三沙湾海水增养殖区表层溶解氧变化特征及有机污染评价

Variation Characteristics of Surface Dissolved Oxygen and Assessment of Organic Pollution in Mariculture Zone of Sansha Bay

【目的】研究三沙湾海水增养殖区溶解氧的动态变化及有机污染状况。【方法】利用2014年三沙湾水质的监测结果,分析调查区表层溶解氧变化特征,以及与水温、无机氮、活性磷酸盐之间的相关性,采用单因子指数法和有机污染指数法分别对调查区溶解氧和有机污染进行评价。【结果与结论】调查区内共布设9个水质监测站位,于2014年1、5、8、9、10月分别采集调查区的表层水样。调查区溶解氧质量浓度在4.44~8.60 mg/L之间,平均值为6.29 mg/L,除8月有2站次和9月有5站次的测值处于三类海水水质标准外,其余均处于一、二类海水水质标准水平;溶解氧季节变化明显呈冬季>春季>秋季>夏季的变化规律,平面分布总体呈西北部高,东南部低的变化特征;结合历史资料分析长期变化趋势,溶解氧总体呈现下降趋势,尤其在2000年下降幅度较为明显,这跟三沙湾沿岸带的经济发展对环境影响有关;溶解氧与水温之间呈现极为显著(r=-0.946 4)的负相关关系,与无机氮和硝酸盐氮之间均呈现极为显著(r=0.827 5,r=0.821 3)的正相关关系,与活性磷酸盐之间呈现显著(r=0.541 3)的正相关关系,说明水温是影响溶解氧变化的首要因子,无机氮和硝酸盐氮以及活性磷酸盐也是影响溶解氧变化的重要因子;从单因子指数来看,在整个调查期间溶解氧污染指数大于1.0的达到15.6%,说明该站点水质已受该因子污染;从有机污染指数来看,调查区水质状况处在开始受到污染状态。

【Objective】The dynamic changes of dissolved oxygen and organic pollution in the mariculture zone of Sansha Bay were studied.【Method】Based on the monitoring data of the water quality in 2014,the paper analyzed the variation characteristics of surface dissolved oxygen content in the mariculture zone of Sansha Bay and the correlation with water temperature,inorganic nitrogen and active phosphate.The dissolved oxygen and organic pollution were evaluated by single factor index method and organic pollution index method respectively.【Result and Conclusion】The dissolved oxygen content in the investigated area was between 4.44 and 8.60mg/L,with an average value of 6.29 mg/L.The measured values of the two stations in August and the five stations in September accorded with category III of Sea Water Quality Standard while those of the other stations accorded with category I and II.There was obvious seasonal variation of DO,and its variation trend was as follows:winter>spring>autumn>summer.The horizontal distribution was generally high in the northwest and low in the southeast;Based on the analysis of historical data,the change of dissolved oxygen over the years showed a decreasing trend,especially in 2000,which may be related to the impact of economic development of Sansha Bay coastal zone on the environment;Dissolved oxygen had extremely significant negative correlation with water temperature(r=-0.946 4),highly significant positive correlation with inorganic nitrogen(r=0.827)and nitrate nitrogen(r=0.821),and significant positive correlation with active phosphate(r=0.541).It indicated that water temperature is the primary factor affecting the change of dissolved oxygen,and inorganic nitrogen,nitrate nitrogen and active phosphate are also important factors.Using single factor index method,the dissolved oxygen pollution index was more than 1.0 and reached 15.6%during the whole investigation period which suggested that the water quality of the site was polluted by this factor.The calculating results of the organic pollution index showed that the water quality in the survey area was beginning to be polluted.