川东北大气沉降中水溶态重金属季节变化:自然和人为因素的影响

Seasonal variations of water-soluble heavy metals in atmospheric deposition at NE Sichuan,Central China:Natural and anthropogenic effects

大气沉降地球化学研究对解释表生环境中元素地球化学行为具有重要意义.但以往对大气沉降地球化学的研究主要集中在城市或者受工业活动强烈影响的地区.本研究选择地处偏远、无明显工业活动影响的川东北地区,于2011年8月—2014年7月采集大气沉降样品,对其中水溶态重金属元素Cr、Co、Ni、Cu、Zn、Ga、As、Cd和Pb进行了研究.结果表明,这些重金属元素的年平均沉降通量最大的为Zn,158μg·(102cm^2·a)^-1,最小的为Ga,0.06μg·(102cm^2·a)^-1,相差达到4个数量级.相对于我国城镇地区或受工业活动影响的偏远地区,川东北地区重金属元素沉降通量较低.总体上Co和Ni的沉降通量在冬-春季节较高,可能与这些季节的大气粉尘活动有关,Ga、Pb、Cr、Cd、Zn、As等则一般在夏季沉降通量较高,可能与降水增加和旅游旺季的人类活动加强有关.2012年12月—2013年9月的当地道路改建工程导致了重金属元素沉降通量的明显提高.

Geochemical study of atmospheric deposition is important for explanation of the geochemical behavior of elements in epigenetic environment.However,previous studies largely focused on cities or areas strongly affected by industrial activities.In this study,the NE Sichuan Province,a remote area receiving little influence from industrial activities,was selected to investigate water-soluble heavy metals(such as Cr,Co,Ni,Cu,Zn,Ga,As,Cd and Pb)in the atmospheric depositions collected from in August 2011 to July 2014.The results indicated that Zn had the largest deposition flux with an annual average of 158μg·(10^2cm^2·m)^-1,while Ga had the smallest one with an annual average of 0.06μg·(10^2 cm^2·m)^-1,4 orders of magnitude lower than that of Zn.The deposition flux of heavy metals at NE Sichuan was lower than those obtained at cities and towns or in areas affected by industrial activities.In general,Co and Ni showed higher deposition fluxes in the winter and spring seasons which might be related to atmospheric dust activities in these seasons.Ga,Pb,Cr,Cd,Zn and As displayed higher deposition fluxes in the summer season,which might be due to increased precipitation as well as more tourist activities in this season.The local road reconstruction in December 2012—September 2013 led to a significant increase in the deposition flux of heavy metals.