Foliar inhibition technology is widely recognized as an efficient and practical approach for mitigating cadmium (Cd) accumulation within rice crops. However, the interactions of foliar application involving various elements in relation to Cd absorption and transport in rice are still not fully understood. A field experiment was conducted to examine the synergistic effects of foliar applying a zinc (Zn)-manganese (Mn) mixture (ZnSO4 + MnSO4) during rice critical growth stages. Subcellular localization, chemical fractionation techniques, and the quantification of transcriptional activity for key genes involved in Cd transport were analyzed to study the influence of foliar spraying of Zn-Mn on Cd absorption, accumulation, and distribution in rice. Spraying Zn-Mn solution onto rice leaves could significantly reduce the absorption and movement of Cd within the rice tissues. Foliar applying 0.5 g·L⁻1 ZnSO4 and 0.25 g·L⁻1 MnSO4 during tillering and filling stages led to a 16.9

Co-contamination of tetracycline (TC) and cadmium (Cd) is common in wastewater from intensive livestock farming and aquaculture. However, quantitative understanding of the coupled removal of antibiotic-heavy metal co-contaminants by the same modified biochar remains limited, while many modification strategies rely on corrosive reagents and complex post-treatment procedures that hinder low-cost and scalable application. This study prepared KHCO3-modified biochar (KBCs: RKBC, YKBC, HKBC, CKBC) via one-step co-pyrolysis of KHCO3 with four agricultural residues (rapeseed meal-straw, corn stover, peanut shells, and Rosa roxburghii residue), for the removal of TC and Cd from wastewater. Compared to raw biochar, KBCs exhibited significantly enhanced textural properties: specific surface area increased by 35.17-305.71-fold, and total pore volume expanded by 27.71-69.98-fold. KBCs exhibited strong resistance to ionic interference, regenerability, and adaptability. At pH 6.0 and 298 K, the best-performing RKBC effectively removed TC/Cd from wastewater. Isotherm models determined maximum adsorption capacities of 496.31 ± 14.212 mg g-1 for TC and 95.67 ± 3.549 mg g-1 for Cd, representing 9.02-fold and 12.33-fold improvements over the corresponding pristine biochar. Mechanistic analyses indicate that TC retention is primarily driven by hydrogen bonding (26.50-32.60%), with electrostatic attraction (18.53-22.42%) and pore filling (6.12-20.32%) as secondary contributions, whereas Cd immobilization is dominated by pore filling (36.92-40.46%) and electrostatic attraction (20.80-27.25%), supplemented by mineral precipitation (10.51-12.81%) and π-Cd interaction (5.41-11.57%). In a pilot-scale three-stage treatment system based on RKBC, TC and Cd decreased from 136.35 to 0.36 mg L-1 to 0.89 and 0.04 mg L-1, respectively, supporting the engineering potential of KBCs in TC-Cd coexisting wastewater.

The adverse impacts on microplastics derived from plastic mulching films to agroecosystems has become increasingly pronounced. At present, existing research has predominantly focused on single regions or processes, and systematic integrative analyses of their contamination status, influencing factors, and field management measures remain scarce. This research gap has hindered the effective prevention and control of microplastic contamination from plastic mulch. Using a meta-analytical approach, this study screened 2,881 relevant publications and synthesized 484 datasets on plastic mulch-derived microplastics across diverse geographical regions, mulch types, and management modes. By coupling the XGBoost model with SHAP analysis, this study quantitatively identified the key determinants of plastic mulch-derived microplastic contamination and put forward efficient technical pathways for contamination management. The results showed that plastic mulching increases soil microplastic abundance, which rises over time and declines with depth, and is higher in peanut fields. Microplastic accumulation peaks at 400–800 mm precipitation, 10-15°C, sunshine duration below 2500 hours and strong evaporation. Annual mean temperature, altitude, and mulching duration are core drivers, with abundance following the order: temperate continental > subtropical monsoon > temperate monsoon > alpine mountainous > tropical monsoon climates. Therefore, source-oriented prevention strategies are more effective than end-of-pipe treatment measures. This study aims to provide robust scientific evidence and theoretical support for the targeted prevention and control of agricultural plastic mulch-derived microplastic contamination, the formulation of relevant policies, and the rational application of plastic mulching films.

