三峡水库典型支流水体氮磷分布特征及污染评价

Nitrogen and Phosphorus Distribution Characteristic and PollutionEvaluation in Typical Tributaries of the Three Gorges Reservoir

研究三峡库区典型支流澎溪河与香溪河水体营养盐分布特征及污染状况,于2017年5月和11月分别对两条河的水体进行采样研究,分析了水体氮磷的含量与时空变化趋势并评价了两条支流沉积物的污染状况.结果为:澎溪河水中的TP含量范围为0. 01～0. 18 mg/L,均值为0. 07mg/L,TN含量范围为0. 45～2. 29 mg/L,均值为1. 22 mg/L;香溪河水中TP含量范围0. 04～0. 31mg/L,均值为0. 15 mg/L,高于澎溪河,可能由于香溪河磷矿资源丰富,TN含量范围0. 20～1. 46mg/L,均值为0. 73 mg/L.澎溪河TN浓度以及香溪河TP浓度丰水期浓度相比枯水期偏高,且香溪河TN/TP比值表明丰水期比枯水期营养水平更高,澎溪河NH4+-N/NO3--N比值表明丰水期营养水平更高.沉积物间隙水中,除了香溪河丰水期TP浓度低于上覆水,澎溪河、香溪河间隙水中其余指标浓度均值均高于上覆水,沉积物表现为营养盐的"源",其中氨氮释放的趋势最大.对澎溪河、香溪河沉积物进行污染评价发现,澎溪河、香溪河存在较明显的有机氮污染,而两条支流的有机指数则表明沉积物在不同水期有差异,丰水期时沉积物受到有机污染,而枯水期时沉积物则无有机污染,处于较清洁～尚清洁的两种类型之间.研究结果表明,两条典型支流澎溪河和香溪河上覆水中丰水期比枯水期营养水平更高,沉积物表现为营养盐的内源,且部分处于清洁状况,部分受到了有机污染,受污染状况呈现季节性波动.

In order to study the distribution characteristics and contamination status of nutrients in typical tributaries of the Three Gorges reservoir,the Pengxi River and Xiangxi River were observed in the reservoir area in May and November 2017. The space-time distribution characteristics of nitrogen and phosphorus in the Pengxi River and Xiangxi River were analyzed,and the contamination status of the sediments was evaluated by organic nitrogen,organic index and nutrients enrichment evaluation method. The concentrations of TP,TN in the overlying water of Pengxi River were 0. 01 ~ 0. 18 mg/L,0. 45 ~ 2. 29 mg/L with average values of 0. 07 mg/L,1. 22 mg/L,respectively. Meanwhile,the TP content in the Xiangxi River ranged from 0. 04 to 0. 31 mg/L,with a mean value of 0. 15 mg/L,which was higher than the Pengxi River,and TN content ranged from 0. 20 to 1. 46 mg/L,with an average of 0. 73 mg/L. In the flooding season,the TN concentration in the overlying water of Pengxi River and the TP concentration in the overlying water of Xiangxi River were higher than that in the dry season. The TN/TP ratio in the overlying water of Xiangxi River indicated that the nutrient level in the flooding season was higher than in the dry season,and the NH+4-N/NO-3-N ratio in the overlying water of Pengxi River represented the same situation. As for the interstitial water,except that the TP concentration in the flooding season of Xiangxi River was lower than that of overlying water,the average concentrations of other indicators in the interstitial water of Pengxi River and Xiangxi River were higher than that of overlying water. The sediment was the"source"of nutrients,and ammonia nitrogen was most likely to release. The pollution evaluation of the sediments revealed that there was obvious organic nitrogen pollution in the Pengxi River and the Xiangxi River,while the organic indices of the two tributaries indicated that the sediments were different in different periods. The sediments were polluted in the flooding season,while they were free of organic pollution and were relatively clean in the dry season. The results show that the nutrient level of overlying water in the flooding season was higher than in the dry season. The sediments were the internal source of nutrients,and some were in a clean state,others were organic pollution,and the pollution was seasonally fluctuating.