Planting Demonstration Of Energy Plants On Typical Marginal Lands And Their Ecological Effection

Lots of heavy metal pollution venues resulted from ore mining activities not only occupy lands but also cause secondary pollution of the surrounding environment. Revegetation of heavy metal pollution venues is a common practice to stabilize mine tailings, prevent secondary pollution and improve environmental amenity. Among them, non-consumption energy plants growed on the heavy metal contaminated marginal lands will become a new trend of biofuel production.In this study, a demonstration research was explored that after chemical stabilization, selected energy plants could be growed on the typical heavy metal pollution marginal lands, including a copper mine tailings reservoir in Tongling, Anhui province, P.R. China and a farmland in surrounding copper zinc smelters Fuyang, Zhejiang province, P.R. China. The amendments applied in the marginal lands included cattle manure, lime, attapulgite, bentonite, zeolite and phosphate rock. Miscanthus floridulu, Miscanthus sacchariflorus, Sorghum bicolor, Saccharum officinarum and so on, which were planted on demonstration plot areas, are important raw materials for bioethanol production. Miscanthus are called fuel-crops in developed countries.Field investigation and laboratory analysis were first carried out. By analyzing samples and barley root elongation test, it was worked out the main limitation factors of plant growth in demonstration areas. Based on research results, the production demonstration of energy plants was carried out. The biomass and contents of heavy metals in energy plants, and contents of available heavy metals in soil were analyzed. The research results were as follows:1. The effect of soil amendments, including lime, attapulgite, bentonite, zeolite and phosphate rock, were evaluated through the barley root elongation toxic response experiment. The results indicated that pH of selected from experimental sites soil was significantly increased by using Ca(OH)2. At the same time, metal solubility of tested soil was reduced by addition of Ca(OH)2. As the amount of Ca(OH)2 was above 0.9 %, most available heavy metals were below the normal detection levels. However, with the Ca(OH)2 amount increased, the pH of tested soil continued to rise, and the growth rate of barley root length first increased and then declined. On the basis of lime addition, there were no obvious effect by addition of attapulgite, bentonite, zeolite and phosphate rock on tested soil, but phosphate rock could be used as a long-term phosphate. Experimental results showed that Ca (OH) 21% W /W and phosphate rock 0.1% W / W was choosed as the best amendments in field trials.2. The marginal agricultural demonstration plot polluted by heavy metal in Fuyang, Zhejiang province, after the addition of Ca (OH)2 and phosphate rock, the contents of available Cu and Zn in soil were decreased significantly. However, available Cu, Zn in soil were recovered from the analysis result showed of the heavy metals cumulative probability distribution in soil of demonstration plot, which indicated the polt after planting the energy plants still need the addition of amendments. It was supposed that the amendments added could control the effect of available Cu and Zn in the soil in the next year of planting energy plants . The biomass of energy plants per unit area followed the order sweet sorghum> sugarcane> vetiver. The tolerance to Zn of cultivated energy plants showed sugarcane had higher tolerance than sorghum. It was showed that the percentage contents of total sugar and reducing sugar in the juice under four treatments were not significantly different by analyzing the juice quality. The juice yield per unit area of sweet sorghum was more twice than the sugarcane. The contents of Zn in sugarcane and sweet sorghum juice exceeded the national food hygiene and safety standards (≤5mg / l) by 96.8%, so it could not be drank as the beverage. There were some differences among the heavy metal contents and accumulation capacity in sugarcane, sweet sorghum and vetiver. Among them, the amount of Zn and Cd were taken away by the energy plants followed the order sweet sorghum> sugarcane> vetiver, while the amount of Cu and Pb were taken away followed the order sugar cane> vetiver> sweet sorghum.3. The demonstration plot of marginal copper tailings in Tongling, after the addition of soil amendments in field experiment, the contents of available heavy metals in surface tailings decreased significantly. The pH of the acidic tailings plot was increased by adding hydrated lime. But heavy metal availability in some plots was increased by addition of phosphate rock in acidic region. After energy plants grew for one season in the demonstration plot, the contents of available heavy metals in surface tailings were still higher. The result indicated it still need addition of amendments in the next year, which could reduce the available heavy metals poisoning effect of energy plant growth. The survival rate and growth vigor of four energy plants showed Miscanthus sacchariflorus was superior to other tested plants (Survival rate of Miscanthus sacchariflorus was 99.3%), followed by Phragmites australis and Miscanthus floridulus, and Arundo donax was the worst. For the above ground biomass of energy plants, C area (cow dung) was higher than D area (cow dung and rock phosphate) in no acid region, and B (cow dung, hydrated lime and rock phosphate) was higher than A area (dung and hydrated lime) in acidic region. The absorption and accumulation capacity of heavy metal Zn, Cu, Pb and Cd in aerial parts of four energy plants showed the order Miscanthus sacchariflorus > Phragmites australis > Miscanthus floridulus > Arundo donax.4. A survey and analysis on the diversity of the newly settled plants in demonstration experimental areas of tailings in Tongling were conducted by sampling methods. The results showed after addition of amendments and introduction of four energy crops, 64 vascular plants naturally settled at the site, belonging to 25 families and 59 genera. Most settled plants were annual or biennial herbs, accounting for 57.8% of all settled plants, followed by perennial herbs, accounting for 37.5% of all settled plants. Species richness index, Simpson diversity index and Shannon-Wiener diversity index in the four treatments all followed the same order: D (phosphate rock) > C (Control) > B (lime and phosphate rock) > A(lime), while the Evenness index were the opposite. The pH and contents of available heavy metals were likely to be the limiting factors for plant settlement.