Soil contamination with cadmium, consequences and remediation using organic amendments

Challenges in microbially and chelate-assisted phytoextraction of cadmium and lead - A review

Cadmium (Cd) and lead (Pb) are ubiquitously present in surface soils, due to anthropogenic activities, causing threat to ecological and human health because of their carcinogenic nature. They accumulate in large quantities in the environment and affect negatively soil microbiota, plants, animals, and humans. For the cleanup of Cd/Pb polluted soils, different plant species have been studied. Many plants have shown the potential to hyperaccumulate Cd/Pb in their above-ground tissues. These plants decrease soil pH by root exudation or by releasing H⁺ ions, and this, in turn, increases the bioavailability of Cd/Pb for plant uptake. Different environmental processes related to soil organic matter, microorganisms, pH, genetic modifications, and various soil-borne chelating agents affect the potential of phytoremediation technology. Review papers trying to identify a single factor influencing the phytoremediation of heavy metals are available in the literature. However, an integrated approach dealing with different factors involved in the remediation of both metals is scarcely discussed. The main focus of this review is to discuss the phytoextraction technique for Cd/Pb removal from contaminated sites along with detoxification mechanisms. Further, the challenges in the Cd/Pb phytoextraction and different options available to cope with these challenges are also discussed. The update on the relevant findings on the use of microorganisms and amendments in enhancing the Cd/Pb phytoextraction is also provided. Finally, the areas to be explored in future research for the removal of Cd/Pb by integrated strategies have been discussed.

24-epibrassinolide improves differential cadmium tolerance of mung bean roots, stems, and leaves via amending antioxidative systems similar to that of abscisic acid

Cadmium (Cd) pollution has attracted global concern. In the present study, the biochemical mechanisms underlying the amelioration of 24-epibrassinolide (eBL) and abscisic acid (ABA) on Cd tolerance of roots, stems, and leaves in mung bean seedlings were comparatively analyzed. Foliar application of eBL markedly ameliorated the growth of mung bean seedling exposed to 100 μM Cd. eBL alone had no significant effects on the activities of antioxidative enzymes and the contents of glutathione (GSH) and polyphenols in the three organs whereas significantly increased the root, stem, and leaf proline contents on average by 54.9%, 39.9%, and 94.4%, respectively, and leaf malondialdehyde (MDA) content on average by 69.0% compared with the controls. When the plants were exposed to Cd, eBL significantly reversed the Cd-increased root ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities, root polyphenol, proline, and GSH levels, leaf chlorophyll contents, and MDA levels in the three organs. eBL significantly restored the Cd-decreased leaf catalase (CAT) activity and leaf polyphenol levels. These results indicated that eBL played roles in maintaining cellular redox homeostasis and evidently alleviated Cd-caused membrane lipid peroxidation via controlling the activity of antioxidative systems. eBL mediated the differential responses of cellular biochemical processes in the three organs to Cd exposure. Furthermore, a comparative analysis revealed that, under Cd stress, the effects of eBL on the biochemical processes were very similar to those of ABA, suggesting that ABA and eBL improve plant Cd tolerance via some common downstream pathways.

The Microbiology of Metal Mine Waste: Bioremediation Applications and Implications for Planetary Health

Mine wastes pollute the environment with metals and metalloids in toxic concentrations, causing problems for humans and wildlife. Microorganisms colonize and inhabit mine wastes, and can influence the environmental mobility of metals through metabolic activity, biogeochemical cycling and detoxification mechanisms. In this article we review the microbiology of the metals and metalloids most commonly associated with mine wastes: arsenic, cadmium, chromium, copper, lead, mercury, nickel and zinc. We discuss the molecular mechanisms by which bacteria, archaea, and fungi interact with contaminant metals and the consequences for metal fate in the environment, focusing on long-term field studies of metal-impacted mine wastes where possible. Metal contamination can decrease the efficiency of soil functioning and essential element cycling due to the need for microbes to expend energy to maintain and repair cells. However, microbial communities are able to tolerate and adapt to metal contamination, particularly when the contaminant metals are essential elements that are subject to homeostasis or have a close biochemical analog. Stimulating the development of microbially reducing conditions, for example in constructed wetlands, is beneficial for remediating many metals associated with mine wastes. It has been shown to be effective at low pH, circumneutral and high pH conditions in the laboratory and at pilot field-scale. Further demonstration of this technology at full field-scale is required, as is more research to optimize bioremediation and to investigate combined remediation strategies. Microbial activity has the potential to mitigate the impacts of metal mine wastes, and therefore lessen the impact of this pollution on planetary health.

