Organochlorine pesticides in aquatic hydrophyte tissues and surrounding sediments in Baiyangdian wetland, China

Ecological Engineering 67 (2014) 150–155

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Organochlorine pesticides in aquatic hydrophyte tissues and surrounding sediments in Baiyangdian wetland, China Wei Guo a,∗ , Huayong Zhang a , Shouliang Huo b a b

Research Center for Ecological Engineering and Nonlinear Science, North China Electric Power University, Beijing 102206, China State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Science, Beijing 100012, China

a r t i c l e

i n f o

Article history: Received 9 October 2013 Received in revised form 26 January 2014 Accepted 29 March 2014 Available online 4 May 2014 Keywords: Organochlorine pesticides Aquatic hydrophyte Sediment Plant tissues Bioconcentration Wetland

a b s t r a c t The levels of 13 organochlorine pesticides (OCPs) in the sediments obtained from Baiyangdian wetland in China were determined to evaluate the effect of aquatic hydrophytes, Ceratophyllum demersum, Phragmites, and Typha, on the distribution of OCPs in the wetland sediments. The total OCP concentration in the sediments was in the range 3.60–11.12 ng g−1 on a dry weight basis. The surface sediment concentrations were higher than those near the roots of aquatic hydrophytes. Dichlorodiphenyltrichloroethanes predominated in the sediments. The OCP concentration in the plant tissues was in the range 4.72–11.19 ng g−1 on a dry weight basis with the highest concentration in Phragmites leaves. Under the water, the plant tissues in the roots accumulated more OCPs than those in the stems. The relationship between the OCP octanol–water partitioning coefficient and bioconcentration factor in these media indicated that less hydrophobic hexachlorocyclohexane and endosulfans were more easily accumulated and transported in plant tissues. Compared to the other two aquatic plants, Phragmites showed more effective OCP removal from the sediments in the wetland. © 2014 Elsevier B.V. All rights reserved.

1. Introduction Organochlorine pesticides (OCPs) in the environment have been a global concern due to their persistence, bioaccumulation, and toxicity (Totten et al., 2004). OCPs have a high potential for bioaccumulation and biomagnification in biological tissues and may even pose hazard to the human beings through food chain (Soto et al., 1994). Although most OCPs has been restricted in many countries since the 1980s, they still have a high residue level and risk in the water, soil, and sediment in some agricultural areas due to past and present usage (Barakat et al., 2012; Sojinu et al., 2012; Shi et al., 2013). The studies on contamination level, risk, and remediation of OCPs in environmental media in this area are relatively recent (Bert et al., 2009; Gao et al., 2013). OCPs can spread into aquatic environment through runoff from contaminated soil, wastewater discharge, and atmospheric transport and fallout (Yang et al., 2013). Because of strong hydrophobicity, OCPs are easily adsorbed onto suspended particulate matter, accumulate, and finally settle in sediments. Under certain conditions, the OCPs in sediment can transport back

∗ Corresponding author. E-mail addresses: [email protected], [email protected] (W. Guo). http://dx.doi.org/10.1016/j.ecoleng.2014.03.047 0925-8574/© 2014 Elsevier B.V. All rights reserved.

to water via resuspension (Liu et al., 2008) and migrate to hydrophytes tissues via root uptake (Zhao et al., 2009). The organic matter in sediments and hydrophytes regulate the risk and bioavailability of OCPs in the interface of water and sediment (Li et al., 2011). Significant differences have been observed in the dichlorodiphenyltrichloroethane (DDT) level between the sediments and rhizo-sediments of Schoenoplectus californicus, as well as the DDT level in bulrush tissues, indicating the capability of that plant to uptake DDTs in sediments (Miglioranza et al., 2004). Thus, an investigation on the contamination characteristics of OCPs in bed sediments and aquatic hydrophytes is important to evaluate and control the potential risk of OCPs in aquatic environments. Baiyangdian wetland, the largest shallow (mean depth <2 m) freshwater wetland in northern China (Fig. 1), plays an important role in the region’s drinking water supply, sustaining agriculture, climate regulation, and flood control. The wetland comprises >100 small wetlands that are linked together by thousands of ditches, covering an average total area of 362.8 km2 within a catchment of 31,200 km2 . Phragmites, Typha, and C. demersum are the dominant emergent and submerged plants, respectively. These hydrophytes, with the highest growth rate and biomass, are distributed in the total littoral zone of the wetland. With the agricultural and industrial developments in the region, the wetland has suffered severe organic pollution such as polycyclic aromatic hydrocarbons (PAHs)

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obtained from the Beijing Chemical Factory (Beijing, China) and Tedia Co. (Tedia, USA). The deionized water was processed through a Milli-Q system (Millipore Co., USA). 2.3. Extraction and cleanup of samples

Fig. 1. Map of the study area.

