Badr El-Sayed A
Environmental Sciences Department, Faculty of Science, Damietta University, PO Box 34517, New Damietta City, Egypt.
Environment and Natural Resources Department, College of Agriculture and Food Science, King Faisal University, Al-Hassa, Saudi Arabia.
Environ Monit Assess. 2016 Oct;188(10):580. doi: 10.1007/s10661-016-5588-5. Epub 2016 Sep 22.
Increases in human activity have resulted in enhanced anthropogenic inputs of nitrogen (N) and carbon (C) into the Nile River. The Damietta Branch of the Nile is subject to inputs from industrial, agricultural, and domestic wastewater. This study investigated the distribution and seasonality of dissolved organic nitrogen (DON), dissolved organic carbon (DOC), and nutrients in the Nile Damietta Branch. Water samples were collected from 24 sites between May 2009 and February 2010. Dissolved organic nitrogen concentrations averaged 251 ± 115 μg/l, with a range of 90.2-671 μg/l, and contributed 40.8 ± 17.7 % to the total dissolved nitrogen (TDN) pool. Relative to autumn and winter, DON was a larger fraction of the TDN pool during spring and summer indicating the influence of bacterioplankton on the nitrogen cycle. Concentrations of DOC ranged from 2.23 to 11.3 mg/l with an average of 5.15 ± 2.36 mg/l, reflecting a high organic matter load from anthropogenic sources within the study area, and were highest during autumn. Higher values of biochemical oxygen demand (BOD), chemical oxygen demand (COD), DON, nitrate, and phosphate occurred downstream of the Damietta Branch and were probably due to anthropogenic inputs to the Nile from the Damietta district. A bacterial incubation experiment indicated that 52.1-95.0 % of DON was utilized by bacteria within 21 days. The decrease in DON concentration was accompanied by an increase in nitrate concentration of 54.8-87.3 %, presumably through DON mineralization. Based on these results, we recommend that water quality assessments consider DON and DOC, as their omission may result in an underestimation of the total organic matter load and impact.
人类活动的增加导致尼罗河的氮（N）和碳（C）人为输入量增加。尼罗河的达米埃塔支流受到工业、农业和生活污水的影响。本研究调查了尼罗河达米埃塔支流中溶解有机氮（DON）、溶解有机碳（DOC）和营养物质的分布及季节性变化。2009年5月至2010年2月期间，从24个地点采集了水样。溶解有机氮浓度平均为251±115μg/l，范围为90.2 - 671μg/l，占总溶解氮（TDN）库的40.8±17.7%。相对于秋季和冬季，春季和夏季DON在TDN库中所占比例更大，这表明浮游细菌对氮循环有影响。DOC浓度范围为2.23至11.3mg/l，平均为5.15±2.36mg/l，反映了研究区域内来自人为源的高有机物负荷，秋季浓度最高。生化需氧量（BOD）、化学需氧量（COD）、DON、硝酸盐和磷酸盐的较高值出现在达米埃塔支流下游，可能是由于达米埃塔地区对尼罗河的人为输入。一项细菌培养实验表明，52.1 - 95.0%的DON在21天内被细菌利用。DON浓度的降低伴随着硝酸盐浓度54.8 - 87.3%的增加，推测是通过DON矿化作用。基于这些结果，我们建议水质评估应考虑DON和DOC，因为忽略它们可能导致对总有机物负荷和影响的低估。