The effects of cadmium on the development of Drosophila and its transgenerational inheritance effects

A new focus in toxicology research is the impact of parental exposure to environmental toxic substances on the characteristics of offspring. In the present study, newly produced eggs of Drosophila melanogaster were treated with different concentrations of cadmium (0, 1, 2, 4, 8 mg/kg) to study the effects of development. The results showed that cadmium changed the larval body length and weight, prolonged the pupation and eclosion time, and changed the relative expression levels of development-related genes (baz, β-Tub60D, tj). Furthermore, the parental Drosophila (F₀) were treated with cadmium (4.5 mg/kg) from egg stage, and when grows to adults, they mated in standard medium to produce the de-stressed offspring (F₁-F₄) to assess the transgenerational effects of developmental delay. The results showed that the delayed effects of the pupation and eclosion time could be maintained for two generations, and the inhibiting effects of juvenile hormone (JH) and ecdysone (20-hydroxyecdysone, 20E) could be maintained for two or three generations. More importantly, cadmium increased the expression of DNA methylation-related genes (dDnmt2, dMBD2/3) in the ovaries (F₀-F₂) and testicles (F₀ and F₁). In addition, cadmium accumulated in parental Drosophila (F₀) was not transmitted to offspring through reproductive pathway. These results demonstrate that the developmental toxicity caused by cadmium could be transmitted to the de-stressed offspring, and the observed transgenerational inheritance effects may be associated with epigenetic regulation, underscoring the need to consider fitness of future generations in evaluating the toxicity and environmental risks of cadmium.

Aging and phytoavailability of newly introduced and legacy cadmium in paddy soil and their bioaccessibility in rice grain distinguished by enriched isotope tracing

Phytoavailability of Cadmium (Cd) plays a critical role in its accumulation in soil-rice systems. However, differential aging and phytoavailability of newly introduced Cd (Cd_N) and legacy Cd (Cd_L) in the soil-rice system remains unknown. Moreover, distinguishing their aging and phytoavailability is challenging. Enriched ¹¹²Cd isotope was introduced into a series of pot experiments, combined with sequential extraction and isotope dilution (¹¹⁰Cd isotopic spike), to investigate the aging and distribution of Cd_N and Cd_L under different treatments. The treatments included simulated acid rain, slaked lime, and biochar. Cd_N aged quickly than Cd_L in flooded soil and its availability was similar to that of Cd_L after tillering stage. The grain Cd contents were positively correlated to Cd concentrations in the overlying water. Acid rain reduced the soil pH, increasing the grain Cd, while slaked lime reduced grain Cd content. The acidic biochar used in this study increased grain Cd, possibly through soil acidification-induced Cd release. The differences in bioaccumulation and translocation factors between Cd_N and Cd_L in rice plants under slaked lime and biochar treatments suggested their different in vivo complexations and translocations. Analysis of bioaccessibility of Cd_N and Cd_L in rice grains provided valuable insights regarding human Cd exposure.

Steel mill waste application in soil: dynamics of potentially toxic elements in rice and health risk perspectives

Potentially toxic elements (PTEs) are of great concern in steel mill wastes. Therefore, in order to use them as potential fertilizers in soil, risk assessments are needed. Three steel mill wastes were tested as possible amendments for soils at seven different doses (0, 0.5, 1, 2, 4, 8, 16 t ha^-1): phosphate mud (PM), metallurgical press residue (MPR), and filter press mud (FPM) during rice cultivation in a pot experiment in a Haplic Gleisol. Analysis on rice tissues, including roots, shoots, husk, and grains, were conducted and contents of Cu, Cd, Ni, Zn, Mn, and Pb were assessed. Translocation and bioaccumulation factors were calculated for each element. In general, PTEs are more accumulated in roots and greater contents of Zn and Mn were found, while the lowest ones were found for Pb, probably due to its lack of functional roles during plants development. Higher translocation was observed for Mn, which is associated to the redox conditions of rice cultivation and the high mobility of this element under this condition. Application of steel mill wastes can increase PTE bioavailability and translocation factors, especially PM, but all of the wastes reveal a high hazard index.

Irrigating digestate to improve cadmium phytoremediation potential of Pennisetum hybridum

The bioavailability of heavy metal and growth of hyperaccumulator are key factors controlling the phytoextraction of heavy metal from soil. In this study, the efficacy and potential microbial mechanisms of digestate application in enhancing Cd extraction from soil by Pennisetum hybridum were investigated. The results showed that digestate application significantly promoted the height, tiller number, and biomass yield of Pennisetum hybridum. The application also increased the activities of urease, sucrase, dehydrogenase, available Cd contents of rhizosphere soils (from 2.21 to 2.46 mg kg^-1), and the transfer factors of Cd from root to shoot and leaf. Assuming three annual harvests, digestate application would substantially reduce time needed for Pennisetum hybridum to completely absorb Cd from soil-from 15-16 yr-10 yr. Furthermore, the results of microbial community diversity analysis showed that digestate irrigation was more facilitated for the growth of the predominant bacteria, which were Actinobacteria and Chloroflexi at phylum level, and Sphingomonas and Nitrospiraat genus level, which mainly have the functions of promoted plant growth and metal resistance. The results suggested that the enhanced phytoextraction of Cd by Pennisetum hybridum with digestate application might mainly attributed to the increased Cd bio-availability and the enhanced plant growth, indicating that an approach combining digestate and Pennisetum hybridum could be a promising strategy for remediating Cd-contaminated soils.

