0012-4966/03/1112- © 2003 MAIK “Nauka /Interperiodica”0550

Doklady Biological Sciences, Vol. 393, 2003, pp. 550–552. Translated from Doklady Akademii Nauk, Vol. 393, No. 4, 2003, pp. 567–569.Original Russian Text Copyright © 2003 by Kolotov, Demidov, Volkov.

It has recently been reported that global urbaniza-tion had a significant negative impact on the photosyn-thetic potential of the earth surface [6]. It was noted inthis report that the period of photosynthetic activity inurban regions may be reduced by as much as 20 days.Emergence of vast urban areas of enhanced local tem-perature causes an increase in the duration of the agri-cultural season without increasing land productivity,which, in turn, can be explained by an earlier onset anda longer duration of the fall of the leaves and by a lowerpeak productivity of the season. It is obvious that theconclusions drawn in this report are fully valid in thecase of vast areas of industrial zones. On the globalscale, such an extraordinary effect of technogenicexpansion may cause dramatic consequences, particu-larly, in the Northern Hemisphere, where this expan-sion is most intense.

Mining, smelting, metal-working, and some otherindustries, as well as intense urbanization, cause envi-ronmental pollution with heavy metals and, eventually,environment degradation [4].

The mechanisms of this degradation and its fundamen-tal signs require special research. In addition, detection ofthe sites of environment degradation within areas ofanthropogenic impact is an urgent problem, because it isconnected with the problem of effective practical use ofnatural resources and evaluation of land cost.

The soil–vegetation system plays a key role in thesestudies, because it solves the main living problems of thehuman population and provides a basis for trophic chains.For ecological research, the soil–vegetation system is alsothe most informative one, because it lies in the interfacebetween four global regions: the lithosphere, hydrosphere,atmosphere, and biosphere.

Heavy metals accumulate in the uppermost soillayer saturated with humus (horizon

Ä

1

). The gross

concentrations of elements in this horizon contain cer-tain fractions of rigidly fixed and mobile (metastable)forms of chemical elements. Mobile forms are eitherdissolved in the soil solution or loosely bound to thewalls of pores. Under certain conditions (e.g., atmo-spheric precipitation, particularly, acid rain), theloosely bound forms of chemical elements are releasedinto the soil solution and taken up by vegetation.Mobile forms may have negative or positive effects onenvironment, primarily, on the vegetation cover. Theconcentrations of the mobile forms of each chemicalelement are correlated with its gross concentration inthe vegetation and soil (Fig. 1).

GENERAL BIOLOGY

Chlorophyll Content as a Primary Indicator of the Environment Degradation Due to Contamination with Heavy Metals

B. A. Kolotov*, V. V. Demidov**, and S. N. Volkov*

Presented by Academician N.P. Laverov August 11, 2003

Received August 11, 2003

*Institute of Mineralogy, Geochemistry, and Crystal Chemistry of Rare Elements, Ministry of Natural Resources of Russian Federation and Russian Academy of Sciences, ul. Veresaeva 15, Moscow, 121357 Russia**Boston University, Boston, MA 02215 United States

1000

100

10

1

0.1

1 2 3 4 5 6 7 8

0.50.40.30.20.10

Chl

orop

hyll,

% o

f dr

y pl

ant w

eigh

t

Pb, mg/kg

Fig. 1.

Gross concentrations and distribution of mobileforms of lead in soil and the profile of chlorophyll concen-tration in the vegetation cover of the Salair mine and thetown of Salair. (

1– 4

) Concentrations of lead and chloro-phyll: (

1

) concentrations of mobile forms of lead in soils;(

2

) concentrations of mobile forms of lead in the vegetation;(

3

) gross concentrations of lead in soils; (

4

) concentration ofchlorophyll. (

5–7

) Functional zones: (

5

) forest and farm-land zone; (

6

) residential zone; (

7

) ore-containing rock;(

8

) ore-bearing layer.

DOKLADY BIOLOGICAL SCIENCES

Vol. 393

2003

CHLOROPHYLL CONTENT AS A PRIMARY INDICATOR OF THE ENVIRONMENT 551

Chlorophyll is the most important component of theearth’s vegetation cover because specifically this sub-stance determines the vital conditions of all ecologicalniches in the entire geosystem of a given area and itscontent in plants is known to be significantly depressedby deterioration of environment (chlorosis). The profileof the distribution of the gross concentration andmobile forms of Pb in the upper soil layer and vegeta-tion cover is shown in Fig. 1 together with the chloro-phyll content profile in the functional zone of the mine-town of Salair. As seen from Fig. 1, a clear correlationis observed between the concentrations of differentforms of lead and the opposite response in the chloro-phyll content. Our studies demonstrated that pollutionof experimental plots of land with heavy metals in theareas of different ore deposits [3, 4], industrial zones,and urban agglomerations was always accompanied byacute chlorosis in the local vegetation cover (Figs. 1–3).

