2013年春季莱州湾海域理化环境及水质状况分析

依据2013年6月对莱州湾海域的调查资料，分析了该海域盐度(S)、pH、溶解氧(DO)、化学耗氧量(COD)、溶解无机氮(DIN)和活性磷酸盐(PO4-P)等理化因子的分布特征，并采用潜在性富营养化评价模式和有机污染指数分别对该海域的营养水平和有机污染状况进行了评价。结果显示，2013年春季莱州湾所有站位溶解氧、化学耗氧量均符合Ⅰ类海水水质标准；DIN污染严重，31%站位的DIN含量超Ⅳ类海水水质标准；PO4-P含量较低，所有站位PO4-P含量均符合Ⅰ类海水水质标准。由评价结果来看，2013年春季莱州湾海域N/P比值总体处于高值，P相对缺乏，营养水平处于磷限制潜在性富营养(ⅥP)水平，有机污染程度属于Ⅱ级，表明该调查海域开始受到有机污染，但有机污染程度轻于2007年夏季。

Evaluation of Physicochemical Environment and Water Quality in the Laizhou Bay in Spring of 2013

In recent years, the marine environment and ecosystem in the Laizhou Bay have obviously deteriorated, which caused serious damage to the ecological environment and biological community. In order to understand the environmental qualities of the Laizhou Bay and the adjacent sea areas, we analyzed the distribution of salinity, pH, dissolved oxygen (DO), chemical oxygen demand (COD), disolved inorganic nitrogen (DIN) and PO4-P based on field data obtained from the Laizhou Bay in June 2013. The nutrition level and organic pollution in this area were also evaluated with potential eutrophication assessment standards and grading of organic pollution respectively. The results showed that DO and COD concentrations at all surveyed stations met the first class seawater quality standard. DIN pollution was serious mainly caused by the terrestrial input. At approximate 31% of investigated stations the DIN concentration exceeded the limit of the fourth class seawater quality standard. The level of PO4-P was lower and satisfied the first class seawater quality standard at all investigated stations. Our results suggested that the N/P ratio was higher than the Redfield value 16, and that phosphate was the limiting factor in the growth of phytoplankton. The nutritional pattern in the Laizhou Bay had evolved from nitrogen limiting to phosphorus limiting. The higher N/P ratio may alter the phytoplankton population, which will consequently affect the whole ecosystem. The nutrition status in the Laizhou Bay was phosphorus limiting potential eutrophication, and the organic pollution remained at the second level in spring 2013. These indicated organic pollution in this sea area; however, the pollution was alleviated compared to the summer 2007.