Cadmium Contaminated Paddy Soils Research Articles

How does the biochar-supported sulfidized nanoscale zero-valent iron affect the soil environment and microorganisms while remediating cadmium contaminated paddy soil?

In previous studies, iron-based nanomaterials, especially biochar (BC)-supported sulfidized nanoscale zero-valent iron (S-nZVI/BC), have been widely used for the remediation of soil contaminants. However, its potential risks to the soil ecological environment are still unknown. This study aims to explore the effects of 3% added S-nZVI/BC on soil environment and microorganisms during the remediation of Cd contaminated yellow-brown soil of paddy field. The results showed that after 49 d of incubation, S-nZVI/BC significantly reduced physiologically based extraction test (PBET) extractable Cd concentration (P < 0.05), and increased the immobilization efficiency of Cd by 16.51% and 17.43% compared with S-nZVI and nZVI/BC alone, respectively. Meanwhile, the application of S-nZVI/BC significantly increased soil urease and sucrase activities by 0.153 and 0.446 times, respectively (P < 0.05), improving the soil environmental quality and promoting the soil nitrogen cycle and carbon cycle. The results from the analysis of the 16S rRNA genes indicated that S-nZVI/BC treatment had a minimal effect on the bacterial community and did not appreciably alter the species of the original dominant bacterial phylum. Importantly, compared to other iron-based nanomaterials, incorporating S-nZVI/BC significantly increased the soil organic carbon (OC) content and decreased the excessive release of iron (P < 0.05). This study also found a significant negative correlation between OC content and Fe(II) content (P < 0.05). It might originate from the reducing effect of Fe-reducing bacteria, which consumed OC to promote the reduction of Fe(III). Accompanying this process, the redistribution of Cd and Fe mineral phases in the soil as well as the generation of secondary Fe(II) minerals facilitated Cd immobilization. Overall, S-nZVI/BC could effectively reduce the bioavailability of Cd, increase soil nutrients and enzyme activities, with less toxic impacts on the soil microorganisms.

Improving arsenic and cadmium contaminated paddy soil health and rice quality with plant-animal-based modified biochar: A mechanistic study

Arsenic and cadmium (As/Cd) are toxic elements which negatively impact the health and productivity of rice plants by subjecting them to stress. To address these issues, we developed three biochar amendment materials derived from plant-based corn-stover with iron-magnesium modification (FM@CB), char sourced from animal-based eggshells with iron-magnesium modification (FM@EB), and a blend (1:1, w/w) of both (FM@CEB). Batch adsorption experiment revealed that FM@CB exhibited a Langmuir sorption capacity of 77 mg g−1 for As(III) and 107 mg g−1 for Cd(II). In contrast, FM@EB showed values of 63 mg g−1 for As(III) and 115 mg g−1 for Cd(II), both observed in mixed systems. The exothermic dual adsorption mechanisms could include ion exchange, cation-anion bridging, complexation with surface functional groups, and precipitation processes. Pot trials were conducted, and the findings unveiled a substantial enhancement in rice grain yield with a 2% application of FM@CB, FM@EB, and FM@CEB. Specifically, there was a notable increase of 21.9%, 34.9%, and 37.6%, respectively. Simultaneously, the application led to a reduction in grain As levels by 34.4%, 53.2%, and 42.6%, and grain Cd levels by 48.7%, 71.2%, and 59.9%, respectively, in comparison to the no-amendment control condition. Our study observed a transformation in the soil's microbial community, as beneficial bacterial genera such as Anaeromyxobacter, Citrifermentans, and Desulfovibrio emerged to assist in the detoxification of these metal contaminants. Concurrently, the application of these materials led to a reduction in harmful bacterial genera like Pseudomonas, Flavobacterium, and Massilia. In addition, these amendments decreased the bioavailable As/Cd fractions in the soil and promoted the root-iron-plaque, which effectively sequesters these contaminants, rendering rice quality improvement. Ultimately, the use of these amendments, particularly FM@CEB, holds the promise of protecting rice from harmful metal(loid)s contaminants, increasing yields, and revitalizing the soil. The presence of these unique bacterial genera, especially those capable of detoxifying As/Cd, plays a crucial role in ensuring a healthier and more secure environment for all living organisms.

