a syringe

equipped with a disposable microfilter (pore size 0.45 lm).

After stabilization of pH, the water sample was split into

one subsample acidified with ultrapure HCl for determi-

nation of cations and metals plus a second unacidified

subsample. The alkalinity of the unacidified subsample was

determined by titration with HCl in a field laboratory using

a Gran plot to determine the end point. Cations in the

acidified water subsample were determined using induc-

tively coupled plasma–mass spectrometry in the Acme

Analytic Laboratories, Vancouver, Canada. Concentrations

of anions in the unacidified water subsample were deter-

mined using a high-pressure Shimadzu LC6A liquid

chromatograph in the accredited Central Laboratories of

the Czech Geologic Survey in Prague.

Tailings samples were air-dried, and after homogeniza-

tion, half of each sample was passed through a 2-mm mesh

screen using a USGS sieving set and pulverized in an agate

ball mill to \0.063 mm mesh. To determine the total

content of metals, tailings samples were digested with aqua

regia in accordance with the ISO 11466 procedure (Inter-

national Organization for Standardization 1995). For the

determination of plant-available metals, samples were

extracted with a solution of diethylentriaminepentaacetic

acid (DTPA) and triethanolamine (TEA) according to the

ISO/DIS 14870 method (International Organization for

Standardization 2001).

All reagents were declared pro analysi, and all solutions

were prepared with double-distilled water. Standard

working solutions were prepared from original certified

stock solutions (MERCK) concentration 1000 mg of

chemical element l-1 in 1% super pure HNO3. Co, Cu, Fe,

Mn, and Zn were determined using flame atomic absorp-

tion spectroscopy (FAAS; Perkin Elmer 4000 spectrome-

ter). As was determined using hydride-generation atomic

absorption spectrometry (HGAAS; Perkin Elmer 503).

All tailings samples were analyzed at the accredited

Central Laboratories of the Czech Geologic Survey. The

quality-control procedure involved analysis of reagent

blanks, duplicate samples, and several reference materials

(RMs). Analytic precision was determined by duplicate

analysis of 10% of randomly chosen samples and of ref-

erence samples as well. The coefficient of variation for all

investigated elements was \8%. Reliability of analyses

determined by RMs was ± 5% for Co, Cu, and Zn; ± 12%

for Fe and Mn; and ± 10% for As.

Sequential extraction for selected samples was per-

formed using the BCR procedure (Rauret et al. 1999) The

following sequence of steps was used: a 0.11 M acetic acid

(CH3COOH) step targeting exchangeable- and acid-soluble

fraction; a 0.5 M hydroxylamine–chloride (NH2OH�HCl)

step targeting reducible fraction (mostly poorly crystalline

Fe/Mn oxides); an oxidisable step (8.8 M H2O2/1 M

CH3COONH4 extractable) targeting organic matter and

sulphides; and an Aqua Regia step targeting the residual

fraction. The full details of the experimental procedure are

given in Rauret et al. (1999).

The amount of total carbon (Ctot) was determined using

an ELTRA CS 500 instrument. Samples were combusted at

1400�C, and Ctot was measured as carbon dioxide using an

infrared (IR) detector. The amount of carbonate carbon

(Ccarb) was established using another ELTRA CS 500

instrument. Samples were digested in a saturated solution

of H3PO4, and the amount of CO2 liberated was recalcu-

lated to that of Ccarb. The amount of organic carbon (Corg)

was determined by subtraction of Ccarb from Ctot content,

i.e., Corg = Ctot - Ccarb. Total sulphur (Stot) was deter-

mined using the ELTRA CS 500 equipment. Samples were

combusted at a temperature of 1400�C, and the Stot, mea-

sured as released SO2, was determined by an IR detector.

The variation coefficient for Ctot and Ccarb is \0.5%, and

for Stot it is \1%. Relative errors of Ctot, Ccarb, and Stot

determined using reference materials were ±2.5% for Ctot

and Stot and ±2% for Ccarb.

To establish the pH value of tailings leachates, 2.5 g

material, sieved through 2-mm sieve mesh, were leached in

a periodically shaken solution of 1 M KCl. The pH mea-

surements were made with a precision of 0.01 pH unit

using a pHC 2085 pH electrode connected to a PHM 201

pH meter after 24 h of leaching. Differences in water


123

temperature were automatically compensated using a T 201

temperature compensator. Calibrations were performed

using two standard IUPAC (Radiometer A/S, Copenhagen,

Denmark) buffers with pH values of 4.01 and 7.00,

respectively. The measured pH value was recorded auto-

matically with a precision of 0.01 pH unit.

Fresh plant materials (200-g weight) were washed

thoroughly with tap water, cleaned with distilled water, and

then separated into roots and shoots. All plant parts were

then oven-dried (65�C for 48 h). The plant tissues were

then cut into small pieces and pulverized in an agate ball

mill to \0.063 mm mesh. Approximately 1-g aliquots of

the plant samples were burned down in a muffle oven.

A temperature programme from 25�C to 550�C was

employed, with a temperature increase of 2�C/min, and

then the temperature was kept at 550�C for 2 h. The

amount of resulting ash was weighed, and the metals were

analytically determined in HNO3 and HCl at 5:1 (v/v)

leachate. As and metals were analysed in leachate as

described previously. Due to the requirements for precision

in As and metals analyses, standard RMs (SRM 1575a pine

needles and SRM 1515 apple leaves) were used for plant

samples. Relative errors determined using reference

materials were ±9.9% for Cu, ±10.8% for Fe, ±7.3% for

Mn, and ±11.4% for Zn. The relative error for As was

higher (±28%) due to a low concentration of this element

in SRMs (0.038 and 0.039 lg g-1, respectively).

Because of the high volatility of As during combustion

of plant samples, selected samples of plants were there-

fore analyzed without combustion using x-ray fluores-

cence (XRF) spectrometry (XRFARL 9400 ADVANTXP;

Applied Research Laboratories, Switzerland). The results

of both methods, i.e., the analyses of burnt samples using

the FAAS method and those of unburnt samples using the

XRF method showed a significant correlation (r = 0.994)

on the probability level of p \ 0.01. However, As con-

centrations established by the XRF method turned out to be

on average 15% higher than values obtained by FAAS

method in plants ash, especially in case of low As con-

centrations in plant material (\1 lg g-1 dw).

The accumulation of Fe and aluminium (Al) by plant

roots in Chambishi-North was studied using an optical

microscope and CamScan 3200 electron microprobe in

scanning electron microscopy mode equipped with an

energy-dispersive analyzer LINK-ISIS.

Statistical Methods

The tailings at Chambishi-North consist of reddish-brown

and grey-green material. Seven samples of P. vittata fronds

and five samples of C. involucratus leaves were collected

from reddish-brown tailings, and five samples of P. vittata

and six samples of C. involucratus were collected from

grey-green tailings. Data are presented as arithmetic

mean ± SD for plants growing in reddish-brown and grey-

green tailings. Values were calculated using S-Plus

programme version 4.5 (MathSoft, Seattle, WA). Further

statistical analysis was not deemed appropriate due to the

small number of samples. The bioaccumulation factor (BF)

is defined as the ratio of As or metal concentration in

shoots (total dw) to that in tailings, which is a measure of

the ability of a plant to take up and transport metals to the

foliage (Caille et al. 2005). The translocation factor, indi-

cating preferential partitioning of metals and defined as the

metal concentration in the plant foliage divided by that in

the roots (McGrath and Zhao 2003), was not calculated

because it was not possible to separate completely the roots

of the plants from the Fe- and Al-rich particles of tailings.

