Goethite (α-FeOOH), a stable iron oxide prevalent in paddy soils, often incorporates foreign metal ions such as Zn2+ via isomorphic substitution. While iron oxides are widely studied for heavy metal adsorption, most research is conducted under high-temperature conditions (e.g., 70°C), with limited attention to ambient environments. This study systematically synthesized Zn-substituted goethite (Zn-Gth) with varying substitution levels at 25°C, 40°C, and 70°C via co-precipitation. The influence of Zn substitution on the structure and surface properties of goethite was comprehensively investigated using XRD, XPS, TG, SEM, and TEM. Batch adsorption experiments were conducted to elucidate the Cd2+ adsorption mechanism. Results indicate that Zn incorporation decreased crystallinity, induced a leftward shift of the (110), (130), (021), and (111) XRD peaks, increased unit cell volume, and decreased crystal density. The emergence of Zn 2p peaks in XPS spectra confirmed successful substitution. XPS O 1s analysis revealed a shift in hydroxyl oxygen binding energy, while TG analysis indicated reduced thermal stability. Microscopic observations indicate that Zn doping increases the crystal length, reduces the crystal width, and renders the crystal surface rougher. Dissolution tests demonstrated that Zn enhanced goethite dissolution, reducing its chemical stability. Adsorption experiments revealed that Cd2+ adsorption capacity increased with Zn substitution, reaching a maximum of 12.62 mg/g at pH 5.0. This work provides fundamental insights into the structural and surface characteristics of Zn2+/Fe3+ substituted goethite and its Cd adsorption behavior, contributing significantly to the theoretical framework of goethite structure-reactivity relationships.

Understanding the interfacial interactions between soil-derived environmentally persistent free radicals (EPFRs) and minerals is crucial for assessing their environmental fate and potential risks, yet the mechanisms remain poorly elucidated. Here, we characterized EPFRs from three typical soils (red soil (S1), fluvo-aquic soil (S2), and black soil (S3)) and investigated how UV-activated humic acid (HA)-derived EPFRs modify montmorillonite (Mon), kaolinite (Kao), and goethite (Goe) surfaces. We found that native soil EPFRs are source-dependent characteristics: S1-EPFRs exhibited the lowest g-factor (g = 2.00149), S2-EPFRs showed the highest concentration (5.051 & times; 1015 spins/g), and S3-EPFRs possessed the longest half-life (11.95 f 0.45 h). Upon UV activation, the interfacial modification patterns of minerals by HA-EPFRs exhibited source and mineral dependence. O--CO/COOH showed the highest content on Goe (30.75%), while C--O/C-O reached maximum on Mon (28.82%); the -OH peak intensity increased on Mon but decreased on Goe. The Kao system showed the largest increase in the relative change rate of Fe3+ (388.01%), while the Goe system exhibited the most dramatic fluctuations in the relative change rate of Fe3+. HA-EPFRs modified mineral surfaces through four synergistic pathways: direct electron injection, C-O-M coordination bond reconstruction, ROS-mediated oxidation, and targeted functional group modification. These pathways produced distinct interfacial outcomes: thin-layer adsorption, carbon enrichment (C up to 74.47% on Goe), oxygen-rich layer formation (O up to 91.78% on Kao), and oxidative etching. This study demonstrates that HA-EPFRs-mineral interfacial interactions are dually controlled by EPFR source and mineral type, providing a mechanistic basis for predicting EPFRs environmental persistence and developing mineral-based strategies for heavy metal and organic pollutant control in soils.