Urinary cadmium and stroke - a case-cohort study in Danish never-smokers

BACKGROUND

and Purpose: Cadmium has been associated with risk of cardiovascular events, including stroke. Human cadmium exposure occurs primarily through diet and tobacco smoke. Recent cohort studies have found an association with stroke, but residual confounding from smoking, could not be ruled out. We therefore conducted a case-cohort study to evaluate whether cadmium is associated with stroke in never-smokers.

METHODS

The Danish Diet Cancer and Health cohort consists of Danes 50-64 years old, recruited in 1993-1997. From never-smoking cohort members without previous cancer or stroke we sampled a sub-cohort of 1200 persons. We also identified all (n = 534) cases in the cohort with a validated stroke diagnosis between baseline and 2009. We quantified cadmium and creatinine concentrations from baseline urine samples and used cadmium per creatinine as our main exposure metric. We used Cox proportional hazards models to estimate hazard ratios (HRs) with age as time scale and adjusting for BMI, education and urinary cotinine with and without stratification by sex.

RESULTS

The median urinary cadmium concentration was 0.21 μg cadmium/g creatinine in cases and 0.19 μg/g in the sub-cohort. The majority (83%) of stroke cases were diagnosed with ischemic stroke. The HR for stroke in the highest quartile of exposure (median 0.44 μg/g creatinine) was 1.11 (95% CI: 0.79-1.54) compared with the lowest quartile (median 0.10 μg/g creatinine). The HR per inter quartile range (IQR, 0.19 μg/g creatinine) was 1.02 (95% CI: 0.92-1.12). Among men, the HR per IQR higher levels of cadmium (0.16 μg/g creatinine) was 1.18 (95% CI: 0.92-1.52), and 1.00 (95% CI: 0.89-1.12) among women. Adjusting for creatinine or using osmolality instead of creatinine standardization generally attenuated observed relationships.

CONCLUSIONS

Our results do not support that low levels of cadmium exposure among never-smokers are strongly associated with risk of stroke, although results varied somewhat by sex and method of accounting for urinary dilution.

Deciphering the dynamics of glomalin and heavy metals in soils contaminated with hazardous municipal solid wastes

Heavy metals (HMs) accumulation in the soils poses risks towards the environment and health. Glomalin related soil protein (GRSP) produced by arbuscular mycorrhizal fungi (AMF) has metal-sorption and soil aggregation properties and is critical in the survival of plants and AMF. For the first time, this study attempted to examine the GRSP mediated bio-stabilization of HMs in soils contaminated with municipal solid wastes (MSW). The content and interrelationship of GRSP and HMs, along with soil physicochemical properties were studied in 20 different soil samples from the dumping site. Higher amount of GRSP indicated potential bio-stabilization of HMs at some sites. GRSP exhibited weak positive correlation with essential (Zn, Cu) and toxic HMs (Cd, Ni). Cr and Mn were possibly sequestered in AMF structures and thus found to be negatively correlated with GRSP. The positive correlation observed between GRSP and soil nutrients like N, P and soil organic carbon (SOC) indicating potential of AMF-GRSP in sustaining soil health. Results revealed that AMF residing at contaminated sites produced higher amount of GRSP potentially to bio-stabilize the HMs, and reduce their bioavailability and also facilitate SOC sequestration.

Availability of Trace Elements in Soil with Simulated Cadmium, Lead and Zinc Pollution

The research was based on a pot experiment in which the impact of increasing Cd, Zn and Pb doses on the content of available trace elements in soil was compared. Seven series of trials were designed: 1 (Cd), 2 (Pb), 3 (Zn), 4 (Cd + Pb), 5 (Cd + Zn), 6 (Pb + Zn), 7 (Cd + Pb + Zn). Aside from the control one (without the metals), three increasing levels of contamination were considered within each series. Mobile forms of trace elements (Cd, Pb, Zn, Fe, Mn, Cu, Ni, Co, and Cr) in soil were determined, in addition to which selected physicochemical soil properties—reaction (pH), salinity (EC), hydrolytic acidity (HAC), total exchange bases (TEB)—were identified while cation exchange capacity (CEC), base saturation (BS) and availability factor (AF) were calculated. The application of Cd and Pb to soil resulted in an increase in the share of potentially available forms of these metals in their total content. The availability factor (AF) in the pots polluted with these metals was higher than in the control, in the range 17.5–20.0% for Cd, and 62.8–71.5% for Pb. In turn, the share of Zn mobile forms was comparable in most experimental objects, oscillating around 30%. Moreover, addition to soil of Cd, Pb and Zn usually caused a significant decrease in the content of available forms of Fe, Mn and Cu, and resulted in significantly higher content of available forms of Cr in the soil.

