Legacy of herbicides in water from Hailun City, Northeast China: Occurrence, source, and ecological risk assessment.

Herbicides (HBCs) are extensively used in modern agriculture. However, their potential negative impacts on environmental media have emerged as a significant environmental concern. In this study, we employed positive matrix factorization (PMF) to identify the potential sources of HBCs. Furthermore, we utilized a multi-matrix ecological risk model to assess the risks associated with HBCs in both surface water and groundwater in the black soil region of Northeast China. The findings revealed that the levels of ∑15HBCs in surface water and groundwater ranged from 585.84 to 6466.96 ng/L and 4.80 to 11,774.64 ng/L, respectively. The PMF results indicated that surface runoff and erosion accounted for 50% of the total HBCs in water, serving as the primary sources. All tested HBCs exhibited acute risk values within acceptable levels. The risk index for the ∑15HBCs was categorized as "moderate risk" in 31% of the surface waters and 13% of the groundwaters. However, 4% of the groundwater sampling sites reached the "high risk" level. The chronic risk quotient of ∑15HBCs in surface water and groundwater was 92% and 62% at the "high risk" level, respectively. Interestingly, non-carcinogenic HBCs contributed more significantly to the ecotoxicology of the aquatic system than carcinogenic HBCs. This study provides comprehensive information on the legacy of HBCs in water bodies and emphasizes the potential risks posed by HBCs to aquatic systems. The results obtained from this study could help relevant management authorities in developing and implementing effective regulations to mitigate the ecological and environmental risks associated with HBCs.

Impacts of simulated atmospheric cadmium deposition on the physiological response and cadmium accumulation of Sedum plumbizincicola.

Atmospheric cadmium (Cd) deposition contributes to the accumulation of Cd in the soil-plant system. Sedum plumbizincicola is a Cd and Zn hyperaccumulator commonly used for the phytoremediation of Cd-contaminated soil. However, studies on the effects of atmospheric Cd deposition on the accumulation of Cd and physiological response in S. plumbizincicola are still limited. A Cd solution spraying pot experiment was conducted with S. plumbizincicola at three atmospheric Cd deposition concentrations (4, 8, and 12 mg/L). Each Cd concentration levels was divided into two groups, non-mulching (foliar-root uptake) and mulching (foliar uptake). The soil type used in the experiment was reddish clayey soil collected from a farmland. The results showed that compared with the non-mulching control, the fresh weight of S. plumbizincicola in non-mulching with high atmospheric Cd deposition (12 mg/L) increased by 11.35%. Compared with those in the control group, the malondialdehyde (MDA) content in the non-mulching and mulching S. plumbizincicola groups increased by 0.88-11.06 nmol/L and 0.96-1.32 nmol/L, respectively. Compared with those in the non-Cd-treated control group, the shoot Cd content in the mulching group significantly increased by 11.09-180.51 mg/kg. Under high Cd depositions, the Cd in S. plumbizincicola mainly originated from the air and was stored in the shoots (39.7-158.5%). These findings highlight that the physiological response and Cd accumulation of S. plumbizincicola were mainly affected by high Cd deposition and suggest that atmospheric Cd could directly be absorbed by S. plumbizincicola. The effect of atmospheric deposition on S. plumbizincicola cannot be ignored.

Photoinduced Electron Transfer from Xanthates to Acyl Azoliums: Divergent Ketone Synthesis via N-Heterocyclic Carbene Catalysis.

Considering the prevalence of alcohols and carboxylic acids, their fragment cross-coupling reactions could hold significant implications in organic synthesis. Herein, we report a versatile method for synthesizing a diverse range of ketones from alcohols and carboxylic acid derivatives via N-heterocyclic carbene (NHC) catalysis. Mechanistic investigations revealed that photoexcited xanthates and acyl azoliums undergo single electron transfer (SET) under photocatalyst-free conditions, generating NHC-derived ketyl radicals and alkyl radicals. These open-shell intermediates subsequently undergo the radical-radical cross-coupling reaction, yielding valuable ketones. Furthermore, this approach can be employed in three-component reactions involving alkenes and enynes, resulting in structurally diverse cross-coupled ketones. The unified strategy offers a unique opportunity for the fragment coupling of a diverse range of alcohols and carboxylic acid derivatives, accommodating diverse functional groups even in complex settings.

