三峡库区腹地秋末冬初大气干湿沉降化学组成特征

Characteristics of Chemical Composition in Wet and Dry Deposition in Late Autumn and Early Winter in the Hinterland of the Three Gorges Reservoir Region

为了解三峡库区腹地秋末冬初大气干湿沉降化学组成特点,采集了万州(城区)和高阳(郊区)两个监测点2015年10—12月的降水和降尘样品,测定了样品的pH、电导率和主要水溶性离子组分(K^+、Na^+、Ca^(2+)、Mg^(2+)、F^-、Cl^-、NO_3^-、SO_4^(2-))。结果表明:万州和高阳湿沉降pH的加权均值为5.79和5.73,平均电导率为45.67μS/cm和25.11μS/cm,湿沉降酸化程度较弱。湿沉降中SO_4^(2-)为主要阴离子,Ca^(2+)和NH_4^+为主要的阳离子,万州和高阳的平均浓度为229.01μeq/L和104.49μeq/L。万州和高阳的[SO_4^(2-)]/[NO_3^-]值分别为6.28和2.61,说明万州和高阳主要为硫酸型污染。由于各个月份降雨量不同,离子组分在时空上存在着不同,总体表现为12月>11月>10月,总体的污染程度是万州城区>高阳郊区。

In order to understand the chemical compositions of wet and dry deposition in the hinterland of the Three Gorges Reservoir Area（ TGRA）,precipitations and dustfall were collected in Wanzhou（ urban） and Gaoyang（ suburban） between October to December,and p H,conductivity and major water-soluble ions of sample components（ K~＋,Na~＋,Ca^（2＋）,Mg^（2＋）,F-,NO3^-,Cl^-,and SO4^（2-）） were determined. The results showed that the average pH values of wet deposition were 5. 79 and 5. 73 in Wanzhou and Gaoyang,and the average conductivities were 45. 67 μS·cm^（-1） and 25. 11μS·cm^（-1）,indicating the good air quality in the hinterland of TGRA. SO4^（2-） was the major anion in wet deposition with the average concentrations were 229. 01 μeq·L^（-1） and 104. 49μeq·L^（-1）,respectively,and the main cations were Ca^（2＋）and NH4~＋. The high [SO4^（2-）]/[NO3^-]values were 6. 28 and 2. 61 in Wanzhou and Gaoyang,which indicated that the rain acidity in this region was governed by SO4^（2-）.There existed great spatial-temporal variations in water-soluble ions because of the different rainfall in each month. Overall,the temporal variation trend was December November October,and the pollution level in urban area was greater than the suburban area.