As the main component of electronic products, plastics contain complex and diverse metal additives. Recycling process is not conducive to stable existence of metal additives in electronic plastics. Once the e-waste plastics enter the environment, they will continue to release harmful metals into environment after aging, causing serious hazards. This study delved into the analysis and comparison of metal content of e-waste plastics, elucidating aging process and metal leaching behavior over a 112-day natural light exposure period. The findings underscored that metal content in recycled plastics surpassed that in their new counterparts. Specifically, Ti content in new plastics remained below 100 mg/kg, while recycled plastics exhibited Ti content surpassing 100 mg/kg threshold. Throughout prolonged natural light exposure, metals such as Zn, Ba and Sb demonstrated a heightened likelihood of release from electronic plastics in comparison to other metals. The aging process during light exposure led to fragmentation of electronic plastics, accompanied by a reduction in particle size. Notably, the particle size reduction was more pronounced in poly acrylonitrile butadiene styrene (ABS) and recycled ABS, experiencing reductions of 40 pm and 85 pm, respectively. This phenomenon was attributed to the presence of polybutadiene structural units, which proved more susceptible to aging. Along with the breaking of plastics, the ABS plastics released metal species such as Pb, Cd, Ni, Al that had not been detected in other plastics solutions. The collective evidence from this study suggested that ABS and recycled ABS electronic plastics might pose a heightened potential environmental risk compared to other electronic plastics. (c) 2025 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Microplastics (MPs) serve as unconventional platforms for microorganisms and vectors for pollutants and pathogens in aquatic ecosystems. This study explored the dynamics of microbial colonization and biofilm formation on MPs, a key factor in their ecological impact, using five common MP types-poly(ethylene terephthalate) (PET), poly(vinyl chloride) (PVC), polyethylene (PE), polylactic acid (PLA), and polypropylene (PP)-incubated in an aquaculture pond for 128 days. The biofilm biomass increased by 173-617% compared with original samples, especially PP- and PE-MPs (OD 595 nm = 0.30 and 0.28, respectively). Driven by the inherent properties of MPs, biofilm biomass and microbial community structure differed significantly across the MP types, leading to varied changes in hydrophobicity and surface morphology. Differences in physicochemical properties cause each MP type to selectively enrich specific microbes, profoundly influencing biofilm formation and MP degradation potential. Notably, PP- and PE-MPs supported rich, mature biofilms conducive to carbon cycling and biofilm development, while PET-MPs attracted more abundant plastic degraders, like Pseudomonas. The study also highlighted the enrichment of pathogens on MPs, indicating potential environmental and human health risk. These findings illuminate the complex interactions between MP characteristics and biofilm dynamics, enhancing understanding of MPs' environmental behaviors and fates in aquatic settings.

To reveal the feedbacks and regulating mechanisms of microplastic types and doses on microbial community, a microcosm experiment was carried out with two non -degradable microplastics [polyethylene (PE) and polyvinyl chloride (PVC)] and four biodegradable microplastics [poly(butylene succinate) (PBS), polyhydroxyalkanoates (PHA), poly(butyleneadipate-co-terephthalate) (PBAT), and polypropylene carbonate (PPC)] at different levels (1 %, 7 %, and 28 %). As a result, the content of total carbon (TC), soil organic carbon (SOC), and microbial biomass carbon (MBC) (expect MBC in PBS soil) increased with increasing doses of microplastics, and increased at the lowest PE dose rate. Biodegradable microplastics created a more active ecological niche while enriching more pathogens than non -degradable microplastics. Structural equation modeling indicated that microbial diversities were in a type -dependent assembly, whereas microbial compositions were more profoundly affected by the microplastic doses, ultimately. The standardized total effect coefficient of microplastic types on bacterial and fungal diversities was - 0.429 and - 0.282, and that of doses on bacterial and fungal compositions was 0.487 and 0.336, respectively. Both microplastic types and doses significantly impacted pH, electrical conductivity, total nitrogen, TC, SOC, and MBC, subsequently inhibiting microbial diversities and stimulating microbial compositions with particular pathways. The results provide a comprehensive understanding for evaluating the potential risk of microplastics.

