heavy metal contamination in arable soils and vegetables around a sulfuric acid factory, china

Juan Liu*1,2

Jin Wang*1

Jianying Qi3

Xiangping Li1

Yongheng Chen1

Chunlin Wang4

Yingjuan Wu1

1Department of Environmental Science

and Engineering, Guangzhou

University, Guangzhou, China2Department of Earth Sciences,

National Taiwan University, Taipei,

China3South China Institute of

Environmental Science, Ministry of

Environmental Protection (SCIES-

MEP), Guangzhou, China4Research Center for Environmental

Science, Guangdong Provincial

Academy of Environmental Science,

Guangzhou, China

Research Article

Heavy Metal Contamination in Arable Soils andVegetables around a Sulfuric Acid Factory, China

This study was designed to investigate heavy metal (Tl, Pb, Cu, Zn, and Ni) contami-

nation levels of arable soils and vegetables grown in the vicinity of a sulfuric acid

factory in the Western Guangdong Province, China. Health risks associated with these

metals by consumption of vegetables were assessed based on the hazard quotient (HQ).

The soils show a most significant contamination of Tl, followed by Pb, Cu, Zn, and Ni.

The heavy metal contents (mg/g, dry weight basis) in the edible parts of vegetables range

from 5.60 to 105 for Tl, below detection limit to 227 for Pb, 5.0–30.0 for Cu, 10.0–82.9

for Zn, and 0.50–26.0 for Ni, mostly exceeding the proposed maximum permissible

level in Germany or China. For the studied vegetables, the subterranean part generally

bears higher contents of Tl and Zn than the aerial part, while the former has lower

contents of Cu and Ni than the latter. In addition, the results reveal that Tl is the major

risk contributor for the local people since its HQ values are mostly much higher than

1.0. The potential health risk of Tl pollution in the food chain and the issue of

food safety should be highly concerned and kept under continued surveillance and

control.

Keywords: Food; Hazard quotient; Health risk; Soil

Received: October 11, 2011; revised: November 22, 2011; accepted: December 5, 2011

DOI: 10.1002/clen.201100550

1 Introduction

The growing problem of heavy metal contamination has significant

negative effects on environmental quality and human livelihoods all

over the world [1–3]. During the recent decades, rapid urbanization

and industrialization releases large quantities of heavy metals into

the agro-environment, which substantially changes the soil quality

of arable soils. The accumulation of heavy metals in soils, either

essential micronutrient like Cu and Zn or toxic elements (e.g., Pb, Tl),

might exceed a toxic content level, thereby leading to ecological

damages through food chain [3, 4].

As a result of the persistent and non-biodegradable properties,

heavy metals could be accumulated in the vital organs of the human

body, causing numerous serious health disorders, such as decreased

immunological defenses, intrauterine growth retardation, impaired

psycho-social faculties, and disabilities associated with malnutrition

[5]. Previous investigations by Xiao et al. [6, 7] illustrated that in the

Lanmuchang area, Southwest China—a specific geo-environmental

context with Tl pollution, the continuous consumption of Tl-

containing vegetables grown in local Tl-contaminated soils resulted

in a chronic Tl poisoning (e.g., disturbance of vision, hair loss) of the

local villagers. The high prevalence of upper gastrointestinal cancer

rates in a region of the Eastern Turkey was found to be related to the

high metal (Co, Cd, Pb, Mn, Ni, and Cu) concentrations in fruits and

vegetables [8].

To date, an enormous number of sites in China have been con-

taminated by heavy metals, due to inadequate sewage treatment,

inadvertent spills, and some other related industrial activities [1, 3].

Inherent to this, reports on the incidental poisoning have soared

throughout China, mostly via intake of vegetables planted on the

heavy metal polluted soil [1, 7]. In the industrial site of the Yunfu

Sulfuric Acid Factory, which is located in the Western of Guangdong

Province, China, pertinent studies have shown that the open-air-

disposed slag material, surface water, sediment, and soil were

severely contaminated by heavy metals (such as Tl, Pb, and Cu)

[9–15]. Since its establishment in 1985, the factory has been dispos-

ing 10–15 thousand tons of pyrite slag in an open air annually [9].

