Distribution and fate of organochlorine pesticide residues
in sediments from the selected rivers in Taiwan
Ruey-An Doong
a,*, Yuh-Chang Sun
b, Pei-Ling Liao
a, Ching-Kai Peng
a,
Shian-Chee Wu
caDepartment of Nuclear Science, National Tsing Hua University, 101, Sec. 2, Kuang Fu Road, Hsinchu 30013, Taiwan, ROC bNuclear Science andTechnology Development Center, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC
cGraduate Institute of Environmental Engineering, National Taiwan University, Taipei 106, Taiwan, ROC
Received 24 April 2001; received in revised form 30 January 2002; accepted 30 January 2002
Abstract
The contamination of organochlorine pesticides (OCPs) in sediments from selected rivers in Taiwan was investigated to evaluate the pollution potentials and hazard in river sediments. Da-han River and Erh-jen River were selected as the target rivers due to their serious pollution. A total of 40 surface sediment samples were collected at five sampling stations along the rivers. Results showed that the concentrations of various pesticides in sediments were in the range of
0.57–14.1 ng/g forPHCH, 0.05–0.15 ng/g for aldrin, 0.12–5.8 ng/g for dieldrin, 0.22–0.64 for endrin, 0.24–6.37 ng/g for
endosulfan and 0.21–8.81 ng/g forPDDT (p; p0-DDD, p; p0-DDE, p; p0-DDT). Among the OCPs,PHCH, endosulfan
andPDDT were the most dominant compounds in the river sediments. Endosulfan sulfate was the most frequent
detected compound in the sediments from the selected rivers. Also,PDDT, dieldrin and b-HCH were in abundance.
Different contamination patterns between the selected river sediments were also observed. Da-han River was mainly
contaminated with endosulfan sulfate andPDDT. Whereas the main pesticides in Erh-jen River were b-HCH and
P
DDT. Among the cyclodiene compounds, dieldrin was in abundance in most of the sediments. Moreover, the fre-quencies of detection of the metabolites were higher than those of parent compounds, depicting that the sediments have contaminated for a long time. The results obtained in this study showed that there still exist a variety of OCPresidues in
the river sediments in Taiwan. Ó 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Organochlorine pesticides; Surface sediment; HCH; DDT; Distribution
1. Introduction
Organochlorine pesticides (OCPs) are known for their environmental persistence and global concerns. Residues of OCPs continue to detect in many areas. Owing to their high capacities for bioaccumulation and toxicities in organisms, these compounds pose threats to ecosys-tems and human health. Since these compounds have an
affinity for particulate matters, one of their major sinks is thought to be the river and marine sediments. Therefore, the investigation of distribution of OCPs in sediments can provide a valuable record of contamina-tion in the aquatic environments.
The input pathways of OCPs into the river environ-ments include discharge of domestic sewage and indus-trial wastewater, runoff from nonpoint sources, and direct dumping of wastes into the river. Although sedi-ments do not constitute a direct measure of the degree of aquatic pollution, they offer an irreplaceable aid in re-constructing the historical inputs of OCPs based on profile descriptions of contamination in core samples
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Corresponding author. Tel.: 5726785; fax: +886-3-5718649.
E-mail address: radoong@mx.nthu.edu.tw (R.-A. Doong).
0045-6535/02/$ - see front matterÓ 2002 Elsevier Science Ltd. All rights reserved. P II: S 0 0 4 5 - 6 5 3 5 ( 0 2 ) 0 0 0 6 6 - 8
(Hendy and Peake, 1996). The distribution of various contaminants in sediments depends largely on the physico-chemical properties of the ecosystem, the partition coef-ficients of individual contaminants, the organic contents, and microflora activities (Pavoni et al., 1987; Brook and Moore, 1988; McKenzie-Smith et al., 1994; Glynn et al., 1995). Although the residue levels of the chlorinated compounds in the environments have considerably de-clined in the past 20 years, recent work has depicted that chlorinated pesticides could be detected in the range of 0.03–25.17 ng/g dry weight (d.w.) in marine and river sediments (Gold-Bouchot et al., 1995; Sarkar et al., 1997). Moreover, some OCPs, such as DDT, HCH and endosulfan are still used in some countries around the tropical and subtropical belts for agricultural and me-dicinal purposes. These compounds can be deposited into the sediments through long-range atmospheric transport (LRT), resulting in a high exposure to OCPs in the areas near the pollution sources.