Results

Groundwater

The groundwater sampled in the old Chambishi-North tail-

ings pond has a pH of 7.16 and high specific conductivity

(1860 lS cm-1). The dominant cation is Ca (654.7 mg l-1),

but the concentrations of Mg (99.8 mg l-1) and potassium

(51.7 mg l-1) are also significant. Sulphate (2149 mg l-1) is

the principal anion; the concentration of bicarbonate is much

lower (393.12 mg l-1); and the chlorine concentration

is negligible. Concentrations of Fe (60 lg l-1) and Al

(20 lg l-1) are low compared with Mn (2085 lg l-1).

Respective concentrations of Cu and Co are 687 and

637 lg l-1, respectively. The concentration of As is

54 lg l-1 and that of Zn is 22 lg l-1.

Tailings

The tailings consist of two types of material with distinct

chemical compositions: (1) reddish-brown tailings rich in

total As, Fe, and other metals, and (2) light grey-green

tailings with lower contents of total As, Fe, and other

metals, apart from Mn (Table 1).

Reddish-brown tailings occupy most of the fern and

papyrus zone, whereas grey-green tailings occur mostly in

the central part of the tailings pond (i.e., in the reed swamp

zone) close to the central lagoon. In many places, however,

grey-green tailings form a layer up to 0.5 m thick, which

overlies reddish-brown tailings, especially in the fern and

papyrus vegetation zone. The pH of the tailings leachate

ranges from near-neutral to slightly alkaline, with an

average pH of 8.19 in reddish-brown and 7.23 in light grey-

green tailings. The mean concentration of Corg and Ccarb


123

are higher in reddish-brown (0.29% and 1.33%, respec-

tively) compared with grey-green tailings (0.04% and

0.75%, respectively). The mean concentration of Stot is

much higher in reddish-brown (0.91%) than in light grey-

green tailings (0.25%).

Concentrations of plant-available As and metals were

determined by extraction with DTPA and TEA (Table 1).

The amounts of plant-available As and metals (expressed

as % of the total concentration of As and metals in the

tailings) show roughly similar trends in both tailings types

(Fig. 2). For reddish-brown tailings, the amount of plant-

available As and metals increases in the following

order: Fe (0.06%), ? As (1.53%), ? Cu (3.62%), ? Co

(4.36%) ? Mn (6.72%), ? Zn (14.81%). In grey-green

tailings, the amount of plant-available As and metals is

slightly different but increases in a similar sequence:

Fe ? (0.61%), ? As (1.15%), ? Co (1.84%), ? Cu

(3.35%), ? Mn (4.41%), ? Zn (5.34%).

It is pointed out that the methods of determination

of plant-available metals extracted with DTPA, as well

as with other similar chelating agents, were developed

for establishment of cation forms of metals. Therefore,

for better evaluation of the plant-availability of As, a

sequential analysis was used, particularly its first step

consisting of extraction of samples by 0.11 M acetic acid.

The results of sequential analyses of reddish-brown and

Table 1 Average concentration (mean value) of Ccarb, Corg, and Stot (all in wt%), total (T), and plant-available (PA) As and metals (in lg g-1)

and average pH value of reddish-brown and grey-green tailings at the old Chambishi-North impoundment, Zambia

Element Reddish-brown tailings (n = 12) Grey-green tailings (n = 14)

Mean SD Max Min Mean SD Max Min

pHleachate 8.19 0.16 8.23 7.95 7.23 0.07 7.32 7.12

Corg 0.29 1.18 0.01 0.64 0.04 0.01 0.04 0.02

Ccarb 1.33 0.41 2.32 1.07 0.75 0.03 0.44 0.08

Stot 0.91 0.55 0.30 1.92 0.25 0.16 0.44 0.06

As

T 175.26 17.18 211.08 156.86 18.81 9.36 43.33 9.21

PA 2.68 0.68 3.79 1.67 0.28 0.32 0.79 9.07

Co

T 3088 1881 8710 1690 272 182 663 148

PA 132 73 328 67 7 9 25 1

Cu

T 11,294 2174 14,200 7900 1728 633 2790 750

PA 738 253 1005 94 393 125 530 200

Fe

T 253,500 20,851 280,000 200,000 28,975 19,801 71,500 15,400

PA 141 38 207 89 121 24 148 80

Mn

T 268 169 810 130 0.018 0.005 0.027 0.01

PA 16 4 20 12 1066 181 1290 680

Zn

T 57 49 209 32 47 15 65 20

PA 8 8 29 2 40 3 47 35

n Number of analysed samples

As Co Cu Fe Mn Zn

20

15

10

5

0

Chemical element

Pla

nt-a

vaila

ble

amou

nt o

f ele

men

ts

(in %

of t

otal

con

cent

ratio

n)

Fig. 2 Average concentration (mean value) of plant-available

(DTPA- and TEA-extracted) As and metals in reddish-brown tailings

(white column, n = 11) and in grey-green tailings (black column,

n = 9) in the Chambishi-North pond in % average total concentration

of elements in tailings. The bar on top of the column is the SD


123

grey-green tailings (Fig. 3) generally correspond with the

results obtained from the determination of the amount of

DTPA- and TEA-extractable elements.

Almost all Fe ([95% of the total content of Fe in the

analysed samples) is retained in the residual fraction.

Together with Fe, most of the As (60–65% of the total As

content of analysed samples) and Zn (55–60%), as well as

high amounts of Co (40–55%), Cu (30–50%), and Mn

(30–40%), are confined to the residual fraction.

The content of metals in the oxidizable fraction, i.e., the

amount of metals confined to sulphides and organic matter

is relatively small (\3%), with the exception of Cu

(20–45%). Particularly As (20–25%), Co and Cu (15–20%)

and, to a lesser extent, Zn (10–15%) are confined to the

reducible fraction, i.e., to poorly crystallized oxides of Fe

and Mn. Relatively high contents of Mn (40–65%) and Co

and Zn (25–35%) are released into the acid-extractable

fraction. Contents of As and Cu in this fraction are lower

(10–20%), whereas contents of Fe are negligible (\2%).

Elements retained in acid-extractable fraction are believed

to be confined to carbonates, absorbed on the surface of

minerals by ion-exchange processes or present in the form

of water-soluble mineral species. The amount of As in

acid-extractable fraction of the sequential analysis is higher

(10–15% of total As) compared with the amount of plant-

bioavailable As determined by extraction with DTPA and

TEA (1–1.5% of total As) because of a weak capacity of

chelating agents used to extract anions.

Arsenic and Metals in Plants

The metal concentrations in fronds of P. vitatta and in

leaves of C. involucratus were investigated in plants

growing in reddish-brown as well as in grey-green tailings.

The results of this study and the BF values versus tailing

types are listed in Tables 2 and 3. Mean concentrations

of As in P. vittata fronds were found to be very high in

samples collected in reddish-brown tailings (mean

3390 lg g-1 dw; Table 2) and even higher in samples

collected in grey-green tailings (mean 5534 lg g-1 dw,

Table 3 and Fig. 4a). Because of the much higher con-

centrations of As in reddish-brown tailings, the BF of

samples collected in this type of tailings is substantially

lower (BF = 18; Table 2 and Fig. 4b) compared with that

of samples taken from grey-green tailings (BF = 184),

regardless of very similar concentrations of As in plants.

