环境科学  2019, Vol. 40 Issue (1): 228-238   PDF    
黄河中游(渭南-郑州段)全/多氟烷基化合物的分布及通量
李琦路1,2, 程相会1, 赵祯3, 郭萌然1, 袁梦1, 华夏3, 方祥光3, 孙红文3     
1. 河南师范大学环境学院, 黄淮水环境与污染防治教育部重点实验室, 河南省环境污染控制重点实验室, 新乡 453007;
2. 中国科学院广州地球化学研究所, 有机地球化学国家重点实验室, 广州 510640;
3. 南开大学环境科学与工程学院, 环境污染过程与基准教育部重点实验室, 天津 300350
摘要: 本研究收集黄河中游(渭南-郑州段)表层水样品,利用高效液相色谱质谱串联的方法分析了水相和颗粒相中的28种全氟和多氟烷基化合物(PFASs).结果表明,水相和颗粒相中∑28PFASs的含量分别为18.4~56.9 ng·L-1和26.8~164 ng·g-1(以干重计).水相和颗粒相中以全氟己酸(PFHxA)为主要污染物,分别占总含量的27%和16%,且3H-全氟-3-(3-甲氧基丙氧基)丙酸(ADONA)、氯代多氟醚基磺酸(6:2和8:2 Cl-PFESA)在颗粒相均有检出,表明PFASs替代品的生产和使用逐渐增多.PFASs在水相-颗粒相中的lgKd变化范围为2.95±0.553(PFPeA)~3.85±0.237(8:2 FTUCA),颗粒物吸附氟调聚羧酸(FTCAs)和不饱和氟调聚羧酸(FTUCAs)的能力随碳链长度的增长而增加,全氟烷基磺酸(PFSAs)较全氟烷基羧酸(PFCAs)更容易被颗粒物吸附.黄河郑州-渭南段PFASs的通量呈现先降低后增加的趋势,表明该河段接纳了来自上游及支流的污染输入.此外,结果表明水相中的PFASs通量大于颗粒相.
关键词: 全/多氟烷基化合物(PFASs)      黄河      替代品      分配系数      通量     
Distribution and Fluxes of Perfluoroalkyl and Polyfluoroalkyl Substances in the Middle Reaches of the Yellow River (Weinan-Zhengzhou Section)
LI Qi-lu1,2 , CHENG Xiang-hui1 , ZHAO Zhen3 , GUO Meng-ran1 , YUAN Meng1 , HUA Xia3 , FANG Xiang-guang3 , SUN Hong-wen3     
1. Key Laboratory for Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang 453007, China;
2. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;
3. Key Laboratory of Pollution Processes and Environment Criteria, Ministry of Education, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
Abstract: Surface water samples were collected in the middle reaches of the Yellow River (Weinan-Zhengzhou section) and all 28 perfluoroalkyl and polyfluoroalkyl substance (PFAS) levels were measured using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results show that the levels of PFASs in the water and particle phase are 18.4-56.9 ng·L-1 and 26.8-164 ng·g-1, respectively. Perfluorohexanoic acid (PFHxA) in the water and particle phases is the main pollutant, accounting for 27% and 16% of the total concentrations, respectively, and 3H-perfluoro-3-[(3-methoxy-propoxy)-propanoate] acid (ADONA) and chlorinated polyfluorinated ethersulfonic acids (6:2 and 8:2 Cl-PFESA) were detected in the particle phase, indicating that the use of PFAS alternatives gradually increases. The lgKd of PFASs between the water and particle phase ranges from 2.95±0.553 (PFPeA) to 3.85±0.237 (8:2 FTUCA)and the adsorption of fluorotelomer carboxylic acids (FTCAs) and fluorotelomer unsaturated carboxylic acids (FTUCAs) on particulate matter increases with increasing of carbon chain length. Perfluoroalkane sulfonic acids (PFSAs) are more easily adsorbed by particulate matter than perfluoroalkyl carboxylic acids (PFCAs). The fluxes of PFASs in the Weinan-Zhengzhou section of the Yellow River show a decrease at first and then increase, indicating that this section receives pollution inputs from the upstream and tributaries. In addition, the results show that the fluxes of PFASs in the water phase are greater than those in the particle phase.
Key words: perfluoroalkyl and polyfluoroalkyl substances (PFASs)      Yellow River      alternative      partition coefficient      flux     