Approximately 2 g (on a dry weight basis) of each sample was sonically extracted with a mixture of 20 mL hexane/dichloromethane (1:1). Each sample was extracted three times for 15 min for each extraction. A known mixture of surrogates (4,4 -dichlorobiphenyl, 10 ␮L) was added before each blank and sample extraction. Two grams of activated copper chips was added to remove elemental sulfur from the extracts. The extracts were concentrated to ∼1–2 mL using a rotary evaporator and then passed through a 1:2 alumina/silica gel glass column with 1 g anhydrous sodium sulfate over the silica gel for purification and fractionation. The elution was performed using 50 mL of a mixture of hexane/dichloromethane (3:1). The eluates were then concentrated to 0.50 mL under a gentle stream of purified N2 and preserved in a freezer at −20 ◦ C until further analysis using a gas chromatograph (GC) with a 63 Ni electron capture detector (GC-ECD). 2.4. OCP analysis

and OCPs in water and sediment (Hu et al., 2010; Dai et al., 2011). However, studies on the distribution and bioaccumulation of OCPs in sediments and different aquatic plant tissues in freshwater wetlands, particularly for in situ conditions, are rare. Thus, the residue levels and distribution characteristics of OCPs were compared in the sediments without plants, near-root sediments, and hydrophyte tissues such as Phragmites, Typha, and C. demersum from Baiyangdian wetland to better understand the effect of aquatic hydrophytes on the distribution and risk of OCPs in wetland sediments.

After adding a known quantity of the IS (pentachloronitrobenzene, 10 ␮L), the OCPs were determined using a Hewlett-Packard 6890 GC-ECD. All the congeners were separated using an HP-5 capillary column (30 m × 0.25 mm × 0.25 ␮m) as follows: A 1 ␮L sample was injected in splitless mode. The carrier gas, helium, flow rate was 1.0 mL min−1 . The injection temperature started at 100 ◦ C, increased to 190 ◦ C at a rate of 20 ◦ C min−1 , and then increased again to 275 ◦ C (held for 10 min) at a rate of 4 ◦ C min−1 . The concentrations of the individual OCPs were obtained using the IS peak area method and a six-point calibration curve for the individual components.

2. Materials and methods 2.5. Quality assurance and quality control 2.1. Sampling The study was conducted in August 2012 at Baiyangdian wetland (Fig. 1). Phragmites (PH), Typha (TY), C. demersum (CE) sediments without plants and the sediments near plant root were collected from Shaochedian Lake. The input for the pollution is in both Baigouyinhe and Fuhe Rivers in the wetland. The sediment samples (top 0–10 cm) without plants were collected 5 m from the aquatic plants, and the sediment samples near plant root were collected 10–20 cm near plant roots. The hydrophytes were collected using a 20 cm × 20 cm sampler and divided into different plant tissues including roots, stems, and leaves. Each sample was collected for six parallel samples. The samples were then freeze-dried, homogenized, and stored at −20 ◦ C until further analysis. 2.2. Chemical reagents The 13 OCP standards in 10 mg L−1 solutions were as follows: ˛-hexachlorocyclohexane (HCH), ˇ-HCH, -HCH, ı-HCH, p -DDE, p,p -DDD, p,p -DDT, heptachlor, aldrin, dieldrin, endrin, ␣endosulfan, and ␤-endosulfan (AccuStandard, USA). The internal standard (IS) of pentachloronitrobenzene and surrogate standard (SS) of 4,4 -dichlorobiphenyl were purchased from Aldrich Co. (Aldrich Co., USA). These standards were diluted to the IS working standard concentration of 1 mg L−1 and SS working standard concentration of 10 mg L−1 . All the solvents used for the sample processing and analysis were of analytical and HPLC grade and

All the data were subjected to strict quality control procedures. The method detection limit (MDL) was in the range 0.02–0.06 ng g−1 for the OCPs. The spiked samples in each set of 15–20 samples had mean recoveries ranging from 71% to 115%. Each extract was analyzed in duplicate. The relative standard deviations were <15%. 3. Results and discussion 3.1. OCPs in sediments The OCP concentrations in the sediments near the hydrophyte zone of Baiyangdian wetland are listed in Table 1. Most of the OCPs were found in the sediment samples except ıHCH. The following order of individual OCPs was observed: DDTs (0.99–3.00 ng g−1 on a dry weight basis) > aldrin–endrin (0.84–2.56 ng g−1 on a dry weight basis) > HCHs (0.71–2.52 ng g−1 on a dry weight basis) > endosulfan (0.71–2.07 ng g−1 on a dry weight basis) > heptachlor (0.34–0.98 ng g−1 on a dry weight basis). DDTs were the most abundant compounds among the OCPs, accounting for 28% of the total OCPs. This can be attributed to the frequent utilization of DDT for agricultural activities in the past (Tao et al., 2008). In addition, the continued use of commercial dicofol (acaricide) containing DDT in cotton and fruit crops may be another reason for the high DDT content in the area (Gao et al., 2008). Aldrin–endrin also exhibited a higher concentration in

