象山港海域N、P和COD_(Mn)的变化趋势及其与富营养化的关系

Variation trends of N,P and COD_(Mn) in Xiangshan Harbor and the relationship between them with eutrophication

根据近20多年来(1984～2005)象山港海域海洋环境监测的基础资料,建立象山港海域CODMn、DIN和PO4-P的时间序列,用平均差值法、最小二乘法和自回归滑动平均法3种趋势分析方法,统计检验了该海域CODMn、DIN和的PO4-P的长期变化趋势。并用相关分析和影响因子分析方法,分析了CODMn、DIN和的PO4-P年际波动与富营养化的关系。结果表明:近20多年来象山港海域DIN和PO4-P的年平均浓度长期以来均呈增加的趋势,而CODMn呈降低的趋势;象山港海域富营养状态指数E长期以来一直呈降低的趋势,这与CODMn相同,与DIN和PO4-P的变化趋势相反。CODMn的变化与富营养状态指数E呈显著的正相关,DIN和PO4-P的变化与富营养化状态指数E呈弱的正相关;CODMn,DIN和PO4-P对富营养装态指数E的影响因子分别为6.9822,2.2449和3.3836,CODMn对富营养状态指数E年际变化的贡献程度远大于DIN和PO4-P。当CODMn含量变化幅度较大的时候,海水营养状态指数E的变化不能真实反映海域营养盐的含量变化特征,富营养状态指数E在表征海水富营养化程度时存在一定的局限性,这也揭示了中国第Ⅰ代海水富营养化评价体系存在的问题。

On the base of ocean environmental data observed in the Xiangshan Harbor,time sequence of annual mean CODMn,DIN,PO4-P was established in last 20 years（1984～2005）.The long-term variation trends of them were tested by three statistical methods：the average difference method,the least square method and self-regression slope AR（1） process.The relationships between CODMn,DIN,PO4-P and the sea water eutrophication were analyzed by the correlation analysis method and effect factor analysis method.The results showed that DIN and PO4-P had increased trend in a long-term and CODMn had decreased trend in a long-term.The eutrophication state indexes（E） in Xiangshan Harbor was straight in decreased trend over a long period of time as same as CODMn,but DIN and PO4-P had opposite tendency.The correlation and effect factor analysis showed that a significant positive correlation existed between CODMn and eutrophication state indexes（E）,while the correlation between eutrophication state indexes（E） and DIN or PO4-P was the insignificant positive correlation.The effect factor of CODMn,DIN and PO4-P on Eutrophication state indexes（E） was 6.9822,2.2449 and 3.3836,respectively.The effect of CODMn on Eutrophication state indexes（E） was evidently larger than DIN and PO4-P.Which was noteworthiness,the study results of the variation trend also showed that the change of eutrophication state indexes（E） could not truly reflect the changes of nutrient content when the amplitude of fluctuation of CODMn was more relatively large.The eutrophication state indexes（E） had definite limitation as a taken of seawater eutrophication degree.It showed that there was a little matter in the eutrophication pricing systemⅠin China.