环境科学  2024, Vol. 45 Issue (7): 3919-3929   PDF    
洞庭湖水和沉积物中有机磷酸酯的分布特征及风险评估
高蕴语, 董靖, 代然, 刘亚清, 赵兴茹, 郑丙辉     
中国环境科学研究院环境基准与风险评估国家重点实验室, 湖泊水污染治理与生态修复技术国家工程实验室, 国家环境保护湖泊污染控制重点实验室, 北京 100012
摘要: 有机磷酸酯(OPEs)作为阻燃剂和添加剂, 广泛应用于生产生活, 在环境中普遍检出. 为探究其环境行为, 采用超高效液相色谱-串联质谱联用仪(UPLC-MS/MS)测定洞庭湖的表层水和沉积物样品中13种OPEs, 共检出11种, 检出率分别为5.26%~100%和58.3%~100%, ∑OPEs含量范围分别为2.06 ~ 2 028 ng·L-1和19.6~ 2 232 ng·g-1. 从整体上看, 表层水中∑OPEs浓度呈现入湖河流 > 湖区 > 出口的趋势, 而沉积物中浓度的空间分布与水动力呈相反趋势. 和国内外湖泊相比, 洞庭湖OPEs污染浓度处于较高水平. 在检出的11种OPEs中, 磷酸三正丁酯(TnBP)和磷酸三异丁酯(TiBP)是水中主要的污染物, 占∑OPEs的52.3%和22.4%;沉积物中主要为磷酸三苯酯(TPhP), 占总量的31.2%. 相关性和主成分分析结果表明, 洞庭湖OPEs污染主要受工业生产排放、渔业养殖业和大气沉降的影响. 风险熵评估结果显示, 水体中检出的多数OPEs的生态风险相对较低, 但在部分采样点由2-乙基己基二苯基磷酸酯(EHDPP)引起的生态风险需引起关注.
关键词: 有机磷酸酯(OPEs)      洞庭湖      分布特征      风险评估      超高效液相色谱-串联质谱联用仪(UPLC-MS/MS)     
Distribution Characteristics and Risk Assessment of Organophosphates in Water and Sediment in Dongting Lake
GAO Yun-yu , DONG Jing , DAI Ran , LIU Ya-qing , ZHAO Xing-ru , ZHENG Bing-hui     
State Key Laboratory of Environmental Standards and Risk Assessment, National Engineering Laboratory for Lake Pollution Control and Ecological Restoration, State Environmental Protection Key Laboratory for Lake Pollution Control, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Abstract: Organophosphates (OPEs) are widely used as flame retardants and additives and thus are commonly detected in the environment. In order to explore their environmental behavior, the concentrations of 13 OPEs in the surface water and sediment of Dongting Lake were analyzed using UPLC-MS/MS. The results showed that 11 OPEs were detected, with detection frequencies of 5.26%-100% and 58.3%-100%, and the concentrations of OPEs were 2.06-2 028 ng·L-1 and 19.6-2 232 ng·g-1 in water and sediment, respectively. Overall, contamination concentrations were ranked in descending order as follows: inflowing rivers, lake area, and outlet, whereas the spatial distribution of concentrations in sediment was inversely proportional to hydrodynamics. The concentration of OPEs in Dongting Lake was at a high level compared with that of domestic and foreign lakes. Among the detected 11 OPEs, tri-iso-butyl phosphate (TnBP) and (TiBP) were dominant in water, accounting for 52.3% and 22.4% of ∑OPEs, respectively. TPhP was the dominant OPEs in sediment, accounting for 31.2% of ∑OPEs. The correlation and principal component analysis indicated that OPEs pollution in Dongting Lake was mainly affected by industrial production emissions, fishery aquaculture, and atmospheric deposition. The assessment results of the risk entropy showed that most of the detected OPEs in water had relatively low ecological risks, whereas the ecological risk of 2-ethylhexyl diphenyl phosphate (EHDPP) at some sampling points requires further attention.
Key words: organophosphates (OPEs)      Dongting Lake      distribution characteristics      risk assessment      ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)     

