春秋季三门湾表层海水氮磷营养盐等要素含量的分布特征

Distribution characters of nitrogen,phosphorus and other factors in surface water of Sanmen Bay in spring and autumn

以2011年5月中旬（春季）和2011年10月中旬（秋季）对浙江三门湾海域开展的海域水质现场调查为基础,分析讨论了三门湾表层海水无机氮、活性磷酸盐、溶解氧含量及化学需氧量的分布特征.结果表明：春秋两季无机氮含量范围为0.395 ～1.073、0.501～0.803 mg/dm3,平均值为0.687、0.645 mg/dm3,无机氮含量超标率达100％;活性磷酸盐含量范围在0.022～0.036、0.040 ～0.053 mg/dm3,平均值为0.030、0.046 mg/dm3,春季超标率为56％,秋季超标率达100％;无机氮与活性磷酸盐含量的高值区出现在陆源径流入海区与大型养殖区附近,总体呈现自西向东递减的趋势;春季氮、磷含量低于秋季.除4号站春季化学需氧量超标外,该海域溶解氧含量与化学需氧量均符合二类海水水质标准.根据富营养化状态指数值和CN/Cp比值的总体评价结果显示,三门湾海域的富营养化现象严重,属于磷限制潜在性富营养区.

Based on the data obtained in surveys of May and October 2011 in Sanmen Bay,Zhejiang Province,the spatial-temporal variables of DIN,PO4-P,DO and COD contents in surface water layers were analyzed.The result showed that in spring and autumn the DIN content ranged from 0.395 to 1.073 mg/dm3 and 0.501 to 0.803 mg/dm3,in averages of 0.687 and 0.645 mg/dm3,respectively.The contents of DIN in all samples exceeded the Grade Ⅱsea water quality standard.The PO4-P content ranged from 0.022 to 0.036 mg/dm3 and 0.040 to 0.053mg/dm3,in averages of 0.030 and 0.046 mg/dm3,respectively.The contents of PO4-P in 56％ samples exceeded the Grade Ⅱ sea water quality standard during spring while it was 100％ exceeded in autumn.The DIN and PO4-P contents near the river estuary and the mariculture zone in the west of the bay were higher than in other areas and descended toward the east bay.The average indexes in autumn were higher than those in spring.The water quality of DO,with exception of station 4,in spring and COD all met the Grade l sea water quality standard.The modified method of nutrient status index and CN/Cp value shows that the eutrophication status in Sanmen Bay was severe and the bay could be classified as a phosphorus-limited potential eutrophication area.