全氟和多氟烷基化合物(perfluoroalkyl and polyfluoroalkyl substances, PFASs)是一类人工合成的化合物, 因其良好的疏水、疏油特性而被广泛应用于纺织、造纸、化工和灭火剂等生产领域[1].全氟辛烷磺酸(perfluorooctane sulfonate acid, PFOS)和全氟辛酸(perfluorooctanoic acid, PFOA)是两种应用最广泛的PFASs, 具有较强的毒性及潜在的致癌性, 可对生物体造成急性和亚慢性毒性作用[2]. 2006年, 美国环保署联合全球8家PFOA生产公司承诺到2015年停止PFOA的生产[3]. 2009年, 斯德哥尔摩缔约方大会将PFOS及其盐类列入附件B并在全球限制使用[4], 之后在2015年通过了PFOA及其盐类和相关化合物的附件D审查(POPs特性筛选), 认为PFOA符合附件D筛选标准, 决定在其附件E审查时应纳入可降解为PFOA的盐类和相关化合物[5]. C8被禁用后, 一些具有较低的生物富集性[6]和毒性[7, 8]的替代品受到广泛关注[9], 如全氟己酸(perfluorohexanoic acid, PFHxA)[6]、全氟醚基烷酸(perfluoroalkyl ether sulfonic acids, PFESAs)[10]、三氟乙酸(trifluoroacetic, TFA)和全氟聚醚类[perfluoropolyethers, PFPEs:CF3O(CF2)3OCHFCF2COOH(ADONA)和CF3(CF2)2OCF(CF3)COOH(HFPO-DA)], 目前已在多个流域的水环境中检出[10~12].

截止到2004年, 直接或间接释放到环境中的PFASs含量为3 200~7 300 t[13]. PFASs在大气[4]、水体[13]、沉积物[14]、土壤[15]及生物体[16]等多种环境介质中均有不同程度的检出.由于具有较高的水溶性、较低的蒸气压和较强的表面活性, 离子型的全氟烷酸(PFAAs)多分布在水环境中[13].进入水体的PFASs可被水生生物摄入体内转移至食物网并随食物链累积[17].河流不仅在全球地球化学循环中起着关键作用, 也为人类生存提供必须的水资源.它是人类排污的主要场所, 是将污染物从大陆向海洋输送的重要途径[18].因此, 了解PFASs在河流中的分布特征及污染来源极为重要.黄河是华北地区重要的饮用水、农业用水和工业用水水源, 黄河渭南—郑州段流经人类活动密集的中原城市群.随着流域内经济的快速发展, 工业化程度提高, 黄河每年接纳的废水量为9.23亿m3, 以有机污染物为主[19].本研究分析了黄河渭南—郑州段表层水体水相及颗粒相中的28种PFASs, 阐述PFASs的分布特征, 并估算了流域通量.

1 材料与方法 1.1 试剂与药品

甲醇(色谱级)、丙酮(色谱级)、氢氧化铵(25%, 体积比)购自德国Merck公司, 玻璃纤维滤膜(glass fibre filter, GFF, GF/C, Φ 47 mm, 1.2 μm)购自美国Whatman公司. 28种目标化合物包含PFCAs(TFA、PFPrA、PFBA、PFPeA、PFHxA、PFHpA、PFOA、PFNA、PFDA、PFUnA和PFDoDA)、PFSAs(PFBS、PFHxS和PFOS)、FTCAs(3:3、5:3、7:3、6:2和8:2 FTCA)、FTUCAs(6:2和8:2 FTUCA)、PFESAs(Cl-6:2和Cl-8:2 PFESA)、PFPEs(ADONA和HFPO-DA)和diPAP(6:2、8:2和10:2 diPAP), 和9种同位素标记内标(internal standard, IS)的具体信息见表 1.所有标准物质购自加拿大Wellington实验室, 纯度大于98%. HPLC级水购自美国Fisher公司. Millipore水由Milli-Q PLUS 185系统(德国)制备. Oasis系列弱阴离子交换柱(WAX, 150 mg, 6 mL, 30 μm)购自美国Waters公司. Envi-Carb柱(3 mL, 0.25 g)购自Supelco公司.