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Table 1 Concentration (ng g−1 dry weight) of OCPs in sediments near the aquatic plant zone in Lake Baiyangdian. Plant species

Ceratophyllum demersum

Typha

Phragmites

Sediment type

WPS

NRS

WPS

NRS

WPS

NRS

˛-HCH ˇ-HCH -HCH ı-HCH p,p -DDE p,p -DDD p,p -DDT Heptachlor Aldrin Dieldrin Endrin ˛-Endosulfan ˇ-Endosulfan HCHs DDTs OCPs TOC

0.54 0.69 0.64
0.42 0.60 0.51
0.69 1.03 0.80
0.34 0.44 0.38
0.48 0.87 0.54
0.22 0.25 0.24
MDL, method detection limit; WPS, sediments without plant; NRS, sediments near plant roots.

the sediments compared to other OCPs, accounting for 23% of the total OCPs. After DDTs, aldrin–dieldrin was the second most commonly used agricultural insecticide (U.S. Environmental Protection Agency USEPA, 1992). The higher aldrin–endrin residue in sediments indicates that they are still used (Jiang et al., 2009). Aldrin is readily converted to dieldrin in the environment (Yang et al., 2012). Technical endosulfan is a mixture of two isomers (˛ and ˇ) in the ratio 70–80% ˛ to 30–20% ˇ, w/w (Leonard et al., 2001). The ratio of the ˛-endosulfan to endosulfan in all the samples was 52%. The higher residue level of heptachlor and ˛-endosulfan in the sediment samples indicates the frequency of recent pesticide use in the area. Similar results were obtained in the agricultural soil of Shanghai (Jiang et al., 2009) The total OCP concentration was in the range 3.60–11.12 ng g−1 on a dry weight basis in the sediments. Compared to other lakes in China, the DDT and HCH residues were lower in Boyang Lake (DDTs: 14.42–82.87 ng g−1 ; HCHs 0.53–6.94 ng g−1 ) (Lu et al., 2012) and Taihu Lake (DDTs: 0.25–375 ng g−1 ; HCHs 0.07–5.75 ng g−1 ) (Zhao et al., 2009), whereas the aldrin–dieldrin levels were much higher. This may be attributed to the different production and usage of OCPs in different regions in China (Yang et al., 2005). The OCP concentrations varied in the different sediment samples, the total OCP concentrations in the sediments near plant root (in the range 3.60–7.03 ng g−1 ) were obviously lower than those in the sediments without plants (in the range 7.91–11.12 ng g−1 ). The same distribution pattern was also observed in individual OCP concentration. This may be attributed to the absorption of OCPs by aquatic plant roots (Miglioranza et al., 2004). Compared to the concentration of OCPs in the sediments without plants, the concentrations near the plant root of PH, TY, and CE were decreased by 22.5%, 50.1%, and 54.5%, respectively. Thus, the plant roots of PH have a higher OCP uptake ability than those of TY and CE, and the developed root system of emergent plants facilitates the absorption and degradation of OCPs in sediments (Carvalho et al., 2011). Moreover, total organic carbon (TOC) can also affect the distribution of OCPs in sediments (Hu et al., 2009). The highest level of total OCPs was detected in the sediments without plants near the TY zone, corresponding to the highest TOC content (1.01%). A good correlation was observed between the OCPs and TOC (r = 0.83, P < 0.01) in the sediment samples indicating that sediment organic matter increased the absorption of these compounds.

