Chemosphere 52 (2003) 1411–1422 www.elsevier.com/locate/chemosphere
Persistent organic pollutants in environment of the Pearl River Delta, China: an overview Jiamo Fu a,*, Bixian Mai a, Guoying Sheng a, Gan Zhang a, Xinming Wang a, PingÕan Peng a, Xianming Xiao a, Rong Ran a, Fanzhong Cheng a, Xianzhi Peng a, Zhishi Wang b, U Wa Tang b a
State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China b Faculty of Science and Technology, University of Macao, Macao
Abstract In the Pearl River Delta of China, the rapidly developing industrial and agricultural activities, municipal development and use of chemicals caused serious environmental problems. This report summarizes the published scientific data on POPs in the environment of the Pearl River Delta, including the levels of POPs in the air, water, soil, river and estuarine sediments, the marine organisms like fish and shellfish in this region. The data preliminarily reveal the state of contamination in this region and give insight into the fate of POPs in this sub-tropical area. However, most research in this area is limited to a few kinds of POP compounds. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Air; Marine organism; Pearl River Delta; Persistent organic pollutants; Sediments; Soils; Surface water
1. Introduction Persistent organic pollutants (POPs) have become widespread pollutants in the environment and now represent a global contamination problem. Hazards associated with these pollutants are their persistence in the environment, their bioaccumulation potential in the tissues of animals and humans through the food chain, and their toxic properties for humans and wildlife. POPs may also be transported for long distances by air, rivers and ocean currents, and contaminate regions remote from their source, and then lead to cross-boundary problems that need international efforts for the control of them (Tanabe, 1991; Wania and Mackay, 1996).
*
Corresponding author. Tel.: +86-20-8529-0199; fax: +8620-8529-0192. E-mail address:
[email protected] (J. Fu).
POPs encompass many different and varied groups of man-made chemicals. Some POPs have been highlighted by national and international organizations as being chemicals of concern. For instance, the United Nations Environment Program (UNEP) has listed 12 organochlorine POPs-known as the dirty dozen by the Stockholm Convention. They are dioxins and furans (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, PCDD/Fs); polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), several organochlorines used as pesticides: dichloro-diphenyl-trichloroethane (DDT), chlordane, toxaphene, dieldrin, aldrin, endrin, heptachlor and mirex. The 12 POPs targeted by the Stockholm Convention are of immense concern given that they contaminate the environment and are toxic. There are however numerous other POPs which are also environmental contaminants and are of great concern. Some of them are both persistent and toxic, and still in widespread production and use, in both industrialized and less industrialized countries. These
0045-6535/03/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0045-6535(03)00477-6
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include polycyclic aromatic hydrocarbons (PAHs), hexachlorohexane (HCH) isomers––such as the organochlorine pesticide (OCP) lindane, organotin compounds (for example, used as anti-fouling agents for ships), organic mercury compounds, some other pesticides–– pentachlorophenol, endosulfan and atrazine, chlorinated paraffins (for example, used in cutting oils and lubricants), polybrominated diphenyl ethers (PBDE, used as flame retardants) and certain phthalates: dibutyl phthalate (DBP) and diethyl-hexylphthalate (DEHP), which are less persistent but are not the less hazardous (mainly used as plastic softeners, especially in polyvinyl chloride (PVC)). Studies on the levels of POPs in the global environment show that emission sources of a number of POPs (such as DDTs and HCHs) in late 20 years have shifted from industrialized countries of Northern Hemisphere to less developing countries in tropical and sub-tropical regions including India and China, owing to the late production ban or still being used both legally and illegally in agriculture and for the control of disease such as malaria, typhus and cholera (Tanabe, 1991; Iwata et al., 1994; Loganathan and Kannan, 1994). The Pearl River Delta, including Hong Kong and Macao, is located in Southern China, covering an area of about 8000 km2 (Fig. 1), and has become one of the rapidest developing regions in China in recent decades. The rapidly developing industrial and agricultural activities, municipal development and the use of chemicals have caused serious pollution problems, which have adversely affected the air and water quality in the Pearl River Delta (Wong et al., 1995; Fu et al., 1997; Yang et al., 1997).
2. Sources of POPs Major POPs sources in the Pearl River Delta include contaminants derived from agriculture, industrial, manufacturing discharge and municipal sewage disposal practices. 2.1. Organochlorine pesticides OCPs, such as HCHs, DDT, HCB, chlorodane, aldrin and dieldrin have been widely used from 1950 to 1983 in China. The production of HCHs and DDT in this country were 4.9 million tons and 0.4 million tons, accounted for 33% and 20% of the total world production, respectively (Hua and Shan, 1996). These compounds were used on a large scale in agricultural practices. Subsequent runoff of the compounds in the waterways has resulted in their accumulation in freshwater, estuarine and marine environment in China (Hong et al., 1995; Wu et al., 1999; Yuan et al., 2001). In the Pearl River Delta, it is estimated that OCPs usage was about 76 000–100 000 tons annually from
Fig. 1. The Pearl River Delta and its location. The numbers indicate the eight major outlets to the South China Sea: 1––Humen; 2––Jiaomen; 3––Honqilimen; 4––Hengmen; 5–– Modaomen; 6––Jitimen; 7––Hutiaomen; 8––Yamen.