Elevated contents of Tl (46.7 mg/g), Pb (1380 mg/g), and Cd (8.77 mg/g)

were found in the pyrite slag stockpile [10]. Relatively high pro-

portions (15–30%) of these metals were associated with the bio-

available fraction of the slag material [10]. Therefore, the possibilities

of heavy metal contamination of the arable soils and the vegetables

planted near the industrial area could not be ruled out. Worse still,

the discharged wastewater and solid wastes were irrationally and

randomly provided for irrigation and fertilization by the local

farmers. As observed in our field trip, various vegetables have been

successfully planted and consumed by the local inhabitants.

However, as to our knowledge, limited information is available

on the heavy metal contamination of the arable soils and vegetables

and the related health risks.

*Jin Wang and Juan Liu contributed equally to this work.

Correspondence: Professor Y. Chen, Department of EnvironmentalScience and Engineering, Guangzhou University, Waihuan Xi Road230, Panyu District, 510006 Guangzhou, ChinaE-mail: [email protected]

Abbreviations: ADD, average daily intake dose; BW, body weight; ED, theexposure duration; EF, the exposure frequency; EPA, EnvironmentalProtection Agency; HQ, hazard quotient; ICP-MS, inductively coupledplasma mass spectrometer (ICP-MS); IR, intake rate; MPL, maximumpermissible level; MRI, Midwest Research Institute; RfD, oral referencedose; SCIES-MEP, South China Institute of Environmental Science,Ministry of Environmental Protection; TF, transfer factor

Clean – Soil, Air, Water 2012, 00 (0), 1–7 1

� 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com

The aims of this study are: (1) to quantify the content of heavy

metals (Tl, Pb, Cu, Zn, and Ni) in the agricultural soil and vegetables

around the Yunfu Sulfuric Acid Factory, China; (2) to assess potential

health risk to local populations produced by the metals via oral

exposure routes.

2 Materials and methods

2.1 Location and sampling

Samplings were carried out in March 2009 around the industrial site

of the Yunfu Sulfuric Acid Factory, located in the Western of

Guangdong Province, China (238030N and 1128010E). The factory

was established by the local government in 1985 as a state owned

enterprise, and plays a vital part in the local economy. The climate is

subtropical monsoon with a mean annual temperature of 228C and

precipitation around 1700 mm/year [11]. The annual average pH

value of rainwater, as reported, is around 4.0 [12].

Six kinds of vegetable samples cultivated in different croplands

around the factory were selected for this study, at the time of

sampling performed. The details of the vegetables are specified in

Tab. 1. They represented the major vegetable species growing in the

vicinity of the factory. The croplands are distributed within 0.2–

0.3 km distance from the factory, and the detailed location is given in

Fig. 1. At each sampling site of the vegetables, their corresponding

rhizosphere soil was collected manually, with a stainless steel shovel

to a depth of 10 cm. Accordingly, six soil samples were gained

in total. All samples were put in plastic bags immediately after

sampling and stored at �48C.

2.2 Sample preparation and analytical methods

Before laboratory analysis, plant samples were cleaned with distilled

water, separated into root, stem and leaf, and oven-dried at 608C to

constant weight. After this, the samples were cut into slices, ground,

and sieved at a size <80 mm, and sealed in polyethylene bottle for

later analysis. Soil samples were air-dried (at 228C) and sieved

(<80 mm in diameter).

The measurement of metal contents was accomplished at the

South China Institute of Environmental Science, Ministry of

Environmental Protection (SCIES-MEP), Guangzhou, China. Prior

to measurement, 200 mg of each plant or soil sample were digested

with 4 mL of 68% HNO3 v/v, 1 mL of 40% hydrofluoric acid (HF) v/v, and

1 mL of 30% H2O2 v/v, at 1908C for 15 min in a WX-4000 closed-vessel

microwave digestion system (630� 50 W full power) (Shanghai EU

Chemical Instrument Co. Ltd, China). After the obtained solute was

cooled to the room temperature, 4 mL of saturated boric acid was

added into the solute. Subsequently, the solute was digested in the

same microwave system at 1908C for another 15 min, in order to

remove the excessive HF. The solution derived was then diluted into

100 mL for subsequent measurement of metals.

