Excessive levels of cadmium (Cd) in soil exert serious negative impacts on soil ecosystems. Microorganisms are a common component of soil and show great potential for mitigating soil Cd. This review summarizes the application and remediation mechanisms of microorganisms, microbial-plants, and microbial-biochar in Cd-contaminated soil. Microorganisms such as Bacillus, Acinetobacter, Pseudomonas, and arbuscular mycorrhizal fungi (AMF) can change the biological validity of Cd through adsorption, mineralization, precipitation and dissolution. Different factors such as pH, temperature, biomass, concentration, and duration have significant effects on Cd bioavailability by microorganisms. Pseudomonas, Burkholderia, and Flavobacterium can promote the uptake of Cd²⁺ by hyperaccumulator through promotion and activation. Biochar, a soil amendment, possesses unique physicochemical properties and could act as a shelter for microorganisms in agriculture. The use of combined microbial-biochar can further stabilize Cd compared to using biochar alone.
Cadmium ; Ecosystem ; Soil Pollutants ; Charcoal/chemistry* ; Soil/chemistry*

OBJECTIVEIn this study, five heavy metals contamination of soil and different parts of Panax notoginseng in the plantation area was investigated. Analysis of heavy metals correlation between the planting soil and P. notoginseng; and the absorption and accumulation characteristics and translocation of soil heavy metals by P. notoginseng plants was revealed.

METHODThrough field investigation and laboratory analytical methods, analysis of China's 30 different soil P. notoginseng origin and content of heavy metals in five different parts of the P. notoginseng plant content of heavy metals.

RESULTThe results revealed that the soil heavy metals should not be neglected in the plantation area Referring to the national soil quality standards (GB15608-1995), the excessive degree of soil heavy metals pollution showed Hg > As > Cd > Cr in the plantation area, and Pb content of soil was in the scope of the standard. Refer to 'Green Industry Standards for Import and Export of Medical Plants and Preparations', the excessive degree of heavy metals content of P. notoginseng plants showed As > Pb > Cr > Cd, and Hg content of plants was in the scope of the standard. Concentrations of five heavy metals of underground parts of P. notoginseng plants are higher than aboveground, and heavy metals elements are more concentrated in the root, followed by the rhizome of P. notoginseng plants. Heavy metal accumulation characteristics of the different parts of the P. notoginseng of the overall performance is the root > the rhizome > the root tuber > leaves > stems. From the point of view BCF value analysis of various parts of the P. notoginseng plants to absorb heavy metals in soil, BCF values of all samples were less than 1, description P. notoginseng not belong Hyperaccumulator. From the view of transportation and related analysis of the soil-P. notoginseng systems, the rhizome of P. notoginseng and the content of As and Cr in soil was significantly correlated, the root of P. notoginseng and the content of Cd in soil was significantly correlated, and no significant correlation between the other indicators. Through the analysis of transportation transfer coefficient showed: Pb, As and Cr are not easy to transport aboveground part from the underground, but Cd and Hg are relatively easy to transport stems from rhizome, the migration of five heavy metals in the aerial part is relatively strong, and heavy metal of stems is easily transported to the leaves.

CONCLUSIONP. notoginseng does not belong to the enrichment of heavy metals in crops, especially for Hg in soil with strong patience. In survey area, the content of heavy metals of P. notoginseng's planting soil is relatively high, and the heavy metals As, Pb, Cr, Cd of P. notoginseng also exist heavy metals exceeded problems. Due to the presence of heavy metals in crops internal absorption and translocation of special laws, accumulation of heavy metals varied significantly in different parts of P. notoginseng. The overall, the performance for the heavy metal content of the underground parts is more than aboveground, it explain heavy metals of P. notoginseng plants is still the main source of the soiL Therefore, the key to control of planting area soil environmental quality and reduce exogenous harmful substances secondary pollution of soil in the cultivation process are to study and solve the heavy metals pollution problem of P. notoginseng.