1972 to 1982 (Hua and Shan, 1996). The application rate of these chemicals has been averaged from 1.8 to 2.7 kg per metric acre in the agricultural zones around the Delta. Although production and usage of DDT and HCHs have been officially banned in China since 1983, pesticide residues remain highly abundant in soils and crops in this area (GAEMS, 1986). In addition, many agricultural lands have been developed for commercial uses in the last two decades, accelerating the remobilization of previously buried OCPs. The OCPs found in environment around the Delta are most likely derived from OCP residues in agricultural soils. Through evaporation (including wind-driven transport of suspended particulate) and surface runoff, OCPs ultimately enter the waterways into the Pearl River system. The Pearl River is believed to carry a considerable load of chlorinated pesticides, up to 863 tons per annum (Zhou et al., 1997), which is the highest amongst ChinaÕs rivers.
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Studies have also showed that usage of some OCPs (such as DDT and c-HCH) in trace amounts may also still been illegally used in some areas of the Delta (Zhou et al., 2001; Mai et al., 2002). 2.2. Polychlorined biphenyls PCBs were produced as industrial chemicals that were mainly used for insulation in electrical equipments. In China, about 10 000 tons of PCBs were produced in the decade from 1965 to 1975, and these were known as PCB3 and PCB5. About 10% of this cumulative tonnage was employed as additives to paint, with the remainder being utilized in electrical industry (e.g. as dielectric fluid in capacitors and transformers) and in carbon-free copy papers (Jing et al., 1992; Yang et al., 1997). Their use was banned in 1980s. However, even today, a large proportion of PCB-containing old transformers and capacitors still remain in use in China, which resulted in continued environmental input (from both deliberate and accidental sources) and as a pool of PCBs remaining in many environment compartments. Other sources of PCBs to the environment were the unwanted by-products of combustion of chlorinecontaining waster, certain chemical processes involving organochlorines, such as PVC, and vehicle exhaust emissions. 2.3. Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans PCDD/Fs are produced as unintentional by-products of many manufacturing and combustion processes that use, produce or dispose of chlorine or chlorine derived chemicals, notably PVC polymers. Important source of PCDD/Fs to the environment include waste incineration, combustion of PVC in landfill fires and open burning, and many organochlorine production processes, including PVC production. Emission from vehicles fuelled with leaded petrol is another source of PCDD/Fs in the environment (Alcock and Jones, 1996). In the Pearl River Delta, although most municipal and industrial wastes were still buried in landfill, several large waste incineration power plants and many small waste incineration factories were built and went into operation since the end of 1980s in some regions of the Pearl River Delta (such as Shenzhen, Zhuhai, Hueizhou). It is estimated that 70% of light industrial waste (such as PVC plastics, rubber, leather and cloth etc.) were mixed with the municipal waste in some region, such as Nanhai, where the production of waste was 215 tons daily. Many PVC production and application industries occurred in the area, and the use of Pb in petrol has just banned in 2000. Therefore, the release of PCDD/Fs from waste incineration, PVC industries and other sources (such as emission from leaded petrol fuelling vehicles) should be of
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particular concern in the area. However, information on the distribution and levels of PCDD/Fs in environment of the Pearl River Delta are very limited. Studies also reported that certain dioxin pollution in some area of China was attributed to the production and use of pesticide sodium-pentachlorophenol (Na-PCP) (Bao et al., 1995; Wu et al., 1997). PCP use is banned in many industrialized countries, but in China, about 5000 tons of PCP were produced annually, and have been used widely to control schistosomiasis and as a wood preservative for making sleepers for railways. So residues of dioxins have been found to be higher in environment medias (such as soils, sediments and foodweb) in area that had been sprayed with the pesticide (Wu et al., 1997, 2001a,b). 