Role of iron manganese plaque in the safe production of rice (Oryza sativa L.) grains: Field evidence at plot and regional scales in cadmium-contaminated paddy soils

The relationship between iron manganese plaque (IP) and cadmium (Cd) accumulation by rice in the microenvironment of rice rhizosphere at varying field scales needs to be further explored. In this study, we selected different rice varieties and implemented tailored amendments to ensure the safe production of rice grains in heavily Cd-contaminated farmland situated around an E-waste dismantling site. Through regional surveys, we elucidated the role of IP in facilitating safe rice production. The selection of low-Cd accumulating rice varieties and application of appropriate amendments with sufficient dosages allowed for the effective reduction of Cd transport from soil to rice, resulting in a safe concentration of Cd in rice grains. Analysis using a random forest algorithm indicated that iron (Fe) played a more pivotal role than manganese in soil–rice systems in mitigating Cd accumulation in brown rice. The presence of Fe in IP (IP-Fe) at a low loading mass was unfavorable to the Cd-safe production of rice, while at an IP-Fe loading mass of 52 g/kg, the Cd content in brown rice decreased to a safe level. Furthermore, precipitation, coprecipitation, and complexation of surface functional groups contributed to Cd fixation on IP, as indicated by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, electron probe microanalysis, and Fourier-transform infrared spectroscopy with attenuated total reflection. Our results highlighted the key role of IP in the production of Cd-safe rice at different field scales.

Different effects of conventional and biodegradable microplastics on the amelioration process of cadmium-contaminated soil

With the emergence of complex soil pollution problems, the combined contamination of heavy metals and microplastics (MPs) should not be overlooked. Particularly, the safe use of farmland soils deserves more attention. Passivators were commonly used for heavy metal–contaminated soil amelioration. However, the potential impact of MPs on this process is yet to be determined. Herein, the cadmium-contaminated paddy soil was collected to evaluate the effect of MPs on soil properties and bacterial community in soil amelioration. Two types of MPs were investigated, including conventional polyethylene (PE) and biodegradable polylactic acid (PLA). Both MPs decreased the available phosphorus content and bioavailability of cadmium in a similar way, while they changed the soil pH and nitrogen species in a different manner. Additionally, the high-dose PLA treatment induced a considerable decrease in soil pH (from ~5.4 to 3.6), with potential considerable release of carbon substrates and modification of bacterial community. Furthermore, for the ameliorated soil, it has a network structure of less complexity and stabilization, which resulted in greater disparities in the microbial community under different MP treatments. Profiling predicted functions provides insights into the potential correlations among bacterial activities and soil physicochemical properties. The study demonstrated that both PE and PLA could have significant effects on the soil amelioration process and pose a threat to agroecosystems.

Effects of Soil pH on the Growth and Cadmium Accumulation in Polygonum hydropiper (L.) in Low and Moderately Cadmium-Contaminated Paddy Soil

Wetland macrophytes have advantages when used in the remediation of cadmium (Cd)-contaminated paddy fields because they can adapt to overly wet soil environments; however, only a few studies have tested the efficiency of macrophytes in Cd phytoremediation. In this study, we investigated the effect of soil pH (pHs of 5, 6, and 7) on the accumulation and translocation of Cd by Polygonum hydropiper (L.) in low and moderately Cd-contaminated paddy soil (0.56 and 0.92 mg/kg, respectively). Our results indicated that Cd accumulation in stems and roots, as well as subcellular distribution in P. hydropiper, was affected by soil pH, with significant interactions between the soil pH and Cd level. At low soil Cd levels, stem and root Cd contents were higher at a soil pH value of 6. In addition, with higher soil pH values, the proportion of Cd distributed in the cell wall increased, whereas that distributed in the organelles decreased. The Cd content in the roots and stems of P. hydropiper significantly decreased with the increase in soil pH in the moderate Cd-contaminated soil. In addition, with higher soil pH values, the proportion of Cd distributed in the cell wall decreased, whereas that distributed in the organelles increased. The translocation factor (TF) of P. hydropiper was higher than one in all treatments, indicating that it can effectively transport root-absorbed Cd to the aboveground shoots. Based on the relatively high bioconcentration factor and TF, P. hydropiper has the potential to remediate Cd-polluted paddy soil. Furthermore, the remediation efficiency of P. hydropiper can be enhanced by adjusting the pH as per the soil-Cd pollution.