Heavy metal (Tl, Pb, Cu, Zn, and Ni) determination was performed

on an Elan 6100 DRCII Inductively Coupled Plasma Mass

Spectrometer (ICP-MS, PerkinElmer Sciex, USA). The detailed

analytical conditions can be found in reference [11, 13]. The standard

solutions were prepared from ICP Multi-Element Standard Solutions

(SPEX Industries Inc., NJ, USA). In and Sc were used as internal

standards to compensate for changes in analytical signals that

may occur during the operation. Blank reagents were digested in

the same way as the samples. The detection limits of the analytical

method were evaluated by normalizing the result of seven repeated

analyses of experimental blank to a sample mass of 200 mg. The

average detection limits (3 s) of Tl, Pb, Cu, and Ni were 0.005 mg/g

and of Zn 0.015 mg/g. A Certified Reference Material (GBW07406)

obtained from the National Center for Standard Reference

Materials of China was digested along with the samples to assure

the precision and accuracy of analysis. The coefficients of variation of

triplicate analysis for the studied elements were below 10%, and the

accuracy was found to be within �5%.

Ultra-pure water (18.25 MV cm) from a MilliQ-system (Millipore,

Milford Corp., USA) was used for all the experiments. All glassware

and Teflon vessels were soaked in a 0.2 mol/L HNO3 solution for 24 h

and then rinsed with ultra-pure water. Nitric acid (HNO3), HF, and

hydrogen peroxide (H2O2) were of super-pure grade.

2.3 Calculation of transfer factor (TF)

In order to evaluate the transfer potential of a metal from soil to

plant, an index specified as transfer factor (TF) was applied in this

study. The TF refers to the ratio of the metal content in plant to that

in soil [16]. The TFs of Tl, Pb, Cu, Zn, and Ni were calculated by the

equation below:

TF ¼ cplant

csoil

where cplant and csoil refer to the content of metal in plant and that in

soil, respectively.

2.4 Risk assessment

In this study, health risk assessment of Tl, Pb, Cu, Zn, and Ni was

performed in the two stages: (1) exposure assessment; (2) risk assess-

ment. During the 1st stage, an average daily intake dose (ADD,

mg/(kg/d)) was applied to quantify the oral exposure dose of hazard-

ous substances. The ADD was calculated as follows [17]:

ADD ¼ ci � IR � ED� EF

BW � TA

where ci is the metal content in plant (mg/g, fresh weight); IR is the

intake rate (g/day, fresh weight); ED is the exposure duration (a); EF is

Table 1. General description of vegetable samples around the Yunfu Sulfuric Acid Factory

Local name Botanical name Species Family

Soy bean Glycine max G. max FabaceaeTaro Colocasia esculenta C. esculenta AraceaeSweet potato Ipomoea batatas I. batatas ConvolvulaceaeChinese lettuce Lactuca sativa var. longifolia Lam. L. sativa AsteraceaeRomaine lettuce Lactuca sativa L. sativa AsteraceaeAubergine Solanum melongena L. S. melongena Solanaceae

2 J. Liu et al. Clean – Soil, Air, Water 2012, 00 (0), 1–7


the exposure frequency (day/a); BW is the body weight (kg); and TA is

the average exposure time (day).

Based on preceding statistical estimated value [18, 19], a factor of

0.8 and 0.085 was used to convert the fresh to dry weight of the

soybean and the other leafy vegetables, respectively. The IR of the

studied vegetables was cited from a previous survey of consumption

habits of the suburb residents in the Guangdong Province [20].

According to the previous reports [21, 22], ED was assumed to be

30 a, and EF be 350 d/a. The BW used in this calculation was that of

the average Chinese adult (62.7 kg) [21], and the average exposure

time used was 70 a� 365 d/a.

In the 2nd stage, the hazard quotient (HQ) was used to assess the

health risk of non-carcinogenic adverse effect to the local residents,

arising from the exposure of toxicants through intake of vegetables.

