湖泊科学   2020, Vol. 32 Issue (3): 654-664.  DOI: 10.18307/2020.0306.
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研究论文

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许妍, 陈佳枫, 徐磊, 刘雨薇, 谢立莹, 王之卓, 金苗, 陈宇炜, 白洋淀表层沉积物中有机氯农药和全多氯联苯的分布特征及风险评估. 湖泊科学, 2020, 32(3): 654-664. DOI: 10.18307/2020.0306.
[复制中文]
XU Yan, CHEN Jiafeng, XU Lei, LIU Yuwei, XIE Liying, WANG Zhizhuo, JIN Miao, CHEN Yuwei. Distribution and risk assessment of organochlorine pesticides and polychlorinated biphenyls in surficial sediments from Lake Baiyangdian. Journal of Lake Sciences, 2020, 32(3): 654-664. DOI: 10.18307/2020.0306.
[复制英文]

基金项目

国家自然科学基金项目(41671468,41301546,51408119)、江苏省自然科学基金项目(BK20171356)和江苏省青蓝工程和污染控制与资源化国家重点实验室开放基金项目(PCRRF16018)联合资助

通信作者

许妍, E-mail:xuxucalmm@seu.edu.cn

文章历史

2019-05-06 收稿
2019-11-13 收修改稿

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白洋淀表层沉积物中有机氯农药和全多氯联苯的分布特征及风险评估
许妍1 , 陈佳枫1 , 徐磊1 , 刘雨薇1 , 谢立莹2 , 王之卓1 , 金苗3 , 陈宇炜4     
(1: 东南大学土木工程学院, 南京 210096)
(2: 辽宁省兴城市环境保护监测站, 兴城 125100)
(3: 中国科学院南京地理与湖泊研究所, 南京 210008)
(4: 南昌工程学院, 南昌 330099)
摘要:为了解白洋淀表层沉积物中有机氯农药(OCPs)和多氯联苯(PCBs)的污染情况,采用改进的GC-μECD方法对白洋淀11处沉积物进行了20种OCPs和全部209种PCB单体的定量检测和分析.结果显示:白洋淀11个沉积物样品共检出10种OCPs和24种PCBs,∑OCPs和∑PCBs的含量范围分别为1.22~52.45 ng/g(DW)和nd ~37.61 ng/g,在国内处于中等水平;OCPs组成中以HCHs和Dieldrin(狄氏剂)为主,分别占到∑OCPs的39.9%和31.5%,其中7个采样点的HCHs以林丹输入为主,4个采样点以工业六六六污染为主.DDTs检出率较低,来源主要为历史残留;检出的PCB单体以低氯联苯为主,其中一氯、二氯和三氯联苯占∑PCBs的64.73%;采用沉积物质量标准法进行生态风险评估,结果表明白洋淀地区沉积物中p,p'-DDD和∑PCBs生态风险较低,Dieldrin生态风险尚需关注,γ-HCH生态风险较高,不容忽视.
关键词白洋淀    沉积物    多氯联苯    有机氯农药    风险评估    
Distribution and risk assessment of organochlorine pesticides and polychlorinated biphenyls in surficial sediments from Lake Baiyangdian
XU Yan1 , CHEN Jiafeng1 , XU Lei1 , LIU Yuwei1 , XIE Liying2 , WANG Zhizhuo1 , JIN Miao3 , CHEN Yuwei4     
(1: School of Civil Engineering, Southeast University, Nanjing 210096, P. R. China)
(2: Environmental Protection Monitoring Station of Xingcheng City, Liaoning Province, Xingcheng 125100, P. R. China)
(3: Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China)
(4: Nanchang Institute of Technology, Nanchang 330099, P. R. China)
Abstract: To better understand the contamination of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in sediments from Lake Baiyangdian, 20 OCPs and all 209 PCB congeners were measured in 11 surficial sediment samples collected from different locations of Lake Baiyangdian. Moreover, the risks posed by OCPs and PCBs were assessed based on sediment quality guidelines. The results show that 10 OCPs and 24 PCB congeners were detectable. The total OCPs concentrations ranged from 1.22 to 52.45 ng/g(DW) (dry weight), while the total PCBs levels were from below detection limit to 37.61 ng/g. These results indicate a moderate pollution level within China. HCHs and Dieldrin were predominant in all OCPs, which accounted for 39.9% and 31.5% of total OCPs, respectively. Seven sampling sites of Lake Baiyangdian were contaminated by Lindane (γ-HCH) and the other 4 sampling sites were mainly contaminated by industrial HCHs. Moreover, new HCHs inputs might exist in some locations. DDTs levels were relatively low, which suggests that DDTs in Lake Baiyangdian might be the historical residues. PCBs detected in these sediment samples were dominated by low chlorinated PCBs congeners. Mono-, di-and tri-chlorinated biphenyls accounted for 64.73% of the total PCBs. However, it is noted that some new organochlorine pesticide pollution of HCHs may be present in some areas. Ecological risk assessment based on sediment quality guidelines revealed that the risks posed by p, p'-DDD and ∑PCBs were relatively lower, while the risk associated with Dieldrin was of concern. Notably, γ-HCH posed apparent adverse effects on the local ecological system.
Keywords: Lake Baiyangdian    sediments    polychlorinated biphenyls    organochlorine pesticides    risk assessment    

