Fertilizer usage and cadmium in soils, crops and food

Source identification of heavy metals and metalloids in soil using open-source Tellus database and their impact on ecology and human health

The presence of heavy metals and metalloids (metal(loid)s) in the food chain is a global problem, and thus, metal(loid)s are considered to be Potentially Toxic Elements (PTEs). Arsenic (As), lead (Pb), mercury (Hg), and cadmium (Cd) are identified as prominent hazards related to human health risks throughout the food chain. This study aimed to carry out a source attribution for metal(loid)s in shallow topsoil of north-midlands, northwest, and border counties of the Republic of Ireland, followed by an assessment of the potential ecological and human health risks. The positive Matrix Factorization (PMF) was used for source characterization of PTEs, followed by the Monte Carlo simulation method, used for a probabilistic model to evaluate potential human health risks. The mean concentrations of prioritized metal(loid)s in the topsoil range in the order of Pb (28.83 mg kg-1) > As (7.81 mg kg-1) > Cd (0.51 mg kg-1) > Hg (0.11 mg kg-1) based on the open-source Tellus dataset. This research identified three primary sources of metal(loid) pollution: geogenic sources (36 %), mixed sources of historical mining and natural origin (33 %), and anthropogenic activities (31 %). The ecological risk assessment showed that Ireland's soil exhibits low-moderate pollution levels however, concerns remain for Cd and As levels. All metal(loid)s except Cd showed acceptable non-carcinogenic risk, while Cd and As accounted for high to moderate potential cancer risks. Potato consumption (if grown on land with elevated metal(loid) levels), Cd concentration in soil, and bioaccumulation factor of Cd in potatoes were the three most sensitive parameters. In conclusion, metal(loid)s in Ireland present low to moderate ecological and human health risks. It underscores the need for policies and remedial strategies to monitor metal(loid) levels in agricultural soil regularly and the production of crops with low bioaccumulation in regions with elevated metal(loid) levels.

Acetone O-(2-naphthylsulfonyl) oxime alleviates the toxic effects of cadmium in maize seedlings by increasing the phenolic substance content and antioxidant system activity

The absorption of cadmium by plants largely depends on cadmium contamination in the soil. The development of phytomining and phytoremediation methods to clean cadmium-contaminated ecosystems is an urgent issue that needs to be solved. Therefore, the role of exogenous O-(2-naphthylsulfonyl)oxime (ANSO) to maize seedlings under cadmium stress was tested. The results showed that when ANSO+cadmium application was compared to cadmium, the cadmium content increased by 7.8 times, while the abscisic acid content decreased. Under cadmium stress, ANSO application did not change the relative water content, but increased the chlorophyll content. While carotenoid content increased with cadmium application, it increased further with ANSO+cadmium application. As a result of the positive effects of ANSO application on the antioxidant system under cadmium stress, hydrogen peroxide content, lipid peroxidation and proline content decreased. ANSO application under cadmium stress increased the phenolic substance content. This study shows that exogenous ANSO makes significant contributions to the protection of maize seedlings despite being under cadmium stress. It also provides important references to the fact that despite stress, the cadmium chelation mechanisms of seedlings continue to work actively to accumulate cadmium in tissues, and it has deep implications for the remediation of cadmium-polluted soils.

Effect of long-term application of pig slurry and NPK fertilizers on trace metal content in the soil

One of the goals of sustainable agricultural production is to avoid soil contamination by elements defined as trace metals (TMs). The aim of this study was to assess the long-term impact of the use of pig slurry (PS) and NPK mineral fertilizers on the soil content of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn). In a 9-year crop rotation, PS was used three times only before root crops. The same four levels of NPK doses (N0P0K0, N1P1K1, N3P2K2, N4P2K2) were applied to both plots with and without PS. Soil samples were collected in early spring from topsoil (0-0.3 m) and subsoil (0.3-0.6 m). Three forms of TMs were determined in the soil: pseudo-total (Aqua regia); bioavailable (Mehlich 3 method) and readily bioavailable (mobile) forms (1 M NH4NO3). The tested factors did not have a significant impact on the Cd, Cu and Pb content, regardless of the form analyzed and the soil depth. PS application significantly increased the content of bioavailable forms of Zn regardless of the year, and the content of pseudo-total Zn only in the sugar beet year, i.e. after manure application. Increasing NPK doses increased the content of mobile Zn in the topsoil, especially in PS plots. A tendency to accumulate mobile forms of Cd and Pb was also observed on NPK-fertilized plots. Thus, long-term application of high NPK doses may increase the risk of contamination of the food chain with these metals. The content of mobile Cd and Zn was positively related to the content of total nitrogen in the soil and negatively related to pH.

Cadmium, zinc, and copper leaching rates determined in large monolith lysimeters

Soil mass balances are used to assess the risk of trace metals that are inadvertently applied with fertilizers into agroecosystems. The accuracy of such balances is limited by leaching rates, as they are difficult to measure. Here, we used monolith lysimeters to precisely determine Cd, Cu, and Zn leaching rates in 2021 and 2022. The large lysimeters (n = 12, 1 m diameter, 1.35 m depth) included one soil type (cambisol, weakly acidic) and distinct cropping systems with three experimental replicates. Stable isotope tracers were applied to determine the direct transfer of these trace metals from the soil surface into the seepage water. The annual leaching rates ranged from 0.04 to 0.30 for Cd, 2.65 to 11.7 for Cu, and 7.27 to 39.0 g (ha a)-1 for Zn. These leaching rates were up to four times higher in the year with several heavy rain periods compared to the dry year. Monthly resolved data revealed that distinct climatic conditions in combination with crop development have a strong impact on trace metal leaching rates. In contrast, fertilization strategy (e.g., conventional vs. organic) had a minor effect on leaching rates. Trace metal leaching rates were up to 10 times smaller than fertilizer inputs and had therefore a minor impact on soil mass balances. This was further confirmed with isotope source tracing that showed that only small fractions of Cd, Cu, and Zn were directly transferred from the soil surface to the leached seepage water within two years (< 0.07 %). A comparison with models that predict Cd leaching rates in the EU suggests that the models overestimate the Cd soil output with seepage water. Hence, monolith lysimeters can help to refine leaching models and thereby also soil mass balances that are used to assess the risk of trace metals inputs with fertilizers.