3.2. OCPs in aquatic plant tissues The OCP concentrations in the tissues of typical hydrophytes in Baiyangdian wetland are listed in Table 2. The submerged plant, CE, was divided into above-sediment parts (stems and leaves) and underground-sediment parts (roots) because of full submersion in water. The emergent plants TY and PH were divided into three parts: roots, stems, and leaves. Compared to the sediments, p,p -DDT was not detected in all the plant tissues. This is probably because of the high hydrophobic nature of p,p -DDT. Because of the physicochemical properties of p,p -DDT, it cannot be absorbed by plant roots and remains in sediments for a longer period (Carvalho et al., 2011). For all the plant tissues, the same OCP distribution pattern was observed with HCHs (1.76–3.68 ng g−1 on a dry weight basis) > DDTs (0.92–3.18 ng g−1 on a dry weight basis) > aldrin–endrin (0.88–1.82 ng g−1 on a dry weight basis) > endosulfan (0.77–1.62 ng g−1 on a dry weight basis) > heptachlor (0.39–0.89 ng g−1 on a dry weight basis). The similar distribution patterns of individual OCPs among different plant tissues indicated that the transport of different types of OCPs within the plant was controlled by a common mechanism or the OCPs in plants originated from the same sources. HCHs were the most abundant compounds, accounting for 37% of the total OCPs. This finding could be attributed to the easy uptake and transport of HCHs by plants owing to their lower hydrophobicity and higher OCP bioavailability (Li et al., 2011). Moreover, the higher HCH concentrations in tissues may be attributed to their extensive use in the past (Tao et al., 2008). The total OCP concentration was in the range 4.72–11.19 ng g−1 on a dry weight basis in plant tissues with the highest value in the leaves of PH and the lowest value in the stems of TY. No positive relationship was observed between the lipid content and OCP concentration in these plant tissues (Table 2), indicating that probably other non-lipid cellular components such as lignin contribute to chemical compound partitioning (Trapp et al., 2001). For submerged plant CE, the concentration of OCPs in the roots was higher than that in the stems + leaves. The hydrophobicity of OCPs indicates that sediments frequently contain higher concentrations than the overlying waters. Thus, CE accumulated higher concentration of pollutants in the roots than in the stem + leaves. For emergent plants TY and PH, the OCP distribution had a different trend in tissues with the order: leaves > roots > stems. This may be attributed

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Table 2 Distribution (ng g−1 dry weight) of OCPs in tissues of different plants including Ceratophyllum demersum, Typha, and Phragmites. Plant species

Ceratophyllum demersum

Typha

Phragmites

Plant tissue

Roots

Stems + leaves

Roots

Stems

Leaves

Roots

Stems

Leaves

˛-HCH ˇ-HCH -HCH ı-HCH p,p -DDE p,p -DDD p,p -DDT Heptachlor Aldrin Dieldrin Endrin ˛-Endosulfan ˇ-Endosulfan HCHs DDTs OCPs Lipids (%)

0.85 1.17 0.85
0.58 0.70 0.63
0.76 1.07 0.84
0.53 0.66 0.57
0.90 1.20 1.03
0.89 1.19 0.97
0.63 1.03 0.76
1.10 1.40 1.18
MDL, method detection limit.

1.05 α-HCH/γ-HCH

1.00

p,p'-DDE/p,p'-DDD

0.95 0.90 0.85 0.80 0.75

PH-leaves

PH-stems

PH-roots

TY-leaves

TY-stems

TY-roots

CE-roots

CE(stems+leaves)

PH-NRS

PH-WPS

TY-NRS

TY-WPS

0.70 CE-NRS

The composition characteristics of HCH and DDT congeners in the environment may indicate different OCP contamination sources and accumulation times, recent or past (Doong et al., 2002). In this study, the HCH concentrations recorded in the sediments and plant tissues were in the ranges 0.22–1.10 ng g−1 , 0.25–1.40 ng g−1 , and 0.24–1.18 ng g−1 on a dry weight basis for ˛-HCH, ˇ-HCH, and -HCH, respectively (Tables 1 and 2). Among the HCHs, ˇ-HCH had the highest ratio to HCHs (39%) in all the samples because of its low vapor pressure and relative resistance to microbial degradation (Willett et al., 1998) and the absence of new inputs of HCHs in the area (Doong et al., 2002). Moreover, ˛and -HCH are more volatile because of their relatively high vapor pressures and are transformed to ˇ-HCH in the aged environmental samples (Walker et al., 1999). Typical technical HCHs contain 55–80% ˛-HCH, 5–14% ˇ-HCH, 8–15% -HCH, and 2–16% ı-HCH (Lee et al., 2001). Moreover, HCHs were available in pure form as lindane (>99% -HCH) (Jiang et al., 2009). Therefore, the ratio of ˛-HCH to -HCH is between 3 and 7 for the technical mixture and almost zero for lindane (Strandberg et al., 1998; Yang et al., 2008). If no degradation of HCHs occurred in the sediments and plants after the absorption, this ratio will provide insight into the sources of HCHs in the sediments and plants (Sojinu et al., 2012; Yang et al., 2013). In this study, the ˛-HCH/-HCH ratios were in the range 0.82–1.00 (Fig. 2). Based on these recorded ratios; no fresh input of technical HCHs in the sediments and plants under investigation was found. Thus, the presence of HCHs in the sediments and plants can be attributed to the past use of lindane in pest control. In general, technical DDTs contain 75% p,p -DDT, 15% o,p -DDT, 5% p,p -DDE, and <5% of other compounds. The concentrations of the DDTs recorded in the sediments and plant tissues were in the

