人为扰动背景下城市边缘溪流底质硝化-反硝化潜力分析

Nitrification and Denitrification Potential of Benthic Sediments in a Suburban Stream under Intense Human Disturbance Scenarios

2016年5月至2017年1月,在合肥城区东北部边缘某一溪流的自然状态段(情形1)、点源排污段(情形2)和水土流失段(情形3)设置6个采样点位,逐月采集水样和表层底质样,解析不同情形下溪流底质硝化-反硝化潜力及其变化特征,并进行差异性和影响因素分析.结果表明:(1)溪流底质硝化活性均值为0.381%,并以情形2底质硝化活性最高,情形1的夏季硝化活性相对最强、冬季最弱,情形2、3硝化活性高低排序为:春季>夏季>秋季>冬季;(2)溪流底质硝化速率均值为0.364mg·(kg·d)^(-1),其中以情形2底质硝化速率最高,情形2、3的各采样点春季硝化速率显著最高,其它季节相差不大,情形1的各季节变化不很明显;(3)溪流底质反硝化活性为37.25%,反硝化速率为57.68 mg·(kg·d)^(-1),其中情形2底质反硝化活性和反硝化速率都高于相同季节的其他情形,情形1、2的反硝化活性和反硝化速率高低排序均为:夏季>春季>秋季>冬季,情形3的反硝化活性和反硝化速率排序均为:春季>夏季>秋季>冬季;(4)差异性分析表明,情形1、2在硝化速率方面存在极显著差异性,情形1、3在反硝化活性、反硝化速率方面存在极显著差异性,而情形2、3在硝化速率、反硝化活性和反硝化速率方面均呈现极显著差异性;(5)偏最小二乘回归分析表明,3种情形在硝化活性和硝化速率方面重要贡献因素差异较大.

Water and benthic sediment samples were collected monthly from six sites over a 2-km reach in a first-order stream located in the northeastern rural-urban fringe of Hefei City,from May 2016 to January 2017.These sites were scattered in three stream reach types as natural pattern sections（Scenario 1）,point source pollution sections（Scenario 2）,and severe soil erosion sections（Scenario3）.The potential rates of nitrification and denitrification in the sediments were measured and variable characteristics were evaluated quarterly.Moreover,a difference analysis of each of the three scenarios and an influencing factor analysis for nitrification and denitrification potentials were subsequently conducted.Our results show that：（1） the mean value of the nitration ratios for total sediment samples is 0.381%,of which the maximum nitration ratio emerged in Scenario 2.As for Scenario 1,the nitration ratio in summer is the larger than in winter.The nitration ratios for Scenarios 2 and 3 rank from largest to smallest as spring summer autumn winter.（2） The mean value of the nitrification rate of the total sediment samples is 0.364 mg·（kg·d）^-1,of which the maximum nitrification rate is associated with in Scenario 2.The nitrification rate is highest in winter,while similar for all other seasons in Scenarios 2 and 3.There is not much difference all year round for Scenario 1.（3） Average values for the denitrification ratio and denitrification rate for all sediment samples are 37.25% and 57.68 mg·（kg·d）^-1,respectively.Both of these are higher for Scenario 2 than the other two scenarios for the same season.The ranking for denitrification for Scenarios 1 and 2 is summer spring autumn winter,and spring summer autumn winter in Scenario 3.（4） According to the difference analysis,significant differences not only exist between the nitrification rates between Scenarios 1 and 2 but also for the denitrification ratios and denitrification rates between Scenarios 1 and 3.In addition,there is an obvious difference in the nitration ratio between Scenarios 2 and 3.（5） Partial least-squares regressive analysis indicates that there is significant difference between the important influencing factors related to the nitration ratio and nitrification rate for each of the three scenarios.