This indicates that the BF value does not necessarily reflect

the capacity of plants to accumulate As (and metals) from

substrates. In case of the Chambisi-North tailings, the

much higher BF of fern growing in grey-green tailings does

not indicate higher capacity of As bioaccumulation but

simply reflects lower concentration of As in such tailings.

Concentrations of metals in fronds of ferns growing in

both types of tailings decrease in the following sequence:

Fe ? Cu ? Mn ? Co, Zn, and the BFs decrease in the

following order: Zn, ? Mn, ? Cu, ? Co, ? Fe. With

an exception of Mn, the BFs of all metals are higher in

ferns growing in grey-green compared with those growing

in reddish-brown tailings.

Compared with P. vittata, the concentration of As in

samples of C. involucratus collected from the same sam-

pling plots is substantially lower. However, concentration

of As in C. involucratus, as well as the BF value, is one

order higher in the foliage of specimens growing in red-

dish-brown tailings (mean 25.3 lg g-1 dw, BF = 0.20)

compared with specimens growing in grey-green tailings

(mean 0.46 lg g-1, BF = 0.04).

The mean concentration of metals in the foliage of

C. involucratus decrease in the following order: Fe ?Cu ? Mn ? Co, Zn. Compared with P. vittata, concen-

trations of metals are slightly lower, with the exception of

Mn. The BFs decrease in the following order: Zn, ? Cu,

Co ? Fe. The BF for Cu is one order higher in the foliage

of plants growing in metal-poor tailings (BF = 0.11)

compared with those growing in metal-rich tailings

(BF = 0.01). Like in the case of As, this difference does

not reflect a different capacity of the plant to accumulate

0%

20%

40%

60%

80%

100%

Dis

trib

uti

on

(in

% o

f to

tal a

mo

un

t)D

istr

ibu

tio

n (

in %

of

tota

l am

ou

nt)

Co Cu Zn As Mn FeChemical element

Residual Oxidizable Reductible Acid extractable

Residual Oxidizable Reductible Acid extractable

0%

20%

40%

60%

80%

100%

Co Cu Zn As Mn Fe

Chemical element

A

B

Fig. 3 Distribution of As and metals extracted in individual steps of

sequential analysis of reddish-brown (a) and grey-green tailings (b) in

the old Chambishi-North tailings pond in Zambia


123

Cu but simply the different Cu concentrations in deposited

tailings.

Discussion

Chemical Composition of Groundwater in Relation

to the Concentration of As and Metals in Plants

The pH value and concentrations of Ca and Mg in

groundwater collected from a shallow trench (30-cm depth)

in the old Chambishi-North tailings pond correspond with

data by Sracek et al. (2010), who reported pH value of 7.5

and concentrations of Ca and Mg corresponding to 568 and

67 mg l-1, respectively, in a groundwater sample collected

at the old Chambishi-North tailings pond from a depth of

approximately 3.0 m. In contrast, concentrations of bicar-

bonate and sulphate in our groundwater sample (SO4

2149 mg l-1, HCO3 393 mg l-1) are higher compared with

data reported by Sracek et al. in 2010 (SO4 1820 mg l-1;

HCO3 71.4 mg l-1), presumably due to evaporation of

groundwater in the shallow part of tailings. High concen-

tration of sulphate in groundwater from the shallow part of

Table 2 Average total concentration of chemical elements in aboveground tissues of plant species (in lg g-1 dw, mean value ± SD) in their

associated reddish-brown tailings (in lg g-1) and BF values

Element P. vittata (n = 7) C. involucratus (n = 5)

Frond ± SD Tailings ± SD BF Leaf ± SD Tailings ± SD BF

As 3389.9 ± 885.8 180.41 ± 18.2 19.28 25.3 ± 3.6 168.0 ± 9.3 0.20

Co 28.2 ± 7.2 3706.11 ± 2257.3 0.01 13.3 ± 1.1 2222.5 ± 285.3 0.01

Cu 164.1 ± 39.3 12287.11 ± 2210.4 0.01 112.2 ± 14.3 9902.3 ± 1 089.3 0.01

Fe 663.0 ± 43.2 250571.01 ± 24070.0 0.003 144.2 ± 112.6 257600.0 ± 14 264.0 0.002

Mn 35.2 ± 9.1 321.31 ± 202.1 0.14 43.3 ± 1.3 193.1 ± 36.2 0.22

Zn 20.2 ± 5.3 75.41 ± 59.4 0.39 10.1 ± 2.3 33.0 ± 1.0 0.32

n Number of analysed plants and tailings samples

Table 3 Concentrations of chemical elements in aboveground tissues of plant species (in lg g-1 dw, mean value ± SD) in their associated

grey-green tailings (in lg g-1) and BF values

Element P. vittata (n = 4) C. involucratus (n = 4)

Shoot ± SD Tailings ± SD BF Shoot ± SD Tailings ± SD BF

As 5533.8 ± 532.6 32.35 ± 7.5 184.45 0.46 ± 0.18 12.45 ± 3.2 0.04

Co 28.1 ± 3.2 551 ± 88.2 0.05 9.0 ± 1.1 163.2 ± 6.0 0.02

Cu 216.3 ± 10.3 2560 ± 395.2 0.01 112.3 ± 23.2 1114.3 ± 342.4 0.11

Fe 546.2 ± 31.1 59000.0 ± 10254.0 0.009 253.1 ± 35.2 15967.2 ± 475.3 0.016

Mn 45.2 ± 1.3 810.1 ± 125.2 0.06 41.2 ± 1.1 1135.2 ± 79.3 0.04

Zn 28.1 ± 4.1 42.2 ± 1.1 0.67 12.1 ± 4.0 42.3 ± 4.3 0.29

n Number of analysed plants and tailing samples

CuCoAs0.001

0.01

0.1

1

10

100

1000

Chemical element

Bio

accu

mul

atio

n fa

ctor

(B

F)

ZnMnFe

As Co Cu

10000

1000

100

10

1

0.1

Chemical element

Con

cent

ratio

n, p

lant

(uµ

g.g-1

DW

)

ZnMnFe

natattiv.P , reddish-brown tailings ( = 7) P. vittata n, grey-green tailings ( = 5)

nsutarculovnI.C , reddish-brown tailings ( =5) C. Involucratus n, grey-green tailings ( = 6)

Fig. 4 Average concentration (mean value) of As and metals in

P. vittata fronds and C. involucratus leaves (a) and mean BF values

(b) for both plants growing in reddish-brown and grey-green tailings

in the Chambishi-North pond. The bar on top of the column is the SD.

n = Number of analysed samples


123

the deposited material at the old Chambishi-North tailings

pond resulted in formation of gypsum on the surface of

tailings. The concentration of dissolved manganese (Mn),

Cu, and Co (2085, 687, and 637 lg l-1, respectively) in

groundwater sample collected from a shallow trench is

high, whereas the contents of Al Fe, Zn, and As (20, 60, 22,

and 54 lg l-1, respectively) are lower. The contents of As

and metals in groundwater are believed to vary over the

whole of the tailings pond being governed by precipitation

of respective mineral phases, by their coprecipitation, and

by cations exchange processes or by chemisorption,

depending on physical properties of either type of dumped

materials. However, it is obvious that the accumulation

ratio (AR) for As for P. vittata calculated using the fol-

lowing equation:

AR

¼ Arsenic ðmetalsÞconcentration inplant ðmg kg�1; DWÞArsenic ðmetals) concentration ingroundwater ðmg 1�1Þ;

which is a few orders of magnitude higher compared with

C. involucratus (Table 4). The AR for Fe appears relatively

high due to its low concentration in groundwater. As

concerns the other elements, the AR values are of the same

order of magnitude, which indicates their passive uptake by

both plants.