In this study, water, fish and bird samples from the Xisha Islands were collected and the species-specific accumulation and biomagnification of PFASs between aquatic and terrestrial biota were investigated. ΣPFAS concentrations ranged from 0.15 to 3.61 ng/L in the seawater, from 1.4 to 35 ng/g wet weight in fish tissues, and from nd to 61 ng/g wet weight in bird tissues. PFASs concentrations follower order of liver > gills > muscle in the fish and liver > heart > muscle in bird. Perfluorooctanoic acid (PFOA) was the dominant PFASs in water. Long chain perfluorocarboxylic acid (C9-14) dominated in fish while perfluorooctanesulfonic acid (PFOS) dominated in most of bird samples, which indicated different PFASs exposure source for fish and bird sample. The trophic magnification factors were <1 for aquatic biota (fish) while >1 for the terrestrial biota (bird) in this study, which may be influenced by various factors such as biotransformation, ecological characteristics. Traditional single compound risk assessment indicated a low risk of fish consumption, but the mixed risk assessment using relative potency factors (RPF) suggested that children's exposure to multiple PFASs through consuming certain local fish might pose health risks. Our research will contribute to a more comprehensive assessment of PFAS pollution and its ecological impacts in the Xisha Islands region of the South China Sea.

Identifying plants suitable for phytoremediation coupled with agro-production in heavily cadmium (Cd)-contaminated agricultural land is crucial. This study conducted kenaf (Hibiscus cannabinus L.) pot experiments (four Cd levels: 1.18–9.76 mg·kg−1) and two-year field experiments (initial soil total Cd: 11.38 mg·kg−1). Dynamic sampling analysis of pot experiments shows that as the Cd content in the soil increases, the growth and development function of kenaf does not stop, and the Cd content and accumulation in both above- and belowground parts increase. At maturity stage (October), soil total Cd and bioavailable Cd (DTPA-Cd) decreased by 16.88%–68.44% and 16.63%–24.96%, respectively, with the remediation efficiency peaking at 18.44% when soil Cd content was 1.18 mg·kg⁻¹ . Field experiments found two-year kenaf cultivation reduced soil total Cd by 12.83% and DTPA-Cd by 27.88%, with annual Cd extraction amounts of 1110.18–1459.72 g·hm−2 and annual remediation efficiency of 4.34%–6.04%. Rhizosphere microbial analysis revealed that Cd stress minimally affected bacterial diversity but reduced arbuscular mycorrhizal fungi (AMF) diversity; dominant bacterial phyla included Chloroflexi, Acidobacteriota, and Proteobacteria, while dominant AMF genera were Glomus and Claroideoglomus,and the relative abundances of Candidatus_Solibacter, Acidothermus, Bradyrhizobium, and Sphingomona were increased under the soil Cd 9.76 mg·kg−1 treatment; soil pH, available nitrogen, available phosphorus, and DTPA-Cd were key drivers of microbial community structure. These findings suggest that kenaf exhibits strong Cd tolerance, high accumulation capacity, while simultaneously maintaining agricultural productivity and positively influencing the rhizosphere microbiome.

Identifying plants suitable for phytoremediation coupled with agro-production in heavily cadmium (Cd)-contaminated farmland is crucial. This study conducted kenaf (Hibiscus cannabinus L.) pot experiments (four Cd levels: 1.18~9.76 mg·kg-1) and two-year field experiments (initial soil total Cd: 11.38 mg·kg-1). Dynamic sampling analysis of pot experiments revealed that the Cd content and accumulation in the aboveground and belowground parts of kenaf increased with rising soil Cd levels and plant growth; at maturity stage (October), the contribution rate of Cd accumulation reached 58.05%–71.23%; soil total Cd and bioavailable Cd (DTPA-Cd) decreased by 16.88%–68.44% and 16.63%–24.96%, respectively, with the remediation efficiency peaking at 18.44% when soil Cd content was 1.18 mg·kg⁻¹. Field experiments found two-year kenaf cultivation reduced soil total Cd by 12.83% and DTPA-Cd by 27.88%, with annual Cd extraction amounts of 1110.18–1459.72 g·hm-2 and annual remediation efficiency of 4.34%–6.04%. Rhizosphere microbial analysis revealed that Cd stress minimally affected bacterial diversity but reduced arbuscular mycorrhizal fungi (AMF) diversity; dominant bacterial phyla included Chloroflexi, Acidobacteriota, and Proteobacteria, while dominant AMF genera were Glomus and Claroideoglomus,and the relative abundances of Candidatus_Solibacter, Acidothermus, Bradyrhizobium, and Sphingomona were increased under the soil Cd 9.76 mg·kg-1 treatment; soil pH, available nitrogen, available phosphorus, and DTPA-Cd were key drivers of microbial community structure. These findings suggest that kenaf exhibits strong Cd tolerance, high accumulation capacity, while simultaneously maintaining agricultural productivity and positively influencing the rhizosphere microbiome.