Modeling and identification of affective parameters on cadmium's durability and evaluating cadmium pollution indicators caused by using chemical fertilizers in long term

Soil contamination by anthropogenic heavy metals has become a global issue. This study aimed to investigate cadmium (Cd) concentration, mobility, and contamination indices of Cd in soils in the Hamadan province, west of Iran. To investigate the concentration of Cd in soil, one hundred soil samples from wheat farms and five samples from control lands were collected. Pollution indexes, including Cd mobility, enrichment factor, geoaccumulation index, contamination index, and availability ratio, were investigated. The structural equation model was also used to evaluate effective parameters on cadmium durability in soil. Results showed that mean values of available phosphorus (P) were 83.65, 129, and 65 (mg kg-1) in three land-use types rainfed, irrigated, and controlled, respectively. The mean values of Cd in different land-use types of rainfed, irrigated, and controlled were 0.15, 0.18, and 0.08 (mg kg-1), respectively. The results indicated that the amount of Cd in both forms (available and total) in ones that received fertilizer, especially P fertilizers, was higher than in the controlled one. Other pollution indexes revealed that the study area had been slightly contaminated due to anthropogenic activities. Lime, clay, lead, and OM were identified as affective parameters on cadmium durability. Finally, the results demonstrated that the mobility rate was high. Cd had a higher potential mobility in soil samples in the rain-fed and irrigated land than in the controlled land, and Cd had a low retention time.

Stability of exogenous Cadmium in different vineyard soils and its effect on grape seedlings

Cadmium (Cd) being potentially toxic heavy metal, has become increasingly serious to vineyard soil and grapes in recent years. Soil type is one of the main factors affecting the absorption of Cd in grapes. To investigate the stabilization characteristics and form changes of Cd in different types of vineyard soils, a 90-days incubation experiment was conducted after exogenous Cd addition to 12 vineyard soils from typical vineyards in China. The inhibition of exogenous Cd on grape seedlings was determined based on the pit-pot incubation experiment (200 kg soil per pot). The results demonstrate that Cd concentration in all the sampling sites did not exceed the national screening values (GB15618-2018; i.e., 0.3 mg/kg when pH was lower than 7.5, 0.6 mg/kg when pH was higher than 7.5);. Cd in Fluvo-aquic soil 2, Red soils1, 2, 3 and Grey-Cinnamon soil is dominated by acid-soluble fraction, but was mainly in residual fraction in the remain soils. Throughout the aging process, proportion of the acid-soluble fraction increased and then decreased, while proportion of the residual fraction decreased and then increased, after exogenous Cd was added. The mobility coefficients of Cd in Fluvo-aquic soil 2 and Red soil 1, 2 increased 2.5, 3 and 2 folds, after exogenous Cd addition, respectively. Compared with CK (control), the correlation between total Cd content and its different fractions was relatively weak in the Cdl (low concentration) and Cdh (high concentration) groups. Poor Cd stabilization and strong inhibition of seedling growth rate were observed in Brown soil 1, black soil, red soil 1 and cinnamomic soil. Fluvo-aquic soil 2, 3 and Brown soil 2 showed good Cd stability and small inhibition effect on grape seedlings. These results show that Cd stability in soils and inhibition rate of grape seedlings by Cd are strongly influenced by soil type.

Effects of Agricultural Intensification on Mediterranean Diets: A Narrative Review

INTRODUCTION

Mediterranean diets (MedDiets) are linked to substantial health benefits. However, there is also growing evidence that the intensification of food production over the last 60 years has resulted in nutritionally relevant changes in the composition of foods that may augment the health benefits of MedDiets.

OBJECTIVE

To synthesize, summarize, and critically evaluate the currently available evidence for changes in food composition resulting from agricultural intensification practices and their potential impact on the health benefits of MedDiets.

METHODS

We summarized/synthesized information from (i) systematic literature reviews/meta-analyses and more recently published articles on composition differences between conventional and organic foods, (ii) desk studies which compared food composition data from before and after agricultural intensification, (iii) recent retail and farm surveys and/or factorial field experiments that identified specific agronomic practices responsible for nutritionally relevant changes in food composition, and (iv) a recent systematic literature review and a small number of subsequently published observational and dietary intervention studies that investigated the potential health impacts of changes in food composition resulting from agricultural intensification.

RESULTS AND DISCUSSION

There has been growing evidence that the intensification of food production has resulted in (i) lower concentrations of nutritionally desirable compounds (e.g., phenolics, certain vitamins, mineral micronutrients including Se, Zn, and omega-3 fatty acids, α-tocopherol) and/or (ii) higher concentrations of nutritionally undesirable or toxic compounds (pesticide residues, cadmium, omega-6 fatty acids) in many of the foods (including wholegrain cereals, fruit and vegetables, olive oil, dairy products and meat from small ruminants, and fish) that are thought to contribute to the health benefits associated with MedDiets. The evidence for negative health impacts of consuming foods from intensified conventional production systems has also increased but is still limited and based primarily on evidence from observational studies. Limitations and gaps in the current evidence base are discussed. Conclusions: There is now substantial evidence that the intensification of agricultural food production has resulted in a decline in the nutritional quality of many of the foods that are recognized to contribute to the positive health impacts associated with adhering to traditional MedDiets. Further research is needed to quantify to what extent this decline augments the positive health impacts of adhering to a traditional MedDiet.