Chemical Composition, Mineralogy, and Origin

of Tailings

The results of chemical analyses proved two types of

material to have been deposited in the old Chambishi-

North tailings pond. The reddish-brown tailings are rich in

hematite and/or poorly crystalline Fe(III) phases and gyp-

sum (Sracek et al. 2010), which corresponds to high con-

centration of total Fe (mean 25 wt%) and Stot (mean

1.3 wt%; Table 1). A small part of sulphur is confined to

residual sulphides (chalcopyrite, bornite, and pyrite; Sracek

et al. 2010). High concentrations of total Cu and Co reflect

geochemical composition of extracted ore, and high

amount of Ccarb (mean 1.33%) indicates an occurrence of

carbonates (calcite). The reddish-brown tailings were most

likely produced by in situ deep tropical weathering of

flotation wastes initially deposited in the tailings pond.

In contrast, the grey-green tailings exhibit lower content

of total Fe (2.8 wt%), Stot (0.25 wt%), and Ccarb

(0.04 wt%; Table 1). Compared with reddish-brown tail-

ings, they show higher contents of quartz and aluminosil-

icates (muscovite, amphibole, and orthoclase; Sracek et al.

2010) and are poor in sulphides. Consequently, the con-

centrations of total As, Cu, Co, and other metals are gen-

erally low. The only exception is a high concentration of

total Mn (mean 1066 mg g-1), which is likely to be linked

with carbonates or with poorly crystallised Mn oxides.

Nevertheless, the origin of grey-green tailings is not evi-

dent. It can only be assumed that these tailings represent a

product of redeposition and deferrification of reddish-

brown tailings under reducing conditions during periods of

inundation of the tailings pond during rainy seasons. An

increase in thickness of grey-green tailings from the

peripheral to central part of the pond with intermittent

lagoon supports this hypothesis.

Table 4 Accumulation ratio (average total concentration of elements in plant, mean value, mg kg-1 dw)/concentration of elements in

groundwater [mg l-1]) for P. vittata and C. involucratus growing in reddish-brown and grey-green tailings at Chambishi-North pond

Element P. vittata reddish-brown

tailings (n = 7)

P. vittata grey-green

tailings (n = 5)

C. ivolucratus reddish-brown

tailings (n = 5)

C. involucratus grey-green

tailings (n = 6)

AR.103

As 6275.9 10246.3 468.5 0.85

Co 0.04 0.04 0.02 0.01

Cu 0.24 0.31 0.24 0.16

Fe 11.1 9.11 2.41 4.21

Mn 0.051 0.022 0.021 0.019

Zn 0.92 1.31 0.46 0.55

n Number of analysed plant samples

Table 5 Correlation coefficients (r) between total and plant-available

(extraction with DTPA and TEA) concentration of elements in tail-

ings from the old Chambishi-North impoundment in Zambia

Element Reddish-brown

tailings (n = 12)

Grey-green

tailings (n = 14)

Astotal–Asplant-available 0.54 0.86

Cototal–Coplant-available 0.95 0.98

Cutotal–Cuplant-available 0.92 0.93

Fetotal–Feplant-available 0.37 –0.86

Mntotal–Mnplant-available 0.92 0.86

Zntotal–Znplant-available 0.87 0.65

Significant correlations on the probability level p \ 0.05 (95%) are

printed in bold

n Number of samples


123

The concentrations of plant-available As, Co, Cu, Mn,

and Zn, as established by extraction with DTPA and TEA,

show significant correlation with total contents of the given

elements in both types of tailings (Table 5). Therefore, the

concentrations of plant-available As, Co, Cu, and Mn

increase proportionally with an increase of their total

concentrations in tailings. Fe is the only metal for which

the value of correlation coefficient is low (Table 5), indi-

cating extremely low plant-availability of this element

regardless of the total amount of Fe in tailings.

Results of the determination of plant-available elements

correspond with the results of sequential analyses, in which

almost all Fe ([95% of the overall content of Fe in ana-

lysed samples) is retained in the residual fraction. The

distribution of As and metals in individual fractions of

sequential analysis (Fig. 3) is similar in both reddish-

brown and grey-green tailings, which indicates that all of

the analysed elements are present in the same chemical

forms in either type of the substrate. The only exception is

Cu, which is more abundant in the oxidizable fraction of

reddish-brown tailings because of a higher amount of

sulphides and organic matter compared with grey-green

tailings. The most important thing, from the point of view

of plant availability, is the amount of chemical elements in

the acid-extractable fraction. However, the applied method

of sequential analysis does not allow us to distinguish to

what extent the chemical elements are confined to the

surface of individual mineral phases by ion-exchange

processes or to what degree they are confined to or con-

tained as isomorphic admixture in carbonates within the

given (acid-extractable) fraction. This particularly applies

to Mn, of which the contents in carbonates may be high. In

contrast, large amount of metals can be absorbed on the

surface of amorphous Fe- and/or Mn-hydrated oxides.

Metal affinity to amorphous Fe oxides in general increases

in the following range: Cu [ Zn [ Co [ Mn (McKenzie

1980), which corresponds to higher amount of Mn, Co, and

Zn and lower amount of Cu in acid-extractable fraction of

sequential analysis of tailings. At higher values of pH, even

anions such as AsO33- can be absorbed on the surface of

amorphous Fe oxides or hydroxides due to negatively

charged sites, which begin to prevail on the surface of the

solid phase (Drever 1997). For example, Otte et al. (1995)

reported high amount of As to be retained on Fe plaques on

the surface of wetland plant roots.

As in Plants and Relation to Tailings

Concentrations of As in fronds of P. vittata growing on the

surface of the old Chambishi-North tailings pond

(2350–6200 lg g-1) are comparable with or slightly lower

than those detected in the same plant by other investigators

(3000–22,000 lg g-1 dw; Matschullat 2000; Cao et al.

2004; Lombi et al. 2002; Ma et al. 2001; Tu and Ma 2003).

Despite much higher contents of total and plant-available

As in reddish-brown compared with grey-green tailings

at Chambisi-North, concentrations of As in fronds of

P. vittata growing in both tailings types are similar or even

higher in plants growing in grey-green tailings (Fig. 5a).

Many investigators have reported that contents of As in

fronds of P. vittata increase with the increase of As in the

substrate (for survey see Xie et al. 2009). However,

Gumaelius et al. (2004) concluded that the uptake of As in

gametophytes of P. vittata follows a linear relation at lower

concentrations of As in substrate and then levels off at high

concentrations. This indicates an exclusion or avoidance

mechanism operating at high concentrations of As in sub-

strate. The surface layer of both types of tailings at

Chambishi-North is deposited in the aerobic environment

as indicated by the occurrence of hematite, poorly crys-

tallized Fe(III) oxides, and gypsum. In an aerobic envi-

ronment, As occurs in its oxidized form, i.e., arsenate, and

has been reported to be taken by plants by way of phos-

phate-transport systems (Meharg & Hartley-Whitaker

2002; Wang et al. 2002). However, in fronds of P. vittata,

arsenite is the main storage form of As (Lombi et al. 2002;

Wang et al. 2002) and is mainly confined to the vacuoles

(Lombi et al. 2002). Zhao et al. (2002) assumed that

arsenate in P. vittata is likely to be reduced to arsenite in

roots because there was almost no competition between As

and phosphate during transport from roots to fronds. With

the information reported so far, it is expected that arsenate

is taken up by way of phosphate transporters and is then

reduced to arsenites in roots and then transported to fronds

by arsenite transporters. Experiments performed by Duan

et al. (2005) showed that like in other plants, the reaction

rate of arsenate reductase (AsR) in roots of P. vittata

decreased at high concentrations of arsenate ([20 mM) in

substrate. Therefore, it may be speculated that relatively

high arsenate concentrations in reddish-brown tailings

might inhibit the AsR reaction rate and subsequently inhibit

the rate of transport of arsenate by way of arsenate trans-

porter to fronds. The same investigators (Duan et al. 2005)

reported that the activity of AsR showed an optimum pH of

approximately 6.5 and sharply decreases at alkaline pH.

