海河天津段与河口海域水体氮素分布特征及其与溶解氧的关系

Nitrogen Distribution in the Water of the Haihe River Mainstream and Estuary Seawater and Its Relationship with Water Dissolved Oxygen Levels

从海河天津段至河口海域选取20个采样点,研究了水体中氨氮、硝酸盐氮和亚硝酸盐氮的分布特征及其与溶解氧的关系。结果表明:海河天津段及河口海域水体氮素以氨氮含量最高,均超出地面水环境质量标准(GB3838-2002)的Ⅴ类水质标准,与海河两岸排放的工业废水及城镇生活污水有关;海河内陆水体的氮素含量远高于河口海域,且亚硝酸盐氮的含量表现得尤为突出,可能与水体溶解氧水平和微生物环境有着很大关系;海域的氮素含量因受水体均质化的影响,与溶解氧含量的关系不明显,而河水的氮素组成受溶解氧含量的影响波动很大;除6,7号样点溶解氧含量较高以外,河水的溶解氧含量均偏低,位于河口处的10号样点的溶解氧含量最低,该站点3种形态的氮含量都相对较高,且亚硝酸盐氮的含量最高,可能是由于该样点处于相对厌氧状态,部分硝酸盐被反硝化细菌等微生物还原为亚硝酸盐所致。

Twenty sites were selected for water sampling from the Haihe River mainstream in Tianjin city and its estuary seawater to study the nitrogen distribution and contents of ammonia, nitrate and nitrite. It was found that the contents of NH_3-N at all the sampling sites are relatively high, and exceed Grade Ⅴ surface water quality of the national standard (GB3838-2002), which is possibly associated with the discharges of both industrial and domestic effluents along the river system. The total nitrogen level of the Haihe River mainstream is considerably high compared with that in estuary seawater, especially for the nitrite, which may result from the differences of the water dissolved oxygen (DO) level and microbial populations. The nitrogen forms level of the seawater depends little on the DO content because of the homogeneity of the water properties, while that in the mainstream differs greatly with the DO levels. In addition, the DO level of the mainstream is relatively low except for that at sites 6 and 7. The DO content is the lowest at site 10 where is the estuary of the river and the water quality is seriously degraded. At this site, the levels of the three nitrogen forms are relatively high, and the nitrite content is the highest, which may be due to the anaerobic environment where nitrite is easily produced from nitrate by reductive microorganisms.