The prolonged consumption of arsenic-contaminated water is linked to an elevated risk of cancer. As(III) in wastewater exhibits greater mobility, biotoxicity, and removal challenges than As(V). Acidic mine drainage (AMD) sludges are solid wastes produced by mining industry. In this study, a novel biochar modified with AMD sludge (AMDs@PB2) was prepared via co-pyrolysis of AMD sludge and pine needles to remove As(III) from the solution. The effects of preparation conditions (pyrolysis temperature, raw material ratio) and environmental factors (solution pH, solution temperature, coexisting ions) of biochar on arsenic adsorption were investigated, and the arsenic adsorption performance of AMDs@PB2 was analyzed by kinetic, isothermal and thermodynamic models. The results show that the optimal pyrolysis temperature for AMDs@PB2 is 800 degrees C, and the mass ratio of AMD sludge to pine needles is 2:1. AMDs@PB2 can effectively remove As(III) from water, thereby achieving the 'treating waste with treated waste' concept. The maximum theoretical adsorption capacity (Qe, the) of AMDs@PB2 for As(III) in wastewater is 83.35 mg g- 1, which is approximately 1.07-31.18 folds greater than Qe, the reported in previous studies. AMDs@PB2 adsorption was slightly affected by anions (15-75 mg L- 1 CI-, NO3-, SO42-, PO43-) and humic acid and its removal rate ranged from 83.48 to 97.57 %. In addition, the AMDs@PB2 adsorption process involves multilayer heterogeneous adsorption. As(III) adsorption by AMDs@PB2 at 25 degrees C is thermo respiratory and spontaneous. The oxidation-reduction reaction, surface complexation, and coprecipitation dominated the immobilization of As(III) in the water environment by AMDs@PB2.

Alleviating cadmium (Cd) risk in paddy soils is a global research hotspot. Although biochar reduces Cd mobility, a holistic perspective on the effects of biochar on Cd fraction distribution in rice rhizosphere and its immobilization mechanisms is lacking. Here, we developed a pathway model that links soil physicochemical properties, IP formation, enzyme activity, microbial biomass, porewater nutrients, and soil Cd fractions to fill knowledge gaps. Results revealed that phosphorus-loaded magnetic biochar (PMLB) application increased soil pH, available phosphorus (AP), total phosphorus (TP), microbial biomass, and TP and Fe contents in porewater while inhibiting soil enzyme activities. Compared with the control, 0.2 %-1 % w/w PMLB treatment reduced soil acetic acid-extractable Cd (Aci-Cd) content during the tillering, filling, and maturity periods by 23.71-32.92 %, 25.45-37.33 %, and 7.39-18.40 %, respectively. Cd content in brown rice was reduced by 44.02-47.86 %. Soil pH, AP and urease activity were the primary drivers of soil Aci-Cd reduction. Soil microbial biomass contributed most to reducing Cd content in rice tissues (total path coefficient: -0.48), followed by enzyme activity and IP. Additionally, PMLB promoted IP formation and altered the immobilization methods of Cd by IP, from coprecipitation with iron (hydr)oxides and phosphate to ternary complex formation with phosphate as a bridge to band Cd and iron (hydr)oxides.

