近20年广西钦州湾有机污染状况变化特征及生态影响

利用1990至2010年长期监测的结果,采用有机污染指数法对钦州湾近20年有机污染程度进行评价,分析其变化趋势并探讨其对海湾环境的潜在生态影响。结果表明近20a钦州湾有机污染指数变化较大,内湾变化范围为-0.55-5.49,外湾的变化范围为-0.44-3.96。20世纪90年代内湾和外湾有机污染物程度均显下降趋势,1999-2003年显上升趋势,2003年以后外湾显平稳波动状态而内湾为显著增加的趋势,近几年内湾有机污染加重到严重污染的程度。径流输入、浮游植物消耗以及水体交换等因子的综合作用是该海湾有机污染变化的主要因素,也是导致内湾和外湾变化差异的主要原因。海湾有机污染的变化导致富营养化的变化,有机污染和富营养化程度的变化并没有与浮游植物生物量的变化显著相关,但内湾近年来急剧加重的有机污染增加了赤潮等生态灾害的风险。内湾有机污染加重也会对水产增养殖等产生影响,需要加大关注和防治。

Variation of organic pollution in the last twenty years in the Qinzhou bay and its potential ecological impacts

Based on the data obtained from 1990 to 2010, concentrations of dissolved oxygen, chemical oxygen demand, inorganic nitrogen, and reactive phosphate in Qinzhou Bay in the past 20 years (1990-2010) were recorded and analyzed to demonstrate the long-term variation of organic pollution level in the bay. Organic pollution index (OPI) was employed to study the organic pollution status, and the potential ecological risk originated from such pollution in the study bay was also been discussed. The result showed that OPI was valuable during last twenty years in the Qinzhou bay. OPI ranged from -0.55 to 5.49 in the inner bay, and ranged from -0.44 to 3.96 in the outer bay, showing a wide variation pattern. Based on the results, the outer bay can be considered as clean or moderately polluted, and the inner bay was moderately polluted as well. Generally, OPI in the outer bay decreased from 1990 to 1999, but increased from 1999 to 2003, and then remained undulatory afterwards. Variation of OPI in the inner bay from 1990 to 2003 was similar to that in the outer bay. The OPI in the inner bay however kept increasing in recent years (2003-2010), and organic pollution status in recent years was serious, which indicated a degradation pattern of the inner bay. Inorganic nitrogen was the most important factor that contributed the variation of OPI, and the effects of reactive phosphate was getting more and more significant in recent years from 2003 to 2010. River input (including the input of the Maolingjiang River and the Qinjiang River), phytoplankton consumption, water exchange as well as the interaction of these factors were the main reasons for the variation of organic pollution in the Qinzhou bay. The difference organic pollution status in recent years between the inner and the outer bay may be due to the change of such reasons. The variations of organic pollution bay resulted in the variation of eutrophication in the study. And the increasing OPI in recent years explained the increasing phytoplankton biomass from 2003 to 2010 in the bay. Although no significant positive relationship was found between organic pollution and phytoplankton biomass, the increasing organic pollution in the inner bay may trigger some ecological impact, such as algae bloom. The increasing reactive phosphate may finally breach the phosphate limitation in the bay and cause a series of deleterious effects to the aquaculture industry. Organic pollution in the inner bay might also influenced the aquatic product in the study bay.