Taiwan has a strong agricultural sector, which has made wide use of pesticides. The OCPs were employed extensively in the early 1950s for the control of soil-dwelling insects and have been officially banned since
1974. It is estimated that 2:5 107 kg of OCPs was
re-leased into the environments annually from the 1950s to 1970s and constituted a long-term source of conta-mination to aquatic ecosystem via soil erosion and agri-cultural runoff. A variety of OCPresidues in foods from Hsinchu, Taiwan were also detected in the range of 0.26–10.22 ng/g wet weight (Doong and Lee, 1999). However, there is little information of the contamina-tion of sediments in Taiwan rivers.
The purpose of this study was to determine the contamination level of OCPs in sediments from selected rivers to evaluate the pollution potentials and hazard of river sediments in Taiwan. Two different rivers, Da-han River and Erh-jen River were selected as the target rivers for studies in northern and southern Taiwan, respec-tively.
2. Methods and materials 2.1. Study area and sampling
The Da-han River, one of the important rivers in
northern Taiwan, has a catchment basin of 1163 km2
and a total length of 135 km. The Da-han River is a traditional agricultural production site which has small scale farms producing grains. Also, this river is a main source for water supply in northern Taiwan and receives massive discharge of domestic sewage from the urban-ized areas in its catchment basin. The Erh-jen River, a representative polluted river in southern Taiwan, has a
catchment area of 350 km2and a total length of 65 km.
The river water is highly polluted with heavy metals and dioxin from the industrial discharge.
A total of 40 sediment samples were collected from these two rivers from October 1997 to April 1998. Five sampling stations along each river were selected and four samples from each station were collected. The lo-cations of these sampling stations in the selected rivers are shown in Fig. 1. The distances of sampling sites from the outlets of the selected rivers were 19.3, 22.9, 23.6, 27.2 and 41.2 km for Da-han River and 1.2, 6.3, 17.9, 24.6, and 30.1 km for Erh-jen River. Water depths of the stations ranged from 0.4 to 6.7 m. The upper 15 cm of the surface sediments were sampled from the sam-pling sites using a boat with a Birge–Ekman sediment grabber in areas of low flow velocity (<0.3 m/s). Im-mediately after collection, sediments were preserved in deep freeze in order to avoid degradation.
2.2. Extraction andcleanup
Homogenized subsamples were freeze-dried and OCPs were extracted with Soxhlet apparatus. A 10 g sediment was placed into a thimble filter and OCPres-idues in sediments were extracted with 250 ml hexane for 24 h at a rate of 10–12 cycles/h. The extract was then preconcentrated to 2–3 ml on a rotary evaporator. The extract was further treated with activated copper powder to remove sulfur compounds. A 2 g Florisil SPE car-tridge was used to cleanup the extracts. Sodium sulfate (ca. 1.0 cm) was added to a Florisil SPE cartridge. The cartridge was washed with 6 ml petroleum ether–ethyl
ether (95þ 5) at a rate of 5 ml/min and then the
orga-nochlorine pesticides were eluted with 12 ml petroleum
ether–ethyl ether (95þ 5) at a rate of 2 ml/min. The
elutes were concentrated to about 1–2 ml on a rotary evaporator and then transferred to 10 ml glass tubes with small amounts of hexane. The solvent in the glass tube was entirely evaporated under a gentle stream of nitrogen and the precipitates were redissolved in 1 ml hexane and analyzed with a gas chromatography (GC)– electron capture detector (ECD) system.
2.3. Analytical procedures
The concentrations of OCPs in the extracts were monitored with GC equipped with an ECD and a PTE-5
fused silica capillary column (30 m length 0:32 mm
inner diameter 0:25 lm film thickness, Supelco Inc.,
Co., Bellefonte, PA.). One ll of each sample was injected into the GC system for separating the OCPs. Column
temperature increased from 140 to 200°C at 15 °C/min,
held for 2 min, and then programmed to 250°C at 2 °C/
min, held for 2 min. The temperatures of injector and
detector were 250 and 300°C, respectively. Nitrogen gas
1.73 ml/min (linear velocity, 25.2 cm/s) and 35.5 ml/min, respectively. Pentachloronitrobenzene and decachloro-biphenyl were used as the internal standards. Also, identified peaks were checked by GC–ECD with
SPB-608 fused silica capillary column (30 m length 0:53
mm inner diameter 0:5 lm film thickness, Supelco
Inc., Co., Bellefonte, PA). The residues of OCPs were determined by comparing the peak areas of the samples and the calibration curves of the standards. The
corre-lation coefficientsðRÞ of calibration curves of OCPs were
all greater than 0.998.
