Study On In-situ Remediation Of Different Cadmium-polluted Agriculture Lands

The survey data from Ministry of environmental protection,Ministry of land and resources shows that China’s heavy metal pollution of the soil has been very grim situation,and cadmium pollution is particularly serious,which has been listed as the primary pollutant.Heavy metal pollution in farmland usually has long duration of pollution,wide area and high concealment,which greatly increases the difficulty of remediation;the economic added value of polluted farmland is far less than the contaminated industrial land,which limits the application of remediation technology to farmland.Therefore,it is urgent to study the remediation technology of heavy metal contaminated farmland with low cost and simple operation.Based on the previous research results,In this paper,three kinds of technical measures,including in-situ passivation repair,combined phytoremediation of hyperaccumulators and combined phytoremediation of animals and plants,were carried out to study the remediation of cadmium polluted paddy fields and dry land respectively,in order to provide a scientific basis for the development and application of in-situ remediation technology of cadmium contaminated farmland.In the passivation repair test,24 passivation materials such as zeolite,calcium magnesium phosphate and vermicompost were selected.The phytoremediation test included different intercropping treatments of red vegetables,ryegrass,clover,alfalfa and cadmium superaccumulators.The effects of earthworms on the efficiency of combined remediation were studied in animal and plant combined remediation experiments.The main results are as follows:Study on the effect of different passivating agents on cadmium passivation in paddy field1.The effect of different passivation materials on the yield of rice is different,but in general,compared with the non passivation agent,the yield of rice only changes a little,and the fluctuation range is less than 10%.After applying the passivation agent,there is a certain change in soil acidity,and the pH value shows an upward trend,but the effect is not obvious.2.Most of the passivating agent can reduce the cadmium content of rice(brown rice)in a way,among which the effect of calcium magnesium phosphate and animal blood meal are the most obvious,the Cd content in brown rice are 0.26 mg/kg,0.31 mg/kg,compared with the control group decreased by 58.33% and 51.16%.3.With the economic cost analysis,as cadmium contaminated rice passivation agent the biological material has obvious economic advantages,the marginal cost of most biological materials are below 10 yuan,of which the animal bone meal and blood meal to the best effect.So the economic feasibility of those agents is higher,which have more application potential.Study on remediation of cadmium contaminated soil by hyperaccumulator intercropping1.Intercropping different plants,due to water and fertilizer and other natural resources competition,Solanum nigra biomass has declined significantly,but the high biomass intercropping plants can increase the total biomass of the plot.Among them,Solanum nigrum and red chard intercropping,the total biomass of the plot(1364.35g)has the largest increase in 22%,when compared to monoculture of Solanum nigrum(1118.76g).2.The intercropping plants have no significant effect on the cadmium content in the aerial parts of Solanum nigrum,but the cadmium content in the roots are increased with the enrichment ability of intercropping plants.The difference of biomass between different treatments directly determines the total amount of cadmium in the plant.Compared to other intercropping plants,for the higher biomass and Cd accumulation ability of red chard,the total area of cadmium extraction reaches the maximum value of 3508.66 g/plot,with the increase of 19.7% compared to monoculture of Solanum nigrum.3,In the different intercropping patterns,compared to monoculture of Solanum nigrum,the efficiency of cadmium extraction of red chard+Solanum nigrum is increased from 0.44% to 0.52%.However,the biological activity of Cd in soil is too low,relying solely on the introduction of intercropping plants can not significantly improve the efficiency of phytoremediation,which can not meet the needs of the actual remediation.Study on remediation of cadmium contaminated soil by earthworm and Solanum nigrum1.Earthworms can promote the growth of Solanum nigrum,the biomass of Solanum nigrum is increased with the increasing amount of earthworm inoculation.When the inoculation amount is 65 g/ pot,the biomass of Solanum nigrum reaches the maximum values of 15.12 g/ plant,with the increase of 61.71% compared with the control group.2.The enrichment ability of Solanum nigrum is the highest when the inoculation amount is 50 g / pot,and the cadmium content on the aerial part is 34.21% mg / kg,but higher inoculation of earthworms can make the cadmium content of the upper and lower parts of Solanum nigrum declined.In general,the effects of earthworms on the cadmium enrichment coefficient(BF)and transfer coefficient(TF)of Solanum nigrum are not significant.3.The cadmium enrichment of Solanum nigrum and earthworms are increased with the increase of earthworm inoculation amount.When the inoculation amount of earthworm is 65 g / pot,the total extraction rate of cadmium reaches the maximum value of 2410 μg / pot,with an increase of 241% compared to monoculture of Solanum nigrum.