In order to estimate the air-surface mercury exchange of grasslands in temperate climate regions, fluxes of gaseous elemental mercury (GEM) were measured at two sites in Switzerland and one in Austria during summer 2006. Two classic micrometeorological methods (aerodynamic and modified Bowen ratio) have been applied to estimate net GEM exchange rates and to determine the response of the GEM flux to changes in environmental conditions (e.g. heavy rain, summer ozone) on an ecosystem-scale. Both methods proved to be appropriate to estimate fluxes on time scales of a few hours and longer. Average dry deposition rates up to 4.3 ng m−2 h−1 and mean deposition velocities up to 0.10 cm s−1 were measured, which indicates that during the active vegetation period temperate grasslands are a small net sink for atmospheric mercury. With increasing ozone concentrations depletion of GEM was observed, but could not be quantified from the flux signal. Night-time deposition fluxes of GEM were measured and seem to be the result of mercury co-deposition with condensing water. Effects of grass cuts could also be observed, but were of minor magnitude.
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机译:为了估计温带气候区草原的空气表面汞交换,2006年夏季在瑞士的两个站点和奥地利的一个站点测量了气态元素汞的通量。两种经典的微气象方法(空气动力学和修正的鲍文比) )已用于估算GEM净汇率,并确定GEM通量对生态系统规模的环境条件(例如大雨,夏季臭氧)变化的响应。事实证明,这两种方法均适用于在数小时或更长时间的时间尺度上估算通量。测量的平均干沉降速率最高为4.3 ng m -2 sup> h -1 sup>,平均沉积速度最高为0.10 cm s s -1 sup>。表明在活跃植被时期,温带草原是大气汞的一个小净汇。随着臭氧浓度的增加,观察到了GEM的消耗,但无法从通量信号中进行量化。测量了GEM的夜间沉积通量,这似乎是汞与冷凝水共沉积的结果。还可以观察到割草的影响,但影响较小。
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