​Cr(VI) is a priority soil contaminant, yet current risk assessments for earthworms still rely largely on single-species, lethal endpoints. In this study, we systematically compared the sensitivity of 12 earthworm species, representing ​epigeic, endogeic and anecic life forms, to Cr(VI) using four toxicity indicators spanning multiple levels of biological organization: growth inhibition (EC50), acetylcholinesterase (AChE) inhibition, protein secondary-structure alteration (circular dichroism, CD), and coelomic fluid osmolality. Species-specific dose–response curves were fitted with log–logistic models to derive EC50 values or inhibition rates for each endpoint. These endpoint-specific EC50 datasets were then used to construct species sensitivity distributions (SSDs) and to estimate the hazardous concentration for 5% of species (HC5) for each endpoint. Across the 12 species, EC50 values showed pronounced interspecific variability, ranging from a ~2.7-fold span for growth inhibition to a ~27-fold span for AChE inhibition (EC50:10.21~280.44 mg·kg-1). Sublethal endpoints produced lower HC5 values than growth inhibition, and the SSDs revealed a consistent ranking of protection thresholds: AChE inhibition < protein structural change < coelomic-fluid osmolality deviation < growth inhibition. The AChE-based HC5 was approximately one order of magnitude lower than the growth-inhibitory HC5, indicating that neurochemical disruption occurs at substantially lower Cr(VI) concentrations than those causing community-level growth inhibition. Results establish AChE inhibition as the most sensitive and protective endpoint for deriving soil Cr(VI) ecological thresholds, providing a mechanistic basis for refining soil environmental quality standards.

The aging of pollutants determines their bioavailability and the corresponding toxicity thresholds in soil environments. However, existing ecotoxicological assessments of heavy metals, antibiotics, and pesticides in facility agricultural soils rarely incorporate the confounding influences of contaminant aging and soil physicochemical properties. This study selected six facility agricultural soils with differing properties and assessed their toxic effects on Chinese cabbage (Brassica rapa subsp. chinensis) biomass following exogenous addition of cadmium (Cd), tetracycline (TC), and imidacloprid (IM), administered both individually and in combination. Under single Cd contamination, the EC50 for biomass inhibition increased from the 14-day value to 30.0 mg kg-1 after 360 days of aging. For combined contamination, the EC50 reached 18.3 mg kg-1 for Cd-TC and 24.5 mg kg-1 for Cd-IM over the same aging period. In the acidic soils, a low-dose tetracycline inducing hormetic response was observed, with biomass stimulation exceeding 110% of the control. As aging progressed from 14 to 360 days, pollutant toxicity declined. During early aging, no significant difference in aging factors was observed between composite and single pollutants. However, in the later stages, the aging factors for composite pollutants were significantly higher than those of single pollutants. Among these, the Cd-TC aging factor was lowest in Guangxi red soil (AF360d = 3.21), and highest in Henan alluvial soil (AF360d = 3.82). Furthermore, the aging factor increment was more pronounced for Cd-TC mixtures than for Cd-IM. In different types of facility agricultural soils, soil organic matter and clay content can effectively predict the soil aging process as the aging period increases. All predictive models for aging factors were derived, for single Cd contamination as: (AF180d) = -0.256 + 0.455 lg pH + 0.511 lg CEC + 0.593 lg OM (R2 = 0.884, p < 0.01). These findings provide data and theoretical support for the development of aging factor prediction models and the establishment of environmental quality standards for combined contamination involving heavy metals and emerging pollutants in facility agricultural soils.

The revision of environmental quality standards for cadmium (Cd) in Chinese farmland soils remains challenged by insufficient toxicological data. To safeguard agricultural product safety, this study established parent material-specific environmental risk thresholds (hazardous concentration for 5 % (HC5) of species represents a protective threshold designed to safeguard approximately 95 % of species from significant adverse effects) for Cd in paddy soils by integrating the Species Sensitivity Distribution (SSD) method with the collected data from pot experiments and literature data. Toxicity data were normalized using aging factors (AF360 = 1.38-3.47) derived from 360 days equilibration. Results revealed significant HC5 variations across parent materials: granite weathered soil (SG) showed the highest threshold (0.53 mg/kg), while quaternary red soil (SQ) exhibited the lowest (0.17 mg/kg). A predictive model incorporating soil properties was developed: lgHC5 = 1.336lgpH + 0.941lgOM + 0.530lgCEC - 3.45, which collectively explained 95.1 % of the variation in HC5 values. Field validation confirmed model reliability, with measured Cd concentrations (0.011-2.0 mg/kg) falling within twice the predicted error range. This work provides a science-based framework for setting Cd thresholds tailored to soil parent materials, emphasizing their critical role in pollution control strategies for rice safety.