In accordance with the standard US Environmental Protection

Agency (EPA) methods [22], the HQ is defined as the ratio of the

ADD and the oral reference dose (RfD, mg/(kg/day)), which could be

calculated as follows:

HQ ¼ ADD

Rf D

The US EPA has established the oral reference dose (RfD) for Pb, Cu,

Zn, and Ni in food at 3.5, 40, 300, and 20 mg/(kg/day), respectively [23].

Due to no RfD of Tl available at present, 0.08 mg/kg/day of provision

tolerable daily intake recommended by the US Midwest Research

Institute (MRI) [24] was used to elaborate Tl health hazard.

Guidelines for interpreting HQ calculations are listed in the

following [25]:

HQ< 0.1, no hazard exists;

HQ¼ 0.1–1.0, hazard is low;

HQ¼ 1.1–10, hazard is moderate;

HQ> 10, hazard is high.

3 Results and discussion

3.1 Heavy metal content in the arable soils

The contents of Tl, Pb, Cu, Zn, and Ni in the arable soils are listed in

Tab. 2. The Tl contents amount to 3.76–7.24 mg/g with the mean value

of 5.36 mg/g. The average Tl content in the background soil of China

and the Guangdong Province was found to be 0.58 and 0.52 mg/g,

respectively [26]. To date, no Tl limit has been established for the

agricultural soil in China, and the maximum admissible level of

1 mg/kg recommended by the Canadian guideline and Swiss

ordinance was used as the ‘‘critical trigger content’’ in the soil

[27]. Obviously, all the studied arable soils bear significantly elevated

level of Tl, exceeding the natural background level as well as the

critical trigger content.

The Pb contents in the soils vary from 43.2 to 94.2 mg/g with the

mean value of 65.9 mg/g (Tab. 2). According to previous survey [28],

the Pb contents of the normal Chinese soils are in the range of

9.95–56.0 mg/g, with the mean value of 26 mg/g, and that of the

background soil from the Guangdong Province is 36 mg/g [29]. By

considering the general range of the Pb content in the studied soils,

it appears that the soils are moderately contaminated by Pb.

However, the levels of Pb are still far below the maximum tolerable

Chinese agricultural content for soil (250 mg/g) [30].

The Cu contents in the arable soils range from 39.4 to 70.2 mg/g

with the mean value of 55.0 mg/g. In comparison to the mean content

of Cu in the background soil of China (17 mg/g) [28] and the

Guangdong Province (22.6 mg/g) [29], the arable soils around the

sulfuric acid factory are assumed to be contaminated by Cu to a

Figure 1. The location of the sampling sitearound the Yunfu Sulfuric Acid Factory inGuangdong Province, China.

Clean – Soil, Air, Water 2012, 00 (0), 1–7 Heavy Metal Contamination in Arable Soils 3


moderate degree. Still, Cu contents are mostly below or within the

limits of the corresponding maximum allowable content for soil in

China (50 mg/g) [30].

The amounts of Zn in the soils are in the range 47.2–88.5 mg/g with

the mean value of 71.5 mg/g (Tab. 2). Clearly, the Zn levels are

generally below or within the range of the Zn contents in the

background soil of China (47.3 mg/g) [28] and the Guangdong

Province (74.2 mg/g) [29]. Again, the Zn contents in the studies soils

are obviously below the threshold value of Zn (200 mg/g) in the

Chinese agricultural soil [30]. Therewith, the studied soils are not

contaminated by Zn. Similarly, no obvious Ni contamination is

observed.

Several possible reasons could be attributed to the high

enrichment of Tl in the studied soils: (1) the irrigation of the

arable soils by the Tl-containing wastewater discharged from the

sulfuric acid plant; (2) the fertilization of the soils by stockpiling

of the Tl-rich pyrite slag materials; and (3) the atmospheric

deposition of Tl-bearing aerosols on the soils. Our previous

investigation showed that Tl concentration in the wastewater of

the Yunfu Sulfuric Acid Factory amounted to 15.4–400 mg/L,

since the conventional treatment method through precipitation

by limes, applied in the factory, is not capable of removing Tl from

the wastewater [14]. According to [15], the aerosols from the factory

were found to contain high contents of Tl (18.6–33.1 mg/g).

