环境科学  2022, Vol. 43 Issue (7): 3562-3574   PDF    
骆马湖表层水和沉积物中全氟化合物赋存特征、来源及健康风险评估
黄家浩1,2, 吴玮1, 黄天寅1, 陈书琴3, 项颂2, 庞燕2     
1. 苏州科技大学环境科学与工程学院, 苏州 215009;
2. 中国环境科学研究院湖泊水污染治理与生态修复技术国家工程实验室, 北京 100012;
3. 安庆师范大学资源环境学院, 安庆 246133
摘要: 通过对骆马湖表层水和沉积物的调查检测, 分析了两类介质中全氟化合物(PFASs)的组分结构和赋存特征, 并运用主成分分析法对表层水中此类物质的来源进行了解析, 运用风险商法评估了此类物质的潜在健康风险, 结果表明, 骆马湖表层沉积物中总计检出14种PFASs, 而其表层水中较之前者多检出1种(PFTeA); 表层水中ρ(∑PFASs)范围为46.09~120.34ng ·L-1, 沉积物中ω(∑PFASs)范围为2.22~9.55ng ·g-1; 表层水中质量分数最高的为PFPeA, 为38%, 沉积物中质量分数最高的为PFBA, 为61%, 骆马湖多介质中PFASs组分均以短链物质为主; 骆马湖表层水中PFASs的高浓度区域集中分布在北部河流入湖口, 其浓度呈现由北向南递减的趋势, 沉积物中PFASs的高含量区域则向南迁移; 骆马湖沉积物中的∑PFASs、PFBA和PFOS的分布情况与沉积物中TOC含量有关; 主成分分析表明骆马湖表层水中PFASs主要来自纺织品阻燃、橡胶品的乳化、食品包装过程和纸类表面处理, 金属电镀行业, 皮革和纺织品制造行业; 骆马湖表层水中PFASs处于较低健康风险水平.
关键词: 骆马湖      全氟化合物(PFASs)      赋存特征      来源解析      健康风险评估     
Characteristics, Sources, and Risk Assessment of Perlyfluoroalkyl Substances in Surface Water and Sediment of Luoma Lake
HUANG Jia-hao1,2 , WU Wei1 , HUANG Tian-yin1 , CHENG Shu-qin3 , XIANG Song2 , PANG Yan2     
1. School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China;
2. National Engineering Laboratory for Lake Pollution Control and Ecological Restoration, Chinese Research Academy of Environmental Sciences, Beijing 100012, China;
3. College of Resource and Environment, Anqing Normal University, Anqing 246133, China
Abstract: Through the investigation and detection of the surface water and sediments of Luoma Lake, the structure and occurrence characteristics of PFASs (perlyfluoroalkyl substances) in the two types of media were analyzed, and the principal component analysis method was used to analyze the characteristics of such substances in the surface water. The source was analyzed, and the potential health risks of such substances were evaluated using the risk quotient method. The results showed that a total of 13 PFASs were detected in the surface sediments of Luoma Lake, and one more species was detected in the surface water (PFTeA); ρ(∑PFASs) in the surface water ranged from 46.09 to 120.34 ng ·L-1, and ω(∑PFASs) in sediments ranged from 2.22 to 9.55 ng ·g-1. PFPeA was the major component in surface water, and the mass fraction of PFPeA was 38%. PFBA was the major component in sediment, and the mass fraction of PFPeA was 61%. The multi-media PFASs in Luoma Lake were mainly short-chain substances; the high concentration area of PFASs in the surface water of Luoma Lake was concentrated and distributed at the mouth of the northern rivers. Its concentration showed a decreasing trend from north to south, and the content of PFASs in the sediments showed a decreasing trend from southwest to northeast. The distribution of ∑PFASs, PFBA, and PFOS in the sediments of Luoma Lake and the TOC content in the sediment were related; the principal component analysis showed that the PFASs in the surface water of Luoma Lake were mainly from textile flame retardant, rubber product emulsification, food packaging processes and paper surface treatment industries, the metal electroplating industry, and leather and textile manufacturing industries. PFASs in the surface water of Luoma Lake were at a relatively low health risk level.
Key words: Luoma Lake      perlyfluoroalkyl substances (PFASs)      occurrence characteristics      source analysis      health risk assessment     