有机氯农药(Organochlorine pesticide,OCPs)和多氯联苯(Polychlorinated biphenyls,PCBs)是常见的两类有机氯污染物,具有“三致”毒性,近来研究更表明其会干扰生物内分泌系统、影响儿童智力发育[1].由于OCPs和PCBs分别在农业生产(杀虫)和工业应用(油漆、变压器油、电容器介电流体等)上表现卓越,曾在全球范围内被大量生产和使用.尽管1970s后,OCPs和PCBs的生产和使用受到了严格的限制,但由于其理化性质稳定,至今仍是备受关注的全球性污染问题. 1979年PCBs被美国环境保护署(USEPA)列入优先检测物黑名单,全美禁用;2001年斯德哥尔摩公约正式将PCBs、Aldrin、Dieldrin、Endrin、DDT、HCB、Heptachlor、Chordane列为8种(共12种)持久性有机污染物;2013年,在美国颁布的国家有害物质优先清单中,PCBs位列第5.中国在1980s前曾生产过大量的OCPs,其中以HCHs(450万吨)和DDTs(27万吨)为主[2-3].同时,统计显示,我国曾生产过近万吨的PCBs[4],并进口过大量的电力电容设备(含PCBs)[3],因历史局限性,这些PCBs存在较高泄露风险[5].调查发现,OCPs和PCBs有机氯污染物在国内的空气、土壤、河流湖泊以及沉积物中均有检出[6-9].白洋淀(38°43′~39°02′N,115°38′~116°07′E),水域面积约为366 km2,平均水深2~3 m,作为华北地区最大的浅水型湖泊,被誉为“华北之肾”. 2017年雄安新区设立后,白洋淀也成为新区的重要水源地之一.有机氯污染物因为疏水性,河流湖泊沉积物是其主要的“汇”. 2010 —2014年,虽然白洋淀有机氯污染物的调查发现了HCHs、DDTs和PCBs等污染物,存在不利生物风险(抚河地区),但总体上仍较为有限[10-14].本研究于雄安新区设立之初的2017年进行,以期为新区建设的生态影响提供科学依据.此外,受限于仪器分析方法,白洋淀地区PCBs的研究大多用几种到几十种PCBs单体来代表PCBs总量,而徐磊等[15]发现有限的PCBs单体检测会导致对环境中PCBs污染程度的低估.本研究希望通过对全部209种PCBs检测获得更加全面的数据.

本文以白洋淀11个主要人类活动区域的表层沉积物为研究对象,对20种OCPs和209种PCBs含量进行检测,并探讨其来源,同时评估其生态风险,为白洋淀水环境中有机氯污染防治和雄安新区生态环境综合整治提供科学依据和数据支持.