2.4. Butyltins Butyltin compounds are widely used as stabilizers, catalysts and biocides. Of the most concern compound in this group, tributyltin (TBT) has been used as the anti-fouling agent in paints for ships and aquaculture nets since the 1960s, although its use is now restricted to large vessels (>25 m) in some of the countries and a global ban is under discussion (European Community, 1989). Butyltins have been considered as the most widely distributed marine toxic contaminants, especially in coastal waters with high shipping activities (Page et al., 1996; Ruiz et al., 1996). Source of TBT in coastal environments are primarily attributed to leaching from ship paint. Owing to its extreme toxicity to aquatic life at low concentrations and its hormone disrupting effects in marine invertebrates (Thain and Waldock, 1986; Valkirs et al., 1987), TBT and other forms of organotin, such as phenyltin, have been legislatively banned in anti-fouling paints since the late 1980s in most European and North American countries. However, only a few countries or regions in Asia have such regulations. Studies have showed that Butyltin compounds were widespread in the Chinese aquatic environment (Jiang et al., 2001). In the Pearl River Delta, there are several huge harbors, and the shipping activities in the area are very busy. Huangpu Harbor and Victoria Harbor were the important harbors in the Pearl River Delta. Huangpu Harbor was located in Guangzhou, the city at the center of the Pearl River Delta, and is the largest harbor in southern mainland China. Victoria Harbor was located in Hong Kong, is one of the largest seaports in the world in terms of tonnage of shipping handled. The use of bultytins has not been regulated in China. Both domestic and international vessels with TBT-containing anti-fouling paint sailing and docking in the area are potential cause of the butyltin contamination in the coastal waters of the area. Other two compounds of the butyltin group, dibutyltin (DBT) and monobutyltin (MBT) are usually
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reported as degradation products of TBT. However, DBD and MBT compounds are commercially used as common PVC stabilizers (Nass, 1967), so they may arise from the leaching of PVC plastics (Schebek et al., 1991). 2.5. Polycyclic aromatic hydrocarbons PAHs are other major contaminants which were studied in many POPs researches of the Pearl River Delta. Athropogenic PAHs mainly produced by processes involving incomplete combustion of fossil fuel and other organic materials, and arise from petrochemical industrial practices. Environmental risks associated with these compounds are related to the carcinogenic character of several individual hydrocarbons (such as benzo[a]pyrene). The major sources of PAHs to the environment of the Pearl River Delta are expected to be industrial sewages (both petroleum and combustion derived), vehicle emissions, and power plant emissions. Non-point source inputs of PAHs to the environment include wet and dry atmospheric deposition and river runoff. Mobile combustion emissions are thought to be primary contributors to PAHs contamination in the atmosphere environment of several urban cities including GuangZhou, HongKong and Macao (Fu et al., 1997; Qi et al., 2001a).
3. POPs in environment of the Pearl River Delta 3.1. Soils Many organochlorine POPs have a high affinity for soil and are retained in this environment medium. Such
POPs may be taken up by crops and by grazing animals and hence reach the human food chain. They may also be washed in run-off from the land into watercourses. In tropical and sub-tropical regions characterized by heavy rainfall, soil erosion can be severe and eroded soils may therefore cause significant pollution of waterways in the tropical countries (Abdullah, 1995). There have been few studies on the fate of POPs in agricultural ecosystems, particularly soils in the Pearl River Delta. Recently, a survey has been carried out on the levels of DDTs and HCHs in differently cultivated and noncultivated soils from the Pearl River Delta in 2000 (Zhang et al., 2001). Fig. 2 gives the mean concentration of DDTs and HCHs present in different types of soils in the Pearl River Delta. A total of 63 soil samples were analyzed. The results showed that high residues of DDTs (averaged 68.5 ng/g in all samples, ranged 15–125 ng/g in 70% samples) and HCHs (averaged 16.2 ng/g in all samples, ranged 2–30 ng/g in 80% samples) were found in agriculture soils. The concentrations of DDTs (averaged 6.7 ng/g) and HCHs (average 8.2 ng/g) in non-cultivated soils are lower than those in the cultivated soils. Rice paddy fields were shown to be heavily DDT-contaminated soils. Levels of DDTs and the isomers of DDTs found in rice paddy soils reflected its past agricultural uses on rice growing. High residuals of HCHs were detected in vegetables, banana, sugar cane and fruit plantation soils, and fish-ponds causeway soils, suggested its former use in agriculture or for fish health purposes. In China, the use of HCHs in agriculture have been restricted since 1983, but the use of technical grade HCHs and lindane (c-HCH) may probably be continued in some area.
Fig. 2. Mean concentration of DDTs and HCHs, and ratios of DDE/DDT and HCHs/DDTs in different soils of the Pearl River Delta. (1) Crop soils: mostly dry. For vegetables, banana, sugarcane and fruits planting; (2) Rice paddy field soil: wet; (3) Rotation soil: for rice and crops as well, managed as dry–wet rotation; (4) Fish-ponds causeway soil: dry, no output of water from the system for crop and fruit planting; (5) Original soil: non-cultivated.