全氟化合物(perlyfluoroalkyl substances, PFASs)是一类人工合成的含氟化合物, 其碳链上的氢原子被氟原子所取代[1].根据基团可以将其分为两大类: 全氟烷基羧酸盐(perfluoroalkyl carboxylic acids, PFCAs) 和全氟烷基磺酸盐(perfluoroalkane sulfonic acids, PFSAs).由于具有很强的碳氟键, 这些分子具有高度的稳定性和抗生物降解性, 因此PFASs具有界面活性、疏水疏油、耐酸和耐高温等独特的理化性质[2~4], 被广泛应用在包括皮革、纸张、衣物的防污处理和消防泡沫灭火器等大量产品中[5].有研究表明PFASs在全球范围内各类环境介质中广泛存在, 如在大气[6, 7]、水体[8~10]、沉积物[11]和生物[12, 13]等环境介质中.当前, PFASs的持久毒性和生物累积性已受到关注[9, 14], 某些代表性物质如全氟辛酸(perfluorooctane sulfonate, PFOS)和全氟辛烷磺酸(perlfuorooctanoic acid, PFOA)分别在2009年和2019年被列为斯德哥尔摩公约新增持久性有机污染物(persistent organic pollutants, POPs).

中国是全球最大的PFASs生产国[15], 而水体既可容纳PFASs, 也会通过各种途径将之再次释放[16], 因此了解PFASs在水环境中的分布特征就显得尤为重要.目前有关PFASs在水体中的赋存特征、源汇关系和风险评价的研究大多集中在经济较发达地区的水体[17~19]和沿海水域[20, 21], 而对地处中国内陆的淮河流域湖泊较少, 如: Cao等[22]对南四湖中表层水和沉积物中PFASs的分布趋势和分配特性进行了研究, Yu等[23]研究了淮河表层水中PFASs的分布特征.骆马湖是南水北调东线工程在淮河流域中的重要节点, 目前针对骆马湖中有机质[24]、重金属[25]和药品及个人护理品(pharmaceuticals and personal care products, PPCPs)[26, 27]等污染研究工作正逐步开展, 但涉及PFASs的研究很少.本研究对骆马湖表层水和沉积物中的14种PFASs进行了调查, 分析了其赋存特征, 评价了其污染情况, 解析了PFASs的污染来源, 并评估了PFASs的健康风险, 以期为骆马湖及其同类水体今后PFASs的研究和管控, 提供决策依据和理论支撑.

1 材料与方法 1.1 研究区概况

骆马湖(34°00′~34°11′N、118°04′~118°18′E)位于江苏省北部, 面积为290 km2, 容积为9.18×108 m3, 汇水面积约1 300 km2, 是淮河流域第三大淡水湖泊、江苏省第四大淡水湖泊, 为宿迁和徐州两市共辖[28].该湖不仅是沂河和中运河洪水的主要调蓄湖泊, 也是宿迁和新沂两市的重要水源地, 同时还是国家南水北调东线输水工程的主要调节湖泊之一, 具有重要的生态地位[29].

1.2 样品采集

采样时间: 2020年9月.

样点布设: 采用网格法布点, 在均匀性基础上兼顾重点, 总计设置32个(图 1).

图 1 骆马湖采样点示意 Fig. 1 Location of sampling sites in Luoma Lake

样品类型和数量: 水样32个, 沉积物31个(12号点地处北部采砂区, 局部水深>20 m, 未能采集沉积物样品).

样品的采集: 水样存放于棕色聚丙烯瓶中, 沉积物样放于聚乙烯自封袋中, 低温保存并及时运回实验室进行预处理.

