ARTICLE IN PRESS + MODEL http://www.paper.edu.cn Environmental Pollution xx (2005) 1e7 Cadmium contamination in orchard soils and fruit trees and its potential health risk in Guangzhou, China J.T. Li a, J.W. Qiu b, X.W. Wang a, Y. Zhong a, C.Y. Lan a,*, W.S. Shu a,* a School of Life Sciences and State Key Laboratory of Biocontrol, Sun Yat-sen (Zhongshan) University, Guangzhou 510275, PR China b Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong, PR China Received 6 August 2005; received in revised form 19 September 2005; accepted 14 October 2005 Carambola fruit can accumulate high levels of cadmium and may be a health risk for humans. Abstract This study examines cadmium (Cd) contamination in orchard soils and fruit trees in Guangzhou, China, and assesses its potential health risk. Soils and tissues samples of three species of fruit trees were collected from three orchards. The average soil Cd concentration was 1.27, 1.84 and 0.68 mg/kg in orchards I, II, and III, respectively. The carambola (Averrhoa carambola) accumulated exceptionally high concentrations of Cd (7.57, 10.84, 9.01 and 2.15 mg/kg dw in root, twig, leaf and fruit, respectively), being 6.0e24 times and 4.0e10 times the corresponding tissue Cd in the longan (Dimocarpus longan) and wampee (Clausena lansium), respectively. Furthermore, all Cd concentrations (0.04e0.25 mg Cd/kg fw) of the fruits exceeded the tolerance limit of cadmium in foods of PR China (0.03 mg/kg fw). Our results indicate that the carambola tree has high Cd accumulation capacity and might be a Cd accumulator; and its fruit, among the three species of fruits studied, also poses the highest potential health risk to local residents. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Cadmium; Accumulator; Fruits; Health risk 1. Introduction have resulted in the release of significant quantities of Cd to the environment (WHO, 1992; Manta et al., 2002; Komarnicki, Cadmium (Cd) contamination of agricultural soil is of 2005). Cadmium in soil is easily accumulated by plants worldwide concern due to the food safety issues and poten- through the root system, compared with other toxic metals tial health risks (Dudka et al., 1996; McLaughlin et al., 1999; (Thuvander and Oskarsson, 1998). Hence, the soil-plant- Dorris et al., 2002; Tsadilas et al., 2005). Cadmium can accu- human transfer of Cd has been considered as a major pathway mulate gradually in the human body, where it may lead to of human exposure to soil Cd (Cui et al., 2004). a number of adverse health effects, such as nephrotoxicity Environmental pollution of Cd occurs widely in China re- and osteotoxicity (WHO, 1992). sulting from its rapidly economic development during the The two major sources of Cd in soils are natural occurrence past two decades (Jin et al., 2004). The potential health risks derived from parent materials and anthropic activities (WHO, due to soil Cd contamination have been well assessed in 1992). Numerous human activities, such as mining, waste dis- China. However, most of the previous investigations have posal, vehicle exhausts and phosphate fertilizer application, focused on rice (Wang et al., 2001; Xiong et al., 2004), wheat (Nan and Cheng, 2001; Nan et al., 2002) and vegetables (Zhou et al., 2000; Cui et al., 2004). Very little information is available on Cd accumulation in orchard soils and fruits * Corresponding authors. Tel.: þ86 20 84036296; fax: þ86 20 84113652. (Santos et al., 2004). In Guangzhou, a major city in southern E-mail addresses: [email protected] (C.Y. Lan), [email protected] (W.S. Shu). China, no such information is available for the assessment of 0269-7491/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2005.10.016 转载 ARTICLE IN PRESS 中国科技论文在线 http://www.paper.edu.cn 2 J.T. Li et al. / Environmental Pollution xx (2005) 1e7 health risk. Therefore, the objectives of this work were to: (1) The aerial parts were sampled by using a pair of stainless steel scissors, and quantify the Cd contamination in orchard soils and fruits; (2) the roots (about 0.5e1 cm in diameter) were scooped up using a stainless evaluate the potential health risk of human fruits consumption; shovel. All samples were stored in polyethylene bags in the field and trans- ferred to the laboratory within 3 h for preparation. and (3) relate Cd accumulation in fruits and the associated soil After removal of visible pieces of plant residues, the soils were air-dried, conditions. crushed, sieved through a 2-mm screen, then pulverized and passed through a 0.2-mm mesh sieve. The plant samples were washed with tap water followed 2. Materials and methods by deionized water to remove soil particles or dust adhering