黄河水体氨氮超标原因探讨

根据黄河水体氮污染物的种类、浓度和来源以及黄河特有的泥沙和水化学条件，结合实验结果，从生物和化学的角度讨论黄河氨氮超标的可能原因.结果表明，水体悬浮颗粒物对硝化过程有明显的促进作用，氨氮的超标不是因为泥沙对硝化作用的影响所导致.氮污染物的不断输入是黄河水体氨氮超标的根本原因，高浓度氨氮和有机氮对硝化过程有抑制作用，当NH⁺₄-N初始浓度分别为10.1，18.4，28.2 mg/L时，初始的硝化效率分别为17.4％，13.0％，2.5％,当有机氮初始浓度分别为5.5，8.6 mg/L时，其降解所产生的氨氮最高浓度分别为0.47，1.69 mg/L，在水体中滞留的时间分别为2 d和6 d.水体中耗氧有机物和有毒物质对硝化细菌活性的影响间接导致了氨氮在水体中的滞留.黄河水体高pH值导致非离子氨浓度较高，进一步对硝化细菌产生抑制作用.水量较小、颗粒物含量较低和微生物的活性降低是枯水期氨氮污染加重的原因.

Reasons of High Concentration Ammonium in Yellow River, China

Ammonium nitrogen contamination is one of the major problems of the Yellow River in China.The speciation,concentration and sources of nitrogen compounds as well as the water environment conditions of the Yellow River had been analyzed to study the reasons for the fact that the ammonium nitrogen concentration was above the water quality standard.In addition,laboratory experiments had been carried out to investigate the effects of suspended sediment(SS) on nitrification rate.The results indicated that the presence of SS could accelerate the nitrification process,therefore,the effects of SS on nitrification rate was not the reason for the high level of ammonium nitrogen in the river.The excessive and continuous input of nitrogen contaminants to the river was the fundamental reason for the high concentration of ammonium nitrogen.Organic and ammonium nitrogen with high concentration inhibitted the nitrification processes.When the initial NH~ _4-N concentrations were 10.1,18.4 and 28.2(mg/L),nitrification efficiencies were 17.4%,13.0% and 2.5%,respectively.When the initial organic nitrogen concentrations were 5.5 and 8.6(mg/L),the maximum concentrations of ammonium nitrogen produced by the oxidation of organic nitrogen would reach 0.47 and 1.69(mg/L) and they would last for 2 days and 6 days,respectively.The oxygen-consuming organics and toxic substance existing in the river water could inhibit the activity of nitrifying bacteria,and thus lead to the accumulation of ammonium nitrogen.In addition,the high pH value of river water resulted in the high concentration of nonionic ammonium nitrogen which would reduce the activity of nitrifying bacteria and decrease the nitrification rates.Besides,low river runoff,low SS content and low activity of nitrifying bacteria resulted in the high level of ammonium nitrogen of the river in the low water season.