Long-term effects of intensive application of manure on heavy metal pollution risk in protected-field vegetable production

Recent advances in phyto-combined remediation of heavy metal pollution in soil

The global industrialization and modernization have witnessed a rapid progress made in agricultural production, along with the issue of soil heavy metal (HM) pollution, which has posed severe threats to soil quality, crop yield, and human health. Phytoremediation, as an alternative to physical and chemical methods, offers a more cost-effective, eco-friendly, and aesthetically appealing means for in-situ remediation. Despite its advantages, traditional phytoremediation faces challenges, including variable soil physicochemical properties, the bioavailability of HMs, and the slow growth and limited biomass of plants used for remediation. This study presents a critical overview of the predominant plant-based HM remediation strategies. It expounds upon the mechanisms of plant absorption, translocation, accumulation, and detoxification of HMs. Moreover, the advancements and practical applications of phyto-combined remediation strategies, such as the addition of exogenous substances, genetic modification of plants, enhancement by rhizosphere microorganisms, and intensification of agricultural technologies, are synthesized. In addition, this paper also emphasizes the economic and practical feasibility of some strategies, proposing solutions to extant challenges in traditional phytoremediation. It advocates for the development of cost-effective, minimally polluting, and biocompatible exogenous substances, along with the careful selection and application of hyperaccumulating plants. We further delineate specific future research avenues, such as refining genetic engineering techniques to avoid adverse impacts on plant growth and the ecosystem, and tailoring phyto-combined strategies to diverse soil types and HM pollutants. These proposed directions aim to enhance the practical application of phytoremediation and its integration into a broader remediation framework, thereby addressing the urgent need for sustainable soil decontamination and protection of ecological and human health.

Quantifying the mitigating effect of organic matter on heavy metal availability in soils with different manure applications: A geochemical modelling study

Manure is one of the main sources of heavy metal (HM) pollution on farmlands. It has become the focus of global ecological research because of its potential threat to human health and the sustainability of food systems. Soil pH and organic matter are improved by manure and play pivotal roles in determining soil HM behavior. Geochemical modeling has been widely used to assess and predict the behavior of soil HMs; however, there remains a research gap in manure applications. In this study, a geochemical model (LeachXS) coupled with a pH-dependent leaching test with continuously simulations over a broad pH range was used to determine the effects and pollution risks of pig or cattle manure separate application on soil HMs distribution. Both pig and cattle manure applications led to soil pH reduction in alkaline soils and increased organic matter content. Pig manure application resulted in a potential 90.5-156.0 % increase in soil HM content. Cattle manure did not cause significant HM contamination. The leaching trend of soil HMs across treatments exhibited a V-shaped change, with the lowest concentration at pH = 7, gradually increasing toward strong acids and bases. The dissolved organic matter-bound HM content directly increased the HM availability, especially for Cu (up to 8.4 %) after pig manure application. However, more HMs (Cr, Cu, Zn, Ni) were in the particulate organic matter-bound state than in other solid phases (e.g., Fe-Al(hydr) oxides, clay minerals), which inhibited the HMs leaching by more than 19.3 % after cattle manure application. Despite these variations, high HM concentrations introduced by pig manure raised the soil contamination risk, potentially exceeding 40 times at pH ±1. When manure is returned to the field, reducing its HM content and mitigating possible pollution is necessary to realize the healthy and sustainable development of circular agriculture.

Treatment of anaerobically digested pig manure by applying membrane processes for nutrient recovery and antibiotics removal

A combination of membrane processes was applied to treat the digestate produced after the anaerobic treatment of pig manure in a biogas plant, aiming towards the recovery of nutrients and effective water treatment for potential reuse. Initially, coarse filtration (sieving and microfiltration) was used to remove particles larger than 1 µm, followed by ultrafiltration, to reduce the suspended solids concentrations below 1 g/L. Subsequently, selective electrodialysis is employed to recover the main nutrient ions, primarily ammonium and potassium. The ion-depleted digestate is then fed to a reverse osmosis unit, where clean water was recovered, yielding a by-product (concentrate) stream enriched in phosphates and organics content. The presence of antibiotics and the concentrations of heavy metals were monitored during all treatment stages to assess their behavior/removal in the various membrane processes. The results indicate that almost 51% of the digestate could be recovered as water free from ions and antibiotics, suitable for reuse in the biogas plant for process needs and irrigation purposes. The selective electrodialysis process can recover 51% of initial NH4+ content (corresponding to 96% of the electrodialysis feed), while the remainder largely ended up in the ultrafiltration concentrate. A similar behavior was observed for the case of K+, while approximately 68% of the phosphates content was retained by the coarse filtration process, with another 24% remaining in the ultrafiltration concentrate and the remaining 8% in the reverse osmosis concentrate. Most of the antibiotics and heavy metals were retained by the coarse and ultrafiltration steps, with smaller amounts detected in the reverse osmosis concentrate.

