北塘口近岸海域水环境质量时空变化分析及预测

Spatio-temporal variational analysis and prediction of water quality in the BeiTang Estuary and its coastal sea areas

通过分析2005年—2010年北塘口及其邻近海域水环境现场调查资料,同时结合历史数据进行对比,结果表明:(1)北塘口河口水体中COD和BOD5超标严重,整体污染态势以2008年为界呈现先降低后升高的趋势;邻近海域水体中无机氮为最主要污染物,其中硝酸盐是无机氮中最主要组成部分,但丰水期时亚硝酸盐氮和枯水期时铵盐氮所占比例逐年升高,说明区域水体氧化还原环境的潜在变化;N/P比值远高于正常的Redfield 16比值表明,区域水体已处于潜在严重P限制状态,同时,区域严重富营养化状态也极易诱导区域赤潮爆发;(2)丰水期陆源无机氮大量输入,使区域水体大部分时间超该区域功能区划要求的Ⅳ类海水水质标准,但底质沉积物环境相对比较稳定,各监测项目全部符合一类海洋沉积物质量标准要求;(3)丰水期和枯水期时,活性磷酸盐含量1983年—1998年分别增加了16.6倍和17.2倍,1998年—2010年由于监控措施的加强,极大地降低了P排放,丰水期和枯水期时活性磷酸盐含量最大增幅分别降到了5.84倍和2.33倍,无机氮含量增幅也呈现明显减小趋势,1983年—1998年丰水期和枯水期分别增加了8.37倍和13.7倍,而1998年—2010年丰水期和枯水期最大增幅也仅为3.52倍和3.28倍;整体看来水质和底质环境有缓和趋势,但潜在威胁仍然严重。

Based on the analysis of the large quantity of monitoring materials on BeiTang estuary and its coastal sea areas from 2005 to 2010, and the comparison with historical data, it was shown that （1） COD and BOD5 in the wa- ter of the BeiTang estuary significantly exceeded the fifth sort of environmental quality standards for surface water. And the overall pollution decreased before 2008 and increased after 2008. IN was the major pollutant in the costal sea areas and the proportion of the nitrite nitrogen in high water period and the ammonia nitrogen in low water pe- riod was yearly increased, suggesting the potential changes of oxidation-reduction context. The fact that N/P ratios outclassed the Redfield 16 indicated the potentially serious P limits and the further badly eutrophication status, which could easily initiate the outburst of Red Tide. （2） A great deal of land-sourced IN pollutants were poured into the coastal sea areas and this make the water quality be in the inferior fourth sort of national water quality. In con- trast, the sedimentary environment was relatively stationary, corresponding to the enormously changing of water environment. （3） From 1983 to 1998, the concentration of phosphate and IN was increased by 16.6 and 8.37 times in high water period and 17.2 and 13.7 times in low water period, respectively. Compared with the early rapid growth, the relatively lower growth rate of phosphate and IN was only 5.84 and 3.52 times in high water period and 2.33 and 3.28 times in low water period separately under strict control from 1998 to 2010. Although the water and sediment quality appeared a relaxed trend in the larger pollutants, there still existed serious threat.