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Persistent chlorinated pesticides in fish species from Qiantang River in East China
Chemosphere 68 (2007) 838–847 www.elsevier.com/locate/chemosphere
Persistent chlorinated pesticides in fish species from Qiantang River in East China Rongbing Zhou, Lizhong Zhu *, Qingxia Kong Department of Environmental Science, Zhejiang University, Hangzhou, Zhejiang 310028, PR China Received 13 April 2006; received in revised form 30 December 2006; accepted 10 February 2007 Available online 8 April 2007
Abstract Thirteen organochlorine pesticides (OCPs) in 18 fish species from Qiantang River were firstly determined by GC-ECD. To elucidate the sources and the environment fate of these pollutants, water and sediment samples were also analyzed for OCPs contents. Total concentrations of OCPs in fish muscles ranged from 7.43 to 143.79 ng g1 wet weight (ww) with highest concentration recorded in sole fish (Cynoglossus abbreviatus), a benthic carnivore. The results indicated that carnivore fish have higher OCPs concentration than other fish with different feeding modes. OCPs concentration in fish was in the range of 1.86–5.85, 2.65–133.51 and 1.94–12.48 ng g1 for HCHs (a-, b-, c-, d-HCH), DDTs (p,p 0 -DDD, p,p 0 -DDE, p,p 0 -DDT, o,p 0 -DDD) and other OCPs (aldrin, diedrin, endrin, heptachlor, heptachlor expoide), respectively. The highest OCPs concentration in fish organs of four big fish species was found in brain of silver carp (Hypophthalmichthys molitrix), 289.26 ng g1 ww followed by kidney, liver, heart and gill. Among the OCPs analyzed, DDE, c-HCH and heptachlor were the predominant contaminants in fish muscle, which indicated that there was recent input of lindane. Significant correlation was observed between concentrations of DDTs and lipid content as well as between OCPs and lipid contents in fish species. Both field water bioconcentration factors (BCF) and sediment BCF showed a positive correlation with octanol-water partition coefficients (Kow) in the sole fish. 2007 Elsevier Ltd. All rights reserved. Keywords: HCH; DDT; BCF; Fish; Qiantang River
1. Introduction Organochlorine pesticides (OCPs) such as hexachlorocyclohexane (HCH) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) are ubiquitous anthropogenic environmental contaminants (Nakata et al., 1998; Willett et al., 1998) because they are persistent, broad-spectrum toxicants that tend to accumulate in the food web and have the potential to adversely affect the ecosystem and human health. Although the application of these chemicals has been banned or restricted in many countries especially the developed ones, some developing countries are still using these compounds because of their low cost and versa*
Corresponding author. Tel./fax: +86 571 88273733. E-mail addresses: [email protected] (R. Zhou), [email protected] (L. Zhu). 0045-6535/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2007.02.021
tility in industry, agriculture and public health (Tanabe et al., 1994; Sarkar et al., 1997). OCPs can enter the water environments by runoff from non-point sources, discharge of industrial wastewater, wet or dry deposition and other ways and persist for a long period. They can be transferred into food chains and finally reach human beings. Therefore, the residues of OCPs might ultimately pass onto people through consumption of drinking water, fish and agriculture food (Oehme and Mano, 1984; Kawano et al., 1988; Iwata et al., 1993). Fish is a suitable indicator for the environmental pollution monitoring because they concentrate pollutants in their tissues directly from water, but also through their diet, thus enabling the assessment of transfer of pollutants through the trophic web (Fisk et al., 2001). Data on the presence and distribution of OCPs in fish and especially edible fish species are therefore important not only from
R. Zhou et al. / Chemosphere 68 (2007) 838–847
ecological, but also human health perspective. Humans are exposed inadvertently to persistent organic pollutants (POPs) through numerous sources, of which the consumption of contaminated fish is one of the most important pathways. China is a large producer and consumer of pesticides in the world. Large amounts of OCPs were used in past decades to obtain high yield to sustain overpopulation in China. HCH and DDT were widely used in China from 1952 to 1983. The total production of technical HCH and DDT is around 4 million tons and 0.27 million tons, respectively. Even after the ban of technical HCH and DDT in 1983, 3200 tons of lindane (almost pure c-HCH) was still in use between 1991 and 2000, and DDT production also continues due to export demand and dicofol production (Zhang et al., 2002; Qiu et al., 2004; Tao et al., 2005). OCPs pollution of aquatic biota was widespread in China (Klumpp et al., 2002; Feng et al., 2003; Jiang et al., 2005; Kong et al., 2005; Nakata et al., 2005; Yang et al., 2005, 2006), neighbouring countries (Nhan et al., 2001; Das et al., 2002) and other developing countries (Nemr and Abd-Allah, 2004; Erdogrul et al., 2005) as well as developed countries (Bayarri et al., 2001; Bordajandi et al., 2003; Yamaguchi et al., 2003; Sapozhnikova et al., 2004). Qiantang River Basin has been rice and orange fields for several centuries with a populous area of 55 558 km2. Economically, tens of millions of people depend on Qiantang River as a source of fresh drinking water and fishing as source of favorite food in the local diet. All species investigated in this study are consumed by the population. Distribution of OCPs in surface water, sediment and soil in Qiantang River has been reported (Zhou et al., 2006). However, few studies have investigated the presence of
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OCPs in local aquatic biota. The objectives of this study were to (1) investigate the levels of OCPs in 18 fish species from Qiantang River; (2) compare distribution of OCPs among main organs in big fish species (>200 g); (3) study field bioaccumulation levels of OCPs in fish species. 2. Material and methods 2.1. Sample collection Qiantang River is located in the south of Yangtze Delta region of China and drains into the East Sea. Fuchun Reservoir possesses an important dam in the upstream of Qiantang River with a maximum capacity of 8740 hm3. Sampling was carried out from July to October 2005. A total of 54 individual adult fishes, representing 18 common species were obtained from local fishermen at two sites in Qiantang River (Fig. 1). One was near Hangzhou, the other was near Tonglu. Hangzhou is the capital of Zhejiang province, located downstream of Qiantang River. Tonglu is a rural area, located upstream of Qiantang River, near the dam. Surface water and sediment samples were also collected at two sites. All the sediment samples were composite samples collected from 4 to 5 points (0–20 cm) in each site using a stainless steel grab. Information on the fish length, weight, and feeding mode is given in Table 1. All the water samples were filtered through 0.45 lm fiber glass filters to remove sand and debris after returning to the laboratory and stored in the dark at temperature between 0 C and 4 C prior to extraction within two days. All the fish and sediment samples were immediately transported to the laboratory. Fish from each site consisted of 3 individual samples of the same species. Four big fish species were
Hangzhou
China
East sea
S1 Tonglu Dam
S2 Qiantang River
0
Fig. 1. Map of Qiantang River and sampling sites.