CE-WPS

3.3. Sources of OCPs

ranges not detectable (ND) to 1.02 ng g−1 , 0.34–1.36 ng g−1 , and 0.30–1.50 ng g−1 on a dry weight basis for p,p -DDT, p,p -DDD, and p,p -DDE, respectively (Tables 1 and 2). The higher contents of p,p -DDD and p,p -DDE may be attributed to the degradation and transformation of p,p -DDT. p,p -DDT can be easily degraded under aerobic and anaerobic conditions to p,p -DDE and p,p -DDD, respectively (Aislabie et al., 1997). The results of this study show the dominance of p,p -DDD over p,p -DDE in the sediments (Table 1) may indicate possible biological transformation under anaerobic conditions (Barakat et al., 2012). Although plant root can release oxygen, the quantity is not enough to change the anaerobic conditions. The change in the ratio of DDE and DDD to DDTs can provide information on a region’s history of DDT application. A ratio of p,p -DDE/p,p -DDD <1.0 indicates the historical application of DDTs (Gao et al., 2013), whereas a ratio >1.0 indicates more recent applications (Sojinu et al., 2012). In this study, the small ratio (in the range 0.82–0.97) indicates that no technical DDT was recently introduced to the Baiyangdian wetland region (Fig. 2). The DDTs in the sediment and plant tissues from Lake Baiyangdian were derived primarily from weathered agricultural soils, where the degradation of DDTs occurred significantly after they were banned officially (Doong et al., 2002).

Ratio

to the differences in OCP nature, source, and input pathway for aquatic plants. The high OCP concentrations found in plant leaves indicated that atmospheric fallout may be an important input pathway for OCPs other than plant transportation and uptake. Airborne particulate and volatile organic compounds (VOCs) probably contributed to the OCP sources for the cuticle and inner tissues in the leaves, respectively (Wang et al., 2008). These OCP distribution patterns in plant tissues were similar to the previous studies on OCPs or other types of persistent organic pollutants (POPs) (Liu et al., 2006; Guo et al., 2011; Desalme et al., 2011).

samples Fig. 2. Diagnostics for distinguishing contamination sources of OCPs. CE, Ceratophyllum demersum; TY, Typha; PH, Phragmites; WPS, sediments without plant; NRS, sediments near plant roots.

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CE-WPS CE-NRS TY-WPS

0.15

TY-NRS

PC2(39%)

PH-WPS 0.10

PH-NRS CE-roots CE-(stems+leaves)

0.05 -0.05

0.00

TY-roots 0.05

0.10

0.15

TY-stems TY-leaves

0.00

PH-roots PH-stems PH-leaves

-0.05

PC1(58%) Fig. 3. Principal component analysis (PCA) on OCPs in sediments and plant tissues from Lake Baiyangdian. CE, Ceratophyllum demersum; TY, Typha; PH, Phragmites; WPS, sediments without plant; NRS, sediments near plant roots.

Principal component analysis (PCA) was performed to evaluate the contribution of main OCP sources and identify the relationship between OCPs in the plants and sediments (Fig. 3). Two principal components (58% and 39%) were considered in the PCA analysis, accounting for 97% of the total variation. Along the PC1 and PC2 axes, the samples were clearly separated into two groups: the sediments and plant tissues. The sediments were rich in DDTs; these compounds have high hydrophobicity, resistance to photooxidation, low vapor pressure, and bioaccumulation and persistence in sediments (Carvalho et al., 2011). In contrast, the plant tissues were rich in HCHs; these compounds have lower hydrophobicity and higher OCP bioavailability (Li et al., 2011). The loading pattern can be attributed to the physicochemical properties shared by the majority of OCPs and the different absorption and uptake of OCPs by plant tissues and sediments. 3.4. Partitioning of OCPs between sediments and roots The OCPs in sediments may enter aquatic plants by root uptake or may be degraded by the microbial population in the rhizosphere and translocated to other parts of the plants (Susarla et al., 2002). Root concentration factor (RCF) was used to describe the distribution of OCPs in these plants roots and sediments (Miglioranza et al., 2004). The RCF of the OCPs from the sediments near plant root and plants was calculated by using the following equation: RCF =