Comparative Study of Heavy Metal Blood Serum Level Between Organic and Conventional Farmers in Eastern Taiwan

Numerous studies have indicated that organic fertilizers (OFer) might contain heavy metals (HMs) that present health risks to organic farmers (OFar). This study compared the concentrations of six HMs (Zn, Ni, Cd, Cu, Pb, Cr) in the blood of two distinct groups of farmers: 30 OFar from a designated organic area in eastern Taiwan, and 74 conventional farmers (CFar) from neighboring non-organic designated regions. The findings revealed that the OFar exhibited higher levels of Zn (1202.70 ± 188.74 μg/L), Cr (0.20 ± 0.09 μg/L), and Ni (2.14 ± 1.48 μg/L) in their blood compared to the CFar (988.40 ± 163.16 μg/L, 0.18 ± 0.15 μg/L, and 0.77 ± 1.23 μg/L), respectively. The disparities in Zn, Cr, and Ni levels were measured at 214.3 μg/L, 0.02 μg/L, and 1.37 μg/L, respectively. Furthermore, among the OFar, those who utilized green manures (GM) displayed significantly elevated blood levels of Zn (1279.93 ± 156.30 μg/L), Cr (0.24 ± 0.11 μg/L), and Ni (1.94 ± 1.38 μg/L) compared to individuals who exclusively employed chemical fertilizers (CFer) (975.42 ± 165.35 μg/L, 0.19 ± 0.16 μg/L, and 0.74 ± 1.20 μg/L), respectively. The differences in Zn, Cr, and Ni levels were measured at 304.51 μg/L, 0.05 μg/L, and 1.20 μg/L, respectively. As a result, OFar should be careful in choosing OFer and avoid those that may have heavy metal contamination.

Amino acid application inhibits root-to-shoot cadmium translocation in Chinese cabbage by modulating pectin methyl-esterification

The exogenous application of amino acids (AAs) generally alleviates cadmium (Cd) toxicity in plants by altering their subcellular distribution. However, the physiological mechanisms underlying AA-mediated cell wall (CW) sequestration of Cd in Chinese cabbage remain unclear. Using two genotypes of Chinses cabbage, Jingcui 60 (Cd-tolerant) and 16-7 (Cd-sensitive), we characterized the root structure, subcellular distribution of Cd, CW component, and related gene expression under the Cd stress. Cysteine (Cys) supplementation led to a reduction in the Cd concentration in the shoots of Jingcui 60 and 16-7 by 65.09 % and 64.03 %, respectively. Addition of Cys alleviated leaf chlorosis in both cultivars by increasing Cd chelation in the root CW and reducing its distribution in the cytoplasm and organelles. We further demonstrated that Cys supplementation mediated the downregulation of PMEI1 expression and improving the activity of pectin methyl-esterase (PME) by 17.98 % and 25.52 % in both cultivars, respectively, compared to the Cd treatment, resulting in an approximate 12.00 %-14.70 % increase in Cd retention in pectin. In contrast, threonine (Thr) application did not significantly alter Cd distribution in the shoots of either cultivar. Taken together, our results suggest that Cys application reduces Cd root-to-shoot translocation by increasing Cd sequestration in the root CW through the downregulation of pectin methyl-esterification.

Health Risk Assessment of Lead, Cadmium, and Arsenic in Leafy Vegetables in Tehran, Iran: the Concentration Data Study

Absorption of heavy and toxic metals causes their accumulation in the edible parts of vegetables. Pollutants such as heavy metals have directly affected the health of society and contributed to emerging diseases in recent years. The current study aimed to detect heavy metals (Pb, Cd, As) in highly consumed leafy vegetables provided from the Tehran market. Four types of vegetables, including dill, parsley, cress, and coriander were selected and 64 samples were randomly collected from fruit and vegetable markets in different regions of Tehran in August and September 2022. Then, samples were analyzed by the ICP-OES system, and health risk assessment was conducted using non-carcinogenic and carcinogenic approach. The range of Pb concentration was 54-314, < LOQ-289, < LOQ-230, and < LOQ-183 μg/kg for dill, cress, parsley, and coriander, respectively. The high mean concentrations of Pb belong to the dill (161.43 ± 77.3 μg/kg) and cress (154.75 ± 72.9 μg/kg). In some samples of dill (37.5% of samples), cress (18.75% of samples), and parsley (12.5% of samples), the Pb content was above the national allowable limit (200 μg/kg). The range of Cd concentration was < LOQ-42, < LOQ-41, < LOQ-30, and < LOQ-38 μg/kg for dill, cress, parsley, and coriander, respectively. In none of the samples, the concentration of Cd was higher than the Iranian national limit (50 μg/kg). The As occurrence was observed in all cress samples with a mean of 165.19 ± 64.83 μg/kg. The range of As concentration was < LOQ-71, < LOQ-256, 58-273, and < LOQ-75 μg/kg for parsley, dill, cress, and coriander, respectively. The THQ and HI values were higher than 1, and either ILCR value was higher than 10-4 for all tested heavy metals, it can be concluded that higher levels of heavy metals than the standard limits in some samples may raise the warning alarm and should come to the attention of the authorities.