Biochar application in a cadmium-contaminated paddy soil also reduces soil microelement zinc availability and its uptake by rice

Biochar application in a cadmium-contaminated paddy soil also reduces soil microelement zinc availability and its uptake by rice

Salicylic acid improves Nasturtium officinale phytoremediation capability for cadmium-contaminated paddy soils.

Cadmium (Cd) contamination is a severe problem in paddy soils that has affected crops' safety. The present study aimed at remediating Cd-contaminated paddy soil by improving the phytoremediation capability of aquatic accumulator plants. We conducted an experiment to investigate the effects of salicylic acid (SA) on the growth and Cd phytoremediation capability of the aquatic accumulator plant Nasturtium officinale. SA with the concentrations of 100, 150, and 200 mg/L increased the root and shoot biomass of N. officinale, while only 150 mg/L increased the chlorophyll a and b contents. SA increased the activities of peroxidase and catalase of N. officinale to a great extent, but decreased the superoxide dismutase activity and soluble protein content. SA also increased the root Cd content, shoot Cd content, root Cd extraction, and shoot Cd extraction to a large extent. At concentrations of 100, 150, and 200 mg/L, SA increased the shoot Cd extraction by 17.59%, 47.16%, and 43.27%, respectively, compared with the control. Moreover, SA concentration had a quadratic polynomial regression relationship with the root Cd extraction and shoot Cd extraction. The correlation and grey relational analyses revealed that root Cd extraction, shoot biomass, and root biomass were closely associated with shoot Cd extraction of N. officinale. Thus, our results suggest that SA promoted the growth and improved the phytoremediation (extraction) capability of N. officinale, and 150 mg/L SA was the most suitable concentration.

An amino acid fertilizer improves the emergent accumulator plant Nasturtium officinale R. Br. phytoremediation capability for cadmium-contaminated paddy soils.

Cadmium (Cd) contamination of paddy soil affects safe crop production. This study aimed to evaluate the effects of plant biostimulant amino acid fertilizer on the phytoremediation capability of an emergent accumulator plant Nasturtium officinale R. Br. for Cd-contaminated paddy soils. A pot study was carried out to study the effects of different concentrations of amino acid fertilizer on the Cd accumulation of N. officinale grown in Cd-contaminated paddy soil. The amino acid fertilizer increased the biomass of N. officinale. The amino acid fertilizer concentration exhibited a quadratic polynomial regression relationship with the root and shoot biomass. The fertilizer also increased the photosynthetic pigment (chlorophyll and carotenoid) contents, peroxidase (POD; EC 1.11.1.7) activity, and catalase (CAT; EC 1.11.1.6) activity of N. officinale, but decreased the soluble protein content and had no significant effect on the superoxide dismutase (SOD; EC 1.15.1.1) activity. Furthermore, the amino acid fertilizer increased the Cd content and Cd extraction of N. officinale. The shoot Cd extraction increased by 29.06%, 63.05%, 77.22%, and 17.40% at 1500-, 1200-, 900-, and 600-fold dilutions of the amino acid fertilizer, respectively, compared with the control. Moreover, the amino acid fertilizer promoted the Cd transport from the roots to shoots of N. officinale. The amino acid fertilizer concentration also exhibited a quadratic polynomial regression relationship with the root Cd content, shoot Cd content, root Cd extraction, and shoot Cd extraction, respectively. The correlation, grey relational, and path analyses revealed that the root biomass, shoot biomass, chlorophyll content, catalase activity, shoot Cd content, and root Cd extraction were closely associated with the shoot Cd extraction. Therefore, the amino acid fertilizer can promote Cd uptake and improve the phytoremediation capability of N. officinale to remediate Cd-contaminated paddy soils, and 900-fold dilution is the most suitable concentration.