Site-Selective Pyridine C-H Alkylation with Alcohols and Thiols via Single-Electron Transfer of Frustrated Lewis Pairs.

A unified strategy for the deoxygenative or desulfurative pyridylation of various alcohols and thiols has been developed through a single-electron transfer (SET) process of frustrated Lewis pairs (FLPs) derived from pyridinium salts and PtBu3 . Mechanistic studies revealed that N-amidopyridinium salts serve as effective Lewis acids for the formation of FLPs with PtBu3 , and the generated phosphine radical cation ionically couples with the in situ generated xanthate, eventually affording the alkyl radical through facile ß-scission under photocatalyst-free conditions. The reaction efficiency was further accelerated by visible-light irradiation. This method is conceptually appealing by using encounter complexes in FLP chemistry to promote SET, which provides a previously unrecognized opportunity for the selective heteroarylation of a diverse range of alcohols and thiols with various functional groups, even in complex settings under mild reaction conditions.

Effects of four endophytic bacteria on cadmium speciation and remediation efficiency of Sedum plumbizincicola in farmland soil.

Cadmium (Cd) pollution in farmland soils severely affects agricultural production safety, thereby threatening human health. Sedum plumbizincicola is a Cd and Zn hyperaccumulator commonly used for the phytoremediation of Cd-contaminated soil. This study was aimed to improve the remediation effect of S. plumbizincicola on Cd-contaminated farmland soil and provide a theoretical basis for the enhancement of endophytic bacteria in the repair of Cd-contaminated soil with S. plumbizincicola. Four kinds of endophytic bacteria, namely Buttiauxella, Pedobacter, Aeromonas eucrenophila, and Ralstonia pickettii, were used, and soil culture experiments and pot experiments were conducted to explore the effects of endophytic bacteria on soil Cd speciation and phytoremediation efficiency of Cd-contaminated farmland soils. Under the experimental conditions, after inoculation with endophytic bacteria, the soil pH was effectively reduced, content of weak acid-extracted Cd and oxidizable Cd increased, and content of reducible Cd and residual Cd decreased. Soil Cd activity was increased, and the availability coefficient of soil Cd increased by 1.15 to 6.41 units compared with that of the control (CK2). Compared with CK2, the biomass of S. plumbizincicola significantly increased by 23.23-55.12%; Cd content in shoots and roots of S. plumbizincicola increased by 29.63-46.01% and 11.42-84.47%, respectively; and bioconcentration factor was 2.13 to 2.72 times that of CK2. The Cd removal rate of S. plumbizincicola monocropping was 48.25%. When S. plumbizincicola was planted with inoculating endophytic bacteria, the Cd removal rate in the soil reached 61.18-71.49%, which was significantly higher than that of CK2 (p < 0.05). The treatment with endophytic bacteria activated soil Cd, promoted the growth of S. plumbizincicola, increased its Cd content, and enhanced the phytoremediation of Cd-contaminated farmland soil. Therefore, endophytic bacteria can be used to improve the remediation efficiency of S. plumbizincicola in Cd-contaminated farmland soils.

Occurrence and health risk assessment of phthalate esters in tobacco and soils in tobacco-producing areas of Guizhou province, southwest China.