Heavy Metals in Agricultural Soils: Sources, Influencing Factors, and Remediation Strategies

Soil heavy metal pollution is a global environmental challenge, posing significant threats to eco-environment, agricultural development, and human health. In recent years, advanced and effective remediation strategies for heavy metal-contaminated soils have developed rapidly, and a systematical summarization of this progress is important. In this review paper, first, the anthropogenic sources of heavy metals in agricultural soils, including atmospheric deposition, animal manure, mineral fertilizers, and pesticides, are summarized. Second, the accumulation of heavy metals in crops as influenced by the plant characteristics and soil factors is analyzed. Then, the reducing strategies, including low-metal cultivar selection/breeding, physiological blocking, water management, and soil amendment are evaluated. Finally, the phytoremediation in terms of remediation efficiency and applicability is discussed. Therefore, this review provides helpful guidance for better selection and development of the control/remediation technologies for heavy metal-contaminated agricultural soils.

Accumulation, migration and health risk of trace metals in a soil-strawberry-human system of the Yangtze River Delta region, China

Growing concern has been paid to metals in soil-strawberry system. In contrast, few attempts have been made to investigate bioaccessible metals in strawberries and further assess health risk based on bioaccessible metals. Moreover, the connections between soil parameters (e.g. soil pH, organic matter (OM), total and bioavailable metals) and metal transfer in soil-strawberry-human system still need to be systematically investigated as well. Considering that strawberries are extensively grown under plastic-shed conditions in China, a total of 18 paired plastic-shed soil (PSS) and strawberry samples were taken from the strawberry bases located in the Yangtze River Delta of China as a case study to assess accumulation status, migration and health risk of Cd, Cr, Cu, Ni, Pb, and Zn in the PSS-strawberry-human system. Overall, heavy application of organic fertilizers induced accumulation and contamination of Cd and Zn in PSS. In particular, 55.6% and 44.4% of PSS samples had considerable and moderate ecological risk caused by Cd, respectively. Despite no metal pollution in strawberry, PSS acidification mainly caused by high nitrogen input promoted Cd and Zn uptake by strawberry and enhanced bioaccessible concentrations of Cd, Cu, and Ni. In contrast, the increased soil OM caused by organic fertilizer application decreased Zn migration in PSS-strawberry-human system. Additionally, bioaccessible metals in strawberries induced limited non-cancer and cancer risk. To mitigate accumulation of Cd and Zn in PSS and metal transfer in the food chain, feasible fertilization strategies should be developed and carried out.

Post-consumption waterpipe tobacco waste as an unrecognized source of toxic metal(loid)s leachates into aquatic environments

Waterpipe is a common form of tobacco smoking, and recently, its use has been increasing globally. Therefore, concern arises regarding the large quantity of post-consumption waterpipe tobacco waste produced and released into the environment and which can contain high levels of dangerous pollutants such as toxic meta(loid)s. This study reports the concentrations of meta(loid)s in waste from fruit-flavoured and traditional tobacco smoking as well as the release rate of these pollutants from waterpipe tobacco waste into three types of water. These include distilled water, tap water, and seawater and contact times ranging from 15 min to 70 days. The mean concentration levels of Ʃmetal(loid)s in waste samples of Al-mahmoud, Al-Fakher, Mazaya, Al-Ayan brands and traditional tobacco brands were 212 ± 92.8, 198 ± 94.4, 197 ± 75.7, 214 ± 85.8 and 40.6 ± 16.1 μg/g, respectively. The concentration levels of Ʃmetal(loid)s in fruit-flavoured tobacco samples were significantly higher than for traditional tobacco samples (p < 0.05). It was found that waterpipe tobacco wastes leached toxic metal(loid)s into different water samples with similar trends. In addition distribution coefficients showed that most metal(loid)s are highly likely to enter the liquid phase. The concentration levels of these pollutants (except Ni and As) in deionized water and tap water exceeded the surface fresh water standards for sustaining aquatic life during long contact time (up to 70 days). In seawater, concentration levels of Cu and Zn exceeded the recommended standards for maintaining aquatic life in the sea. Therefore, due to the possibility of contamination by soluble metal(loid)s through disposal of waterpipe tobacco waste in wastewater, there is concern that these toxic chemicals might enter the human food chain. Appropriate regulatory measures for disposal of waterpipe tobacco waste are necessary to prevent environmental pollution due to discarded wastes into aquatic ecosystems.

Dynamic characteristics of heavy metal accumulation in agricultural soils after continuous organic fertilizer application: Field-scale monitoring