Oxidation–reduction potential (ORP), volatile sus-pended solid (VSS), total organic carbon (TOC), water content and particle size distribution of sediments were also analyzed. ORPwas determined with an Orion EA 920 expandable ion analyzer (Orion Research Inc., Boston., MA.) by using an Orion model 97-78-00 Pt re-dox electrode. The values were expressed in terms of the ORPs of the samples relative to the Pt redox electrode and were read out until the potential changed was less than 0.5 mV/min. Water content and VSS were
deter-mined by the weight loss at 103 2 °C and 550 50 °C,
respectively. Moreover, ampule TOC concentrations of sediment particles were obtained by a model 700 TOC analyzer using wet oxidation method (O.I. Corporation, Texas).
2.4. Quality assurance
For every set of 10 samples, a procedural blank and spike sample consisting of all reagents was run to check for interference and cross contamination. The method detection limits (MDLs) of OCPs were determined as the concentrations of analytes in a sample that gives rise to
a peak with a signal-to-noise ratioðS=NÞ of 3. The OCP
recoveries were determined relative to the ratio of direct injection of extract and the working standards prepared in hexane. Also, the quality of the analytical data was assured using the CRM 804-050 soil standard. Table 1 il-lustrates the recoveries and MDLs of OCPs. The recov-eries and MDLs of OCPs ranged from 69.5% to 129.4% and 0.05–0.35 ng/g dry sediment, respectively. More-over, the average analyzed concentrations of OCPs in CRM sample were in the range of 19.2–1989.8 mg/kg, which corresponding to the recoveries of 84–130%.
3. Results and discussion 3.1. Characteristics of sediments
Table 2 illustrates the basic physico-chemical pa-rameters of sediments collected from Da-han and Erh-jen Rivers. These parameters included ORP, VSS, TOC, water content and particle size distribution. The
char-acteristics of sediments were site-depended. The ORP
values ranged from 184 to372 mV and from 59 to
269 mV for Da-han and Erh-jen Rivers, respectively. These measured OPR values reflect that the collected sediments were mainly under anaerobic conditions (Parsons and Barrio-Lage, 1985). The distributions of particle sizes in sediments from Da-han and Erh-jen Rivers were also different. The particle sizes in Da-han River ranged mainly from 180 to 300 lm, while small-size particles (8–37 lm) were dominant in Erh-jen River. Also, the TOC contents of sediments ranged from 0.51 to 7.86 mg C/g and from 1.78 to 45.21 mg C/g for Da-han River, and Erh-jen River, respectively. It is clear that Erh-jen River was composed of fine particles and had high organic contents in the sediments. This ob-servation is consistent with other studies, which dem-onstrated that fine particles can retain large amounts of organic compounds and pose a high pollution potency (Sarkar et al., 1997). Moreover, the VSS contents of the sediments ranged from 1.07% to 2.5% and from 0.71% to 3.0% for Da-han and Erh-jen Rivers, respectively. A
positive correlation (r2¼ 0:692) between VSS and TOC
in sediments was established, depicting that the sediment was contaminated with organic compounds (Fig. 2). 3.2. Concentration profiles of OCPs
Tables 3 and 4 illustrate the concentrations of OCP residues in surface sediments from Da-han and Erh-jen Rivers, respectively. Concentrations of OCPs in sedi-ments from Da-han River were <0.12–4.94 ng/g d.w. for P
HCH, <0.05–0.15 ng/g d.w. for aldrin, <0.12–5.8 ng/g d.w. for dieldrin, <0.08–3.78 ng/g d.w. for endosulfan,
Table 1
The recoveries, MDLs, and the analyzed results of CRM standards (840-050) of OCPs in sediments
Pesticides Recovery (%) MDLs (ng/g dry weight) CRM standard (mg/kg)
Certified value Analyzed value
a-HCH 85.0 0.12 –a – b-HCH 94.4 0.35 – – c-HCH 83.1 0.25 491.4 470.6 d-HCH 99.9 0.11 – – Heptachlor 92.0 0.15 – – Aldrin 92.2 0.05 18.04 19.18 Heptachlor epoxide 96.9 0.15 – – Endosulfan I 90.1 0.08 1464.3 1232.6 p; p0-DDE 88.6 0.12 1519.6 1269.6 Dieldrin 98.9 0.12 1862.5 1693.9 Endrin 121.1 0.22 62.15 67.7 Endosulfan II 96.2 0.16 1128.2 1284.3 p; p0-DDD 117.7 0.18 1530.6 1989.8 Endosulfan sulfate 85.2 0.13 – – p; p0-DDT 116.4 0.18 1060.1 1067.7 Endrin ketone 69.5 0.13 – – Methoxychlor 129.4 0.30 – – a Not available.
