都柳江河道急流-深潭-沙(砾)滩系统水质差异研究

Evaluations on the Difference of Water Quality of the Riffle-deep pool-benchland Systems of Watercourses in Duliujiang River

河流是流域生态系统的重要组成部分,河流形态结构与水质变化间关系研究可以为河流生态修复提供理论依据。河流是由急流-深潭-沙(砾)滩不断重复出现构成的系统,急流-深潭-沙(砾)滩是河流的基本结构单元,并以都柳江上、中、下游9个急流-深潭-沙(砾)滩单元为对象,测定了水质指标,分析了山区典型河道基本结构单元与水质变化之间的关系。结果表明:都柳江深潭水体中氮素浓度与pH值大于急流,其浓度分别是总氮0.97mg/L和0.87mg/L;硝酸盐氮0.60mg/L和0.56mg/L;氨氮0.22mg/L和0.20mg/L;pH8.22和8.14。而磷素、溶解氧、BOD5和COD则是深潭小于急流。其浓度分别是总磷0.0187mg/L和0.0202mg/L;正磷酸盐0.0070mg/L和0.0085mg/L;溶解氧11.93mg/L和13.50mg/L;BOD53.75mg/L和5.36mg/L;COD10.986mg/L和12.807mg/L。电导率深潭与急流相等,均为169.7μS/cm。方差分析表明,深潭与急流水体总氮和硝酸盐氮在夏季差异极显著;磷素和pH在春季差异极显著;电导率在秋季差异极显著;氨氮、溶解氧、BOD5和COD差异均不显著。研究工作显示,河流形态结构变化影响着水环境质量,急流-深潭-沙(砾)滩不断重复出现使河流水质得到改善,在河道生态修复中需要遵循河流形态结构规律以便提高河流的自净能力。

River is an important part of a watershed ecosystem and the understanding on relationship between river morphology and water quality may provide a theoretical basis for the river ecosystem restoration. A river is a continual system containing the repetitive basic structural unit,i.e.,the ＂riffle-deep pool-benchland＂systems in a river. In the study,nine of the ＂riffle-deep pool-benchland＂ systems respectively in the upstream,midstream and downstream of Duliujiang River were researched and water quality indicators were determined to analyze the relationship between water quality and the basic structural unit in the typical mountain rivers. The results showed that nitrogen and p H values in deep pool was greater than the riffle,while phosphorus,DO,BOD5 and COD concentration in deep pool was less than the riffle. Specifically, the concentration of TN,NO3-N and NH4＋-N was respectively 0.97mg/L,0.60mg/L and 0.22mg/L in deep pool and 0.87mg/L,0.56mg/L and 0.20 mg/L in riffle. p H was 8.22 in deep pool and 8.14 in riffle.The concentration of TP and orthophosphate was 0.018 7mg/L and 0.007 0mg/L in deep pool and 0.020 2mg/L and 0.008 5mg/L in riffle. The concentration of DO,BOD5,COD was 11.93mg/L,3.75mg/L and 10.986mg/L in deep pool and 13.50mg/L,5.36mg/L and 12.807mg/L in riffle. Conductivity was equal in both deep pool and riffle,which was 169.7μS/cm. Analysis of variance showed TN and nitrate nitrogen significantly different in riffle and deep pool in the summer;phosphorus and p H significantly different in the spring;conductivity significant difference in the fall;ammonia,DO,BOD5 and COD were not significantly different.Structural changes of river morphology affects water quality in river and with the repetitive emergence of the riffle-deeppool-benchland systems,the river water quality is improved. The study clarifies the effects of the unitary structures in a river on water quality.