Manure has been considered as a source of soil heavy metal (HM) pollution. However, the long-term impact of manure application on soil HM accumulation have not been well studied. This study tracked the long-term cumulative trends of soil copper (Cu), zinc (Zn), arsenic (As), and lead (Pb) in three soil-crop systems over 5-8 years' application of commercial manure fertilizer. The contribution of different fertilization treatments (CF, chemical fertilizer; T1-T3, manure with different application dosages) to soil HMs pollution risk were assessed. There are accumulating tendencies for Cu, Zn, and Pb in paddy fields, Cu and As in orchard fields, and Zn, As, and Pb in vegetable fields, while the concentrations of As in paddy fields and Zn in orchard fields decreased over time. Manure application significantly influenced the accumulation of Cu, Zn, and As in soils rather than that of Pb. The modeling prediction subsequently revealed that the time required to reach the risk screening values (Cu: 50 mg kg^-1; Zn: 200 mg kg^-1) for HM content in paddy soil, according to GB15618-2018, decreased from 18.20 years to 7.20 years due to the introduction of Cu and Zn via manure use. Recommend annual manure application dosage was 7.73 t hm^-2 y^-1 to ensure a 20-year period of clean production in paddy soils, while it was 26.15 t hm^-2 y^-1 in the orchard soil and 16.23 t hm^-2 y^-1 in vegetable soil to ensure a 50-year period of clean production, respectively. Overall, the impacts of HMs input by manure application on soil HMs accumulation varied depending on the type of metal and the soil-crop system. The cumulative trends of HMs in soils play a crucial role in determining whether the input of HMs through manure application can lead to the risk of HM pollution.

Remediation of arsenic-contaminated calcareous agricultural soils by iron-oxidizing bacteria combined with organic fertilizer

In arid soil with low-iron and high-calcium carbonate contents, the fate of arsenic (As) is mainly controlled by the contents of calcium and organic matter in the soil. However, there is still a lack of knowledge about their interaction and that effect on their absorption by maize. The purpose of this study was to explore the long-term immobilization and repair mechanism of in situ As-contaminated farmland. We designed three treatments: iron-oxidizing bacteria (FeOB), organic fertilizer, FeOB and organic fertilizer added in combination. After 140-day field farmland remediation trial, the results showed that the FeOB can effectively immobilize the water-soluble As (F_S1) in soil, and the organic fertilizer promoted the remediation of FeOB. In addition, the content of As in maize grains was reduced after treatment by FeOB and organic fertilizer. The XRD and XPS analysis of the topsoil showed that the combined treatment of FeOB and organic fertilizer promoted the formation of calcium arsenate mineral with low solubility and high stability; As(III) would gradually transform into As(V). The biological iron (hydr)oxide can increase the contents of Fe and As in the rhizosphere and form iron plaques on the surface of the roots by SEM-EDS analysis of maize root. Collectively, these results clarify the main biogeochemical ways to control the fate of As in calcareous soils with low-iron and low-organic matter contents and provide a basis for in situ remediation of As.

Source-specific risk assessment for cadmium in wheat and maize: Towards an enrichment model for China

Cadmium (Cd) pollution of agricultural soil is of public concern due to its high potential toxicity and mobility. This study aimed to reveal the risk of Cd accumulation in soil and wheat/maize systems, with a specific focus on the source-specific ecological risk, human health risk and Cd enrichment model. For this we investigated more than 6100 paired soil and grain samples with 216 datasets including soil Cd contents, soil pH and grain Cd contents of 85 sites from China. The results showed that mining activities, sewage irrigation, industrial activities and agricultural practices were the critical factors causing Cd accumulation in wheat and maize cultivated sites. Thereinto, mining activities contributed to a higher Cd accumulation risk in the southwest China and Middle Yellow River regions; sewage irrigation influenced the Cd accumulation in the North China Plain. In addition, the investigated sites were classified into different categories by comparing their soil and grain Cd contents with the Chinese soil screening values and food safety values, respectively. Cd enrichment models were developed to predict the Cd levels in wheat and maize grains. The results showed that the models exhibited a good performance for predicting the grain Cd contents among safe and warning sites of wheat (R² = 0.61 and 0.72, respectively); while the well-fitted model for maize was prone to the overestimated sites (R² = 0.77). This study will provide national viewpoints for the risk assessments and prediction of Cd accumulation in soil and wheat/maize systems.

Covalently Functionalized Cellulose Nanoparticles for Simultaneous Enrichment of Pb(II), Cd(II) and Cu(II) Ions

Cellulose nanoparticles are sustainable natural polymers with excellent application in environmental remediation technology. In this work, we synthesized cellulose nanoparticles and covalently functionalized them with a multi-functional group possessing ligands. The hybrid material shows excellent adsorption properties for the simultaneous extraction of multiple metal ions in the sample preparation technique. The sorbent shows excellent sorption capacity in the range of 1.8-2.2 mmol/g of material. The developed method was successfully employed for the simultaneous extraction of Pb(II), Cd(II) and Cu(II) from real-world samples (industrial effluent, river water, tap and groundwater) and subsequently determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). The method shows a preconcentration limit of 0.7 ppb attributes to analyze the trace concentration of studied metal ions. The detection limit obtained for Pb(II), Cd(II) and Cu(II) is found to be 0.4 ppb.

The different trends in the burden of neurological and mental disorders following dietary transition in China, the USA, and the world: An extension analysis for the Global Burden of Disease Study 2019

Introduction

The highly processed western diet is substituting the low-processed traditional diet in the last decades globally. Increasing research found that a diet with poor quality such as western diet disrupts gut microbiota and increases the susceptibility to various neurological and mental disorders, while a balanced diet regulates gut microbiota and prevents and alleviates the neurological and mental disorders. Yet, there is limited research on the association between the disease burden expanding of neurological and mental disorders with a dietary transition.

