Migration And Distribution Of Cd In Soil-Mulberry-Silkworm System

At present, China is facing quite serious heavy metal pollution. Among all provinces, Hunan Province is famous for rich mine resource, called "hometown of non-ferrous metals". While in the operating and smelting of non-ferrous metal, due to waste water, waster solid and atmosphic deposition, the serious environmental problem had happened, like soil heavy metals pollution, especially Cd pollution. The high concentration of Cd in soil caused the growth of plants, and the product of crop. Moreover, through food chain, Cd is easily adsorpted by human body and causes health problem, like itai-itai disease. Therefore, it is necessary to remediate heavy metal-contaminated soil. Among all remediation technologies, phytoremediation technology has the unique advantage of being favored by the people. Among phytoremediation technologies, economic plant like Mulberry can be planted in heavy metals contaminated soil for making money. In order to study the distribution of Cd in Mulberry, the greenhouse experiment and field experiments were employed. The contents of Cd in soil Cd- Mulberry-silkworm system were analyzed, which provided a scientific basis for the use of Sericulture for remediation Cd contaminated soil. The main results are as follows:(1)It was found that the height and bio mass of Mulberry firstly increased and then decreased with the increasing of Cd concentrations in the soil.The mulberry photosynthesis were caused with increasing Cd concentrations. There were direct correlation between Cd content in different parts of mulberry (root, stem and leaf) and Cd contents in soil, Moreover, with the increase of Cd concentration in soil, Cd concentrations in different part of mulberry also increased. Accumulation of Cd in Nongsang-11 and Yuesang-14 with the Cd concentration in the soil increased significantly increased firstly and then decreased, Cd accumulation in two cultivars plant mulberry highest can reach 161.90ug and 178.75ug.(2)To tesearch the effect chelating agent on Cd absorption in mulberry through pot experiment, the addition of high concentrations of EDTA and DTPA reduced the dry weight by 92.2%,26.0%,94.0% and 90.0% 88.35% 29.66%87.61% 85.79% in mulberry root, stem, branch, leaf. chelating agent to increase the mulberry resin membrane peroxidation degree and caused some damage to it. The high concentration of EDTA can enhance the accumulation of cadmium in branches and leaves of mulberry.The concertration of Cd in root accounted for the largest proportion in mulberry, leaves at least.1 mmol·kg-1 EDTA application in improving mulberry Cd accumulation ability and can ensure the biomass does not reduce or reduce at least, in order to improve the heavy metal accumulation.(3)The content of Cd in above ground (stem, branch and leaf) of mulberry increased with the increase of planting density. The high density planting method is beneficial to improve the efficiency of the remediation of Cd contaminated soil. In the whole mulberry plant, the Cd contents of mulberry roots accounted for about 40% of the total, of stem and branch accounted for about 44%, and of leaf accounted for about 16%. The increase of soil Cd pollution degree promoted the ability of mulberry root to transport Cd, The translocationfactors of root-stem, root-branch and root-leaf of mulberry in Dongkou is 0.37-0.46,0.38-0.51 and 0.37-0.49, Lingxiang is 0.50-0.83, 0.42-0.61,0.54-0.64, respectively.(4)Through biological experiments, to reasearch transference and distribution of Cd in the system of sericulture, found that the first day of the pollution mulberry leaf feeding silkworm, Bombyx mori for the accumulation of Cd is slow, eating the fourth Cecropia in Cd content increased significantly, from ripe silkworm period does not change; silkworm intake of Cd most of the day with Silkworm Feces excretion, the content of Cd in the silkworm excrement with silkworm constantly eating and increased significantly, the highest value for 94.62ug·kg-1, the period of mature silkworm silkworm excrement in the Cd content decreased; cooked silkworm cocoon, silkworm Cd most residues in silkworm pupa.Utilization of mulberry to repair severe heavy metal pollution of soil, the mulberry mulberry leaf can be used for feeding silkworm, the growth of silkworm can not be affected, silkworm, silkworm, silkworm and cocoon can be for production, further to obtain economic benefits.