Adsorption ; China ; Laboratories ; Metals, Heavy ; analysis ; Panax notoginseng ; chemistry ; Soil ; chemistry ; Soil Pollutants ; analysis

The effect of vermicomposting on kinetic behavior of the products is not well recognized. An incubation study was conducted to investigate C mineralization kinetics of cow manure, sugarcane filter cake and their vermicomposts. Two different soils were treated with the four solid wastes at a rate of 0.5 g solid waste C per kg soil with three replications. Soils were incubated for 56 d. The CO(2)-C respired was monitored periodically and a first-order kinetic model was used to calculate the kinetic parameters of C mineralization. Results indicated that the percentage of C mineralized during the incubation period ranged from 31.9% to 41.8% and 55.9% to 73.4% in the calcareous and acidic soils, respectively. The potentially mineralizable C (C(0)) of the treated soils was lower in the solid waste composts compared to their starting materials. Overall, it can be concluded that decomposable fraction of solid wastes has decreased due to vermicomposting.
Industrial Waste ; prevention & control ; Kinetics ; Refuse Disposal ; methods ; Soil ; analysis ; Soil Pollutants ; chemistry ; isolation & purification

In order to understand the pollution of heavy metals in Guizhou soil planting Eucommia ulmoides,the paper has determined the contents of five heavy metals respectively( Cu,Cd,Pb,Hg and As) by atomic absorption spectrophotometry. The soil environmental quality by single factor pollution index was evaluated,nemerow integrated pollution index and potential ecological risk index,the correlation of 5 heavy metals was analyzed and the relationship between heavy medals content and p H value was discussed. The results showed that: ①The soils of LP,SB and ZA-2 had low heavy metals content,LP soil met the first national standard,and other soils met the second national standard; ②The soils of LP,ZA-1 and ZA-2 were all in a clean state,while HX and BZ-1 were in a light pollution state,and the pollution degree was Cu>Pb>As>Cd>Hg; ③The soil of BZ-2 was light warning( medium ecological risk),the soils of HX,BZ-1 and MT were early warning( low ecological risk),the main warning source was Cu and Pb,and the rest were no warning( no ecological risk); ④Cd and As were positively correlated with Pb and Hg,and Cd,Pb and As were positively correlated with p H. The research showed that the soils of LP,SB,ZA-1 and ZA-2 were clean and could be used for E. ulmoides to continue planting,the soils of HX,MT,BZ-1 and BZ-2 were polluted and should be treated in time by effective measures.
China ; Environmental Monitoring ; Eucommiaceae ; Metals, Heavy ; analysis ; Risk Assessment ; Soil ; chemistry ; Soil Pollutants ; analysis

In this study, the effects of two plant growth-promoting bacteria Klebsiella michiganensis TS8 and Lelliottia Jeotgali MR2 on the growth and cadmium (Cd) uptake of Arabidopsis thaliana under Cd stress were explored. A wild-type Arabidopsis thaliana was selected as the experimental plant and was planted at different Cd concentrations. MR2 and TS8 bacterial suspensions were sprayed onto the rhizospheric soil during the planting process. The initial Cd concentration of the bought soil was 14.17 mg/kg, which was used as the pot soil of the low-concentration Cd treatment group (LC). The concentration of soil Cd at high-concentration Cd treatment group (HC) were 200 mg/kg higher than that at LC group. Compared with the control group, MR2 suspension significantly promoted the growth of A. thaliana at both low and high concentrations, while TS8 strain and MR2_TS8 mixture only exhibited growth-promoting effect at high concentration. However, it was noteworthy that, TS8 suspension significantly reduced the Cd content in the underground parts of A. thaliana (60% and 59%), and significantly improved the Cd content in the aboveground parts of A. thaliana (234% and 35%) at both low and high concentrations. In addition, at low concentration, both single strain and mixed strains significantly improved the transformation from reducible Cd to acid-extractable Cd in soil, promoted Cd intake, and thereby reduced the total Cd content in soil. Therefore, the rational application of plant growth-promoting bacteria may improve crop yield and remediate Cd contamination in soil.
Arabidopsis ; Bacteria ; Biodegradation, Environmental ; Cadmium/pharmacology* ; Enterobacteriaceae ; Klebsiella ; Plant Roots/chemistry* ; Soil ; Soil Pollutants