Hydrogen peroxide reduces root cadmium uptake but facilitates root-to-shoot cadmium translocation in rice through modulating cadmium transporters

Cadmium (Cd) contamination in agricultural soils has become a serious worldwide environmental problem threatening crop production and human health. Hydrogen peroxide (H₂O₂) is a critical second messenger in plant response to Cd exposure. However, its role in Cd accumulation in various organs of plants and the mechanistic basis of this regulation remains to be elucidated. In this study, we used electrophysiological and molecular approaches to understand how H₂O₂ regulates Cd uptake and translocation in rice plants. Our results showed that the pretreatment of H₂O₂ significantly reduced Cd uptake by rice roots, which was associated with the downregulation of OsNRAMP1 and OsNRAMP5. On the other hand, H₂O₂ promoted the root-to-shoot translocation of Cd, which might be attributed to the upregulation of OsHMA2 critical for Cd²⁺ phloem loading and the downregulation of OsHMA3 involved in the vacuolar compartmentalization of Cd²⁺, leading to the increased Cd accumulation in rice shoots. Furthermore, such regulatory effects of H₂O₂ on Cd uptake and translocation were notably amplified by the elevated level of exogenous calcium (Ca). Collectively, our results suggest that H₂O₂ can inhibit Cd uptake but increase root to shoot translocation through modulating the transcriptional levels of genes encoding Cd transporters, furthermore, application of Ca can amplify this effect. These findings will broaden our understanding of the regulatory mechanisms of Cd transport in rice plants and provide theoretical foundation for breeding rice for low Cd accumulation.

Trifolium repens and biochar addition affecting soil nutrients and bacteria community

Biochar has wide application prospects as a good soil conditioner, leguminous plants can fix nitrogen and improve soil available nutrients. However, it is not clear how adding biochar when planting leguminous plants affects soil bacterial community and soil available nutrients. This study investigates the effects of biochar addition on the content of ammonia nitrogen, Olsen-P, and available potassium in northeastern farmland soils under the plantation of Trifolium repens and then compared with the application of organic fertilizer. A 90-day incubation experiment was conducted to compare the changes in the structure and relative abundance of soil microflora under varied biochar additions. It was found that the addition of biochar could affect the structure of the microflora and the available nutrients in the soil. When compared with soil planted with T. repens without the addition of biochar, with the application of 3% biochar increased the content of ammonia nitrogen, Olsen-P, and available potassium in the soil by 31.71%, 21.40%, and 11.51%, respectively. High throughput sequencing revealed that the relative abundance of functional bacteria such as azotobacter, rhizobacteria, and phosphorus solubilizing bacteria in the soil increased with the addition of biochar. Furthermore, the effect was more obvious with the addition of organic fertilizers. The addition of biochar improved the microbial community structure and increased the relative abundance of functional bacteria and the content of available nutrients in the soil. This is expected to reduce the application of chemical fertilizers, thereby protecting the environment and conserving natural resources.

Effect of phosphorus sources on growth and cadmium accumulation in wheat under different soil moisture levels

Both cadmium (Cd) toxicity and water limited stress in crop plants are serious concerns worldwide while little is known about the impact of various phosphorus (P) sources on Cd accumulation in cereals especially under water limited stress. A study was conducted to explore the efficiency of three frequently available P fertilizers on Cd accumulation in wheat under different soil moisture levels. Three different P sources including diammonium phosphate (DAP), single super phosphate (SSP), and nitrophos (NP) were applied in the soil with three levels (0, 50 and 100 mg/kg). The drought stress was applied to half treatments during the latter growth stages of wheat and plants were harvested at maturity. The results demonstrated that water-limited stress decreased the growth and yield of plants than respective treatments without water stress. P supply increased the growth of wheat irrespective of water-limited stress. The effect on growth and yield varied with the sources and levels of P and maximum effects was observed in DAP treatment (100 mg/kg). The P amendments enhanced the leaf photosynthesis and activities of SOD, POD, CAT and decreased the leaf oxidative burst. Water limited stress enhanced the Cd concentrations in shoots, roots, and grains whereas P amendments minimized the Cd concentrations and enhanced the P concentrations in these parts of plants. The results obtained demonstrated that P supply in the form of DAP might be effective in minimization of Cd in grains and can be used for safe cultivation of metal-contaminated soils.

Soil Quality Assessment in Farmland of a Rapidly Industrializing Area in the Yangtze Delta, China

The comprehensive quality assessment of farmland soil is critical for agricultural production and soil ecological protection. Currently, there is no systematic method for conducting a comprehensive quality assessment of farmland soil; subsequently, as the most developed economic area in China, the comprehensive quality assessment of farmland soil in the Yangtze River Delta is lacking. We chose the farmland soil of Suzhou city as the research object. The soil fertility index (SFI) and soil environment index (SEI) were calculated with the membership function and Nemerow index. Finally, the comprehensive assessment of soil quality was achieved with the TOPSIS model. The results showed that the average values of soil pH, SOM, TN, AHN, AP, and AK were 6.44 (slightly acidic), 28.17 g/kg (medium), 1.63 g/kg (rich), 118.16 mg/kg (medium), 38.31 mg/kg (rich), and 160.63 mg/kg (rich), respectively. For the concentrations of heavy metals, including Cr, Ni, Cu, Zn, Cd, and Pb, in 122 soil samples, the percentages exceeding the background values of Jiangsu province were 5.74%, 8.20%, 8.20%, 10.66%, 86.07%, and 84.43%, respectively. Cd and Pb were the main heavy metal pollutants on farmlands. The soil samples with SFI values below the medium level (SFI < 0.6) accounted for 44.26%, and samples with SEI values below the medium level (SEI < 0.6) accounted for 13.12%. The values of the soil quality index (SQI) ranged from 0.171 to 0.996, with an average SQI value of 0.586 (very poor-V), and approximately half of the farmland soil quality in Suzhou city needed to be further improved. In a word, this study provides a theoretical basis and scientific support for the quality assessment and rational utilization of farmland soil.