6 Km
840
R. Zhou et al. / Chemosphere 68 (2007) 838–847
Table 1 Biometric data and feeding mode of 18 fish species from Qiantang River Sampling location
Code
Common name
Species
Feeding mode
Weight (g)
Length (cm)
S1
A B C D E F G H I J
Saury Redlip mullet White fish Sole – Crucian carp Gurnet Leather carp Silver carp Perch
Coilia ectenes Jordan Liza haematocheila Erythroculter ilishaeformis Cynolossus abbreviaius Leiocassis longirostris Carassius auratus Megalobrama terminalis Cyprinus carpio Hypophthalmichthys molitrix Lateolabrax japonicus
Carnivore Omnivorous Carnivore Carnivore Carnivore Omnivorous Herbivorous Omnivorous Herbivorous Carnivore
41 36 115 96 71 41 200 1500 600 500
24 17 22 19 26 24 28 54 30 28
S2
K L M N O P Q R
– – Sheatfish – – Snake head mullet Bulltrout Bleeker
Erythroculter mongolicus Hemibarbu maculates Silurus osotus Linnaeus Acanthobrama simony Culter alburnus Odontobutis obscura Squaliobarbus curriculus Erythroculter dabryi
Carnivore Carnivore Omnivorous Omnivorous Carnivore Carnivore Herbivorous Carnivore
48 51 52 14 17 55 11 65
33 17 22 12 13 16 11 22
dissected immediately and samples were collected from different organs: gill, liver, kidney, brain, spleen, heart, ovary. All fish and sediment samples were stored in the laboratory at 20 C. All the equipment used for sample collection, transportation, and preparation were free of organochlorine contamination. All the glassware were pre-cleaned with ultra-pure water (PALL system) in an ultra-sonic cleaner (KQ-300DE, Kunshan Ultrasonic Instrument). 2.2. Extraction and clean-up procedure Fish samples were defrosted and homogenized by using a manual homogenizer. Approximately 10 g of homogenized tissues were grounded with 30 g of anhydrous sodium sulphate and extracted with 200 ml of hexane: acetone (3:1, v:v) mixture in a Soxhlet apparatus for 8 h. After concentrating the extracted solvents, lipid content was determined gravimetrically from an aliquot of the extract. The extracts were concentrated with a rotary evaporator at 40 C. For the clean up, the residue was dissolved in 1.5 ml hexane according to Manirakiza’s method (Manirakiza et al., 2002). For acid-stable pesticides, a 25 ml empty cartridge was filled with 3 g of ashed, activated and H2SO4 impregnated silica (45%, w/w) and washed with 6 ml hexane. The fat residue was loaded onto the cartridge and the elution was done with 2 · 5 ml hexane: dichloromethane (3:1, v/v) in a 25 ml conical flask. The eluates were finally reduced to 200 ll with nitrogen gas for GC injection. For non acid-stable analytes, such as diedrin and endrin, a 25 ml empty cartridge was filled successively with 2 g alumina, 2 g silica gel and 2 g Florisil (60–100 mesh, Wenzhou chemical reagent factory, China). All of them were impregnated with a 15% KOH methanolic solution (50%, v/w). Before the extract was loaded, 1 g of Na2SO4 was added at the top and the cartridge washed with 6 ml hexane. The elution was done with 2 · 5 ml fraction of hexane-
dichloromethane (3:1) in a 25 ml conical flask. The eluates were concentrated to 200 ll for GC injection. Solid phase extraction (SPE) cartridges system from Supelco was used to extract water samples according to Zhou’s method (Zhou et al., 2002). Before the extraction, the Supelco SPE cartridges (Supelclean Envi-18) were first washed with 5 ml of ethyl acetate and conditioned with 5 ml of methanol, then washed with 2 · 5 ml of ultra-pure water. The water samples (1 l) were percolated through the cartridges with a flow rate of 5 ml min1 under vacuum pump. After extraction, the pesticides trapped in the cartridges were eluted by passing 6 ml ethyl acetate. Water was eliminated by Na2SO4(dried at 300 C) from the extracts before the solution in the glass tube was evaporated to 100 ll by gentle stream of nitrogen. The analytical procedure of OCPs residues in sediments was as follows. Firstly, 10 g homogenized sample was extracted for 30 min with ultrasonication using 60 ml dichloromethane-acetone (1:1, v/v) two times. The two extracts were combined and the activated Cu was added to remove elemental sulfur and then the extracts were dehydrated with anhydrous sodium sulfate. The extracts were concentrated to about 1–2 ml by a rotary evaporator, and further purified with a glass column (12 mm i.d.) loaded with 10 g activated Florisil. The elution was subsequently carried out using 10 ml hexane containing 10% acetone (v/v). The effluents were concentrated to 0.1 ml under a gentle stream of pure nitrogen for GC analysis. 2.3. Sample analysis The OCPs residues were analyzed with a GC (Shimadzu GC-14B, Japan) with a 63Ni ECD and a DB-5 fused silica capillary (30 m length · 0.32 mm i.d · 0.25 lm film thickness, J&W Scientific Co., Folsom, CA, USA). The column temperature was increased from 100 C to 190 C at a rate of 20 C min1, held for 1 min, and then programmed to
R. Zhou et al. / Chemosphere 68 (2007) 838–847
235 C at 4 C min1, held for 7 min. The temperature of injector and detector was 220 C and 300 C, respectively. High pure nitrogen was used for both carrier gas and make-up gas at a flow rate of 2.25 ml min1 and 35.5 ml min1, respectively, after it was filtered to remove moisture and oxygen. Samples (1 ll) were injected under splitless injection mode. The concentrations of OCPs were determined by comparing the peak height of the samples and the calibration curves of the standards. The correlation coefficient of calibration curves of OCPs were all greater than 0.998. Peak identification was conducted by the accurate retention time of each standard (±1%) and also confirmed by GC-MS (Aligent 5975). 2.4. Quality control and quality assurance The thirteen target OCP compounds included a-HCH, b-HCH, c-HCH, d-HCH, d-HCH, p,p 0 -DDT, o,p 0 -DDT, p,p 0 -DDE, p,p 0 -DDD as well as heptachlor, aldrin, heptachlor epoxide, diedrin, endrin. The standard solution of composite 13 OCPs was purchased from National Research Center of certified reference material in China. The residue levels of OCPs were quantitatively determined by the external standard method using peak height. For every set of 10 samples, a procedural blank and spiked sample consisting of all reagents was run to check for interference and cross contamination. The detection limits (DL) of OCPs were determined as the concentration of analyses in a sample that gives rise to a peak with a signal-to-noise ratio (S/N) of 3. The recoveries of OCPs were determined by the ratio of direct injection of extract to the working standards. OCPs recovery studies were undertaken to demonstrate the efficiency of the method. The percentage recovery of 13 OCPs in fish tissue varied from 68% to 115%. The detection limits of the procedure were 0.10– 0.60 ng g1. Ten grams of quartz were analyzed as blanks by the same procedure as for the samples and did not reveal any contamination. The recoveries of OCPs in the spiked sediment (100 ng of composite standard) were in the range of 87–106%. The detection limits of the procedure were 0.10–0.46 ng g1. Five separate clean water samples were spiked with the working solution including all the 13 OCPs, then extracted and analyzed in the same way as the real samples. Mean recoveries of OCPs ranged from 76% to 87% for water samples. The detection limits of the procedure were 0.08–0.16 ng l1. All relative standard deviation (RSD) was in the range of 5–10%. The above data confirmed the practicability of the analytical protocols herein in the determination of OCPs residues in the water, sediment and fish tissue. 3. Results and discussion 3.1. OCPs concentration in water and sediment Table 2 illustrated OCPs concentration in water and sediments samples in two sampling sites. Most of thirteen