Effects of Cadmium Exposure on the Immune System and Immunoregulation

Cadmium (Cd), a biologically non-essential heavy metal, is widespread in the environment, including the air, water, and soil, and is widely present in foods and quantum dot preparations. Cd enters the body primarily through inhalation and ingestion. Its biological half-life in humans is 10-35 years; therefore, Cd poses long-term health risks. While most studies on Cd toxicity have focused on organ and tissue damage, the immunotoxicity of Cd has drawn increasing attention recently. Cd accumulates in immune cells, modulates the function of the immune system, triggers immunological responses, and leads to diverse health problems. Cd acts as an immunotoxic agent by regulating the activity and apoptosis of immune cells, altering the secretion of immune cytokines, inducing reactive oxygen species (ROS) production and oxidative stress, changing the frequency of T lymphocyte subsets, and altering the production of selective antibodies in immune cells. This review summarizes the immunological toxicity of Cd, elucidates the mechanisms underlying Cd toxicity in terms of innate immunity and adaptive immunity, and discusses potential strategies to alleviate the adverse effects of Cd on the immune system.

The growth of plants and indigenous bacterial community were significantly affected by cadmium contamination in soil-plant system

Concentrations of heavy metals continue to increase in soil environments as a result of both anthropogenic activities and natural processes. Cadmium (Cd) is one of the most toxic heavy metals and poses health risks to both humans and the ecosystem. Herein, we explore the impacts of Cd on a soil-plant system composed of oilseed rapes (Brassica napus and Brassica juncea) and bacteria. The results showed that Cd accumulation within tissues of two species of oilseed rapes enhanced with increasing concentrations of Cd in soils, and Cd treatment decreased their chlorophyll content and suppressed rapeseeds growth. Meanwhile, Cd stress induced the changes of antioxidative enzymes activities of both B. napus and B. juncea. Response to Cd of bacterial community was similar in soil-two species of oilseed rapes system. The impact of Cd on the bacterial communities of soils was greater than bacterial communities of plants (phyllosphere and endophyte). The α-diversity of bacterial community in soils declined significantly under higher Cd concentration (30 mg/kg). In addition, soil bacterial communities composition and structure were altered in the presence of higher Cd concentration. Meanwhile, the bacterial communities of bulk soils were significantly correlated with Cd, while the variation of rhizosphere soils bacterial communities were markedly correlated with Cd and other environmental factors of both soils and plants. These results suggested that Cd could affect both the growth of plants and the indigenous bacterial community in soil-plant system, which might further change ecosystem functions in soils.

The Monitoring of Selected Heavy Metals Content and Bioavailability in the Soil-Plant System and Its Impact on Sustainability in Agribusiness Food Chains

This study assisted in identifying and preventing the increase in heavy metals in soil and winter wheat. Its accumulation can affect cultivated crops, quality and crop yields, and consumers’ health. Selected heavy metals were analyzed using the GTAAS method. They were undertaken on selected heavy metals content (Cd, Cu, Pb, and Zn) in arable soils at three sites in Slovakia and their accumulation in parts of cultivated winter wheat. Our study showed that the limit value of Cd in soil samples was exceeded in the monitored arable soils from 2017–2019. The average content values of Cu and Zn did not exceed the limit values, even in Pb values (except for the spring period). The analyses also showed that the heavy metals content for plants bioavailable in soil did not exceed the statutory critical values for Cd, Cu, and Zn’s average content values. However, Pb content exceeded permitted critical values. Heavy metals bioaccumulation (Zn, Cu) was within the limit values in wheat. Analyzed Cd content in wheat roots and Pb content were determined in all parts of wheat except grain. The study showed that grain from cultivated winter wheat in monitored arable soils is not a risk for consumers.

Land Suitability Mapping Using Geochemical and Spatial Analysis Methods

Assessing the suitability of urban and agricultural land is essential for planning sustainable urban and agricultural systems. The main objective of this study is to evaluate the suitability of land in Ioannina plain (western Greece) concerning the soil contents of two potentially toxic elements, cadmium (Cd) and cobalt (Co). Geochemical and spatial analysis methods were applied to assess the distribution of Cd and Co in the soil of the Ioannina plain and identify their origin. The primary anthropogenic sources of Cd and Co in the topsoil of the study area can be attributed to traffic emissions, aircraft operations, vehicle crushing and dismantling activities. Element content is compared to international guidelines and screening values. Cadmium and Co concentration in the soil of the study area is well above the European topsoil mean. Thus, the urban and agricultural lands cover the vast majority (92%) of the total area. Cadmium concentration in soil of the study area with a mean (mg kg−1) 1.7 and 2.0 was observed in agricultural and urban land use, respectively. Cobalt content in soil of the area studied with a mean (mg kg−1) 30.8 and 37.1 was recorded in agricultural and urban land use, respectively. Land evaluation suitability by adopting criteria provided from the international literature is discussed.