Therefore, the pH of reddish-brown tailings (pH = 8.19)

compared with near-neutral pH of greenish-grey tailings

(pH = 7.23) can decrease the AsR reaction rate. In addition

to internal mechanisms that may decrease translocation of

As from roots to aboveground tissues of plants, the chem-

istry of the substrate may be an important control of As

uptake. Liao et al. (2003), for example, reported that high

contents of Ca2? in the growth media negatively affect As

translocation in P. vittata. Therefore, higher concentrations

of Ccarb in reddish-brown tailings (mean 1.33 wt%), com-

pared with grey-green tailings (mean 0.75 wt%), may be one


123

of the external factors that efficiently decrease the uptake of

As by plants growing in reddish-brown substrate. Previous

experiments have shown (Meharg and Macnair 1990, 1991,

1992; Meharg et al. 1994; Chen et al. 2002b; Meharg and

Hartley-Whitaker 2002; Wang et al. 2002; Huang et al.

2007) that arsenate competes with phosphate for uptake in

plants and that increased external phosphate leads to

decreased As in P. vittata. Our preliminary data indicate that

the concentration of available phosphorus (P) in reddish-

brown tailings (27–36 mg kg-1) is much higher than in

grey-green tailings (1–2 mg kg-1). This corresponds with

much higher content of Corg in reddish-brown tailings

compared with grey-green tailings (Table 1). Therefore, the

higher content of available P in reddish-brown tailings may

inhibit the uptake of As by plants growing in reddish-brown

tailings, whereas lower P content may increase its uptake by

plants growing in grey-green tailings.

Compared with P. vittata, concentrations of As in

C. involucratus leaves are much lower and differ in plants

growing in reddish-brown (21–30 lg g-1 dw) and grey-

green (0.2–0.6 lg g-1 dw) tailings as it is characteristic of

common plants in which uptake and translocation of As

reflect As concentrations in the substrate (Pickering et al.

2000; Meharg and Hartley-Whitaker 2002).

Metals in Plants and Relation to Tailings

Concentrations of Cu and Co in P. vittata and C. invo-

lucratus growing in the Chambishi-North tailings pond are

higher, whereas concentrations of other studied metals are

10000

1000

100

10

1

0.11 10 100 1000

40

35

3025

2015

10

50

0 1000 2000 3000 4000 5000 6000 7000

250

200

150

100

50

00 4000 8000 12000

35

30

25

20

15

10

5

00 10 20 30 40 50 60 70 80

60

50

40

30

20

10

00 500 1000 1500

natattivsiretP , Reddish-brown tailings ( = 7) Pteris vittata n, Grey-green tailings ( = 5)nsutarculovnisurepyC , Reddish-brown ailings ( = 6) Cyperus involucratus, Grey-green tailings (n = 6)

Mn, tailings (µg.g-1)

Zn, tailings (µg.g-1)

As, tailings (µg.g-1) Co, tailings (µg.g-1)

As,

pla

nt (

µg.g

-1 D

W)

Co,

pla

nt (

µg.g

-1 D

W)

Zn,

pla

nt (

µg.g

-1 D

W)

Mn,

pla

nt (

µg.g

-1 D

W)

Cu,

pla

nt (

µg.g

-1 D

W)

Fe,

pla

nt (

µg.g

-1 D

W)

A

800

700

600500

400300

200

100

00 100000 200000 300000

Fe, tailings (µg.g-1)

Cu, tailings (ppm)

B

C D

FE

Fig. 5 Average concentration (mean value) of As (a), Co (b), Cu (c),

Zn (d), Fe (e), and Mn (f) in plant species studied in relation to

average concentrations of the same elements in reddish-brown (full

symbols) and grey-green tailings (open symbols). The bars are SDs.

n = Number of analysed samples of plants and tailings


123

comparable with those in common plants (Table 6). High

concentrations of Cu and Co in plants growing in tailings

ponds were reported by several investigators. For instance,

Brooks and Malaisse (1985) mentioned concentrations of

Cu and Co in several plants from the Copperbelt region

reaching 200 and 73 lg g-1 (dw), respectively. Fonkou

et al. (2002) reported B12,500 lg g-1 Cu in shoots of

C. papyrus growing in wetland contaminated by heavy

metals in Cameroon, and Osman (2001) demonstrated

substantial accumulation of Cu and Co by Typha sp. and

Cyperus sp. within the Copperbelt tailings impoundments.

In contrast, high contents of Mn in leaves of C. involuc-

ratus reported by Cheng et al. (2002) were not confirmed in

our study. However, it is possible that high contents of Cu

and Co in substrate of the Chambishi-North tailings pond

prevent the uptake of Mn or other metals (antagonism in

metals uptake [Brooks 1972; Ross 1994]).

The concentrations of metals accumulated in the

aboveground tissues of P. vittata and C. involucratus

growing on both types of tailings of the old Chambishi-

North tailings pond are similar regardless of different

values of total and plant-available amount of metals in both

types of deposited materials. This is similar to the findings

of MacFarlane et al. (2003), who established that Cu levels

in mangrove leaves were not associated with Cu levels in

the sediment. In case of P. vittata, the mean total con-

centration of Co (Fig. 5b) is similar regardless of its con-

tent in deposited materials. The mean concentrations of Cu

and Zn in fronds are even higher in plants growing on

flotation tailings exhibiting lower concentrations of the

respective metals (Fig. 5c, d), and the mean concentration

of Fe in P. vittata growing on different types of tailings is

similar relative to the great difference in concentration of

Fe in the substrate (Fig. 5e).

As for C. involucratus, the mean concentration of Co is

slightly enhanced in plants growing in reddish-brown

tailings, but the mean content of Zn, Cu, and Fe in this

plant is similar in both types of tailings. As for both plants,

the concentrations of Mn in their aboveground tissues are

similar regardless of very different concentrations of Mn in

tailings (Fig. 5f).