Study on the Effectiveness and Mechanism of Mercapto-Modified Attapulgite for Remediation of Cadmium-Contaminated Paddy Soil

Study on the Effectiveness and Mechanism of Mercapto-Modified Attapulgite for Remediation of Cadmium-Contaminated Paddy Soil

Phytoremediation with kenaf (Hibiscus cannabinus L.) for cadmium-contaminated paddy soil in southern China: translocation, uptake, and assessment of cultivars.

Kenaf (Hibiscus cannabinus L.) is suitable for growing in heavy metal-polluted soil for non-food purposes and can be used as a potential crop to remediate heavy metal-contaminated soil. The main objective of this study was to investigate kenaf phytoextraction of cadmium (Cd), including uptake, translocation, and accumulation differences in tissues among kenaf cultivars. A field experiment was conducted in a Cd contaminated paddy field in southern China area with 13 kenaf cultivars in 2015 and 2016. Agronomic performance, Cd concentrations in plant tissues (root, xylem, and phloem), and biomass of different tissues of each cultivar were measured and evaluated. Significant differences in Cd concentrations and accumulation among tissues and cultivars were observed. The phloem had the highest Cd accumulation and transfer capability compared with the roots and xylem. Approximately 35 ~ 65g of Cd could be taken up by the aerial parts of different kenaf cultivars within every hectare of soil. The percentage of Cd uptake by the phloem ranged from 47 to 61% and by the xylem ranged from 38 to 53%. By evaluating the agronomic traits and Cd bioaccumulation capacity, Fuhong 952, Fuhong 992, and Fuhong R1 were regarded as Cd accumulators for the phytoremediation of Cd-contaminated soil. Our study clearly demonstrated that a significant level of Cd in the soil was taken up through the phytoremediation with kenaf. In addition, harmless utilization of kenaf planting in Cd-contaminated paddy soil was discussed.

Clay-hydrochar composites return to cadmium contaminated paddy soil: Reduced Cd accumulation in rice seed and affected soil microbiome

Excess cadmium (Cd) in rice precipitated by Cd contamination in paddy soils is a global human health threat and rational response is urgently needed. In this study, attapulgite-modified hydrochar (CA) and the montmorillonite-modified hydrochar (CM) were utilized in Cd-contaminated paddy soils at 0.5% (w/w) and 1% (w/w) application rates to investigate the effects of these clay-hydrochar composites on rice growth and soil Cd availability. The results show that the utility of CA and CM resulted in a significant increase in rice yield, especially at 1% application rate, which extended rice yield by 46.7–50.0% compared to 0.5% application rate. This is related to the Cd fixation and nutrient sequestration of the acidic functional groups on the surface of CA and CM. Additionally, CA-1% and CM-1% reduced the Cd concentration in rice seeds by 26.9–28.1% relative to the control. Notably, CA-1% showed the capacity to passivate Cd at the early stage of rice transplanting, lowering the proportion of Cd in the ion exchange state by 41.6% compared to the control, and this passivation effect persisted until the late stage of transplanted rice. The soil microbial community consequences showed that CA and CM did not significantly change the horizontal composition of the soil bacterial phylum and species diversity, indicating that CA and CM had excessive soil microbial adaptability. Moreover, results of correlation and Canonical Correspondence Analysis confirm that microbial genera responded significantly to the soil Cd morphologies, revealing the importance of CA and CM in the remediation of Cd-contaminated soils by influencing microorganisms. Our findings provide clay-hydrochar composites as a low-cost approach to effectively mitigate soil Cd contamination and improve the security and quality of rice.

