2000~2021年中国典型地区大气降水化学与沉降特征

Characteristics of atmospheric precipitation chemistry and deposition in typical regions of China during 2000~2021

基于2000~2021年中国东北、华北、华东、东南、西北、西南6个区域10个城市的大气降水组分资料,针对各地区降水量、pH值、降水电导率、水溶性离子浓度及其氮硫湿沉降特征开展了长期变化特征研究,分析了典型地区降水组分的离子中和特性.结果表明:2000~2021年中国各研究站点pH值总体呈上升趋势,但重庆和上海地区的年均pH值至今未达到5.6.济南、西安和重庆站电导率呈现出较明显的下降趋势.西北地区陆源性特征较为明显,Ca^(2+)浓度较高(可达1035.2μeq/L);NO_(3)^(-)浓度在重庆地区有上升趋势,这与城市机动车保有量的逐年增长有关;而NH_(4)^(+)在各个地区均有下降;东南地区受海盐影响,Na^(+)和Cl^(-)的浓度相对较高.西北和西南地区的硫、氮湿沉降量明显高于东南地区,NH_(4)^(+)-N/NO_(3)^(-)-N各地区均呈下降趋势,但该比值年平均值均大于1,说明大气降水中氮沉降以还原态氮为主.东南地区的降水酸度相对较高,然而酸性离子(SO_(4)^(2-)和NO_(3)^(-))浓度却较低,说明降水酸度还会受到碱性离子(Ca^(2+)和NH_(4)^(+))的影响.在厦门和西安NO_(3)^(-)、NSS-SO_(4)^(2-)和NH_(4)^(+)浓度年变化很小,而pH值、中和潜力和酸化潜力的比值(NP/AP)有明显上升趋势;但西安NP/AP值明显较高,反映西安土壤尘埃中的中和能力比东南地区强.

Based on the data of atmospheric precipitation in 10cities of the Northeast,North,East,Southeast,Northwest,and Southwest China from 2000 to 2021,a long-term variation trend was studied on precipitation amount,pH value,electrical conductivity,water-soluble ion concentration,and nitrogen and sulfur wet deposition in various regions.The ion neutralization of precipitation components in typical sites was also analyzed.The pH values of each site in China generally showed an upward trend from 2000 to 2021,but the annual average pH in Chongqing and Shanghai had not yet reached 5.6.The electrical conductivity showed a significant downward trend in Jinan,Xi'an,and Chongqing.The terrestrial characteristics were more obvious in the Northwest with a higher concentration of Ca^(2+)(up to 1035.2μeq/L).The concentration of NO_(3)^(-)showed an upward trend in Chongqing,which was related to the growth of motor vehicle ownership.The concentration of NH_(4)^(+)decreased in all regions.The relatively high concentrations of Na^(+)and Cl^(-)occurred in Southeast,where was influenced by sea salt.The sulfur and nitrogen wet deposition in the Northwest and the Southwest was significantly higher than that in the Southeast.The ratio of NH_(4)^(+)-N to NO_(3)^(-)-N showed a downward trend in all regions,but the annual average ratio was commonly greater than 1,indicating that reduced nitrogen was dominated in nitrogen deposition.The acidity of precipitation in Southeast China was relatively higher,but the concentration of acidic ions (SO_(4)^(2-)and NO_(3)^(-)) was lower,indicating that the acidity of precipitation was also influenced by the alkaline ions (Ca^(2+)and NH_(4)^(+)).The annual changes in concentrations of NO_(3)^(-),NSS-SO_(4)^(2-)and NH_(4)^(+)were not significant in Xiamen and Xi'an,while the pH value and the ratio of the neutralizing potential to the acidifying potential (NP/AP) showed a significant upward trend.The value of NP/AP in Xi'an was significantly higher,reflecting that the neutralization capacity in dust in Xi'an was higher than that in the Southeast China.