In common (‘‘index’’) plants growing on substrate with

low contents of metals, the concentrations of metals in

aboveground tissues reflect contents of metals in substrate,

but their tolerance to high concentrations of metals is

limited. However, some plants (metallophytes) can grow

under conditions of extremely high concentrations of

metals in the substrate. Metallophytes are incapable of

excluding completely potentially toxic elements, but they

may restrict their uptake and/or translocation within the

plant. The uptake of metals by metallophytes can be

restricted over a wide range of substrate metal concentra-

tion. Plant survival in environments heavily contaminated

with potentially toxic elements can be achieved either by

avoidance mechanisms, whereby a plant is protected from

the influence of metals stress, or by true tolerance mech-

anisms whereby a plant survives the effect of an internal

stress (Baker 1987; Ross and Kaye 1994). The mechanisms

are not mutually exclusive (Macnair 1990; Tomsett and

Thurman 1988), and they can operate in different ways for

different metals. Avoidance can be defined as an organ-

ism’s ability to prevent excessive metal uptake into its

body (Levitt 1980). Such avoidance or metal-exclusion

mechanisms include mycorrhiza formation, alteration of

membrane permeability, proliferation of roots in uncon-

taminated horizons, changes in the metal-binding capacity

of the cell wall, or increased exudation of metal-chelating

substances (for surveys see Verkley and Schat 1990;

Clemens 2001; Raab et al. 2004).

Unlike As, which is stored mostly in fronds of P. vittata,

many investigators (see surveys by Weis and Weis 2004;

Sheoran and Sheoran 2006) have reported that mostly roots

of wetland plants, for example, species of Cyperus, Typha,

and Phragnites, tend to trap metals. Cheng et al. (2002)

Table 6 Concentrations of selected chemical elements (lg g-1 dw) in common plants and in aboveground tissues of P vittata and C. invo-lucratus growing in Cu- and Co-rich tailings of the Chambishi-North impoundment in Zambia

Element Normal rangea Normal rangeb P. vittata Chambishi-

North tailings

C. involucratus Chambishi-

North tailings

As 0.12–0.25 NR 2350.2–6197.4 0.24–30.27

Co 0.25–4.15 0.03–2 18.3–38.6 9.2–14.8

Cu 5.2–14.8 5–25 123.2–237.4 96.3–151.8

Fe 272–470 NR 492–690 215–500

Mn 47.4–337 20–400 26.7–46.2 6.2–56.7

Zn 24–130 20–400 13–33 6–14

NR not reporteda Reported by Reimann and de Caritat (1998), bark data excludedb Reported by Reeves and Baker (2000) and Ma et al. (2001)


123

reported B15,600 lg g-1 Cu, 4850 lg g-1 Mn, and

4579 lg g-1 Zn (dw) in lateral roots of C. involucratus

growing in artificial wetland after application of metals in

solution. Concentrations of Cu, Mn, and Zn in leaves of the

same plant were much lower: 7.1, 68.9, and 77.3 lg g-1

(dw), respectively.

Excess of essential as well as nonessential metals can be

sequestered in root cells by various mechanisms, e.g., (1)

metal sequestration in roots by specially produced organic

compounds, (phytochelatins; Cobbett 2000); (2) subcellulal

compartmenisation, particularly in vacuoles of the root

cell; or (3) organic ligand exudation (Clemens et al. 2002).

Moreover, organic molecules exuded by root cells, as well

as mucilage at root tips, can bind, or chelate, with metals in

the rhizosphere, thus rendering them unavailable or less

available for root uptake (Levitt 1980; Verkley and Schat

1990).

A striking feature of roots of wetland plants is the

presence of metal-rich rhizoconcretions or ‘‘plaques’’ on

the roots (Mendelssohn and Postek 1982; Vale et al. 1990;

Weis and Weis 2004). These structures are composed

mostly of Fe(III) hydroxides and other components, i.e.,

Mn-hydroxides and carbonates, that are precipitated on

the root’s surface. The presence of these accumulations

appeared to decrease the amount of Zn, Mn, Cu, and other

metals in plants (Otte et al. 1989; Batty et al. 2000). At

Chambishi-North, the formation of plaques on the surface

of plant roots (Fig. 6a), as well as the subcelullar com-

partmenisation of inorganic matrix in root cells of P. vittata

(Fig. 6b), was observed using an optical microscope and

electron microprobe studies. Compared with other inves-

tigators who reported the formation of Fe- or Mn-rich

rhizoconcretions on the roots in an acid environment, Al

predominates over Fe on the root surface and in root tissues

at Chambishi-North, which is probably due to the neutral to

alkaline environment of deposited tailings (pH of tailings

leachates 7.12–8.23). The concentration of Fe is close to

the detection limit of the microprobe (0.2 wt% Fe). The

solubility of Fe(III) in the surface layer of tailings under

aerobic, neutral to alkaline conditions is low, whereas Al

may be dissolved as Al(OH)4- and precipitated on the roots

or within the root tissues in the form of amorphous Al

hydroxide or as a crystalline phase (gibbsite). As shown by

Garcia-Sanchez et al. (2002), the absorption capacity of Al

hydroxides for metals and As is comparable with or even

higher than that of Fe(III) oxyhydroxides. Therefore, it can

be assumed that the formation of Al-rich accumulations on

root surfaces or in root cells, and the adsorption of As and

metals on these accumulations, may restrict their uptake

and/or translocation within the plants at the Chambishi-

North tailings pond. If so, then the concentrations of metals

in shoots of plants growing in metalliferous substrates at

Chambishi-North do not reflect the metal contents in the

substrate but rather the efficiency of metal-exclusion

mechanisms in plant roots.

Conclusion

The results of the investigation summarized in this article

show that the Chinese brake fern (P. vittata) is not only a

hyperaccumulator of As, but it has adapted itself to high

concentrations of Cu, Co, and other metals contained in

flotation tailings in mud-settling ponds of the Zambian

Copperbelt. This is an important conclusion because this

plant may possibly be used for phytoremediation. Con-

tamination of soils or ground waters by a single element,

such as As, is actually rare. Pollution by metallurgical and

industrial wastes usually introduces a range of heavy

metals so that any phytoremediation should be based on the

selection and cultivation of plant assemblages that can

accumulate the widest range of pollutants contained in the

B

A

B

Cortex

Cortical cellsCentralcylinder

Al (Fe)deposit

Al (Fe)deposit

Centralcylinder

50 µm

Fig. 6 Deposition of Al-rich and Fe-poor material on root surface

and in root cells of P. vittata growing in the Chambishi-North tailings

pond in Zambia. a Photomicrograph of polished section of degraded

root tissues with accumulation of Al-rich and Fe-poor material (rusty-brown color) on the surface of cortical cells and in the neighborhood

of the central cylinder. b Accumulation of Al-rich and Fe-poor

material (whitish color) close to the central cylinder of P. vittata root.

Back-scattered electron image (Color figure online)


123

substrate. Consequently, it is useful to study plant assem-

blages growing in regions contaminated by high levels of

potentially toxic elements. The tailings ponds of the

Zambian Copperbelt have proven to be the ideal setting for

such a study. Although the results of this study are prom-

ising from the viewpoint of phytoremediation, it will be

necessary to carry out germination experiments and pot

trials to obtain more accurate information about vegetation

growth and the response of different accumulator plants to

As, Co, and Cu mineralization as well as the uptake of

these elements by the root systems and aboveground foli-

age. The natural revegetation of mine wastes contaminated

by combinations of metals and metalloids is crucial for

environmental remediation and human health in populated

areas affected by mining. The value of plant hyperaccu-

mulators in this process is of the utmost importance, and

further investigations should be given high priority.

