若尔盖高原湿地地表水与大气湿沉降中有机氯农药和多氯联苯研究

采用高分辨率气相色谱-高分辨率质谱联用法分析位于青藏高原东缘的若尔盖高原牧场地表水和大气湿沉降中有机氯农药(OCPs)和多氯联苯(PCBs)异构体含量的季节分布特征,探讨持久性有机污染物(POPs)在边远清洁地区的地球化学行为.结果表明,若尔盖地区地表水中∑HCHs、∑DDTs、HCB、∑6PCBs平均浓度分别为0.90,1.36, 0.95,1.35ng/L.大气降水中OCPs和PCBs平均浓度分别为0.363,0.118ng/L,最大值出现在11月初冬的降雪样品中.异构体按平均浓度排序为HCB > PCB28 > p,p’-DDD > p,p’-DDE > α-HCH > γ-HCH.PCBs以PCB28和PCB52为主,除少量的PCB101外,其余高氯代PCB化合物都未在沉降样品中检出.∑HCHs、∑DDTs、∑PCBs的大气沉降通量分别为0.058~0.268,0.087~0.311,0.049~0.188ng/(m2·d).高海拔地区POPs大气沉降模式可分为“海拔梯度降水型”和“高原型”2类.类似于极地冷凝作用,高原型降雪中的POPs的沉积通量高于降雨沉降通量,但持久性较强的PCB138、PCB153和PCB180则缺失.这一结果验证了高空大气远程迁移和局地的高山冷凝效应的区别.

Research of organochlorine pesticides and polychlorinated biphenyls in atmospheric precipitation and surface water in Zoige alpine wetland

To further understand the geochemical behaviors of persistent organic pollutant (POPs) in remote areas, the seasonal distribution characteristics of anthropogenic organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) concentrations in surface water and wet precipitation samples collected from Zoige alpine wetland in the eastern edge of the Qinghai-Tibet Plateau were determined by HRGC-HRMS. The mean concentrations of ∑HCHs, ∑DDTs, HCB, ∑6PCBs in the surface water were 0.90, 1.36, 0.95, 1.35ng/L, respectively. The mean concentrations of ∑OCPs and ∑6PCBs in wet precipitation were 0.363, 0.118ng/L, respectively, with the maximum values present in snow of November. The mean concentrations were in the order of HCB > PCB28 > p,p’-DDD > p,p’-DDE > α-HCH > γ-HCH. PCB28and PCB52were the predominant PCB congeners. Except for trace amount of PCB101, all highly chlorinated PCB congeners were not detected. The deposition fluxes of ∑HCHs, ∑DDTs, and ∑6PCBs were in the range of 0.058~0.268, 0.087~0.311, and 0.049~0.188ng/(m2·d), respectively. The results confirmed the difference between long-range atmospheric transport via high altitude air mass and the mountain cold trapping effect. The precipitation mode of POPs in high altitude areas can be distinguished as two types, i.e., the “altitudinal gradient wet precipitation mode” and the “high plateau mode”. Similar to the cases in polar areas, the snow deposition flux of POPs in “high plateau mode” is generally higher than rain deposition flux, lack of less persistent PCB 138, PCB153and PCB180components.