有机磷酸酯(organophosphate esters, OPEs)是一类人工合成的磷酸衍生物, 因其优良的阻燃性和柔韧性被广泛用作电子设备、纺织品、塑料材料和乳胶漆等产品中的阻燃剂、增塑剂和消泡剂, 或作为液压油和润滑油中的添加剂[1 ~ 4]. 有机磷酸酯作为卤代阻燃剂的替代品, 生产量和使用量逐年增加, 2013~2018年, 全球OPEs的产量从62万t·a-1增加至105 t·a-1;在中国, 2007年时OPEs产量为7万t, 至2020年已增加至36.3万t[3, 5]. 由于OPEs主要以物理添加而非化学键合的方式存在于产品中, 因此在产品的使用周期中(包括生产、使用、处置和回收)易以挥发、扩散或磨损等方式从产品中释放出来[3, 6]. 据报道, OPEs在各种环境介质和生物体中均有检出[6 ~ 15]. OPEs日益增长的使用量, 及其在环境介质和生物体中的广泛检出, 也逐渐引起人们对其潜在生物毒性效应的关注. 研究表明, 磷酸三甲酯(trimethyl phosphate, TMP)、磷酸三(2-氯乙基)酯[tri(2-chloroethyl)phosphate, TCEP]、磷酸三正丁酯(tri-iso-butyl phosphate, TnBP)、磷酸三苯酯(triphenyl phosphate, TPhP)和磷酸三(1-氯-2-丙基)酯[tris(1-chloro-2-propyl)phosphate, TCPP]等, 具有潜在的生殖毒性、胚胎发育毒性、神经毒性、潜在的致癌性和内分泌干扰效应[16 ~ 22]. 此外, 卤代OPEs(如TCEP和TCIPP)在水环境中具有相当强的持久性, 部分OPEs还具有较强的亲脂性和半挥发性, 因此在具有较强的迁移能力和蓄积的潜力[1, 16, 17]. 近年来, 有机磷系阻燃剂污染成为新兴污染物研究的热点问题之一.

洞庭湖位于湖南省北部, 是我国第二大淡水湖, 是长江流域重要的调蓄湖泊和饮用水源地, 保障洞庭湖水质和维护生态系统健康具有重要意义. 关于洞庭湖水中OPEs的研究鲜见报道[23], 沉积物中OPEs的研究未见报道. 本文采集洞庭湖入湖河流和湖区的表层水和沉积物样品, 采用超高效液相色谱-串联质谱联用仪(UPLC-MS/MS)对13种OPEs进行检测, 分析其中OPEs的浓度水平与分布特征, 并探究其潜在来源, 以期为洞庭湖有机污染防治与生态安全保障工作提供数据支撑.

1 材料与方法 1.1 研究区域概况

洞庭湖(27°39′~29°51′N, 111°19′~113°34′E)位于长江中游荆江南岸、湖南省北部, 跨岳阳、常德和益阳等县市, 北纳长江的松滋、太平、藕池和调弦四口来水, 南、西接湘江、资水、沅江、澧水和汨罗江等小支流, 由岳阳市城陵矶注入长江. 洞庭湖平水期湖泊面积2 625 km2, 总容积1.74×1010 m3. 洞庭湖周边城市降水季节差异很大, 雨季降水量为115.7~159.3 mm, 远高于旱季降水(52.9~67 mm). 此外, 洞庭湖是我国农工业重点发展区域, 渔业、养殖业和机械装备制造业生产地位重要[23 ~ 25].

1.2 样品采集

在洞庭湖湖区和4条入湖河流及出口布设共20个采样点, 于2016年9月在各采样点采集水和沉积物样品, 采样点布设如图 1所示. 其中, 东洞庭湖采样点:BS、BXQ、LJ、DDTH、DXXH、LMZ和YYL;西洞庭湖采样点:NZ、JJZ和XHZ;南洞庭湖采样点:WZH、HLH、YGM和ND;出湖口采样点:CLJ和DTHCK;入湖四水采样点:ZSG、WJZ、PT和SHK;其中, YYL的水样缺失, BS、BXQ、DXXH、XHZ、CLJ和SHK这6个采样点因水深等问题, 未采集到底泥.