In order to clarify the stabilization characteristics of cadmium (Cd) after different aging methods, soil culture tests of freeze-thaw, wetting-redrying cycles, and natural aging affecting on Cd phytotoxicity to rice were conducted. According to the national food safety standard GB2762-2022, the toxicity thresholds (RT) of Cd under different aging modes were derived. The results showed that: as the aging time increased to 360 days, the RT of different parent soils increased by 28.49 %-204.86 % (freeze-thaw), 37.80 %-192.55 % (natural), 34.45 %-205.87 % (wetting-redrying), compared with 14d' aging. Compared with natural aging: The RT of granite soil ( SG ), river sandy mud ( SR ), stucco field ( SS ) increased by 99.46 % under freeze-thaw aging, decreased by 66.68 % under wetting-redrying aging; The RT of purple sandy shale ( SP ), quaternary red clay soil (SQ) decreased by 20.32 % under freeze-thaw aging, increased by 70.99 % under wetting-redrying aging. RT of yellow mud soil (SY) showed a decreasing trend under unnatural aging. The prediction models of RT based on different parental characteristics under different aging methods were established: log10(AF360)=1.038AG-0.251Chaol-1.052, log10(AF360 )= 0.481pH +1.492CEC +1.223MW-6.375, log10(AF360)= 0.119pH +0.264CEC +1.091AD + 0.263. The regression coefficients of aging factors (AF360), which were 1.04, 1.49, and 1.09 respectively, provided that water-stable aggregates (AG), cation exchange capacity (CEC), and the adhesive film (AD) were the primary controlling factors influencing RT with positive correlations. This study provided an important basis for evaluating different long-term aging modes affecting on soil Cd toxicity behavior and RT of Cd on rice.

Unstable pe+pH (a soil redox parameter representing the total variation of pH and Eh, pe = -log(10)(e(-)) = Eh (mV)/59.2) environment caused by alternation flooding and drainage cycles can alter aggregate structure. However, the mechanism of aggregate restructuring and its impact on Cd distribution remains poorly understood. Contaminated soils were collected from three different rice-growing regions in China and then were subjected to a 40-day anaerobic incubation followed by a 20-day oxidation period. The contribution of known binders, including iron (Fe) oxides and soil organic carbon (SOC), to aggregate structural stability and its impact on DTPA-Cd distribution were investigated. The results show that flooding decreased laterite soil pe+pH from 9.56 to 1.73, resulting in the disintegration of macroaggregates and formation of microaggregates. In addition, free Fe oxides (Fe-DCB) were mainly distributed in macroaggregates, while amorphous Fe oxides (Fe-OA) and SOC tended to accumulate in microaggregates. The greatest decrease of 65.2 %-73.2 % was observed in aggregate mean weight diameter (MWD) after dithionite-citrate-bicarbonate (DCB) extraction, which indicates that Fe-DCB contributed more to aggregate stability than Fe-OA and SOC. Furthermore, flooding stage decreased the content of DTPA-Cd in bulk soil, and that tended to distribute in microaggregates (0.30 and 0.52 mg/kg for the > 2 and < 0.053 mm fraction, respectively). Taken together, unstable pe+pH changed the distribution of Fe oxides and SOC in different aggregate size, resulting in aggregate restructuring, which further impacted Cd distribution in paddy soil.

