闽江感潮河段非雨季、雨季不同形态氮的时空分布及影响因素

Abstract

【中文摘要】选取非雨季(2018年11月)和雨季(2019年4月)对闽江感潮河段7个断面进行水样采集,研究不同季不同形态氮的时空分布规律,采用相关性分析及主成分分析并结合2016—2019年来水情况,深入探讨不同季氮组分分布及转化的影响因素.结果表明:1)非雨季盐水入侵明显,各理化指标盐度、温度、pH 和溶解氧的波动均强于雨季.2)非雨季上游NH4+-N低于雨季,下游则高于雨季,而非雨季NO3--N和总氮(TN)总体均高于雨季.从上游到下游,非雨季NH4+-N变化波动较大,NO3--N平缓而TN呈轻微上升;雨季NH4+-N、NO3--N和TN变化均较平缓.3)相关性分析表明非雨季的氮转化活跃.雨季NH4+-N浓度是影响TN浓度的主要因素.结合主成分分析及长期上游来水氮的污染负荷发现,人为排放和各形态氮的相互转化是非雨季不同形态氮变化的主要因素,雨季水体反硝化对不同形态氮的分布发挥重要作用,而上游来水的氮污染负荷对不同形态氮的浓度影响较小. 【Abstract】Two field surveys in the Minjiang River tidal reach were conducted to investigate the spatiotemporal distribution of different species of nitrogen during non-monsoon season (November, 2018) and monsoon season (April, 2019),respectively with a total of 7 cross-sections. Then，the influencing factors of nitrogen distribution in different seasons were explored using correlation analysis，principal component analysis and historical data of the upstream water environment changes from 2016 to 2019. The results showed that salinity intrusion was stronger in the non-monsoon season than that in the monsoon season，which led salinity， temperature，pH and dissolved oxygen to fluctuate more significantly in the non-monsoon season. As for different nitrogen species, the upstream NH+ -N concentration in the non-monsoon season was lower than that in the monsoon season while an opposite trend was present in the downstream. However，the N〇3--N and total nitrogen (TN) concentrations in the whole river reach in the non¬monsoon season were higher than those in the monsoon season. From upstream to downstream，the NH4+ -N concentration fluctuated significantly,the N〇3--N concentration kept the same level and TN increased slightly in the non-monsoon season. While in the monsoon season，the concentrations of all nitrogen species (NH4+-N，N〇3_-N and TN) changed slightly. Finally, correlation analysis suggested that the nitrogen transformation was active in the non-monsoon season. In the monsoon season，the NH4+ -N concentration was the key factor controlling the fluctuation of the TN concentration. Combined with the principal component analysis and upstream inflow nitrogen pollution load，in the non-monsoon season,anthropogenic discharge and the nitrogen cycle in different nitrogen species were the main factors of nitrogen species distribution, while in the monsoon season，the denitrification process played an important role in the distribution of different nitrogen species. The upstream inflow nitrogen pollution load had little influence on the concentration of different nitrogen species.