1.3 试剂及仪器

标准品和内标物质: 高纯度混合标准品PFAC-MXB(native PFCAs and PFSAs solution/mixture)包括: 全氟丁烷磺酸(perfluorobutanoic acid, PFBA)、全氟戊烷羧酸(perfluoropentanoic acid, PFPeA)、全氟己烷羧酸(perfluorohexanoic acid, PFHxA)、全氟庚烷羧酸(perfluoroheptanoic acid, PFHpA)、全氟辛烷羧酸(perfluorooctanoic acid, PFOA)、全氟壬烷羧酸(perfluorononanoic acid, PFNA)、全氟癸烷羧酸(perfluorodecanoic acid, PFDA)、全氟十一烷羧酸(perfluoroundecanoic acid, PFUnDA)、全氟十二烷羧酸(perfluorododecanoic acid, PFDoDA)、全氟十三烷羧酸(perfluorododecanoic acid, PFTrDA)、全氟十四烷羧酸(perfluorotetradecanoic acid, PFTeDA)、全氟丁烷磺酸(perfluorobutane sulfonate, PFBS)、全氟己烷磺酸(perfluorohexane sulfonate, PFHxS)、全氟辛烷磺酸(perfluorooctane sulfonate, PFOS); 高纯度混合碳同位素标记品为MPFAC-MXA(mass-labelled PFCAs and PFSAs Solution/Mixture), 包括: 13C4-PFBA、13C2-PFHxA、13C4-PFOA、13C5-PFNA、13C2-PFDA、13C2-PFUnDA、13C2-PFDoDA、18O2-PFHxS和13C4-PFOS.以上标准品和内标物均购于加拿大Wellington实验室(纯度均高于98%).

试剂和材料: 色谱级甲醇(MeOH)、乙腈(ACN)、醋酸铵(NH4OAc)、甲基叔丁基醚(MTBE)和四丁基硫酸氢铵(TBAS), 购自美国Fisher公司, Milli-Q超纯水, Oasis WAXSPE柱(Waters公司, 美国), 0.22μm聚丙烯滤膜(Pall公司, 美国).

主要实验仪器: 高效液相色谱串联四级杆质谱联用仪(XevoTQD, Waters公司, 美国).

1.4 实验方法

本研究参考Zheng等[30]的方法, 采用固相萃取的方式对表层水进行前处理, 沉积物的前处理通过超声提取、离子对萃取和液液萃取的复合提取方式来完成.

水样前处理: 用6 mL含1%氨水的MeOH、6 mL MeOH和6 mL水依次过柱进行活化, 后加入5 ng相应内标物质到已过滤的样品(1.0 L)中摇匀, 将该水样以3~5 mL·min-1的速度流过WAX柱.上样结束后, 用6 mL浓度为25 mol·L-1(pH=4)的NH4OAc和2 mL MeOH冲洗小柱, 淋洗结束后, 分别用6 mL含体积分数1%氨水的MeOH和含体积分数1%氨水的ACN对目标物质进行洗脱, 然后氮吹至近干, 最后用流动相溶液定容至1 mL, 转移至冻存管等待上机测定.

沉积物前处理: 称取1 g过筛后的沉积物样品, 加入5 ng内标标准品, 摇匀后静置一夜, 然后加入1 mL 0.2 mol·L-1氢氧化钠(NaOH)溶液和1.5 mL ACN进行碱消解, 充分振荡, 超声12 min后, 在4℃的条件下以10 000 r·min-1离心10 min, 转移上层清液至新的15 mL离心管, 重复一次, 合并上层清液.将上层清液氮吹浓缩至2 mL, 向剩余的提取物中加入1 mL 0.5 mol·L-1 TBAS, 用0.2 mol·L-1 NaOH和0.5 mol·L-1 TBAS将pH调至3.6.所得溶液中加入6 mL MTBE进行液液萃取, 振荡摇动5 min, 离心10 min(10 000 r·min-1), 吸取上清液于PP洗脱管中, 萃取两次, 合并提取液.最后氮吹至近干, 用1mL流动相溶液复溶, 转移至冻存管等待上机测定.

1.5 液相色谱/质谱条件

水样和沉积物样的定性定量采用超高效液相色谱串联四级杆质谱联用仪(ACQUITY UPLC-ESI/MS/MS)检测目标化合物, 色谱柱为ACQUITY UPLCTM BEH C18柱(2.1 mm×50 mm, 1.7 μm, 美国Waters公司), 柱温保持35℃, 进样量为20 μL.

液相条件: 流动相A为10mmol·L-1醋酸铵水溶液, 流动相B为10mmol·L-1醋酸铵甲醇乙腈溶液(其中甲醇和乙腈的体积比为8 ∶2), 采用梯度洗脱程序: 初始流动相组成为50%A和50%B, 于0~7 min升至100%B; 7~7.5 min降至50%; 7.5~9 min保持50%B.