<0.18–2.64 ng/g d.w. for p; p0-DDT and <0.3–2.85 ng/g d.w. for methoxychlor. Several biological metabolites of the parent OCPs were also detected. The concentrations were 0.32–2.39 ng/g d.w. for endrin aldehyde, 0.62–3.18 ng/g d.w. for endosulfan sulfate, 0.51–3.89 ng/g d.w. for
p; p0-DDE and 0.56–3.34 ng/g d.w. for p; p0-DDD.
Concentrations of OCPresidues in sediments from Erh-jen River were higher than those from Da-han River. As illustrated in Table 4, concentrations of OCPs ranged from <0.35 to 14.1 ng/g d.w. for b-HCH, <0.12 to 1.29 ng/g d.w. for dieldrin, <0.08 to 6.27 ng/g d.w. for
endosulfan, <0.12 to 1.69 ng/g d.w. for p; p0-DDE,
<0.18 to 3.9 ng/g d.w. for p; p0-DDD, <0.18 to 5.57 ng/g
d.w. for p; p0-DDT and <0.3 to 7.39 ng/g d.w. for
methoxychlor. This may be due to the high organic con-tents of the sediment particles in Erh-jen River. Several studies have depicted that the contamination of hydro-phobic organic compounds in sediments is dependent on the chemical properties of the ecosystem, the partition coefficients of individual compounds and the organic
contents of sediment particles (McKenzie-Smith et al., 1994; Glynn et al., 1995). A similar distribution pattern of OCPs in sediments from the selected rivers was ob-tained when the concentrations of OCPresidues were normalized to TOC contents. Table 5 illustrates the con-centration ranges, medians and mean values of OCPs in the selected rivers based on TOC concentrations. The total OCPresidues in sediments from Da-han River ranged from 0.21 to 7.42 lg/g TOC with the mean value
of 2.34 lg/g TOC. Also, PHCH, Pcyclodiene and
P
DDT concentrations ranged from ND to 2.08, from ND to 4.51 and from 0.06 to 2.91 lg/g TOC, respec-tively. The normalized OCPconcentrations in sediments collected from Erh-jen River was only slightly higher
than that from Da-han River. The measured PHCH
ranged from ND to 3.47 lg/g TOC with the mean value of 1.03 lg/g TOC. Although this value is 2-fold higher than that in Da-han River, the concentration ranges
and mean values ofPDDT andPcyclodiene obtained
from Erh-jen River were similar to those from Da-han River. Also, the total concentrations of OCPs in Erh-jen River ranged from 0.08 to 8.20 lg/g TOC with the mean concentration of 2.67 lg/g TOC, which is similar to that in Da-han River. This result reflects that the contamination of OCPs in sediments from the selected rivers in Taiwan may be partly from the same pollution sources.