Large areas of arable lands in China have been contaminated by heavy metals, in which cadmium (Cd) contamination was the most prevalent. Cd accumulation in main food crops and leafy vegetables grown in Cd-contaminated fields has aroused considerable attention in recent years. The present study investigated the Cd pollution of farmland soils and vegetables in Qujing city of Yunnan Province, China. By comparing the Cd uptake capacities of different crops, this study aimed to provide guidance for agricultural production in Cd-contaminated farmland, and clarify the influence of Cd bioavailability in soil and chemical forms of Cd in plant roots on its migration. Results showed that soil Cd concentration was up to 37 mg kg−1, which was 61-fold higher than the soil environmental quality standard in China. Concentration of Cd in 73% of the investigated vegetable samples, with the mean value of 5.43 mg Cd kg−1 (dry weight basis), exceeded the food safety standard of China. Leafy vegetables had the highest bioaccumulation factors (BF) and transfer factors (TF), with the mean values of 0.53 and 0.41, respectively. Water spinach (Ipomoea aquatica Forsk.), cole (Brassica campestris L.), and fennel (Foeniculum dulce Mill.) had the highest Cd TFs, with averages of 0.67, 0.66, and 0.64, respectively. On the contrary, garlic (Allium sativum L.), onions (Allium fistulosum L.), and pea (Lathyrus odoratus L.) had the lowest Cd TFs, with averages of 0.04, 0.03, and 0.04, respectively. The main chemical fraction of Cd in garlic root was insoluble phosphate (35–48%), whereas in water spinach root, it was pectate, protein binding or sorbed fraction (50–64%), resulting in a higher TF value of water spinach than garlic. These results indicate that there were significant differences in Cd uptake and accumulation between vegetables, and the Cd accumulation in leafy vegetable was significantly higher than that in alliums. Therefore, it is possible to reduce the uptake and accumulation of Cd in crop edible parts by the selection of vegetable species with low Cd accumulation capacity. The chemical fractions of Cd in crop roots, especially the proportions of more mobile fractions, might be an important reason for the root-to-shoot Cd transport and Cd accumulation in the aerial portions.

Background and aims Water spinach readily uptakes cadmium (Cd), posing a risk to human health. Selecting low-Cd cultivars is a promising mitigation strategy, but its extensive utilization is limited without a clear understanding of the critical plant factors determining Cd accumulation. This study aimed to elucidate the effects and interactions of the radial oxygen loss (ROL) and iron (Fe) plaque on the Cd accumulation in different water spinach cultivars and the underlying mechanisms. Methods A pot and four hydroponic experiments using ten water spinach cultivars were conducted with different aeration, Fe supply, and Cd stress treatments. Results The Cd accumulation of different cultivars was determined by both root uptake and root-to-shoot transport. There were 4.0-, 3.8- and 6.3-fold differences among different cultivars in ROL, Fe plaque, and shoot Cd accumulation, respectively. Rhizosphere and root Fe plaque reduced root Cd uptake and were regulated by Fe supply and ROL. Increased ROL under stagnant conditions enhanced Fe plaque and induced its redistribution along root axes. Root Cd retention through compartmentalization and chelation inhibited root-to-shoot Cd translocation. Conclusion The Fe plaque, ROL, and root Cd retention formed an interactive system to decrease the Cd uptake and accumulation in water spinach. Low-Cd cultivars exhibited higher ROL, greater Fe plaque and more effective root Cd retention, and responded to stagnant conditions with greater ROL increases and more enhanced Fe deposition on root surfaces. This study provides new insights into the Cd accumulation mechanisms in water spinach and a theoretical basis for selecting low-Cd cultivars.

Using low Cd accumulation cultivars and managing field water regimes are effective measures to mitigate Cd accumulations in rice grains. However, the effect of the cultivar-water condition interaction (CWI) on grain Cd accumulations has largely been ignored. To solve this problem, pot and hydroponic experiments were conducted using 14 rice cultivars and two contrasting water conditions. The results showed that CWI significantly affected Cd concentrations in rice grains and roots, explaining 8.8% and 22.8% of the total variance, respectively. These CWI effects were derived from cultivar-dependent variations in rhizosphere soil properties [Eh, pH and available Cd associated with root radial oxygen loss (ROL)] and root Cd uptake. In this context, cultivar HH61 exhibited low, stable Cd accumulations, owing to its stably lower translocation rate, root Cd uptake ability and available Cd in its rhizosphere than the other cultivars, which was induced by its lower ROL. Root-to-grain Cd translocation rates were vital in determining Cd accumulations in grain of different cultivars but were independent from CWI. These results indicated that CWI could play an important role in Cd accumulation in rice while stable low-Cd cultivar should possess low ROL under flooding and low root-to-grain Cd translocation rate. The results will provide novel theoretical basis for cultivar selection and hence benefit the extensive use of low-accumulation cultivars and public health.