1 材料与方法 1.1 样品采集

在白洋淀水域内选取主要围绕人类活动地区重要水道和面积较大的淀,于2017年5月利用手持式GPS定位系统,选定11处采样点并标号BY1~BY11,依次代表苲淀、荷花淀、杨家淀、光淀、鸳鸯岛、李郎村、烧车淀河道、烧车淀中心、郭里口、大观园和烧车淀湿地.各个采样点水深0.43~0.97 m,水温18.81~20.86℃.使用抓斗式采泥器在每个采样点采集1~2 L的0~10 cm表层沉积物样品,去除多余的杂质、动植物残体等,水封于棕色硼玻璃瓶中,并置于低温(4℃)条件下备用. 11处采样点的具体位置、采样环境及地理分布如图 1所示.

图 1 白洋淀表层沉积物采样点分布 Fig.1 Sampling sites of surficial sediments in Lake Baiyangdian
1.2 仪器与试剂

主要仪器:Agilent 7890A气相色谱—电子捕获检测器(GC-μECD,美国安捷伦科技有限公司);Eyela N-1200B旋转蒸发仪(东京理化器械株式会);Eyela MGS-220氮吹仪(东京理化器械株式会);ZX3涡旋仪(美国赛默飞世尔科技).

主要试剂和药品:美国天地品牌,色谱纯,正己烷(n-Hexane 95 %)、丙酮(Acetone)、二氯甲烷(Dichloromethane)、异丙醇(Isopropanol);美国赛默飞世尔科技60~100目弗罗里土(Florisil);美国西格玛奥德里奇品牌,分析纯,无水硫酸钠(Na2SO4)、氯化钠(NaCl)、亚硫酸钠(Na2SO3)、四丁基硫酸氢铵(TBA)等;美国AccuStandard公司的多氯联苯单体及混合标准样品;OCPs标准物质和内标化合物:滴滴涕及其代谢产物系列;HCHs系列,狄氏剂(Dieldrin)、异狄氏剂(Endrin)、艾氏剂(Aldrin)、硫丹Ⅰ (Endosulfan Ⅰ)、硫丹Ⅱ (Endosulfan Ⅱ)、硫丹硫酸酯(Endosulfan sulfate)、十氯酮(Kepone)、甲氧滴滴涕(Methoxylor)、七氯(Heptachlor)、七氯环氧(Heptachlor epoxide)、六氯苯(Hexachloro- benzene,HCB)、灭蚁灵(Mirex)、氯丹(Chlordane,含顺反式)共20种OCPs标准物质和内标化合物五氯硝基苯(PCNB)以及回收指示物十氯联苯(PCB209)均购自美国Accustandard公司.

1.3 样品处理

样品有机氯污染物的萃取采用加速溶剂萃取法(ASE)(美国环境保护署《加压液体萃取(PFE)》(EPA Method 3545A)).沉积物样品自然风干后充分研磨并过60目不锈钢筛筛分;将5.0 g沉积物样品和5.0 g预处理过(马弗炉450℃,4 h)的石英砂加入放有纤维素滤膜的不锈钢萃取池中(34 mL),充分混合均匀.于萃取池中;以正己烷/丙酮(1 :1)混合液进行加压萃取.设定的萃取程序包括:预热5 min,静态萃取5 min,萃取压力10.3 MPa,萃取温度100℃,冲洗体积60 %,循环萃取2次.萃取完成后,转移萃取并液氮吹浓缩至1 mL.

萃取液的净化采用美国环境保护署《硫的净化》(EPA Method 3660B)和《硅酸镁载体柱净化》(EPA Method 3620)分别于萃取液中加入1 mL四丁基铵-亚硫酸钠(TBA)溶液和2 mL异丙醇,振荡至底部有晶体出现.加入4 mL超纯水充分摇匀至晶体溶解,静置分层,转移有机层(上层)溶液并氮吹浓缩至1 mL.于直径为10 mm的30 cm玻璃层析柱中自下而上填充8.0 g活化的弗罗里硅土和3.0 g预处理过的无水硫酸钠(马弗炉450℃,6 h);分别用90 mL正己烷和90 mL正己烷/二氯甲烷(4 :1)混合液梯度洗脱.洗脱液旋蒸浓缩、氮吹后定容至200 μL待进样.

