Hyperaccumulator Of Copper Contaminated Soil Enrichment Plant Screening

In recent years, due to the "three wastes" discharge, copper minerals mining, the long-term heavy use of copper fungicides and sewage sludge compost in soil containing copper rose sharply in some areas, once over the soil environmental capacity, will affect the ecological system security. For the increasingly serious problem of heavy metal remediation of copper, due phytoextraction low cost, does not destroy the soil structure, the implementation should be very easy, easy to operate features well received by the environmental scientists of all ages. To screen out a series of ideal hyperaccumulators and accumulators that can effectively remedy contaminated soils by heavy metals is the main groundwork of phytoremediation engineering and the first step of its commercial application on a large scale, which is also front field of contaminated environment remediation. In view of that the amount of discovered hyperaccumulators and their hyperaccumulated the types of heavy metals are short at present, the author select Polygala chinensis L., Calendula officinalis L., Lactuca sativa L., Chrysanthemum paludosum, Chysanthemun coronarium L., Festuca arundinacea Schreb., Amaranth, Amaranthus tricolorL., Portulaca pilosa, Dianthus chinensis L., Mimosa pudica L., Trifolium repens Linn.12 species that predecessors have not studied, set a different concentration gradient of Cu to carry out pot experiment. From the growth, plant biomass, content of copper in plants, the total accumulation of copper, Bioconcentration factor, Biological transport coefficient and so on, the author explore the different plant absorption and enrichment characteristics, defined the size of the biomass plant uptake of copper,study the influence of different copper concentrations in soil to the plant with the absorption and accumulation of copper. The main findings are as follows:(1)The degree of copper tolerance to the different types of plants is of a difference. According to the difference of copper tolerance, tested plants were divided into two categories:①lant can grow in the soil with highest concentration of copper, showing a stronger tolerance to copper. Such as Lactuca sativa L.,Festuca arundinacea Schreb., Trifolium repens Linn., Calendula officinalis L.and so on;②plant can not grow in the soil with highest concentration of copper, showing a general tolerance to copper. Such as Polygala chinensis L., Chrysanthemum paludosum, Amaranth, Amaranthus tricolorL.,Portulaca pilosa, Dianthus chinensis L. and so on.(2)The effects on plant biomass caused by different copper treatments are quite different, showing the following rules:①Different concentrations of Cu treatments on plant growth shows "promote inhibition" phenomenon, such as Festuca arundinacea Schreb., Trifolium repens Linn., Amaranth., Portulaca pilosa and Dianthus chinensis L;②Copper treatment at any concentration, the biomass is much less than the control. Such as Chrysanthemum paludosum;③with the increase of the concentration of copper in soil, the aboveground and underground of plant biomass had two peaks. For example Polygala chinensis L., Calendula officinalis L., Lactuca saliva L. and Amaranthus tricolor L.;(3)In the different types of plants, absorption of copper content for per unit mass are significantly different. Under the conditions of different copper concentrations, the variation of copper content in plants is as follows:①Copper content of aboveground is larger than 400 mg kg-1. Such as Festuca arundinacea Schreb. and Trifolium repens Linn, have strongest absorption to copper, plant copper content of aboveground reached a maximum of 434.07 mg kg-1,465.89 mg kg-1.②Copper content of aboveground is larger than 100 mg kg-1. Such as Polygala chinensis L. and Amaranth copper content of aboveground reached a maximum of 138.07 mg kg-1,235.03 mg kg-1③Copper content of aboveground have poor absorption of copper. Such as Calendula officinalis L., Chrysanthemum paludosum, Lactuca sativa L., Amaranthus tricolorL., Portulaca pilosa and Dianthus chinensis L copper content of aboveground are only 73.51 mg kg-1,64.24 mg kg-1,52.45 mg kg-1,52.01 mg kg-1,21.90 mg kg-1 and 21.54 mg kg-1. But all the tested plants have not reached the copper hyperaccumulator of copper content in the aerial parts must be more than 1000 mg kg-1 of the screening criteria.(4)The plant biomass's size has certain influence to the copper absorption total quantity. The copper absorbing capacity is different according to the adult plant to the soil, may divide into the following two kinds:①The plant can absorb copper massively from the soil. By calculating the absolute amount of copper it is found that the biomass of Festuca arundinacea Schreb. is the biggest one and the absolute number of copper is the highest. The copper absorption quality achieves 2.5 mg. The aboveground and underground unit mass copper content respectively is 143.35 mg kg-1,338.77 mg kg-1 under the same density.②The plant absorb lower copper from the soil. The biomass of Calendula officinalis L. reaches 2.45g. The copper absorption quality is only 0.20 mg. The aboveground and underground unit mass copper content respectively is 31.12 mg kg-1,256.31 mg kg-1 under the same density. The biomass of Polygala chinensis L. is 2.53g. The copper absorption quality is only 0.24 mg. The aboveground and underground unit mass copper content respectively is 73.54 mg kg-1,162.78 mg kg-1 under the same density. (5)The BCF is varies by species. Specific rules are as follows:①The BCF of aboveground is greater than or close to 1 when in the low concentration. Such as Festuca arundinacea Schreb.and Trifolium repens Linn..②The BCF of aboveground is lower than 1. Such as Polygala chinensis L., Calendula officinalis L., Lactuca sativa L., Portulaca pilosa, Amaranth, Chrysanthemum paludosum, Amaranthus tricolorL. and Dianthus chinensisL..(6)Tested the biological transport capacity to copper can be summarized as the following 3 conditions:①transfer coefficient under various copper concentrations are greater than 1.Such as Amaranthus tricolorL.and Dianthus chinensis L.②transfer coefficient under various copper concentrations are less than 1,with the increase of the concentration of copper in soil to increase or decrease volatility,no regularity..Such as Festuca arundinacea Schreb., Calendula officinalis L and Lactuca sativa L.③transfer coefficient under various copper concentrations are greater than or less than 1.Such as Polygala chinensis L.,Chrysanthemum paludosum, Amaranth, Portulaca pilosa and Trifolium repens Linn..(7)After analyzing the experimental measure index and find that 12 species of the experiment plants do not meet the definition of the current international standard of copper hyperaccumulator. However, the tested plants like Festuca arundinacea Schreb.and Trifolium repens Linn, have large biomass, higher removal rate and stronger tolerance to copper. The BCF of aboveground plant is greater than or close to 1. They can be used as afforestation plants in the future.