Fly ash and steel slag can potentially mitigate the cadmium (Cd) and arsenic (As) accumulation in rice grains but their long-term effectiveness and impact on soil health are unclear. By running a four-crop-season field trial, we found that the concentrations of Cd, As and inorganic As in rice grains were significantly reduced by steel slag and (consecutively applied) fly ash. For both amendments, decreased soil extractable Cd by increased pH was crucial in reducing grain Cd, but soil re-acidification diminished their effects. Increased soil extractable silicon played a key role in alleviating grain As accumulation. Steel slag had a more persistent effect on reducing grain Cd than fly ash but the sustainability of their effects on reducing grain As depended on rice cultivars. Steel slag improved soil fertility by increasing soil calcium, magnesium, manganese and zinc but chromium and nickel were also increased; it also enhanced the activities of soil urease and alkaline phosphatase, shifted soil bacterial community composition, and increased bacterial diversity. Fly ash had little effect on soil health. Our results indicated that steel slag had positive and sustainable effects on mitigating grain Cd and As accumulation but its potential negative impact on soil health requires in-depth monitoring.

有色金属矿在开采和冶炼的过程中会产生大量的尾矿渣和酸性矿山废水,后者被中和沉淀后成为中和渣.大量堆存的尾矿和中和渣会产生严重的安全和环境问题,亟需有效方法将其安全地处置或回收再利用.研究认为中和渣可以替代土壤作为植物的种植基质,进而缓解尾矿复垦中表土缺乏的困境,但该策略的可行性和安全性尚未经过系统的论证.本研究以紫金山铜矿堆浸废石边坡为对象,评估以中和渣替代自然土壤进行植被复垦的可行性,识别复垦过程中可能存在的限制植物生长的关键环境因子,分析中和渣中毒性重(类)金属元素的状况,比较不同种植方式和坡位对复垦效果的影响.结果表明,有机肥改良后的中和渣土壤氮、磷和钾的总量相对较好,孔隙度、容重和含水率和盐度持续改善.但其有机质总量的偏低,以及有机养分矿化速率较慢所导致的无机氮和有效磷的缺乏,很可能是限制植物生长的关键因素.中和渣所含重金属总量普遍保持稳定,产生二次的污染风险较小.相比机喷处理,人工穴播处理下的中和渣具有更好的养分条件和微生物多样性,但有pH下降和铜、铁和锰等重金属的有效性上升的趋势.本研究的结果表明,以中和渣作为土壤基质进行尾矿复垦是相对安全可行的,但仍需长期关注其pH的变化,并适当增加有机质的添加量和利用微生物菌剂促进其中养分的矿化.

The heterogeneity of arsenic (As) and cadmium (Cd) in paddy soils seriously hinders the assessment of contamination status and prediction of rice uptake. Their vertical patterns across different environmental conditions and the underlying mechanisms remain largely unexplored. In this study, maximum vertical differences of bioavailable As and Cd within 0-30 cm depth in paddy soils were 4.1-fold and four orders of magnitude, respectively. The vertical patterns of As and Cd followed the vertical redox gradient in long-term reduced paddies, but were shaped by the vertical pH gradient derived from acidic wastewater irrigation in partly oxidized soils. Iron(III)- and sulfate-reducing bacteria played key roles in the formation of vertical pH gradient and the immobilization of As and Cd by iron (hydr)oxides and sulfides under varied redox conditions. Soil redox and organic matter determined the transition between these two mechanisms via regulating microbial iron(III) and sulfate reduction processes. The work proposes that soil vertical As and Cd patterns directly affect the accumulation of As and Cd in different rice cultivars with different vertical root patterns. This is the first study elucidating the controlling mechanisms governing the vertical As and Cd patterns in paddy fields, providing important references to identify, manage and remediate contaminated paddy fields.