图 1 洞庭湖采样点分布示意 Fig. 1 Dongting Lake area and sampling sites

用采水器采集1L表层水样于棕色玻璃瓶, 加入2 mL甲醇以减少瓶壁对化合物的吸附. 运回实验室后, 经0.45 μm滤膜过滤去除悬浮颗粒物后, 4℃冷藏保存待处理分析. 沉积物样品用抓泥斗采集, 铝箔纸包裹, 置于冷藏箱运回实验室, 冷冻干燥后挑除石粒和植物, 研磨并过80目筛, -20℃保存至分析.

1.3 实验试剂与仪器

主要仪器:超高效液相色谱-串联质谱联用仪(Xevo T-QS型, Waters, USA), 全自动固相萃取仪(SPE-DEX 4790, Horizon Technology), 加速溶剂萃取仪(ASE350, Dionex), DryVap浓缩仪(Horizon Technology, USA), 氮气蒸发仪(Organomation Associate Inc)和马弗炉(TM-0610P, 北京盈安美诚科学仪器有限公司).

主要试剂:OPEs标准品包括OPE mix1#~16#(天津阿尔塔科技有限公司)、内标TnBP-d27、TCEP-d12和TPhP-d15(CDN Isotopes Inc., CAN), 农残级正己烷(n-hexane)、二氯甲烷(dichloromethan)和甲醇(methano)购自Fisher(Fair Lawn, NJ, USA)和Tedia(Fairfield, OH, USA), 活性硅胶(试剂级, 青岛海洋化工), 无水硫酸钠、氢氧化钠和浓硫酸(优级纯, 北京化工厂), 碱性氧化铝(色谱纯, 国药集团化学试剂有限公司). 所测定化合物的详细信息见表 1.

表 1 OPEs的理化性质1) Table 1 Physical and chemical properties of OPEs

1.4 样品前处理 1.4.1 水样前处理

采用HLB固相萃取小柱进行水样的富集. 取1 L表层水样品, 过0.45 μm的玻璃纤维膜后, 加入5 ng TCEP-d12、TPhP-d15和TnBP-d27, 混匀后平衡2 h, 然后通过HLB小柱固相萃取. 富集前, 依次用二氯甲烷、甲醇和纯水各10 mL活化HLB小柱. 将平衡好的水样上样至小柱, 按5~10 mL·min-1的流速, 上样后, 真空干燥萃取柱30 min, 再用10 mL二氯甲烷洗脱. 收集洗脱液, 浓缩完全后转移至内衬管, 氮吹至近干, 用0.1%甲酸水∶乙腈(95∶5, 体积比)至100 μL待测[26].

1.4.2 沉积物前处理

称取2 g沉积物样品样品于萃取池, 加入5 ng的3种氘代标液, 混匀平衡后用二氯甲烷∶正己烷(1∶1, 体积比)进行加速溶剂萃取. 提取液浓缩, 并氮吹至2~3 mL, 经复合硅胶柱、碱性氧化铝柱和弗洛里硅土柱净化分离. 收集洗脱液, 后续操作同水样.

1.5 仪器分析

样品的分析采用超高效液相色谱-串联质谱联用仪(UPLC-MS/MS), 色谱柱选用Waters BEH C18(2.1 mm×50 mm, 1.7 µm). 进样体积为10 µL, 流速0.45 mL·min-1, 柱温40℃. 流动相为0.1%的甲酸水(A)和乙腈(B), 流动相梯度设置:0~0.5 min 95% 流动相A, 5 min 5% 流动相A, 6 min 5%流动相A, 6.1 min 95% 流动相A, 7.5~8 min 5% 流动相A. 使用正离子模式和多反应监测记录色谱图, 目标化合物参数详见表 2[27].