表 1 目标化合物和内标化合物全称、缩写及特征离子 Table 1 Full names, abbreviations and characteristic ion of the target compound and standard chemicals

1.2 样品采集

2016年4月, 在渭南(WN, 110°19′35.05″E, 34°36′17.00″N)、三门峡(SMX, 111°07′54.95″ E, 34°47′27.53″ N)、小浪底镇(XLDZ, 112°20′33.07″ E, 34°57′40.52″ N)、大峪镇(DYZ, 112°21′27.54″ E, 34°56′17.70″ N)、坡头镇(PTZ, 112°30′52.23″ E, 34°54′51.55″ N)和郑州(ZZ, 113°42′09.03″, 34°54′48.64″ N)布设6个采样点(见图 1), 每个样点采集3个体积为1 L的表层水样(0~1 m), 共18个样品.河水使用甲醇预洗的不锈钢采水器采集, 收集在甲醇预洗的聚丙烯(polypropylene, PP)瓶中, -20℃下保存至进一步处理.

图 1 黄河渭南—郑州段样点分布示意 Fig. 1 Sampling stations in the Weinan-Zhengzhou section of the Yellow River

1.3 样品前处理

利用抽滤装置将颗粒相截留在GFF上.水相使用固相萃取法(solid-phase extraction, SPE)提取PFASs.萃取柱使用前用10 mL的甲醇和10 mL的Millipore水活化.样品萃取前加载5 ng (500 μg·L-1, 10 μL)内标, 由改造的分液漏斗控制流速1~2滴·s-1, 依靠重力富集到SPE柱上.分别用5 mL甲醇和5 mL 0.1%氢氧化铵甲醇溶液洗脱萃取柱, 洗脱液氮吹浓缩至150 μL.滤膜使用前在马弗炉中450℃灼烧12 h.加载样品后的滤膜在-50℃下冷冻干燥72 h, 之后置于PP离心管超声萃取.离心管中加入10 mL甲醇和5 ng(500 μg·L-1, 10 μL)IS, 于摇床振荡20 min后超声15 min.在4 000 r·min-1条件下离心10 min, 转移上清液至50 mL的PP管中, 重复两次.萃取液氮吹(>99.99%)浓缩至2 mL, 经10 mL甲醇活化的Envi-Carb柱净化, 氮吹浓缩至150 μL.仪器分析前添加13C2-8:2 FTUCA(5 ng)作为进样内标.

1.4 仪器分析

分析仪器为安捷伦1260液相色谱仪串联安捷伦6460三重四级杆质谱联用仪(HPLC-MS/MS, Agilent Technologies, 美国). C2~C4-PFCAs使用RSpak JJ-50 2D离子交换柱(150 mm×2 mm, 5 μm, CNW, 德国)进行分离.进样体积为10 μL, 流动相为体积比1:4的20% pH=9的50 mmol·L-1 CH3COONH4与甲醇混合溶液.流动相的流速是250 μL·min-1. C5~C12-PFCAs、PFSAs、FTCAs、FTUCAs、PFESAs、PFPEs及diPAPs使用X-terra MS C18色谱柱(150 mm×2.1 mm, 5 μm; Waters, 爱尔兰)进行分离.进样体积为10 μL.流动相分别为含2.5 mmol·L-1醋酸铵缓冲剂的Millipore水(A)和含2.5 mmol·L-1醋酸铵缓冲剂的甲醇(B).梯度洗脱:起始流动相为10%B, 0~0.8 min逐渐升至60%B, 0.8~12.8 min逐渐升至100%B, 12.8~14.3 min逐渐恢复到初始状态.质谱条件为电喷雾离子源(electrospray ionisation, ESI), 负离子化多反应监测模式(multiple reaction monitoring, MRM), 雾化器电压、温度和气流流速分别为-4 500 V、350℃和10 L·min-1, 气帘流速为8 L·min-1, 停留时间为15 ms[4].质谱的特征离子见表 1.