BACKGROUND:Iron plaque on the rice rhizoplane could potentially prevent cadmium (Cd) entry into plant roots. A hydroponic experiment was conducted to study the morphological characteristics and mineral compositions of iron plaque, Cd immobilization mechanism by iron plaque, and its effect on Cd uptake and transport in rice. RESULTS:Exogenous divalent iron ion (Fe(II)) could induce the formation of deep-red iron plaque on rice rhizoplane, which primarily consisted of ferrihydrite, goethite, hematite, iron phosphate, and iron sulfate compounds. The results of X-ray photoelectron spectroscopy and X-ray diffraction indicated that the conversion of Fe(II) into ferric ion (Fe(III)) during the formation of iron plaque could promote the adsorption and immobilization of Cd in iron plaque. Meanwhile, Cd content in amorphous and crystalline fractions of iron plaque increased by 29.9-97.3% and 13.6-97.9%, respectively, during the formation of iron plaque. Correlation analysis indicated that fractions of amorphous and crystalline Fe might effectively combine with Cd in the iron plaque on rice rhizoplane. Furthermore, the content of Cd in the above-ground parts of rice decreased by 2.75-35.2% during the formation of iron plaque. Also, the translocation factors of Cd from rice roots to shoots showed a gradually decreasing trend with increasing Fe(II) concentration in the solution. CONCLUSION:Cd could be effectively adsorbed on iron plaque and immobilized on rice rhizoplane, thus further reducing the transport of Cd from roots to the above-ground parts in rice. © 2025 Society of Chemical Industry.

Microplastics (MPs) are recognized as emerging soil contaminants. However, the potential risks of MPs to agroecosystems have not been fully revealed, especially the compound toxic effects of MPs with co-existing organic or inorganic pollutants (OPs/IPs) in agricultural fields. In this study, we quantified the contributions of different agronomic practices to the sources of MPs in soil and highlighted the important influences of long-term tillage and fertilization on the migration and aging of MPs in agricultural fields. In addition, the antagonistic and synergistic interactions between MPs and OPs/IPs in soil were explored. We emphasized that the degree of adsorption of MPs and soil particles to OPs/IPs is a key determinant of the co-toxicity of those contaminants in soil. Finally, several directions for future research are proposed, and these knowledge gaps provide an important basis for understanding the contamination process of MPs in agricultural soils.

Cadmium (Cd)-contaminated rice paddies have been a primary environmental concern worldwide. Biochar or modified biochar application favors reducing Cd availability in paddy soil, which has been demonstrated in physical and chemical terms. However, we know little about soil microbial responses after biochar application. In this study, we revealed the immobilization effect and mechanism of Cd in paddy fields by a novel phosphorite magnetic biochar (PMCB) from the perspective of soil microbial response. The results suggested that PMCB application facilitated the conversion of highly active Cd to less active Cd in soil and reduced Cd uptake by rice by improving soil physicochemical properties and functional bacterial and gene abundance. Compared with the control, acetic acid extractable Cd and reducible Cd contents in soil and Cd content in brown rice decreased by 7.4%-18.4%, 16.2%-19.9%, and 44.0%-47.9%, respectively, and residual Cd content increased by 16.3%-25.8% under PMCB treatment. A decrease in sqr and fccB gene abundances (downregulated by 6.3% and 12.4%, respectively) inhibited CdS oxidative dissolution after 0.2% PMCB application. Conversely, other treatments stimulated the abundant proliferation of functional microbes (e.g., Anaeromyxobacter, Geobacter, and Thiobacillus) and these genes while suppressing sulfide-producing gene abundance (sreA and phsA decreased by 30.5%-73.4% and 3.3%-11.3%, respectively). This result implies that Fe(III) mineral reduction and CdS oxidation lead to a limited secondary release of Cd. Additionally, aqueous-phase analysis of the immobilization mechanism revealed that PMCB immobilized Cd mainly by coprecipitation with PO43- and CO32- (34.5%) and ion exchange (32.2%), followed by surface complexation (18.7%) and cation pi-bonding (13.1%).

Non-grain production of cultivated land (NGPCL) threatened food security. Therefore, scholars have begun study this area in China and other countries, but most of the studies have focused on large scales, and few studies have focused on plot scale analysis. This study presents an analytical framework to shed light on the causes of NGPCL in the hilly mountainous regions of southern China. First, we categorized NGPCL into severe damage class and slight damage class according to the degree of damage of NGPCL to cultivated soils and the difficulty of restoring food production capacity. Then, we revealed the characteristics of spatial differentiation and causes of NGPCL in the southern hilly areas by using methods such as binary logistic regression model and spatial correlation analysis. Finally, the results in the study showed that: (1) the overall NGPCL areal in 2020 was 11288.46 hm ^2 , accounts for 38.14%, of which the areas of NGPCL in the minor damage class and the serious damage class were 27.32% and 10.82%, respectively. (2) The spatial differentiation of NGPCL was obvious, which showed a clustered distribution pattern, with NGPCLs of the minor damage class clustered at high values in the topographically flat areas of the east-central zone, and NGPCLs of the severe damage class clustered at high values in the vicinity of the central urban area. (3) The levels of NGPCL for each type were significantly correlated with the three dimensions of natural, locational, and socio-economic factors, while topography, cultivated land infrastructure conditions and the degree of centralized and contiguous cultivated land were the important drivers of spatial differentiation of NGPCL. This paper reveals the distribution and influencing factors of NGPCL at the plot scale, that can provide theoretical reference and categorized governance suggestions for NGPCL governance in similar regions in China and even in the world.