Physiological and metagenomic strategies uncover the rhizosphere bacterial microbiome succession underlying three common environmental stresses in cassava

The most common environmental pollutants such as cadmium (Cd), glyphosate and tetracycline have led to profoundly adverse impacts on plant productivity. However, how tropical crops such as cassava sense these pollutants via roots and how rhizosphere microbiome interacts with the host and pollutants remain largely unknown. In this study, we found these stresses significantly inhibited plant growth and triggered cell damage in a dosage-dependent manner, and the toxic effect on redox homeostasis was correlated with antioxidant metabolism. Using metagenomics technique, we found the rhizosphere microbiomes dynamically altered as the dose of these stresses increased. We also identified stressor-associated metagenome-assembled genomes and microbial metabolic pathways as well as mobile genetic elements in the rhizosphere microbiomes. Next, a co-occurrence network of both physiological and microbiome features was constructed to explore how these pollutants derived oxidative damage through the microbiome succession. Notably, phyllosphere transplantation of Agrobacterium tumefaciens or Pseudomonas stutzeri can significantly alleviate the negative effects of stresses on cassava growth and redox homeostasis. Collectively, this study demonstrated the dynamics of rhizosphere bacterial microbiome of cassava under three common environmental stresses, and A. tumefaciens and P. stutzeri could be developed as potential beneficial bacteria to alleviate Cd, glyphosate and tetracycline-triggered damage to cassava.

Effects of natural organic matter on cadmium mobility in paddy soil: A review

Cadmium (Cd) contamination in paddy soil has caused public concern. The uptake of Cd by rice plants depends on soil Cd mobility, which is in turn substantially influenced by organic matter (OM). In this review, we first summarize the fate of Cd in soil and the role of OM. We then focus on the effects of OM on Cd mobility in paddy soil and the factors influencing the remedial effectiveness of OM amendments. We further discuss the performance of straw incorporation in the remediation of Cd-contaminated paddy soils reported in laboratory and field studies. Considering the huge production of organic materials (such as straw) in agriculture, the use of natural OM for soil remediation has obvious appeal due to the environmental benefits and low cost. Although there have been successful application cases, the properties of OM amendments and soil can significantly affect the remedial performance of the OM amendments. Importantly, straw incorporation alone does not often decrease the mobility of Cd in soil or the Cd content in rice grains. Careful evaluation is required when considering natural OM amendments, and the factors and mechanisms that influence their remedial effectiveness need further investigation in paddy soil with realistic Cd concentrations.

Comparative study on protective effect of different selenium sources against cadmium-induced nephrotoxicity via regulating the transcriptions of selenoproteome

Cadmium (Cd) is a ubiquitous environmental pollutant, which mainly input to the aquatic environment through discharge of industrial and agricultural waste, can be a threat to human and animal health. Selenium (Se) possesses a beneficial role in protecting animals and ameliorating the toxic effects of Cd. However, the comparative antagonistic effects of different Se sources such as inorganic, organic Se and nano-form Se on Cd toxicity are still under-investigated. Hence, the purpose of this study was to evaluate the comparative of Se sources antagonism on Cd-induced nephrotoxicity via oxidative stress and selenoproteome transcription. In the present study, Cd-diet disturbed in the system balance of 5 trace elements (Zinc (Zn), copper (Cu), Iron (Fe), Se, Cd) and impaired renal function. Se sources, including nano- Se (NS), Se- yeast (SY), sodium selenite (SS) and mixed selenium (MS) significantly recovered the balance of 4 trace elements (Zn, Cu, Cd, Se) and renal impaired indexes (blood urea nitrogen (BUN) and creatinine (CREA)). Histological appearance of Cd-treated kidney indicated renal tubular epithelial vacuoles, particle degeneration and enlarged capsular space. Ultrastructure observation results illustrated that Cd-induced mitochondrial cristae reduction, membrane disappearance, and nuclear deformation. Treatment with Se sources, NS appeared a better impact on improving kidney tissues against the pathological alterations resulting from Cd administration. Meanwhile, NS reflected a significant impact on relieving Cd-induced kidney oxidative damage, and significantly restored the antioxidant defense system of the body. Our findings also showed NS ameliorated the Cd-induced downtrends expression of selenoproteome and selenoprotein synthesis related transcription factors. Overall, NS was the most effective Se source in avoiding of Cd cumulative toxicity, improving antioxidant capacity and regulating of selenoproteome transcriptome and selenoprotein synthesis related transcription factors expression, which contributes to ameliorate Cd-induced nephrotoxicity in chickens. These results demonstrated diet supplement with NS may prove to be an effective approach for alleviating Cd toxicity and minimizing Cd -induced health risk.