Racial disparities in liver cancer: Evidence for a role of environmental contaminants and the epigenome

Liver cancer incidence has tripled since the early 1980s, making this disease one of the fastest rising types of cancer and the third leading cause of cancer-related deaths worldwide. In the US, incidence varies by geographic location and race, with the highest incidence in the southwestern and southeastern states and among racial minorities such as Hispanic and Black individuals. Prognosis is also poorer among these populations. The observed ethnic disparities do not fully reflect differences in the prevalence of risk factors, e.g., for cirrhosis that may progress to liver cancer or from genetic predisposition. Likely substantial contributors to risk are environmental factors, including chemical and non-chemical stressors; yet, the paucity of mechanistic insights impedes prevention efforts. Here, we review the current literature and evaluate challenges to reducing liver cancer disparities. We also discuss the hypothesis that epigenetic mediators may provide biomarkers for early detection to support interventions that reduce disparities.

Distribution and ecological risk assessment of trace elements in the paddy soil-rice ecosystem of Punjab, Pakistan

Trace elements (TEs) contamination of agricultural soils requires suitable criteria for regulating their toxicity limits in soil and food crops, which depends on their potential ecological risk spanning regional to global scales. However, no comprehensive study is available that links TE concentrations in paddy soil with ecological and human health risks in less developed regions like Pakistan. Here we evaluated the data set to establish standard guidelines for defining the hazard levels of various potentially toxic TEs (such as As, Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, Se, Zn) in agricultural paddy soils of Punjab, Pakistan. In total, 100 topsoils (at 0-15 cm depth) and 204 rice plant (shoot and grain) samples were collected from five ecological zones of Punjab (Gujranwala, Hafizabad, Vehari, Mailsi, and Burewala), representing the major rice growing regions in Pakistan. The degree of contamination (C_d) and potential ecological risk index (PERI) established from ecological risk models were substantially higher in 100% and 97% of samples, respectively. The positive matrix factorization (PMF) model revealed that the elevated TEs concentration, notably Cd, As, Cr, Ni, and Pb, in the agricultural paddy soil was attributed to the anthropogenic activities and groundwater irrigation. Moreover, the concentration of these TEs in rice grains was higher than the FAO/WHO's safe limits. This study provided a baseline, albeit critical knowledge, on the impact of TE-allied ecological and human health risks in the paddy soil-rice system in Pakistan; and it opens new avenues for setting TEs guidelines in agro-ecological zones globally, especially in underdeveloped regions.

Zinc fortification and alleviation of cadmium stress by application of lysine chelated zinc on different varieties of wheat and rice in cadmium stressed soil

Sustainable and cost-effective methods are required to increase the food production and decrease the toxic effects of heavy metals. Most of the agriculture land is contaminated with cadmium (Cd). The present study was designed to minimize the toxic effect of Cd stress (0, 10 and 20 mg kg1-) on tolerant and sensitive varieties of wheat (Punjab-2011; Sammar) and rice (Kisan Basmati; Chenab) under Zn-lysine (Zn-lys) application as foliar spray (0, 12.5 and 25 mM) and seed priming (0, 3 and 6 ppm). Remarkable decrease was observed in plant growth, physiology and biochemistry as well as increase in Cd uptake, roots to shoots and grains of both crops. Cd significantly reduced the root and shoot lengths, root and shoot dry weights, transpiration rate, photosynthetic rate, stomatal conductance and water use efficiency as well as chlorophyll contents associated with enhanced electrolyte leakage (EL), malondialdehyde (MDA) and H2O2 and Cd uptake in different plant parts including grains of both crop varieties. The foliar application of Zn-lys (0, 12.5 and 25 mM) ameliorated the toxic effect of Cd on growth and physiology associated with decrease in EL, MDA and H2O2 and improved the activities of SOD, POD, CAT and APX enzymes with decreasing Cd uptake in tolerant varieties of wheat and rice as compared to seed priming. Furthermore, it has been investigated that the foliar application of Zn-lys is effective to improve quality of wheat and rice tolerant varieties (Punjab-2011 and Chenab) under Cd contamination soils.

An Assessment of Trace Element Accumulation in Palm Oil Production

African oil palm (Elaeis guineensis) is grown on 17,000,000 hectares in Southeast Asia, producing oil and the by-product, palm kernel expeller (PKE), for export. Elaeis guineensis is typically produced on weathered acidic soils, with fertilisers and fungicides used to increase production. These amendments can contain elevated concentrations of trace elements (TEs), either as the active ingredient (e.g., Cu-based fungicides) or as contaminants, including F, Zn, As, Cd, Pb and U. TEs may accumulate in soil over time, and be taken up by plants, posing a food-chain transfer risk if allowed to exceed soil guideline values. We reviewed available literature on trace elements in soil, plant material, oil and PKE to evaluate the risk of TE accumulation due to phosphate fertiliser and Cu-fungicide use. TE concentrations of Cu, Zn, and Cd were reported to be up to 69, 107 and 5.2 mg kg−1, respectively, in E. guineensis plantation soils, while Cu and As were reported to be up to 28.9 and 3.05 mg kg−1, respectively, in PKE (>50% their permissible limits). Iron, a TE, has also been reported in PKE up to 6130 mg kg−1 (>10-fold the permissible limit). TE accumulation is an emerging issue for the palm oil industry, which, if unaddressed, will negatively affect the industry’s economic and environmental sustainability. There are critical knowledge gaps concerning TEs in palm oil systems, including a general lack of research from Southeast Asian environments and information concerning key contaminants (Fe, Cu, As and Cd) in soils, plants and PKE.

