土地利用类型对漓江流域会仙岩溶湿地水系氮磷的影响

Effects of Land Use Types on Nitrogen and Phosphorus in Rivers of the Huixian Karst Wetland in the Lijiang River Basin

为揭示下垫面土地利用和岩溶特征对漓江流域会仙岩溶湿地水系氮磷的影响,研究于2017年10月至2021年9月在睦洞河、会仙河和相思江地表水系进行月尺度氮磷监测。统计分析了21.79~376.42 km~2集水范围内的地表水系氮磷排放特征,并应用Pearson相关性分析法和灰色关联法探究了研究区水系氮磷排放浓度与土地利用类型、岩溶地貌分布、水文气象等因素之间的关系,结果表明:(1)监测期内水系总氮(TN)污染较总磷(TP)严重,水样的TN和TP浓度分别介于0.30~27.55 mg/L和0.03~2.49 mg/L之间,70.3%水样(样本数n=518)的TN>1.0 mg/L,35.1%水样的TP>0.2 mg/L;受水文气象影响,TN和TP浓度峰值出现在旱季,均值在雨季下降。(2)水系中氮磷主要来源于受人为活动影响较大的农业用地(水田、旱地和果园);沟塘湿地有助于氮磷减排,覆盖型岩溶区氮磷输出水平较高。(3)相比氮素(NH~+-N、NO~--N和TN),磷素(TP和TDP)浓度受降水量的影响更大,雨季尤为明显。充分了解岩溶湿地水系氮磷污染现状及其主要影响因素有助于科学管理和保护流域水质。

When the factors affecting the spatial and temporal variation of nitrogen and phosphorus in rivers of karst watershed are considered,the unique karst geomorphic and its accompanying land use features of underlying surface cannot be ignored.To reveal the effects of karst feature and land use types on nitrogen and phosphorus of the Huixian karst wetland rivers,water samples from Mudong River,Huixian River and Xiangsi River were collected monthly for nitrogen and phosphorus analysis from October 2017 to September 2021.Based on the statistical analysis of river N and P concentration in catchments ranging from 21.79 to 376.42 km~2,in combination with Pearson and Grey correlation analysis,the relationship between N,P concentrationof rivers and the area proportion of landuse type,karst landform,as well as the hydrometeorology factors was studied.The results showed that (1) During the monitoring period,total nitrogen(TN)pollution was more serious than total phosphorus(TP)pollution.The concentrations of TN and TP varied from 0.30 to 27.55 mg/L and 0.03 to 2.49 mg/L,respectively,with 70.3%of 518 samples had TN>1.0 mg/L and 35.1%had TP>0.2 mg/L.Under the influence of hydrometeorology,the peak concentrations of TN and TP appeared in the dry season,and the mean concentrations decreased in the wet season.(2) The nitrogen and phosphorus in rivers mainly came from agricultural land(include paddy field,dry land,and orchard)which was significantly affected by human activities.Wetland and ponds contribute to nitrogen and phosphorus reduction.The covered karst area has a positive effect on nitrogen and phosphorus emission levels.(3) The correlation between the concentrations of phosphorus(TP and TDP)and precipitation is stronger than that of nitrogen(NH-N,NON and TN),especially in the wet season.This research helps to improve the knowledge about the status and main influence factors of N and P pollution in Huixian karst wetland rivers.It is important to pay attention to nitrogen and phosphorus in karst wetland system for water quality safety and management.