Croot CNRS

where Croot and CNRS are the accumulated concentration in the roots and sediments near plant root, respectively, on a dry weight basis (ng g−1 ). Both the average RCFs of these plants were above 1 in our study (Table 3); however, the RCFs varied for different OCPs. The calculated RCF values ranged from 0.63 (endrin) to 2.03 (˛HCH) for CE, 0.65 (aldrin) to 2.44 (ˇ-HCH) for TY, and 0.98 (endrin) to 4.78 (ˇ-HCH) for PH. The majority of the individual OCP RCFs of these plants were above or near 1; only the RCF of aldrin and endrin of CE and TY were below 1. Based on the analysis of RCF, less hydrophobic HCHs and endosulfans were more easily accumulated and transported in the plant tissues (Table 3). The presence of a relatively high RCF of the less hydrophobic pesticides such as HCHs (RCF = 2.2–61.1; Kow = 3.78–4.15; Kow = octanol–water partitioning coefficient) in roots and that of relatively low RCF of the most hydrophobic pesticides such as aldrin and endrin (RCF = 0.5–1.2; Kow = 5.30–5.34) are consistent with the findings reported for S. californicus (C.A. Meyer) from a shallow lake in Argentina (Miglioranza et al., 2004). Compared to the other two aquatic plants, the PH roots showed more effective OCP uptake from the sediments in the wetland. The relationship between OCP Kow and bioconcentration factor in these media showed that the RCF of each plant correlated negatively (R2 = 0.316, CE; R2 = 0.336, TY; R2 = 0.357, PH) with the Kow of the OCPs (Fig. 4), indicating that the uptake of OCPs by roots is controlled by their Kow values.

(1) 1.50 CE

Table 3 Bioaccumulation of OCPs for aquatic plants as calculated from roots to near root sediment (NRS). CE-RCF

TY-RCF

PH-RCF

˛-HCH ˇ-HCH -HCH p,p -DDE p,p -DDD Heptachlor Aldrin Dieldrin Endrin ˛-Endosulfan ˇ-Endosulfan Average

2.03 1.93 1.67 1.17 1.04 1.05 0.64 1.14 0.63 1.06 1.24 1.24

2.24 2.44 2.22 1.11 1.02 1.07 0.65 1.23 0.86 1.22 1.23 1.39

3.98 4.78 4.04 1.49 1.40 1.96 1.47 2.13 0.98 1.87 1.91 2.36

RCF, root concentration factor; CE, Ceratophyllum demersum; TY, Typha; PH, Phragmites.

PH

1.00

LogRCF

Compounds

TY

0.50

0.00

-0.50

-1.00 2.50

3.00

3.50

4.00

4.50

5.00

5.50

6.00

6.50

LogKow

Fig. 4. Relationships between RCF and Kow of OCPs. Both variables are log transformed. RCF, root concentration factor; CE, Ceratophyllum demersum; TY, Typha; PH, Phragmites.