to the plant sur- face and dried with tissue paper. The fruits were separated into edible and in- 2.1. Site description edible parts. All of the plant samples were then oven-dried at 70 C for 72 h to a constant weight. Fresh and dry edible fruits parts were weighed. Prior to The present investigation was conducted in Guangzhou City (22 26# to chemical analysis, all dry plant samples were ground into fine powder by 23 56#N, 112 57# to 114 03#E), the capital of Guangdong Province, southern a stainless steel mill. China. The area has a typical subtropical monsoonal climate, with annual av- erage temperature of 23.0 C and rainfall of 1782.9 mm (Guangzhou Year- 2.3. Chemical analysis book, 2003), which is very suitable for the growth of most subtropical fruits. The carambola (Averrhoa carambola), the longan (Dimocarpus longan) Soil pH value was measured in a 1:2.5 (w/v) ratio of soil to distilled water and the wampee (Clausena lansium) studied in this work are three species of using a pH meter. Soil organic matter (OM) content was determined by a wet- the most favorite and economically important fruits of the city, and they are combustion method (ISSCAS, 1978). Soil cation exchange capacity (CEC) also very popular in many southeast Asian countries. In 2002, the production was determined by the BaCl2 compulsive exchange method (Gillman and of the carambola and longan in Guangzhou amounted to 6875 and 37,968 tons, Sumpter, 1986). For total Cd determination, the soil samples were digested respectively (Guangzhou Yearbook, 2003). Three large orchards with different in 4 ml of ‘‘aqua-regia’’ (HNO3/HCl ¼ 1/3, v/v; McGrath and Cunliffe, irrigation water sources were included in this study (Fig. 1). Orchard I and or- 1985). The ‘‘plant available’’ Cd in soils was extracted with a diethylenetet- chard II are located in the same district (Hai-Zhu District), and have direct ac- raminepentaacetic acid (DTPA) solution (0.005 M DTPA þ 0.005 M cess to the Pearl River through irrigation channels. Orchard I is about 3 km and CaCl2 þ 0.1 M TEA, pH ¼ 7.3; Lindsay and Norvell, 1978). Total Cd in plant orchard II about 1 km from the town center, whereas orchard III is located in materials was extracted with a mixture of concentrated HNO3 and concentrated another district (Tian-He District), being inaccessible to the Pearl River. HClO4, at 5:1 (v/v) (Allen, 1989). Cd concentrations were determined using an atomic absorption spectrophotometer (Hitachi-Z-5300). Quality control of soil and plant materials analysis was performed using a certified concentration of 2.2. Sampling and preparation Cd solution (GBW-08612) obtained from the National Center for Standard Materials. The sampling was carried out in August 2004. Ten samples of soils and plant tissues (including root, twig, leaf and fruit) of the carambola were col- 2.4. Data analysis lected from each of the three orchards (Fig. 1). The roots of the carambola were collected only in orchard I, because the sampling of roots was not per- 2.4.1. Soil Cd contamination assessment mitted in the other orchards. Each soil sample (about 1 kg) was a composite The degree of Cd contamination in the orchard soils was determined by the of five sub-samples taken from a depth of 0e20 cm. The carambola samples geo-accumulation index (I-geo) as proposed by Muller (1969): were collected from the associated soil-sampling sites for correlation purpose. The carambola trees in the three orchards belonged to the same local cultivar I-geo ¼ log2ðCn=1:5BnÞ (Averrhoa carambola cv. Hua-Di). In orchard I, since the longan (Dimocarpus longan cv. Shi-Jia) and wampee (Clausena lansium cv. Ji-Xin) trees were where Cn represents total Cd concentration in orchard soil, Bn is the natural planted along with the carambola within 5 m  5 m plots, so 10 tissue (root, background soil Cd concentration in Guangzhou (0.14 mg/kg; GDPEMC, twig, leaf and fruit) samples of the two trees were also collected, respectively. 1990) and 1.5 is a correction factor. Based on I-geo, the Cd contamination Fig. 1. Map of Guangzhou, showing the location of orchards I, II and III. Soil and tissues of tree samples were collected from the three orchards as indicated by filled triangles, and the sampling sites in the orchards are indicated by filled circles. The main tributes of the Pearl River and the irrigation channels connecting with them are shown as filled curves. The empty curves represent the roads. ARTICLE IN PRESS 中国科技论文在线 + MODEL http://www.paper.edu.cn J.T. Li et al. / Environmental Pollution xx (2005) 1e7 3 levels of soil are classified into seven grades: 0 (grade 0) represents uncontam- potentially ecological risk (Liu et al., 2002).