1.5 加标回收率

向1 L的HPLC级水中加入5 ng目标化合物标准品(PFCAs、PFSAs、FTCAs、FTUCAs、PFESAs、PFPEs和diPAPs)和IS(13C-标记的C2-、C4-和C8-PFCAs、C8-PFSA、8:2 FTUCA、HFPO-DA、6:2和8:2 diPAPs、18O-标记的C6-PFSA)进行加标回收率方法实验, 分别为水样萃取前加入目标化合物标准品和IS(前加标), 水样测定前加入目标化合物标准品和IS(后加标)及水样萃取前只加IS(不加标), 每组实验设3个平行样, 目标化合物的回收率计算公式如下:

(1)
(2)

式中, AS1、AS2和AS3分别为前加标、不加标和后加标组中标准品的响应面积. BS1和BS2分别为前加标和后加标组中内标的响应面积. 28种目标化合物的方法回收率在45%±15%(8:2 diPAP)~108%±13%(PFHxS)之间, 具体数值见表 2, 内标的方法回收率在36%±22%(13C3-8:2 diPAP)~116%±19%(18O2-PFHxS)之间.

表 2 目标化合物的IQLs、MQLs及回收率 Table 2 IQLs, MQLs, and recoveries of target analytes

1.6 质量控制和质量保证

本实验器皿均采用玻璃和PP材质, 但玻璃材质容易吸附PFASs[20], 应尽可能地避免使用, 对于无法避免的玻璃材质的过滤装置应在250℃下烘烤12 h, 使用前用Millipore水和甲醇润洗内壁, 过滤后用少量Millipore水和甲醇淋洗并收集. PP材质器皿事先用甲醇与水的混合液超声30 min, 然后用甲醇溶液超声30 min, 接触样品前用甲醇淋洗内壁3次.在采样过程中设置3个野外空白, 在样品处理过程中设置3个过程空白.标准曲线的浓度梯度为0、0.5、1、2、5、10、20、50、100和200 μg·L-1, 在标准曲线浓度范围内, 线性相关系数均大于0.993.仪器定量限(instrument quantification limits, IQLs)利用3倍的信噪比确定.方法定量限(method quantification limits, MQLs)利用10倍的信噪比确定.水相及颗粒相中28种PFASs的IQLs和MQLs列于表 2. C3~C4-PFCAs、C6~C7-PFCAs和PFSAs在颗粒相及水相空白中检出, 含量(以干重计)分别为 < MQL~0.9 ng·L-1和 < MQL~0.3 ng·g-1(以干重计), C2-PFCAs在空白中检出含量较高, 分别为10 ng·L-1及7 ng·g-1, 所有实验结果为经过空白修正后再使用内标校正法进行定量分析.