Methods

We compared the disability-adjusted life-years (DALYs) trend by age for neurological and mental disorders in China, in the United States of America (USA), and across the world from 1990 to 2019, evaluated the dietary transition in the past 60 years, and analyzed the association between the burden trend of the two disorders with the changes in diet composition and food production.

Results

We identified an age-related upward pattern in disease burden in China. Compared with the USA and the world, the Chinese neurological and mental disorders DALY percent was least in the generation over 75 but rapidly increased in younger generations and surpassed the USA and/or the world in the last decades. The age-related upward pattern in Chinese disease burdens had not only shown in the presence of cardiovascular diseases, neoplasms, and diabetes mellitus but also appeared in the presence of depressive disorders, Parkinson's disease, Alzheimer's disease and other dementias, schizophrenia, headache disorders, anxiety disorders, conduct disorders, autism spectrum disorders, and eating disorders, successively. Additionally, the upward trend was associated with the dramatic dietary transition including a reduction in dietary quality and food production sustainability, during which the younger generation is more affected than the older. Following the increase in total calorie intake, alcohol intake, ratios of animal to vegetal foods, and poultry meat to pulses, the burdens of the above diseases continuously rose. Then, following the rise of the ratios of meat to pulses, eggs to pulses, and pork to pulses, the usage of fertilizers, the farming density of pigs, and the burdens of the above disease except diabetes mellitus were also ever-increasing. Even the usage of pesticides was positively correlated with the burdens of Parkinson's disease, schizophrenia, cardiovascular diseases, and neoplasms. Contrary to China, the corresponding burdens of the USA trended to reduce with the improvements in diet quality and food production sustainability.

Discussion

Our results suggest that improving diet quality and food production sustainability might be a promising way to stop the expanding burdens of neurological and mental disorders.

Manure properties, soil conditions and managerial factors regulate greenhouse vegetable yield with organic fertilizer application across China

To better understand the responses of vegetable yields in a greenhouse system to organic fertilizer through a quantitative evaluation based on peer-reviewed journal articles and in consideration of environmental managerial factors. We conducted a meta-analysis of 453 paired observations from 68 peer-reviewed journal articles to assess the response of vegetable yields in greenhouse vegetable systems in China to organic fertilization. Compared with the control (no organic fertilizer), organic fertilization significantly increased the yields of vegetables by 44.11% on average. The response of vegetable yields to organic fertilizer tended to increase with the increasing experimental duration. Organic fertilizer application had the greatest potential for leafy vegetables (+76.44%), in loamy soils (+53.94%), at moderate organic fertilizer carbon input levels (+54.13%), and in soils with moderate initial soil total nitrogen levels (+50.89%). Aggregated boosted tree analysis indicated that organic fertilizer carbon inputs, vegetable type and experimental duration were the predominant factors that manipulated the response of vegetable yields to organic fertilizer application. The rational application of farmyard manure would be a promising strategy for increasing vegetable yields in greenhouse vegetable systems in China. Factoring in vegetable type, carbon and nitrogen inputs of organic fertilizer, and soil texture would benefit vegetable yields with the application of organic fertilizer.

Source tracing with cadmium isotope and risk assessment of heavy metals in sediment of an urban river, China

The Nanfei River was one of dominant inflowing rivers of the fifth largest freshwater Chaohu Lake in China, which had been subjected to increasing nutrients and contaminants from population expansion, rapid industrialization and agricultural intensification in recent decades. In present study, surface sediment from the Nanfei River was collected to investigate the anthropogenic impact on distribution and bioavailability of heavy metals. Possible Cd sources along the river were constrained by using Cd isotope signatures and labile concentrations of heavy metals in sediment were determined through the DGT technique for risk assessment. Results showed that Cd in river sediment showed greatest enrichment (EF 0.8-9.4), indicating massive pollution from anthropogenic activities. Among the various possible Cd source materials, urban road dust, industrial soil and chicken manure, displayed higher Cd abundance and enrichment that might contribute to Cd accumulation in river sediment. Cadmium isotopic composition in river sediment was ranged from -0.21 ± 0.01‰ to 0.13 ± 0.03‰, whereas yielded relative variation from -0.31 ± 0.02‰ to 0.23 ± 0.01‰ in source materials. Accordingly, Cd sources along the river were constrained, i.e. traffic and industrial activities in the upper and middle reaches whereas agricultural activities in the lower reaches. Furthermore, the evaluation on ecological risk of heavy metals in sediment on basis of SQGs and DGT-labile concentrations demonstrated that Pb and Zn might pose higher risk on aquatic species. The present study confirmed that Cd isotopes were promising source tracer in environmental studies.

