天津近海富营养化及环境因子的时空变化特征

基于1995—2010年监测数据,通过Mann-Kendall趋势检验和Kriging空间插值等方法,对天津近岸海域氮磷营养盐、有机污染物和富营养状况的时空变化趋势及其成因进行了分析. 结果表明:在天津近岸海域的48个监测时段中,有81.3%的监测时段处于富营养状态,有39.6%的ρ(DIN)和16.7%的ρ(DIP)超过海洋水质四类标准,有89.6%的ρ(COD_Mn)符合海洋水质一类标准;氮和磷为主要污染物,污染物质量浓度和富营养状态的季节性差异显著. ρ(DIP)、ρ(COD_Mn)和营养状态指数的年际变化主要呈下降趋势,ρ(DIN)呈先下降后显著上升的趋势；ρ(DIN)、ρ(DIP)和ρ(COD_Mn)在空间分布上基本遵循近岸高、远岸低的规律,其中ρ(DIN)和ρ(DIP)均显著呈带状分布,并且基本为北高南低. 防治天津近岸海域水体富营养化的关键是削减丰水期和平水期入海径流的氮负荷以及北部海域入海径流的磷负荷. 

Temporal-Spatial Changes Analysis of Eutrophication and Environmental Factors in Tianjin Coastal Waters

The Mann-Kendall (M-K) test and Kriging interpolation were applied to analyze the pollution status and temporal-spatial variation trend of eutrophication and environmental factors in Tianjin coastal waters over past 16years. The seawater was in the eutrophic state in 81.3% of the monitoring period. The quality of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) were worse than the fourth category of Chinese sea water quality standard in 39.6% and 16.7% during the monitoring period, respectively. The main pollutants were inorganic nitrogen and inorganic phosphorus in this area, and the seasonal differences of the environmental factors were significant. The M-K test results indicated that the annual average concentrations of COD_Mn, DIP and the eutrophication index showed an obvious downward trend, while DIN showed a downward trend in the earlier stage and an upward trend later. The Kriging interpolation results showed that the concentrations of all pollutants have a similar trend of decreasing from the near-shore to the off-shore. Furthermore, the concentration of DIN was mainly characterized by the zonal distribution, while DIP highlights the North-South differences. To control the eutrophication in Tianjin coastal waters, efforts should be taken to reduce the nitrogen discharges from all rivers and the phosphorus discharges from the rivers in the north in summer and autumn.