1.4 气相色谱分析

采用配置63Ni微电子捕获检测器的气相色谱仪(GC-μECD) (Agilent 7890A)对OCPs和PCBs进行定量分析.使用的毛细管色谱柱为Agilent J & W GC Colimns DB-XLB(30 m× 0.18 mm×18 μm);色谱仪运行条件:进样口温度275℃,检测器温度300℃,载气为高纯氦气(99.999 %).升温程序:初始柱温50℃,保持1 min,然后以12℃/min升至150℃,接着以0.4℃/min升至220℃,最后以2℃/min升至260℃.进样量为1 μL,采用不分流进样.

1.5 质量控制

在上述色谱条件下,利用20种OCPs和209种PCBs的标样获得各物质色谱峰保留时间,据此对实际样品中的OCPs和PCBs进行定性.采用多点校正曲线法对样品进行外标定量分析,方法检测限 < 1 ng/mL.采用方法空白、平行样和加标回收对实验进行QA/QC控制.过程空白样中均无OCPs和PCBs检出;平行样相对偏差 < 5 %,OCPs和PCBs的平均加标回收率为85.3 % ~105.5 %和78.2 % ~102.6 % (详细见附录Ⅰ).

1.6 风险评估方法

鉴于国内无相应OCPs和PCBs沉积物质量标准,本研究参考国外沉积物质量标准法(sediment quality guidelines, SQGs)中使用较多的Long等[16]提出的生物毒性影响标准中的ERL(effects range low,低于该值毒性风险小于25 %)、ERM(effects range median,高于该值毒性风险大于75 %)值和加拿大魁北克省的标准中的TEL(the threshold effect level,低于该值几乎不会引起生物负效应)、PEL(the probable effect level,高于该值将有较大可能产生不利反应)值对白洋淀地区沉积物中的OCPs和PCBs进行风险评估.同时,根据检出的OCPs和PCBs,mERMq(mean ERM quotient)值将被用于污染物的综合风险评估,计算公式为:

$ mERMq = (\sum {C_x}/ER{M_x})/n $ (1)

式中,Cx指污染物x的检出浓度,ERMx指污染物x对应的ERM值或PEL值(出于风险评估保守性,部分ERM值用PEL值代替),n表示参与综合风险评估的污染物的数量.归类为:mERMq<0.1,风险最小,毒性概率仅为9 %;0.1≤mERMq<0.5,低风险,毒性概率为21 %;0.5≤mERMq<1.5,中风险,毒性概率为49 %;mERMq≥1.5,高风险,毒性概率为76 %.

2 结果与讨论 2.1 白洋淀表层沉积物中OCPs分布特征及分析

白洋淀11处表层沉积物的ΣOCPs含量在1.22~52.45 ng/g之间,均值为16.12 ng/g,与Hu等[17]的研究结果相近. 11处表层沉积物采样点中,BY5(鸳鸯岛)、BY9(郭里口)和BY11(烧车淀湿地)处的ΣOCPs含量相对较高,BY6(李郎村)和BY10(大观园)处的ΣOCPs含量相对较低(图 2).考虑到鸳鸯岛,郭里口和烧车淀湿地均为白洋淀的重要风景区,这3处地区较高的ΣOCPs含量可能与频繁的人类活动有关,而烧车淀湿地在三者中最高的ΣOCPs含量这一结果则还应考虑到湿地的生态截留作用[18].附录Ⅲ表 1中这3处区域较高含量的Aldrin、Endosulfan sulfate、Endrin ketone检出和相应较低的检出率印证了这3处地区较其他研究区域农药应用广泛的说法.