Multi-metals contamination in agriculture soil poses a significant challenge, threatening wheat quality. The effects of cow dung (CD) and cow dung biochar (CDB) applied to contaminated soil on heavy metals (HMs) uptake and microbial diversity in wheat were tested with pot experiment. CD and CDB applications reduced soil Cd/Zn ratio by 30 % and inhibited Cd uptake by wheat roots. Compared to the CK, CD doses of 0.5 %, 1 %, and 2 % reduced Cd content in grains by 12.7 %, 37.0 %, and 35.3 %, respectively, and CDB doses of 0.05 %, 0.1 %, and 0.2 % reduced it by 16.7 %, 27.7 %, and 51.9 %, respectively. CD and CDB changed the HMs fraction distribution in the soil and reduced the proportion of acid-extractable and Fe-Mn oxidized fractions. The significant negative correlation between the acid-extractable fractions of Cd and Pb in soil and pH, confirming that increased pH reduces the acid-extractable fraction of HMs in soils. CD reduced the alpha-diversity of soil microorganisms, but the total number of edges, nodes, and microbial taxa positive correlation ratio increased by 168 %, 34.5 %, and 9.97 %, respectively, resulting in more complex and tightly packed soil microbial network structure. Signature microorganisms such as Alphaproteobacteria, Mycobacterium spp. and Rhizobium spp. appeared in 1 % and 2 % of the dosage CD treatments, furthermore the abundance of metabolism-related genes such as amino acid synthesis, organic matter metabolism and citrate cycle were upregulated, which was favorable for soil nutrient cycling and transformation. Applying CD can mitigate wheat HMs uptake, improving crop safety and soil health and promoting eco-friendly agricultural practices.

Strong acidity of antimony (Sb) mine drainage enhances Sb and arsenic (As) mobility, posing serious environmental risks. The secondary iron-rich minerals (e.g., goethite, ferrihydrite, and hematite) in acid mine drainage (AMD) sludge can serve as effective iron sources and significantly enhance the Sb immobilization capacity of biochar modified with iron-rich minerals through the specific coordination of its surface iron (hydr)oxides with Sb. Based on above evidence, this study was conducted to develop a "using waste to treat pollution" strategy by developing a novel pH-responsive AMD sludge-modified biochar (SPNB2: 800 degrees C and 2:1 AMD sludge/pine needle ratio). Results demonstrated that the maximum adsorption capacities (Qe) of SPNB2 were 47.54 mg/g (Sb(III)) and 147.92 mg/g (Sb(V)), following a spontaneous, temperature-enhanced multilayer chemisorption mechanism. SPNB2 maintained optimal performance in strongly acidic (pH 2-3) and complex anionic environments (Cl-/NO3-/SO42-, 10-150 mg/L), enabling synergistic immobilization of As(III)-Sb(III/V) with combined Qe values of 84.52 mg/g (As(III)-Sb(III)) and 184.61 mg/g (As(III)-Sb(V)). Immobilization mechanisms of SPNB2 predominantly involve surface complexation, hydrogen bonding, redox reactions, pi-pi interactions, and pore filling. SPNB2 effectively immobilized Sb in soil at a 4 % dosage via mixed filling, converting highly mobile Sb fractions (nonspecifically/specifically adsorbed forms) to residual Sb and reducing Sb leaching risk. These results highlighted the satisfactory performance of SPNB2 in the remediation of Sb-contaminated water and soil.