表 2 目标OPEs的UPLC-MS/MS参数 Table 2 UPLC-MS/MS parameters of target OPEs

1.6 质量控制

采用内标法定量. 配制10.0~2 000 μg·L-1的混标溶液做标准曲线, 相关系数(r2)均在0.990以上. 分析样品前, 取4份相同的样品, 每个样品中均加入16种OPEs混标, 仅其中一份加入同位素内标, 进行精密度和回收率实验, 每12个样品做一个全过程空白. 表层水样的检出限为0.12~0.78 ng·L-1, 回收率为90.3%~110.7%, 精密度为8.78%~ 13.4%. 沉积物的检出限为0.57~1.44 ng·g-1, 回收率77.1%~103.5%, 精密度9.86%~ 17.1%.

1.7 数据分析

采用Origin 22和SPSS 23软件进行Pearson相关性和主成分分析.

1.8 相关公式 1.8.1 逸度分数(ff)

逸度分数(ff)用于评估沉积物和水体之间化学物质的平衡状态和交换行为, 其计算公式如下:

(1)

式中, ρw为水中目标化合物的浓度, ng·L-1ωs为沉积物中目标化合物含量, ng·g-1foc为沉积物中的有机碳含量, %;Kow为化合物的辛醇-水分配系数(无量纲). 当ff > 0.5时, 它表示有机污染物从沉积物迁移到水中;当ff < 0.5时, 表示有机污染物从水中迁移到沉积物中[28].

1.8.2 风险评估

采用风险熵(risk entropy, RQ)评估OPEs的生态风险, 计算公式如下:

(2)
(3)

式中, MEC为污染物的实测浓度, PNEC为无效应浓度, LC50为半数致死浓度, EC50为半数效应浓度, 上述浓度单位均为mg·L-1;AF为评估因子, 取值1 000. 当RQ < 0.1时, 生态环境风险很低可以忽略;当0.1≤RQ < 1.0时, 说明有中等生态环境风险;当RQ≥1.0时, 有高生态环境风险[23].

2 结果与讨论 2.1 洞庭湖表层水和沉积物中OPEs的浓度水平

OPEs在洞庭湖水和沉积物中广泛存在, 各采样点均有不同浓度检出, 但表层水和沉积物之间的检出率有所不同. 13种OPEs中, 8种对所有表层水和沉积物样品的检出率超过50%, TMP、TBP、TPhP和TCPP的检出率超过70%;EHDPP(75%)、TBEP(75%)和TEHP(83.3%)对沉积物样品的检出率较高, 但对于水样检出率偏低(47.4%、42.1%和63.2%).

洞庭湖表层水和沉积物中∑13 OPEs的浓度和各种OPEs的浓度差异很大(见表 3图 2), 所有采样点的水样中∑13 OPEs浓度范围为2.06~2 028 ng·L-1(均值491 ng·L-1, 中值176 ng·L-1). 洞庭湖入湖河流的表层水中∑13 OPEs浓度最高, 均值为841 ng·L-1, 湖区∑13 OPEs浓度低于入湖河流, 均值为431 ng·L-1, 出口处∑13 OPEs浓度降至最低, 均值为10.1 ng·L-1. 从总体上看, 洞庭湖表层水中∑OPEs的浓度呈现入湖支流 > 湖区 > 湖区出口的趋势, 说明入湖河流输入是洞庭湖OPEs的主要来源. TnBP和TiBP是洞庭湖表层水中污染最严重的物种, 浓度分别为未检出(ND)~ 1 138 ng·L-1和ND ~ 551 ng·L-1, 均值为250 ng·L-1和107 ng·L-1, 与松花江(87~960 ng·L-1[29]相当, 高于珠江三角洲[30](10.5~389 ng·L-1)和北京市河流[31](ND~256 ng·L-1), 远高于韩国Shihwa湖(15.6~72.9 ng·L-1[32]和骆马湖(0.01~5.85 ng·L-1[33], 两物种的高浓度水平表明洞庭湖流域中有新的可能来源, 有待进一步考察. ρ(TCPP)为ND~307 ng·L-1, 均值73.2 ng·L-1, 与太湖(30.53~287.28 ng·L-1[34]和杭州湾(21.9~106 ng·L-1[35]相当, 低于北京市河流(ND~1 742 ng·L-1[31]和韩国Shihwa湖(68.3~5 102 ng·L-1[32], 高于骆马湖(0.02~10.8 ng·L-1[33]和北冰洋水(ND~5.4 ng·L-1[36]. ρ(TPhP)为ND~78.1 ng·L-1, 均值27.1 ng·L-1, 高于太湖(ND~14.49 ng·L-1[34]、杭州湾(ND~21.7 ng·L-1[35]、骆马湖(0.15~8.16 ng·L-1[33]和珠江三角洲(0.90~5.15 ng·L-1[30], 与Xu等[23]于2021年在洞庭湖的调查结果相当(ND~27.8 ng·L-1), 略高于北冰洋水(ND~63 ng·L-1[36]、北京市河流(< LOD~96.3 ng·L-1[31]和韩国Shihwa湖(5.14~96.2 ng·L-1[32]. ρ(TEHP)(ND~34.5 ng·L-1, 均值9.08 ng·L-1)低于韩国Shihwa湖(ND~59.4 ng·L-1[32], 略高于太湖(ND~14.56 ng·L-1[34], 与北京市河流(ND~23.5 ng·L-1[31]和杭州湾(0.81~3.50 ng·L-1[35]相当, ρ(TBEP)(ND~34.6 ng·L-1, 均值6.50 ng·L-1)与韩国Shihwa湖(ND~59.4 ng·L-1[32]相当, 远低于北京市河流(ND~3 617 ng·L-1[31].

