Heavy metals in soils

Remediation techniques for heavy metal-contaminated soils: Principles and applicability

https://repository.hanyang.ac.kr/bitstream/20.500.11754/110830/1/Heavy%20metals%20in%20food%20crops%20Health%20risks%2c%20fate%2c%20mechanisms%2c%20and%20management.pdf

Heavy metals in food crops: Health risks, fate, mechanisms, and management

Cadmium toxicity in plants: Impacts and remediation strategies.

Phytoremediation of cadmium (Cd) and uranium (U) contaminated soils by Brassica juncea L. enhanced with exogenous application of plant growth regulators

Comparison of three types of oil crop rotation systems for effective use and remediation of heavy metal contaminated agricultural soil

The aim of this study was to estimate the influence of regenerated tobacco on the extraction of Cd from two acidic soils as well as to address the problem of how to deal with contaminated leaves following phytoextraction. Results showed that a coppicing tobacco led to a decline in Cd concentration in regenerated leaves and stalks when plants were grown in pots, but increased concentrations in regenerated lower and middle leaves when plants were grown under field conditions. The highest recorded bioconcentration factors in Chaling and Guanxi soil were 37.53 and 19.21 in lower leaves in the field, respectively. Total Cd extraction efficiency in practice (9.43% for Chaling soil and 6.24% for Guanxi soil) under field conditions confirmed our theoretical calculations (10.0% for Chaling soil and 6.73% for Guanxi soil). Use of a 0.5% hydrochloric acid(HCl) solution was sufficient to reduce Cd (98.4%) in tobacco leaves to permissible levels as required by the Hygienic Standard for Feeds in China (≤0.5 mg kg−1). Regenerated tobacco has the potential to allow cultivation of Cd contaminated farmland to produce animal feed, assist in lowering total Cd content of soil, and allow income generation for farmers.

Phytoextraction of cadmium-contaminated soil and potential of regenerated tobacco biomass for recovery of cadmium

Heavy metal pollution, in particular with cadmium (Cd), threatens both the environment and human health. The phytoremediation of contaminated soil is one recently developed eco-friendly technique that can be applied to mitigate this issue. Repairing Cd-contaminated paddy soil during the fallow winter period can ensure future rice production while reducing heavy metal pollution. Seven winter crops were planted in this study to investigate the accumulation of this metal in mid-level Cd and low-level lead (Pb) and zinc (Zn)-contaminated paddy soils. Results show that after 4 or 5 months of growth, all crops had become moderately tolerant to toxicity; indeed, shoot Cd bioconcentration factor (BCF) values were 37.4, 17.0, 11.5, 10.5, 5.8, 3.9, and 1.4 for Sedum alfredii (SA), Witloof chicory (WC), edible-leaf beet (EB), Cardamine hupingshanensis (CH), leafy mustard (LM), oil mustard (OM), and perennial ryegrass (PR), respectively, while shoot Pb and Zn BCF values were less than 1 and 5, respectively. And SA, WC, EB, and CH all had higher shoot Cd accumulation capacities, especially SA in which the level reached 53.9 mg kg−1. The calculation results of restoration potential show that it will take at least 5 years for WC, 7 years for SA and EB, and 10 years for CH to reach the repair target. These results show that it is possible to grow winter crops to repair soil Cd pollution, with WC, EB, CH, and SA, the best candidates for making full use of fallow periods while simultaneously achieving soil phytoremediation. The results of this study will prove useful for establishing a new summer production model by ensuring the winter repair of contaminated paddy soil.

Cadmium accumulation in winter crops and the assessment of paddy soil phytoremediation in southern China

The invention relates to a method for improving the capability of endives for removing cadmium from heavy-metal-polluted soil by using fertilization and harvesting techniques. The method comprises the following steps: planting the endives into the heavy-metal-polluted soil according to the natural growth period for regular cultivation, harvesting the endives after the endives are matured, and applying fertilizers after harvesting each time to improve the enrichment capability of the endives on the cadmium and fulfill the aim of removing the excessive cadmium from the soil. When the endives grow normally in the cadmium-polluted soil, no obvious poison symptoms occur, so that the yield of the endives is not affected; furthermore, the overground parts of the endives have large biomass, so that the endives can be harvested for multiple times in the growth period to absorb and accumulate a plenty of various metals; particularly, the content of the heavy metals (cadmium) in the plants is obviously higher than the background value of the soil, so that the enrichment level is achieved. The method for cultivation is simpler, and the management cost is low; multiple benefits can be earned from one-time planting; after the endives are simply detoxified, the heavy metals can be prevented from entering a food chain, so that considerable economic income can be obtained when the pollution is treated.

Method for improving capability of endives for removing cadmium from heavy-metal-polluted soil by using fertilization and harvesting techniques

The invention provides a method for improving the soil cadmium removal capability of tobacco by use of a fertilization and harvesting technology. The method comprises the following steps of: transplanting tobacco seedlings to heavy metal cadmium contaminated soil according to a natural growing period of the tobacco seedlings, performing conventional cultivation, applying additional fertilizers during a vigorous growing period, and harvesting tobacco after the tobacco seedlings are mature; and performing conventional cultivation again, and applying additional fertilizers so as to promote growth of regenerated tobacco, so that the cadmium absorption and enrichment capability is improved by virtue of application of additional fertilizers and the growing process of regenerated tobacco, and thus the purpose of removing excessive cadmium in soil is achieved. The tobacco seedlings can grow normally in cadmium contaminated soil without obvious toxic symptoms and influence on tobacco yield, and the tobacco seedlings can be regenerated; furthermore, the overground part of the tobacco is large in biomass, so that a large amount of heavy metal cadmium can be absorbed and accumulated. The method provided by the invention is relatively simple in cultivation and low in management cost; harvesting can be performed twice through once planting; tobacco has relatively high protein content; after being treated, tobacco can serve as a feed, and heavy metals can be prevented from entering a food chain again by virtue of a utilization mode of the tobacco, so that certain economical benefits can be achieved while pollution is treated.

Xihong Zhou

Papers

Comparison of three types of oil crop rotation systems for effective use and remediation of heavy metal contaminated agricultural soil

Phytoextraction of cadmium-contaminated soil and potential of regenerated tobacco biomass for recovery of cadmium

Cadmium accumulation in winter crops and the assessment of paddy soil phytoremediation in southern China

Method for improving capability of endives for removing cadmium from heavy-metal-polluted soil by using fertilization and harvesting techniques

Method for improving soil cadmium removal capability of tobacco by use of fertilization and harvesting technology