梅溪湖表层沉积物营养盐和有机质分布特征及污染评价

梅溪湖属于城市浅水湖泊，其沉积物特征可反映湖泊的水生态环境状况，对防止湖泊富营养化具有重要意义。2020年11月至2021年7月，分季节对梅溪湖表层沉积物（0～10 cm）进行了采样，分析了沉积物TN、NH4+、NO3-、TP、有效磷（AP）和有机质（OM）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）TN、NH4+、NO3-、TP、AP和OM的平均含量依次为1654.68± 754.22 mg/kg、24.66± 20.02 mg/kg、13.60± 2.33 mg/kg、512.60± 281.39 mg/kg、8.58± 6.81 mg/kg和2.84± 1.43 %。湖区东部营养物和有机质含量最高。人类活动对梅溪湖表层沉积物营养盐的空间分布有着较大的影响。梅溪湖沉积物TP和NO3-含量在春季最高（4月份），冬季（1月）最低。AP含量在春季（4月）最高，在夏季最低（7月份）。沉积物TN、NH4+和OM含量没有明显的季节差异。梅溪湖沉积物TN和TP的含量变幅分别为667～4000 mg/kg和184～1475mg/kg，均已超出我国东部浅水湖泊沉积物的营养物参考阈值范围；TN和TP的标准指数变幅分别为1.21～7.27和0.31～2.46，TN全部超标，梅溪湖生态环境质量受N元素的影响较为严重，对湖泊生态系统安全构成了一定的威胁。相关分析表明，沉积物OM与TN、TP、AP、NH4+、NO3-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。

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

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, NH4+-N, NO3--N, TP, available phosphorus (AP), and organic matter (OM). Sediment (0-10 cm) concentrations (mean±SD) of TN, NH4+-N, NO3--N, TP, AP and OM were, respectively, (1 654.68±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 NO3--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, NH4+-N or OM. Sediment TN and TP in Meixi Lake ranged from 667 mg/kg to 4 000 mg/kg and 184 mg/kg to 1 475 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, NH4+-N, and NO3--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.