Relieving Effects Of Trifolium Repens On Complex Heavy Metals Pollution In Copper Tailing Yard

As one of the ideal approaches for improving the injured ecosystem and reducing the heavy metals pollution in soil, phytoremediation is inexpensive and convenient, and can prevent of secondary pollution.In order to recover the ecosystem in the copper tailing yard in Penzhou of Sichuan, firstly we investigated its natural vegetation characters and plant community succession state. The results showed that there were 91 species of high plants in the copper tailing yard, which belonged to 38 families and 79 genera. The main families were Gramineae and Compositae. The vegetation formed 6 types of relatively stable community. The succession stage of the copper tilling yard was between hassock and dwarf-shrub. We found that Trifolium repens is preponderant specie which has the capacity of biological nitrogen fixation and improvement of the soil environment. It also has attractive appearance and strong adaptation to trampling stress. So we had chosen it as kinds of potential plant for the vegetation recover.We analyzed the total and the available contents of the heavy metal in the copper tailings with atomic spectrophotometer. The result showed that there were several heavy metals in the copper tailing except copper. Their total contents exceeded the national standard and the pollution of the copper tailings was complex.We tested the effects of extraction liquid of copper tailing on the seeds germination of T. repens. It showed that the extraction liquid delayed the germination of T. repens, and made the radical became shorter and decreased the weight of seedling. However, the finally germination rate was as same as the control under distilled water. So we considered that T. repens could withstand the pollution of complex heavy metals in a way, although it would also be injured by the copper tailings. The soil constitutes in the copper tailings should be improved to weaken its injury on T. repens.T. repens were planted in pots contained the copper tailings and non-polluted soil in different mixing proportion (100% copper tailings, 75% copper tailings +25% non-polluted soil, 50% copper tailings +50% non-polluted soil, 25% copper tailings +75% non-polluted soil, 100% non-polluted soil). Three months later, we analyzed the physiological function (viz. biomass, root activity, contents of photosynthetic pigment, contents of MDA, contents of free proline, contents of solubility sugar, contents of solubility protein, activity of SOD, activity of POD) of their leaves. The result showed that copper tailings affected the growth and development of T. repens. Addition of 25% non-polluted soil (v/v) into copper tailings could weaken the injury on T. repens.The present study showed that T. repens could resist the pollution of complex heavy metals in copper tailings. We can recover the vegetation by introducing T. repens into the copper tailing yard mixed with some non-polluted soil.