The reclamation of mine waste deposits is often hindered by the scarcity of natural topsoil. Acid mine drainage sludge (AMDS), as a mass-produced waste in metalliferous mines, is a potential topsoil substitute but had not been validated. In this study, a pot experiment with three plant species was conducted to evaluate the capacity of AMDS to support plant growth, buffer acidification, and immobilize heavy metal(loid)s when reclaiming mine waste rocks. Chemical fertilizer and compost chicken manure were applied to AMDS at different rates to explore their effects on plant growth and the physicochemical properties of AMDS. Results showed that all the plants could survive in AMDS even without fertilization. The contents of heavy metal(loid)s in rhizosphere remained almost unchanged over the experimental period, indicating low leachability of revegetated AMDS. Fertilizers enhanced macronutrients and soil enzyme activities, leading to significant increases in plant biomass. However, owing to manure composting and low richness and diversity of the bacterial community in AMDS, the NH4+-N and bioavailable phosphorus contents were extremely low. Bermuda grass was a suitable pioneer species for reclamation for its better adaptability to nutrient deficiency and heavy metal(loid) stress. Overall, AMDS is a viable soil substitute for mine reclamation due to its capability to support plant growth and environmental safety.

Cadmium (Cd) and arsenic (As) contamination in paddy soils poses serious health risks to humans. The accumulation of Cd and As in rice (Oryza sativa L.) depends on their bioavailability, which is affected by soil physicochemical properties and soil microbial activities. However, little is known about the intricate interplay between rice plants and their rhizosphere microbes during the uptake of Cd and As. In this study, different bacterial communities were established by sterilizing paddy soils with γ-radiation. A pot experiment using two paddy soils with different levels of contamination was conducted to explore how the bacterial community composition affects Cd and As accumulation in rice plants. The results showed that the sterilization treatment substantially changed the bacterial composition in the rhizosphere, and significantly increased the grain yield (by 33.5–38.3%). The sterilization treatment resulted in significantly decreased concentrations of Cd (by 18.2–38.7%) and As (by 20.3–36.7%) in the grain, straw, and root of rice plants. The accumulation of Cd and As in rice plants was negatively correlated with the relative abundance of sulfate-reducing bacteria and iron-oxidizing bacteria in the rhizosphere. Other specific taxa associated with the accumulation of Cd and As in rice plants were also identified. Our results suggest that regulating the composition of the rhizosphere bacterial community could simultaneously reduce Cd and As accumulation in rice grain and increase the grain yield. These results would be useful for developing strategies to cultivate safe rice crops in areas contaminated with Cd and As.

In order to help mitigate widespread cadmium (Cd) and arsenic (As) co-contamination in paddy soils in China, screening and breeding of low-accumulating rice (Oryza sativa L.) cultivars (excluders) have been widely adopted. However, the performance of rice cultivars for grain Cd and As accumulation may vary in different growing environments. The inability to identify stable low-accumulating cultivars has largely hindered their application. In this study, 51 rice cultivars were evaluated at four Cd- and As-contaminated paddy sites in two crop seasons in northern Guangdong Province, China. The aim was to investigate the effects of cultivar, environment and their interactions in determining grain Cd and As concentrations, and so to identify stable low-accumulating cultivars. Results showed that environment effects dominated the Cd and As concentrations in rice grains, explaining 87% of the total variations. The crop season played a vital role; compared to early season, grain Cd levels increased and As levels lowered significantly in late season. Large variations in grain Cd, total As, inorganic As concentrations and the percentage of inorganic As were observed between different cultivars. Conventional japonica cultivars exhibited lower Cd levels but higher As levels in the grains than did indica cultivars. The cultivar × environment interaction (CEI) was significant, and its importance was comparable to the cultivar effect. By measuring and interpreting such an interaction, stable Cd and As excluder cultivars were identified based upon the yield, grain Cd and As levels as well as the stabilities of cultivars across the trial environments. Two stable Cd and As co-excluders were found among the hybrid indica cultivars. These results demonstrated that the variations in grain Cd and As concentrations could mainly be attributed to the environment effects and cultivar selection practices should include the analysis of CEI to identify stable low-accumulating rice cultivars.