夏季岩溶区河流的水化学及碳汇动态变化——以桂林漓江为例

Dynamic Changes to Water Chemical and Carbon Sinks of Karst River in Summer——A Case Study in the Li River of Guilin

在2012年7月6日至2012年7月13日期间,对漓江进行每两小时一次的高频率昼夜监测,分析河流的水化学和碳汇动态变化特征,研究表明:监测期间漓江河水的pH值介于7.83～8.44之间,平均值为8.14,呈弱碱性;HCO3-质量浓度的变化范围为87.26～93.36mg/L,平均值为90.02mg/L,受到降雨稀释效应影响,由于河水温度的变化及其水生植物的光合作用和呼吸作用引起CO2浓度变化导致HCO3-具有白天低夜晚高的特点;漓江受流域的岩溶作用影响强烈,SIc变化为0.09～0.67,平均值为0.38,呈过饱和状态,SIc变化趋势和pH值变化相似,表现为白天较高,夜晚较低;p(CO2)的变化范围为41.28～176.08Pa,平均值为88.63Pa,p(CO2)的变化与SIc刚好相反.监测期间漓江的碳汇量总体呈不断降低的趋势,从监测初期的1 873g/s下降到最后的1 173g/s,平均碳汇量为1 525g/s.通过分析发现碳汇量与流量显著相关(R2=0.992 1),碳汇量与HCO3-质量浓度的相关性则较低(R2=0.348 6).通过计算得知,本次监测期间漓江阳朔监测断面的碳汇量为955.31t.

In order to investigate the chemical analysis of water chemistry and dynamic characteristics of carbon sinks,the high-frequency diurnal monitoring was carried out in Li River from 6 to13 of July in 2012.The results show that the average pH value of Li River is 8.14,the water is weak alkaline during monitoring;the variation range of HCO-3 is 87.26~93.36 mg/L with an average being 90.02 mg/L,HCO-3 is affected by dilution effect of rainfall,and its characteristics is low in daytime and high at night.Li River is intensively affected by the karstification of basin,so the SIc varies between 0.09~0.67 with an average being 0.38,and it shows over saturation state,the trend of Sic similar to pH change,which mainly manifests as higher in daytime and lower at night.the variation range of p（CO2） is 41.28~176.08 Pa,the average being 88.63 Pa,then the change of p（CO2） is opposite to Sic,which mainly manifests as higher at night and lower in daytime.Carbon sinks of Li River is declined in general during monitoring,which from 1 873 g/s in initial decreased to 1 173 g/s in the last,and its average is 1 525 g/s.Correlated analysis shows that significant correlation is found between carbon sink and flow（R2=0.992 1）,moreover,positive correlation between carbon sink and HCO-3 is found flow（R2=0.348 6）.The amount of carbon sink of monitoring section at Yangshuo in Li River is 955.31 t,which is calculated by hydrochemistry-runoff method in flood process.