Arsenic (As) is a common toxic metalloid, and in As-contaminated paddy soils, safe rice production is crucial for human health. In this study, lanthanum-modified biochar (BC-L) was developed to reduce soil As availability and limit As accumulation in rice. Characterization using SEM-EDS, FTIR, XRD, and XPS revealed that La modification increased the biochar surface roughness, introduced La-OH groups, and facilitated La-O-As complex formation, which is essential for As immobilization. Applying BC-L significantly increased soil pH, CEC, and OM, helping convert bioavailable As into more stable forms and decreasing TCLP- and NaHCO3extractable As by up to 30.7 % and 21.4 %, respectively. Simultaneously, BC-L reduced As buildup in rice, with inorganic As in brown rice decreasing by 31.7-40.8 % (below 0.35 mg/kg), while biomass increased by 6.0-14.5 %. Mechanistically, BC-L acted through La complexation and iron plaque regulation at low doses (0.5-1 g/kg), thereby enhancing iron plaque sequestration. In contrast, higher doses (2-4 g/kg) primarily relied on direct soil As immobilization. It also lowered As phytotoxicity and prevented As translocation to grains. From an economic and practical perspective, the optimal application rate of BC-L was 1 g/kg, making it an effective amendment for remediating As-contaminated soils.

Cadmium (Cd) pollution poses a severe threat to rice safety and human health, while traditional linear models exhibit significant limitations in predicting rice Cd accumulation due to environmental complexities. This study systematically evaluated the predictive performance of Random Forest (RF), Gradient Boosting Decision Tree (GBDT), and Residual Neural Networks (ResNet), using a multi-source soil–rice dataset comprising 57,200 samples from Hunan Province. The results showed that the RF model performed best on the test set (R2 = 0.62), with the dominant features being soil’s available Cd (contributing 9.74%) and precipitation during the rice-filling stage (joint contribution of 15.96%). However, the model’s predictive performance experienced a sharp decline on the independent 2023 validation set comprising 393 samples from Yizhang County and Lengshuitan District, with R2 values ranging from −0.12 to −0.31. This highlighted the fundamental limitations of static data-driven paradigms. Agronomic management measures, simplified by heterogeneous data and binary encoding, failed to effectively represent the actual intervention intensity. The study demonstrated that while machine learning models captured nonlinear relationships in laboratory environments, they struggled to adapt to the dynamic interactions and spatiotemporal heterogeneity of farmland systems. Future efforts should focus on developing hybrid models guided by mechanistic insights, integrating dynamic environmental processes and real-time data, and promoting localized “one model per region” strategies to enhance predictive robustness. This study provides methodological insights for the technological transformation of agricultural artificial intelligence, emphasizing that the deep integration of data-driven approaches and mechanistic understanding is crucial for overcoming the “last mile” challenge.

Woody plants have received considerable attention for the phytoremediation of heavy metal-contaminated soil. This study aimed to investigate the changes in antioxidant enzyme activity, macroelement uptake and microstructure of the woody plant Robinia pseudoacacia (black locust) for the phytoremediation of cadmium (Cd) and lead (Pb) co-contaminated soil based on dynamic sampling. The results show that black locust demonstrates strong tolerance in Cd and Pb co-contaminated soil. After 30-120 days of cultivation, the activities of superoxide dismutase, peroxidase and the macroelement (potassium [K] and calcium [Ca]) content in plant leaves significantly declined in response to Cd and Pb. However, after 160 d of cultivation, the antioxidant enzyme activities, chlorophyll, sulfhydryl and soluble protein contents, as well as Ca and magnesium content in plant leaves were returned to normal levels under the 40 mg kg-1 Cd and 1000 mg kg-1 Pb contaminated soil (CdPb3). Meanwhile, K content in plant leaves under the CdPb3 treatment was significantly (P < 0.05) increased by 68.9% compared with the control. Cadmium and Pb were primarily accumulated in black locust roots. Scanning electron microscope analysis indicated that the sieve tubes in the roots and stems of plant might block the transport of Cd and Pb. Transmission electron microscope analysis indicated that the number and volume of osmiophilic particles in plant leaves were increased and the cell walls were thickened in response to Cd and Pb stress. Path analysis further indicated that the growth of plant was related to macroelements uptake and physiological change (photosynthesis, antioxidant enzyme activity and chelation). Thus, black locust could effectively regulate the antioxidant defense system, macroelement absorption and microstructure to enhance plant tolerance to Cd and Pb stress. Moreover, black locust could maintain the normal urease, acid phosphatase and sucrase activities in the Cd and Pb co-contaminated soil. These findings suggest that black locust could be considered as a useful woody plant for the phytostabilization in Cd- and Pb-contaminated soil.