Chemodiversity of dissolved organic matter in cadmium-contaminated paddy soil amended with different materials

Dissolved organic matter (DOM) in soil is a key factor affecting the bioavailability of heavy metals, but very few studies have focused on the role of DOM in the use of soil amendments to mitigate heavy metal accumulation in crops. Here, eleven materials were added to cadmium (Cd)-contaminated paddy soil in greenhouse pot trials; rice was grown and harvested, the chemodiversity of post-harvest soil DOM was characterized using Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry, and the specific associations between soil DOM traits and water-extractable soil Cd concentration were identified at the molecular level. The results showed that the endogenous release caused by altering soil pH had a greater effect on soil DOM concentration than did the exogenous chemical input due to the application of organic amendments, which in turn contributed to the chemodiversity of DOM. After one season of rice cultivation, soil DOM molecules were mainly dominated by relatively low molecular weight heteroatom-free lignins. C/N, C/H ratios of organic materials influenced DOM molecular fingerprint patterns, and soil pH and redox potential were the main driving forces affecting the chemodiversity of DOM. Furthermore, the low molecular weight, high saturation, low aromaticity, and heteroatom-free DOM molecules are more likely to dissolve Cd from the soil solid phase, thus increasing the potential risk of Cd to the environment. The results provide critical information about amendments-induced changes in DOM chemodiversity and will inform the selection of appropriate soil amendments.

Responses of microbial community and soil enzyme to heavy metal passivators in cadmium contaminated paddy soils: An in situ field experiment

Heavy metal passivators could reduce the transfer of heavy metal ions from soil to crops and exhibit great potential in safe cropping in heavy metal contaminated agricultural soils. However, the effects of heavy metal passivators on microbial diversity and microorganisms-based biogeochemical processes in agricultural soil are poorly explored. In this study, the effects of three heavy metal passivators, viz. lime, silicon (Si) fertilizer, and gypsum, on the structure and function of microorganisms in cadmium (Cd) contaminated paddy soils were investigated through activity of soil enzyme, microbial abundance and community structure by an in situ paddy field plot experiment. Our results showed that lime application changed the activity of phosphatase and urease through increasing bio-available phosphorus (AP) content in soil and soil pH, respectively. Lime application increased abundance and richness of the prokaryotic microbes in paddy soil, while gypsum application increased evenness of the eukaryotic microbes. Si fertilizer application resulted in the increase of evenness of both prokaryotic and eukaryotic microbes. The results presented in this study suggest that application of heavy metal passivator lime, Si fertilizer, and gypsum could improve microbial diversity and function in Cd contaminated paddy soil.

The impact of stabilizing amendments on the microbial community and metabolism in cadmium-contaminated paddy soils

Since biomagnification takes place in food chains, cadmium (Cd) contamination in paddy fields has aroused substantial concern. The remediation of soil cadmium by amendment addition has been commonly implemented in agriculture. However, for sustainable development, this technology still has unclear microbial and metabolic effects. In the present study, a 3-month in situ field-scale experiment was performed to clarify how five compound amendments with different pH values affect the Cd concentration, soil microbes and metabolic activities related to Cd transformation. Compared with the control treatment CK1 (Cd-polluted soil), the five amendments noticeably decreased the content of soil-available Cd, which was lowest in alkaline treatments (approximately 0.2 mg/kg). In the acidic treatment (E), the Shannon diversity was reduced in both June and September, whereas the abundant genera related to ammonia oxidation, namely, Nitrospira and Nitrosospira, were enriched. Among the Cd transformation genes identified, genes participating in Cd2+ transport, reducedglutathione (GSH) metabolism, and nitrogen and sulfur metabolism showed considerable variations. Genes participating in nitrogen fixation, sulfate dissimilation and Cd2+/Zn2+-exporting ATPases and relevant microbes (e.g., sulfur-reducing and nitrogen-fixing bacteria) exhibited their maximal abundances in alkaline treatments A and D. Genes participating in GSH metabolism and sulfate assimilation, which affected the intracellular precipitation of CdS and Cd complexation by GSH, exhibited their maximal abundances in the E and D treatments. As suggested from the results achieved here, of two critical metabolisms (N and S), nitrogen fixation more significantly accounted for soil Cd reduction. To successfully combine remediation and microbial effects, soil parameters and components should be rigorously considered to minimize additional effects on the soil ecosystem.