Hypothetical scenarios estimating and simulating the fate of antibiotics: Implications for antibiotic environmental pollution caused by manure application

The application of animal manure containing antibiotic residues as an organic fertilizer to farmlands, poses a major threat to the health of river basin ecosystems. Waste treatment processes can help reduce antibiotic pollution levels in river basins following manure application, but the overall influence of these processes remains unclear. This study evaluates the impact of manure treatment methods on the emission and subsequent river pollution caused by 14 frequently detected antibiotics in a typical pig breeding area in China, by using hypothetical scenarios method. Three scenarios were constructed based on possible fate pathways of antibiotics, representing in 47.0, 55.3, and 81.6 ton·yr^-1 antibiotic emissions into the river basin. The soil and water assessment tool (SWAT) model successfully simulated the transport of antibiotics from farmland to surface water, with calibration and verification performed using hydrological station monthly data over 8 consecutive years. Field measured concentrations also verified the reliability of the model and were used to determine the most realistic scenario. In basins applied with manure, environmental antibiotic pollution is most affected by the wastewater treatment process and manure applied patterns, followed by changes in streamflow. The antibiotic pollution in manure applied areas showed significant spatial and temporal differences, resulting from the different manure application patterns. The simulated total outflow of antibiotics in the river basin accounted for 18.1% of the inflow, with the loss of target antibiotics by degradation, volatilization and sedimentation deposition in the river basin being 0.23, 0.01 and 33.2 ton·yr^-1, respectively. This study can help to clarify the environmental fate of antibiotics in the basin following manure application, provide guidance for policy makers and help to design the effective corrective interventions for reducing the environmental pollution.

Cadmium Phytotoxicity, Tolerance, and Advanced Remediation Approaches in Agricultural Soils; A Comprehensive Review

Cadmium (Cd) is a major environmental contaminant due to its widespread industrial use. Cd contamination of soil and water is rather classical but has emerged as a recent problem. Cd toxicity causes a range of damages to plants ranging from germination to yield suppression. Plant physiological functions, i.e., water interactions, essential mineral uptake, and photosynthesis, are also harmed by Cd. Plants have also shown metabolic changes because of Cd exposure either as direct impact on enzymes or other metabolites, or because of its propensity to produce reactive oxygen species, which can induce oxidative stress. In recent years, there has been increased interest in the potential of plants with ability to accumulate or stabilize Cd compounds for bioremediation of Cd pollution. Here, we critically review the chemistry of Cd and its dynamics in soil and the rhizosphere, toxic effects on plant growth, and yield formation. To conserve the environment and resources, chemical/biological remediation processes for Cd and their efficacy have been summarized in this review. Modulation of plant growth regulators such as cytokinins, ethylene, gibberellins, auxins, abscisic acid, polyamines, jasmonic acid, brassinosteroids, and nitric oxide has been highlighted. Development of plant genotypes with restricted Cd uptake and reduced accumulation in edible portions by conventional and marker-assisted breeding are also presented. In this regard, use of molecular techniques including identification of QTLs, CRISPR/Cas9, and functional genomics to enhance the adverse impacts of Cd in plants may be quite helpful. The review's results should aid in the development of novel and suitable solutions for limiting Cd bioavailability and toxicity, as well as the long-term management of Cd-polluted soils, therefore reducing environmental and human health hazards.

Remediation of heavy metal-polluted alkaline vegetable soil using mercapto-grafted palygorskite: effects of field-scale application and soil environmental quality

Remediation materials are the most critical factors for in situ immobilization of soil contaminated by heavy metals. In this study, in order to improve the performance of palygorskite (Pal), a new remediation material, mercapto-grafted palygorskite (MPal) was synthesized by grafting mercapto groups onto the surface of Pal. The results of field application in northern China showed that at a dosage of 0.12-0.23 kg m^-2, MPal significantly reduced the available concentrations of Cd, Pb, and Cr in the soil by 52.2%, 29.9%, and 46.2%, respectively. Concurrently, Cd, Pb, and Cr concentrations in the shoots of head lettuce also decreased significantly, with the highest reduction being 44.0%, 61.5%, and 50.0%, respectively. At the same dosage, MPal had a better immobilization effect than Pal. There was no significant change in the pH of the vegetable soil, while the zeta potential decreased significantly, indicating that the MPal did not immobilize the heavy metals by increasing the pH, making it suitable for alkaline farmland soil. In addition, soil environmental quality was improved overall. MPal increased the activities of urease, β-glucosidase, cellulase, and catalase by 15.4%, 56.5%, 7.8%, and 14.9%, respectively. It increased the number of fungi and actinomycetes by 4.5% and 23.1%, respectively. MPal, as a new remediation material for soil contaminated by heavy metals, could achieve efficient remediation effects when applied in small doses. Compared with Pal, it is environmentally friendly, is low cost, and is more suitable for the treatment of heavy metal pollution in large areas of farmland.

Intrahippocampal Effects of Nickel Injection on the Affective and Cognitive Response in Wistar Rat: Potential Role of Oxidative Stress

The present study focused on affective and cognitive behaviors in male Wistar rats, following direct and unique exposure to nickel chloride (NiCl₂), as well as the possible involvement of oxidative stress. The rats were exposed to NiCl₂ (300 μM), by intracerebral administration of 2 μL of this metal at the right hippocampus, using the stereotaxic approach. Five days after the surgery, a battery of behavioral tests was performed, including the open-field test (OFT) and elevated plus maze test (EPM) to assess the state of anxiety-like behavior and forced swimming test (FST) for depressive-like behavior. Y-maze and Morris Water Maze (MWM) were used to evaluate working memory and spatial learning. Thereafter, oxidative stress markers of the hippocampus were evaluated. The results confirm that NiCl₂ exerts anxiogenic effects in both anxiety tests and depressogenic effects in the FST. In addition, MWM and Y-maze data show that NiCl₂ causes memory and spatial learning disorders. The biochemical assay results showed that intrahippocampal injection of NiCl₂ increased the levels of nitric oxide and lipid peroxidation (p < 0.001), while the activities of catalase and superoxide dismutase were significantly decreased in the hippocampus (p < 0.01). Overall, these results suggest that NiCl₂ causes affective and cognitive disorders and oxidative stress in rats.

