西江溶解有机碳的输送对典型洪水过程的响应

The response of dissolved organic carbon export to the typical flood event in the Xijiang River

对2005年6月西江干流出现特大洪水期问及其前后的溶解有机碳（DOC）进行连续采样分析．结果表明，DOC浓度对流量变化的响应不敏感（n=43，R^2=0．23，p〉0．0．5），尽管流量有6—7倍的变化，但DOC浓度的变化不到30％．洪水前夕、洪水期间及洪水过后DOC平均浓度逐渐降低，且洪水过后西江下游各个采样点的DOC浓度明显低于洪水前夕．DOC的输出量主要受地表径流深度的影响，二者之间存在着显著的线性相关关系．DOC荷载通量与流量密切相关，通过建立二者之间的线性回归方程可以计算出DOC的输出量，洪水期间DOC的输出量为4．5×10^10g．

A once-in-a-century flood was taken place in the Xijiang River in June 2005. Continuous monitoring of DOC concentration had been carried out during, before and after this super flood. The results show that DOC variation was, relatively independent of the discharge variation. Although the discharge had changed 6 - 7 folds, the DOC variation was less than 30% during the same period, which is very different from other rivers that DOC concentration increased quickly with the increasing discharge. DOC concentrations were in the range of 0.92 - 1.22 mg·L^-1 at Wuzhou gauge station and 0.82- 1.34 mg·L^-1at Makou gauge station during the flood period. For all those sampling stations, DOC concentrations before the flood are higher than that after the flood. SpatiaUy, DOC concentration decreased downstream the main channel. DOC yield was very closely related to the runoff depth, suggesting that DOC yield is almost entirely under the control of the surface flow. DOC flux during the flood can be calculated by fitting a linear regression equation between the DOC load and the discharge from all measured DOC values at Wuzhou gauge station. There was 4.5 ×10^10g dissolved organic carbon export during the super flood.