表 3 洞庭湖表层水和沉积物中OPEs的含量1) Table 3 Concentration of OPEs in surface water and sediments of Dongting Lake

图 2 洞庭湖表层水和沉积物中OPEs的浓度空间分布 Fig. 2 Spatial distribution of OPEs concentrations in surface water and sediments of Dongting Lake

沉积物通常被视为有机污染物的汇或潜在的源[31]. 13种OPEs因采样点不同而有显著差异, 沉积物中ω(∑OPEs)范围为19.6~2 232 ng·g-1, 均值为438 ng·g-1. 与表层水中不同, TPhP是沉积物中的主要污染物, 其含量范围为ND~1 143 ng·g-1, 均值136 ng·g-1, 高于韩国Shihwa湖(1.28~257 ng·g-1[32], 远高于珠江三角洲(0.90~7.80 ng·g-1[30]、杭州湾(0.07~0.16 ng·g-1[35]、骆马湖(0.01~0.03 ng·g-1[33]、太湖(ND~54.72 ng·g-1[34]、北冰洋(ND~45 ng·g-1[36]和北美五大湖(ND~9.03 ng·g-1[37]. ω(TnBP)和ω(TiBP)次之, 为4.54~330 ng·g-1和1.4~144 ng·g-1, 均值125 ng·g-1和53.2 ng·g-1, 高于珠江三角洲(1.30~32.0 ng·g-1[30]和韩国Shihwa湖(0.18~33.3 ng·g-1[32], 远高于杭州湾(4.71~7.89 ng·g-1[35]、骆马湖(0.02~0.05 ng·g-1[33]、北美五大湖(ND~7.62 ng·g-1[37]和北冰洋(0.36~2.1 ng·g-1[36]. ω(TCPP)(0.22~484 ng·g-1, 均值52.1 ng·g-1), 高于韩国沿海沉积物(ND~216 ng·g-1[38]ω(TEHP)(ND~93.8 ng·g-1, 均值28.7 ng·g-1)与韩国沿海沉积物(ND~92.0 ng·g-1[38]相当, 低于长三角电子回收区(1.90~568 ng·g-1[39]ω(EHDPP)ND~205 ng·g-1, 均值31.4 ng·g-1)高于韩国Shihwa湖(0.67~47.6 ng·g-1[32]和太湖(ND~0.86 ng·g-1[34].