Plant-Mycorrhizal Fungi Interactions in Phytoremediation of Geogenic Contaminated Soils

Soil contamination by geogenic contaminants (GCs) represents an imperative environmental problem. Various soil remediation methods have been successfully employed to ameliorate the health risks associated with GCs. Phytoremediation is considered as an eco-friendly and economical approach to revegetate GC-contaminated soils. However, it is a very slow process, as plants take a considerable amount of time to gain biomass. Also, the process is limited only to the depth and surface area of the root. Inoculation of arbuscular mycorrhizal fungi (AMF) with remediating plants has been found to accelerate the phytoremediation process by enhancing plant biomass and their metal accumulation potential while improving the soil physicochemical and biological characteristics. Progress in the field application is hindered by a lack of understanding of complex interactions between host plant and AMF that contribute to metal detoxification/(im)mobilization/accumulation/translocation. Thus, this review is an attempt to reveal the underlying mechanisms of plant-AMF interactions in phytoremediation.

Changes in Metal Distribution, Vegetative Growth, Reactive Oxygen and Nutrient Absorption of Tagetes patula under Soil Cadmium Stress

Phytoremediation with hyperaccumulator plants has been recognized as a potential way for the clearing of cadmium (Cd)-contaminated soil. In this study, hyperaccumulator Tagetes patula was treated with seven concentrations of Cd, ranging from 0 to 300 mg kg−1. The Cd enrichment and nutrient contents in different organs during different growth phases were investigated. Under Cd concentrations ≤75 mg kg-1, the morphological growth of T. patula did not change significantly regardless of growth stage. However, when Cd concentration exceeded 150 mg kg−1, the morphological growth was remarkedly inhibited. The root/shoot ratio remained unchanged except for at 300 mg kg−1. In addition, Cd negatively influenced the flowering process at the concentration of 300 mg kg−1. Cd content increased significantly in Cd-treated plants. Nitrogen absorption was increased under Cd treatments, and phosphorus content was also increased under concentration ≤150 mg·kg−1. However, the potassium content in the flower was decreased under 300 mg kg−1. Furthermore, the contents of H2O2, O2− and malondialdehyde were increased during the seedling phase, especially when Cd concentration was ≥150 mg kg−1. In summary, T. patula showed a strong ability to tolerate Cd, and such ability might be explained by nutrient absorption and reactive oxygen clearness.

A review on adsorptive separation of toxic metals from aquatic system using biochar produced from agro-waste

Water is a basic and significant asset for living beings. Water assets are progressively diminishing due to huge populace development, industrial activities, urbanization and rural exercises. Few heavy metals include zinc, copper, lead, nickel, cadmium and so forth can easily transfer into the water system either direct or indirect activities of electroplating, mining, tannery, painting, fertilizer industries and so forth. The different treatment techniques have been utilized to eliminate the heavy metals from aquatic system, which includes coagulation/flocculation, precipitation, membrane filtration, oxidation, flotation, ion exchange, photo catalysis and adsorption. The adsorption technique is a better option than other techniques because it can eliminate heavy metals even at lower metal ions concentration, simplicity and better regeneration behavior. Agricultural wastes are low-cost biosorbent and typically containing cellulose have the ability to absorb a variety of contaminants. It is important to note that almost all agro wastes are no longer used in their original form but are instead processed in a variety of techniques to improve the adsorption capacity of the substance. The wide range of adsorption capacities for agro waste materials were observed and almost more than 99% removal of toxic pollutants from aquatic systems were achieved using modified agro-waste materials. The present review aims at the water pollution due to heavy metals, as well as various heavy metal removal treatment procedures. The primary objectives of this research is to include an overview of adsorption and various agriculture based adsorbents and its comparison in heavy metal removal.

Potentially toxic trace element pollution in long-term fertilized agricultural soils in China: A meta-analysis

Fertilization results in potentially toxic trace element (PTTE) pollution in agricultural soils. However, it is unclear which factors determine the effect sizes of fertilization on PTTEs at the multiple spatial-temporal scale. This work synthesized 379 observations in 78 field sites (3-35 years) across China's main grain producing areas, and showed that long-term organic fertilization significantly enhanced total Cu, Zn and Cd by 25.7%, 18.9% and 66.6%, and soil available Cu, Zn and Cd by 60.5%, 155.3% and 83.6%, respectively; whereas long-term inorganic fertilization increased only available Cu, Zn and Cd by an average of 6.3%. Organic fertilizer (OF) type and application rate dominated the variation of PTTE concentrations, where approximately one-half of Cd pollution (42.6% of total Cd and 47% of available Cd) was observed. Furthermore, OFs containing Cd less than 1 mg kg-1 were recommended to be safely applied to agricultural soils. Soil type was main factor under long-term inorganic fertilization determining available PTTE variation, resulted in higher pollution risk in some soils such as Alfisols and Semi-hydromorphic soils, where we suggested the use of lower amounts of P fertilizers or the application of ones having small amounts of PTTEs. In short, long-term organic fertilization caused serious pollution of PTTEs especially Cd in Chinese croplands, and some strategies with a focus towards reducing the pollution risk must be developed, e.g., promoting straw return, forbidding Cd addition to feeds and feed additives, and improving carbon sequestration efficiency (CSE) of OFs and thus soil organic matter (SOM).

Assessing the distribution of cadmium under different land-use types and its effect on human health in different gender and age groups

Cadmium (Cd) is one of the toxic elements entering the food chain in various ways, including chemical fertilizers. This study aimed to assess different amounts and forms of available Cd in soils under wheat cultivation affected by long-term use of phosphorus chemical fertilizers and also to study the rate of Cd intake by people with age and gender differences. To investigate the Cd status in wheat-cultivated lands, 105 soil samples and also 24 wheat samples were collected from three land uses of rainfed, irrigated, and control one. Phosphorus levels were also measured in soil samples to investigate the relationship between the amount of chemical fertilizer consumption and the amount of Cd. The mean values of available Cd were 0.15, 0.18, and 0.08 (mg/kg) under three land-use types of rainfed, irrigated, and control one, respectively, and the mean values of total Cd were also 1.9, 2.22, and 1.30 in the rainfed land, irrigated land, and control one, respectively. The results showed that the amount of available and total Cd in the irrigated and rainfed lands was higher than the amount of Cd in the control sample. According to the results of Cd fractionation, the highest amounts of Cd were in the residual, carbonate, organic, soluble, and exchangeable fractions, respectively. The amounts of Cd in the three parts of root, stem, and grain were 1.08, 0.65, 0.91 (mg/kg), respectively. Finally, the results showed that the rate of Cd entry into the children's body was higher than that of adults and the elderly.