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Levels of individual isomers of DDTs in samples suggest that DDE dominated the compositions of DDTs in most of the samples with an average DDE/DDT ratio of 4.0 for non-cultivated soils and 14.0 for cultivated soils, indicating an on-land weathering process (Fig. 2(c)). The higher HCHs/DDTs ratios in non-cultivated soils as compared with cultivated soils (Fig. 2(d)) suggested that the OCPs in raw soil were manly input from air precipitation tending to favor more volatile HCHs. 3.2. Air There are only limited number of studies which have analyzed levels of persistent organochlorines in air from the Pearl River Delta. Recent study shows the concentrations of DDTs, HCHs, heptachlor and dieldrin in a few aerosol samples from some cities in the Pearl River Delta (Cheng et al., 2000). Concentrations of DDTs in aerosols were found to be higher in Guangzhou (up to 109.38 pg/m3 ) and Zhuhai (up to 65.07 pg/m3 ) than that in other cities in the Pearl River Delta. A recent study was carried out on PCBs levels in gas phase and particulate phase of air from three cities (Guanzhou, Shenzhen and Zhaoqing) in the Pear River Delta (Li et al., 2001a,b). The study detected PCBs concentrations of 297.16–537.41 pg/m3 in gas phase, and 47.50–157.38 pg/m3 in particulate phase. PCBs concentrations in gas phase are higher than those in particulate phase in all samples. Iwata et al. (1994) note that there was a wide variation in the levels of PCBs in air between different locations in tropical Southeast Asia (74–4600 pg/m3 ), although comparable levels were observed over the whole region. The total PCBs concentrations in air samples from the Pearl River Delta fell in the middle
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values of concentration range of air in tropical Southeast Asia, and comparable to or lower than levels in Vietnam (710–830 pg/m3 ) (Iwata et al., 1994). In another recent study on the wet and dry deposition of OCPs in the Pearl River Delta (Qi et al., 2001b), the wet and dry deposition samples from 14 stations in the Pearl River Delta in April–June 2001 were analyzed to assess their deposition fluxes and to give insight to their possible air migration process. The deposition fluxes of HCHs and DDTs are within the range of 0.6– 9.4 ng/m2 /day and 0.4–15.0 ng/m2 /day, respectively. The sampling station on the paddy field had the highest fluxes of HCHs and DDTs, suggesting that the air particulate originated from agricultural soils may contain significant amount of these OCPs. On the other hand, more studies have been conducted on levels and sources of PAHs in aerosols from the Pearl River Delta (Fu et al., 1997; Qi et al., 2001a). Table 1 shows levels of 16 US EPA priority pollutant PAHs in aerosols collected from Guangzhou, HongKong and Macao reported in the study by Fu et al. (1997) and levels in aerosols from Macao reported by Qi et al. (2001a). Levels of PAHs in aerosols varied between locations. Higher levels within this region are associated with industrial and heavy traffic areas, for instance, relatively higher levels within the city of Guangzhou were found for aerosols from commercial regions with heavy traffic (Fu et al., 1997). 3.3. Surface waters A survey of organic micropollutant in surface waters in 1997 was carried out in three main rivers, West River (Shijiang), North River (Beijiang) and East River
Table 1 Range of 16 US EPA priority pollutant PAHs in aerosols of the Pearl River Delta (ng/m3 ) Location of sampling
Guangzhou (n ¼ 17)
Naphthalene Acenaphthene Acenaphthylene Fluorene Phenanthrene Anthracene Fluoroanthracene Pyrene Benzo[a]anthracene Chrysene Benzo[b + k]fluoranthene Benzo[a]pyrene Indeno[1,2,3-c,d]pyrene Dibenzo[a,h]anthracene Benzo[g,h,I]perylene Total 16 PAHs Reference
nd–0.23 0.02–0.41 nd–0.17 nd nd–0.18 nd nd–0.14 nd tr–4.94 nd nd–tr nd 0.12–11.54 0.04–1.04 0.10–12.31 nd–1.25 tr–16.29 nd–1.61 0.15–33.53 nd–1.49 0.23–58.97 0.05–4.39 0.08–25.03 nd–1.91 0.16–22.16 nd–1.43 tr–6.12 nd–0.13 0.18–25.75 nd–1.75 1.29–200.90 0.12–14.88 Fu et al., 1997
nd: Not detected; tr: trace.