A two-year field study of using a new material for remediation of cadmium contaminated paddy soil

Cadmium (Cd) as a highly toxic heavy metal can cause seriously harmful to human health. Rice consumption is a major source of Cd intake by Chinese. Reduce the Cd accumulation by rice is the key for reducing Cd hazard. Therefore, fly ash (FA) was used as raw material in this study, after the process of simplifying hydrothermal synthesis the zeolite (ZE), which was named as low-temperature-alkali roasting, a new intermediate materials (IP) was got. And the three mentioned materials (FA, IP and ZE) were used for a two-year field experiment. The study demonstrated that, application of IP and ZE could promote rice growth, as well as increase soil pH, and improve available Si content. The rice production increased by 36.1% and 29.8% in 2017 by IP and ZE applied, enhanced 35.9% and 31.7% in 2018, respectively. Meanwhile, the bio-available Cd decreased by 26.9% and 26% in 2017, reduced by 22.9% and 28% in 2018, respectively. Generally, the passivators could promote the conversion of acid-exchangeable fraction Cd to reducible fraction Cd. It can be conclude that, IP and ZE have good remediation effect on contaminated soil, and alleviated effects on Cd accumulation by rice, even though no significant difference was detected between IP and ZE. The synthesis process of IP of is simpler than ZE. The impact of IP on contaminated soil needs further exploration.

Control of Cadmium Migration and Transformation in Alkaline Paddy Soil-Rice Using Cotton Stalk Biochar

We investigated the effects of cotton stalk biochar addition on the soil nutrient characteristics of alkaline paddy soil and the migration and transformation of cadmium in a soil-rice system. An outdoor pot experiment was conducted with Tefengyou 2 rice as the testing material. We added cotton stalk biochar (0%, 1%, 2.5%, and 5%) in the alkaline paddy soil with cadmium content of 0, 1, 4, and 8 mg·kg-1. After rice harvesting, the effects of different concentrations of cotton stalk biochar on alkaline soil physical and chemical properties, cadmium enrichment and transfer in rice, and the occurrence of cadmium in soil were analyzed under different concentrations of cadmium stress. The results showed that ① adding cotton stalk biochar can effectively increase soil nutrient (P<0.05). After the addition of cotton stalk biochar, the organic matter increased by 25.74%-47.53%, and the available potassium content increased by 3.16-4.25 times. ② Cotton stalk carbon can reduce the cadmium content in soil and rice, especially after the application of 5% cotton stalk carbon, The cadmium content of brown rice at Cd4 and Cd8 concentrations decreased from 0.31 mg·kg-1 and 0.43 mg·kg-1 to 0.15 mg·kg-1 and 0.10 mg·kg-1, respectively, reaching the national standard. Cotton stalk biochar can significantly reduce the enrichment and transfer coefficient of cadmium in soil-rice systems and can increase the cadmium content in the residual cadmium but decrease the acid extractable cadmium, reducible cadmium, and oxidizable cadmium content (P<0.05). ③ Soil pH, conductivity, and nutrient indicators were significantly negatively correlated with cadmium content in rice and acid extractable cadmium, reducible cadmium, and oxidizable cadmium content in soil and were positively correlated with cadmium content in residual cadmium. The above results indicate that the application of cotton stalk biochar can significantly improve the soil nutrient of alkaline cadmium-contaminated paddy soil, and the application of cotton stalk biochar has a significant control effect on the migration and transformation of cadmium in alkaline soil and rice.