2.2 洞庭湖表层水和沉积物中OPEs的组成

洞庭湖水和沉积物中13种OPEs的组成如图 3所示. TnBP(52.3%)、TiBP(22.4%)和TCPP(14.9%)是表层水中的主要OPEs, 而TPhP(31.2%)、TnBP(28.7%)、TiBP(12.2%)和TCPP(11.9%)在沉积物样品中占主导地位. 样品中OPEs的组成受OPEs的物理化学性质影响. 目标OPEs的lg Kow值范围为-0.65(TMP)~9.49(TEHP)[1]. 尽管表层水中TCEP(1.44)的比例可以忽略不计(0.242%), 但由于其lg Kow值较低, 在表层水中的贡献高于沉积物(0.06%);而对于TEHP(9.49)、EHDPP(6.64)和TCrP(5.11)这3种OPEs, 尽管它们在表层水的占比很低(0.01%~2%), 但由于lg Kow值高(5.11~9.49), 它们在沉积物样品中的占比共达14%. 根据lg Kow, TnBP(4)、TiBP(3.6)和TCPP(2.59)这3种OPEs在沉积物中的占比应多于水相, 但实际情况与之相反. 用总逸度分数ffsw来表示OPEs在表层水和沉积物两相间的平衡状态[28]. 经计算[24], 3种OPEs的ffsw均大于0.5, 即由沉积物向水相释放, 因此其在水相中的分配多于沉积物相.

(a)表层水(b)沉积物 图 3 洞庭湖表层水和沉积物中OPEs的百分组成 Fig. 3 Percentage composition of OPEs in water and sediments of Dongting Lake

水样中OPEs的组成与以前的报告不同, 以TCPP、TnBP和TiBP为主要化合物, 而在以往的研究中, 多为TCEP和TCPP占主导地位[30 ~ 32, 36]. 沉积物中OPEs的主要化合物除TCPP、TnBP和TiBP外, 还有TPhP. 值得注意的是, TnBP和TiBP在之前的研究中并不占主导地位[31 ~ 35], 但在此研究中, 水和沉积物中TnBP和TiBP分别占总量的73.0%和40.7%, 表明了洞庭湖流域特有的TnBP和TiBP来源.

2.3 洞庭湖表层水和沉积物中OPEs的来源分析

从空间分布上看, 入湖支流的水中∑OPEs浓度[(841 ± 947)ng·L-1, 均值±标准差, 下同]高于洞庭湖湖区[(431 ± 569)ng·L-1)和湖区出口[(10.1 ± 7.52)ng·L-1], 这表明OPEs通过入湖支流输入进入洞庭湖湖区, 这与Xu等[23]的研究结果一致. 此外, 湖区采样点S1(扁山)位于造纸厂污水排放口附近, 其ρ(∑OPEs)为1 727 ng·L-1, 仅次于资水入流处(WJZ), 这意味着工业生产与湖泊环境中OPEs的污染有关. 沉积物中的∑OPEs也在显著差异, 与水中不同的是, 洞庭湖湖区沉积物中ω(∑OPEs)为(580 ± 780)ng·g-1, 高于入湖支流[(155 ± 54.1)ng·g-1]和湖区出口(151 ng·g-1). 污染物在湖区沉积物中的分布与各点位的水动力有关[35]. 湖区采样点中, 水动力较低的两个采样点为WZH和LMZ[40], 此两点沉积物样品中∑OPEs的浓度高于其他点位, 这与河流的输送作用有关, 说明此处的OPEs主要来源于历史沉积.

对11种OPEs进行Pearson相关性分析. 结果如图 4所示, 水中的OPEs存在显著的相关性(P < 0.05), 其中TnBP、TiBP、TCPP、TBEP、TEHP、EHDPP和CDPP两两相关, 系数范围在0.714~0.999之间, 说明它们可能有相同的污染来源;TCEP、TCrP和TMP与其他OPEs无显著相关, 表明这3种OPEs有不同的污染源.