HongKong (n ¼ 4)
Macao (n ¼ 6)
Macao (n ¼ 10)
nd–0.75 nd–tr nd nd–0.06 nd nd–tr nd–0.06 tr–0.17 0.83–2.05 0.16–1.45 tr–0.21 tr–0.25 1.12–3.01 0.42–2.84 1.15–4.34 0.64–5.65 0.40–2.42 0.32–6.48 0.83–3.39 0.90–10.51 nd–7.99 2.44–14.77 nd–2.61 0.74–7.90 0.83–4.21 1.70–10.60 tr–0.51 0.42–2.56 1.04–7.24 1.93–17.08 9.01–38.63 9.75–80.31 Qi et al., 2001a
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(Dongjiang) and seven tributaries of the water way network in the Pearl River Delta (Yang et al., 1997). Research results showed levels of the total OCPs in river waters from this survey to be from 130 to 1200 ng/l. The sewage waters from Guangzhou have the highest concentration of DDTs and HCHs (up to 1200 ng/l). The PCBs were also reported to be detectable in all river water samples, although the detected concentrations were lower than 5 ng/l. Other studied have found high levels of organochlorines in water of the Pearl River Delta, for example in Daya Bay, a very important aquacultural area in the Pearl River Delta (Zhou et al., 2001). Levels of HCHs in 4 out of 13 stations were in excess of 500 ng/l, whilst levels of DDTs were particularly high and exceeded 100 ng/l at 6 stations. The DDTs levels are much higher than those found in the raw water of the Lawrence River and its tributaries, Canada (0.30–3.02 ng/l) (Pham et al., 1996) and in the Xiamen Harbor, China (Zhou et al., 2000). It was also noted that the Daya Bay was one of the main aquacultural areas in Guangdong province and levels of DDTs exceeded the Chinese guideline (GB30971997) value (50 ng/l), in the grade 1 seawater which is considered to pose no hazard to the marine ecosystem. The HCHs levels were lower than the Chinese seawater quality guideline value (1000 ng/l)(GB3097-1997), in the grade 1 seawater, in all stations except at one site as far as the level of HCHs in water is concerned. The levels of total PCBs (91.1–1353.3 ng/l) in Daya Bay water are two to four orders of magnitude higher than those detected in Xiamen Harbor, China (0.1–1.7 ng/l) (Zhou et al., 2000), the Humber Estuary, UK (1 ng/l) (Zhou et al., 1996) and the Midway Atoll of North Pacific Ocean (9.1–63.0 ng/l) (Hope et al., 1997). Therefore, water in Daya Bay was thought to be heavily polluted by PCBs. It was suggested that there were a number of sources contributing to total contaminant burden in the bay, including soil runoffs, wastewater discharges, sewage outfalls and shipping activities. In addition to DDT levels providing insight to emission sources of this chemical, the ratio of DDT to its breakdown products DDD and DDE can also serve as a guide to emission sources. High ratios of DDT/ (DDD + DDE) in water ranged from 0.15 to 280.00 and averaged 51.39 in all samples collected from 14 stations were especially found around Daya Bay (Zhou et al., 2001). This indicates fresh inputs of such chemicals into the bay, which eventually find their way into marine environment and global environment, since only small amount of DDE and DDD is contained in commercial products (Iwata et al., 1993). The findings point to the urgent need to develop and use of more efficient and less persistent agrochemicals and phase out outdated and more persistent insecticides such DDT and lindane. Data on organotin pollution of surface waters are very limited. One recent study of butyltins in environ-
ment of the Pearl River Delta reported organotin contamination in four water samples collected from western Pearl River Estuary (Zhang et al., in press). The TBT concentration (21.7–38.5 ng/l) in this study is much higher than the environmental standards for TBT in water proposed in the US (10 ng/l, Federal Register, 1989) and UK (2 ng/l, Cleary, 1992). So the TBT concentrations in waters of the Pearl River Estuary may cause deleterious effects on marine invertebrates. 3.4. Marine organisms (fish and shellfish) Several studies have been conducted on levels of organochlorines and other contaminants in green mussel (perna viridis) from the Pearl River Estuary (Fang et al., 2001) and HongKong waters (Phillips, 1985; Tanabe et al., 1987). These shellfish have a wide geographical distribution in the Southeast Asia–Pacific region and grown as a commercially valuable seafood for worldwide markets. Studies on the levels of contaminants in mussels have been conducted to cheek contamination levels in the interests of public safety. In addition, mussels have also been used as bioindicators to assess the state of marine pollution by toxic contaminants and to understand the fate and effects of contaminants in tropical regions. The international Mussel Watch Scheme has used mussels and other shellfish in the Southeast Asia–Pacific region for this purpose (Tanabe, 1994). Table 2 shows levels of organochlorines in green mussels collected from 13 sites along the Pearl River Estuary from July to August 1996, reported in the study by Fang et al. (2001). The ranges of HCHs, DDTs and PCBs in mussels were in the rang of not-detected––1.1, Table 2 Concentrations of HCHs, DDTs and PCBs in green-lipped mussels (perna viridis), collected from the Pearl River Estuary, July to August 1996 (ng/g, lipid weight basis) Locations
HCHs
Lajia Island JuaoZhou Luohesha Beijiao Pier Tsim Sha Tsui Pier (Victoria Harbor) Ludi Bay Outer Lingding Island Guoshan Island Dongao Island Daiwangshan Island Hebao Island Daiwan Bay Datiwan Bay Source: Fang et al., 2001. nd: Not detected.
