苏北海岸带盐沼二氯甲烷和1,2-二氯乙烷通量沿高程梯度的变化特征

The flux of dichloromethane and 1,2-dichloroethane along an elevational gradient of a coastal salt marsh,East China

2004年4月到2005年1月在我国东部海岸带盐沼上沿高程梯度采用静态箱技术原位测定二氯甲烷（DCM,CH2Cl2）和1,2-二氯乙烷（1,2-DCA,CH2CH2Cl2）气体通量。为确定高等植物对通量的贡献,进行了高等植物地上部分去除实验。也对通量与生态因子间关系进行了分析。研究结果表明：在高程梯度上,生长季（4~10月份）盐沼整体上表现为DCM和1,2-DCA的净汇,其中,米草带和光滩对DCM和1,2-DCA的消耗率最高。非生长季（11月到翌年3月份）表层冻结的植被带表现为DCM和1,2-DCA的弱源,但是受非生长季采样量不足的限制,难以确定盐沼究竟是DCM和1,2-DCA的净源还是净汇。高等植物去除实验结果表明生长季高等植物地上部分是DCM和1,2-DCA的重要汇,而非生长季为净源,然而高等植物排放和消耗DCM和1,2-DCA气体的基本机制还不清楚。盐沼DCM和1,2-DCA通量正相关于光照强度、土壤可溶性盐含量、土壤有机质和全氮含量,而负相关于土壤温度、硫酸盐含量和大气中DCM和1,2-DCA浓度。这表明盐沼对DCM和1,2-DCA的吸收可能与相对较高的DCM和1,2-DCA大气背景浓度和丰富的土壤有机质含量有关。

The fluxes of dichloromethane（DCM,CH2Cl2） and 1,2-dichloroethane（1,2-DCA,CH2CH2Cl2） were seasonally measured using static flux chambers from April 2004 to January 2005 along an elevational gradient of a coastal salt marsh in eastern China.To estimate the contribution of higher plants to the fluxes,plant aboveground biomass was experimentally removed and the flux difference between the treatment and the intact was tested.In addition,the fluxes were analyzed in relation to soil and weather conditions.Along the elevational gradient,the salt marsh generally acted as a sink for the compounds in the growing season（from April to October）,and the maximum negative flux occurred at the cord-grass marsh for DCM and at mudflat for 1,2-DCA.In the non-growing season（from November to March）,the vegetated marsh was a source of DCM and 1,2-DCA.However,because of the lack of extensive sampling in the non-growing season,it is hard to determine whether the marsh under study is a source or sink for DCM and 1,2-DCA.Comparative analyses showed that the higher plants acted as an important sink for DCM and 1,2-DCA in the growing season,but a net source for them in the non-growing season,even during the frozen time.The mechanism responsible for the release and removal processes of plants is not clear.The fluxes of DCM and 1,2-DCA were positively correlated to light intensity,soil dissolved salt,soil organic matter,and TN content,but were negatively correlated to soil temperature,sulfate content,and their ambient concentrations.This suggests that the net consumption of DCM and 1,2-DCA observed in the study marsh may result from the high ambient concentrations and enriched soil organic matter that resulted in anoxic sediments.