The latest works have been devoted to the stabilization mensuration for heavy metals and indicate that clay minerals can promote Cd(II) precipitation by favoring the retention of Mn(II). The assessment however has been tempered due to lacking the information about the molecular-level surface complexation structure and Cd nucleation process on clay sur- faces. In this study, microscopic mechanisms for adsorption and stabilization of Cd at mont- morillonite interfaces with or without Mn loading were leveraged by combining surface complexation model (SCM) evaluations and density functional theory (DFT) calculations. Mn(II) substitution resulted in increases in surface acidity equilibrium constant (pKa) a ) by about 1 unit and complexation constant (lgK(SOCd K (SOCd + )) ) of Cd(II) by about 0.15 units at clay surface, and Mn(II) adion can provide extra active sites (i.e., OH-- groups) for complexing Cd(II) via hydrolysis. DFT calculations revealed Mn(II) and Cd(II) adions bind on base sur- faces by isomorphic substitutions through weak long-range interactions, whereas on edge surfaces by surface complexation with strong but short-range connections. Adsorption en- ergy calculations and electrostatic distribution showed heterogenous nucleation with sub- sequent cations on clay surfaces was thermodynamically favored, the stabilization process underwent the steps of the adsorption-hydrolysis-precipitation. The derived results pro- vide a quantitative basis for understanding the precipitation and heterogenous nucleation of cations on clay surfaces in surficial environments. (c) 2025 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Scientific soil environmental quality standards are critical for preventing "over-protection" and "under-protection" of soil ecosystems, and for supporting soil quality and risk assessments. To account for pedogenic processes and spatial heterogeneity in regional soil development, we classified China's agricultural soils into nine zones with distinct soil types and pedogenic properties. Sixty soil samples from diverse ecoregions were analyzed for Cd toxicity using pot experiments and literature-derived datasets. Species sensitivity distribution (SSD) modeling was used to derive region-specific HC5 thresholds (the concentration that protects 95 % of species), revealing significant variability in Cd bioconcentration factors (BCFs: 0.09-1.62) across soil types and crops. Effect concentrations (ECx) for ecological indicators also differed markedly among soils with contrasting physicochemical properties. To account for the changed bioavailability of Cd due to aging processes in real field conditions, toxicity data were corrected using aging factors (AFs). SSD-derived HC5 values varied 0.14-0.72 mg·kg-1 across nine subzones, with regression models linking HC5 to soil properties. Comparative analysis with China's Soil Environmental Quality Standard (GB 15618) highlighted the inadequacy of a uniform national criterion, demonstrating the necessity of region-specific standards. This work provides empirical evidence and methodological frameworks to optimize soil environmental quality regulations across China's agro-ecological zones.

A previous in vivo study showed that lincosamide antibiotics (lincomycin and clindamycin) could induce changes in the gut bacterial community, leading to significant changes in fecal bile acid profiles. Herein, our aim is to develop an animal alternative in vitro model for studying gut microbiota-dependent bile acid profiles induced by xenobiotics. The effects of lincosamides were evaluated using this model, and results obtained were verified by comparing with those of the previous in vivo study. Fecal sample processing and bile acid incubation conditions were developed and optimized using feces collected from Wistar rats, and prepared samples were incubated for 24 h with or without lincosamides. Upon treatment of the fecal gut microbiota with lincosamides primary and secondary bile acids showed obviously increased and decreased levels respectively. Moreover, the changes in bile acid profile could be linked to a reduced richness of family Erysipelotrichaceae, Bacteroidacea and Lactobacillaceae or Prevotellaceae. The consistent consequences of in vivo and in vitro provides a proof of principle for further application on elucidating effects of other xenobiotics on the gut bacterial community and related bile acid metabolism, thereby contributing to the 3Rs (replacement, reduction and refinement) in animal testing. ### Competing Interest Statement The authors have declared no competing interest.