The remediation of heavy-metal (HM) contaminated soil using hyperaccumulators is one of the important solutions to address the inorganic contamination widely occurred worldwide. Hyperaccumulators are able to hyperaccumulate HMs, but their planting, growth, and extraction capacities are greatly affected by HM stress. The application of arbuscular mycorrhizal fungi (AMF) enhances the function of hyperaccumulators by combining the functional advantages of both, improving the efficiency of remediation, shortening the remediation cycle, and maintaining the stability and persistence of the remediation. Thus, the combined use of AMF with hyperaccumulators has broad prospects for application in the management of increasingly complex and severe HM pollution. This review starts by defining the concept of hyperaccumulators, followed by describing the typical hyperaccumulators that were firstly reported in China as well as those known to form symbioses with AMF. This review provides a systematic and in-depth discussion of the effects of AMF on the growth of hyperaccumulators, as well as the absorption and accumulation of HMs, the effects and mechanism on the hyperaccumulator plus AMF symbiosis to absorb and accumulate HMs. AMF enhances the function of hyperaccumulators on the absorption and accumulation of HMs by regulating the physicochemical and biological conditions in the plant rhizosphere, the situation of elements homeostasis, the physiological metabolism and gene expression. Moreover, the symbiotic systems established by hyperaccumulators plus AMF have the potential to combine their abilities to remediate HMs-contaminated habitat. Finally, challenges for the combined use of remediation technologies for hyperaccumulator plus AMF symbiosis and future directions were prospected.
Biodegradation, Environmental ; Metals, Heavy ; Mycorrhizae/chemistry* ; Plant Roots/chemistry* ; Soil Pollutants ; Symbiosis

OBJECTIVEThe wetland at Dalian Bay in the Northeast of China has been polluted by oil severely. The effect of various microbes and operation parameters on the bioremediation of oil-polluted wetlands at Dalian Bay was investigated and reported previously. In the study, other operation conditions related to the status of medium were investigated via statistical experimental design and analysis and a necessary information is involved to use micro-technology in the application.

METHODSThe method used involved the direct inoculation of selected bacteria, which were capable of degrading oil. The operation conditions were further optimized and evaluated by gravimetrical assay.

RESULTSThe optimal pH and temperature for the studied bacteria to degrade the existing oil pollutants were established as pH 8.0 and 27 degrees C. The mixed of various bacteria showed better results in terms of oil degradation than any single one. Among the selected four factors, disturbance, oxidant, nutrients, and biosurfactant, the former two contributed more impacts on the oil degradation in the early stage of process, while the latter two became the limiting factors in the late stage. Three sets of optimal conditions were obtained for each individual stage, but no one was suitable for the overall process.

CONCLUSIONThe study demonstrated the technical feasibility of using direct inoculation into the contaminated soil samples to remove oil pollutants. It suggested that the operation conditions should be monitored and adjusted during the different stages of bio-reactions in the process to achieve the best result of oil degradation.

Bacteria ; metabolism ; Biodegradation, Environmental ; China ; Ecosystem ; Hydrogen-Ion Concentration ; Oceans and Seas ; Petroleum ; metabolism ; Soil ; analysis ; Soil Pollutants ; chemistry ; metabolism ; Temperature

OBJECTIVETo investigate the performance of soil-slurry bioreactor used for remediating contaminated soil with 4-nitrophenol (4-NP).

METHODSThe slurry bioreactor was used to degrade different concentrations of 4-nitrophenol with or without inoculating the acclimated activated sludge. HPLC system (Hewlett-Packard model 5050 with a UV detector) was used for the quantification of 4-nitrophenol.