Cadmium concentration and its typical input and output fluxes in agricultural soil downstream of a heavy metal sewage irrigation area

Heavy metal pollution of agricultural soils in sewage irrigation areas is a serious environmental issue. Many prior studies have demonstrated that soil around the irrigation area is polluted with heavy metals, even though they had not been irrigated by wastewater. In this study, a paddy field downstream of the Zhangshi Irrigation Area was selected as the study area. The Cd concentrations and their representative input and output fluxes to and from the topsoil were systematically studied. The results showed that 95.5% of soil samples exceeded the screening value of Cd concentration. The Cd input fluxes via irrigation water and atmospheric deposition, accounting for 56.95% and 42.53% of the total input flux, respectively, were the main sources of Cd in soil. Crop harvesting was the main output pathway, accounting for 89.63% of the total output flux. An estimation of the annual mass balance showed that Cd in the studied area was in a state of accumulation, and the annual increase in Cd concentration in topsoil would be 2.46 µg kg^-1 if the observed fluxes remain. These results will provide a reference for the development of strategies to control and reduce heavy metal contamination and diffusion in agricultural soils around irrigation areas.

X-ray absorption spectroscopy evidence of sulfur-bound cadmium in the Cd-hyperaccumulator Solanum nigrum and the non-accumulator Solanum melongena

It has been proposed that non-protein thiols and organic acids play a major role in cadmium phytoavailability and distribution in plants. In the Cd-hyperaccumulator Solanum nigrum and non-accumulator Solanum melongena, the role of these organic ligands in the accumulation and detoxification mechanisms of Cd are debated. In this study, we used X-ray absorption spectroscopy to investigate Cd speciation in these plants (roots, stem, leaves) and in the soils used for their culture to unravel the plants responses to Cd exposure. The results show that Cd in the 100 mg kg^-1 Cd-doped clayey loam soil is sorbed onto iron oxyhydroxides. In both S. nigrum and S. melongena, Cd in roots and fresh leaves is mainly bound to thiol ligands, with a small contribution of inorganic S ligands in S. nigrum leaves. We interpret the Cd binding to sulfur ligands as detoxification mechanisms, possibly involving the sequestration of Cd complexed with glutathione or phytochelatins in the plant vacuoles. In the stems, results show an increase binding of Cd to -O ligands (>50% for S. nigrum). We suggest that Cd is partly complexed by organic acids for transportation in the sap.

Biochar application modified growth and physiological parameters of Ocimum ciliatum L. and reduced human risk assessment under cadmium stress

Biochar (BC) is prepared from waste organic material that can improve soil health in the contaminated area. Soil pollution with cadmium (Cd) is one of the worldwide problems. The present study aimed to evaluate the BC influence on some morphophysiological and biochemical characteristics, also Cd concentration of Ocimum ciliatum L. leaves under Cd stress as well as human risk assessment. Therefore, a pot factorial arrangement based on a completely randomized design was done which included three levels of BC (non-BC, 1%, and 2% of the pot soil) and three Cd levels (0, 20, and 40 mg/kg soil) with three replications. The results of the present study indicated that BC application improved morphological traits, photosynthetic pigments, relative water content (RWC), and catalase (CAT) activity of O. ciliatum under Cd stress and reduced total soluble sugars, total phenol, antioxidant activity, proline content, electrolyte leakage (EL), soluble protein content, ascorbate peroxidase (APX), and guaiacol peroxidase (GPX) activities, and Cd concentration as well as target hazard quotient (THQ). In conclusion, based on the findings of this study, BC could be applied as an environmental friendly amendment in Cd-polluted soil to ameliorate the negative influences of Cd stress on O. ciliatum and reduces Cd levels and THQ in the plants due to the absorption properties of BC. This means that BC usage in contaminated soil helps to reduce pollutions and decreases the human risk assessment.

Mass balance approach to assess the impact of cadmium decrease in mineral phosphate fertilizers on health risk: The case-study of French agricultural soils

Cadmium is a ubiquitous and highly toxic contaminant that can cause serious adverse effects. The European Food Safety Authority (EFSA) and the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) have shown that the risk related to food contamination by cadmium cannot be ruled out in Europe and France. Fertilizing material is one of the main sources of cadmium contamination in the food chain on which regulators can play to reduce cadmium exposure in the population. The aim of this work was to develop a mass-balance approach integrating the various environmental sources of cadmium to estimate the effects of a decrease in cadmium concentrations in crop fertilizers on dietary exposure and on the health risk. This approach led to a predictive model that can be used as a decision-making tool. Representative and protective fertilization scenarios associated with controlled cadmium levels in mineral phosphate fertilizers were simulated and converted into cadmium fluxes. Cadmium inputs from industrial mineral phosphate fertilizers were then compared with cadmium brought by the application of manure, sewage sludge and farm anaerobic digest, at the levels typical of French agricultural practices. Regardless of the fertilizer and scenario used, a flux lower than 2 g Cd.ha^-1.year^-1 reduces both the accumulation in soils and the transfer of cadmium in the food chain. It corresponds to a cadmium content of 20 mg.kg P₂O₅^-1 or less in mineral phosphate fertilizers. Modelling the transfer of cadmium from the soil to consumed food made it possible to propose cadmium limits in fertilizers applied in France. In a global context of ecological transition to promote human health, this research will help risk managers and public authorities in the regulatory decision-making process for the reduction of environmental cadmium contamination and human exposure.