DDTs
PCBs
0.5 nd nd 0.6 0.5
9.5 12.3 12.8 72.6 51.4
91.8 109.6 82.8 197.0 615.1
0.4 0.5 nd 0.6 0.4 1.1 nd 1.1
76.2 191.0 131.4 72.8 54.7 143.9 45.6 47.6
145.0 289.0 205.5 124.5 138.0 243.3 84.0 86.9
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9.5–191 and 82.8–615.1 ng/g (lipid weight basis), respectively. Mussels collected from Tsim Sha Tsui pier (Victoria Harbor) showed the highest contamination of PCBs, while those collected from Hebao island (western estuarine zone) had relative high contamination by DDTs and HCHs. The PCBs distribution profile also indicated that there were two different PCB pollution sources in the Pearl River Estuary, one from Guangzhou and another from HongKong. The distribution patterns of DDT and its breakdown products reflect that run off from soils contaminated with DDTs by extensive use in the Delta continues to be a major source of this chemical to the aquatic ecosystem of the Pearl River Estuary, and there may have current input of fresh DDT to the aquatic environment due to illegally use in agricultural practices in some areas of the Pearl River Delta, as suggested by the DDT results of river waters and sediments (Zhou et al., 2001; Mai et al., 2002). A recent study reported the levels of organotins in several marine organisms (fish, mussel and shrimp) from the Pearls River Estuary (Zhang et al., in press). The TBT concentrations of fish tissue samples vary from 4.8 to 18.8 ng/g wet weight. This level is within the range of fish TBT concentrations in most Asian coasts (India, Thailand, Indonesia, Taiwan and Vietnam) (Guruge and Tanabe, 2001 and references therein). The TBT concentration of the mussel sample (13.2 ng/g) is identical to that of the fish samples (18.8 ng/g), and higher than that of shrimp (3.6 ng/g). The calculated biota-water partition coefficients (log Kp ) of TBT for fish, mussel and shrimp are 2.4, 2.5 and 2.0, respectively, indicated bioconcentration factors at the 102 level from water to biota body. 3.5. River and estuarine sediments Sediments act as an ultimate sink for POPs brought into the aquatic environment from direct discharges, surface run-off and atmospheric fall out. Several surveys have been carried out on levels of organochlorines and PAHs in sediments from river and estuarine waters in the Pearl River Delta (European Commission, 1998; Hong et al., 1999; Zhang et al., 1999; Kang et al., 2000; Mai et al., 2000; Fu et al., 2001; Li et al., 2001a,b; Mai et al., 2001; Zhou et al., 2001; Mai et al., 2002). Results are presented in Table 3. These studies showed that levels of DDTs and HCHs in sediments from the Pearl River Delta were relatively high when compared to levels of DDTs and HCHs in most sediments from Southeast Asia and Oceania countries reported by Iwata et al. (1994). Studies revealed very high levels of DDTs, and PCBs in some areas, for example, Guangzhou Branch of Zhujiang River (Kang et al., 2000; Mai et al., 2002), Macao Inner Harbor (Kang et al., 2000; Mai et al., 2002) and Daya Bay (Zhou et al., 2001). It was concluded that substances such as PCBs DDTs and
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HCHs in the Pearl River Delta sediments were the results of trace discharges in stormwaters, sewage, industrial waste, agricultural run off, atmosphere deposition and were of long term significance to the quality of waters in this area. As shown in Table 3, the ratios of DDT/(DDE + DDD) in some sediments is particular high, suggesting there are still have fresh inputs of DDT to the bed sediments at some areas of the Pearl River Delta. These studies commented that DDT is officially banned for agricultural use in China, but it may be illegally used in trace amounts recently for some agricultural practices. Furthermore, with recent