Soil acidifications become one of the main causes restricting the sustainable development of agriculture and causing issues of agricultural product safety. In order to explore the effect of different acidification on soil cadmium (Cd) availability, soil pot culture and hydroponic (soil potting solution extraction) were applied, and non-invasive micro-test technique (NMT) was combined. Here three different soil acidification processes were simulated, including direct acidification by adding sulfuric acid (AP1), acid rain acidification (AP2) by adding artificial simulated acid rain and excessive fertilization acidification by adding (NH4)2SO4 (AP3). The results showed that for direct acidification (AP1), DTPA-Cd concentration in field soils in Liaoning (S1) and Zhejiang (S2) increased by 0.167 - 0.217 mg/kg and 0.181 - 0.346 mg/kg, respectively, compared with control group. When soil pH decreased by 0.45 units in S1, the Cd content of rice stems, leaves and roots increased by 0.48 to 6.04 mg/kg and 2.58 to 12.84 mg/kg, respectively, When the pH value of soil S1 and S2 decreased by 0.20 units, the average velocity of Cd2+ at 200 µm increased by 10.03 - 33.11 pmol/cm2/sec and 21.33 -52.86 pmol/cm2/sec, respectively, and followed the order of AP3 > AP2 > AP1. In summary, different acidification measures would improve the effectiveness of Cd, under the same pH reduction condition, fertilization acidification increased Cd availability most significantly.

At present, there is still a lack driving mechanism for how the biogenetic characteristics of different parent soils affect soil cadmium (Cd) fraction. In this study, the Cd2+ adsorption mechanisms by the clay minerals, iron oxides, soil acidity and organic matter heterogeneity in different parent soils (purple sandy shale (hereby defined as P), quaternary red clay soil (Q), granite soil (G), river sandy mud (R), yellow mud soil (Y), stucco field (S)) were analyzed. The results showed the kaolinite and hematite contents in Q were relatively high, R had a high montmorillonite, Y had a high illite. The soil latent acids content in Q was 1-9 times that of other parent soils. Y had the lowest latent acid content, which was 0.46 cmol center dot kg(-1). With the increase of pH from 4 to 8.5, the removal efficiency of Cd2+ by these soils and main minerals reached up to 98.82 %, and the solid-liquid partition coefficient to 4.19 L center dot g(-1). With the molecular weight increase of the extracted HA in the soils from 3600 to 57339, the complexation stability constant and the maximum coordination number increased from 2.09 and 0.93-5.54 and 1.72, respectively. The Cd2+ different adsorption pathways in soils resulted in certain differences in the intensity of the absorption peaks as indicated by FTIR. For example, the C-O stretching vibration was most pronounced at 1032 cm(-1) in soil R. Through the above studies, the microinterface characteristics and differences of Cd adsorption and binding speciation of different parent paddy soils were revealed.

The derivation of chromium (Cr) ecological risk thresholds in soils remains limited, despite their importance as measurement standards and indicators for enacting soil protection policies. In this study, toxicity of Cr in soil to different species was tested based on Log-Logistic dose-effect relationship. On this basis, combined with Cr toxicity measurement data in literature, the ecological risk threshold HC5 for protecting 95% species safety in soils with different properties was obtained by fitting species sensitivity distribution curve (SSD). This research collected various Cr toxicological data from Chinese cropland soils, based on 31 different endpoints covering soil fauna, functional indicators of microorganisms, terrestrial plants, etc., sourced from both our laboratory and existing literature. We applied the SSD method to estimate the hazardous concentration of Cr for HC5 and ultimately established a predictive model according to HC5 and different soil properties. As a result, the EC10 (an effective concentration of Cr resulting in 10% suppression of terminal biological activity) based on 7 different soils and 4 endpoints ranged from 16.8 to 148.0 mg kg-1, and the hormesis of Cr induction reached up to 109%. Overall, the toxicity (EC10) to microorganisms was much lower, while it was higher for graminoids. All the toxicity data were corrected through an aging factor with up to 540 days of equilibration before fitting the SSD curves. After that, a prediction model considering HC5 values and soil properties was established as LogHC5 = 3.003LogpH + 0.651LogOC + 0.013LogCEC - 0.476. The model was well-verified in field experiments, as the actual and predicted values fell within a 2-fold error range. This approach offers a rigorous scientific foundation for determining the Cr ecological risk threshold and could be important for the conservation of ecological species in soils.