质谱条件: 在负离子模式下扫描, 采用多反应检测模式(MRM), 电子喷雾离子源(ESI-), 离子温度保持在120℃, 去溶剂温度为400℃, 以氮气作为锥孔气和脱溶剂气, 其流速分别为50 L·h-1和800 L·h-1.

1.6 质量控制与保障

为确保数据的可靠性, 在实验过程中设置运输空白和方法空白, 每5个样品加入1个平行样品.结果显示所有空白均低于检出限, 平行样品的相对标准偏差范围为: 2.80% ~10.27%.

上机检测时, 每10个样品添加一个溶剂空白和质量控制样品, 配置的标曲浓度范围是0.02~5 ng·mL-1, 精密度(RSD)在3.1% ~8.6%(n=7), 线性系数R均大于0.99, 表层水样品的加标回收率(n=3)为68.2% ~103.9%、沉积物样品的加标回收率(n=3)为65.6% ~90.1%, 均符合实验精度要求.仪器检测限和定量限分别为仪器信噪比的3倍和10倍.表层水样和沉积物样的方法检测限(MDL)和回收率的具体数值见表 1.

表 1 表层水和沉积物样品中PFASs的方法检出限及回收率 Table 1 Method detection limits and recoveries of PFASs in the surface water and sediment samples

1.7 健康风险评估

本研究采用HQ(health risk quotient)法评估骆马湖水体中PFASs的存在对人类健康的潜在风险.该方法基于饮用水中目标化合物的MEC(measured environmental concentration)和DWEL(drinking water equivalent level), 在本研究中, 人的年龄被划分3~6、7~11、12~16、17~19、20~24、25~59和>60等7个类别.为了减少HQ方法的不确定性和HQ值超过1的可能性[31], 基于浓度中值数据和浓度范围的第95%数据中建立的中等和高暴露情景[32].HQ表示人类健康风险水平, 计算公式如下:

(1)
(2)

式中, P为通过饮用水摄入PFASs的占比系数, 取0.2[33]; ADI为接受的每日摄入量[μg·(kg·d)-1]; BW为平均体重(kg), ADI、BW和DWI的参考值如表 2所示; DWI为饮用水摄入量(L·d-1); AB为胃肠道吸收率, 取1[34]; FOE为暴露频率, 取0.96[35].PFASs通常以混合物的形式出现在水环境中.为了评估PFASs对人体健康的危害, 有必要考虑PFASs的累积毒性.根据漏斗假说理论[36], PFASs的累积健康风险方程如下:

(3)
表 2 中国不同年龄/性别组的平均体重(BW)、饮用水摄入量(DWI)和PFASs每日可接受摄入量(ADI) Table 2 Mean body weight (BW), quantity of drinking water intake (DWI), and acceptable daily intake of PFAS values (ADI) for different age/gender groups in China

式中, HQmix为PFASs的累计健康风险值; HQi为第i个PFASs的HQ值; MECi为水体样品中第i个PFASs的环境浓度值(ng·L-1); DWELi为第i个PFASs的饮水当量水平

本研究借鉴Thomaidi等[37]的研究将健康风险评估的等级分为3级: 当HQ≥1时, 说明PFASs对人类健康产生了不可忽视的不利影响; 当0.2≤HQ<1时, 说明存在不确定的风险; 当HQ<0.2时, 说明PFASs对人类健康造成的健康风险可忽略不计[35, 37].

2 结果与讨论 2.1 表层水和沉积物中PFASs的组分特征

在骆马湖表层水中, ρ(∑PFASs)为46.09~120.34ng·L-1(平均值为76.35 ng·L-1), 如图 2所示, 其中PFCAs占比为93.7%, PFASs占比为6.3%, ∑PFCAs浓度远大于∑PFASs浓度.这与陈舒[42]所调查的浙江省羧酸类化合物浓度的平均值是磺酸类的二十多倍的情况相似.

