贵阳市2种不同类型草地的汞释放通量

利用动态通量箱法对贵阳市人工草坪和天然草地的汞释放通量进行了野外实测. 结果表明:春季和夏季的草地是大气中汞的来源，并未出现明显的季节性变化，其平均汞释放通量为(7.8±15.7)～(41.5±15.2) ng/(m2·h)，且天然草地的汞释放通量明显高于人工草坪. 草地的汞释放通量具有明显的日变化特征，白天汞释放通量显著高于夜间，最大值通常出现在午后，最小值则出现在夜间. 草地的汞释放通量与光照强度、土壤温度、大气温度呈显著的正线性关系，与大气相对湿度呈负线性关系. 大气中气态总汞的质量浓度是影响草地汞释放通量的另一个重要因素. 大气中气态总汞质量浓度的升高能够抑制草叶片向大气中释放汞，而高质量浓度的气态总汞可导致大气中的汞向草叶片的强烈沉降. 

Mercury Flux Rate of Two Types of Grasslands in Guiyang

Measurements of mercury exchange flux were conducted from cultivated lawn and forest wild grassland in Guiyang City by using a dynamic flux chamber method. Generally, lawn and grassland were the source of atmospheric mercury in spring and summer sampling campaigns. No seasonal change of Hg exchange fluxes wasobserved and the mean Hg fluxes ranged from 7.8±15.7 to 41.5±15.2 ng/(m2·h). The mean Hg flux from forest wild grassland was obviously higher than those from cultivated lawn. Hg fluxes between grassland and lawn and atmosphere exhibitedclearly diurnal cycle with elevated Hg fluxes in the daytime comparing to thoseat night, and the maximum Hg fluxes were generally observed in the afternoon and the lowest observed at night. Hg flux was positively linear with solar radiation, soil and air temperature, and negatively correlated with air relative humidity. Total gaseous mercury (TGM) concentration in the ambient air was another important factor that regulated Hg flux from grassland. Elevated atmospheric TGM concentration could inhibit Hg emission from grass foliar, and extremely high TGM concentration was the primary reason causing high deposition flux to grass foliar.