Flue-cured tobacco is one of the important sources of national economy in China. However, Phthalic acid esters (PAEs) are ubiquitous contaminants in the cultivation and growth management of flue-cured tobacco, and attracting more and more attention. Here, six priority PAEs were detected in tobacco and soils and their residue characteristics, pollution sources were analyzed, and their exposure risks to the health of farmers were assessed. The concentration of six total PAEs ranged from 0.78 to 4.79 mg/kg in tobacco with the average of 1.75 mg/kg, and 0.84-25.68 mg/kg in soils with the average of 5.40 mg/kg. Di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) had the highest detection frequency (DF = 100%) both in soil and tobacco samples. DEHP was the most abundant of the total PAEs in soil and tobacco samples, with the mean contribution values of 71.0% and 58.8%, respectively. Principal component analysis (PCA) indicates that the major sources of PAEs in the tobacco-soil system were plastic films, fertilizers and pesticides. Health risk assessment suggests that the non-cancer hazard indexes (NCHI) of dimethyl phthalate (DMP), diethyl phthalate (DEP), DBP and di-n-octyl phthalate (DnOP) in all samples for farmers were at acceptable levels (NCHI < 1), and the average carcinogenic hazard indexes (CHI) of butyl benzyl phthalate (BBP) and DEHP for farmers were 3.79 × 10-13 and 8.54 × 10-11 in soils, respectively, 8.23 × 10-13 and 1.95 × 10-11 in tobacco, respectively, which were considered to be very low level (CHI < 10-6). This study provides data on PAEs in tobacco and soils and their health risks which may provide valuable information to aid the management of tobacco cultivation and risk avoidance.

One-Pot Enantioselective Construction of Polycyclic Tetrahydroquinoline Scaffolds through Asymmetric Organo/Photoredox Catalysis via Triple-Reaction Sequence.

A novel one-pot triple-reaction strategy for the asymmetric construction of polycyclic skeletons with multiple consecutive chiral centers through aza-Michael/Michael/Wittig/ketyl radical addition/esterification processes is reported. A wide range of polycyclic tetrahydroquinoline derivatives were smoothly obtained from easily available starting materials with good results (up to 80% yield, >20:1 dr, >99% ee) under mild conditions. In this transformation, five chemical bonds and five consecutive chiral centers were successively formed.

[Strengthening the effect of Bacillus megaterium on remediation of Cd-contaminated farmland soil by Sedum plumbizincicola]. / 巨大芽孢杆菌对伴矿景天修复镉污染农田土壤的强化作用.

Sedum plumbizincicola is a Cd and Zn hyperaccumulator, widely used for the phytoremediation of Cd-contaminated soil. Bacillus megaterium, a phosphate-solubilizing bacteria, can promote plant growth and improve the bioavailability of heavy metals in soil, and thus has a strengthening effect on the remediation of heavy metal-contaminated soil. Here, a pot experiment was carried out with S. plumbizincicola as a hyperaccumulator to investigate the effects of different inoculation amounts (10-60 mL) of B. megaterium on the phytoremediation efficiency of Cd-contaminated farmland soils. The results showed that inoculation of B. megaterium increased soil available Cd content by 15.0%-45.0% compared with the CK. Biomass of shoots and roots of S. plumbizincicola increased by 8.7%-66.7% and 13.6%-81.8%, respectively. Shoot Cd concentration was significantly increased by the application of B. megaterium by 29.2%-60.4%. Under the conditions of S. plumbizincicola inoculated with B. megaterium, Cd removal rate of soil reached 26.7%-42.9%. In conclusion, application of B. megaterium in phytoremediation significantly enhanced the Cd removal efficiency and increased plant biomass, which promoted Cd remediation efficiency.

Analysis of the effect of cadmium stress on root exudates of Sedum plumbizincicola based on metabolomics.

