阿拉善流动沙漠区沙层CO2浓度与昼夜变化规律研究

利用红外CO2监测仪,对全球最高大的巴丹吉林诺尔图湖东大沙山、沙坡头流动沙丘和民勤流动沙丘进行了19个钻孔的CO2浓度昼夜观测。结果表明,阿拉善流动沙漠区空气中CO2浓度较1 m、2 m、3 m、4 m、5 m沙层中CO2浓度均低,表明在植物极稀少的流动沙漠区温暖季节会向空气中释放CO2,是大气CO2的来源区。沙层不仅白天向空气释放CO2,夜间也在释放CO2。在极端干旱的阿拉善流动沙漠区沙层2 m深处CO2浓度一般较1 m、3 m、4 m、5 m的大,但也有个别例外。流动沙漠区沙层CO2浓度的昼夜变化也具有明显的规律性,各个深度沙层CO2浓度从早8时至次日7时均呈现由低到高再到低的变化规律。沙层CO2浓度与昼夜温度变化呈显著正相关关系。在极端干旱的阿拉善流动沙漠区水分含量较高的沙层CO2浓度明显高,表明沙层含水量高低是决定沙层CO2浓度水平的主要因素。

CO2 concentration and its diurnal variation in sand layer of mobile sand dunes of Alxa Desert

In order to explore CO2 concentration in the sand layer of the mobile sand dunes of the Alxa Desert, and its influence atmospheric CO2 and its role in the global carbon cycling, the research team utilized infrared CO2 monitor to observe diurnal variation of CO2 concentrations in the 19 holes drilled in mobile sand dunes of the desert. Results show that the CO2 concentration in the air was lower than that in the sands 1 m, 2 m, 3 m, 4 m or 5 m deep, which indicates that the mobile sand dunes with rare plants release CO2 into the atmosphere both at night and in the daytime during the warm season, acting as CO2 sources. In the sand layer 5 m deep in the profile, the CO2 concentration is markedly higher than that in the air, suggesting that the potential of CO2 release is very big. In the extremely arid part of the Alxa Desert, CO2 concentration is usually higher in the sand layer 2 m deep than in the layers 1 m, 3 m, 4 m or 5 m deep, but with some individual exceptions. Diurnal variation of CO2 concentration in the area follows a specific law in all the layers, showing a curve of saddle shape from 08:00 am to 07:00 am the next day, and a significant positive relationship with the temperature in the profile. In that region, the sand layer higher in moisture content is significantly higher in CO2 concentration, which indicates that moisture content in the sand layers is the major factor determining CO2 concentration in the layer.