Nitrogen removal effect of agricultural ecological drainage ditches in the Yangtze River Basin,China
To improve the total nitrogen(TN)removal efficiency of ecological drainage ditches(EDDs)in the Yangtze River Basin,this study collected 639 field test data from EDDs in the basin and investigated the effects of different vegetation types,ditch materials,reinforcement measures,temperature ranges,and TN influent concentration ranges on the TN removal efficiency(TNRE)of the EDDs using Mann-Whitney U test and K-W test methods.The results showed that EDDs covered with various types of selected vegetation performed better in TN mitigation than ditches with other types of vegetation,producing an average TNRE of 47.72%.Among different ditch types,EDDs with semi-lined side slopes(ditch slope material was partially concrete,and ditch bottom material was full soil)had the best effect on TNRE,with an average removal efficiency of 58.18%.Among the different reinforcement measure types,EDDs with artificial substrates and interception-type reinforcement measures added had the best TNRE,with an average reduction efficiency of 54.24%.The TN reduction effect of EDDs was greater when the temperature was>25-35℃.In low-temperature environments,the TN reduction effect could be improved by planting certain cold-tolerant plants.The TN inlet concentration of the ditch was mainly within>2-4 mg·L-1,and the TN outlet concentration of the ditch was mainly within 0-2 mg·L-1.The reduction effect in the EDDS was best when the TN inlet concentration was within>2-4 mg·L-1.Under different concentration conditions,ditches were selected for the planting of various selected vegetation,semi-lined side slopes,and reinforcement measures to improve the purification effect of TN.The TNRE was positively correlated with hydraulic retention time,ditch length,and water depth.The TN surface removal load increased with inlet concentration.The results showed that EDDs in the Yangtze River Basin could more effectively reduce TN under the following conditions:implementation of various selected vegetation and ditches with semi-lined side slopes,addition of artificial substrates and interception-type reinforcement measures,temperature and inlet concentration controlled at>25-35℃and>2-4 mg·L-1,respectively,and extended length of ditch and controlled water depth and hydraulic retention time of water bodies.
Yangtze River Basinecological drainage ditchagricultural non-point sourcenitrogenMann-Whitney U testK-W test
万方数据
维普