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4. Conclusions This study explains the distribution characteristics of OCPs in the surficial sediments, sediments near plant root, and hydrophyte tissues such as roots, stems, and leaves from a typical freshwater wetland. DDTs are more easily enriched in the sediments and HCHs are more easily accumulated in the plant tissues because of their past usage and hydrophobic nature. Higher residues of aldrin–endrin were observed in the sediments, in the range 0.84–2.56 ng g−1 , indicating that these compounds may still being used. The aquatic plants can reduce the residual OCPs in sediments by root uptake. The concentrations near the plant root of PH, TY, and CE decreased by 22.5%, 50.1%, and 54.5%, respectively. Under the water, the plant tissues in the roots accumulated more OCPs than those in the stems. The results of OCP molecular ratio and PCA indicated that the sources of OCPs in the sediments and plants can be attributed to the past use in pest control. The OCPs in the sediments originated mainly from the residual OCPs because of long weathering and degradation; however, those in the plants mainly originated from the bioavailable OCP transport. In these hydrophytes, PH showed more valuable use as a tool for studying OCP pollution, monitoring, and remediation. Acknowledgments This study was funded by the National Natural Science Foundation of China (No. 41201509). Additional funding was provided by the Fundamental Research Funds for the Central Universities of China. References Aislabie, J.M., Richards, N.K., Boul, H.L., 1997. Microbial degradation of DDT and its residues: a review. N. Z. J. Agric. Res. 40, 269–282. Barakat, A.O., Mostafa, A., Wade, T.L., Sweet, S.T., El Sayed, N.B., 2012. Assessment of persistent organochlorine pollutants in sediments from Lake Manzala, Egypt. Mar. Pollut. Bull. 64, 1713–1720. Bert, V., Seuntjens, P., Dejonghe, W., Lacherez, S., Thuy, H., Vandecasteele, B., 2009. Phytoremediation as a management option for contaminated sediments in tidal marshes, flood control areas and dredged sediment landfill sites. Environ. Sci. Pollut. Res. 16, 745–764. Carvalho, P.N., Rodrigues, P.N.R., Evangelista, R., Basto, M.C.P., Vasconcelos, M.T.S.D., 2011. Can salt marsh plants influence levels and distribution of DDTs in estuarine areas? Estuar. Coast. Shelf Sci. 93, 415–419. Dai, G.H., Liu, X.H., Liang, G., Han, X., Shi, L., Cheng, D.M., Gong, W.W., 2011. Distribution of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in surface water and sediments from Baiyangdian Lake in North China. J. Environ. Sci. 23 (10), 1640–1649. Desalme, D., Binet, P., Bernard, N., Gilbert, D., Toussaint, M., Chiapusio, G., 2011. Atmospheric phenanthrene transfer and effects on two grassland species and their root symbionts: a microcosm study. Environ. Exp. Bot. 71, 146–151. Doong, R.A., Sun, Y.C., Liao, P.L., Peng, C.K., Wu, S.C., 2002. Distribution and fate of organochlorine pesticide residues in sediments from the selected rivers in Taiwan. Chemosphere 48, 237–246. Gao, J.J., Liu, L.H., Liu, X.R., Lu, J., Zhou, H.D., Huang, S.B., 2008. Occurrence and distribution of organochlorine pesticides-lindane, p,p-DDT, and heptachlor epoxidein surface water of China. Environ. Int. 34, 1097–1103. Gao, J., Zhou, H.F., Pan, G.Q., Wang, J.Z., Chen, B.Q., 2013. Factors influencing the persistence of organochlorine pesticides in surface soil from the region around the Hongze Lake, China. Sci. Total Environ. 443, 7–13. Guo, W., Pei, Y.S., Yang, Z.F., Wang, C.H., 2011. Assessment on the distribution and partitioning characteristics of polycyclic aromatic hydrocarbons (PAHs) in Lake Baiyangdian, a shallow freshwater lake in China. J. Environ. Monit. 13, 681–688. Hu, G.C., Luo, X.J., Li, F.C., Dai, J.Y., Guo, J.Y., Chen, S.J., Hong, C., Mai, B.X., Xu, M.Q., 2010. Organochlorine compounds and polycyclic aromatic hydrocarbons in surface sediment from Baiyangdian Lake, North China: concentrations, sources profiles and potential risk. J. Environ. Sci. 22, 176–183.