Fig. 3 illustrates the detection frequencies of OCPs in sediments collected from the selected rivers. Among the OCPs detected in Da-han River, endosulfan sulfate was the most frequent found compound in sediment (60%),
followed by p; p0-DDE (55%) and dieldrin (55%). Also,
high detection frequencies of p; p0-DDD and p; p0-DDT
were demonstrated. This result shows that DDTs were the most dominant compounds in the sediments from Da-han River. Similar to the results in Da-han River,
high detection frequencies of b-HCH, p; p0-DDD,
endo-sulfan sulfate and p; p0-DDE were observed in
sedi-ments from Erh-jen River. The detection frequencies
Table 2
The physicochemical properties of surface sediments collected from the selected rivers in Taiwan Sampling stations Water depth (m) ORPvalue (mV) VSS (%) Water content (%)
TOC (mg C/g) Particle size distribution (lm) DH-1 3.2–6.7 (184)–(184) 1.56–2.50 33.2–47.1 4.72–7.88 8–37 DH-2 1.9–4.0 (181)–(220) 1.52–1.82 26.2–31.9 1.76–5.32 37–300 DH-3 0.9–2.2 (18)–(112) 1.35–1.57 24.9–27.0 1.62–3.23 180–300 DH-4 2.0–4.5 (172)–(372) 1.36–2.44 23.9–51.9 1.49–5.98 8–300 DH-5 1.9–6.5 (225)–(290) 1.07–1.59 26.2–30.3 0.51–5.21 105–300 EJ-1 0.4–1.0 (59)–(185) 1.29–1.94 26.2–35.7 2.82–6.94 8–37 EJ-2 0.6–1.8 (105)–(234) 1.34–1.79 23.1–47.1 1.78–5.78 8–37 EJ-3 0.5–3.0 (234)–(255) 0.49–1.89 25.4–39.6 1.79–3.59 8–180 EJ-4 1.8–2.1 (255)–(269) 0.71–2.71 47.9–50.3 2.2–11.15 4–180 EJ-5 2.5–3.7 (179)–(269) 0.82–3.0 30.3–72.7 9.03–45.21 2–37 *
Five sampling stations along each river were selected and four samples from each station were collected.
Fig. 2. The relationship between ampule TOC (mg C/g) and VSS (%) in sediments collected from the selected rivers.
Table 3
Concentrations of OCPresidues in surface sediment of the Da-han River Sample OCPs (ng/g of dry sediment)a
a-BHC b-BHC Hept. Hept. epoxide
Aldrin Diel-drin
Endrin Endo. I Endo. II Endo. sulfate Endrin alde-hyde Endrin ketone DDE DDD DDT Meth-oxy. P OCP DH-101 1.96 <0.35 <0.15 <0.05 0.4 <0.22 <0.15 <0.08 <0.16 <0.13 <0.06 <0.13 1.33 0.69 0.75 <0.3 5.13 DH-201 3.74 <0.35 <0.15 0.08 <0.12 <0.22 <0.15 <0.08 <0.16 <0.13 0.32 <0.13 <0.12 <0.18 1.03 <0.3 5.17 DH-301 1.31 <0.35 <0.15 <0.05 <0.12 <0.22 <0.15 <0.08 0.18 <0.13 <0.06 <0.13 <0.12 <0.18 0.21 <0.3 1.7 DH-401 4.32 <0.35 <0.15 <0.05 0.29 <0.22 <0.15 2.41 1.36 2.21 <0.06 <0.13 1.5 <0.18 1.76 <0.3 13.85 DH-501 <0.12 <0.35 <0.15 <0.05 3.16 <0.22 <0.15 <0.08 <0.16 0.88 <0.06 <0.13 <0.12 <0.18 0.32 <0.3 4.36 DH-102 4.55 0.39 <0.15 0.15 5.8 <0.22 <0.15 <0.08 <0.16 <0.13 <0.06 <0.13 3.89 <0.18 <0.18 <0.3 14.78 DH-202 <0.12 <0.35 <0.15 <0.05 0.18 <0.22 <0.15 <0.08 0.03 <0.13 <0.06 <0.13 2.29 <0.18 0.83 <0.3 