3.2 Heavy metal content in the edible parts of

vegetables

As listed in Tab. 3, heavy metal contents (mg/g, dry weight basis) in

the edible parts of vegetables range from 5.60 to 105 for Tl, below

detection limit to 227 for Pb, 5.0–30.0 for Cu, 10.0–82.9 for Zn, and

0.50–26.0 for Ni. According to the maximum permissible levels

(MPLs) of contaminants in foods of China (GB2762-2005) [31], the

average Pb, Cu, Zn, and Ni levels in the edible parts are 151, 1.64,

1.35, and 6.82 times higher than the permissible values, respectively.

Since no guideline of Tl in foods is available in China, the MPL

(0.5 mg/g) in foods and feedstuffs recommended in Germany

(Richtlinie 2310 Blatt 29 (E)) was utilized in this case [32, 33]. As

shown in Tab. 3, the Tl levels in all the vegetable samples

highly exceed the MPL for Tl, with the highest (105 mg/g) in the

edible parts of sweet potato followed by the aubergine fruit

(38.4 mg/g). On average, the Tl content in the edible part of the

vegetables is 69.2 times as high as the permissible values. High

Table 3. Heavy metal contents in the edible parts of the vegetables around the Yunfu Sulfuric Acid Factory

Tl (mg/g) Pb (mg/g) Cu (mg/g) Zn (mg/g) Ni (mg/g)

Soybean 22.6 227 30.0 82.9 4.00Taro 5.60 ND 20.0 10.0 4.50Sweet potato 105 43.4 18.5 13.5 3.50Chinese lettuce 14.2 1.50 8.00 12.0 26.0Aubergine 38.4 ND 17.0 18.5 2.50Romaine lettuce 22.0 ND 5.00 25.5 0.50Minimum 5.60 ND 5.00 10.0 0.50Maximum 105 227 30.0 82.9 26.0Mean 34.6 45.3 16.4 27.0 6.80Maximum permissible levela) 0.5 0.3 10 20 1

ND, not detectable.a) The value for Tl is taken from [32, 33]; the others are referred to [31].

Table 2. Heavy metal content (mg/g), pH, and cation exchange capacity (CEC, cmol (þ)/kg) in the arable soils around the Yunfu Sulfuric Acid Factory

Tl Pb Cu Zn Ni pHd) CECe)

Soy bean soil 3.76 43.2 39.4 47.2 22.6 6.72 10.8Taro soil 5.03 52.6 54.6 59.4 26.5 5.91 6.15Sweet potato soil 6.56 85.1 52.9 82.2 34.0 5.56 7.95Chinese lettuce soil 5.32 51.9 70.2 77.0 29.4 5.20 9.66Romaine lettuce soil 7.24 94.2 63.1 88.5 28.4 4.42 5.76Aubergine soil 4.27 68.4 49.8 74.7 24.1 5.63 8.79Minimum 3.76 43.2 39.4 47.2 22.6 4.42 5.76Maximum 7.24 94.20 70.20 88.50 34.00 6.72 10.8Mean 5.36 65.90 55.00 71.50 27.50 5.57 8.18Background soil in Chinaa) 0.58 26 22.6 74.2 26.9 NG NGBackground soil in Guangdong Provinceb) 0.52 36 17 47.3 14.4 NG NGMaximum permissible level in soilc) 1.00 250 50 200 40 NG NG

NG, not given.a) The value of Tl content is taken from [26]; the others are referred to [28].b) The value of Tl content is taken from [26]; the others are referred to [29].c) The value of Tl content is taken from [27]; the others are referred to [30].d) Determined in 1:1 w/v soil/ultra-pure water suspension after equilibration for 15 min [9, 11].e) Determined by using BaCl2–H2SO4 exchange method [9, 11].



contents of Tl were also detected in the French rape (53 mg/kg), the

mustard (147.6 mg/kg) in Poland, the cereal grains (9.5 mg/kg), and

the green cabbage (45 mg/kg) in Germany, and the green cabbage

(120–495 mg/kg) in China [7].