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OCPs in water and sediment showed higher concentration in S2 compared with S1. S2 was located in Fuchun reservoir, where large number of farms and villages were flooded to cumulate water in 1970. A mass of OCPs had been applied in the area before the reservoir construction, which could be the severest OCPs pollution source. Moreover, natural water flow was hold back for a long time due to the man-made dam, which was not good for OCP pollutant dilution and diffusion. Lower OCPs concentration in S1 was attributed to large flux dilution effect in downstream of the river. For example, flux in S2 and S1 was in the range of 50– 350 m3 s1 and 500–750 m3 s1, respectively. Water depth in S2 and S1 varied from 23.1 to 23.3 m and from 3.57 to 3.83 m, respectively, in four seasons of 2005 according to Hangzhou hydrology record (Weng, 2005). Total OCPs concentration in sediment and water showed a decreasing trend upstream to downstream. A higher proportion of p,p 0 -DDD to p,p 0 -DDE in sediments was probably due to the presence of anaerobic conditions at the bottom of the river and higher proportion of cHCH to HCHs in sediment and water was probably due to recent application of lindane (Zhou et al., 2006). 3.2. OCPs concentration in fish samples Almost all the OCPs were detected in the fish samples. The residual levels of OCPs in fish samples from Qiantang River were shown in Table 2. Residual levels of DDTs were predominant by concentration followed by other OCPs and HCHs. Concentrations of OCPs were in the range of 8.28–143.79 ng g1 ww. The maximal level of OCPs and the highest concentrations of DDTs were found in Cynolossus abbreviaius collected from S1, which was a benthic carnivore with higher fat content (6.20%). In fish, bioconcentration from water via the gills, skin, and food is a possible route for POPs to accumulate in tissue: the route depends mainly on their feeding preference, general behavior, and trophic level (Fisher, 1995). The present study indicated the sole fish had a higher tendency to bioaccumulate OCPs than others. This may be due to its specific habitats and feeding habits. Since a large amount of matter including POPs sink at the bottom of the river by adsorption onto the particles and sediment (Shea, 1988), the bottom feeders play a significant role in the process of resuspension, during which the contaminant adsorbed on the sediment would be recycled into the water column. OCPs contained in farmland runoff can enter the river and persist for a long period; they can therefore be adsorbed in the sediment and onto suspended particulate matter, transferred into food chains, accumulated in the fatty tissues of fish, and finally reach human beings. Fig. 2a showed that carnivore fish usually have higher mean OCPs concentration (29 ng g1) than omnivorous fish (15 ng g1) and herbivorous fish (12 ng g1). It mainly attributed to DDTs biomagnification effect through food chain. DDTs are highly hydrophobic compared with HCHs and other OCPs. Once DDTs are
842
Table 2 OCPs concentrations in water (ng/l), sediment (ng/g dw) and fish species (ng g1 ww) collected from Qiantang River in China (W: water, S: sediment, A-R: fish code, see Table 1) Location
S1 (downstream)
Matrix
W
S
S2 (upstream) A
B
C
D
E
F
H
I
J
W
S
K
L
M
N
O
P
Q
R
0.10 0.43 1.53 0.44 0.32 0.47 0.51 1.38 0.37 0.27 1.73 0.48 1.94 2.50 5.53 1.94 9.97 1.60
0.10 0.67 1.40 0.35 0.18 0.20 0.25 1.28 1.24 0.50 0.47 0.14 1.50 2.52 3.39 2.37 8.28 1.50
0.42 0.41 1.48 0.37 0.40 0.20 4.25 0.93 0.50 0.50 0.33 0.19 1.75 2.68 3.20 5.85 11.73 1.80
0.12 0.53 1.97 0.45 0.15 0.83 0.79 4.96 1.11 1.40 1.74 0.99 1.64 3.07 9.33 4.28 16.7 2.00
3.75 15.4 45.8 1.34 45.1 16.8 97.7 3.72 4.28 0.5 0.65 1.62 1.64 66.2 7.63 164.3 238.2 0.83
9.63 25.3 78.6 6.72 28.1 2.13 25.11 40.1 14.16 0.16 52.82 0.77 2.12 120.2 95.8 69.66 285.6 2.11
0.11 0.46 2.75 0.73 0.08 0.52 0.15 2.70 1.67 4.35 0.54 0.94 1.24 4.05 5.42 6.77 16.24 2.10
0.10 0.33 2.36 0.10 0.55 0.75 1.36 2.00 0.50 1.29 0.40 0.70 1.20 2.89 4.30 4.45 11.64 2.80
0.15 0.11 2.49 0.38 1.01 0.18 1.24 1.50 0.60 0.18 0.30 0.55 1.10 3.13 3.45 3.21 9.79 1.90
0.17 0.19 2.05 0.79 5.76 0.38 3.36 1.70 1.98 1.00 0.34 0.60 1.00 3.20 3.64 12.48 19.32 2.40
0.21 0.56 2.68 0.63 1.47 0.16 1.12 2.30 1.55 0.80 0.46 0.80 1.60 4.09 5.16 5.10 14.35 1.90
0.10 0.75 2.33 0.40 1.11 0.12 0.73 2.69 0.46 0.60 0.54 0.94 1.78 3.58 5.95 3.02 12.55 1.60
0.10 0.10 2.65 0.33 2.30 0.45 3.30 1.00 0.24 0.80 0.20 0.35 1.10 3.18 2.65 7.09 12.92 2.30
0.22 1.61 2.98 1.04 2.79 0.37 1.92 2.60 1.58 1.00 0.52 0.94 1.12 5.85 5.18 7.66 18.69 2.40
R. Zhou et al. / Chemosphere 68 (2007) 838–847
a-HCH 7.38 0.92 0.29 0.11 0.14 0.20 0.10 0.92 b-HCH 5.58 2.86 0.30 0.81 0.55 0.44 0.28 1.20 c-HCH 12.0 9.95 1.51 1.21 3.27 1.40 1.30 1.72 d-HCH 6.92 2.38 0.49 0.42 0.91 1.27 0.18 0.22 Heptachlor 67.7 8.65 1.15 1.47 1.06 2.74 1.53 1.88 Aldrin 12.09 0.36 0.38 0.52 0.47 1.27 0.09 0.21 Heptachlor epoxide 8.14 0.43 0.83 2.43 0.23 0.20 0.14 1.82 p,p 0 -DDE 2.43 0.75 6.00 4.09 5.44 99.9 2.39 3.36 Diedrin 8.83 1.08 2.23 2.96 3.54 2.16 0.42 0.30 Endrin 0.4 0.16 0.46 0.39 0.50 0.60 1.00 0.30 p,p 0 -DDD 0.52 3.81 1.01 1.92 0.75 25.8 2.68 0.40 1.5 0.40 1.45 1.01 0.85 1.51 0.29 0.52 o,p 0 -DDT p,p 0 -DDT 3.41 1.19 2.95 8.06 7.32 6.30 5.80 1.88 P a 31.9 16.11 2.59 2.55 4.87 3.31 1.86 4.06 PHCHb DDT 7.86 6.15 11.4 15.1 14.4 133.5 11.2 6.16 P 97.2 10.7 5.05 7.77 5.80 6.97 3.18 4.51 other OCPc P OCPd 136.9 32.9 19.1 25.4 25.0 143.8 16.2 14.7 Lipid or TOC (%) 0.61 1.11 4.00 3.50 2.50 6.20 2.10 2.30 a P HCH = a-HCH + b-HCH + c-HCH + d-HCH. b P DDT = p,p 0 -DDE + p,p 0 -DDD + o,p 0 -DDT + p,p 0 -DDT. P c other OCP = Heptachlor + Aldrin + Heptachlor epoxide + Diedrin + Endrin. P P P d P OCP = HCH + DDT + other OCP.
G
R. Zhou et al. / Chemosphere 68 (2007) 838–847
OCPs, ng g-1 ww
70 60
Σ HCH
50
Σ DDT
40
Σ other OCP
30 20 10 0
carnivore
omnivorous
herbivorous
OCPs, ng g-1 ww
70 60
HCHs
50
DDTs
40
other OCPs
30 20 10 0 fish in S1
fish in S2
843
centration was significantly higher than that of HCHs (p < 0.05). With regard to the residues levels of other OCPs (aldrin, diedrin, endrin, heptachlor, heptachlor expoide), they were detected at higher level than that of HCHs, ranging from 1.94 to 12.68 ng g1 ww. Other OCPs had ever been used in small amounts in Zhejiang province and were detected in most of water, farm runoff, wet deposition and sediment samples from Qiantang River Basin (Zhou et al., 2006). The results showed that these compounds probably originated from other regional atmospheric flow transport into Qiantang River. Other OCPs such as heptachlor are still used in some developing countries around the tropical belt and may potentially move into other relatively colder regions. 3.2.1. Composition of HCHs and DDTs in fish muscles The composition of HCHs according to feeding habit was shown in Fig. 3a. It can be seen that c-HCH was the predominant HCH isomer in all species. The concentration ratio of c-HCH to HCHs was above 0.5 in all species and much higher than in the technical mixture. Although bHCH has the lowest water solubility and vapor pressure,
Fig. 2. Concentrations of OCPs in fish according to feeding habit (a) and sampling sites (b).
herbivorous
accumulated, they will be transported in the food chain. Carnivore fish are situated at the highest trophic level in all three classes of fish with higher lipid content than other fish. It was also reported that carnivore fish showed significantly higher levels of DDTs in its muscle than other freshwater fish with different feeding modes (Zhou et al., 1999; Kong et al., 2005). The results imply that the bioaccumulation of OCPs in fish is species-specific due to their ecological characteristics such as feeding habits and habitat. Fig. 2b showed the composition of three classes of OCPs in fish muscles from two sampling sites in Qiantang River. Average OCPs concentration of fish in S1 was much higher than those of fish in S2, especially for DDTs, but there were no significant difference in fish between two sites for HCHs and other OCPs. But total OCPs concentration of water and sediment in S1 was lower than that in S2. Water was calm and deep in S2 (in fact, a big reservoir), while water in S1 was rapid and shallow with complex hydrodynamic condition (near estuary), easily influenced by tide. Fish in S2 usually liked calm freshwater environment, whereas fish in S1 had good adaptability. This fact indicated that OCPs level in fish is relative to geographical position. Total HCHs concentration ranged from 1.86 for Liza haematocheila to 5.85 ng g1 ww for Erythroculter ilishaeformis in all fish species. Compared to HCHs, fish muscles showed higher levels of DDTs. Total DDTs concentration ranged from 2.65 to 132.5 ng g1 ww, much higher than HCHs. Statistical analysis (t-test) was performed to analyze difference between HCHs and DDTs. The results indicated that DDTs con-
omnivorous
carnivore
0%
20%
α-HCH
40%
β-HCH
60%
80%
γ-HCH
100%
δ-HCH
herbivorous
omnivorous
carnivore
0%
20%
p, p’-DDE
40% p, p’-DDD
60%
80%
o, p’-DDT
100% p, p’-DDT
Fig. 3. Composition of HCHs (a) and DDTs (b) in fish according to feeding habit.
