珠海市降水化学与沉降特征

为探究珠海市降水及湿沉降的长期变化趋势，基于东亚酸沉降监测网（EANET）的湿沉降监测数据，针对2008—2018年珠海市大气降水量、降水电导率、pH、水溶性离子浓度与湿沉降量进行了降水酸化、降水组分及湿沉降分析.结果表明:①珠海市1—12月降水pH均低于5.6，强酸雨及特强酸雨频率较高，降水酸化问题普遍；2008—2018年pH由4.9增至5.2，总体呈改善趋势；降水电导率小于3 mS/m的月份占61.68%.②珠海市降水中Cl-浓度和Na+浓度较高，二者的区域性特征表明海洋源和人为源共同影响珠海市降水；SO₄2-/NO₃-（浓度比）总体呈逐年递减趋势，降水类型为硫酸-硝酸混合型；较低的ΔpH（酸中和能力评估参数）说明缺乏中和能力可能是珠海降水酸化问题严重的主要原因.③珠海市湿沉降量范围为71.98~200.77 kg/（hm2·a），其中SO₄2-湿沉降量最高；2008—2018年DIN-N（可溶性无机氮湿沉降量）在11 kg/（hm2·a）上下波动，而SO₄2--S（硫湿沉降量）降幅接近40%；大气氮、硫湿沉降量在春季达到最高.四季NH₄+-N/NO₃--N（铵态氮湿沉降量与硝态氮湿沉降量的比值）均大于1，说明珠海市活性氮主要来源于农业活动.研究显示，珠海市大气降水酸化问题普遍但总体呈改善趋势，严重的降水酸化问题与缺乏中和能力存在一定关系. 

Characteristics of Precipitation Chemistry and Wet Deposition in Zhuhai,China

In order to understand the long-term change trend of precipitation chemistry and wet deposition in Zhuhai, the chemical characteristics of precipitation and wet deposition from 2008 to 2018 were studied based on the monthly precipitation conductivity, pH, ion concentration and wet deposition data from Acid Deposition Monitoring Network in East Asia (EANET). The results showed: (1) The pH of precipitation between January and December in Zhuhai was lower than 5.6. The frequencies of strong and extremely strong acid rain were high. The problem of precipitation acidification was widespread. The pH value increased from 4.9 to 5.2 between 2008 and 2018 with an improving trend. The months with precipitation conductivity less than 3 mS/m accounted for 61.68%. (2) The concentration of Cl- and Na+ in the precipitation of Zhuhai was high, which indicated that the combined effects of marine and anthropogenic sources on the precipitation. The downward trend of SO₄2-/NO₃- occurred year by year, and the mixed type of sulfuric and nitric acid was the main type of the precipitation. The low ΔpH (evaluation parameter of acid neutralization capacity) indicated that the lack of neutralization capacity might be the main reason for the serious acidification of precipitation in Zhuhai. (3) The range of wet deposition in Zhuhai was 71.98-200.77 kg/(hm2·a), in which SO₄2- deposition was the highest. The deposition of DIN-N (the depostition of dissolved inorganic nitrogen) fluctuated around 11 kg/(hm2·a) from 2008 to 2018, while SO₄2--S (sulfur deposition) decreased by nearly 40%. The maximum wet deposition of atmospheric nitrogen and sulfur occurred in spring. The ratios of NH₄+-N/NO₃-N (the ratio of ammonium nitrogen to nitrate nitrogen deposition) was greater than 1 in the four seasons, indicating that the active nitrogen mainly came from agricultural activities. The precipitation acidification was widespread in Zhuhai, but the overall trend is improving. There was a certain relationship between the serious precipitation acidification and the lack of neutralization capacity.