Effect of modified fly ash on environmental safety of two soils contaminated with cadmium and lead

In this study, a low-temperature roasting and hydrothermal methods were used to modify the fly ash resulting in two new types of adsorption materials - modified fly ash (MFA) and artificial zeolite (ZE). These modified fly ashes, as well as a natural zeolite (ZO) were applied to two types of contaminated soils to explore their effects and mechanisms on the behavior of Cd and Pb through leaching column experiments. The bioavailable of Pb, Cd, pH, dissolved organic carbon (DOC), organic matter, as well as the microbial community changings were detected. The results showed that, 2% ZE has a significant stabilizing effect on Cd and the bioavailable fraction contents in Guanzhong (GZ) and Hunan (HN) soils decreased by 40.5% and 53.2%, respectively. However, for Pb, the 2% MFA showed a better result than that of ZE and ZO; the contents of bioavailable Pb in HN and GZ decreased by 48.3% and 30%, respectively. Furthermore, based on the Illumina NovaSep sequencing platform, 18 soil samples of GZ and HN were sequenced for microbial communities. As compared to the control blank(CK) treatment, the abundance of soil microbial communities was significantly improved in the amended soils.

Consistent trade-offs in ecosystem services between land covers with different production intensities

Sustaining multiple ecosystem services across a landscape requires an understanding of how consistently services are shaped by different categories of land uses. Yet, this understanding is generally constrained by the availability of fine‐resolution data for multiple services across large areas and the spatial variability of land‐use effects on services. We systematically surveyed published literature for New Zealand (1970–2015) to quantify the supply of 17 non‐production services across 25 land covers (as a proxy for land use). We found a consistent trade‐off in the services supplied by anthropogenic land covers with a high production intensity (e.g. cropping) versus those with extensive or no production. By contrast, forest cover was not associated with any distinct patterns of service supply. By drawing on existing research findings, we reveal complementarity and redundancy (potentially influencing resilience) in service supply from different land covers. This will guide practitioners in shaping land systems that sustainably support human well‐being.

Comparison between a Traditional (Horse Manure) and a Non-Conventional (Cork Powder) Organic Residue in the Uptake of Potentially Toxic Elements by Lettuce in Contaminated Soils

The use of natural organic correctives is a current agricultural practice that may have advantages for the production of plants in contaminated soils. Cork powder is a natural sub-product of the cork industry that has several potential benefits compared to more commonly used soil amendments. In this work, an evaluation was performed of the use of cork powder (a non-conventional organic residue) and horse manure (traditionally used in agriculture) to control the availability of potentially toxic elements in artificially contaminated soils. Four concentrations were used for each element: Cr (100 to 800 mg kg−1), Ni (37.5 to 300 mg kg−1), Zn (150 to 1200 mg kg−1), Cd (1.5 to 12 mg kg−1) and Pb (150 to 1200 mg kg−1). The accumulation of these elements in lettuce plants grown in pots under controlled conditions was evaluated. With the exception of Cd, no significant differences were detected in the absorption of the different elements by lettuce plants at the studied amounts of correctives applied (1% for cork powder and 0.5% for horse manure). Cadmium was the element that accumulated most in lettuce. Cork powder was shown to be less effective than horse manure in controlling the bioavailability of these elements in the soil. Further tests with chemically modified cork products could improve its efficiency.

Thyroid disrupting effects of low-dose dibenzothiophene and cadmium in single or concurrent exposure: New evidence from a translational zebrafish model

Thyroid hormones (THs) are major regulators of biological processes essential for correct development and energy homeostasis. Although thyroid disruptors can deeply affect human health, the impact of exogenous chemicals and in particular mixture of chemicals on different aspects of thyroid development and metabolism is not yet fully understood. In this study we have used the highly versatile zebrafish model to assess the thyroid axis disrupting effects of cadmium (Cd) and dibenzothiophene (DBT), two environmental endocrine disruptors found to be significantly correlated in epidemiological co-exposure studies. Zebrafish embryos (5hpf) were exposed to low concentrations of Cd (from 0.05 to 2 μM) and DBT (from 0.05 to 1 μM) and to mixtures of them. A multilevel assessment of the pollutant effects has been obtained by combining in vivo morphological analyses allowed by the use of transgenic fluorescent lines with liquid chromatography mass spectrometry determination of TH levels and quantification of the expression levels of key genes involved in the Hypothalamic-Pituitary-Thyroid Axis (HPTA) and TH metabolism. Our results underscore for the first time an important synergistic toxic effect of these pollutants on embryonic development and thyroid morphology highlighting differences in the mechanisms through which they can adversely impact on multiple physiological processes of the HPTA and TH disposal influencing also heart geometry and function.