2 结果与讨论 2.1 PFASs的含量、组成及空间分布 2.1.1 水相中的PFASs

水相中有24种PFASs检出, 其中TFA、PFHxA、PFOA、PFNA、PFDA、PFHxS、PFOS、8:2 FTUCA和Cl-6:2PFESA的检出率为100%. Σ28PFASs的浓度为18.4~56.9ng·L-1, 平均值为(35.8±9.51)ng·L-1(表 2). Σ28PFASs最高浓度在坡头镇(PTZ)检出[(43.0±12.2)ng·L-1]. PFHxA是水相中的主要污染物, 浓度为(9.82±3.87)ng·L-1, 占总浓度的27%(图 2), 其作为C8的替代品广泛应用于服装、地毯及家具等产品中[21, 22].新型PFASs在水相中均有检出. 6:2和8:2 Cl-PFESA的浓度分别为(2.49±1.62)ng·L-1和(0.005 19±0.011 4)ng·L-1. 6:2和8:2 Cl-PFESA是铬雾抑制剂F-53B的主要成分, 多应用于电镀行业[23].本研究中6:2 Cl-PFESA浓度与PFOA[(3.31±3.57)ng·L-1]和PFOS[(3.44±1.70)ng·L-1]的浓度处于同一水平, 由此可见, 电镀行业的兴盛和发展带来的PFASs污染问题应当引起重视[24].该河段6:2/8:2 Cl-PFESA的比值为264±98.4, 显著高于商品中两种同系物的比值(12.9±2.6)[8], 这可能与不同PFESAs在环境中的物理化学性质及环境行为的差异有关[8]. ADONA和HFPO-DA可作为全氟辛酸铵(ammonium perfluorooctanoate, APFO)的替代物用作氟聚物工业生产过程中的乳化剂[25].本研究ADONA和HFPO-DA的浓度均低于检出限, 显著低于德国阿尔兹河中ADONA的浓度[(0.32~6.2)μg·L-1][26]和我国小清河中HFPO-DA的浓度(n.d.~3.1 μg·L-1)[25], 表明流域内氟聚物工业生产过程中的乳化剂的排放处于较低水平.

图 2 黄河渭南—郑州段水相中PFASs的浓度和组成 Fig. 2 Concentrations and compositions of PFASs in the water phase from the Weinan-Zhengzhou section of the Yellow River

2.1.2 颗粒相中的PFASs

颗粒相中27种PFASs均有检出, TFA、PFPrA、PFBA、PFPeA、PFHxA、PFOA、PFUnA、PFHxS、PFOS、8:2 FTCA和8:2 FTUCA的检出率为100%. Σ28PFASs的含量(以干重计, 下同)为26.8~164 ng·g-1, 平均值为(74.7±35.9)ng·g-1(见表 2), 高于大连湾中Σ17PFASs的含量(3.5~22.2 ng·g-1)[27]. Σ28PFASs最高值在大峪镇检出(DYZ, 108±49.8 ng·g-1). DYZ位于小浪底水库中, 可能接受了上游河流的输入.河水进入库区后, 流速降低, 大粒径颗粒沉降, 颗粒物以富含有机质的小粒径悬浮颗粒物为主[28, 29], 有利于PFASs的吸附[30].

颗粒相中PFHxA是主要污染物, 含量为(12.2±7.77)ng·g-1, 占总含量的16%(图 3).前体物FTCA及一些新型PFASs在颗粒相中均有检出.大峪镇(DYZ)8:2 FTCA的含量[(23.6±5.99)ng·g-1]较高. FTCAs没有直接排放源, 来自于前体物FTOHs的降解[31, 32]. Ellis等[33]报道大气中FTOHs降解的中间产物(FTCAs等)可附着在大气颗粒上, 而后沉降到河流中, 是离子型PFASs的间接源[13].三门峡(SMX)和小浪底镇(XLDZ)检出较高含量的6:2 diPAP, 分别为(49.1±16.0)ng·g-1和(18.9±6.85)ng·g-1. diPAPs主要应用于与食品接触的纸质包装材料及润湿剂中, 在污水处理厂及纸纤维中检测到diPAPs的存在[34].分布在河南省的多家包装材料生产厂家可能是diPAP的主要污染源[35]. 6:2 Cl-PFESA和8:2 Cl-PFESA的检出含量为(2.91±3.90)ng·g-1和(0.036 3±0.110)ng·g-1. 6:2/8:2 Cl-PFESA的比值为31.4±30.5, 低于水相中的结果, 这可能是因为PFASs的疏水性随碳链长度增加而增强[8].