Root exudates are the most direct manifestation of the response of plants changes in the external environment. Therefore, based on non-targeted gas chromatography-time-of-flight mass spectrometry and metabolomics, the response of Sedum plumbizincicola root exudates to Cd stress was used to reveal the possible mechanism of resistance to or accumulation of Cd. The results showed that Cd significantly changed the composition and contents of S. plumbizincicola root exudates. A total of 155 metabolites were identified in S. plumbizincicola root exudates, among which 33 showed significant differences under Cd stress, including organic acids, amino acids, lipids, and polyols. Cd stress suppressed organic acid metabolism and lipid metabolism in S. plumbizincicola and significantly affected amino acid metabolism. There were 16 metabolic pathways related to Cd stress, among which arginine and proline metabolism, valine, leucine, and isoleucine biosynthesis, glycine, serine, and threonine metabolism, glutathione metabolism, and purine metabolism were the key pathways with the highest correlation, and were closely related to the stress resistance of S. plumbizincicola.

Asymmetric Organocatalytic [4 + 1] Annulations Involving a Polarity Reversal Process: A Tandem Catalytic Approach to Highly Functionalized Spiropyrazolone Derivatives.

A tandem catalytic strategy for the asymmetric synthesis of spirocyclopentanone pyrazolones bearing three contiguous stereocenters and two quaternary carbons with good stereoselectivities has been developed. This strategy, using pyrazolones as efficient C1 synthons and involving a polarity reversal process, not only overcame the energy barrier of the dearomatization process but also avoided nucleophilic addition of the hydroxy group in the enol form tautomer. Futhermore, spirocyclopentanones could be transformed into spirocyclohexamide pyrazolone with the Lawesson reagent.

Atmospheric deposition of cadmium in an urbanized region and the effect of simulated wet precipitation on the uptake performance of rice.

Excessive inputs of potentially toxic elements (PTEs) into the surface environment as a consequence of atmospheric deposition, imposes long-term burdens on agricultural ecosystems. Studying the spatial and temporal variation in PTEs in atmospheric deposition and their effects on plant shoot accumulation are important in understanding the sources and contributions of PTEs in soils and agricultural products. Here, the spatial and temporal variations in cadmium (Cd) concentration and atmospheric deposition fluxes were investigated in five rice-producing areas of the urbanized Chang-Zhu-Tan region over two years. Then, the effects of simulated wet precipitation on the uptake of Cd in rice seedlings in hydroponic culture was explored. The results showed substantial spatial variability in Cd concentrations and atmospheric deposition fluxes in this region. The Cd concentration of atmospheric deposition ranged from 0.07 to 114 µg L-1, and the annual Cd fluxes in the industrial area reached 61.0 g ha-1 but all were <10.0 g ha-1 in the rural areas. Rice seedling growth became significantly inhibited with increasing concentrations of Cd. Cadmium content in the shoots and white roots and dithionite-citrate-bicarbonate (DCB) extractable Cd on root surfaces were significantly and positively correlated with the concentration of Cd in the nutrient solution. Shoot Cd concentrations increased significantly (p < 0.05) when the annual Cd precipitation flux was ≥50 g ha-1 compared to the control with no Cd precipitation, and the concentration in the shoot was higher than that in roots of rice cultivar A159, when the annual simulated wet precipitation flux of Cd was 400 g ha-1. Thus, shoot Cd was directly related to the simulated wet precipitation when the flux exceeded 50 g ha-1a-1, indicating that air pollution is an important source factor affecting crop Cd uptake.

One-Pot Asymmetric Synthesis of Spiropyrazolone-Linked Cyclopropanes and Benzofurans through a General Michael Addition/Chlorination/Nucleophilic Substitution Sequence.

A sequential and general strategy has been successfully developed for the synthesis of spiropyrazolone scaffolds. This intriguing transformation of the asymmetric multicomponent catalysis process was realized with the combination of Michael addition/chlorination/nucleophilic substitution in a one-pot sequence, giving rise to a series of spiropyrazolones with fully substituted cyclopropanes and spiro-dihydrobenzofurans containing continuous stereogenic centers in good yields with excellent stereoselectivities.

Distribution, contamination and source identification of heavy metals in bed sediments from the lower reaches of the Xiangjiang River in Hunan province, China.