Acknowledgments This work was supported by the Czech Grant

Agency (Project No. 205/08/0321). The authors are grateful to

F. Veselovsky (Czech Geologic Survey) for participation in the field

operations. The authors are also obliged to J. Macurova (Institute of

Soil Amelioration and Preservation, Czech Republic) for analyses of

available phosphorus in tailings and to J. Malec (Czech Geologic

Survey) for microprobe analyses of root tissues. We are thankful to

David Chuba of the Biological Sciences Department, University of

Zambia for the botanic names of the Zambian plants described in this

paper. The authors are indebted to Ales Soukup (Department of

Experimental Biology, Charles University) for valuable information

about the tolerance and the capacity of plants to accumulate metal-

loids and metals and to Jaroslav Hak and Chriss Halls (the British

Museum of Natural History, London) for English editing. Our thanks

are also directed to Daniel R. Doerge, the journal manager, and to

three anonymous reviewers for their effort to go carefully through the

text and for their reasonable and inspiring recommendations.

References

Baker AJM (1987) Metal tolerance. New Phytol 106(Suppl):93–111

Batty LC, Baker AJM, Wheeler BD, Curtis CD (2000) The effect of

pH and plaque on the uptake of Cu and Mn in Phragmitesaustralis (Cav.). Ann Bot 86:647–653

Boyd RR (2007) The defense hypothesis of elemental hyperaccumu-

lation: status, challenges and new directions. Plant Soil 293:

153–176

Brooks RR (1972) Geobotany and biogeochemistry in mineral

exploration. Harper and Row, New York, NY, p 320

Brooks RR (1998) Plants that hyperaccumulate heavy metals. CABI

Publishing, Wallingford, UK, p 379

Brooks RR, Malaisse F (1985) The heavy metal tolerant flora of

South-Central Africaa multidisciplinary approach. Balkema,

Rotterdam, The Netherlands, p 199

Caille N, Zhao FJ, McGrath SP (2005) Comparison of root

absorption, translocation and tolerance of arsenic in the hypper-

accumulator Pteris vittata and nonhyperaccumulator Pteristremula. New Phytology 165:755–761

Cao XD, Ma LQ, Tu C (2004) Antioxidative responses to arsenic in

the arsenic-hyperaccumulator Chinese brake fern (Pteris vittata).

Environ Pollut 128:317–325

Chen TB, Fan ZL, Lei M, Huang ZC, Wei CY (2002a) Effect of

phosphorus on arsenic accumulation in As-hyperaccumulator

P. vittata L. and its implication. Chin Sci Bull 47:1876–1879

Chen TB, Wei CY, Huang ZC, Huang QF, Lu QG, Fan ZL (2002b)

P. vittata L.: an arsenic hyperaccumulator and its character

accumulating in arsenic. Chin Sci Bull 47:207–210

Cheng S, Grosse W, Karrenbrook F, Thoennessen M (2002)

Efficiency of constructed wetlands in decontamination of water

polluted by heavy metals. Ecol Eng 18:317–325

Clemens S (2001) Molecular mechanisms of plant metal tolerance

and homeostasis. Planta 212:475–486

Clemens S, Palmgren MG, Kramer U (2002) A long way ahead:

understanding and engineering plant metal accumulation. Trends

Plant Sci 7:309–315

Cobbett ChS (2000) Phytochelatins and their roles in heavy metal

detoxification. Plant Physiol 123:825–832

Drever JI (1997) The geochemistry of natural waters. Prentice Hall,

Englewood Cliffs, NJ, p 437

Du WB, Li ZA, Zou B, Peng SL (2005) Pteris multida Poir., a new

arsenic hyperaccumulator: characteristics and potential. Int J

Environ Pollut 23:388–396

Duan G-L, Zhu Y-G, Tong Y-P, Cai Ch, Kneer R (2005) Charac-

terization of arsenate reductase in the extract of roots and fronds

of Chinese Brake Fern, an arsenic hyperaccumulator. Plant

Physiol 138:461–469

Fonkou T, Agendia P, Kengne I, Akoa A, Nya J (2002) The

accumulation of heavy metals in biotic and abiotic components

of the Olezoa wetland complex in YaoundeCameroon (West

Africa). Proceedings of international symposium on environ-

mental pollution control and waste management 7–10 January

2002, Tunis (EPCOWM’2002), pp 29–33

Garcia-Sanchez A, Alvarez-Ayuso E, Rodriguez-Martin F (2002)

Sorption of As(V) by some oxyhydroxides and clay minerals.

Application to its immobilization in two polluted mining soils.

Clay Miner 37:187–194

Gumaelius L, Lahner B, Salt DE, Banks JA (2004) Arsenic

hyperaccumulation in gametophytes of Pteris vittata. A new

model system for analysis of arsenic hyperaccumulation. Plant

Plysiol 136:3198–3208

Huang ZC, An ZZ, Chen TB, Lei M, Xiao WY, Liao XY (2007)

Arsenic uptake and transport of P. vittata L. as influenced by

phosphate inorganic arsenic species under sand culture. J Environ

Sci China 19:714–718

ISO 11466 (1995) Soil quality: extraction of trace elements soluble in

aqua regia. International Organization for Standardization (ISO),

Geneva, Switzerland

ISO/DIS 14870 (2001) Determination of extractable metals with

solution of diethylentriaminepentaacetic acid (DTPA) and

trethanolamine (TEA). International Organization for Standardi-

zation (ISO), Geneva, Switzerland

Kamona AF, Nyambe IA (2002) Geological characteristics and

genesis of stratiform sediment-hosted Cu-(Co) deposits, Zam-

bian Copperbelt. In: Miller RE (ed) Proceedings of the 11th

IAGOD quadrennial symposium and geocongress, extended

abstracts. Geological Survey of Namibia, Windhoek Namibia

(CD version)

Koller CE, Patrick JW, Rose RJ, Offler CE, MacFarlande GR (2007)

Pteris umbrosa R.Br. as an arsenic hyperaccumulator: accumu-

lation, partitioning and comparison with the established hyper-

accumulator Pteris vittata. Chemosphere 66:1256–1263

Krıbek B, Majer V, Veselovsky F, Nyambe I (2010) Discrimination

of lithogenic and anthropogenic sources of metals and sulphur in

soil of the central-northern part of the Zambian Copper Mining

District: a topsoil vs. subsurface soil concept. J Geochem Explor

104:69–86


123

Levitt J (1980) Responses of plants to environmental stress, 2nd edn.

Academic, New York, NY, p 354

Liao XY, Xiao XY, Chen TB (2003) Effects of Ca and As addition of

As, P and Ca uptake by hyperaccumulator P. vittata L. under

sand culture. Acta Ecol Sin 23:2057–2065

Limpitlaw D (2002) An assessment of mining impacts on the

environment in the Zambian Copperbelt. PhD Thesis, University

of the Witwatersrand, Johannesburg, South Africa

Lombi E, Zhao FJ, Fuhrmann M, Ma LQ, McGRath SP (2002)

Arsenic distribution and speciation in the fronds of the hypeac-

cumulator Pteris vittata. New Phytol 156:195–203

Ma LQ, Komar KM, Tu C, Zhang W, Cai Y, Kennelley ED (2001) A

fern that hyperaccumulates arsenic: a hardy, versatile, fast-

growing plant helps to remove arsenic from contaminated soils.