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Soil plastisphere has attracted many concerns, however, its influence on cadmium (Cd) availability in paddy soil was still unclear. This study carried out batch microcosmic and bagging experiments to explore the influence of microplastic (MPs) on Cd availability in paddy soil under flooding conditions in the view of plastisphere. Results showed that the presence of MPs could act as plastisphere micro-environment. The bacterial community composition changed dramatically around the plastisphere compared with MPs-contaminated bulk soil and control soil. The relative abundance of Symbiobacteraceae, Rhodocyclaceae and Bryobacteraceae was improved in the plastisphere which contributed to the enhanced the reduction of Fe(III) and sulfate in flooding paddy soil. The higher content of Fe(II) and S content contributed to the enrichment of Cd in the plastisphere which aggravated Cd availability in paddy soil under flooding conditions. The partial least squares structure equation modeling results confirmed the presence of MPs in paddy soil could act as plastisphere which could change the bacterial community composition and improve the content Fe and S that was conductive to gather Cd in plastisphere. This study shed lights on the understanding of the role of plastisphere on Cd availability in paddy field ecosystem under flooding conditions.

Soil bacterial community structure and rhizosphere metabolites are important pathways for rice to respond to external Cd stress. The specific correlations between these microorganisms, metabolites and inherent soil properties, as well as the mechanisms they utilize to regulate Cd availability across different parent soils remain underexplored, emphasizing the need for deeper understanding to inform effective soil management strategies. In this study, five typical parent soils with large differences in properties (quaternary red clay soil (hereby defined as Q), granite soil (G), river sandy mud (R), yellow mud soil (Y), stucco field (S)) in Chinese paddy soils were collected, and extra Cd were added (CK: 0 mg·kg-1, Cd: 2.4 mg·kg-1).The result indicated that the toxicity impact of Cd in rice grains in G was the weakest, and the highest Cd bioavailability in S. The abundance of Proteobacteria, Bacteroidota and Firmicutes showed an increasing trend in G, while they decreased significantly in S. The contents of Cis-9-palmitoleic acid and phosphoethanolamine increased by 170.02 % and 154.03 % in G, decreased by 218.62 % and 181.58 % in S. MBNT15 and Desulfobacterota showed a significant negative correlation with humic acid molecular weight (MW) extracted from parent soils and Clay (montmorillonite, illite, kaolinite) contents, while they exhibited a positive correlation with soil organic matter (OM) content (P < 0.01). The MW played a crucial role in shaping rhizosphere metabolites with R2 value of 0.8498. These results elucidate how soil bacterial communities, rhizosphere metabolites, and inherent soil properties interact to regulate Cd availability across different parent soils.

Foliar application of rare earth micronutrient of lanthanum (La) exhibits great potential in reducing cadmium (Cd) uptake in crops, the underlying mechanisms controlling the interaction between Cd toxicity-relieved crops and soil microbiota are poorly understood. In this study, LaCl3 with the concentrations of 10 and 30 μM was sprayed on pakchoi (Brassica chinensis L.) planting on Cd contaminated solution and soil to determine the changes of root metabolites and rhizosphere bacterial communities. Compared to the control, Cd concentration in pakchoi leaves was significantly decreased by 30.9 % and 22.6 % with the high group under both hydroponic and pot culture by applying 30 μM LaCl3. Herein, the concrete evidence is provided that pakchoi plants in response to foliar-spraying La under soil or solution Cd toxicity can promote the root secretion of amino acids, resulting in a strong enrichment of nitrogen-related microorganisms. To probe this linkage, a Pseudomonas representative specie was isolated that had the ability of consuming alanine, the most oversecreted root exudate due to La application. Further results demonstrated that this strain had the capacities for alleviating Cd toxicity and enhancing crop growth by immobilizing Cd and secreting plant-beneficial metabolites. This study reveals a plant-extrudate-microbiome feedback loop for responding to La-relieved Cd toxicity in crops by the chemotaxis of rhizosphere Pseudomonas toward alanine secreted by pakchoi.