Concentrations of heavy metals Ba, Sc, V, Cr, Mn, Co, Ni, Th, U, Cu, Pb, Zn, and Cd in sediments from the lower reaches of the Xiangjiang River were analyzed using inductively coupled plasma mass spectrometry. The results suggest that there are two metal distribution patterns in these sediments: (1) Ba, Sc, V, Cr, Mn, Th, and U are relatively homogeneously distributed and (2) Cd, Pb, Zn Cu, Co and Ni are heterogeneously distributed. The heterogeneously distributed metals are significantly enriched in these sediments and, thereby, contribute to contamination. Assessments of heavy metal contamination using the Geoaccumulation index, Pollution load index, and potential ecological risk index suggest that the levels of contamination from Cd and Mn are extremely high and moderately high, respectively, in all the sediments from the lower river. In comparison, the levels of contamination by Cu, Zn, and Pb varied spatially, decreasing progressively downriver. The level of contamination by Pb, Zn, and Cu in sediments from the Zhuzhou reach is extremely high, and is moderate to significant high for the Xiangtan, Changsha, and Xiangyin reaches. The ecological potential risks posed heavy metals are ranked, in descending order, as Cd > Pb > Cu > Zn > Cr > Ni > Co > Mn for sediments from the Zhuzhou reach and Cd > Pb > Cu > Ni > Cr > Co > Zn > Mn for sediments from the Xiangtan, Changsha, and Xiangyin reaches. Principal component analysis and enrichment factor calculations suggest that Ba, Sc, V, Cr, Th, and U mostly originate from natural processes. While, Cd, Pb, Zn, Cu, Co, Ni, and Mn are derived from both natural processes and anthropogenic activities. Therefore, strategies for environmental protection in this watershed should focus on contamination by Cd, Pb, Zn, and Cu, with Cd requiring particular attention.

Effect of a novel Ca-Si composite mineral on Cd bioavailability, transport and accumulation in paddy soil-rice system.

Ubiquitous cadmium (Cd) contamination in mine impacted paddy soil has been jeopardizing regional rice quality, which represents a dominant pathway of Cd exposure in populations depending on a rice diet. Two major aspects of mitigation, soil liming and Si fertilization, were integrated and investigated with a Ca-Si-rich composite mineral (CS) derived from feldspar and carbonate. With the CS amendment, bioavailable Cd in rice rhizosphere was reduced by 92-100% from tillering to maturation stage, paralleled by a marked increase in Cd bound to Fe/Mn oxides and carbonate. As indicated by XRD analysis, the much reduced labile pool of Cd in the CS-amended soil could be mainly attributed to Cd (co)precipitation (Cd(OH)2, Cd2(OH)3Cl, CH6Br3CdN) and surface complexation on more negatively charged oxides at elevated soil pH with CS addition. EDX line scan illustrated much more intensified Si deposition along root cross-section in the CS treatment, which resulted in 1.5-2.1-fold higher Cd sequestration in the CS-amended root than control. As a direct result, the root-to-shoots Cd translocation was reduced significantly by 42-51%, while a slightly less significant decrease in brown rice Cd was obtained with the CS treatment relative to control. The CS amendment showed differing effects on brown rice mineral accumulation, with 1.2-1.5-fold increase in brown rice Zn and simultaneously reduced Fe, Mn, Mg and Cu in brown rice. Our results call the readers' attention to the potential impact of soil ameliorator on grain mineral uptake, and we suggest that proper fortification with mineral fertilizers should be supplemented to assist sustainable rice production with improved mineral nutrition.

Participation of ß-Ketothioamides in N-Heterocyclic Carbene-Catalyzed [3 + 3] Spiroannulation: Asymmetric Synthesis of Functionalized Spiro-piperidinone Derivatives.

An N-heterocyclic carbene-catalyzed asymmetric [3 + 3] spiroannulation of ß-ketothioamide was successfully developed. ß-Ketothioamides exhibit an unusual reactivity to undergo a previously challenging lactamization reaction, and the desired spiro-piperidinone derivatives containing two vicinal stereogenic centers were synthesized in good to high yields with high stereoselectivities, whose structure can be converted to the corresponding imide and δ-lactam derivatives smoothly.

