铁山港湾近8年溶解氧状况与变化趋势

Status and Trend of Dissolved Oxygen in Tieshangang Bay in Recent 8 Years

溶解氧(Dissolved Oxygen,DO)是判断水质优劣的重要指标之一,为弄清2013-2020年广西铁山港湾溶解氧的变化特点,对该港湾近8年自动监测结果的年均值、日均值、季节均值等进行统计分析。结果表明:铁山港内湾、外湾溶解氧浓度年均值均呈波动下降趋势,内湾溶解氧降幅较外湾明显,内湾低于第二类水质标准的天数由8 d增加至93 d。2013-2020年夏季内湾溶解氧季节均值均未达到第一类海水水质标准,2020年秋季内湾溶解氧季节均值均为8年来最低值。内湾溶解氧受季节影响较大,呈现冬季>春季>秋季>夏季的特点,溶解氧偏低的时段为夏、秋季,主要受水温、地表径流营养盐的输入和人工海水养殖的影响。

Dissolved oxygen(DO)is one of the important indicators for judging the quality of water.In order to clarify the characteristics of changes in dissolved oxygen in Tieshangang Bay of Guangxi from 2013 to 2020,this study conducted a statistical analysis on the annual average,daily average,and seasonal average of the automatic monitoring results of the bay in the past 8 years.The analysis results concluded that the annual average value of dissolved oxygen concentration in the inner and outer bays of Tieshangang Bay showed a fluctuating downward trend.The dissolved oxygen in the inner bay had a more significant decline than that in the outer bay,and the number of days in the inner bay was below the second-class water quality standard had increased from 8 d to 93 d.In the summer of 2013-2020,the average seasonal value of dissolved oxygen in the inner bay did not meet the first-class seawater quality standard,and the average seasonal value of dissolved oxygen in the inner bay during the autumn of 2020 was the lowest in eight years.The dissolved oxygen in the inner bay was greatly affected by the seasons,showing the characteristics of winter>spring>autumn>summer.The period of low dissolved oxygen was summer and autumn,which was mainly affected by water temperature,nutrient input of surface runoff and artificial mariculture.