The impacts of straw removal on rice Cd absorption, behaviour of Cd and microbial community in rhizosphere soil were investigated in paddy fields over two consecutive seasons. The results of the experiments in two fields revealed that straw removal promoted the transformation of soil Cd from acid-extractable and oxidisable fraction to residual fraction and reduced soil DTPA-Cd content with the reduction in DOC and Cd ions in soil porewater, thereby decreasing Cd content in rice. Specifically, the Cd content in brown rice was below 0.2 mg·kg-1 when all rice straw and roots were removed in the slightly Cd-contaminated soils. The α-diversity of soil microbial communities was less influenced by continuous straw removal, β-diversity was altered and the relative abundances of Anaeromyxobacter, Methylocystis and Mycobacterium microbes were increased. Redundancy analysis and network analysis exhibited that soil pH predominantly influenced the microbial community. Path analysis revealed that the Cd content in brown rice could be directly influenced by the soil Total-Cd and DTPA-Cd, as well as soil pH and OM. Straw removal, including roots removal, is an economical and effective technique to reduce Cd accumulation in rice plants.

In this study， a field experiment was conducted to examine the effects of the application of irrigation water containing Zn at the key growth period （booting stage and filling stage） on exchangeable Cd content in the soil， Cd concentration in pore water， and Cd uptake and transport in rice in a Cd-contaminated paddy field in Liuyang City， Hunan Province. The results indicated that： ① the application of irrigation water containing Zn during the key growth period could inhibit the releasing process of exchangeable Cd from the soil into pore water. Compared with that in the control， the content of exchangeable Cd in soil was slightly changed， but the concentration of Cd in soil pore water at the mature stage was significantly reduced by 16.7%-57.6%. ② The application of irrigation water containing Zn at the key growth period could significantly reduce the Cd content in various parts of rice. Cd contents in root， stem， and brown rice with the application of irrigation water containing 20 mg·L-1 Zn before the booting and the filling stage （BF1） were significantly decreased by 56.0%， 83.8%， and 85.2%， respectively. ③ Compared with the application of 100 mg·L-1 irrigation water containing Zn， the application of 20 mg·L-1 irrigation water containing Zn significantly reduced the uptake and transport of Cd in rice， and the translocation factor （TF） of Cd from rice roots to stems was also significantly reduced by 12.5%-56.3%， with the B1 and BF1 treatments reaching significant levels. These results suggested that the application of irrigation water containing Zn could significantly reduce the uptake and accumulation of Cd in rice， and the application of 20 mg·L-1 irrigation water containing Zn before the booting and filling stage could effectively realize the safe production of Cd-contaminated paddy fields.

Sweet sorghum has a large biomass and strong cadmium (Cd) absorption capacity, which has the potential for phytoremediation of Cd-contaminated soil. In order to study the Cd phytoremediation effect of sweet sorghum assisted with citric acid on the typical parent materials in southern China, a field experiment was carried out in two typical parent material farmland areas (neutral purple mud field and jute sand mud field) with Cd pollution in Hunan Province. The results showed that:① Citric acid had no inhibitory effect on the growth of sweet sorghum. After the application of citric acid, the aboveground biomass of sweet sorghum at the maturity stage increased by 10.1%-24.7%. ② Both sweet sorghum planting and citric acid application reduced the soil pH value, and the application of citric acid further reduced the soil pH value at each growth stage of sweet sorghum; this decrease was greater in the neutral purple mud field, which decreased by 0.24-0.72 units. ③ Both sweet sorghum planting and citric acid application reduced the total amount of soil Cd, and the decreases in the neutral purple mud field and jute sand mud field were 23.8%-52.2% and 17.1%-31.8%, respectively. The acid-extractable percentage of soil Cd in both places increased by 38.6%-147.7% and 4.8%-22.7%, respectively. ④ The application of citric acid could significantly increase the Cd content in various tissues of sweet sorghum. The Cd content in the aboveground part of the plant in the neutral purple mud field was higher than that in the jute sand mud field, and the Cd content in stems and leaves was 0.25-1.90 mg·kg-1 and 0.21-0.64 mg·kg-1, respectively. ⑤ After applying citric acid, the Cd extraction amount of sweet sorghum in neutral purple mud soil in the mature stage reached 47.56 g·hm-2. In summary, citric acid could enhance the efficiency of sweet sorghum in the phytoremediation of Cd-contaminated soil, and the effect was better in neutral purple mud fields. This technology has the potential for remediation coupled with agro-production for heavy metal-contaminated farmland.