农田汇水河道水生植物原位净化工程处理效果分析

为了研究水生植物原位净化工程处理效果,于2017年5—11月,在江苏省泗洪县四河乡的农田汇水河道,利用水葫芦和绿狐尾藻构建组合生态浮床,沿着水流方向设置4个水质采样点,每月监测水体基本理化指标,主要包括水温(T)、酸碱度(pH)、溶解氧(DO)、总氮(TN)、总磷(TP)、化学需氧量(COD_(Cr))、悬浮物(SS),分析河段水质沿程变化;在试验开始时、每次采收时监测单位面积植物生物量,干物质含量与氮磷含量,计算植物氮磷富集量。结果显示:植物种养后,沿程各采样点数据对比,水体pH值逐渐趋于中性;各采样时间数据对比,水体DO浓度呈升高趋势。在植物旺盛生长期(7—10月),组合生态浮床对河段水体TN、TP、COD和SS的沿程总消减率分别为50.41%～78.00%、44.62%～73.33%、46.15%～57.82%和33.33%～52.38%,其中最高值出现在8月。按照有效试验周期180 d(5—10月)计算,水葫芦的氮、磷去除量分别约为0.76 g·m~(-2)·d~(-1)和0.09 g·m~(-2)·d~(-1);绿狐尾藻的氮、磷去除量分别约为1.17 g·m~(-2)·d~(-1)和0.08 g·m~(-2)·d~(-1)。除了植物自身的吸收作用,根系微生物降解作用在污染物净化过程中也发挥了重要作用。在农田汇水河道原位净化工程中,水葫芦与绿狐尾藻组合生态浮床大幅消减水体氮磷浓度,有效降解有机物及拦截颗粒物,对于缓解下游水域富营养化问题具有积极的意义。

Removal of contaminants in a farmland catchment river by aquatic macrophyte on floating beds

This study was designed to determine the efficiency of contaminants removal from a farmland catchment river via aquatic macrophytes growing on floating beds. A field experiment utilizing floating beds with Eichhornia crassipes(Mart.)Solms and Myriophyllum elatinoides Gaudich. was conducted in Sihong County, Jiangsu Province, China, from May to November in 2017. After plant cultivation, water samples were collected at 4 sites along the river. The physical and chemical indexes of the river, including temperature, pH, dissolved oxygen(DO), total nitrogen(TN), total phosphorous(TP), chemical oxygen demand(COD_Cr), and suspended solids(SS)were monitored every month during the experiment, to analyze changes in water quality along the river. Fresh weight, dry matter content, and N and P contents of the plants were monitored on May 11, June 11, August 7, September 13, and November 19, to calculate the amount of absorption of N and P in plant tissues. Based on the comparison of data among sampling points, pH tended to be neutral along the river. Based on the comparison of data of intermediate and initial period, DO concentration showed an increasing trend. During the vigorous growth phase of the aquatic plants(from July to October), the total removal rates of TN, TP, COD_Cr and SS in river water were 50.41%~78.00%, 44.62%~73.33%, 46.15%~57.82% and 33.33%~52.38% along the river, respectively, and the highest removal rates occurred in August. Based on calculations during the effective experimental cycle of 180 d(from May to October), the amounts of N and P removed by E. crassipes were 0.76 g·m^-2·d^-1 and 0.09 g·m^-2·d^-1, respectively; the amounts of N and P removed by M. elatinoides were 1.17 g·m^-2·d^-1 and 0.08 g·m^-2·d^-1, respectively. In addition to the assimilation by marcophytes, degradation by root microorganisms also played an important role in the purification of contaminants. These results indicate that ecological floating beds with E. crassipes and M. elatinoides can effectively decrease the concentrations of N and P, degrade organic contaminants and retain particulate matter, which have positive impacts on the alleviation of eutrophication in downstream waters.