RESULTSThe indigenous microorganisms exhibited a little activity for simulated soil with 50 mg 4-NP/kg soil. However, at the concentration of 10 mg 4-NPkg soil, a considerable degradation occurred within two weeks. It appeared that high concentrations of 4-nitrophenol apparently produced an inhibitory effect on microbial activity. For system receiving 50 mg 4-NP/kg soil, the maximum rate of 4-NP degradation measured in the reactor inoculated with 25 g sludge/kg soil was approximately 10 times higher than the uninoculated reactor, suggesting that the degradation rate of 4-nitrophenol could be enhanced greatly by means of inoculating acclimated sludge.

CONCLUSIONThe addition of sludge capable of degrading 4-nitrophenol can result in enhance the degradation rate of 4-nitrophenol.

Biodegradation, Environmental ; Bioreactors ; Chromatography, High Pressure Liquid ; Nitrophenols ; metabolism ; Sewage ; chemistry ; microbiology ; Soil Microbiology ; Soil Pollutants ; metabolism ; Time Factors

Iron (Fe) deficiency and excess cadmium (Cd) in rice grain are important problems to be solved in agricultural production. Previous studies have shown that OsVIT1 and OsVIT2 are vacuolar iron transporters. In this study, wild-type ZH11 was selected as the background material and OsVIT1 and OsVIT2 were overexpressed in endosperm by using endosperm specific promoter Glb-1. Field experiments were conducted to study the effect of OsVIT1 and OsVIT2 overexpression on Fe and Cd accumulation in different parts of rice. The results showed that OsVIT1 overexpression in endosperm significantly reduced Fe content in grain by about 50%, while significantly increased zinc (Zn) and copper (Cu) contents in straw and Cu content in grain. OsVIT2 overexpression in endosperm significantly decreased Fe and Cd contents in grain by about 50%, and significantly increased Fe content in straw by 45%-120%. Overexpression of OsVIT1 and OsVIT2 in endosperm did not affect the agronomic traits of rice. In conclusion, OsVIT1 and OsVIT2 overexpression in endosperm reduced Fe accumulation in rice grain, which did not achieve the expected effect. OsVIT2 overexpression in endosperm also decreased Cd accumulation in grain and increased Fe accumulation in straw, which provided reference for iron biofortification and cadmium reduction in rice.
Cadmium ; Endosperm/chemistry* ; Oryza/genetics* ; Iron ; Zinc ; Edible Grain ; Soil Pollutants

The hydroponic culture test method was used to study the physiological and biochemical responses of Paulownia fortunei seedlings under Zn stress, Cd stress, and combined Zn and Cd stress as well as changes in the enrichment and transfer characteristics of heavy metals. Under single and combined heavy metal stress, the biomass, plant height, and peroxidase (POD) activity of P. fortunei decreased as the treatment concentration increased. Combined Zn and Cd affected adversely plant height and biomass. As the concentration of Zn increased when applied alone, the chlorophyll content and catalase (CAT) activity of P. fortunei first increased and then decreased, the superoxide dismutase (SOD) activity increased, and the aboveground malondialdehyde (MDA) content first decreased and then increased. As the concentration of Cd increased when applied alone, chlorophyll content and CAT activity increased, and SOD activity and aboveground MDA content first increased and then decreased. Under both Cd and Zn, the physiological response was more complex. Cd in the seedlings of P. fortunei was concentrated in the root. In contrast, Zn was concentrated in the upper part of the ground, and its transfer coefficient was greater than 1.00. Thus, the addition of Zn promotes the transfer of heavy metals to the above-ground portions of plants. Generally, P. fortunei can effectively promote ecological restoration under complex forms of heavy metal pollution.
Cadmium ; Chlorophyll ; Metals, Heavy ; Plant Roots/chemistry* ; Seedlings ; Soil Pollutants ; Stress, Physiological ; Superoxide Dismutase ; Zinc