The Response of the Soil Microbiome to Contamination with Cadmium, Cobalt and Nickel in Soil Sown with Brassica napus

Soil fertility is determined by biological diversity at all levels of life, from genes to entire biocenoses. The aim of this study was to evaluate bacterial diversity in soil contaminated with Cd2+, Co2+ and Ni2+ and sown with Brassica napus. This is an important consideration because soil-dwelling microorganisms support phytoremediation and minimize the adverse effects of heavy metals on the environment. Microbial counts, the influence (IFHM) of Cd2+, Co2+ and Ni2+ on microorganisms, the colony development (CD) index, the ecophysiological diversity (EP) index and genetic diversity of bacteria were determined under controlled conditions. Soil contamination with Cd2+, Co2+ and Ni2+ significantly influenced microbial diversity and increased the values of CD and EP indices. The tested heavy metals decreased the genetic diversity of bacteria, in particular in the phyla Actinobacteria and Proteobacteria. Bacteria of the genera Arthrobacter, Devosia, Kaistobacter, Paenibacillus, Phycicoccus, Rhodoplanes and Thermomonas were identified in both contaminated and non-contaminated soil. These bacteria are highly resistant to soil contamination with Cd2+, Co2+ and Ni2+.

Soil cadmium mobilisation by dissolved organic matter from soil amendments

Dissolved organic matter (DOM) release from Cd contaminated soils been linked to mobilisation of the metal as Cd-DOM complexes and this may be exacerbated by organic matter-rich soil amendments. The quantity and quality of the DOM can determine the proportion of dissolved Cd that partitions to mobile complexes and their stability and, thus, the potential for Cd transport from contaminated soils. The aim of this work was to examine differences in Cd mobilisation from soils to which different types of soil amendments/conditioners have been applied and the importance of DOM characteristics in determining the extent to which this can happen. Three soils were spiked with Cd to 2 mg kg^-1, allowed to equilibrate and then treated with compost and peat. These soils and an untreated subsample of each soil were then adjusted to three different pHs: 5.6, 6.4 and 7.4, using lime. The amount of Cd mobilised from each soil was tested using a column leaching experiment. Ultrafiltration and speciation modelling were used to determine amounts of Cd as DOM-complexed, "truly" dissolved (<5 kDa) and colloidal species, while DOM quality was assessed using UV-Vis and fluorescence spectroscopy. Most colloidal Cd was mobilised from the compost treated soils (50%-60%), followed by the peat treated soils (20-44%). The relationships between colloidal Cd, DOC concentration and soil pH, together with the spectroscopic and modelling results showed that structural properties of DOM are an important factor in mobilising Cd from contaminated soils.

Occurrence, geochemical fraction, ecological and health risk assessment of cadmium, copper and nickel in soils contaminated with municipal solid wastes

Unscientific municipal solid waste (MSW) dumping provokes heavy metal (HM) associated ecological and human health hazards through heightened bioavailability and bioaccumulation. In this study, we focused on three important HMs Cadmium (Cd), Copper (Cu) and Nickel (Ni) and their geochemical fractions, to enable clutter free data management, analysis and interpretation. Stratified random soil sampling was carried out from twenty different locations around a Ramsar site (Deepor Beel) in Guwahati, India. The spatial concentration profiles of Cd, Cu and Ni were determined by data elicited from geochemical fractionation and the Geographic Information System (GIS). Ecological and health risks indices were used to evaluate the severity of soil pollution and assess the level of health risks. All the three HMs thus evaluated, conformed to the potential bioavailable category. Cd (54.59%) was associated mostly with the carbonate bound fraction (F3), while 25.53% of Cu and 40.60% Ni were associated with the exchangeable fraction (F2). Significant contamination levels and higher ecological risks posed by these metals were in the order Cd > Ni > Cu. Children were found to be more vulnerable towards Cd associated health risks whereas, Ni posed threats to both adults and children. Cu posed no risk to human health. Geochemical fractionation and different indices played a critical role in the integrated assessment of soil pollution, ecological and health risk assessment, and provided an empirical basis for the sustainable future planning and comprehensive adaptive management practices for MSW.

