人工湿地构筑根孔作用下土壤物质分布状况

嘉兴市石臼漾湿地应用人工构筑根孔技术,以玉米秸秆和油菜秸秆按比例混合埋植于土壤亚表层,作为湿地的基质/填料。在湿地运行一年半后,按照正交设计表,以埋植秸秆的种类(S)、填埋的土壤层次(L)、距离秸秆外环的远近(D)和秸秆周围土壤的表观颜色(C)作为实验因素,对秸秆周围养分物质浓度、土壤酶活性以及铁含量进行采样分析。实验结果显示:玉米秸秆和油菜秸秆腐烂较充分,分别形成较发达的粗根孔和细根孔;根孔周围土壤呈中度还原状态;粗根孔具有较强的优先流效应,其周围土壤具有较高的养分物质含量和较低的Fe2+/Fe3+比。粗根孔周围土壤具有较高的磷酸酶活性,而细根孔周围具有较高的β-葡糖苷酶活性和脲酶活性。综合比较,人工湿地构建初期,径级较大秸秆腐烂后形成的粗根孔发挥着更高的水分传导效率和更强的物质截留效应。

Soil substances distribution in the rhizosphere of an artificial wetland affected by constructed root channels

Root channel purification technology utilizes mixed straws with various diameters as the substrate media of constructed wetlands.This technology can promote the rapid formation of soil macropores at the initial operation stage of constructed wetlands.The novel technology had been successfully applied in Shijiuyang constructed wetland for 1.5 years.In order to evaluate the rhizospheric soil substances distribution and to compare the intercept efficiency of different constructed root channels,a research was conducted to study enzymatic activity,nutritional elements,iron element in the root channel purifying zone.The design of experiment was based on orthogonal tests,using plant straws of different species(S),buried soil layers(L),distance to the outer ring of straws(D) and soil apparent color around straws(C) as four experimental factors.It was found that the straws of maize and rape had begun to decompose well forming thick and thin root channels respectively,and the ambient soil around root channels was in a condition of moderate reduction.The thick constructed root channels could stimulate a better preferential hydraulic conductivity,compared to the thin ones.The soil around the thick root channels contained higher contents of nutritional elements and lower ratios of Fe2+/Fe3+.Enzyme activities were compared between soils around both straw types in the root channel zone.Results showed that phosphatase activity was higher in soil around maize straws,while urease activity and β-glucosidase activity were higher in soil around rape straws.To summarize,the thick root channels could conduct more water through the subsurface zones of wetlands and trap more elements at the initial operation stage of constructed wetlands.