图 3 黄河渭南—郑州段段颗粒相中PFASs的含量和组成 Fig. 3 Contents and compositions of PFASs in the particle phase from the Weinan-Zhengzhou section of the Yellow River

2.2 含量对比

本研究发现黄河呼和浩特段水相中Σ7PFASs(PFHpA、PFOA、PFNA、PFDA、PFDoDA、PFHxS和PFOS)浓度为(1.8±0.15)ng·L-1, 山西境内为(4.8±1.8)ng·L-1[36], 低于本研究中相同的7种PFASs的浓度[(11.2±4.50)ng·L-1]. 2011年, Zhao等[14]分析了黄河中下游水相中的11种PFASs污染水平, 短链PFASs(PFBS、PFBA、PFPeA、PFHxA和PFHpA)和长链PFASs(PFOS、PFOA、PFNA、PFDA、PFUnA和PFDoDA)的浓度分别为44.7 ng·L-1和1.52 μg·L-1, 均高于本研究水相中相同PFASs短链[(15.3±4.84)ng·L-1]和长链[(8.05±3.56) ng·L-1]的浓度(表 3).本研究水相中PFOA浓度范围是0.459~12.7 ng·L-1[(3.32±3.67)ng·L-1], 与莱茵河PFOA的浓度处于同一水平[(4.8±1.0)ng·L-1][25], 但低于辽河(12.0 ng·L-1)[37]、海河(15 ng·L-1)[38]、长江(2.0~260 ng·L-1)[39]和多瑙河(25 ng·L-1)[40]流域中PFOA的浓度.本研究水相中PFOS浓度为1.21~6.05 ng·L-1[(3.45±1.33)ng·L-1], 显著低于黄河河口(82.30~261.8 ng·L-1)[41]和塞纳河(97 ng·L-1)[40]水相中PFOS的浓度.

表 3 水相和颗粒相中PFASs的含量 Table 3 Contents of the target compounds in the water and particle phases

Zhao等[14]分析黄河中下游颗粒相中11种PFASs的污染水平, 短链PFASs(PFBS、PFBA、PFPeA、PFHxA和PFHpA)含量为3.44 ng·g-1, 长链PFASs(PFOS、PFOA、PFNA、PFDA、PFUnA和PFDoDA)含量为14.7 ng·g-1, 均低于本研究颗粒相中的短链[(22.3±14.8)ng·g-1]及长链[(13.1±11.7)ng·g-1]的含量.黄河渭南—郑州段颗粒相中PFOA含量范围是0.663~4.97 ng·g-1[(2.73±1.33)ng·g-1], 低于辽河(30 ng·g-1)和太湖(13 ng·g-1)[37]中PFOA的含量, 但与大连湾(1.8 ng·g-1)[27]及黄河[(2.78±1.43)ng·g-1][14]中PFOA的含量处于同一水平.本研究颗粒相中PFOS含量为1.19~33.6 ng·g-1[(7.20±7.75)ng·g-1], 高于大连湾(3.3 ng·g-1)[27]和黄河[(0.252±0.178)ng·g-1]颗粒相中PFOS的含量, 但低于太湖中PFOS的含量(23 ng·g-1)[37].

2.3 PFASs在水-颗粒相中的分配

污染物在水相和颗粒相的分配系数Kd可由如下公式计算:

(3)

式中, cs(ng·kg-1)是PFASs在颗粒相中的含量, cw(ng·L-1)是PFASs在水相中的含量. Kd(L·kg-1)为污染物在水相和颗粒相的分配系数.

