达里诺尔湿地水环境和鱼类多样性调查Ⅲ.达里湖水体中的氮和磷含量及分布

达里湖是达里诺尔湿地的重要组成部分。2019年,对达里湖开展了野外调查并采集了水样,测定了水样的氮、磷含量和非离子氨含量与水体pH的关系,并将研究结果与以往的达里湖相对应的调查资料进行比较,探讨了达里湖水体中氮、磷含量特征的形成及其对达里湖鱼类物种多样性的影响。研究结果表明,2019年7月,达里湖水体中的COD_Cr和COD_Mn质量浓度分别为125.10 mg/L和19.18 mg/L,1975~2019年明水期COD_Mn含量平均每年增加0.67%;水体中的总氮和总磷质量浓度分别为1.964 mg/L和1.870 mg/L,1994~2019年明水期其平均每年分别减少4.51%和增加1.90%;水体中的氨氮和总有效氮质量浓度分别为0.168 mg/L和0.490 mg/L,1975~2019年明水期其平均每年分别增加2.25%和4.59%;水体中的硝酸盐氮质量浓度为0.166 mg/L,2004~2019年明水期其平均每年增加24.78%;水体中的活性磷酸盐质量浓度和总有效氮含量与活性磷酸盐含量的比值分别为5.729 mg/L和0.086,1975~2019年明水期其平均每年分别增加1.23%和减少0.82%;水体中的非离子氨含量占总氨含量的比例为19.23%;水体中的非离子氨质量浓度为0.031 mg/L,1975~2019年明水期其平均每年减少0.28%。1975年以来,达里湖水体中的活性磷酸盐含量持续高于总有效氮含量,水体中的氮、磷组成极不平衡;水体中的化学需氧量、总磷、总氮和非离子氨含量持续超标,达里湖水体处于中度或重度富营养化状态,其对湖中原有鱼类的多样性尚无负面影响,但是对未来鱼类多样性健康发展构成了潜在威胁。

Investigation of Water Environment and Fish Diversity in Dalinor WetlandsⅢ.Contents and Distribution of Nitrogen and Phosphorus in the Waters in Dali Lake

Dali Lake is an important part of the Dalinor wetlands.This paper reported the investigation results of nitrogen,phosphorus and pH in the water of Dali Lake in 2019,and also discussed the influence of contents of nitrogen and phosphorus in the water on fish diversity.The contents of COD_Crand COD_Mnwere 125.10 mg/L and 19.18 mg/L in the water of Dali Lake in July 2019,respectively;and the content of COD_Mnincreased by 0.67%annually during open water period from 1975 to 2019.The contents of total nitrogen and total phosphorus were 1.964 mg/L and 1.870 mg/L in the water of Dali Lake in July 2019,respectively;the content of total nitrogen decreased by 4.51%and the content of total phosphorus increased by 1.90%per year during open water period from 1994 to 2019.The contents of ammonia nitrogen and total available nitrogen were 0.168 mg/L and 0.334 mg/L in the water of Dali Lake in July 2019,respectively;they increased by 2.25%and 4.59%per year respectively during open water period from 1975 to 2019.The content of nitrite nitrogen was 0.166 mg/L in the water of Dali Lake in July 2019,the content of nitrite nitrogen increased by 24.78%per year during open water period from 2004 to 2019.The content labile phosphate and ratio between the content of total available nitrogen and the content of labile phosphate wer 5.729 mg/L and 0.086 in the water of Dali Lake in July 2019,the content labile phosphate increased by 1.23%and the ratio decreased by 0.82%per year during open water period from 1975 to 2019.The content of non-ionic ammonia accounted for 19.23%of the content total ammonia.The content of non-ionic ammonia was 0.031 mg/L in the water of Dali Lake in July 2019,the content of non-ionic ammonia decreased by 0.28%per year during open water period from 1975 to 2019.The content labile phosphate has been consistently more than the content of total available nitrogen in the water of Dali Lake since 1975,and the composition of nitrogen and phosphorus in the water was extremely unbalanced.The contents of chemical oxygen demand,total phosphorus,total nitrogen and non-ionic ammonia continued to exceed the standard of classⅢwater;and the water in Dali Lake was in the state of moderate of severe eutrophication in 2019,which poses a potential threat to the healthy development of the future fish diversity,but still has no negative effect on the diversity of the original fish in the lake at present.