The gross concentrations of metals in soil were mea-sured by spectral analysis method. The concentrationsof the mobile metal forms in the vegetation were deter-mined in the hydrochloric acid extracts (pH 4) from thefresh plant substrate using atomic absorption spectrom-etry. The chlorophyll concentration in the ethanol

2

10

3 5 7 9 11 13 15 17 19 21 23 25 31 29 27

468

101214161820 0.40

0.350.300.250.200.150.100.050

Chlorophyll, %Concentration of Mo, g/t

Mo, grass CHL, grass

Sado

voe

The

for

kof

Var

shav

skoe

and

Kas

hirs

koe

shos

se

Sum

skoi

MR

R

Fig. 2.

The profile of the concentrations of, molybdenum,and chlorophyll in the vegetation cover of Moscow, fromthe Moscow Ring Road (MRR, which encircles the entirecity) to Sadovoe Kol’tso (a ring road circling the central part ofthe city). Designations: CHL, chlorophyll; Mo, molybdenum.

Fig. 3.

Development of chlorophyll deficiency in the polluted area of intense, long-term mining (mine Salair): (

1

) the borders of theore field; (

2

) ore-enrichment factories; (

3

) the border of the town of Salair; (

4

) complex contrast geochemical anomaly of elements(Ag, Pb, Mo, Ba, V, Co, Cr, Cu, Zn, Sr, B, and Ni) in the soil cover; (

5

) complex weak geochemical anomaly of elements (Ag, Pb,Mo, Ba, V, Co, Cr, Cu, Zn, Sr, B, and Ni) in the soil cover; (

6

) the zone of a reduced concentration of chlorophyll.

Kol

’tso

shos

se

proe

zd

0 500

1 2 3 4 5 6

552

DOKLADY BIOLOGICAL SCIENCES

Vol. 393

2003

KOLOTOV

et al

.

extracts of crushed plants preliminarily dried in thedark was photometrically measured at 660.

The transpiration solutions taken up by the vegeta-tion from the soil contain nutritional chemical ele-ments, excessive amounts of which are dischargedthrough leaves to the atmosphere [1–3]. This dischargeoccurs through the fine hollow hairs, and the chemicalcomposition of the discharged transpiration solutiondirectly reflects specific features of the underlying soilcover, including the composition of soil moisture(Fig. 1) [1, 5]. The growth rate of the hollow hairs inplants exposed to toxic elements (e.g., Cd) decreases,whereas the number of the hairs in such plants increasesalmost twofold to provide forced discharge of the toxiccomponent [5]. In this case, crystals of Cd-containingphytochelatin emerge from the hollow hair heads at theleaf surface. This was experimentally demonstrated byY.-E. Choi

et al.

[5] and is shown in Fig. 4. Based on theresults described above, we may therefore concludethat heavy metals exert a deleterious effect on plants.

Thus, rather evident symptoms of the environmentdegradation could be observed in the case of environ-ment pollution with toxicants. Still, because most pol-

lutants decrease the chlorophyll content, the signs ofserious deprivation of environment are most evidentwhen simultaneously monitoring both the environmen-tal pollution with heavy metals and the deterioration ofchlorophyll in local plants (i.e., decrease in chlorophyllcontent in the vegetation cover).

Statistic analysis of the data obtained in urban areas(Moscow) demonstrated a statistically significant nega-tive correlation between the concentrations of Cu, Sn,Ag, Co, Mo, W, Sr, and Sc in the vegetation cover andthe concentration of chlorophyll (Fig. 2). In the case ofsevere environmental pollution with heavy metals, e.g.,at the sites of ore (especially sulfide) mining, the scaleof chlorosis is extensive, and large vegetation areas aredamaged and turning into chlorophyll-deficient “holes”(Fig. 3).

This study is of considerable practical importance,because it allows the areas with different degrees ofenvironment degradation to be readily mapped usingthe chlorophyll content as a primary indicator.

ACKNOWLEDGMENTS

We are grateful to L.I. Kashina, D.E. Kalugin, andL.I. Minacheva for their assistance in field experimentsand analytical studies.

REFERENCES

1. Demidov, V.V., in

Biogeokhimicheskie metody priizuchenii okruzhayushchei sredy

(Biogeochemical Meth-ods in Environmental Studies), Moscow: IMGRE, 1989,pp. 130–134.

2. Kolotov, B.A., Kiseleva, E.A., and Rubeikin, V.Z.,

Geokhimiya

, 1966, vol. 7, pp. 878–880.3. Kolotov, B.A., Rubeikin, V.Z., and Kiseleva, E.A.,

Raz-ved. Okhr. Nedr

, 1995, vol. 6, pp. 192–195.4. Kolotov, B.A., Solomin, G.A., Rubeikin, V.Z.,

et al.

, in

Prikladnaya geokhimiya

(Applied Geochemistry), Mos-cow: IMGRE, issue 2, pp. 70–98.

5. Choi, Y.-E., Harada, E., Wada, M.,

et al., Planta

, 2001,vol. 213, no. 1, pp. 45–50.

6. Yee, A.,

Goddard Space Flight Centre: Release no: 00-23

, Greenbelt, 2000.

Fig. 4.

Formation of a Cd–Ca phytochelatin crystal (arrow)on the hollow-hair head at the leaf surface of tobacco plant(

Nicotiana tabacum

L.) in the case of treatment of seedlingswith cadmium salts (data from [5]).