R. Zhou et al. / Chemosphere 68 (2007) 838–847
3.2.2. Comparision of OCPs in fish different organs Four kind of big fishes (gurnet, leather carp, silver carp, perch) were anatomized to analyze eight organs (flesh, live and pancreas, kidney, brain, spleen, gill, heart, ovary). From Fig. 4, it can be seen that brain in silver carp (Hypophthalmichthys molitrix) had the highest OCP concentration among all fish organs in four fish species, kidney in chub having the second highest OCP concentration, followed by liver and pancreas in gurnet. This result indicated that fish muscle had lower level OCPs in a whole fish. 3.3. Relationship between lipid content and OCPs contamination in fish flesh Lipid content was assumed to be an important determinant controlling POPs accumulation in freshwater fish, since OCPs ingested by fish accumulation in lipid-rich tissue and muscle due to their lipophilic properties (Philips, 1980). Significant correlation (r = 0.86, p < 0.01) was observed between concentrations of sum DDTs (expressed in ng g1 ww) and lipid content (%) in fish species. A high positive correlation (r = 0.85, p < 0.01) was found between concen-
350 G
300
-1
and is most stable and resistant to microbial degradation, and d-HCH has the longest half-life of the HCH isomers (Willett et al., 1998), they could exist in the environment for several years or longer. (Simonich and Hites, 1995). But these two isomers were not dominant of HCHs in the fish muscles of Qiantang River. c-HCH levels were highest and a-HCH levels were lowest among HCHs in all fish muscles contrary to their technical grade composition. It was evident that the proportions of HCH isomers in the fish species did not reflect the technical mixture composition (approximately 65% a-, 10% b-, 15% c-HCH, and 10% other isomers). Considering also the persistence order of these isomers (b > c > a; Kouras et al., 1998), a relatively recent use of c-HCH (the most toxicological active HCH isomer)-lindane, (c-HCH > 99%) on Qiantang rivershores farms could be suggested as a possible explanation. The observed finding agreed with those in water and surficial sediment samples from Qiantang River (Zhou et al., 2006). The composition of DDTs according to feeding habit was shown in Fig. 3b. p,p 0 -DDE and p,p 0 -DDD accounted for 50–70% of DDTs in all fish species. Higher proportions of p,p 0 -DDE to p,p 0 -DDD suggested that DDT endured the aerobic transform in organisms. The ratio of p,p 0 -DDT to p,p 0 -DDE in herbivorous and omnivorous fish was above 1.0 and was below 1.0 in carnivorous fish. The mean ratio of p,p 0 -DDT to p,p 0 -DDE in fish from Qiantang River was less than 1, suggesting an old use of DDT in Qiantang River. But a recent scattered input of DDT in small amounts might exist in the river. Dicofol was probably the new input source, an acaricide manufactured from technical DDT, used mainly on orchard to treat mites in Zhejiang province on a small scale. Dicofol is also a replacer of market DDT, consisting of 20% DDT (Qiu et al., 2004).
OCPs, ng g ww
844
H
I
J
250 200 150 100 50 0
muscle liver
kidey brain spleen fish organs
gill
heart ovary
Fig. 4. Distribution of OCPs in fish organs from Qiantang River (G, H, I, J: fish code, see Table 1).
tration of total other OCPs and lipid content as well as between total OCPs and the lipid content (%) of the muscle (r = 0.85, p < 0.01). While a low correlation (r = 0.46, p < 0.01) was found between sum HCHs and lipid content in fish species. 3.4. Bioaccumulation of fish species Bioaccumulation of compounds in fish is the process by which chemicals are enriched in the organism relative to the water in which they reside. It is well accepted for fishes and many other animals that hydrophobic compounds preferential accumulate in lipids relative to other compartments. Accumulation of contaminants in fish lipids can occur by two routes: (1) diffusion from the water across the gills into the body and (2) transfer from the gut into the body after consumption of contaminated food. The relative importance of these routes is affected by species, locale, food web, and contaminant physical-chemical properties (Swackhamer and Hites, 1988). The bioconcentration factor, BCF, has been used to quantitatively describe bioaccumulation. It is defined as the dimensionless ratio of wet-weight contaminant concentration in fish, CF, to the water concentration, Cw. It also describes the equilibrium reached between uptake and depuration of a contaminant by fish and is the ratio of the respective rate constants for those processes (BCF = CF/ Cw). In order to eliminate lipid content influence, BCF is normalized by lipid content. Fig. 5a showed lipid normalized log BCF of HCHs, DDTs and other OCPs ranged from 3.0 to 5.4 in 18 fish species muscle, with the highest value found in Cynolossus abbreviaius (fish D). The bioconcentration of hydrophobic compounds in fish has been modeled as a simple partition process between water and lipids, which can be predicted by the octanolwater partition coefficient (Kow) (Colombo et al., 1990). The field correlation between OCPs log Kow and log BCF,
R. Zhou et al. / Chemosphere 68 (2007) 838–847
a
845
6
log BCF
5 4
Σ HCH
3
Σ DDT
2
Σ other OCP
1 0
A B C D E F G H I J K L M N O P Q R fish species
b
c 5 fish D
6
DDE
5 4 3 2 2
fish D
y = 0.53x +1.28, r=0.68
log fish/sediment BCF
log fish/water BCF
7
y =0.41x -0.56, r=0.67
4 DDE
3 2 1 0
3
4
5
log Kow
6
7
2
3
4
5 log Kow
6
7
Fig. 5. Fish/water BCF of OCPs in eighteen fish species (a), correlations between fish/water BCF and Kow (b) and correlations between fish/sediment BCF and Kow (c) for fish D from Qiantang River (A-R: fish code, see Table 1).
calculated with lipid-normalized values (ng g1 lipid) and the average water concentration (ng l1) was shown in Fig. 5b. The water BCF-Kow relationship show higher regression coefficients (r = 0.66, n = 13) in fish D and weak correlation in other fishes. Fig. 5c showed fish-sediment log BCF (ng g1 lipid, ng g1 dw, mean sediment concentration) plotted against log Kow in fish D. As expected, sediment log BCFs (0.5– 3.5) are lower than water BCFs (2.5–5.9) indicating the high affinity of sediments and lipid tissues for OCPs. DDTs are extremely hydrophobic and easily adsorbed by suspended particles which eventually settled down in the sediment. Therefore, sediment is the sink for OCPs in the aquatic system. The persistent residues may be transported across the sediment-water interface, which in turn taken up by aquatic organisms such as fish. In fish D, DDE showed an extremely higher BCF than DDT and DDD. This is probably due to its high lipid affinity in fish D (Colombo et al., 1990). DDTs compounds all have optimal physicochemical characteristics for their bioconcentration. According to partition theory, DDT should have the highest BCF followed by DDE and DDD (Chiou, 2003). Enhanced bioaccumulation of DDE has been attributed to preferential membrane transport due to a more planar configuration (Swackhamer and Hites, 1988) or due to food chain accumulation. Fish D is also benthic fish close to sediment mud. This habitat
behavior favors OCPs uptake from sediments. The fish/ sediment BCF-Kow relationship showed significant regression coefficients (r = 0.66, n = 13) in fish D and weak correlation (r = 0.12–0.48, n = 13) in other fishes. Fish/sediment BCF-Kow relationship could be useful indicators of the environmental fate of this benthic fish. The field BCF data are much complicated because the contaminant concentration may vary significantly with the time and with location and because fish are not confined to a fixed local environment. There would be large uncertainties concerning the achievement of equilibrium of contaminants between fish and water in natural systems. 4. Conclusions Among OCPs determined in the fish samples in the present study, residual levels of DDTs were predominant, followed by HCHs and other OCPs. Fish organs such as brain, kidney and liver have higher OCPs concentrations than muscle. It was indicated that carnivore fish usually have higher OCPs concentration than other fish with different feeding modes. These results imply that the bioaccumulation of OCPs in fish is species-specific due to their ecological characteristics such as feeding habit and habitat. The highest levels of c-HCH and DDTs in fish may be due to the fact that a large amount of lindane and DDTs was
