青海海北高寒湿地近地层大气CO_2浓度的变化特征

采用快速响应红外气体分析仪对青海海北高寒湿地大气CO2浓度进行连续监测,分析2004年CO2浓度变化特征表明,CO2浓度存在明显的日、季变化,日、年内均表现“U”型变化特征。这些变化与植被生理活动、土壤呼吸、大气逆温层、及湍流交换强度等有关。自1月到7月CO2浓度的日变化过程中,日最高值出现时间在日出前后的5:00到9:00,并随7月的到来逐渐提早,日出后下降,约在下午15:00左右为最低,日落后又逐步升高。7月以后日最高值出现时间随时间推移又滞后,最低提早。一年中,月平均浓度最低值出现在7月份,最高值则在10月。观测表明,2004年海北高寒湿地CO2年平均浓度为315.3μmol/mol,月平均最高为335.0μmol/mol(10月),月平均最低值为270.1μmol/mol(7月)。统计海北高寒湿地旬平均CO2浓度与气象因素线性相关关系表明,海北高寒湿地CO2浓度与大多数气象因子有显著的负相关关系,但与土壤温度、气压、相对湿度等的相关关系不明显。

Changes of Surface Atmospheric CO2 Concentration in Alpine Swamp of Northern Qinghai

Surface atmosphericcarbon dioxide concentration was measured continuouslywith an anemometer`s temperature and open-path CO2analyzer,and then CO2concentration change of alpine swamp in Northern Qinghai was analyzed during 2004.It was suggested that there were distinct daily and seasonal change in CO2concentration,present a "U"pattern changing mode during a day and a year,all those changes were correlatedwith vegetation physiological activity,soil respiration,atmospheric trade inversion layerand overfall exchange intensity.As for diurnal variation of CO2 concentration from January to July,the maximum CO2 concentration appeared during 05:00 to 09:00(Beijing Standard Time),and became earlier gradually from January to July;CO2 concentration decrease obviously after sunrise,the minimum value appeared around 15:00,and then,increased after sunset.The time of maximum CO2concentration was lag after July,and there was no obviously change for the time of minimum CO2 concentration.As for monthly change,the maximum monthly average CO2 concentration was in July and the minimum month was in October.Observation results showed that average CO2 concentration of 2004 was 315.3μmol·mol-1,the maximum monthly average was 335.0μmol·mol-1(October),and theminimum monthly average was 270.1μmol·mol-1(July).According to statistic analysis results,there were negative correlations between average CO2 concentration and most of climate factors in a period of ten days.However,there were no distinct correlation with soil temperature,air pressure and relative humidity.