梅溪湖表层沉积物营养盐和有机质分布特征及污染评价

Distribution and Pollution Assessment of Nutrients and Organic Matter in Surface Sediments of Meixi Lake

探究梅溪湖沉积物营养物的空间分布特征及污染程度,为梅溪湖等城市景观湖泊富营养化防治提供科学依据和理论支持。2020年11月至2021年7月,分季节采集了梅溪湖表层沉积物(0~10 cm),分析其氮磷和有机质等指标的时空分布特征和污染程度。结果表明:沉积物(0~10 cm)总氮、氨氮、硝氮、总磷、有效磷和有机质的平均含量分别为(1654.68±754.22)、(24.66±20.02)、(13.60±2.33)、(512.60±281.39)、(8.58±6.81)mg/kg和(2.84±1.43)%。湖区东部受人类活动影响较大,营养物和有机质含量最高。沉积物总磷和硝氮含量在春季最高(4月),冬季(1月)最低;有效磷含量在春季(4月)最高,夏季(7月)最低;沉积物总氮、氨氮和有机质含量没有明显的季节差异。梅溪湖沉积物总氮和总磷的含量变幅分别为667~4000 mg/kg和184~1475 mg/kg,均已超出我国东部浅水湖泊沉积物营养物参考阈值范围;总氮和总磷的标准指数变幅分别为1.21~7.27和0.31~2.46,总氮全部超标,梅溪湖生态环境质量受氮元素污染较为严重。相关分析表明,沉积物有机质与各形态氮磷营养盐均显著正相关,说明沉积物有机质的降解和释放对梅溪湖氮磷营养盐具有重要影响。

Meixi Lake is a shallow urban lake,and its sediments reflect the aquatic ecology of the lake and greatly influence lake eutrophication.In this study,we explored the temporal and spatial distribution and nutrient levels in the surface sediment of Meixi Lake,aiming to provide basic data and theoretical evidence for preventing eutrophication of Meixi Lake and protecting water quality in urban lakes.From November 2020 to July 2021,surface sediments(0-10 cm)of Meixi Lake were sampled seasonally at seven sites(S1-S3 in the southwest area,S4-S5 in the central area,and S6-S7 in the northeast area)for the determination of TN,NH^(+)_(4)-N,NO^(-)_(3)-N,TP,available phosphorus(AP),and organic matter(OM).Sediment(0-10 cm)concentrations(mean±SD)of TN,NH^(+)_(4)-N,NO^(-)_(3)-N,TP,AP and OM were,respectively,(1654.68±754.22),(24.66±20.02),(13.60±2.33),(512.60±281.39),(8.58±6.81)mg/kg and(2.84±1.43)%.Human activities greatly influence the spatial distribution of nutrients in Meixi Lake sediments.Spatially,the highest nutrient and organic matter concentrations occurred in the eastern area of the lake.Seasonally,sediment concentrations of TP and NO^(-)_(3)-N were highest in spring(April)and lowest in winter(January),while AP was highest in spring(April)and lowest in summer(July).There were no obvious seasonal differences in sediment levels of TN,NH^(+)_(4)-N or OM.Sediment TN and TP in Meixi Lake ranged from 667 mg/kg to 4000 mg/kg and 184 mg/kg to 1475 mg/kg,respectively,exceeding the reference threshold range for nutrients in the sediments of shallow lakes in eastern China,with TN and TP standard index ranges of 1.21-7.27 and 0.31-2.46,respectively.TN levels in surface sediments at all sites exceeded the standard,and excess nitrogen seriously affects the ecological environment quality of Meixi Lake,threatening the lake ecosystem.Correlation analysis shows a significant positive correlation between sediment OM and TN,TP,AP,NH^(+)_(4)-N,and NO^(-)_(3)-N,indicating that degradation of organic matter and subsequent release of nutrients in Meixi Lake sediments has a large impact on nitrogen and phosphorus levels.