Spatio-temporal variational analysis and prediction of water quality in the BeiTang Estuary and its coastal sea areas
北塘口近岸海域水环境质量时空变化分析及预测

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 water 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 period 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 contrast, 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.