草原地区河流型天然湿地对河流水体污染物去除特性

Removal characteristics of pollutants by riverine natural wetland in prairie region

为阐明草原地区河流型天然湿地对主要污染物总磷(TP)、总氮(TN)和化学需氧量(COD)的去除效果,以海拉尔河湿地为研究对象,通过2010—2015年湿地入水口(陶海断面)和出水口(嵯刚断面)水体TP、TN浓度和COD变化,分析不同月份湿地对水体TP、TN和COD的去除效果,并对污染物去除机理进行探讨。结果表明:陶海断面水体TP、TN浓度和COD变异系数分别为0. 51、0. 73和0. 39,嵯刚断面水体TP、TN浓度和COD变异系数下降至0. 36、0. 43和0. 38,海拉尔河湿地对水体TP、TN和COD的去除率分别为26. 67%、20. 90%和8. 74%,目前湿地入水TP、TN和COD负荷尚未超过其饱和净化能力;受融雪水和夏雨带来的地表径流的影响,海拉尔河湿地在5月和8—9月对水体TP、TN的去除率较低,在地表径流作用弱的1—3月、10—12月去除率较高;海拉尔河湿地对TP的去除在融雪期主要为生物同化及土壤吸附作用,在冰冻期主要为土壤吸附和沉淀作用,对TN的去除在融雪期主要为硝化与反硝化作用及生物同化作用,在冰冻期主要为底泥吸附作用,生物同化作用次之,对COD的去除主要是微生物降解和土壤吸附作用等。

In order to clarify the removal effects of total phosphorus( TP), total nitrogen( TN) and chemical oxygen demand( COD) in river-type natural wetlands in the grassland, the Hailaer River wetland was studied. The changes of TP, TN and COD in the inlet( Taohai section) and the outlet( Cuogang section) during 2010-2015 were analyzed. The removal effects of TP, TN and COD in wetlands in different months were analyzed, and the mechanism of pollutant removal was discussed. The results showed that the coefficients of variation of TP, TN and COD in the Taohai section were 0. 51, 0. 73 and 0. 39, respectively, and in the Cuogang section were reduced to0. 36, 0. 43 and 0. 38. The removal rates of TP, TN and COD in Hailaer River wetland were 26. 67%, 20. 90%and 8. 74%, respectively. At present, the load of TP, TN and COD in wetland inflow had not exceeded their purification capacity. During the snowmelt period( May) and summer rain period( August to September), the wetland had lower removal of TP and TN. During the weak surface runoff period( January to March, October to December), the TP, TN and COD were highly removed. The removal of TP by wetland was mainly by bio-assimilation and soil adsorption during ice-thaw period, and by soil adsorption and precipitation during freezing period. The removal of TN by wetland was mainly by nitrification and denitrification and biological assimilation in ice-melting period, followed by sediment adsorption and biological assimilation in freezing period. The removal of COD in wetlands was mainly due to microbial degradation and soil adsorption.