Determination of Nutrients in Liquid Manures and Biogas Digestates by Portable Energy-Dispersive X-ray Fluorescence Spectrometry

Knowing the exact nutrient composition of organic fertilizers is a prerequisite for their appropriate application to improve yield and to avoid environmental pollution by over-fertilization. Traditional standard chemical analysis is cost and time-consuming and thus it is unsuitable for a rapid analysis before manure application. As a possible alternative, a handheld X-ray fluorescence (XRF) spectrometer was tested to enable a fast, simultaneous, and on-site analysis of several elements. A set of 62 liquid pig and cattle manures as well as biogas digestates were collected, intensively homogenized and analysed for the macro plant nutrients phosphorus, potassium, magnesium, calcium, and sulphur as well as the micro nutrients manganese, iron, copper, and zinc using the standard lab procedure. The effect of four different sample preparation steps (original, dried, filtered, and dried filter residues) on XRF measurement accuracy was examined. Therefore, XRF results were correlated with values of the reference analysis. The best R²s for each element ranged from 0.64 to 0.92. Comparing the four preparation steps, XRF results for dried samples showed good correlations (0.64 and 0.86) for all elements. XRF measurements using dried filter residues showed also good correlations with R²s between 0.65 and 0.91 except for P, Mg, and Ca. In contrast, correlation analysis for liquid samples (original and filtered) resulted in lower R²s from 0.02 to 0.68, except for K (0.83 and 0.87, respectively). Based on these results, it can be concluded that handheld XRF is a promising measuring system for element analysis in manures and digestates.

Cadmium accumulation in wheat and maize grains from China: Interaction of soil properties, novel enrichment models and soil thresholds

The cadmium (Cd) activity in soil has been widely studied. However, the interactive effects of soil properties (e.g. soil pH, CEC, and SOM) on Cd transfer from soil to grain are generally overlooked. In total 325 datasets including soil pH, CEC, SOM, and soil Cd content were used in this study. The descriptive statistics indicated that Cd content in wheat and maize soils ranged from 0.05 to 10.31 mg/kg and 0.02-13.68 mg/kg, with mean values of 0.87 and 1.14 mg/kg, respectively. Cd contents in wheat and maize grains were 0.01-1.36 mg/kg and 0.001-1.08 mg/kg with average values of 0.15 and 0.10 mg/kg, respectively. The results of SEM demonstrated that the interactive effects of soil properties contributed more to Cd transfer from soil to wheat grain than the soil Cd content. Subsequently, CITs-MLR indicated that the critical factors, including soil pH and total soil Cd content, could mask the contribution of other soil properties on Cd accumulation in grain; soil CEC may prevent Cd from leaching and therefore improve grain Cd level of wheat especially at acidic soil condition. The result of derived Cd thresholds revealed that current Cd thresholds are not completely suitable to wheat and maize grain at different soil conditions. This study provides a new model for further investigation on relationships between soil properties, soil Cd content and grain Cd level.

Treatment of Manure and Digestate Liquid Fractions Using Membranes: Opportunities and Challenges

Manure and digestate liquid fractions are nutrient-rich effluents that can be fractionated and concentrated using membranes. However, these membranes tend to foul due to organic matter, solids, colloids, and inorganic compounds including calcium, ammonium, sodium, sulfur, potassium, phosphorus, and magnesium contained in the feed. This review paper is intended as a theoretical and practical tool for the decision-making process during design of membrane-based systems aiming at processing manure liquid fractions. Firstly, this review paper gives an overview of the main physico-chemical characteristics of manure and digestates. Furthermore, solid-liquid separation technologies are described and the complexity of the physico-chemical variables affecting the separation process is discussed. The main factors influencing membrane fouling mechanisms, morphology and characteristics are described, as well as techniques covering membrane inspection and foulant analysis. Secondly, the effects of the feed characteristics, membrane operating conditions (pressure, cross-flow velocity, temperature), pH, flocculation-coagulation and membrane cleaning on fouling and membrane performance are presented. Finally, a summary of techniques for specific recovery of ammonia-nitrogen, phosphorus and removal of heavy metals for farm effluents is also presented.