3.3 Heavy metal contents in tissues of vegetables

The heavy metal contents in tissues of the vegetables, such as root,

leave, stalk, and fruit, are presented in Fig. 2. For most of the studied

vegetables, the Tl contents in the subterranean part (root and/or

stalk) are higher than those in the aerial part. The Tl contents in

soybean decrease in the order of root, stalk, leave, and fruit.

Aubergine has higher Tl content in the root than in the other parts.

In the leaf lettuce, the root has much higher Tl content than the

leave. In the taro, the significant enrichment of Tl is found in the root

as well as in the subterranean fruit. A possible reason is that the

likely source of Tl accumulation in the plants is the abnormally high

Tl content retained in the soils and/or surface waters other than

dusts, and root and/or fruit is the part of the plants that is in direct

touch with the soils and/or surface waters. Previous studies have

demonstrated as well that the enrichment of Tl in soil and water may

result in Tl transfer to food crops [7, 33, 34].

Similar to the distribution of Tl, higher levels of Zn were observed

in the subterranean parts than the aerial parts of taro, aubergine

and leaf lettuce. However, Cu and Ni contents in the aerial part

are obviously higher than those in the parts underground. It might

be due to the adsorption of aerosols containing Cu or Ni through the

leaves.

As shown in Tab. 4, the TF values for Tl vary from 2.77 to 27.1. The

mean TF value for Tl is 12.6, which is more than 25 folds higher than

Cu and Ni, 15 times above Zn, and nine times above Pb. This indicates

that Tl is much more inclined to transfer from soil to vegetable. The

high Tl enrichment in the plants could be explained by the non-

discriminatory uptake of Tlþ over Kþ in the organisms of the plants,

due to the similarity of the ionic radii of Tlþ (1.49 A) and Kþ (1.33 A) [7].

The values of Cu and Ni are generally <1.0, which are obviously

lower than other metals (Tab. 4). This indicates that their amount

adsorbed by vegetables from soil via root is quite limited. It may

be explained by that it is more difficult for vegetable to uptake

Cu and Ni from soil, in that soil organic matter can react with

Cu and Ni to form stable complex [17, 35]. Meanwhile, for

most of the studied vegetables, the leaves have notable higher

contents of Cu and Ni than the roots. This might be ascribed to

the contribution of Cu and Ni to the leaves from the atmospheric

dust particles.

3.4 Assessment of health risks from the heavy

metal in the vegetables

3.4.1 Average daily intake dose (ADD)

For the inhabitants around the Yunfu Sulfuric Acid Factory, the daily

ingestion rate of soybean, taro, sweet potato, Chinese lettuce,

aubergine, and romaine lettuce is 7.0, 26.4, 26.4, 106, 106, and

106 g/person per day, respectively [20]. Accordingly, the total ADD

of Tl, Pb, Cu, Zn, and Ni is 3.93, 2.92, 2.06, 3.42, and 1.73 mg/(kg/day),

respectively (see Tab. 4).

3.4.2 Hazard quotient (HQ)

Oral reference dose was based on 0.08, 3.5, 40, 300, and 20 mg/(kg/day)

for Tl, Pb, Cu, Zn, and Ni, respectively [23, 24]. As shown in Tab. 4,

the HQ of heavy metals in the vegetables decreases in the order of

sweet potato> romaine lettuce> aubergine>Chinese lettuce>

taro> soybean (for Tl), sweet potato> soybean>Chinese lettuce>

romaine lettuce� aubergine� taro (for Pb), aubergine>Chinese

lettuce> romaine lettuce> soybean> sweet potato> taro (for Cu),

Figure 2. Heavy metal distribution in the tissues of the vegetables ( soy bean, & taro, & sweet potato, romaine lettuce, Chinese lettuce,aubergine).



romaine lettuce>Chinese lettuce� soybean> taro� sweet potato

> aubergine (for Zn), and Chinese lettuce> aubergine� sweet

potato> soybean> romaine lettuce> taro (for Ni).