Cadmium toxicity in plants: Impacts and remediation strategies

Cadmium (Cd) is an unessential trace element in plants that is ubiquitous in the environment. Anthropogenic activities such as disposal of urban refuse, smelting, mining, metal manufacturing, and application of synthetic phosphate fertilizers enhance the concentration of Cd in the environment and are carcinogenic to human health. In this manuscript, we reviewed the sources of Cd contamination to the environment, soil factors affecting the Cd uptake, the dynamics of Cd in the soil rhizosphere, uptake mechanisms, translocation, and toxicity of Cd in plants. In crop plants, the toxicity of Cd reduces uptake and translocation of nutrients and water, increases oxidative damage, disrupts plant metabolism, and inhibits plant morphology and physiology. In addition, the defense mechanism in plants against Cd toxicity and potential remediation strategies, including the use of biochar, minerals nutrients, compost, organic manure, growth regulators, and hormones, and application of phytoremediation, bioremediation, and chemical methods are also highlighted in this review. This manuscript may help to determine the ecological importance of Cd stress in interdisciplinary studies and essential remediation strategies to overcome the contamination of Cd in agricultural soils.

A colorimetric paper-based ATONP-ALP nanobiosensor for selective detection of Cd2+ ions in clams and mussels

A colorimetric paper-based enzyme-coupled antimony tin oxide nanoparticle (ATONP) nanobiosensor for selective detection of Cd²⁺ ions in clams and mussels is presented. Alkaline phosphatase (ALP) was immobilized on ATONPs via 16-phosphonohexadecanoic acid (16-PHA) to develop ATONP-ALP nanobiosensor. The biosensor was characterized using XPS, Raman spectroscopy, SEM, and EDX. ATONP-ALP nanobiosensor exhibited high selectivity towards detection of Cd²⁺ ion with a LOD 0.006 μg L^-1 and linear range of detection 0.005-1 μg L^-1. The developed biosensor was further integrated into a low-cost paper-based format. A visual color change was obtained for Cd²⁺ ion in the range 0.1-10 μg L^-1. The developed biosensor was successfully demonstrated for the analysis of Cd²⁺ ions in clams with recoveries 101-104%. The ATONP-ALP nanobiosensor was validated using mussel tissue (BCR-668) and the conventional ICP-OES and ICP-MS techniques.

Phosphate and methionine affect cadmium uptake in valerian (Valeriana officinalis L.)

This study investigated the effects of exogenous methionine (Met) and different phosphate (PO₄) concentrations on Cd uptake and translocation in Valeriana officinalis L. Seedlings were grown in nutrient solutions with three different concentrations of phosphate (900, 1200, and 1500 μM) for two weeks, then exposed for 4 days to 10 μM Cd, either in presence or absence of 400 μM methionine. The Met treatment decreased root Cd accumulation by up to 40%, while it enhanced Cd uptake into the shoots by 50%. In absence of Met, shoot Cd uptake was not affected by the level of phosphate application, although root Cd contents increased. The latter effect was entirely due to increased apoplastic Cd binding. In presence of Met, the Cd accumulation of both plant parts showed trends to increase with increasing phosphate level. In contrast to the treatments without Met, however, the phosphate effect on root Cd was due to increased symplastic root Cd allocation. The results suggest that the effects of Met on Cd uptake were due to the formation of mobile Cd-Met complexes, reducing phosphate-promoted Cd-retention in the apoplast and enhancing Cd transfer into the root symplast. Irrespective of the treatment, shoot Cd accumulation showed a close linear relationship to shoot mass, suggesting that convective transport with the transpirational water stream was the rate-governing uptake process. The results indicate that methionine supplementation could reduce Cd accumulation in valerian roots, which are the parts of this plant harvested for medicinal purposes, in Cd-contaminated soil, while phosphate would enhance it.

Peptone-Induced Physio-Biochemical Modulations Reduce Cadmium Toxicity and Accumulation in Spinach (Spinacia oleracea L.)

The accumulation of cadmium (Cd) in edible plant parts and fertile lands is a worldwide problem. It negatively influences the growth and productivity of leafy vegetables (e.g., spinach, Spinacia oleracea L.), which have a high tendency to radially accumulate Cd. The present study investigated the influences of peptone application on the growth, biomass, chlorophyll content, gas exchange parameters, antioxidant enzymes activity, and Cd content of spinach plants grown under Cd stress. Cd toxicity negatively affected spinach growth, biomass, chlorophyll content, and gas exchange attributes. However, it increased malondialdehyde (MDA), hydrogen peroxide (H₂O₂), electrolyte leakage (EL), proline accumulation, ascorbic acid content, Cd content, and activity of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in spinach plants. The exogenous foliar application of peptone increased the growth, biomass, chlorophyll content, proline accumulation, and gas exchange attributes of spinach plants. Furthermore, the application of peptone decreased Cd uptake and levels of MDA, H₂O₂, and EL in spinach by increasing the activity of antioxidant enzymes. This enhancement in plant growth and photosynthesis might be due to the lower level of Cd accumulation, which in turn decreased the negative impacts of oxidative stress in plant tissues. Taken together, the findings of the study revealed that peptone is a promising plant growth regulator that represents an efficient approach for the phytoremediation of Cd-polluted soils and enhancement of spinach growth, yield, and tolerance under a Cd-dominant environment.