3.33 DH-302 <0.12 <0.35 <0.15 <0.05 <0.12 <0.22 <0.15 <0.08 <0.16 <0.13 <0.06 <0.13 <0.12 <0.18 0.47 <0.3 0.47 DH-402 <0.12 <0.35 <0.15 <0.05 0.89 <0.22 <0.15 <0.08 <0.16 <0.13 <0.06 <0.13 0.46 <0.18 <0.18 <0.3 1.35 DH-502 <0.12 <0.35 <0.15 <0.05 <0.12 <0.22 <0.15 <0.08 <0.16 <0.13 <0.06 <0.13 <0.12 <0.18 <0.18 0.2 0.2 DH-103 <0.12 <0.35 <0.15 <0.05 0.82 <0.22 <0.15 0.69 <0.16 0.8 <0.06 <0.13 0.51 0.56 <0.18 0.52 3.9 DH-203 0.73 <0.35 0.58 <0.05 <0.12 <0.22 <0.15 0.71 <0.16 0.62 <0.06 <0.13 1.52 <0.18 <0.18 <0.3 4.16 DH-303 <0.12 <0.35 <0.15 <0.05 <0.12 0.56 <0.15 <0.08 0.51 2.27 0.68 <0.13 <0.12 1.5 1.57 0.76 7.85 DH-403 <0.12 <0.35 1.15 <0.05 <0.12 <0.22 <0.15 <0.08 <0.16 3.18 2.39 <0.13 <0.12 1.36 2.26 0.72 11.06 DH-503 1.44 1.08 0.54 <0.05 <0.12 <0.22 <0.15 <0.08 <0.16 2.03 <0.06 <0.13 <0.12 3.34 <0.18 <0.3 8.43 DH-104 <0.12 <0.35 1.23 <0.05 0.8 <0.22 <0.15 1.08 0.62 0.89 0.66 0.57 0.72 1.07 <0.18 <0.3 7.64 DH-204 <0.12 <0.35 <0.15 <0.05 <0.12 <0.22 <0.15 1.54 0.85 2.16 <0.06 <0.13 0.63 0.91 <0.18 <0.3 6.09 DH-304 <0.12 0.73 0.63 <0.05 0.59 <0.22 <0.15 <0.08 <0.16 1.67 0.56 <0.13 <0.12 0.64 <0.18 <0.3 4.82 DH-404 1.9 <0.35 1.57 <0.05 0.72 <0.22 <0.15 <0.08 <0.16 2.66 1.07 <0.13 1.22 1.65 2.64 <0.3 13.43 DH-504 <0.12 0.67 <0.15 <0.05 0.52 <0.22 <0.15 0.57 <0.16 1.38 0.89 1.34 0.71 1.41 <0.18 2.85 10.34
aHept.: heptachlor; Endo.: endosulfan, Methoxy.: methoxychlor.
R.-A. Doong et al. / Chemosph ere 48 (2002) 237–246
Concentrations of OCPresidues in surface sediment of the Erh-jen River Sample OCPs (ng/g of dry sediment)a
a-BHC b-BHC Hept. Hept. epoxide
Aldrin Diel-drin
Endrin Endo. I Endo. II Endo. sulfate Endrin alde-hyde Endrin ketone DDE DDD DDT Meth-oxy. P OCP EJ-101 <0.12 0.57 <0.15 <0.24 <0.05 <0.12 <0.22 <0.08 <0.16 <0.13 <0.06 <0.13 <0.12 <0.18 <0.18 <0.3 0.57 EJ-201 <0.12 <0.35 <0.15 <0.24 <0.05 <0.12 <0.22 <0.08 <0.16 <0.13 0.89 <0.13 <0.12 <0.18 2.35 <0.3 3.24 EJ-301 <0.12 0.53 <0.15 <0.24 <0.05 <0.2 <0.22 <0.08 <0.16 <0.13 <0.06 <0.13 <0.12 <0.18 0.09 0.57 1.19 EJ-401 <0.12 5.35 <0.15 <0.24 <0.05 <0.12 <0.22 <0.08 <0.16 1.27 <0.06 <0.13 <0.12 <0.18 <0.18 <0.3 6.62 EJ-501 <0.12 2.27 <0.15 <0.24 <0.05 1.29 <0.22 <0.08 <0.16 <0.13 <0.06 <0.13 0.38 <0.18 0.57 <0.3 4.51 EJ-102 0.97 5.93 <0.15 <0.24 <0.24 <0.12 0.64 <0.08 <0.16 <0.13 <0.06 <0.13 0.28 <0.18 1.44 <0.3 9.26 EJ-202 <0.12 2.61 <0.15 <0.24 <0.05 <0.12 0.23 0.63 <0.16 0.21 <0.06 <0.13 <0.12 0.25 0.3 <0.3 4.23 EJ-302 <0.12 5.09 <0.15 <0.24 <0.05 <0.12 <0.22 0.5 <0.16 <0.13 0.02 <0.13 <0.12 2.28 0.71 <0.3 8.60 EJ-402 <0.12 7.15 <0.15 <0.24 <0.05 0.17 <0.22 0.39 2.12 <0.13 <0.06 <0.13 0.4 0.45 0.29 <0.3 10.97 EJ-502 <0.12 14.1 5.61 <0.24 <0.05 <0.12 <0.22 1.71 0.71 <0.13 0.2 <0.13 <0.2 0.26 1.08 <0.3 23.67 EJ-103 1.17 3.77 0.64 <0.24 <0.05 <0.12 <0.22 2.12 <0.16 1.25 0.64 1.77 0.66 2.7 <0.18 0.74 15.46 EJ-203 <0.12 <0.35 <0.15 <0.24 <0.05 <0.12 <0.22 <0.08 <0.16 0.96 <0.06 <0.13 <0.12 0.75 <0.18 1.14 2.85 EJ-303 0.84 4.4 0.51 <0.24 <0.05 0.58 <0.22 2.3 <0.16 0.72 1.99 1.02 0.75 3.9 <0.18 1.23 18.24 EJ-403 1.11 3.1 0.95 <0.24 <0.05 0.53 <0.22 <0.08 <0.16 1.58 <0.06 <0.13 1.69 1.55 5.57 <0.3 16.08 EJ-503 1.5 <0.35 0.6 <0.24 <0.05 0.77 <0.22 3.26 3.01 0.89 1.42 <0.13 1.39 1.09 <0.18 <0.3 13.93 EJ-104 1.36 1.63 <0.15 <0.24 <0.05 1.09 <0.22 1.07 0.93 1.12 0.61 <0.13 0.65 1.14 <0.18 1.71 11.31 EJ-204 1.37 1.48 <0.15 <0.24 <0.05 0.98 <0.22 0.52 <0.16 1.52 <0.06 1.76 0.86 3.49 <0.18 7.39 19.37 EJ-304 1.2 5.02 <0.15 <0.24 <0.05 0.58 <0.22 1.13 <0.16 0.6 <0.06 <0.13 0.67 1.9 1 <0.3 12.1 EJ-404 1.29 2.83 0.65 <0.24 <0.05 <0.12 <0.22 <0.08 <0.16 1.72 <0.06 <0.13 1.1 1.66 1.04 0.71 11 EJ-504 1.18 <0.35 <0.15 <0.24 <0.05 <0.12 <0.22 1.09 <0.16 0.37 0.66 0.61 0.78 <0.18 <0.18 <0.3 4.69
aHept.: heptachlor; Endo.: endosulfan, Methoxy.: methoxychlor.
R.-A. Doong et al. / Chemosphere 48 (2002) 237–246 243
were 80%, 65%, 60% and 60%, respectively. These results clearly show that DDTs and HCHs were the main OCPs used in Taiwan.
3.3. Characteristics of OCP contamination in sediments The relative concentrations of the parent DDT compound and its metabolites can provide useful
in-formation on the pollution source. The compound p; p0
-DDT is the active ingredient of the -DDT pesticides and typically makes up approximately 80% of the technical formulation (Bopp et al., 1982; Hendy and Peake, 1996).
Fig. 4 illustrates the ratios of DDD/DDE andðDDE þ
DDDÞ=PDDT in the sediments from Da-han and
Erh-jen Rivers. Ratios of ðDDE þ DDDÞ=PDDT in
sedi-ments ranged from 0.37 to 1.0. Since ratio ofðDDE þ
DDDÞ=PDDT > 0:5 is reported to be subjected to
long-term weathering (Hites and Day, 1992), results obtained in this study indicate that the DDT compounds in sediments may be mainly derived from DDT-treated aged and weathered agricultural soils. Also, the ratios of DDD/DDE ranged from 0.24 to 1.99 and from 0.78 to
5.20 for Da-han and Erh-jen Rivers, respectively. Most of the ratios are greater than unity. This means that the total DDT found in sediments from the selected rivers is
dominated by p; p0-DDD, the product of anaerobic
de-gradation of p; p0-DDT. This result is consistent with the
measured ORPvalues (372 to 184 mV), suggesting that the input of DDT compounds to the rivers was via the weathered agricultural soils and was retained under anaerobic conditions within the sediment in Taiwan rivers.
