Elsholtzia Splendens Remediation Of Copper Contaminated Soil Assisted By Trichoderma

Heavy-metal pollution in soils is very common at home and abroad. Heavy metals pollution in soil is more hidden, hysteretic, cumulative and irreversible than in the air and water pollution, not easily found directly by senses. In view of heavy metal pollution in soil of severity, early detection and timely treatment and remediation is essential.With traditional physical and chemical soil remediation technology, phytoremediation technology, paid great attention by scholars at home and abroad, become one of methods of effective management of polluted soil, for whose low cost, environmentally friendly features. However, hyperaccumulator plant is low-biomass, slow-growth, great-impact of soil environment, and not easy to absorb fixed-state heavy metals. So finding a way to improve the efficiency of phytoremediation, but also to improve the ecological environment of soil, will be of great theoretical significance and wide application prospect. Microbial enhanced phytoremediation approach is an environment-friendly and cost-effective new way.In this paper, Cu-resistant fungi were selected in varying degrees from the Cu-polluted soils, and in accordance with broad-spectrum, security and wide-adaptability features of Trichoderma, Cu-resistant Trichoderma were selected, which was investigated their biological characteristics and properties of copper-resistant. The study of Cu-resistant Trichoderma to enhance Elsholtzia splendens remediation of copper polluted soil was carried out by pot experiments. The aim is to explore a more efficient and more generally approach to microorganisms strengthens phytoremediation of heavy-metal pollution in soils. The main findings are as follows:1,The type and quantity of culturable fungi was investigated in varying degrees of Cu-polluted soils, and three strains (FS5-H, FS10-C and FS10-G) of Cu-resistance Trichoderma spp. were isolated. Identified by morphological characters and 18S rDNA, FS5-H and FS10-G are assigned to Trichoderma harzianum, and FS10-C is assigned to Trichoderma reesei.2,Because of Trichoderma can not be quickly and efficiently selected from heavy metal polluted soil by an ordinary fungi medium, based on high-resistance and high-activity-cellulose of Trichoderma, in our study the medium was improved. Medium B (that is, sodium carboxymethyl cellulose 15 g/L, peptone 5 g/L, asparagine 1.0 g/L, MgSO₄·7H₂O 0.5 g/L, KH₂PO₄ 1.0 g/L, 1 % of Bangladesh Red 3.3 ml/L, 1 % streptomycin, 3 ml/L, trace elements 1 ml/L) and modified Martin's medium (that is, add 60 mg/L streptomycin, Martin's medium concentration) are highly efficient to screen Trichoderma in the Cu-polluted soils. Particularly, Medium B is more effective screening of Trichoderma than modified Martin's medium.3,Resistant copper of the three screening Trichoderma strains was investigated. All of the strains have high Cu-resistant ability and high accumulation rate at low concentration of Cu (≤300 mg/L). Especially, FS10-C strain is able to grow in the 600 mg/L of the high concentration of copper. And in the 100 and 200 mg/L of the low concentration of copper, the rates of its accumulation are 50.6 % and 30.3 %, respectively. Further study of biological characteristics of the FS10-C strain, indicates that its conidiospore germination and hypha growth need of some nutritional condition, and no other strict requirements. The conditions of its conidiospore germination are temperature range of 20-36℃, humidity range of above 80 %, and pH 2-8; And the conditions of its hypha growth are temperature range of 20-36℃, pH 5-7, and small light effect.4,Seed germination test of Elsholtzia splendens results showed that spores suspension of different concentrations of FS10-C do not inhibit seed germination of Elsholtzia splendens. The germination rate was above 70 % at 5 d, and of which 100 % spores suspension to deal with the seeds germination rate of Elsholtzia splendens was significantly higher than the control group, up to 78.3 %. Pot test results showed that added FS10-C's spore suspension to the biomass and uptake-copper of plants had a significant role in the promotion. The dry weight of the plate of Elsholtzia splendens to deal with adding FS10-C more than 72.4 % increased in one not adding FS10-C at concentration of Cu (≤400 mg/kg) in soils. And the Cu-concentration of aboveground and underground parts of the plant processed FS10-C agents increased significantly of the low Cu concentration in soils, but at high concentration of Cu (400 mg/kg) no significant effect. The biomass of Elsholtzia splendens adding FS10-C agents was more than 50 % higher than the control in combined pollution soil, especially the mass of its aboveground part increased significantly, but the underground part did not change. It was no significant effect with the repair process to add springtails for increasing plate biomass and Cu-uptake. And the uptake of plants for copper and zinc had same trend.