| As we all know, the soil is the major agricultural production areas, but in recent. years due to use pesticides in agricultural production, widespread use of fertilizers and the use of irrigation water, resulting in heavy metal pollution become very serious, then this soil pollution because of their own hidden, cumulative, hysteresis, long-term, irreversible, directly or indirectly,and through the food chain affecting human health, control of soil heavy metal pollution has become a challenging and difficult task. that the environment scientists faced. Currently,we control of heavy metal pollution of soil have biology, chemistry, physics and more complete repair techniques, and according to the economic view, people are often more attracted to low-cost bioremediation technique, due to the microbials have no ability to heavy metals contaminants in soil.Phytoremediation can make up for the deficiencies and favored by environmental scientists, screening of hyperaccumulators to remediation of heavy metal contaminated soils as a basis preparing the preliminary work, but also is a hot research aspect. It is sceened that can grow well in contaminated soil and can have strong absorption zinc in soil, accumulation and transport capacity of plants, on the basis of previous studies, select the head shape comb, kale, zinnia, basil, cypress, maidenhair, camellia impatiens, amaranth, bitter gourd, carrot 10 species, set different concentrations of zinc make pot experiment. By measuring the different parts of the plant biomass, zinc content, and further use a related formula to caculate the enrichment factor in different parts of plants, and the transport coefficients of various concentrations of plants. Analysis the experimental plant zinc absorption, accumulation and transfer capability in different conditions, the results are as follows:(1) Zinc concentration in soil influenced plant biomass due to plant species vary. Tested 10 kinds of major changes in plant biomass are following four rules:①Convex type of plant:with the increase of the concentration of zinc in soil, the underground and aboveground part of plant biomass increased, but reached a certain critical concentration, biomass reached the maximum, more than the critical value, the plant biomass will decreased with increasing zinc concentration, such as head-like crest and cypress;②incremental type of plant:the plant biomass showed an increasing trend with increasing zinc concentrations, indicating that these plants have strong tolerance to zinc,the higher the concentration of zinc in the soil, the greater role it played on plant growth promotion, such as basil;③increasing volatility model:the biomass of these plants as the concentration of zinc in soil increases, the overall trend was increasing type, but very volatile, such as zinnia, bitter gourd, carrot;④aboveground plant biomass changes were convex and underground biomass of plants increased volatility:the kale, maidenhair, Camellia Impatiens, amaranth represented.(2) Tested 10 species of plants on the absorption of zinc varies by species. Head-shaped crest, basil, amaranth on zinc absorption capacity is very strong in 10 species, zinc content of the aerial part of the zinc concentration in the soil reached the maximum when the largest 2148.2,1749.47,2129.47 mg·kg-1; kale, zinnia, impatiens Camellia zinc absorption capacity of the second, and shoot the maximum zinc content to 1000 mg·kg-1 above; and carrots on the ground have poor absorption capacity only 596.47 mg·kg-1.10 species on zinc absorption capacity were shown the following situations:①underground zinc content higher than the ground, such as Camellia Impatiens, head-shaped crest, kale, carrots, etc.;②above and under ground are not have high zinc content. Such as carrots;③As the zinc concentration increased, first aboveground part of the zinc content higeter than the underground,then the undergroude zinc content is greater than above ground, such as zinnia, basil;④plant aboveground and underground zinc content change is not certain regularity. Such as Kochia, maidenhair, amaranth, bitter gourd.(3) Selected plants almost every plant on the absorption of zinc there was an enrichment of the highest (peak) concentration, zinc concentration in soils with a certain value, the absorption capacity of plants to zinc strongest the best restoration.When the concentration of zinc in the soil below or above this value, the absorption capacity will be reduced, its effect will have an impact on restoration. Strong absorptive capacity for zinc plants, such as head-shaped crest, kale, zinnia, basil plants,the aerial part of the zinc content of zinc in experimental design concentration 1048mg·kg-1 attain to the maximum; Maidenhair aboveground part of the zinc content of the maximum concentration of zinc in soil 262mg·kg-1; bitter gourd aboveground part of the maximum zinc content of zinc in the soil concentration of 131mg·kg-1.(4) The enrichment ability of plants to zinc mainly as follows law:①plant enrichment factor greater than 1, with the zinc concentration, enrichment capability enhanced in a certain range of low concentration, high concentration inhibited. Representative plants kale, head-shaped crest, zinnia, basil, Camellia Impatiens, indicating a low concentration of zinc is beneficial for enrichment capabilities, the high concentration of zinc in inhibition of its effect on the zinc concentration, enrichment capability weakened.②aboveground and underground parts of the enrichment factor greater than 1 or less than 1, with the concentration.enrichment capacity first increased and then decreased, on behalf of cypress plants, maidenhair, bitter gourd.③above ground and underground parts of the enrichment factor greater than 1, regressive changes, such as geese to red, indicating an increase in zinc concentration in the soil will inhibit the absorption of zinc.④aboveground and underground parts of the enrichment factor within a certain range of low concentrations of greater than 1, high concentrations of less than 1.(5) Tested the transfer ability of plants to zinc can be summarized as the following 3 conditions:①transfer coefficient under various zinc concentrations less than 1, and with the increasing concentration of zinc in soil, transfer factor increased volatility, head-shaped comb and kale plants represented.②transfer coefficient under various zinc concentrations greater than or less than 1, with the increasing concentration of zinc in soil showed a decreasing trend and, on behalf of zinnia plants, maidenhair.③transfer coefficient of greater than or less than 1, with the increase of the concentration of zinc in soil to increase or decrease volatility, no regularity, such as basil, cypress, camellia Impatiens, amaranth, bitter gourd, carrot.(6) zinc hyperaccumulator screening. Zinc hyperaccumulator above the ground, zinc content more than 10000 mg·kg-1, shoot enrichment factor greater than 1, transfer coefficient of greater than 1 selection criteria, for the test from the selected plant does not meet the requirements. But the tested plants like the head cocks comb, basil, amaranth treatment in various concentrations of zinc are growing well and strong ability to absorb zinc, zinc concentration greater ability to screen out these three kinds of enrichment plants for future generations training through a variety of biological means to provide some hyperaccumulators reference. |
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