The frequency of detection of HCH compounds in environmental samples showed that the contamination of HCH was also widespread in Taiwan rivers. Recent studies also show that the contamination of HCH iso-mers is a serious problem worldwide (Fellin et al., 1996; Sarkar et al., 1997; Hong et al., 1999; Walker et al., 1999). HCH pesticide is an inexpensive insecticide and had been used for agricultural purpose to control the insects in fruit, grain and vegetable crops in Taiwan since 1950s. Technical-grade HCH consists principally of five isomers, a-HCH (60–70%), b-HCH (5–12%), c-HCH (10–15%), d-c-HCH (6–10%) and e-c-HCH (3–4%) (Walker et al., 1999). The most often found isomers in the environment are a-, b- and c-isomers. a-HCH was found to be the dominant compound of HCH in the
Table 5
Concentration ranges, medians and mean values of OCPresidues in surface sediments collected from Da-han and Erh-jen Rivers OCPs Da-han river (lg/g TOC) Erh-jen River (lg/g TOC)
Range Median Mean Range Median Mean POCP0.21–7.42 1.73 2.34 0.08–8.20 2.03 2.67 PHCH ND–2.08 0.13 0.39 ND–3.47 0.70 1.03 PCyclodiene ND–4.51 0.87 1.05 ND–5.8 0.53 0.92 P DDT 0.06–2.91 0.43 0.90 ND–2.03 0.50 0.72 ND: not detected.
Fig. 4. The relationship between DDD/DDE and ðDDE þ DDDÞ=PDDT in sediments from Da-han and Erh-jen Rivers. Fig. 3. The detection frequencies of OCPs in the sediments
collected from Da-han and Erh-jen Rivers, Taiwan. The results are the means of the OCPs from the five sampling stations and four sampling times in each river.
sediments from Da-han River. Since the catchment of Da-han River is a heavily urbanized area, the contami-nation of a-HCH may be attributed to the long distance transport from other areas. Some OCPs such as endo-sulfan, heptachlor and HCH are still used in some de-veloping countries around the tropical belt and may be transported through the atmosphere and gradually de-posit in the river at higher latitudes. Oehme et al. (1996) measured the seasonal concentration changes of orga-nochlorines in the European Arctic and found that long-range atmospheric transport from more polluted areas might lead to a significant concentration change in the Arctic air. It is estimated that the total global usage of technical grade HCH between 1948 and 1997 was around 10 million tons (Li, 1999). Recently, consider-able unused stockpiles of technical-grade HCH was found in dump sites in Africa and Near East (FAO, 1998). Some of the containers have damaged and are leaking. Among the HCH isomers, a-HCH is more likely to partition to the air and transport for a long distance. A study conducted in India examining the flux of HCH also indicated that most of the HCH applied annually was lost to the atmosphere (Takeoka et al., 1991). These results depict that a-HCH may be mainly from the long-range transport (LRT). Since a-HCH exhibits the most carcinogenic activity among HCH isomers, the contamination levels detected may pose a high ecotoxicity for aquatic organisms.
Different HCH contamination patterns for Erh-jen River were observed. The detection frequencies of a- and b-HCH were 50% and 80%, respectively. The similar detection frequency of a-HCH in the selected rivers shows that the LRT may be the major source of a-HCH in Erh-jen River. Unlike the a-HCH, b-HCH is more lipophilic and is the predominant isomer in soils and animal tissue and fluids (Willett et al., 1998). Also, b-HCH is resistant to hydrolysis and environmental de-gradation. Since Erh-jen River is a strong agricultural sector in southern Taiwan, the abundance of the b-HCH may be attributed to the weathered soils, which is
also consistent with the results ofPDDT.
4. Conclusions
The results obtained in this study documents the first known analysis of OCPdistributions in sediments col-lected from Da-han and Erh-jen Rivers, Taiwan. There still exist a variety of OCPresidues in the river sediments in Taiwan. The total concentrations of OCPs in sedi-ments ranged from 0.2 to 14.8 and 0.6 to 29.5 ng/g dry weight for Da-han and Erh-jen Rivers, respectively, which corresponds to 0.21–7.42 and 0.08–8.20 lg/g TOC when normalized to TOC concentrations. DDTs and HCHs were the dominant OCPs in sediments from the
selected rivers. Da-han River was mainly contaminated
with a-HCH and p; p0-DDE, while the main pesticide
residues in Erh-jen River were b-HCH and p; p0-DDD.
The detection frequencies of the metabolites were higher than those of parent compounds. This distribution pat-tern reflects the fact that the contamination of the col-lected sediments is mainly from LRT and weathered agricultural soils.
Acknowledgements
The authors would like to thank Environmental Protection Administration (EPA) and National Science Council, Taiwan, ROC for the financial supports under the Contract No. EPA-87-E3L1-03-02 and NSC 90-2621-Z-007-002.
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