典型自然河道形态结构差异对水体自净作用的影响

Influence of Typical Structures of a Natural River on Self- purification of Water

深潭-急流-沙(河)滩是天然河道的一种基本结构单元,分析认为,深潭-急流-沙(河)滩系统由于结构单元不同的环境异质性,水体的自净作用会增强。本文以赤水河为例,对其进行采样分析,测定其水质指标,检验典型自然河道形态结构对水体自净的影响,为河流生态修复提供理论依据。结果表明:赤水河深潭水体中总氮、硝酸盐氮、氨氮浓度大于急流,而溶解氧、BOD5、COD、总磷浓度表现为急流大于深潭。方差分析表明,深潭-急流总氮、BOD5浓度在枯水期和丰水期均差异不显著,枯水期深潭-急流硝酸盐氮、氨氮、溶解氧、总磷浓度差异极显著(P<0.01,n=9),丰水期深潭-急流硝酸盐氮、氨氮、溶解氧、总磷浓度差异均不显著。就采样时期来看,总氮、硝酸盐氮、氨氮、溶解氧、BOD5、COD浓度均表现为枯水期大于丰水期,而总磷浓度表现为丰水期大于枯水期。以上结果表明,水体在经过深潭-急流-沙(河)滩这一结构单元时水质会有差异,河流中不断重复出现的深潭-急流-沙(河)滩系统能有效的改善河流水质,提高水体的自净能力。

Deep pool- rapid stream- beach system is a basic structural unit of a natural river. The qualitative analysis indicates that self- purification may be enhanced due to environmental differences among the structural units in the deep pool- rapid stream- beach system. In this study,nine of the ＂deep pool- rapid stream- beach system＂in upstream,midstream and downstream of Chishui River were researched,and water quality indicators were determined to analyze the influence of typical structures of a natural river on water purification. The results indicated that the total nitrogen,nitrate nitrogen and ammonia nitrogen values in deep pool was greater than those in rapid stream,while dissolved oxygen,COD,BOD5 and total phosphorus in deep pool was less than those in rapid stream. Concentrations of total nitrogen,nitrate nitrogen,ammonia nitrogen,dissolved oxygen,BOD5,and COD in water bodies were relatively greater in the low water period than in the high water period,while total phosphorus concentration presents an opposite result. These results indicated that water quality changes after water in river has flown through deep pool- rapid stream- beach system,and the repetitive occurrence of deep pool- rapid stream- beach system in a river may effectively improve the water quality of the river and increase self- purification capacity of water.