National Engineering Laboratory for Lake Pollution Control and Ecological Restoration, Institute of Lake Environment and Ecology, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
Environ Sci Pollut Res Int. 2023 May;30(23):64363-64376. doi: 10.1007/s11356-023-26801-z. Epub 2023 Apr 17.
Nitrogen (N) in sediments was a key element of lake eutrophication. The spatial distribution characteristics of four parts N in surface sediments were investigated by sequential extraction method, including free nitrogen (FN), exchangeable nitrogen (EN), hydrolyzable nitrogen (HN), and residual nitrogen (RN). Modified models were utilized to describe the adsorption isotherms of ammonia nitrogen (NH-N) in sediments and thus predict the risk of N release. The correlation between environmental factors and N concentration was discussed, as well as the migration or transformation and release risk of N between different mediums. The results showed that spatial variations characteristics of N fractions were influenced by the lake topography and surrounding human activities. The content of total nitrogen (TN) in the sediments was 933.4 ~ 3006.8 mg/kg, with an average of 1835 mg/kg. The HN, RN, FN, and EN in sediments accounted for 66.85%, 21.35%, 6.82%, and 4.92% of TN, respectively. There was a significant correlation between each fraction of N and TN and also between different fractions of N (p < 0.01). Fitting by modified Langmuir model indicated that the adsorbed amounts of N in the sediments at maximum (Q) was, from greatest to least, southeast lake (2905.3 mg/kg) > southwest lake (1415.4 mg/kg) ≈ north lake (1424.6 mg/kg). Environmental parameters (pH, DO, C/N, etc.) affected the occurrence fraction of nitrogen, which could cause the persistent and increased risk of sustained release of high concentrations of endogenous N. N pollution in sediment and interstitial water is severe, and the risk of endogenous N release will gradually increase in the future.
氮（N）是湖泊富营养化的关键元素之一。本研究采用连续提取法研究了表层沉积物中四部分 N（包括游离氮（FN）、交换态氮（EN）、水解态氮（HN）和残留态氮（RN））的空间分布特征。利用修正模型描述了沉积物中氨氮（NH-N）的吸附等温线，从而预测了 N 释放的风险。探讨了环境因子与 N 浓度之间的相关性，以及不同介质之间 N 的迁移或转化和释放风险。结果表明，N 分数的空间变化特征受湖泊地形和周围人类活动的影响。沉积物中总氮（TN）含量为 933.4 ～ 3006.8 mg/kg，平均值为 1835 mg/kg。沉积物中 HN、RN、FN 和 EN 分别占 TN 的 66.85%、21.35%、6.82%和 4.92%。各形态 N 与 TN 之间以及不同形态 N 之间均呈显著正相关（p<0.01）。采用修正的 Langmuir 模型拟合表明，沉积物中 N 的最大吸附量（Q）大小顺序为：东南湖区（2905.3 mg/kg）>西南湖区（1415.4 mg/kg）≈北湖区（1424.6 mg/kg）。环境参数（pH、DO、C/N 等）影响氮的赋存形态，可能导致内源 N 持续释放高浓度的持久性和增加风险。沉积物和间隙水中的 N 污染严重，内源 N 释放的风险将在未来逐渐增加。