Rice intercropping with alligator flag (Thalia dealbata): A novel model to produce safe cereal grains while remediating cadmium contaminated paddy soil

Phytoremediation has been employed as a cost-effective technique to remove the cadmium (Cd) from soil and water in several ecosystems. However, little is known about whether intercropping the remediating plants with rice (Oryza sativa) crop could reduce Cd accumulation in rice grains. We conducted greenhouse pot and concrete pond trials to explore the effects of intercropping alligator flag (Thalia dealbata, Marantaceae) on soil Cd remediation, paddy soil and microbial properties, and rice production. Our results suggest that intercropping with alligator flag significantly decreased Cd absorption, transportation, and accumulation from the soil to the rice grains (under 0.2 mg kg–1 at a soil Cd content below 2.50 mg kg–1). This decrease was due to the lowered Cd availability and higher soil pH in the rice-alligator flag intercropping system. Although planting alligator flag resulted in the reduction of soil NH4-N and NO3-N, Cd content in the rhizosphere was the main factor restricting microbial biomass, species, and community composition. Alligator flag could tolerate higher Cd contamination, and accumulate and stabilize more Cd in its tissues than rice. Our study suggests that alligator flag intercropped with rice has potential as a phytostabilization plant to produce rice safely for human consumption in moderately Cd-contaminated soils.

Bioremediation of cadmium-contaminated paddy soil using an autotrophic and heterotrophic mixture.

Cadmium (Cd) pollution poses a serious risk to human health and ecological security. Bioremediation can be a promising and effective remediation technology for treating Cd contaminated soils. In this study, seven heterotrophic strains were isolated from Cd contaminated soil and 7 autotrophic strains were isolated from acid mine drainage. Cd removal efficiencies were compared after leaching with autotrophic bacteria (Att-sys), heterotrophic isolates (Htt-sys) and cooperative leaching systems (Co-sys) in laboratory agitating reactors. The results indicated that Cd removal efficiency of Co-sys (32.09%) was significantly higher than that of Att-sys (23.24%) and Htt-sys (0.74%). By analyzing the soil microbial community in different bioleaching systems, we found that the addition of heterotrophic isolates significantly promoted the growth of some heavy metal resistant inhabitants (Massilia, Alicyclobacillus, Micromonospora, etc.), and Co-sys had a minor effect on the growth of soil indigenous microbes. In Co-sys, the content of the four Cd fractions all decreased compared with other leaching systems. The analysis of soil physicochemical parameters during the leaching process showed that pH and ORP (oxidation reduction potential) were not the only determinants for Cd removal efficiency in Co-sys, synergistic metabolic activities of autotrophic and heterotrophic strains may be other determinants. This study demonstrated that cooperative bioremediation may prove to be a safe and efficient technique for field application in heavy metal soil pollution.

水稻秸秆草木灰对镉污染水稻土修复效果研究

水稻秸秆草木灰对镉污染水稻土修复效果研究

Dynamics and potential roles of abundant and rare subcommunities in the bioremediation of cadmium-contaminated paddy soil by Pseudomonas chenduensis.

Microbial bioremediation of heavy metal-contaminated soil is a potential technique to reduce heavy metals in crop plants. However, the dynamics and roles of the local microbiota in bioremediation of heavy metal-contaminated soil following microbial application are rarely reported. In this study, we used Pseudomonas chenduensis strain MBR for bioremediation of Cd-contaminated paddy soil and investigated its effects on the dynamics of the local soil bacterial community and Cd accumulation in rice. Cd accumulation in rice grains and roots were significantly reduced by the addition of the strain MBR. The addition of the strain MBR caused greater changes in bacterial communities in rhizosphere soil than in bulk soil. MBR enhanced the roles of microbial communities in transformation of Cd fractions, especially in rhizosphere soil. The strain MBR likely regulated abundant subcommunities more than rare subcommunities to improve Cd bioremediation, especially in rhizosphere soil. Consequently, the dynamics and functional roles of the local microbial communities differed significantly during bioremediation between abundant and rare subcommunities and between rhizosphere soil and bulk soil. This study provides new insight into the microbiota-related mechanisms underlying bioremediation.