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produced in the immediate previous decades in China and the usage still continues in east China. Significant correlations were observed between concentrations of sum DDTs and lipid content in fish species as well as sum OCPs and lipid content. Both water bioaccumulation factors (BCF) and sediment BCF showed a positive correlation with octanol-water partition coefficients (Kow) in the sole, while weak correlations were observed in other fish species. Acknowledgements The research was supported by the national natural science foundation of China (No. 20337010) and the natural science foundation of Zhejiang province (No. Z203111). The authors thank Dr. Kun Yang and two anonymous reviewers for their valuable suggestions. References Bayarri, S., Baldassarri, L.T., Iacovella, N., Ferrara, F., Domenico, A., 2001. PCDDs, PCDFs, PCBs and DDE in edible marine species from the Adriatic Sea. Chemosphere 43, 601–610. Bordajandi, L.R., Gomez, G., Fernandez, M.A., Fernandez, M.A., Abad, E., Rivera, J., Gonzalez, M.J., 2003. Study on PCBs, PCDD/Fs, organochlorine pesticides, heavy metals and arsenic content in freshwater fish species from the River Turia (Spain). Chemosphere 53, 163–171. Chiou, C.T., 2003. Environmental partition and concentration of organic compounds. J. Chin. Inst. Environ. Eng. 13, 1–6. Colombo, J.C., Khalll, M.F., Arnac, M., Horth, A.C., 1990. Distribution of chlorinated pesticides and individual polychlorinated biphenyls in biotic and abiotic compartments of the Rio de la Plata, Argentina. Environ. Sci. Technol. 24, 498–505. Das, B., Khan, Y.S.A., Das, P., Shaheen, S.M., 2002. Organochlorine pesticide residues in catfish, Tachysurus thalassinus (Ruppel, 1835), from the South Patches of the Bay of Bengal. Environ. Pollut. 120, 225–259. Erdogrul, O., Covaci, A., Schepens, P., 2005. Levels of organochlorine pesticides, polychlorinated biphenyls and polybrominnared diphenyl ethers in fish species from Kahramanmaras, Turkey. Environ. Int. 31, 703–711. Feng, K., Yu, B.Y., Ge, D.M., Wong, M.H., Wang, X.C., Cao, Z.H., 2003. Organo-chlorine pesticides (DDT and HCH) residues in the Taihu lake region and its movement in soil–water system I. Field survey of DDT and HCH residues in ecosystem of the region. Chemosphere 50, 683–687. Fisher, S.W., 1995. Mechanisms of bioaccumulation in aquantic systems. In: Ware, G.W. (Ed.), Rev. Environ. Contam. T. 142. Springer, New York, pp. 87–118. Fisk, AT., Hobson, KA., Norstrom, RJ., 2001. Influence of chemical and biological factors on trophic transfer of persistent organic pollutants in the Northwater polynya marine food web. Environ. Sci. Technol. 35, 732–740. Iwata, H., Tanabe, S., Sakai, N., Tatsukawa, R., 1993. Distribution of persistent organochlorines in the oceanic air and surface seawater and the role of ocean on their global transport and fate. Environ. Sci. Technol. 27, 1080–1098. Jiang, Q.T., Lee, T.K.M., Chen, K., Wong, H.L., Zheng, J.S., Giesy, J.P., Lo, K.K.W., Yamashita, N., Lam, P.K.S., 2005. Human health risk assessment of organochlorines associated with fish consumption in a coastal city in China. Environ. Pollut. 136, 155–165. Kawano, M.T., Inoue, T., Wada, H., Hidaka, H., Tatsukawa, R., 1988. Bioconcentration and residue patterns of chlordane compounds in
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Persistent chlorinated pesticides in fish species from Qiantang River in East China Rongbing Zhou, Lizhong Zhu *, Qingxia Kong Department of Environmental Science, Zhejiang University, Hangzhou, Zhejiang 310028, PR China Received 13 April 2006; received in revised form 30 December 2006; accepted 10 February 2007 Available online 8 April 2007
Abstract Thirteen organochlorine pesticides (OCPs) in 18 fish species from Qiantang River were firstly determined by GC-ECD. To elucidate the sources and the environment fate of these pollutants, water and sediment samples were also analyzed for OCPs contents. Total concentrations of OCPs in fish muscles ranged from 7.43 to 143.79 ng g1 wet weight (ww) with highest concentration recorded in sole fish (Cynoglossus abbreviatus), a benthic carnivore. The results indicated that carnivore fish have higher OCPs concentration than other fish with different feeding modes. OCPs concentration in fish was in the range of 1.86–5.85, 2.65–133.51 and 1.94–12.48 ng g1 for HCHs (a-, b-, c-, d-HCH), DDTs (p,p 0 -DDD, p,p 0 -DDE, p,p 0 -DDT, o,p 0 -DDD) and other OCPs (aldrin, diedrin, endrin, heptachlor, heptachlor expoide), respectively. The highest OCPs concentration in fish organs of four big fish species was found in brain of silver carp (Hypophthalmichthys molitrix), 289.26 ng g1 ww followed by kidney, liver, heart and gill. Among the OCPs analyzed, DDE, c-HCH and heptachlor were the predominant contaminants in fish muscle, which indicated that there was recent input of lindane. Significant correlation was observed between concentrations of DDTs and lipid content as well as between OCPs and lipid contents in fish species. Both field water bioconcentration factors (BCF) and sediment BCF showed a positive correlation with octanol-water partition coefficients (Kow) in the sole fish. 2007 Elsevier Ltd. All rights reserved. Keywords: HCH; DDT; BCF; Fish; Qiantang River
1. Introduction Organochlorine pesticides (OCPs) such as hexachlorocyclohexane (HCH) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) are ubiquitous anthropogenic environmental contaminants (Nakata et al., 1998; Willett et al., 1998) because they are persistent, broad-spectrum toxicants that tend to accumulate in the food web and have the potential to adversely affect the ecosystem and human health. Although the application of these chemicals has been banned or restricted in many countries especially the developed ones, some developing countries are still using these compounds because of their low cost and versa*
Corresponding author. Tel./fax: +86 571 88273733. E-mail addresses: [email protected] (R. Zhou), [email protected] (L. Zhu). 0045-6535/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2007.02.021
tility in industry, agriculture and public health (Tanabe et al., 1994; Sarkar et al., 1997). OCPs can enter the water environments by runoff from non-point sources, discharge of industrial wastewater, wet or dry deposition and other ways and persist for a long period. They can be transferred into food chains and finally reach human beings. Therefore, the residues of OCPs might ultimately pass onto people through consumption of drinking water, fish and agriculture food (Oehme and Mano, 1984; Kawano et al., 1988; Iwata et al., 1993). Fish is a suitable indicator for the environmental pollution monitoring because they concentrate pollutants in their tissues directly from water, but also through their diet, thus enabling the assessment of transfer of pollutants through the trophic web (Fisk et al., 2001). Data on the presence and distribution of OCPs in fish and especially edible fish species are therefore important not only from
R. Zhou et al. / Chemosphere 68 (2007) 838–847
ecological, but also human health perspective. Humans are exposed inadvertently to persistent organic pollutants (POPs) through numerous sources, of which the consumption of contaminated fish is one of the most important pathways. China is a large producer and consumer of pesticides in the world. Large amounts of OCPs were used in past decades to obtain high yield to sustain overpopulation in China. HCH and DDT were widely used in China from 1952 to 1983. The total production of technical HCH and DDT is around 4 million tons and 0.27 million tons, respectively. Even after the ban of technical HCH and DDT in 1983, 3200 tons of lindane (almost pure c-HCH) was still in use between 1991 and 2000, and DDT production also continues due to export demand and dicofol production (Zhang et al., 2002; Qiu et al., 2004; Tao et al., 2005). OCPs pollution of aquatic biota was widespread in China (Klumpp et al., 2002; Feng et al., 2003; Jiang et al., 2005; Kong et al., 2005; Nakata et al., 2005; Yang et al., 2005, 2006), neighbouring countries (Nhan et al., 2001; Das et al., 2002) and other developing countries (Nemr and Abd-Allah, 2004; Erdogrul et al., 2005) as well as developed countries (Bayarri et al., 2001; Bordajandi et al., 2003; Yamaguchi et al., 2003; Sapozhnikova et al., 2004). Qiantang River Basin has been rice and orange fields for several centuries with a populous area of 55 558 km2. Economically, tens of millions of people depend on Qiantang River as a source of fresh drinking water and fishing as source of favorite food in the local diet. All species investigated in this study are consumed by the population. Distribution of OCPs in surface water, sediment and soil in Qiantang River has been reported (Zhou et al., 2006). However, few studies have investigated the presence of
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OCPs in local aquatic biota. The objectives of this study were to (1) investigate the levels of OCPs in 18 fish species from Qiantang River; (2) compare distribution of OCPs among main organs in big fish species (>200 g); (3) study field bioaccumulation levels of OCPs in fish species. 2. Material and methods 2.1. Sample collection Qiantang River is located in the south of Yangtze Delta region of China and drains into the East Sea. Fuchun Reservoir possesses an important dam in the upstream of Qiantang River with a maximum capacity of 8740 hm3. Sampling was carried out from July to October 2005. A total of 54 individual adult fishes, representing 18 common species were obtained from local fishermen at two sites in Qiantang River (Fig. 1). One was near Hangzhou, the other was near Tonglu. Hangzhou is the capital of Zhejiang province, located downstream of Qiantang River. Tonglu is a rural area, located upstream of Qiantang River, near the dam. Surface water and sediment samples were also collected at two sites. All the sediment samples were composite samples collected from 4 to 5 points (0–20 cm) in each site using a stainless steel grab. Information on the fish length, weight, and feeding mode is given in Table 1. All the water samples were filtered through 0.45 lm fiber glass filters to remove sand and debris after returning to the laboratory and stored in the dark at temperature between 0 C and 4 C prior to extraction within two days. All the fish and sediment samples were immediately transported to the laboratory. Fish from each site consisted of 3 individual samples of the same species. Four big fish species were
Hangzhou
China
East sea
S1 Tonglu Dam
S2 Qiantang River
0
Fig. 1. Map of Qiantang River and sampling sites.