Effects of a natural sepiolite bearing material and lime on the immobilization and persistence of cadmium in a contaminated acid agricultural soil.

Soil contamination with cadmium (Cd) represents a substantial threat to human health and environmental quality. Long-term effectiveness and persistence of remediation are two important criteria for the evaluation of amendment techniques used to remediate soils polluted with potentially toxic metals. In the current study, we investigated the remediation persistence of a natural sepiolite bearing material (NSBM, containing 15% sepiolite) and ground limestone (equivalent to > 98.0% CaO) on soil pH, Cd bioavailability, and Cd accumulation by pak choi (Brassica chinensis L.) during the growth of four consecutive crops in a Cd-contaminated acid soil with different amounts of NSBM (0, 0.2, 0.5, 1, 2, and 5%). Soil pH levels ranged from 5.21 to 7.76 during the first crop, 4.30 to 7.34 during the second, 4.23 to 7.80 during the third, and 4.33 to 6.98 during the fourth, and increased significantly with increasing the application rate of NSBM. Soil CaCl2-Cd and shoot Cd concentrations decreased by 8.11 to 99.2% and 6.58 to 94.5%, respectively, compared with the control throughout the four cropping seasons. A significant negative correlation was found between soil CaCl2-Cd and soil pH. Combined use of 0.1% lime and NSBM showed greater effects than NSBM alone, especially, when the application rate of NSBM was ˂ 2%. Moreover, pak choi tissue Cd concentrations in the treatments with NSBM addition alone at ≥ 2% or at ≥ 1% NSBM combined with 0.1% lime met the maximum permissible concentration (MPC) over the four crops, allowed by the Chinese and European regulations. Based on the present study, safe crop production in the test soil is possible at a soil pH > 6.38 and CaCl2-Cd < 14 µg kg-1, and soil Cd immobilization by NSBM without or with lime is a potentially feasible method of controlling the transfer of soil Cd into the food chain.

Effectiveness and potential risk of CaO application in Cd-contaminated paddy soil.

In this study, the accurate effectiveness of CaO in mitigating Cd bioavailability in paddy soil-rice system was investigated and moreover, the potential for reversibility of CaO liming process was provided. Increasing soil pH to ≥6.5 by CaO was determined to be the minimal threshold for minimizing Cd transfer into rice in historically contaminated soils across light to severe Cd levels, while an elevated CaO ratio was needed for soil with recent input of Cd. In CaO remediation treatment, a reduced pool of bioavailable Cd in rhizosphere soil coupled with an increased Cd retention by Fe plaque and an inhibited planta Cd transfer was determined consistently and proposed to be largely responsible for the significant reduction in brown rice Cd. Under continuous simulated acid precipitation test, a negligible level of Cd in eluate with ∼1 unit higher pH than control was recorded with CaO. Significant acidification, however, increased Cd solubilization in the limed soil than in unlimited control, notably at pH 5.5-6.5. As indicated by Visual MINTEQ, a higher Cd-carbonate solubility and much decreased Cd complexation on Fe-(hydr)-oxides across this pH range occurred as a result of elevated Ca input. This suggests that a high soil pH (≥6.5) needs to be permanently maintained once liming has been performed to minimize Cd mobilization. Therefore, amending Cd-contaminated soils with CaO is a cost-effective remedial measure for reducing Cd bioavailability to paddy rice, while a high soil pH need to be permanently maintained to sustain this beneficial effect.

Effect of biochar and Fe-biochar on Cd and As mobility and transfer in soil-rice system.