图 2 白洋淀表层沉积物中ΣOCPs含量 Fig.2 Content of total OCPs in surficial sediments from Lake Baiyangdian
表 1 白洋淀表层沉积物中OCPs分布情况* Tab. 1 Distribution of OCPs in surficial sediments from Lake Baiyangdian

白洋淀表层沉积物中OCPs分布情况如表 1所示,所检测的20种OCPs在所有采样点中共检出10种,分别为α-HCH、β-HCH、γ-HCH、δ-HCH、Aldrin、Dieldrin、p-p′-DDD、Endosulfan sulfate、Endrin ketone和methoxychlor.检出率较大(>50 %)的OCPs共有3种,其中α-HCH在所有采样点均有检出,含量范围为0.41~4.57 ng/g,其次为Dieldrin,检出率达82 %,含量范围为nd~19.83 ng/g,γ-HCH的检出率和含量范围分别为64 %和nd~20.77 ng/g,而其余7种检出的OCPs检出率均较低,仅在白洋淀个别地区有检出. OCPs分布情况显示HCHs和Dieldrin类农药曾在白洋淀地区使用广泛,这与国内湖泊的OCPs含量分布相似[24, 27, 33],而其余类型的农药使用较少且分布不均匀,只在局部地区使用.

国内不同地区水体沉积物中的ΣOCPs含量见表 2.与国内其他研究区域相比,白洋淀地区的ΣOCPs含量高于松花江流域、千岛湖和长江中下游,接近于韩江流域、太湖梅梁湾和博斯腾湖等,较其他水体沉积物中的ΣOCPs含量低.总体来说,白洋淀地区表层沉积物中的ΣOCPs含量在我国处于中等水平,与2010年白洋淀调查所显示的ΣOCPs平均含量无明显差异.

表 2 国内不同地区表层沉积物中OCPs含量比较 Tab. 2 Comparison of OCPs content in surficial sediments from different domestic areas

DDT及其降解产物DDD、DDE的相对含量和HCHs各异构体(α-HCH,β-HCH,γ-HCH,δ-HCH)的比例常被用于研究环境中OCPs的代谢情况和污染源的分析.自然环境中的DDT有两种归宿[34],视好氧环境和厌氧环境的不同,DDT可分别被相应的好氧或厌氧微生物降解为DDE和DDD,一般以DDE与DDD之和相对DDT的含量[m(DDE)+m(DDD)]/m(DDTs)作为判断有无新污染源进入水体的指标(>0.5).进一步分析表 1数据发现,p, p′-DDT和p, p′-DDE均未被检出,仅有少量p, p′-DDD在BY3(杨家淀)和BY11(烧车淀湿地)处发现,表明白洋淀底泥中的DDTs污染来源为历史残留,无新DDT污染源输入,且底泥中DDT降解主要为厌氧降解.

HCHs与Dieldrin是本研究中的主要污染物,环境中的HCHs主要来源于工业生产的六六六和林丹产品,一般工业六六六中α-HCH比重为60 % ~70 %,β-HCH比重为5 % ~12 %,γ-HCH比重为10 % ~15 %,δ-HCH比重为6 % ~10 %,而林丹中99 %为γ-HCH.故研究中常用α-HCH与γ-HCH的比值m(α-HCH)/m(γ-HCH)来估计污染点处HCHs的来源[35]m(α-HCH)/m(γ-HCH)在4~7之间认为是工业六六六残留的结果,而当m(α-HCH)/m(γ-HCH)小于1趋近0时则认为该处污染源自林丹的输入.同时,HCHs的4种单体中β-HCH的物理化学性质最为稳定,其他3种环境中的HCH单体会随时间向β-HCH转化,较高的β-HCH含量可表明环境中无新的HCHs污染源进入.

从白洋淀11处采样点沉积物中各HCH异构体比例分布(图 3)可知,苲淀、荷花淀、杨家淀、鸳鸯岛、烧车淀中心、郭里口和烧车淀湿地处的m(α-HCH)/m(γ-HCH)范围在0.07~0.35之间,均趋近于0,说明该7处地区的HCHs输入以林丹为主.进一步分析该7处地区,杨家淀和烧车淀湿地两处的β-HCH含量(19.8 %和47.5 %)均较工业产品中的β-HCH含量(5 % ~12 %)高,表明这两处区域的HCHs污染主要为历史残留,而其余5处地区均无β-HCH检出,对比2008年Dai等[36]得到的白洋淀底泥中较高β-HCH的调查结果,白洋淀地区可能存在新的林丹的使用,在高秋生等[33]最近对白洋淀底泥的研究中亦有类似的发现.其余4处采样点(光淀、李朗村、烧车淀河道和大观园地区)沉积物中均无γ-HCH检出且HCHs异构体以α-HCH为主,表明这4处地区的HCHs主要来源于工业六六六的污染. 四处采样点中李朗村和烧车淀河道检出高比例的β-HCH含量(80.6 %和48.8 %),表明该地区无新的HCHs污染,而光淀和大观园地区则无β-HCH检出,表明可能存在新的工业六六六输入.综上所述,白洋淀11处采样点有7处受林丹污染,4处受工业六六六污染,其中有7处采样点附近区域可能存在新的HCHs类农药的使用.