Quantitative analysis of the main sources of pollutants in the soils around key areas based on the positive matrix factorization method

Quantitative identification of the main sources of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in soils around multiple types of key areas is of great significance for blocking pollution sources. However, there is a lack of more comprehensive relevant research. In this study, Beijing was taken as the research area and four main sources were identified using the positive matrix factorization (PMF) method. The concentration of Pb, PAHs, Cr, and Hg in soils was significantly affected by the presence of landuse type, road traffic, natural factor, and industrial production, respectively, and the farmland, distance to main road, Proterozoic Changcheng-Jixian parent material and cinnamon soil type, and the gross industrial production make greater contributions to these four factors respectively than other variables. Moreover, the uncertainty of the PMF indicates that this four-factor PMF solution is stable and appropriate. These results provide support for the comprehensive control of soil environmental risks.

Comparative Analysis of Genetic Determinants Encoding Cadmium, Arsenic, and Benzalkonium Chloride Resistance in Listeria monocytogenes of Human, Food, and Environmental Origin

Environmental adaptation of Listeria monocytogenes is a complex process involving various mechanisms that can contribute to their survival in the environment, further spreading throughout the food chain and the development of listeriosis. The aim of this study was to analyze whole-genome sequencing data in a set of 270 strains of L. monocytogenes derived from human listeriosis cases and food and environmental sources in order to compare the prevalence and type of genetic determinants encoding cadmium, arsenic, and benzalkonium chloride resistance. Most of the detected genes of cadmium (27.8%), arsenic (15.6%), and benzalkonium chloride (7.0%) resistance were located on mobile genetic elements, even in phylogenetically distant lineages I and II, which indicates the possibility of their horizontal spread. Although no differences were found in the prevalence of these genes between human and food strains, they have been detected sporadically in strains from the environment. Regarding cadmium resistance genes, cadA1C1_Tn5422 predominated, especially in clonal complexes (CCs) 121, 8, and 3 strains. At the same time, qacH_Tn6188-encoding benzalkonium chloride resistance was most frequently detected in the genome of CC121 strains. Genes encoding arsenic resistance were detected mainly in strains CC2 (located on the chromosomal island LGI2) and CC9 (carried on Tn554). The results indicated a relationship between the spread of genes encoding resistance to cadmium, arsenic, and benzalkonium chloride in certain serotypes and CCs and showed the need for a more extensive study of L. monocytogenes strains to better understand their ability to adapt to the food production environment.

Study on Heavy Metal Contamination in High Water Table Coal Mining Subsidence Ponds That Use Different Resource Reutilization Methods

Heavy metals accumulate in high water table coal mining subsidence ponds, resulting in heavy metal enrichment and destruction of the ecological environment. In this study, subsidence ponds with different resource reutilization methods were used as study subjects, and non-remediated subsidence ponds were collectively used as the control region to analyze the heavy metal distributions in water bodies, sediment, and vegetation. The results revealed the arsenic content in the water bodies slightly exceeded Class III of China’s Environmental Quality Standards for Surface Water. The lead content in water inlet vegetation of the control region and the Anguo wetland severely exceeded limits. Pearson’s correlation, PCA, and HCA analysis results indicated that the heavy metals at the study site could be divided into two categories: Category 1 is the most prevalent in aquaculture pond B and mainly originate from aquaculture. Category 2 predominates in control region D and mainly originates from atmospheric deposition, coal mining, and leaching. In general, the degree of heavy metal contamination in the Anguo wetland, aquaculture pond, and fishery–solar hybrid project regions is lower than that in the control region. Therefore, these models should be considered during resource reutilization of subsidence ponds based on the actual conditions.

Accumulation of potentially toxic elements in agricultural soil and scenario analysis of cadmium inputs by fertilization: A case study in Quzhou county

Fertilizer application has greatly increased crop yield, however impurities in mineral or organic fertilizers, such as heavy metals, are being added to agricultural soils, which would pose a high risk for soil and crop production. 115 soil samples were collected from Quzhou, a typical agricultural county in the North China Plain, to investigate the total content of cadmium (Cd), arsenic (As), lead (Pb), nickel (Ni), copper (Cu), zinc (Zn) and chromium (Cr) in soils. The contamination levels and source apportionment of studied elements were explored by the pollution indices, multivariate statistical approaches and geostatistical analysis. The ranges of Cd, As, Pb, Ni, Cu, Zn and Cr were between 0.08 and 0.35, 5.34-15.9, 7.34-38.9, 12.9-61.3, 7.80-27.0, 31.4-154, and 17.0-50.5 mg/kg and with the mean values 0.16, 9.20, 16.0, 24.7, 17.6, 61.1, and 29.5 mg/kg, respectively. The studied area was slightly polluted mainly by Cd, and higher pollution was found in soils under vegetable crops. The application of mineral phosphate fertilizer and livestock manure were the main source of Cd and Zn, and other elements (As, Pb, Ni and Cu) might originate from soil parent materials. Scenario analyses were performed using the R programming language, based on the cadmium contents in mineral phosphate fertilizers and livestock manures. The results showed that the long-term application of phosphate fertilizers would lead to some Cd enrichment in soil without risk of substantial pollution. Compared to pure mineral fertilizers, the long-term application of blended fertilizers (30% livestock manures and 70% phosphate fertilizers) or livestock manures would incur a higher Cd pollution risk within a short period, with a maximum probability of Cd risk of 55.21%. Mitigation measurements and scientific agronomic practices should be developed to minimize the risk of potential toxic elements in agricultural soil.