藻类暴发对国家地表水考核断面水质的影响

横江大桥国考断面在2019年8月水质监测结果不符合GB 3838—2002《地表水环境质量标准》中的Ⅴ类要求,调查发现仅水体pH不符合标准要求。受日照和气温的影响一天中的pH波动较大,出现pH符合标准要求和不符合标准要求两种情形。进一步研究发现是水体中藻类暴发引起pH升高。夏季白天较强的日照和较高的气温会使藻类的光合作用增强,pH和溶解氧浓度升高,pH不符合标准要求,溶解氧出现过饱和;而夜晚缺少日照且气温降低使光合作用减弱,pH和溶解氧浓度降低,pH又符合标准要求,溶解氧恢复正常。夏季控制水体质量应特别需要考虑治理藻类。

The water quality monitoring results of the national examination section of Hengjiang Bridge in August 2019 did not meet the Class V requirements in GB 3838-2002 Environmental Quality Standards for Surface Water,the investigation found that only the pH value of water body did not meet the standard requirements.The pH value fluctuated greatly in a day due to the influence of sunshine and temperature,and there were two situations:meeting the standard requirements and not meeting the standard requirements.Further research found that the algae blooms in the water body caused the increase of pH value.The stronger sunlight and higher temperature during the daytime in summer would enhance the photosynthesis of algae,the pH value and dissolved oxygen concentration increased,and the pH value did not meet the standard requirements,the dissolved oxygen was supersaturated.Lack of sunshine and lower temperature at night weakened the photosynthesis,the pH value and dissolved oxygen concentration decreased,and the pH value met the standard requirements,the dissolved oxygen returned to normal.Algae control shall be specially considered for water quality improvement in summer.