6 Km
840
R. Zhou et al. / Chemosphere 68 (2007) 838–847
Table 1 Biometric data and feeding mode of 18 fish species from Qiantang River Sampling location
Code
Common name
Species
Feeding mode
Weight (g)
Length (cm)
S1
A B C D E F G H I J
Saury Redlip mullet White fish Sole – Crucian carp Gurnet Leather carp Silver carp Perch
Coilia ectenes Jordan Liza haematocheila Erythroculter ilishaeformis Cynolossus abbreviaius Leiocassis longirostris Carassius auratus Megalobrama terminalis Cyprinus carpio Hypophthalmichthys molitrix Lateolabrax japonicus
Carnivore Omnivorous Carnivore Carnivore Carnivore Omnivorous Herbivorous Omnivorous Herbivorous Carnivore
41 36 115 96 71 41 200 1500 600 500
24 17 22 19 26 24 28 54 30 28
S2
K L M N O P Q R
– – Sheatfish – – Snake head mullet Bulltrout Bleeker
Erythroculter mongolicus Hemibarbu maculates Silurus osotus Linnaeus Acanthobrama simony Culter alburnus Odontobutis obscura Squaliobarbus curriculus Erythroculter dabryi
Carnivore Carnivore Omnivorous Omnivorous Carnivore Carnivore Herbivorous Carnivore
48 51 52 14 17 55 11 65
33 17 22 12 13 16 11 22
dissected immediately and samples were collected from different organs: gill, liver, kidney, brain, spleen, heart, ovary. All fish and sediment samples were stored in the laboratory at 20 C. All the equipment used for sample collection, transportation, and preparation were free of organochlorine contamination. All the glassware were pre-cleaned with ultra-pure water (PALL system) in an ultra-sonic cleaner (KQ-300DE, Kunshan Ultrasonic Instrument). 2.2. Extraction and clean-up procedure Fish samples were defrosted and homogenized by using a manual homogenizer. Approximately 10 g of homogenized tissues were grounded with 30 g of anhydrous sodium sulphate and extracted with 200 ml of hexane: acetone (3:1, v:v) mixture in a Soxhlet apparatus for 8 h. After concentrating the extracted solvents, lipid content was determined gravimetrically from an aliquot of the extract. The extracts were concentrated with a rotary evaporator at 40 C. For the clean up, the residue was dissolved in 1.5 ml hexane according to Manirakiza’s method (Manirakiza et al., 2002). For acid-stable pesticides, a 25 ml empty cartridge was filled with 3 g of ashed, activated and H2SO4 impregnated silica (45%, w/w) and washed with 6 ml hexane. The fat residue was loaded onto the cartridge and the elution was done with 2 · 5 ml hexane: dichloromethane (3:1, v/v) in a 25 ml conical flask. The eluates were finally reduced to 200 ll with nitrogen gas for GC injection. For non acid-stable analytes, such as diedrin and endrin, a 25 ml empty cartridge was filled successively with 2 g alumina, 2 g silica gel and 2 g Florisil (60–100 mesh, Wenzhou chemical reagent factory, China). All of them were impregnated with a 15% KOH methanolic solution (50%, v/w). Before the extract was loaded, 1 g of Na2SO4 was added at the top and the cartridge washed with 6 ml hexane. The elution was done with 2 · 5 ml fraction of hexane-
dichloromethane (3:1) in a 25 ml conical flask. The eluates were concentrated to 200 ll for GC injection. Solid phase extraction (SPE) cartridges system from Supelco was used to extract water samples according to Zhou’s method (Zhou et al., 2002). Before the extraction, the Supelco SPE cartridges (Supelclean Envi-18) were first washed with 5 ml of ethyl acetate and conditioned with 5 ml of methanol, then washed with 2 · 5 ml of ultra-pure water. The water samples (1 l) were percolated through the cartridges with a flow rate of 5 ml min1 under vacuum pump. After extraction, the pesticides trapped in the cartridges were eluted by passing 6 ml ethyl acetate. Water was eliminated by Na2SO4(dried at 300 C) from the extracts before the solution in the glass tube was evaporated to 100 ll by gentle stream of nitrogen. The analytical procedure of OCPs residues in sediments was as follows. Firstly, 10 g homogenized sample was extracted for 30 min with ultrasonication using 60 ml dichloromethane-acetone (1:1, v/v) two times. The two extracts were combined and the activated Cu was added to remove elemental sulfur and then the extracts were dehydrated with anhydrous sodium sulfate. The extracts were concentrated to about 1–2 ml by a rotary evaporator, and further purified with a glass column (12 mm i.d.) loaded with 10 g activated Florisil. The elution was subsequently carried out using 10 ml hexane containing 10% acetone (v/v). The effluents were concentrated to 0.1 ml under a gentle stream of pure nitrogen for GC analysis. 2.3. Sample analysis The OCPs residues were analyzed with a GC (Shimadzu GC-14B, Japan) with a 63Ni ECD and a DB-5 fused silica capillary (30 m length · 0.32 mm i.d · 0.25 lm film thickness, J&W Scientific Co., Folsom, CA, USA). The column temperature was increased from 100 C to 190 C at a rate of 20 C min1, held for 1 min, and then programmed to
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235 C at 4 C min1, held for 7 min. The temperature of injector and detector was 220 C and 300 C, respectively. High pure nitrogen was used for both carrier gas and make-up gas at a flow rate of 2.25 ml min1 and 35.5 ml min1, respectively, after it was filtered to remove moisture and oxygen. Samples (1 ll) were injected under splitless injection mode. The concentrations of OCPs were determined by comparing the peak height of the samples and the calibration curves of the standards. The correlation coefficient of calibration curves of OCPs were all greater than 0.998. Peak identification was conducted by the accurate retention time of each standard (±1%) and also confirmed by GC-MS (Aligent 5975). 2.4. Quality control and quality assurance The thirteen target OCP compounds included a-HCH, b-HCH, c-HCH, d-HCH, d-HCH, p,p 0 -DDT, o,p 0 -DDT, p,p 0 -DDE, p,p 0 -DDD as well as heptachlor, aldrin, heptachlor epoxide, diedrin, endrin. The standard solution of composite 13 OCPs was purchased from National Research Center of certified reference material in China. The residue levels of OCPs were quantitatively determined by the external standard method using peak height. For every set of 10 samples, a procedural blank and spiked sample consisting of all reagents was run to check for interference and cross contamination. The detection limits (DL) of OCPs were determined as the concentration of analyses in a sample that gives rise to a peak with a signal-to-noise ratio (S/N) of 3. The recoveries of OCPs were determined by the ratio of direct injection of extract to the working standards. OCPs recovery studies were undertaken to demonstrate the efficiency of the method. The percentage recovery of 13 OCPs in fish tissue varied from 68% to 115%. The detection limits of the procedure were 0.10– 0.60 ng g1. Ten grams of quartz were analyzed as blanks by the same procedure as for the samples and did not reveal any contamination. The recoveries of OCPs in the spiked sediment (100 ng of composite standard) were in the range of 87–106%. The detection limits of the procedure were 0.10–0.46 ng g1. Five separate clean water samples were spiked with the working solution including all the 13 OCPs, then extracted and analyzed in the same way as the real samples. Mean recoveries of OCPs ranged from 76% to 87% for water samples. The detection limits of the procedure were 0.08–0.16 ng l1. All relative standard deviation (RSD) was in the range of 5–10%. The above data confirmed the practicability of the analytical protocols herein in the determination of OCPs residues in the water, sediment and fish tissue. 3. Results and discussion 3.1. OCPs concentration in water and sediment Table 2 illustrated OCPs concentration in water and sediments samples in two sampling sites. Most of thirteen