图 3 白洋淀表层沉积物中HCHs异构体组成 Fig.3 Percentage composition of HCHs in surficial sediments from Lake Baiyangdian

在污染源分析中,主成分分析(PCA)方法应用较为广泛.利用Origin 9软件对白洋淀11处采样点检出的10种OCPs进行主成分分析,前两个主成分PC1和PC2的方差解释量分别为45.55 %和21.11 %,总方差解释量达到66.66 %,结果如图 4所示.由图 4可知,BY5(鸳鸯岛)和BY8(烧车淀中心)污染情况相似;BY1(窄淀)、BY2(荷花淀)、BY4(光淀)和BY10(大观园)污染情况相似;BY6(李朗村)和BY7(烧车淀河道)污染情况相似,这代表这些区域间可能存在相同的污染源或具有相互扩散的可能,而BY3(杨家淀)、BY9(郭里口)和BY11(烧车淀湿地)与其他淀的污染特征有较大差异.从总体上分析,各点位在PCA图上没有显著的聚类归一现象,这可能说明白洋淀OCPs农药种类使用并不统一.

图 4 白洋淀表层沉积物中OCPs主成分分析 Fig.4 Principal component analysis of OCPs in surficial sediments from Lake Baiyangdian
2.2 白洋淀表层沉积物中PCBs分布特征及源分析

209种PCB单体在白洋淀11处采样点表层沉积物中共检出24种,总PCBs含量在nd~ 37.61 ng/g之间,平均含量为13.45 ng/g.各采样点处PCBs种类和总含量见图 5附录Ⅳ,其中BY11(烧车淀湿地)处总PCBs含量最高,为37.61 ng/g,该地检出的PCB单体及同系物种类也最多,PCBs污染严重;BY3(杨家淀)和BY5(鸳鸯岛)位居第2、3,分别为29.27和24.30 ng/g,其余地区总PCBs含量较前三者低,而BY6(李朗村)低于检测限.

图 5 白洋淀表层沉积物中检出的PCBs单体及含量分布 Fig.5 Distribution of PCB congeners detected and content in surficial sediment from Lake Baiyangdian

多氯联苯同系物组成常用来分析环境中PCBs的分布、来源和归宿.本研究白洋淀地区表层沉积物中PCBs以低氯联苯为主,一氯联苯最多,占总量的31.16 %,二氯联苯和三氯联苯其次,分别占总量的17.60 %和15.97 %,四氯联苯含量占总量的11.49 %.高氯联苯中六氯联苯居多,占总量的12.55 %,五氯联苯相对含量仅为总量的5.3 %,七氯联苯为4.6 %,其余高氯联苯含量可忽略不计(图 6).中国在1980s前生产的PCBs商品多以三氯联苯和五氯联苯为主,其中三氯联苯主要用于电容器,而五氯联苯多用于油漆. Dai等[36]在2008年对白洋淀地区沉积物PCBs的调查中发现,白洋淀沉积物中PCBs以高氯联苯为主(五氯联苯和六氯联苯占总量的65 %),并推测船底油漆是白洋淀地区主要的PCBs污染来源.对比10年前白洋淀沉积物中PCBs分布情况的调查结果[36],一氯、二氯联苯等低氯联苯含量明显增多而高氯联苯五氯、六氯联苯含量明显减少,这一结果表明白洋淀沉积物中可能存在微生物脱氯现象.结合国内PCBs商品生产状况,五氯、六氯联苯含量的大幅度减少以及五氯联苯较低的相对含量在一定程度上可以说明白洋淀地区PCBs污染情况好转且无新的污染源输入.

