| Because of the low fertility and high heavy metal content in the lead/zine tailings, it is difficult to plant and restore the ecosystem. It can not only increase the nutrient, also affect the form of heavy metals in lead-zinc tailings to use green manure. Visible, green manure plays an important role on improving ecological environment of lead-zinc tailings.In order to study the effects of green manure on lead/zine tailings from Laiyuan, Hebei, China, with a pot experiment, two kinds of green manure ryegrass and alfalfa were selected. Alfalfa green manure was applied with the amount of 1%, 2%, 4%(weight/weight), and the amount of ryegrass was based on the equal quantity of carbon to each treatment of alfalfa. At the same time, a control treatment was set up(without applying manure). The nutrient availability, pH value and heavy metal phytoavailability were investigated. The results indicate that both the two kinds of green manure significantly inrecased the available nitrogen and phosphorus concentrations in tailings. The results also found that green manure had influence on Ph of tailings. The pH values in treatments with addition of green manure were higher than those in control in the prophase, but lower than control after that until the 60 th day. And the exent of variatoan on pH values decreased with the amount growing of green manure addition during the 60 days. Moreover, it was found that the application of green manure decreased the phytoavailability of Pb, Zn, Cd and Cu in lead/zine tailings. The inhibitory effects on heavy metal concentration in 1 mol/L NH4NO3 and 0.05 mol/L EDTA-2Na extractions were stronger in treatments of applying ryegrass 1% and 4%(weight/weight), as well as applying alfalfa 4%.In order to study the effects of ryegrass green manure on the growth of ryegrass and the accumulation of heavy metal in ryegrass, ryegrass green manure was applied with the amount of 1%, 2%, 4%(weight/weight), and a control treatment was set up(without applying manure). Then ryegrass were harvested and determined on 60 th day. The study found that ryegrass green manure addition can not only increase the biomass of ryegrass and also reduce the accumulation of Pb, Zn, Cu, as well as heavy metal transfer coefficient and the enrichment factor. The biomass of ryegrass is bigger in treatments of applying ryegrass 1% and 4%(weight/weight). When the ryegrass addition is 4%, the transfer coefficient of Pb, Zn, Cu is lower than the treatment of applying ryegrass 1%, but the enrichment factor of Pb, Zn, Cu is higher than the treatment of applying ryegrass 1%.In summary, consider the cost of manure, and the most important facter of limiting plant growth is the high levels of heavy metals in lead and zinc tailings. This study suggested that the addition of 1% ryegrass manure and the addition of 4% alfalfa manure had a better effect on ecological restoration of lead/zine tailings. |
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