*表示P≤0.05, **表示P≤0.01 图 4 Pearson相关性热图 Fig. 4 Pearson correlation heat map

使用主成分分析(PCA)进一步确定洞庭湖水域中OPEs的来源及贡献. 经计算, 表层水中OPEs的浓度显著性为P < 0.05, KMO > 0.5, 符合主成分分析的要求. PCA提取了两个主成分(PC1和PC2), 总贡献率为65.56%, 因子载荷和点位得分如图 5所示. PC1解释了52.69%的方差, 对TnBP、TiBP、TPhP、TCPP、TBEP、TCEP、TEHP和EHDPP有较高的载荷, 与Pearson相关性分析的结果基本一致. WJZ、SHK、BS和WZH这4个采样点在PC1上有较高的得分, 表明其受PC1的影响较大. WJZ和SHK分别位于资水和澧水, BS采样点位于某造纸厂废水排放口附近, WZH则是重要的渔业养殖场. 上述采样点在PC1上有较高的得分, 表明其受PC1影响较大. TnBP、TiBP和EHDPP常被用作液压油、油漆和塑料的添加剂, 资水和澧水流经益阳市和常德市, 区域内机械和装备制造业发达, 表明了工业生产活动中OPEs的本地排放和入湖支流输入的影响. TCPP广泛应用于工业生产, 且使用量较大[41], TPhP则被用作纤维素和合成树脂等生产过程中的浸润剂[3], 这两种化合物在BS采样点的浓度水平高于其他点位, 说明了工业生产点源排放的影响. TCEP和TEHP被添加于聚乙烯和聚丙烯酸酯等材料中, 用于改善其耐水性和耐酸性[3], 可用来制作渔业用具, 洞庭湖渔业养殖业发达, 说明了渔业用具也是洞庭湖OPEs的来源之一. 综上所述, PC1主要为工业生产排放和渔业. PC2主要包括CDPP, 对方差的贡献率为12.81%. CDPP主要作为汽油和润滑油的添加剂, 广泛应用于车辆和机械装备, 在使用过程中易进入大气, 在雨水和灰尘中有较高检出[41, 42]. 有研究表明, 大气沉降是水生环境中OPEs的重要来源[23]. 洞庭湖雨季降水量为115.7~159.3 mm, 因此CDPP可通过降水等方式进入水体, 即PC2解释为大气沉降过程.

图 5 主成分因子载荷与得分 Fig. 5 Principal component factor load and score

2.4 生态风险评估

通过计算风险熵值对洞庭湖表层水中的OPEs进行风险评估, LC50数据来源于文献和世界卫生组织IRIS数据库[43 ~ 45]. 其中, TPrP和TDCP两种OPEs未检出, 无法计算. 剩余11种OPEs对藻、甲壳和鱼类这3种敏感物种的风险熵, 结果见表 4. 表明大部分OPEs对藻类、甲壳类和鱼类的RQs值小于0.1, 生态风险较低. 其中, EHDPP对甲壳类的风险最大, RQ的最大值为0.244 124, 在部分采样点(BS、SHK、WZH和BXQ)呈现中等风险(见图 6). 总体来看, 除EHDPP外, 其余OPEs对洞庭湖水生生物的风险可以忽略.

表 4 OPEs毒理数据及生态风险1) Table 4 OPEs toxicological data and ecological risk

图 6 洞庭湖各采样点OPEs的风险熵值 Fig. 6 Values of risk quotient for OPEs at sampling sites in Dongting Lake

3 结论

(1)洞庭湖流域的表层水和沉积物中广泛检测到OPEs, 其中∑OPEs的含量分别在2.06 ~ 2 028 ng·L-1和19.6 ~ 2 232 ng·g-1之间, 表层水中平均浓度呈现入湖支流 > 湖区 > 湖区出口的趋势, 沉积物中∑OPEs的含量则与各采样点的水动力分布呈相反趋势. 与国内外河流和湖泊相比, 洞庭湖OPEs污染处于中等水平.

(2)TnBP和TiBP是表层水中最丰富的OPEs, 浓度均值为250 ng·L-1和107 ng·L-1, 占∑OPEs的52.3%和22.4%;沉积物中TPhP浓度最高, 为136 ng·g-1, 占总量的31.2%. 主成分分析表明, 洞庭湖流域OPEs污染主要受入湖支流输入和工厂废水排放的影响. 此外, 由于洞庭湖渔业发达, 相关塑料制品带来的污染值得关注.

(3)生态风险评估结果显示, 大部分OPEs的生态风险可以忽略. EHDPP对洞庭湖中甲壳类生物风险最大, RQ值大于0.1, 在BS、SHK、WZH和BXQ这4个采样点呈现中等风险.

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