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OCPs in water and sediment showed higher concentration in S2 compared with S1. S2 was located in Fuchun reservoir, where large number of farms and villages were flooded to cumulate water in 1970. A mass of OCPs had been applied in the area before the reservoir construction, which could be the severest OCPs pollution source. Moreover, natural water flow was hold back for a long time due to the man-made dam, which was not good for OCP pollutant dilution and diffusion. Lower OCPs concentration in S1 was attributed to large flux dilution effect in downstream of the river. For example, flux in S2 and S1 was in the range of 50– 350 m3 s1 and 500–750 m3 s1, respectively. Water depth in S2 and S1 varied from 23.1 to 23.3 m and from 3.57 to 3.83 m, respectively, in four seasons of 2005 according to Hangzhou hydrology record (Weng, 2005). Total OCPs concentration in sediment and water showed a decreasing trend upstream to downstream. A higher proportion of p,p 0 -DDD to p,p 0 -DDE in sediments was probably due to the presence of anaerobic conditions at the bottom of the river and higher proportion of cHCH to HCHs in sediment and water was probably due to recent application of lindane (Zhou et al., 2006). 3.2. OCPs concentration in fish samples Almost all the OCPs were detected in the fish samples. The residual levels of OCPs in fish samples from Qiantang River were shown in Table 2. Residual levels of DDTs were predominant by concentration followed by other OCPs and HCHs. Concentrations of OCPs were in the range of 8.28–143.79 ng g1 ww. The maximal level of OCPs and the highest concentrations of DDTs were found in Cynolossus abbreviaius collected from S1, which was a benthic carnivore with higher fat content (6.20%). In fish, bioconcentration from water via the gills, skin, and food is a possible route for POPs to accumulate in tissue: the route depends mainly on their feeding preference, general behavior, and trophic level (Fisher, 1995). The present study indicated the sole fish had a higher tendency to bioaccumulate OCPs than others. This may be due to its specific habitats and feeding habits. Since a large amount of matter including POPs sink at the bottom of the river by adsorption onto the particles and sediment (Shea, 1988), the bottom feeders play a significant role in the process of resuspension, during which the contaminant adsorbed on the sediment would be recycled into the water column. OCPs contained in farmland runoff can enter the river and persist for a long period; they can therefore be adsorbed in the sediment and onto suspended particulate matter, transferred into food chains, accumulated in the fatty tissues of fish, and finally reach human beings. Fig. 2a showed that carnivore fish usually have higher mean OCPs concentration (29 ng g1) than omnivorous fish (15 ng g1) and herbivorous fish (12 ng g1). It mainly attributed to DDTs biomagnification effect through food chain. DDTs are highly hydrophobic compared with HCHs and other OCPs. Once DDTs are
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Table 2 OCPs concentrations in water (ng/l), sediment (ng/g dw) and fish species (ng g1 ww) collected from Qiantang River in China (W: water, S: sediment, A-R: fish code, see Table 1) Location
S1 (downstream)
Matrix
W
S
S2 (upstream) A
B
C
D
E
F
H
I
J
W
S
K
L
M
N
O
P
Q
R
0.10 0.43 1.53 0.44 0.32 0.47 0.51 1.38 0.37 0.27 1.73 0.48 1.94 2.50 5.53 1.94 9.97 1.60
0.10 0.67 1.40 0.35 0.18 0.20 0.25 1.28 1.24 0.50 0.47 0.14 1.50 2.52 3.39 2.37 8.28 1.50
0.42 0.41 1.48 0.37 0.40 0.20 4.25 0.93 0.50 0.50 0.33 0.19 1.75 2.68 3.20 5.85 11.73 1.80
0.12 0.53 1.97 0.45 0.15 0.83 0.79 4.96 1.11 1.40 1.74 0.99 1.64 3.07 9.33 4.28 16.7 2.00
3.75 15.4 45.8 1.34 45.1 16.8 97.7 3.72 4.28 0.5 0.65 1.62 1.64 66.2 7.63 164.3 238.2 0.83
9.63 25.3 78.6 6.72 28.1 2.13 25.11 40.1 14.16 0.16 52.82 0.77 2.12 120.2 95.8 69.66 285.6 2.11
0.11 0.46 2.75 0.73 0.08 0.52 0.15 2.70 1.67 4.35 0.54 0.94 1.24 4.05 5.42 6.77 16.24 2.10
0.10 0.33 2.36 0.10 0.55 0.75 1.36 2.00 0.50 1.29 0.40 0.70 1.20 2.89 4.30 4.45 11.64 2.80
0.15 0.11 2.49 0.38 1.01 0.18 1.24 1.50 0.60 0.18 0.30 0.55 1.10 3.13 3.45 3.21 9.79 1.90
0.17 0.19 2.05 0.79 5.76 0.38 3.36 1.70 1.98 1.00 0.34 0.60 1.00 3.20 3.64 12.48 19.32 2.40
0.21 0.56 2.68 0.63 1.47 0.16 1.12 2.30 1.55 0.80 0.46 0.80 1.60 4.09 5.16 5.10 14.35 1.90
0.10 0.75 2.33 0.40 1.11 0.12 0.73 2.69 0.46 0.60 0.54 0.94 1.78 3.58 5.95 3.02 12.55 1.60
0.10 0.10 2.65 0.33 2.30 0.45 3.30 1.00 0.24 0.80 0.20 0.35 1.10 3.18 2.65 7.09 12.92 2.30
0.22 1.61 2.98 1.04 2.79 0.37 1.92 2.60 1.58 1.00 0.52 0.94 1.12 5.85 5.18 7.66 18.69 2.40
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a-HCH 7.38 0.92 0.29 0.11 0.14 0.20 0.10 0.92 b-HCH 5.58 2.86 0.30 0.81 0.55 0.44 0.28 1.20 c-HCH 12.0 9.95 1.51 1.21 3.27 1.40 1.30 1.72 d-HCH 6.92 2.38 0.49 0.42 0.91 1.27 0.18 0.22 Heptachlor 67.7 8.65 1.15 1.47 1.06 2.74 1.53 1.88 Aldrin 12.09 0.36 0.38 0.52 0.47 1.27 0.09 0.21 Heptachlor epoxide 8.14 0.43 0.83 2.43 0.23 0.20 0.14 1.82 p,p 0 -DDE 2.43 0.75 6.00 4.09 5.44 99.9 2.39 3.36 Diedrin 8.83 1.08 2.23 2.96 3.54 2.16 0.42 0.30 Endrin 0.4 0.16 0.46 0.39 0.50 0.60 1.00 0.30 p,p 0 -DDD 0.52 3.81 1.01 1.92 0.75 25.8 2.68 0.40 1.5 0.40 1.45 1.01 0.85 1.51 0.29 0.52 o,p 0 -DDT p,p 0 -DDT 3.41 1.19 2.95 8.06 7.32 6.30 5.80 1.88 P a 31.9 16.11 2.59 2.55 4.87 3.31 1.86 4.06 PHCHb DDT 7.86 6.15 11.4 15.1 14.4 133.5 11.2 6.16 P 97.2 10.7 5.05 7.77 5.80 6.97 3.18 4.51 other OCPc P OCPd 136.9 32.9 19.1 25.4 25.0 143.8 16.2 14.7 Lipid or TOC (%) 0.61 1.11 4.00 3.50 2.50 6.20 2.10 2.30 a P HCH = a-HCH + b-HCH + c-HCH + d-HCH. b P DDT = p,p 0 -DDE + p,p 0 -DDD + o,p 0 -DDT + p,p 0 -DDT. P c other OCP = Heptachlor + Aldrin + Heptachlor epoxide + Diedrin + Endrin. P P P d P OCP = HCH + DDT + other OCP.
G
R. Zhou et al. / Chemosphere 68 (2007) 838–847
OCPs, ng g-1 ww
70 60
Σ HCH
50
Σ DDT
40
Σ other OCP
30 20 10 0
carnivore
omnivorous
herbivorous
OCPs, ng g-1 ww
70 60
HCHs
50
DDTs
40
other OCPs
30 20 10 0 fish in S1
fish in S2
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centration was significantly higher than that of HCHs (p < 0.05). With regard to the residues levels of other OCPs (aldrin, diedrin, endrin, heptachlor, heptachlor expoide), they were detected at higher level than that of HCHs, ranging from 1.94 to 12.68 ng g1 ww. Other OCPs had ever been used in small amounts in Zhejiang province and were detected in most of water, farm runoff, wet deposition and sediment samples from Qiantang River Basin (Zhou et al., 2006). The results showed that these compounds probably originated from other regional atmospheric flow transport into Qiantang River. Other OCPs such as heptachlor are still used in some developing countries around the tropical belt and may potentially move into other relatively colder regions. 3.2.1. Composition of HCHs and DDTs in fish muscles The composition of HCHs according to feeding habit was shown in Fig. 3a. It can be seen that c-HCH was the predominant HCH isomer in all species. The concentration ratio of c-HCH to HCHs was above 0.5 in all species and much higher than in the technical mixture. Although bHCH has the lowest water solubility and vapor pressure,
Fig. 2. Concentrations of OCPs in fish according to feeding habit (a) and sampling sites (b).
herbivorous
accumulated, they will be transported in the food chain. Carnivore fish are situated at the highest trophic level in all three classes of fish with higher lipid content than other fish. It was also reported that carnivore fish showed significantly higher levels of DDTs in its muscle than other freshwater fish with different feeding modes (Zhou et al., 1999; Kong et al., 2005). The results imply that the bioaccumulation of OCPs in fish is species-specific due to their ecological characteristics such as feeding habits and habitat. Fig. 2b showed the composition of three classes of OCPs in fish muscles from two sampling sites in Qiantang River. Average OCPs concentration of fish in S1 was much higher than those of fish in S2, especially for DDTs, but there were no significant difference in fish between two sites for HCHs and other OCPs. But total OCPs concentration of water and sediment in S1 was lower than that in S2. Water was calm and deep in S2 (in fact, a big reservoir), while water in S1 was rapid and shallow with complex hydrodynamic condition (near estuary), easily influenced by tide. Fish in S2 usually liked calm freshwater environment, whereas fish in S1 had good adaptability. This fact indicated that OCPs level in fish is relative to geographical position. Total HCHs concentration ranged from 1.86 for Liza haematocheila to 5.85 ng g1 ww for Erythroculter ilishaeformis in all fish species. Compared to HCHs, fish muscles showed higher levels of DDTs. Total DDTs concentration ranged from 2.65 to 132.5 ng g1 ww, much higher than HCHs. Statistical analysis (t-test) was performed to analyze difference between HCHs and DDTs. The results indicated that DDTs con-
omnivorous
carnivore
0%
20%
α-HCH
40%
β-HCH
60%
80%
γ-HCH
100%
δ-HCH
herbivorous
omnivorous
carnivore
0%
20%
p, p’-DDE
40% p, p’-DDD
60%
80%
o, p’-DDT
100% p, p’-DDT
Fig. 3. Composition of HCHs (a) and DDTs (b) in fish according to feeding habit.
