土壤CO_(2)浓度变化特征及其对岩溶碳循环的影响

Characteristics of Soil CO_(2) Concentration Change and Its Influence on KarstCarbon Cycle

为探究土壤CO_(2)浓度变化特征及其对岩溶碳循环的影响,于2018年6—12月对重庆市南川区后沟泉水化学及泉域上覆土壤CO_(2)(监测点土地利用类型为玉米-油菜轮作地)进行为期7个月的连续监测和采样,并结合1—5月的监测数据,定量分析旱雨季土壤CO_(2)浓度与岩溶碳汇量的季节性演变特征及二者的相互关联性.结果表明:①土壤CO_(2)浓度具有显著的季节性变化特征,主要表现为雨季较高、旱季较低,其最高值和最低值分别出现在9月(13316μmol/mol)和1月(2262.63μmol/mol).②温度与土壤CO_(2)浓度之间存在较强的正相关关系(R^(2)=0.82,0.001<P<0.005),降水量与土壤CO_(2)浓度之间不具相关性(R^(2)=0.17,P>0.5),说明土壤CO_(2)浓度主要受温度的影响.③泉水Ca^(2+)+Mg^(2+)、HCO_(3)^(−)浓度在雨季明显高于旱季,而水体CO_(2)净消耗量在旱雨季无较大差异,这可能是由于受土壤CO_(2)效应、降水稀释效应和H_(2)SO_(4)/HNO_(3)释放CO_(2)的共同影响.研究显示,土壤CO_(2)浓度的变化特征表现为季节性差异,但在土壤CO_(2)浓度及外部环境的多重影响下,岩溶碳循环的季节性变化并不明显.

To study the characteristics of soil CO_(2) concentration change and its influence on the karst carbon cycle,the spring chemistry,and CO_(2) of the overlying soil in the spring area of Hougou,Nanchuan District,Chongqing(the land use type of the monitoring site is maize-oilseed rape rotation)were monitored and sampled for seven months.The seasonal evolution characteristics of soil CO_(2) concentration and the karst carbon sink during the dry and rainy seasons and their correlations were quantitatively analyzed.The results showed that:(1)Soil CO_(2) concentration had obvious seasonal variation characteristics,which was mainly higher in the rainy season and lower in the dry season.The highest and lowest values appeared in September(13,316μmol/mol)and January(2,262.63μmol/mol),respectively.(2)There was a strong positive correlation between temperature and soil CO_(2) concentration(R^(2)=0.82,0.001<P<0.005),but there was no correlation between precipitation and CO_(2) concentration(R^(2)=0.17,P>0.5),which indicated that soil CO_(2) concentration was mainly influenced by temperature.(3)The concentrations of Ca^(2+)+Mg^(2+)and HCO_(3)^(−)in the rainy season were significantly higher than those in the dry season,while the net CO_(2)consumption in water bodies was significantly different between the dry and rainy seasons.This may be due to combined effects of soil CO_(2),precipitation dilution,and CO_(2)released by H_(2)SO_(4)/HNO_(3).The study showed that the variation of soil CO_(2)concentration was characterized by seasonal differences,but the seasonal variation of the karst carbon cycle was not obvious under the multiple effects of soil CO_(2)concentration and external environmental influences.