The HQ of Tl in sweet potato as well as romaine lettuce amounts

to more than 15, indicating a high potential hazard to the

inhabitants by consuming these kinds of vegetable. The HQ in

Chinese lettuce and aubergine are both around 6, suggesting a

moderate hazard. Besides, a potential low hazard is not negligible

for the inhabitants via intake of Taro and soy bean, for their HQ

of Tl are in the range of 0.1–1.0. However, the HQ of Pb, Cu, Zn, and

Ni in all the vegetables are much lower than 1, indicating that

no immediate hazard is available to the residents by single intake

of Pb, Cu, Zn, and Ni.

In addition, the total HQ from consuming the studied vegetables

planted near the Yunfu Sulfuric Acid Factory lessens in the sequence

of Tl> Pb>Ni>Cu>Zn (Tab. 4). The respective total HQ of Cu, Zn

and Ni is much lower than 0.1, illustrating no hazard arising from

these elements would be exposed to the local residents by consump-

tion of the vegetables. As displayed in Tab. 4, the total HQ of Pb is less

than 1.0, which suggests that a low risk may result from intake of Pb.

But extremely high total HQ of Tl (49.1) in the vegetables indicates

remarkable potential health hazards by intake of Tl. On the

one hand, the toxic effects of Tl on humans, are linked partly to

the readiness whereby Tlþ substitutes for Kþ as an activator of some

reactions catalyzed by enzymes; on the other hand, Tlþ has an

especial affinity for SH-groups and can cause disordered of metabolic

or energy processes in cells of human bodies [33].

4 Summary

The investigation of the arable soils and vegetables grown nearby the

Yunfu Sulfuric Acid Factory in the Western Guangdong Province,

China shows that (1) the soils are significantly contaminated by Tl

with a moderate contamination of Pb and Cu and no contamination

of Zn and Ni; (2) the contents of Tl, Cu, and Ni in the edible parts

of the vegetables though generally exceed the proposed MPL, but

only extremely high potential risks arising from Tl are detected

to the local residents by intake of the vegetables, with total HQ

amounting to around 50. Therefore, the status of heavy metal

contents of the food crops grown in the vicinity of the sulfuric

acid factory and their implications for human health should be

further investigated. Besides, it is high time to take appropriate

measures to control and prevent Tl contamination in the area.

Acknowledgments

This project was performed under the support of the National

Natural Science Foundation Committee of P.R. China (no.

40930743; no. 41173100), the Guangzhou Bureau of Education

(no. 10A029), and the Start-up Scientific Research Project of the

Guangzhou University (WJ05-2001).

The authors have declared no conflict of interest.

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Table 4. Transfer factor (TF), average daily intake dose (ADD), total ADD, hazardous quotient (HQ), and total HQ of the vegetables around the Yunfu

Sulfuric Acid Factory

Tl Pb Cu Zn Ni

TF Soybean 13.5 6.62 0.89 2.64 0.29Taro 2.77 0.00 0.68 0.62 0.34Sweet potato 27.1 1.07 0.60 0.27 0.16Chinese lettuce 4.0 0.27 0.22 0.30 1.17Aubergine 13.5 0.00 0.42 0.43 0.77Romaine lettuce 15.0 0.54 0.13 0.52 0.04

ADD (mg/(kg/day)) Soybean 0.04 2.02 0.37 0.64 0.04Taro 0.06 0.00 0.12 0.22 0.02Sweet potato 1.54 0.64 0.27 0.20 0.05Chinese lettuce 0.48 0.27 0.47 0.71 1.54Aubergine 0.51 0.00 0.53 0.15 0.06Romaine lettuce 1.30 0.00 0.30 1.50 0.03

Total ADD (mg/(kg/day)) 3.93 2.92 2.06 3.42 1.73HQ Soybean 0.53 0.576 0.009 0.002 0.000

Taro 0.75 0.000 0.003 0.001 0.001Sweet potato 19.3 0.183 0.007 0.001 0.003Chinese lettuce 5.95 0.076 0.012 0.002 0.077Aubergine 6.34 0.000 0.013 0.000 0.003Romaine lettuce 16.3 0.000 0.007 0.005 0.001

Total HQ 49.1 0.835 0.052 0.011 0.085



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heavy metal contamination in arable soils and vegetables around a sulfuric acid factory, china

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