Organic agriculture is of great socioeconomic significance because it can promote the nutritional quality of horticultural crops and is environmentally friendly. However, owing to the lack of techniques for studying complex aroma-related chemical profiles, limited information is available on the influence of organic practices on the flavor quality of strawberries, one of the primary factors driving consumer preferences. Here, two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GC×GC-TOF-MS) and flavoromics analysis was employed to investigate the profiles and differences in the volatile organic compounds (VOCs) of strawberries under organic (without imidacloprid) and conventional (with imidacloprid) agricultural practices. A total of 1164 VOCs, representing 23 chemical classes (e.g., aldehydes, terpenes, and furanone compounds), were detected, which is the highest number of VOCs that have ever been detected in strawberries. The sensory evaluation results indicated that there was a notable influence of imidacloprid (IMI) on the aroma of the strawberries. Principal component analysis and partial least squares discriminant analysis results suggested that the composition of volatile compounds significantly differed in the present study between the IMI-treated and non-IMI-treated groups. Furthermore, the flavor-related indicators of 25 key contributors to the differences between the two treatment groups suggested that VOC profiles can be considered an indicator for distinguishing between strawberries from different agricultural practices. Flavoromics can provide new insights into the quality of strawberries from different agricultural practices.

Ferrihydrite (Fh) is an important iron mineral in paddy soil and is prone to phase transition during dynamic redox condition, which affects Cd distribution and induces Cd isotope fractionation across soil to rice. Here, we conducted rice culture experiments with or not Fh application under different irrigation regimes to study the relationship between Fe species and Cd availability, as well as the isotope ratio of Cd in different Cd pools in paddy soil-rice system. Fh addition under continuous flooding (FL) with the decrease of pe + pH from 9.36 to 3.44 promoted the formation of amorphous Fe oxides as increased by 120.1% and facilitated Cd immobilization along with the increase of Fe/Mn oxides bound Cd by 25.3%, compared with continuous drying (DY) treatment. The isotopically heavy Cd were preferentially enriched from soil to extractable Cd (Δ114/110Cdextractable Cd-soil = 0.39-0.62‰) and from soil to grain (Δ114/110Cdgrain-soil = 0.40-0.66‰) particularly at low pe + pH and with Fh addition, while light Cd were enriched in Fe/Mn oxides (Δ114/110CdFe/Mn oxides bound Cd-extractable Cd = -0.65 ∼ -0.14‰). Besides, the expression of transporters involved in Cd transport in rice like OsNRAMP1, OsNRAMP1, OsHMA3, OsHMA2 and OsLCT1 were suppressed under low pe + pH condition. These findings indicated that low pe + pH facilitated Cd stabilization by the existence of more amorphous iron oxides, which induced the enrichment of heavy Cd isotope in liquid phase and light in Fe/Mn (oxy)hydroxides, respectively.

In order to explore the environmental behavior of organophosphate esters (OPEs) in aquatic environment, the accumulation and distribution of OPEs in water, sediment, and plant were investigated. In this study, watermifoil ( Myriophyllum aquaticum ) were exposed with ten OPEs for concentrations of 200 ng/g, 500 ng/g, 1000 ng/g, and 2000 ng/g, respectively. The concentrations of Σ 10 OPEs in rhizosphere sediment were higher than those in non-rhizosphere sediment, demonstrating that rhizosphere processes tend to transport OPEs into the rhizosphere sediment. Most of the selected OPEs were not in equilibrium between water and sediment, and trend to retain in sediment. In addition, OPEs with relatively higher hydrophobicity had trend to retained in Myriophyllum aquaticum roots, whereas OPEs with lower hydrophobicity were more likely transported to shoots. In this study, octanol-water partition coefficient ( K OW ) had significantly positive correlations with organic carbon-normalized soil-water partition coefficients ( K OC ) and root-water concentration factors (RWCFs), but K OW was negatively correlated with translocation factors (TFs). Moreover, the substituent types and initial levels of OPEs also have impacts on the plant uptake and accumulation. These observations will improve our understanding of the distribution and translocation of OPEs in aquatic environment.