Seasonal variation of transport pathways and potential source areas at high inorganic nitrogen wet deposition sites in southern China

This study attempts to identify the dominant transport pathways,potential source areas,and their seasonal variation at sites with high inorganic nitrogen(IN)wet deposition flux in southern China.This is a long-term study(2010-2017)based on continuous deposition measurements at the Guangzhou urban site(GZ)and the Dinghushan Natural Reserve site(DHS)located in the Pearl River Delta(PRD)region.A dataset on monthly IN concentration in precipitation and wet deposition flux were provided.The average annual fluxes measured at both sites(GZ:33.04±9.52,DHS:20.52±10.22 kg N/(ha·year))were higher,while the ratios of reduced to oxidized N(GZ:1.19±0.77,DHS:1.25±0.84)were lower compared with the national mean level and the previous reported level throughout the PRD region.The dominant pathways were not always consistent with the highest proportional trajectory clusters.The transport pathways contributing most of deposition were identified in the north and northnortheast in the dry season and in the east-southeast,east,and south-southwest in the wet season.A weighted potential source contribution function(WPSCF)value>0.3 was determined reasonably to define the potential source area.Emission within the PRD region contributed the majority(≥95%at both sites)of the IN deposition in the wet season,while the contribution outside the region increased significantly in the dry season(GZ:27.86%,DHS:95.26%).Our results could help create more effective policy to control precursor emissions for IN fluxes,enabling reduction of the ecological risks due to excessive nitrogen.

福建省硫沉降量变化的分析与比较

应用中国科学院大气物理研究所建立的三维欧拉污染物输送模式模拟了1995、2000、2002年福建省本省排放源造成的和邻近省份排放源向其输送的硫沉降量,结果表明,福建省接收的硫沉降量有一半以上是由周围省份的远距离输送造成的。进而分析了每年4个季节硫沉降的变化特点,并结合福建省气象条件给出理论解释。最后,把这3年福建省SO2及SO42-年沉降量和各季节沉降量分别作了比较,结果显示,造成福建省SO2沉降的主要来源是本省的排放源,而SO42-沉降中外来源占很大比例,超过了50%。

亚洲粉尘的源区分布、释放、输送、沉降与黄土堆积

根据亚洲粉尘关键区域（中国沙漠、黄土高原、青藏高原和中国历史降尘区）大气气溶胶中１５～２８种元素的浓度一粒度分布、沉降速率和通量分析，以及元素示踪系统的进一步解析，发现中国北方沙漠存在两个粉尘地一气交换较活跃区域，即中国西部沙漠和北部沙漠高粉尘区，且证明这两个区域及其邻区是亚洲粉尘和黄土高原黄土主要源区的中心区域；通过对５个亚太区域粉尘沉降量的模式估算，得出亚洲粉尘释放总量每年约为８００Ｔｇ，约相当于全球沙漠排放总量的一半；粉尘与黄土的对比表明，亚洲粉尘区域尺度输送受季风环流控制，但间冰期时并不取决于尘暴过程，而全球尺度输送主要由高空西风完成，无论冰期、间冰期均受尘暴过程控制；粉尘通量的结果表明干沉降是粉尘在黄土区沉降的主要过程，巨晚第四纪粉尘沉积的再改造份额不超过其沉积总量的１０％；元素示踪系统应用于风成黄土，发现在间冰期北部沙漠源区输出的粉尘量增加，而在冰期西部源区输出的粉尘量增加。这种晚第四纪亚洲粉尘“源区摆动”的快速变化其实是全球千年尺度气候变化的一环，并可视为过去北半球大气环流长期变化的代用序列。