155

Hu, L.M., Zhang, G., Zheng, B.H., Qin, Y.W., Lin, T., Guo, Z.G., 2009. Occurrence and distribution of organochlorine pesticides (OCPs) in surface sediments of the Bohai Sea, China. Chemosphere 77, 663–672. Jiang, Y.F., Wang, X.T., Jia, Y., Wang, F., Wu, M.H., Sheng, G.Y., Fu, J.M., 2009. Occurrence, distribution and possible sources of organochlorine pesticides in agricultural soil of Shanghai, China. J. Hazard. Mater. 170, 989–997. Lee, K.T., Tanabe, S., Koh, C.H., 2001. Distribution of organochlorine pesticides in sediments from Kyeonggi Bay and nearby areas, Korea. Environ. Pollut. 114, 207–213. Leonard, A.W., Hyne, R.V., Lim, R.P., Leigh, K.A., Le, J., Becket, R., 2001. Fate and toxicity of endosulfan in Namoi River and bottom sediment. J. Environ. Qual. 30, 750–759. Li, H., Ling, W., Lin, C., 2011. Fishpond sediment-borne DDTs and HCHs in the Pearl River Delta: characteristics, environmental risk and fate following the use of the sediment as plant growth media. J. Hazard. Mater. 186, 1474–1480. Liu, M., Yang, Y., Xu, S., Liu, H., Hou, L., Ou, D., Liu, Q., Cheng, S., 2006. HCHs and DDTs in salt marsh plants (Scirpus) from the Yangtze estuary and nearby coastal areas, China. Chemosphere 62, 440–448. Liu, M., Cheng, S.B., Ou, D.N., Yang, Y., Liu, H.L., Hou, L.J., Gao, L., Xu, S.Y., 2008. Organochlorine pesticides in surface sediments and suspended particulate matters from the Yangtze estuary, China. Environ. Pollut. 156, 168–173. Lu, M., Zeng, D.C., Liao, Y., Tong, B., 2012. Distribution and characterization of organochlorine pesticides and polycyclic aromatic hydrocarbons in surface sediment from Poyang Lake, China. Sci. Total Environ. 433, 491–497. Miglioranza, K.S.B., De Moreno, J.E.A., Moreno, V.J., 2004. Organochlorine pesticides sequestered in the aquatic hydrophyte Schoenoplectus californicus (C. A. Meyer) Soják from a shallow lake in Argentina. Water Res. 38, 1765–1772. Shi, Y.J., Lu, Y.L., Meng, F.Q., Guo, F.F., Zheng, X.Q., 2013. Occurrence of organic chlorinated pesticides and their ecological effects on soil protozoa in the agricultural soils of North Western Beijing, China. Ecotoxicol. Environ. Saf. 92, 123–128. Sojinu, O.S., Sonibare, O.O., Ekundayo, O.O., Zeng, E.Y., 2012. Assessment of organochlorine pesticides residues in higher plants from oil exploration areas of Niger Delta, Nigeria. Sci. Total Environ. 433, 169–177. Soto, A.M., Chung, K., Sonnenshein, C., 1994. The pesticides endosulfan, toxaphene and dieldrin have estrogenic effects on human estrogen-sensitive cells. Environ. Health Perspect. 102, 380–383. Strandberg, B., Bavel, B.V., Bergqvist, P.A., Broman, D., Ishaq, R., Naf, C., Pettersen, H., Rappe, C., 1998. Occurrence, sedimentation and spatial variations of organochlorines contaminants in settling particulate matter and sediments in the northern part of the Baltic Sea. Environ. Sci. Technol. 32, 1754–1759. Susarla, S., Medina, V.F., McCutcheon, S.C., 2002. Phytoremediation: an ecological solution to organic chemical contamination. Ecol. Eng. 18, 647–658. Tao, S., Liu, W., Li, Y., Yang, Y., Zu, Q., Li, B., Cao, J., 2008. Organochlorine pesticides contaminated surface soil as reemission source in the Haihe Plain, China. Environ. Sci. Technol. 42, 8395–8400. Totten, L.A., Gigliotti, C.L., Vanry, D., Offenberg, J.H., Nelson, E., Dachs, J., Reinfelder, J.R., Eisenreich, S.J., 2004. Atmospheric concentrations and deposition of polychorinated biphenyls to the Hudson River Estuary. Environ. Sci. Technol. 38, 2568–2573. Trapp, S., Miglioranza, K.S.B., Mosbaek, H., 2001. Sorption of lipophilic organic compounds to wood and implications for their environmental fate. Environ. Sci. Technol. 35, 1561–1566. USEPA, 1992. National Study of Chemical Residues in Fish, EPA-823-R-92-008a. U.S. Environmental Protection Agency. Walker, K., Vallero, D.A., Lewis, R.G., 1999. Factors influencing the distribution of lindane and other hexachlorocyclohexanes in the environment. Environ. Sci. Technol. 33, 4373–4378. Wang, Z., Yan, W., Chi, J., Zhang, G., 2008. Spatial and vertical distribution of organochlorine pesticides in sediments from Daya Bay, South China. Mar. Pollut. Bull. 56, 1578–1585. Willett, K.L., Ulrich, E.M., Hites, R.A., 1998. Differential toxicity and environmental fates of hexachlorocyclohexane isomers. Environ. Sci. Technol. 32, 2197–2207. Yang, D., Qi, S.H., Zhang, J.Q., Wu, C.X., Xing, X.L., 2013. Organochlorine pesticides in soil, water and sediment along the Jinjiang River mainstream to Quanzhou Bay, southeast China. Ecotoxicol. Environ. Saf. 89, 59–65. Yang, L., Li, D., Mu, D., 2008. Levels seasonal variations and sources of OCPs in ambient air of Guangzhou, China. Atmos. Environ. 42, 677–687. Yang, L.J., Li, X.Q., Zhang, P.F., Melcer, M.E., Wu, Y.X., Jan, U., 2012. Concentrations of DDTs and dieldrin in Long Island Sound sediment. J. Environ. Monit. 14, 878–885. Yang, R.Q., Lv, A.H., Shi, J.B., Jiang, G.B., 2005. The levels and distribution of organochlorine pesticides (OCPs) in sediments from the Haihe River, China. Chemosphere 61, 347–354. Zhao, Z.H., Zhang, L., Wu, J.L., Fan, C.X., 2009. Distribution and bioaccumulation of organochlorine pesticides in surface sediments and benthic organisms from Taihu Lake, China. Chemosphere 77, 1191–1198.