Indicating Effect Of Nematodes On Environment Quality Of Farmland Soil Irrigated By Constructed Wetland Treated Water

This research, based upon constructed wetland system for sewage treatment, explores the efficiency of constructed wetland system applying to purifying of irrigation water and farmland soil and indicative effect of soil nematode to the variance of heavy metals in soil. After one year of irrigation to original farmland by using purified water pumped from Yellow River originally, and setting farmland that irrigated by non-treated water from Yellow River as control group, we select different time points (September,2008; March,2009; May,2009; July,2009; September,2009) to detect the community structure of soil nematode, and calculate eco-index, and detect content of Cd, Cu, Pb and Zn in irrigation water and soil in farmlands. The results are showed as following:The content of the four metallic elements in wetland-treated water is lower than the content in control group in different time points (P<0.01), and the content in farmlands is also lower than the content in control group (P<0.01). However, the level of the content of heavy metals fluctuates with the change of content in Yellow River.In total,24 families and 41 genera of nematode in soil have been identified. Except of March 2009, the nematodes number in soil irrigated by treated water is lower than control group (P<0.01), and the average number in treated group is 122.6/100g soil, while the number in non-treated soil is 165.8/100g soil. Moreover, except of September 2008, the proportion of bacteria-feeding nematodes in farmland soil irrigated by treated water is lower than control group (P<0.01).Soil nematodes are classified in different c-p value groups. The proportion of c-pl-2 is lower than control group except September 2008 (P<0.01). On the contrary, the proportion of c-p3-5 is higher than control group.Ecological indexes of soil nematode MI,∑MI,H'and PPI become lower at the month of high heavy metals (September 2009), and vice versa. MI and∑MI of treated group is higher than control group except September 2008 (P<0.05-0.01).The result indicates that constructed wetland can efficiently decrease the content of heavy metals in water and irrigated farmland (P<0.05-0.01), and the quality of soil can be improved at the same time. Improvement of quality of soil can also be represented by community, ecological diversity and ecological indexes of nematode.