liberalization of the agrochemicals market, there has been a tendency towards the application of cheaper pesticides and there are concerns that some banned OCPs, including DDT, may be available to farmers and result in widespread environmental contamination. The levels of PCBs, DDTs and PAHs in the Pearl River Delta sediments have been compared with that in other places in the world by a study (Mai et al., 2002). The sediments in Zhujiang River (48.3–486 ng/g) and Macao Harbor (339 ng/g) were thought to be moderately to strongly contaminated by PCBs, when compared to the world-wide concentrations (0.2–400 ng/g) of near-shore surface sediments (Fowler, 1990). While PCB levels in sediment from Shiziyang (10–30.3 ng/g) and Xijiang (11–13.6 ng/g) Rivers, and Lingding Bay (10.2– 13.5 ng/g) were comparable to those of sediments from Canadian Midlatitude and Arctic Lake sediments (2.4– 39 ng/g) (Muir et al., 1996). The DDT concentration (1629 ng/g) in sediment from Macao Inner Harbor is higher than those obtained in other heavily polluted locations, such as Rhone prodelta in the north-west Mediterranean region (124–657 ng/g) (Tolosa et al., 1995). DDTs levels in sediments of Zhujiang (35.1–91.0 ng/g) and Shiziyang (22.9–40.4 ng/g) rivers were fell in the high values of the world-wide concentration range, and comparable to those of moderately polluted locations, such as Ebro prodelta in the NW Mediterranean region (23–89 ng/g) (Tolosa et al., 1995). While DDTs concentrations in sediments of Xijiang river (5.0–16.6 ng/g) and Lindding Bay (2.6–10.6 ng/g) (except one sample near Macao) were fell at the low values of the world wide concentration range, and comparable to those measured in other agricultural locations, such as San Joaquin River (Pereira et al., 1996). The 16 PAHs concentrations of Zhujiang river (1434–10 811 ng/g) and the Macao Harbor (9220 ng/g) are closely to those obtained from other urbanized and industrialized areas, such as Brisbane River (3940– 16 110 ng/g) (Kayal and Connell, 1989), Georges River (56–21 400 ng/g) (Brown and Maher, 1992), Tamar Estuary (430–14 070 ng/g) (Readman et al., 1986), and Casco Bay (215–14 400 ng/g) (Larsen et al., 1983), which have been considered as moderately polluted areas. Nevertheless, these are relatively low if compared to
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Table 3 Concentrations (ng/g, dry wt.,) of organochlorines and PAHs in river and estuarine sediments from the Pearl River Delta Locations
Sampling date
Remarks
HCHs
DDTs
PCBs
PAHs
DDT/ (DDE + DDD)
References
Zhujiang River (n ¼ 3) Shiziyang River (n ¼ 3) Xijiang River (n ¼ 4) Lingding Bay (n ¼ 6) Macao Harbor (n ¼ 1)
1997
Urban area Agricultural area Agricultural area Estuary
4.5–17.0
35.1–91.1
52.1–486
1434–10 800
0.32–0.94
2.2–3.2
22.9–40.4
16.0–30.0
408–854
0.28–0.65
1.2–4.0
5.0–16.6
11.0–14.9
709–1589
0.38–1.11
nd–2.6
2.6–115.6
10.2–11.9
156–1570
0.21–4.41
Mai et al. (2002), Fu et al. (2001), Mai et al. (2001), Kang et al. (2000)
Pearl River Estuary (n ¼ 12) Pearl River Estuary (n ¼ 8) Zhujiang River (n ¼ 1) Pearl River Estuary (n ¼ 1) Macao Estuary (n ¼ 23) Pearl River Estuary (n ¼ 15) Daya Bay, Shenzhen (n ¼ 14)
1997 1997 1997 1997
2.4
1629
339
9220
0.42
1996
Urban area (estuary) Estuary
0.28–1.06
1.54–5.38
0.18–0.89
318–1849
0.29–0.91
1997
Estuary
0.29–1.23
1.36–8.99
0.31–1.68
208–887
0.65–1.11
1995
Urban area Estuary
72.5
11.1
Core sediments Core sediments Aquacultural area
tr–82.3
tr–79.0
0.43–5.19
2.19–26.5
0.32–4.16
0.20–20.27
1996 1997 1997 1999
28.57
2.49
0.85–27.37
6.4
0.95–25.32
0.95–25.32
Hong et al. (1999)
Wu et al. (1999) Yuan et al. (2001) Zhang et al. (1999) Li et al. (2001a) Zhou et al. (2001)
That is the total 16 US EPA priority PAH concentration. nd: Not detected. tr: Trace.