表 4可知, 水体主要PFASs的lgKd变化范围为2.95±0.553(PFPeA)~3.85±0.237(8:2 FTUCA). PFOA的lgKd值为2.89±0.524, 高于海河中PFOA的lgKd值(2.1±0.4)[38]. PFOS的lgKd值为3.21±0.363高于辽河(3.06±0.56)中PFOS的lgKd[42]. PFOS比PFOA高0.32个lg单位, PFBS比PFBA高0.04个lg单位, 表明磺酸基团的存在是影响PFASs在颗粒物上吸附的重要因素[9]. n :3 FTCA、n:2 FTCA及n:2 FTUCA呈现随碳链长度的增加而增加的趋势. 6:2 Cl-PFESA和ADONA的lgKd值为3.03±0.488和3.23±0.659, 分别与TFA(3.01±0.538)和PFOS(3.21±0.363)的lgKd值接近. PFCAs的lgKd值没有呈现随碳链长度增加而增加的趋势, 且lgKd与lgKow值没有显著相关. PFASs在水相和颗粒相的分配受颗粒物粒径及有机碳含量的影响[42]; 水体的pH值、Ca2+、盐度、水温及电导率也会影响PFASs的分配[9].

表 4 PFASs在水和颗粒相间的lgKd和lgKow Table 4 The lgKd and lgKowvalues of PFASs between water and particle phase

2.4 通量

PFASs的年通量的计算方程如下[44]

(4)

式中, FW+PFWFP分别是水体、水相及颗粒相中PFASs的年通量(t·a-1), cW(ng·L-1)和cP(ng·g-1)是水相和颗粒相中PFASs的含量, fP(g·L-1)指颗粒物的含量, Q(亿m3)是河水年径流量[45].

表 5可知, PFASs的年通量呈现先下降后上升的趋势.渭南[WN, (0.773±0.151)t·a-1]到三门峡[SMX, (0.573±0.128)t·a-1]的F值呈下降趋势.渭南以西河段有渭河和汾河汇入, 分别为黄河第一和第二大支流.两条河流流经陕西省和山西省, 常年接纳大量的纺织、造纸废水及城市污水[46, 47], 是水中PFASs的主要来源[48].三门峡到郑州[ZZ, (0.866±0.184)t·a-1]的F值呈上升趋势.该河段通量的增加主要来自于支流的汇入[49].洛阳市工业发达, 沿岸有消防药剂厂、污水处理厂及造纸厂等企业分布, 流经洛阳市的洛河接收PFASs并输入黄河.渭南到三门峡的PFASs通量呈现降低趋势, 这可能是由于水库阻碍了PFASs的输送, 导致部分PFASs被截留在水库段[50].水相中的PFASs通量大于颗粒相, 主要是因为PFASs多分布在溶解相[51].

表 5 黄河渭南—郑州段cwcpfpQ及水相和颗粒相中PFASs的年通量 Table 5 The cw, cp, fp, Q, and the flux of PFASs in the water and particles phases in the Weinan-Zhengzhou section of the Yellow River

图 4可知黄河渭南—郑州段PFASs通量以PFHxA[(0.167±0.054 4)t·a-1]为主, 高于本研究PFOA[(0.067 9±0.066 2)t·a-1]和PFOS[(0.069 9±0.029 6)t·a-1]的通量, 且高于易北河[(71±37)kg·a-1][52]和双台子河(17.9 kg·a-1)[51]的PFHxA通量. PFOA低于双台子河[(83±36)kg·a-1][51]的PFOA通量.渭南PFASs通量以PFOA(0.178 t·a-1)为主, 而其他样点均以PFHxA为主要输入污染物.

图 4 黄河中游7个主要的PFASs物质(水相+颗粒相)年通量的百分比 Fig. 4 Percentage of the annual flux of each site for the seven major PFASs (water+particle phase) in the middle of the Yellow River

3 结论

(1) 水相和颗粒相中Σ28PFASs的含量分别为18.4~56.9 ng·L-1和26.8~164 ng·g-1(以干重计).

(2) 水相和颗粒相中均以PFHxA为主要污染物.

(3) ADONA、PFESAs及diPAPs在颗粒相均有检出.

(4) 黄河渭南—郑州段的上游及支流对该河段PFASs的通量贡献较大.

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