R. Zhou et al. / Chemosphere 68 (2007) 838–847
3.2.2. Comparision of OCPs in fish different organs Four kind of big fishes (gurnet, leather carp, silver carp, perch) were anatomized to analyze eight organs (flesh, live and pancreas, kidney, brain, spleen, gill, heart, ovary). From Fig. 4, it can be seen that brain in silver carp (Hypophthalmichthys molitrix) had the highest OCP concentration among all fish organs in four fish species, kidney in chub having the second highest OCP concentration, followed by liver and pancreas in gurnet. This result indicated that fish muscle had lower level OCPs in a whole fish. 3.3. Relationship between lipid content and OCPs contamination in fish flesh Lipid content was assumed to be an important determinant controlling POPs accumulation in freshwater fish, since OCPs ingested by fish accumulation in lipid-rich tissue and muscle due to their lipophilic properties (Philips, 1980). Significant correlation (r = 0.86, p < 0.01) was observed between concentrations of sum DDTs (expressed in ng g1 ww) and lipid content (%) in fish species. A high positive correlation (r = 0.85, p < 0.01) was found between concen-
350 G
300
-1
and is most stable and resistant to microbial degradation, and d-HCH has the longest half-life of the HCH isomers (Willett et al., 1998), they could exist in the environment for several years or longer. (Simonich and Hites, 1995). But these two isomers were not dominant of HCHs in the fish muscles of Qiantang River. c-HCH levels were highest and a-HCH levels were lowest among HCHs in all fish muscles contrary to their technical grade composition. It was evident that the proportions of HCH isomers in the fish species did not reflect the technical mixture composition (approximately 65% a-, 10% b-, 15% c-HCH, and 10% other isomers). Considering also the persistence order of these isomers (b > c > a; Kouras et al., 1998), a relatively recent use of c-HCH (the most toxicological active HCH isomer)-lindane, (c-HCH > 99%) on Qiantang rivershores farms could be suggested as a possible explanation. The observed finding agreed with those in water and surficial sediment samples from Qiantang River (Zhou et al., 2006). The composition of DDTs according to feeding habit was shown in Fig. 3b. p,p 0 -DDE and p,p 0 -DDD accounted for 50–70% of DDTs in all fish species. Higher proportions of p,p 0 -DDE to p,p 0 -DDD suggested that DDT endured the aerobic transform in organisms. The ratio of p,p 0 -DDT to p,p 0 -DDE in herbivorous and omnivorous fish was above 1.0 and was below 1.0 in carnivorous fish. The mean ratio of p,p 0 -DDT to p,p 0 -DDE in fish from Qiantang River was less than 1, suggesting an old use of DDT in Qiantang River. But a recent scattered input of DDT in small amounts might exist in the river. Dicofol was probably the new input source, an acaricide manufactured from technical DDT, used mainly on orchard to treat mites in Zhejiang province on a small scale. Dicofol is also a replacer of market DDT, consisting of 20% DDT (Qiu et al., 2004).
OCPs, ng g ww
844
H
I
J
250 200 150 100 50 0
muscle liver
kidey brain spleen fish organs
gill
heart ovary
Fig. 4. Distribution of OCPs in fish organs from Qiantang River (G, H, I, J: fish code, see Table 1).
tration of total other OCPs and lipid content as well as between total OCPs and the lipid content (%) of the muscle (r = 0.85, p < 0.01). While a low correlation (r = 0.46, p < 0.01) was found between sum HCHs and lipid content in fish species. 3.4. Bioaccumulation of fish species Bioaccumulation of compounds in fish is the process by which chemicals are enriched in the organism relative to the water in which they reside. It is well accepted for fishes and many other animals that hydrophobic compounds preferential accumulate in lipids relative to other compartments. Accumulation of contaminants in fish lipids can occur by two routes: (1) diffusion from the water across the gills into the body and (2) transfer from the gut into the body after consumption of contaminated food. The relative importance of these routes is affected by species, locale, food web, and contaminant physical-chemical properties (Swackhamer and Hites, 1988). The bioconcentration factor, BCF, has been used to quantitatively describe bioaccumulation. It is defined as the dimensionless ratio of wet-weight contaminant concentration in fish, CF, to the water concentration, Cw. It also describes the equilibrium reached between uptake and depuration of a contaminant by fish and is the ratio of the respective rate constants for those processes (BCF = CF/ Cw). In order to eliminate lipid content influence, BCF is normalized by lipid content. Fig. 5a showed lipid normalized log BCF of HCHs, DDTs and other OCPs ranged from 3.0 to 5.4 in 18 fish species muscle, with the highest value found in Cynolossus abbreviaius (fish D). The bioconcentration of hydrophobic compounds in fish has been modeled as a simple partition process between water and lipids, which can be predicted by the octanolwater partition coefficient (Kow) (Colombo et al., 1990). The field correlation between OCPs log Kow and log BCF,
R. Zhou et al. / Chemosphere 68 (2007) 838–847
a
845
6
log BCF
5 4
Σ HCH
3
Σ DDT
2
Σ other OCP
1 0
A B C D E F G H I J K L M N O P Q R fish species
b
c 5 fish D
6
DDE
5 4 3 2 2
fish D
y = 0.53x +1.28, r=0.68
log fish/sediment BCF
log fish/water BCF
7
y =0.41x -0.56, r=0.67
4 DDE
3 2 1 0
3
4
5
log Kow
6
7
2
3
4
5 log Kow
6
7
Fig. 5. Fish/water BCF of OCPs in eighteen fish species (a), correlations between fish/water BCF and Kow (b) and correlations between fish/sediment BCF and Kow (c) for fish D from Qiantang River (A-R: fish code, see Table 1).
calculated with lipid-normalized values (ng g1 lipid) and the average water concentration (ng l1) was shown in Fig. 5b. The water BCF-Kow relationship show higher regression coefficients (r = 0.66, n = 13) in fish D and weak correlation in other fishes. Fig. 5c showed fish-sediment log BCF (ng g1 lipid, ng g1 dw, mean sediment concentration) plotted against log Kow in fish D. As expected, sediment log BCFs (0.5– 3.5) are lower than water BCFs (2.5–5.9) indicating the high affinity of sediments and lipid tissues for OCPs. DDTs are extremely hydrophobic and easily adsorbed by suspended particles which eventually settled down in the sediment. Therefore, sediment is the sink for OCPs in the aquatic system. The persistent residues may be transported across the sediment-water interface, which in turn taken up by aquatic organisms such as fish. In fish D, DDE showed an extremely higher BCF than DDT and DDD. This is probably due to its high lipid affinity in fish D (Colombo et al., 1990). DDTs compounds all have optimal physicochemical characteristics for their bioconcentration. According to partition theory, DDT should have the highest BCF followed by DDE and DDD (Chiou, 2003). Enhanced bioaccumulation of DDE has been attributed to preferential membrane transport due to a more planar configuration (Swackhamer and Hites, 1988) or due to food chain accumulation. Fish D is also benthic fish close to sediment mud. This habitat
behavior favors OCPs uptake from sediments. The fish/ sediment BCF-Kow relationship showed significant regression coefficients (r = 0.66, n = 13) in fish D and weak correlation (r = 0.12–0.48, n = 13) in other fishes. Fish/sediment BCF-Kow relationship could be useful indicators of the environmental fate of this benthic fish. The field BCF data are much complicated because the contaminant concentration may vary significantly with the time and with location and because fish are not confined to a fixed local environment. There would be large uncertainties concerning the achievement of equilibrium of contaminants between fish and water in natural systems. 4. Conclusions Among OCPs determined in the fish samples in the present study, residual levels of DDTs were predominant, followed by HCHs and other OCPs. Fish organs such as brain, kidney and liver have higher OCPs concentrations than muscle. It was indicated that carnivore fish usually have higher OCPs concentration than other fish with different feeding modes. These results imply that the bioaccumulation of OCPs in fish is species-specific due to their ecological characteristics such as feeding habit and habitat. The highest levels of c-HCH and DDTs in fish may be due to the fact that a large amount of lindane and DDTs was
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