those found in highly polluted areas, such as Boston Harbor (483–718 000 ng/g) (Shiaris and Jambard-Sweet, 1986), Chespeake Bay (555–178 000 ng/g) (Foster and Wright, 1988), and New Bedford Harbor (14 000– 170 000 ng/g) (Pruell et al., 1990). On the other hand, the concentrations of Shiziyang (590–854 ng/g) and Xijiang river samples (709–1589 ng/g), and Lingding Bay (134– 996 ng/g) are similar to or slightly higher than those undergoing reasonable anthropogenic impacts, such as San Joaquin River in California (5–756 ng/g) (Pereira et al., 1996), Gulf of Maine (10–512 ng/g) (Larsen et al., 1986), Western Mediterranean Sea (149–1655 ng/g) (Lipiatou and Saliot, 1991) and Northwestern Mediterranean Sea (147–2427ng/g) (Tolosa et al., 1996). The concentration of PCBs, DDTs and PAHs in the study of Mai et al. (2002) were also compared by mean of two guideline values, an effects range low (ERL) and effects range median (ERM), which were designated to assess the potential for biological effects of sedimentsorbed contaminants by Long et al. (1995). In all the sediment samples of this study, there is at least one constituent that may occasionally pose biological impairment (with concentration greater than ERL). Four
samples had constituents that frequently pose biological impairment (with concentrations greater than ERM). The sediments from Macao Harbor and Zhujiang River had the highest level of organochlorine and PAH constituents, with concentrations greater than ERL or ERM. These findings indicated that sediments of the Zhuujiang River and Macao Harbor had the potential to be detrimental to biological systems. A recent study on levels of organotins in surface sediments from the Pearl River Delta reported that levels of TBTs ranged from 1.7 to 379.7 ng/g (Zhang et al., in press). Compared to other parts of the world, the TBT concentration in the Pearl River Delta sediments is relatively low. High TBT concentrations (328.7– 377.7 ng/g) were found in sediments from the Front Channel of Zhujiang River, where more than 30 shipyards and ship-repairers owned by various enterprises were located. It was suggested that shipping activities, especially shipyards, were mostly responsible for the TBT contamination in the region. Limited studies were available in the scientific literature on levels of PCDD/Fs in environment of the Pearl River Delta. A study by Zheng et al. (2001)
J. Fu et al. / Chemosphere 52 (2003) 1411–1422
reported the 2,3,7,8-substituted PCDD/Fs concentrations in eight sediment samples from the Pearl River Delta. The results showed that only 6 of 17 congeners of 2,3,7,8-substituted PCDD/Fs were detected in sediments. OCDD had the highest concentrations (472–2502 pg/g), followed by 1,2,3,4,7,8,9-H7CDD (nd–100 ng/g) or OCDF (nd–334 ng/g). The reported concentrations of PCDD/Fs were 0.6–17.5 I-TEQ (international toxic equivalence factors). Based on limited sample numbers, they noted that samples from upper reaches in Zhujiang River contain somewhat higher levels of OCDD than samples from lower reaches. The pattern of PCDD/Fs in sediments dominated with OCDD suggested that the dioxin pollution in these sediments could be related to past use of sodium pentachlorophenol (Na-PCP) in upper reaches of Zhujiang River (Zheng et al., 2001). Na-PCP has not been utilized in the Pearl River Delta in recent years, but it is expected that most of the dioxins emitted in past pesticide impurities still exist in agricultural soil and they will continue to flow into water bodies and pollute sediment in the future. Since the number of samples during the study was small (eight samples) and full congener-specific data are unavailable, using low-resolution mass spectrometry for analysis, it is very difficult to assess the state of PCDD/Fs pollution and to identify the sources of PCDD/Fs in sediments of this area at present. Although past PCP use is a known source of dioxins, the present production of dioxins is deemed to be combustion and widely use of chlorine chemicals (such as PVC) in this region. As reported by Zhang et al. (2002), DDTs and HCHs in eight 210 Pb-dated sedimentary cores from the Pearl River Delta, South China, were analyzed in order to reconstruct the time trends of these POPs in the region. The sedimentary inventories of DDTs and HCHs through the cores ranged from 36.6 to 1109.5 ng/cm2 and from 11.2 to 226.3 ng/m2 , respectively. Although a production ban of technical HCH and DDT was imposed in China in 1983, their sedimentary fluxes display increasing trends or strong rebounds in the 1990s as recorded in the core profiles. It is suggested that an enhanced soil runoff in the process of large-scale land transform, as well as a higher river water flow in early 1990s, had mobilized these pesticides from soil to the sedimentary system in the region.
4. Conclusions (1) Studies on POPs in environment of the Pearl River Delta demonstrate that the levels of DDTs and HCHs in various environmental media are of great concern. The PCBs is also concerned in water and sediments of some areas such as Guanzhou Branch of Pearl River (Zhujiang River), Macao Inner Harbor, and Daya Bay. Sediments of the Zhujiang river
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and Macao Harbor are most likely to pose biological impairment. The TBT concentrations (21.7– 38.5 ng/l) in water of Pearl River Estuary exceeded TBT levels (2–10 ng/l) that are thought to cause adverse effect in shellfish. (2) There is evidence from the distribution profiles of DDT and its degradation products that inputs of fresh DDT still continues in some regions of the Pearl River Delta. (3) Of the available data, most is restricted to investigating levels of a few organochlorines (DDTs, HCHs and PCBs) with little or no data on other POPs such as brominated flame retardants and chlorinated paraffins. Research on levels of dioxins and furans in the environment of Pearl River Delta is very limited. (4) In the future study on POPs in this region, investigation should be enhanced on fully characterizing and remedying the POPs data gap first, their occurrence in marine and terrestrial living organisms, their transfer from food web to human, and subsequently their air–land/air–ocean exchange, their land–ocean interaction and cycling between Pearl River Delta and South China Sea, and finally, the contributions of POPs from this sub-tropical region to the pollution of global environment.
Acknowledgements This research was supported largely by the Natural Science Foundation of PeopleÕ Republic of China under Project No. 49972094 and No. 40272129. Partial support from the Guangdong Natural Science Foundation under Project No. 010504 is also gratefully acknowledged.
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