Nature 409:579

MacFarlane GR, Pulkownik A, Burchett MD (2003) Accumulation

and distribution of heavy metals in the gray mangrove,

Avicennia marina (Forsk.) Vierth.: geological indication poten-

tial. Environ Pollut 123:139–151

Macnair MR (1990) The genetics of metal tolerance in natural

populations. In: Shaw AJ (ed) Heavy metal tolerance in plants:

evolutionary aspects. CRC Press, Boca Raton, FL, pp 235–255

Matschullat J (2000) Arsenic in the geosphere: a review. Sci Total

Environ 249:297–312

McGrath SP, Zhao FJ (2003) Phytoextraction of metals and metal-

loids from contaminated soils. Curr Opin Biotechnol 14:277–282

McKenzie RM (1980) The adsorption of lead and other heavy metals

on oxides of manganese and iron. Aust J Soil Res 18:61–73

Meharg AA, Hartley-Whitaker J (2002) Tansley review no. 133:

arsenic uptake and metabolism in arsenic resistant and nonre-

sistant plant species. New Phytol 154:29–43

Meharg AA, Macnair MR (1990) An altered phosphate-uptake system

in arsenate-tolerant Holcus lanatus L. New Phytol 116:29–35

Meharg AA, Macnair MR (1991) Uptake, accumulation and trans-

location of arsenate in arsenate-tolerant and nontolerant Holcuslanatus L. New Phytol 117:225–231

Meharg AA, Macnair MR (1992) Suppresion of the high-affinity

phosphate-uptake system: a mechanism of arsenate tolerance in

Holcus lanatus L. J Exp Bot 43:519–524

Meharg AA, Bailey J, Breadmore K, Nacnair MR (1994) Biomass

allocation, phosphorus nutrition and vesicular-arbuscular mycor-

rhizal infection in clones of Yorkshire fog Holcus lanatus L.

(Poaceae) that differ in their phosphate uptake kinetics and

tolerance to arsenate. Plant Soil 160:11–20

Mendelsohn F (1961) The geology of the Northern Rhodesian

Copperbelt. Macdonald & Co. Ltd, London, UK, p 876

Mendelssohn IA, Postek MT (1982) Elemental analysis of deposits on

the roots of Spartina alterniflora Loisel. Am J Bot 69:904–912

Osman A (2001) The uptake of contaminants in mine effluent by

plants (Typha sp. and Cyperus sp.) at the New Dam dambo,

Zambia. Masters thesis, Oxford University, Oxford, UK

Otte ML, Rozema J, Koster L, Haarsma M, Broekman R (1989) Iron

plaque on roots of Aster tripolium L.: interaction with zinc

uptake. New Phytol 111:309–317

Otte ML, Kearns CC, Doyle MO (1995) Accumulation of arsenic and

zinc in the rhizosphere of wetland plants. Bull Environ Contam

Toxicol 55:154–161

Pickering IJ, Prince RC, George MJ, Smith RD, George GN, Salt DE

(2000) Reduction and coordination of arsenic in Indian mustard.

Plant Physiol 122:1171–1177

Raab A, Feldmann J, Meharg AA (2004) The nature of arsenic

phytochelatin complexes in Holcus lanatus and Pteris cretica.

Plant Physiol 134:1113–1122

Rauret G, Lopez-Sanchez JF, Sahuquillo A, Rubio R, Davidson C,

Ure A et al (1999) Improvement of the BCR three step sequential

extraction procedure prior to the certification of new sediment

and soil reference materials. J Environ Monit 1:57–61

Reimann C, de Caritat P (1998) Chemical elements in the environ-

ment. Factsheets for geochemists and environmental scientists.

Springer, Berlin, Germany, p 460

Ross SM (1994) Retention, transformation and mobility of toxic

metals in soils. In: Ross SM (ed) Toxic metals in soil-plant

systems. Wiley, Chichester, UK, pp 63–152

Ross SM, Kaye KJ (1994) The meaning of metal toxicity in soil-plant

system. In: Ross SM (ed) Toxic metals in soil-plant systems.

Wiley, Chichester, UK, pp 27–62

Salt DE, Blaylock M, Kumar NP, Dushenkov V, Ensley BD, Chet I

et al (1995) Phytoremediation: a novel strategy for the removal

of toxic metals from the environment using plants. Biotechnol-

ogy 13:468–474

Sheoran AS, Sheoran V (2006) Heavy metal removal mechanism of

acid mine drainage in wetlands: a critical review. Miner Eng

19:105–116

Sracek O, Mihaljevic M, Krıbek B, Majer V, Veselovsky F (2010)

Geochemistry and mineralogy of Cu and Co in mine tailings at

the Copperbelt, Zambia. J Afr Earth Sci 57:14–30

Srivastava M, Ma LQ, Santos JAG (2006) Three new arsenic

hyperaccumulating ferns. Sci Total Environ 364:24–31

Tomsett AB, Thurman DA (1988) Molecular biology and metal

tolerance in plants. Plant Cell Environ 11:383–394

Tripathi RD, Srivastava S, Mishra S, Singh N, Tuli R, Gupta DK et al

(2007) Arsenic hazards: strategies for tolerance and remediation

of plants. Trends Biotechnol 25:158–165

Tu C, Ma LQ (2003) Effects of arsenate and phosphorus on their

accumulation by ab arsenic-hyperaccumulator Pteris vittata L.

Plant Soil 49:373–382

Tu C, Ma LQ, Bondada B (2002) Arsenic accumulation in the

hyperaccumulator Chinese brake and its utilization potential for

phytoremediation. J Environ Qual 31:1671–1675

United States Geological Survey (2010) Minerals information, copper

and cobalt. Available at: http://minerals.usgs.gov/minerals/

pubs/commodity. Accessed 23 July 2010

Vale C, Catarino F, Cortesao C, Cacador M (1990) Presence of metal-

rich rhizoconcretions on the roots of Spartina maritima from the

salt marshes of the Tagus estuary, Portugal. Sci Total Environ

97(98):617–626

Verkley JAC, Schat H (1990) Mechanisms of metal tolerance in

higher plants. In: Shaw AJ (ed) Heavy metal tolerance in plants:

evolutionary aspects. CRC Press, Boca Raton, FL, pp 179–193

Wang JR, Zhao FJ, Meharg AA, Raab A, Feldmann J, McGrath SP

(2002) Mechanisms of arsenic hyperaccumulation in P. vittata:

uptake kinetics, interactions with phosphate, and arsenic speci-

ation. Plant Physiol 64:1552–1661

Wang HB, Ye ZH, Shu S, Li WC, Wong MH, Lan CY et al (2007)

Uptake and accumulation of arsenic by 11 Pteris taxa from

southern China. Environ Pollut 145:225–233

Weis JS, Weis P (2004) Metal uptake, transport and release by

wetland plants: implication for phytoremediation and restoration.

Environ Int 30:685–700

Wenzel WW, Adriano DC, Salt D, Smith R (1999) Phytoremediation:

a plant-microbe-based remediation system. In: Adriano DC,

Bollag JM, Frankenberger WT Jr, Sims RC (eds) Bioremediation

of contaminated soils. Agronomy Monograph 37. Soil Science

Society of America, Madison, WI, pp 456–508

Xie QE, Yan XL, Liao XY, Li X (2009) The arsenic hyperaccumu-

lator fern Pteris vittata L. Environ Sci Technol 43:8488–8495

Zhao FJ, Dunham SJ, McGrath SP (2002) Arsenic hyperaccumulation

by different fern species. New Phytol 56:27–31

Zhao FJ, Ma JF, Meharg AA, McGrath SP (2009) Arsenic uptake and

metabolism in plants. New Phytol 181:777–794


123

http://minerals.usgs.gov/minerals/pubs/commodity

http://minerals.usgs.gov/minerals/pubs/commodity

the extent of arsenic and of metal uptake by aboveground ... · the extent of arsenic and of metal...

Documents