(a)表层水中PFASs浓度, (b)表层水中PFASs质量分数 图 2 骆马湖表层水中PFASs的浓度和质量分数 Fig. 2 Concentrations and mass fraction of PFASs in surface water

根据OECD的定义[43], 碳链长度≥7的PFCAs和碳链长度≥6的PFSAs为长链PFASs.随着学界对长链PFASs危害的认识不断深入, 此类物质的禁用和被短链PFASs的替代已成为必然[44].这种禁用和替代也影响到了此类污染物在环境介质中的赋存状态.由上可知, 骆马湖表层水中短链PFASs质量分数已超过长链PFASs, 在PFASs中达到56.13%.其中PFPeA(C5, 浓度平均值为28.64ng·L-1)已成为主要的PFCAs, PFBS(C4, 浓度平均值为1.98ng·L-1)已成为主要的PFSAs.虽然如此, 骆马湖表层水中长链物质仍不可忽视, PFOA(C8, 浓度平均值为24.69ng·L-1)仍占PFASs总质量的32%.

从组分特征上看, 骆马湖表层水中PFBA质量分数亦高达13%, 处于所有组分中第3位, 这说明该湖已经出现了短链PFASs替代效应, 这与Wu等[19]的研究成果相符.与陈舒[42]的研究结果相比, 骆马湖表层水中PFOS浓度较低, 但PFPeA浓度却处于国内较高水平.这可能是因为近年来6 ∶2FTS已被用作金属电镀行业中PFOS的替代品[45], 而PFPeA是6 ∶2FTS的转化产物之一[46].骆马湖表层水中PFOA浓度水平与太湖、长江和秦淮河南京段相当, 高于韩国六大河流, 远低于氟化工园区直接排放地区[47].

与其他地区相比, 骆马湖表层水中∑PFASs浓度处于世界中等水平, 高于我国太湖、南四湖、淮河流域地表水和韩国六大河流, 与南非瓦尔河浓度相近, 低于我国小清河、白洋淀、长江、秦淮河南京段和美国拉斯维加斯过水区(表 3).

表 3 不同研究区表层水中主要PFASs比较1) Table 3 Comparison of PFASs in surface water of different regions

与表层水相比, 骆马湖沉积物中未能检出PFTeDA, ω(∑PFASs)范围为2.22~9.55ng·g-1(平均值为5.61ng·g-1), 如图 3所示, PFCAs占比降低为90.0%, PFSAs占比升高为10.0%.由此可见, 水体中PFSAs较之PFCAs更易被沉积物吸附.从组分特征上看, 沉积物中PFBA(C4, 含量平均值为3.44ng·g-1), 在PFASs中质量分数高达61%, 略低于武倩倩等[52]在天津市河流沿岸土壤中调查到的质量分数, 其次为PFHxA(C6, 质量分数为8%)、PFOS(C8, 质量分数为8%)和PFTrDA(C13, 质量分数为8%).

(a)沉积物中PFASs含量, (b)沉积物中PFASs质量分数 图 3 骆马湖沉积物中PFASs的含量和质量分数 Fig. 3 Concentrations and mass fraction of PFASs in sediment

沉积物中∑PFASs含量同样处于中等水平, 从全国来看, 高于太湖和南四湖, 与长江和秦淮河南京段的含量相近, 低于小清河和白洋淀.与国外比较来看, 高于韩国六大河流和南非瓦尔河的含量, 低于美国拉斯维加斯过水区含量(表 4).根据齐彦杰[53]的研究结果, 2013年骆马湖沉积物中∑PFASs含量为0.929 ng·g-1, 最主要的化合物是PFOS, 本研究发现, 骆马湖沉积物中PFASs含量较之2013年已经增加了6倍, 且主要化合物已从PFOS转变成了短链PFASs, 这表明骆马湖PFASs污染呈加剧态势且发生了短链的替代.

表 4 不同研究区沉积物中主要PFASs比较1) Table 4 Comparison of PFASs in sediment of different regions

2.2 表层水和沉积物中PFASs空间分布特征

骆马湖表层水中PFASs浓度和质量分数前3的单体组成空间分布特性较为相似(图 4).骆马湖表层水中∑PFASs浓度整体呈现出北部高于南部, 这是因为骆马湖流域内工业企业主要分布在北部的新沂市[54]这与该地区以前研究中报道的其他新型污染物如内分泌干扰物(endocrine disrupting chemicals, EDCs)和药品及个人护理用品(PPCPs)的分布模式相似[27, 55], 这表明北部入湖河流是PFASs主要污染来源.根据已有研究, 表层水和沉积物PFASs分布规律有较大差异[56~58], 这一现象在本研究中亦得到了证实: 骆马湖表层水中∑PFASs、PFPeA、PFBA和PFOA的高浓度区主要出现在北部入湖河流处, 而沉积物中相应的高含量区向南迁移(图 5).