House J, L. Maguire R, G. Skinner H, Hoyo C. Associations between Maternal Cadmium Exposure with Risk of Preterm Birth and Low after Birth Weight Effect of Mediterranean Diet Adherence on Affected Prenatal Outcomes

Prenatal cadmium exposure at non-occupational levels has been associated with poor birth outcomes. The intake of essential metals, such as iron and selenium, may mitigate cadmium exposure effects. However, at high levels, these metals can be toxic. The role of dietary patterns rich in these metals is less studied. We used a linear and logistic regression in a cohort of 185 mother-infant pairs to assess if a Mediterranean diet pattern during pregnancy modified the associations between prenatal cadmium exposure and (1) birth weight and (2) preterm birth. We found that increased cadmium exposure during pregnancy was associated with lower birth weight (β = -210.4; 95% CI: -332.0, -88.8; p = 0.008) and preterm birth (OR = 0.11; 95% CI: 0.01, 0.72; p = 0.04); however, these associations were comparable in offspring born to women reporting high adherence to a Mediterranean diet (β = -274.95; 95% CI: -701.17, 151.26; p = 0.20) and those with low adherence (β = -64.76; 95% CI: -359.90, 230.37; p = 0.66). While the small sample size limits inference, our findings suggest that adherence to a Mediterranean dietary pattern may not mitigate cadmium exposure effects. Given the multiple organs targeted by cadmium and its slow excretion rate, larger studies are required to clarify these findings.

Membrane fouling control by Ca2+ during coagulation-ultrafiltration process for algal-rich water treatment

Seasonal algal bloom, a water supply issue worldwide, can be efficiently solved by membrane technology. However, membranes typically suffer from serious fouling, which hinders the wide application of this technology. In this study, the feasibility of adding Ca²⁺ to control membrane fouling in coagulation-membrane treatment of algal-rich water was investigated. According to the results obtained, the normalized membrane flux decreased by a lower extent upon increasing the concentration of Ca²⁺ from 0 to 10 mmol/L. Simultaneously, the floc particle size increased significantly with the concentration of Ca²⁺, which leads to a lower hydraulic resistance. The coagulation performance is also enhanced with the concentration of Ca²⁺, inducing a slight osmotic pressure-induced resistance. The formation of Ca²⁺ coagulation flocs resulted in a looser, thin, and permeable cake layer on the membrane surface. This cake layer rejected organic pollutants and could be easily removed by physical and chemical cleaning treatments, as revealed by scanning electron microscopy images. The hydraulic irreversible membrane resistance was significantly reduced upon addition of Ca²⁺. All these findings suggest that the addition of Ca²⁺ may provide a simple-operation, cost-effective, and environmentally friendly technology for controlling membrane fouling during coagulation-membrane process for algal-rich water treatment.

Input of Cd from agriculture phosphate fertilizer application in China during 2006-2016

Phosphate fertilizer applications are an important source of soil Cd in China. However, the input of Cd from phosphate fertilizer has always been neglected in China because of its low content. In this paper, we calculated the Cd input from phosphate fertilizer in China during 2006-2016. According to the data, the total phosphate fertilizer consumption and agriculture application rate tended to decrease after 2014. In 2016, the phosphate fertilizer application rate ranged from 12.14 to 99.38 kg/ha with a mean value of 42.70 kg/ha, and excessive fertilizer application occurred in Xinjiang, Henan, and Hubei Provinces. The Cd content in phosphate fertilizer was 0.75 mg/kg based on 1222 samples. The national Cd input from phosphate fertilizer was estimated to be 10.52 tons in 2016, with DAP/MAP being the largest contributor, accounting for 83.31% of the total input. These findings demonstrate the necessity of performing assessments to regulate the utilization of phosphate fertilizer in China, especially in Henan and Xinjiang Provinces.

Cd, Cu, and Zn Accumulations Caused by Long-Term Fertilization in Greenhouse Soils and Their Potential Risk Assessment

The intense management practices in greenhouse production may lead to heavy metal (HM) accumulations in soils. To determine the accumulation characteristics of HM and to evaluate possible HM sources in greenhouse soils, thirty typical greenhouse soil samples were collected in Shouguang District, Shandong Province, China. The results indicate that the Cd, Cu, and Zn concentrations are, respectively, 164.8%, 78.6%, and 123.9% higher than their background values. In the study area, Cd exhibits certain characteristics, such as wide variations in the proportion of its exchangeable form and the highest mobility factor and geo-accumulation index, which are indicative of its high bioavailability and environmental risk. In addition, there is a significant positive correlation between pairs of Cd, P, soil organic carbon, and cultivation age. Combined with principal component analysis, the results indicate the clear effects that agricultural activities have on Cd, Cu, and Zn accumulation. However, Cr, Ni, and Pb have a significant correlation with soil Fe and Al (hydr)-oxides, which indicates that these metals mainly originate from parent materials. This research indicated that long-term intensive fertilization (especially the application of chemical fertilizers and livestock manure) leads to Cd, Cu, and Zn accumulation in greenhouse soils in Shouguang. And the time required to reach the maximum permeable limit in agricultural soils for Cd, Cu, and Zn is 23, 51, and 42 years, respectively, based on their current increasing rates.

Soil amendments for cadmium phytostabilization by five marigold cultivars

In recent years, ornamental plants have come under investigation as phytoremediation agents. In addition to reducing contaminant concentrations in soil, such plants support local economies by serving social (e.g., religious) and decorative purposes. Greenhouse studies investigated the phytostabilization potential of soil cadmium (Cd) by five cultivars of marigold (Tagetes erecta), a common ornamental flower in Asia. The effects of organic (cattle manure and pig manure) and inorganic (leonardite and Osmocote®) amendments in supporting plant growth and enhancing Cd uptake were also examined. Marigold cultivars Babuda and Sunshine grown in soil supplemented with pig manure produced the greatest biomass and experienced greatest Cd accumulation and flower production. In all treatments, plant parts accumulated Cd in the following order: root > shoot ≈ flower. Furthermore, Babuda and Sunshine cultivars had a high phytostabilization potential as evidenced by translocation factors < 1 and bioconcentration factors > 1 for roots. It is proposed that Babuda and Sunshine marigold cultivars be applied toward Cd phytostabilization while enhancing local economies as an ornamental species.