图 6 白洋淀表层沉积物中PCBs同系物百分比组成 Fig.6 Percentage composition of PCBs homologues in surficial sediment from Lake Baiyangdian

国内外部分研究地区沉积物中PCBs污染情况见表 3.国外发达国家水体沉积物中PCBs含量普遍较高,白洋淀PCBs含量远低于美国历史上PCBs污染严重的哈德逊河和格拉斯河,与国外研究地区相比,白洋淀PCBs含量也处于低等水平.与国内其他地区进行比较,白洋淀PCBs含量较太湖、黄海、滇池等地高,与珠江三角洲流域、长江口及东海近岸和太湖竺山湾及入湖河流等处相比PCBs含量较低.总体来说,白洋淀沉积物中PCBs含量在全国范围内处于中等水平,PCBs含量与2011年白洋淀调查时无明显差异,但PCB单体种类减少.

表 3 国内外不同地区表层沉积物中PCBs含量比较 Tab. 3 Comparison of PCBs content in surficial sediments from different areas
2.3 白洋淀表层沉积物中PCBs风险评估

因部分OCPs缺乏标准值,白洋淀10种检出的OCPs中,仅评估γ-HCH、Dieldrin和p, p′-DDD,其余OCPs暂不进行风险评估,结果如表 4所示.

表 4 白洋淀表层沉积物中OCPs和PCBs生态风险评估 Tab. 4 Ecological risk of OCPs and PCBs in surficial sediments from Lake Baiyangdian

对于p, p′-DDD,仅有两处采样点含量位于ERL值与ERM值之间,其余均低于ERL值,表明白洋淀表层沉积物中p, p′-DDD生态风险较低,只杨家淀、大观园两处存在一定毒性风险;对于Dieldrin,烧车淀湿地采样点处含量高于ERM,存在较大可能的生态风险,同时大部分采样点处的Dieldrin含量位于ERL值与ERM值之间,均存在一定毒性风险,尚需进一步关注;对于γ-HCH,白洋淀沉积物中γ-HCH生态风险较高,11处采样点中有7处采样点的γ-HCH含量高于PEL值,不容忽视;对于∑PCBs,8处采样点的总PCBs含量低于ERL值,3处采样点含量介于ERL值与ERM值之间,生态风险较低.整体mERMq值为1.37,大于0.5而小于1.5,表明白洋淀研究区域的总体生态风险程度为中,需要重视.

3 结论

1) 白洋淀表层沉积物中共检出10种OCPs,总含量在1.22~52.45 ng/g之间,在国内处中等水平,HCHs和Dieldrin为其主要污染物. HCHs组成分析发现白洋淀地区可能存在新的HCHs污染源输入.

2) 白洋淀表层沉积物中共检出24种PCB单体,总含量在nd~37.61 ng/g之间,较国外地区污染程度低,在国内处中等水平.目前PCBs分布以低氯联苯为主,沉积物中低氯联苯含量大幅度上升而高氯联苯含量大幅度下降,白洋淀地区PCBs污染程度减轻,无新的污染源输入且可能存在微生物脱氯现象.

3) 白洋淀沉积物中,p, p′-DDD和∑PCBs生态风险较低,仅个别地区存在一定毒性风险需关注;Dieldrin尚需关注;γ-HCH在多数地区含量均高于PEL值,存在较高的生态风险.

4 附录

附录Ⅰ~见电子版(DOI:10.18307/2020.0306).

附录Ⅰ OCP的保留时间与回收率 Appendix Ⅰ Retention time and recovery of OCPs
附录Ⅱ PCB单体的保留时间与回收率 Appendix Ⅱ Retention time and recovery of PCBs
附录Ⅲ 白洋淀沉积物中OCPs含量* Appendix Ⅲ Content of OCPs in sediments from Lake Baiyangdian
附录Ⅳ 白洋淀表层沉积物中检出的PCBs单体及含量 Appendix Ⅳ Distribution of PCB congeners detected and content in surficial sediment from Lake Baiyangdian
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