长江水体多氯联苯和有机氯农药污染特征与通量研究

河流作为陆源持久性有机污染物(POPs)进入海洋的重要途径，其POPs污染问题备受关注. 为了解我国“十三五”时期长江水体多氯联苯(PCBs)和有机氯农药(OCPs)的污染特征，以2017年11月—2018年11月在长江大通站采集的表层水为研究对象，利用气相色谱-三重四级杆串联质谱仪(GC-MS/MS)测定水体中溶解态、颗粒态PCBs和OCPs的浓度，分析水体中溶解态、颗粒态PCBs和OCPs的污染特征，通过化合物组成特征和比值揭示水体中PCBs、OCPs的来源，估算输出通量，并从污染物浓度、年径流量及输沙量三方面加以比较. 结果表明:大通站水体中溶解态∑₄₁PCBs和∑₉OCPs浓度范围分别为0.059~0.29和0.21~0.52 ng/L，颗粒态∑₄₁PCBs和∑₉OCPs浓度范围分别为0.26~0.88和0.34~0.89 ng/L. 六六六(HCHs)、滴滴涕(DDTs)和氯丹(CHLs)均以历史使用残留为主，而PCBs存在新的输入. PCBs、HCHs和DDTs的总输出通量(溶解态+颗粒态)分别为0.57、0.35和0.29 t/a，远低于其他学者于2009—2015年得到的长江入海PCBs、HCHs和DDTs的年均通量. 研究显示，大通站水体中溶解态、颗粒态PCBs和OCPs的污染特征不同，大通站相对较低的PCBs、HCHs和DDTs的输出通量与长江流域过去10年污染物浓度、年径流量和输沙量的整体降低直接相关，溶解态PCBs、HCHs和DDTs浓度显著降低是重要因素. 研究结果反映了我国“十三五”期间提出的长江经济带“共抓大保护，不搞大开发”和近20年坚持履行《关于持久性有机污染物的斯德哥尔摩公约》的重要成效. 今后应重点关注大通以下至长江河口的污染物跨介质分配和交换通量，以系统揭示长江输出POPs在区域污染物“源汇”关系中扮演的角色. 

Pollution Characteristics and Fluxes of Polychlorinated Biphenyls and Organochlorine Pesticides in Water of the Yangtze River

River runoff is an important pathway for terrestrial organic matters to enter the ocean, and persistent organic pollutants (POPs) pollution is of particular concern. In order to understand the pollution characteristics of PCBs and organochlorine pesticides (OCPs), including hexachlorocyclohexane (HCHs), dichlorodiphenyltrichloroethane (DDTs) and chlordane (CHLs), in the Yangtze River, water samples were collected at the Datong Station of the Yangtze River during November 2017 to November 2018. The concentrations of dissolved and particulate PCBs, HCHs, DDTs and CHLs were determined by gas chromatography-triple quadrupole tandem mass spectrometer (GC-MS/MS) to discuss compound composition, phase distribution and source. The fluxes were estimated and illustrated by the changes of concentration, annual runoff and sediment load. The results showed that the dissolved concentrations of ∑₄₁PCBs and ∑₉OCPs in surface water of the Datong Station were 0.059-0.29 and 0.21-0.52 ng/L, respectively. Moreover, the particulate concentrations of ∑₄₁PCBs and ∑₉OCPs were 0.26-0.88 and 0.34-0.89 ng/L, respectively. Combined with the comparison of concentration levels in different regions, the compound composition and ratio results indicated that HCHs, DDTs and CHLs were dominated by the historical application of pesticides, but there were new inputs of PCBs. The estimated fluxes of PCBs, HCHs and DDTs from river runoff were 0.57, 0.35 and 0.29 t/a, respectively. The results of this study indicated that the pollution characteristics of dissolved and particulate PCBs and OCPs in water of the Datong Station were different, and the fluxes of PCBs, HCHs and DDTs were significantly lower than those from 2009 to 2015 reported by previous studies, due to the overall reduction in pollutant concentration, annual runoff and sediment load of the Yangtze River over the past decade, and reduced dissolved concentration of PCBs, HCHs and DDTs in water were important factors. It can be said that ‘to set up conservation of the Yangtze River and stop its over development’ proposed during the ‘13th Five-Year Plan’ period, as well as the implementation of the Stockholm Convention on Persistent Organic Pollutants in the past 20 years have jointly contributed to the decline of flux. In the future, further studies should focus on the profile distribution of POPs and exchange fluxes at the different media interface from Datong to the Yangtze River Estuary, to systematically reveal the role of the Yangtze River runoff output and its implications for the regional POPs cycle.