In this study, the effects of biochar derived from rice-straw (biochar) and iron-impregnated biochar (Fe-biochar) on Cd and As mobility in rice rhizosphere and transfer from soil to rice were investigated with different application rates. 1-3% biochar reduced porewater Cd in rhizosphere but elevated soluble As, resulting in 49-68% and 26-49% reduction in the root and grain Cd, with a simultaneous increase in root As. Unlike biochar, 0.5% Fe-biochar decreased porewater As throughout rice growth, resulting in reduced root As, which, however, increased Cd uptake by root. Biochar-induced soil As mobilization was probably through competitive desorption and Fe-biochar-induced soil Cd mobilization was probably via soil acidification. The results suggested that biochar and Fe-biochar was effective in reducing Cd and As uptake by rice, respectively, so they may be used as emergency measures to cope with single Cd or As contamination in paddy soils.

Phosphate reclaim from simulated and real eutrophic water by magnetic biochar derived from water hyacinth.

In this study, the efficiency and mechanism of aqueous phosphate removal by magnetic biochar derived from water hyacinth (MW) were investigated. The MW pyrolyzed at 450 °C (MW450) exhibited the most prominent phosphate sorption capacity, which was estimated to be 5.07 mg g-1 based on Langmuir-Freundlich model. At an initial phosphorus (P) concentration of 1 mg l-1, >90% P removal was achieved over pH 3-9, but the efficiency decreased sharply at pH > 10. The presence of arsenate and carbonate could remarkably decrease P sorption, while the inhibition effects of antimonate, nitrate and sulfate were less significant. In further application of MW450 to reclaim P from eutrophic lake waters (0.71-0.94 mg l-1 total P), ∼96% P removals were attained in the batch studies and the effluent P concentrations in the column tests were reduced to <0.05 mg l-1 within 509-1019 empty bed volumes. As indicated by XRD, MW450 surface was dominated by Fe3O4 and Fe2O3, resulting in a good ferromagnetic property of this composite (saturation magnetization 45.8 emu g-1). Based on XPS, P sorption onto MW450 occurred mainly by surface complexation with the hydroxyl via ligand exchange. These results highlighted that MW derived from highly damaging water hyacinth could provide a promising alternative for P removal from most eutrophic waters.

Varying effect of biochar on Cd, Pb and As mobility in a multi-metal contaminated paddy soil.

Cd, Pb and As stand as the most prominent contaminants prevailing in Chinese soils. In the present study, biochars derived from water hyacinth (BCW) and rice straw (BCR) were investigated regarding their applicability and durability in soil Cd, Pb, and As immobilization under acid precipitation. Total Cd, Pb, and As in both BCs were below the maximum allowed threshold according to biochar toxicity standard recommended by International Biochar Initiative. To evaluate BCs effect on Cd, Pb, As bioavailability and mobility, CaCl2, KH2PO4 and SPLP extractions were firstly carried out. In neutral extraction with CaCl2 and KH2PO4, significantly reduced Cd/Pb concentrations in CaCl2 extract along with elevated KH2PO4-extractable As were recorded with either BC at 2% or 5%. In SPLP with simulated acid rainwater as extractant, comparable Cd, Pb and As levels were determined in SPLP extract with 2% BCW, while slight to significant increase in SPLP-Cd, Pb or As was recorded with other treatments. Longer-term leaching column test further confirmed the high durability of 2% BCW in Cd immobilization under continuous acid exposure. In parallel, little increase in As concentrations in eluate was determined with 2% BCW compared to no-biochar control, indicating a lowered risk of As mobilization with acid input. However, remarkably higher Pb in leachate from both BCW-only control and 2% BCW-amended soils were noticed at the initial stage of acid leaching, indicating a higher acid-solubility of Pb minerals in BCW (most probably PbO) than in tested soil (PbO2, PbAs2O6). Taken together, BCW exhibited important potential for soil Cd sequestration with little effect on As mobilization under acid precipitation. But it may simultaneously load highly acid-soluble Pb minerals into soils, resulting in elevated Pb mobility upon acid exposure. Therefore, more stringent threshold for Pb content in biochar need to be put forward to secure biochar application in soils subject to anthropogenic acidification.