图 4 骆马湖表层水中PFASs分布特征 Fig. 4 Spatial distribution of PFASs in the surface water of Luoma Lake

图 5 骆马湖沉积物中PFASs分布特征 Fig. 5 Distribution characteristics of PFASs in the sediments of Luoma Lake

虽然骆马湖受南水北调的影响[59], 水体对流趋势得到了加强, 但并未完全改变其天然状态下由北向南的流向.故其PFASs进入沉积物存在一定的向南滞后效应.

图 5可知, PFBA和PFHxA在湖区的空间分布特征较为相似, 而PFOS在北部入湖河流处的含量较高, 这可能是因为PFOS为长链PFASs更容易被沉积物吸附[60], 导致其滞后效应变弱.根据齐彦杰[53]的研究, 在受人类活动影响干扰较为强烈地区, PFASs和介质中TOC有较显著的相关性, 骆马湖沉积物中PFASs和TOC的Spearman相关分析结果如表 5所示.

表 5 沉积物中主要PFASs含量和TOC的相关性分析1) Table 5 Correlation analyses among main PFASs content and TOC in sediments

表 5可知, 骆马湖沉积物中TOC含量和PFBA呈极显著正相关(P < 0.01), 和PFOS呈显著正相关(P < 0.05), 而PFHxA含量和TOC的相关性则没有显著的统计学意义(P>0.05), PFASs各组分和TOC的相关性可能是决定其具有不同空间分布规律的重要原因之一.

2.3 表层水中PFASs的潜在来源

源解析对于包括PFASs在内的持久性有机污染物的控制变得越来越重要[18], 然而关于骆马湖中PFASs的来源却仍不清楚.已证明各种PFASs之间的相关性分析可用于推断PFASs的潜在来源[61], 在本研究中表层水的组分特征表明, PFPeA是最主要的化合物, 具有最高的浓度和检出率, 其次是PFBA和PFOA(图 2). Spearman相关分析表明(图 6), PFPeA和PFOS呈显著正相关, PFBA和PFHxA呈显著正相关, PFOA和PFDA、PFHpA、PFHxA呈显著正相关, 表明这些化合物可能共享相似的来源和运输路线[57].据报道, PFHpA/PFOA的比值随着距离非大气源距离的增加而增大, 高比值可能是大气沉降的有效示踪剂, 在城市地区为0.5~0.9, 在偏远地区为6~16[62].在本研究中PFHpA/PFOA均小于1, 说明骆马湖中PFASs的来源不是大气沉降而是直接排放.

*表述在0.01级别, 相关性显著 图 6 骆马湖表层水中单个PFASs浓度的斯皮尔曼相关系数 Fig. 6 Spearman correlation coefficients for individual PFASs concentrations in surface waters of Luoma Lake

KMO和Barlett检验表明, 骆马湖表层水PFASs的KMO值为0.663(>0.6), 球形度检验的P值为0.00(<0.05), 可知本研究数据满足PCA分析的条件.利用PCA/MLR进一步量化PFASs的潜在来源及其贡献[63~65], 结果表明前4个主成分解释了总方差的86.99%(图 7中用不同颜色区别每个因子的主要化合物).由于同组化合物可能来源相似, 骆马湖表层水中的PFASs可能主要来源于4种不同类型的污染源.因子1主要由PFHxA、PFHpA和PFBA组成, 占来源贡献总量的16.94%, PFHxA和PFHpA可被认为是来自皮革和纺织品的生产和降解[57], 因此可解释来自皮革和纺织品制造等行业.因子2主要由PFOS和PFPeA组成, 占来源贡献总量的27.10% PFOS和PFPeA的存在可归因于金属电镀行业的工业排放[45], 因此可解释金属电镀行业的影响.因子3主要由PFOA和PFDA组成, 占来源贡献总量的49.43%, PFDA的生产是有限的, 被认为是前体化合物的降解产物[66], PFOA是工业应用中最常用的PFASs, 主要来源于纺织品阻燃、橡胶品的乳化、食品包装过程和纸类表面处理等[67], 因此可解释来自纺织品阻燃、橡胶品的乳化、食品包装过程和纸类表面处理.因子4主要由PFHpA和PFNA组成占来源贡献总量的6.53%, PFHpA和PFNA是传统PFASs, 它们通常应用于含氟聚合物产品[20], 因此可以解释含氟聚合物的生产.

图 7 骆马湖表层水中PFASs的子载荷 Fig. 7 Loading factors of PFASs in surface water from Luoma Lake

2.4 健康风险评估

本研究用式(2)计算了10种PFASs在不同年龄不同性别中的HQ值(因为没有相关毒理学数据[37], 计算不包括PFTeA、PFTrA、PFBA和PFPeA).

健康风险评估如图 8所示, 结果表明在高暴露背景情况下本研究计算的PFASs的HQ值全部低于0.2的阈值(图 8中虚线), 其中, C8的PFOA和PFOS的HQ值最高.在所有的年龄和性别组中PFASs的HQmix均低于0.2的阈值, 说明骆马湖作为宿迁和新沂的饮用水源地健康风险值较低.其中3~6岁和20~24岁群体的HQmix较高, 说明这两个年龄组对PFASs的易感程度更高.其中3~6岁年龄组是因为个体体重较低, 20~24岁年龄组的HQmix值第二高是因为在相同日耗水量的条件下, 其体重低于其他年龄组.并且由于体重相对较低, 女性的HQmix值高于男性, 这说明PFASs的累积毒性对女性的风险大于男性.

(a)各类PFAS的健康风险值, (b)PFASs对于各个年龄段人类的累积健康风险值 图 8 PFASs在高暴露情景时的健康风险评估 Fig. 8 Health risk assessment of perlyfluoroalkyl substances (PFASs) in the high-exposure scenario

从各类PFASs的HQ值和HQmix来看, 健康风险不大, 但PFASs长期暴露的直接摄入和生物积累风险不可忽视[12].由于相关毒理学资料的缺乏, 本研究并没有评价此次采样中检出含量较高的PFPeA, 并且现有的研究普遍认为膳食是最主要的PFASs暴露来源[68], 本研究对骆马湖水产品中的PFASs含量未作评价, 在今后的研究中会重点关注.

3 结论

(1) 骆马湖表层水和沉积物中PFASs普遍被检出, 表层水中ρ(∑PFASs)范围为46.09~120.34ng·L-1(平均值为76.36ng·L-1), 沉积物中的ω(∑PFASs)范围为2.22~9.55ng·g-1, (平均值为5.61ng·g-1), 其中表层水中的主要组分是PFPeA(C5, 质量分数为37%)和PFOA(C8, 质量分数为33%), 沉积物中的主要组分是PFBA(C4, 质量分数为61%).短链PFASs在骆马湖表层水和沉积物中占主要含量可能是因为前驱体和短链PFASs目前已被作为长链PFASs的替代品而被广泛使用.

(2) 骆马湖表层水和沉积物中PFASs有不同空间分布特征, 北部入湖河流是骆马湖表层水中PFASs主要污染来源, 其浓度呈现由北向南递减的趋势, 沉积物中PFASs的高含量区域则向南迁移, 经过Spearman相关性分析得到骆马湖沉积物中的TOC和∑PFASs、PFBA极显著相关, 和PFOS显著相关.

(3) 通过PCA-MLR法进一步量化了骆马湖表层水中PFASs的潜在来源和贡献.主成分分析表明骆马湖表层水中PFASs主要有4种不同类型的污染源, 多元线性回归计算出的贡献值表明, 骆马湖表层水中PFASs主要来自纺织品阻燃、橡胶品的乳化、食品包装过程和纸类表面处理等行业, 金属电镀行业, 皮革和纺织品制造行业.

(4) 健康风险评估表明, 在高暴露背景情况下, 骆马湖表层水中10类PFASs单体和其累计值的HQ值均未达到健康风险评估的阈值, 表明骆马湖表层水中PFASs处于较低健康风险水平.同时3~6岁和20~24岁群体对PFASs的易感程度更高、PFASs的累积毒性对女性的风险大于男性.

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