Influence of Cd on atrazine degradation and the formation of three primary metabolites in water under the combined pollution

To understand the influence of Cd on atrazine (ATZ) degradation in aqueous solution, the degradation of different initial levels of ATZ (0.1, 0.5, 1.0, and 2.0 mg·L^-1) was investigated in the presence and absence of Cd²⁺ in a 20-day laboratory experiment. It was found that Cd²⁺ caused a significant decrease in ATZ degradation and increased its half-life from 17-34 days to 30-57 days (p < 0.0001). Regarding the three most common metabolites of ATZ, deethylatrazine (DEA) and deisopropylatrazine (DIA) were detected in water earlier than hydroxyatrazine (HYA). The DEA content was several times higher than the DIA and HYA contents, regardless of the presence or absence of Cd²⁺. In the presence of Cd²⁺, the DIA content was significantly lower and the HYA content was significantly higher. Furthermore, Cd²⁺ had a dose-dependent effect on HYA formation. Our results indicated that the coexistence of Cd²⁺ and ATZ resulted in greater herbicide persistence, thereby possibly increasing the risk of environmental contamination. DEA was still the predominant ATZ degradation product detected in water under the combined pollution, which was similar to the ATZ tendency.

Cadmium-induced phytotoxicity and tolerance response in the low-Cd accumulator of Chinese cabbage (Brassica pekinensis L.) seedlings

In vegetable production, Chinese cabbage can readily accumulate cadmium (Cd) into its edible parts and exceed food safety standards. However, there are still some ecotypes that respond differently to cadmium stress. This study aimed to investigate the differences of Cd-induced (0, 10, 50, 100, 200 µM) response under hydroponic culture between two Chinese cabbage ecotypes which were promoted in northeastern China from the characteristics of biomass, uptake kinetic, accumulation, and initial oxidative stress. In this paper, it was confirmed that Jinfeng (JF) was a Cd-tolerant cultivar and had low Cd accumulation in edible part, while Qiutian (QT) was Cd-sensitive, exhibiting a faster Cd uptake rate but lacking effective Cd detoxication mechanisms, and was severely damaged by 10 µM Cd treatment. Conversely, even at a high Cd concentration of 200 µM, Jinfeng had weaker biomass inhibition, lower root Cd affinity, more difficult root-to-leaf translocation, and stronger antioxidant enzyme activity than Qiutian. In conclusion, Jinfeng can endure mild Cd stress (<10 µM), and Qiutian can be used as a Cd indicator. This study provides reliable materials and related data support for vegetable production in areas with mild Cd pollution.Novelty statement: This work further investigates the unique features of low-Cd accumulator in Chinese cabbage (Brassica pekinensis L.) seedlings as an interesting material for vegetable production in areas with mild Cd pollution. It also explains the differences between Cd-tolerant and Cd-sensitive cultivars under different cadmium stress levels and how these differences can alter their response. With the increase of Cd concentration, Cd-tolerant cultivars compared to Cd-sensitive cultivars showed less biomass decrease, lower accumulation, lower TF, more chemically stable Cd in roots and more active antioxidant enzymes under the same Cd stress level. With the development of seedlings, the uptake of Cd in roots and the translocation to the leaves were effectively restricted by the poor Cd affinity of roots, the conversion of Cd chemical forms and the promotion of antioxidase activities, in a Cd-tolerant low accumulator, Jinfeng.

Comparative Exposure Assessment of Potential Health Risks through the Consumption of Vegetables Irrigated by Freshwater/Wastewater: Gujranwala, Pakistan

The motive of this study is the rapid increase of industrial and domestic wastewater application for the growth of agricultural crops, which is closely associated with human health. In this study, the accumulation of eight heavy metals (Zn, Cu, Fe, Mn, Pb, Cr, Ni, and Cd) in the edible parts of five different species of common vegetables-cauliflower, bitter gourd, radish, pumpkin, and apple gourd-irrigated by two different water irrigation sources (wastewater/freshwater) grown in Pakistan's industrial and agricultural city Gujranwala and human health risks associated with the consumption of vegetables were evaluated. The mean concentration of each metal (Zn, Cu, Fe, Mn, Pb, Cr, Ni, and Cd) in five selected freshwater irrigated vegetables was observed as 48.91, 38.47, 133, 87.5, 4.62, 0.92, 1.46, and 0.36 mg/kg, respectively, while the mean concentration of each corresponding metal in wastewater irrigated vegetables was found to be 59.2, 49.5, 188, 90.9, 6.08, 2.66, 3.98, and 1.76 mg/kg, respectively. The estimated daily intake of metals (EDI), target health quotient (THQ), hazard index (HI), and target cancer risk (TCR) were computed to assess the impact of a raised level of metals in vegetables on human health. The grand THQ (G-THQ) values of individual freshwater irrigated vegetables were lower than the G-THQ values of individual wastewater irrigated vegetables and the G-THQ values of Cu, Cr, Pb, and Cd were found to be greater than the safety limit in wastewater irrigated vegetables. The HI values were found to be 7.94 and 4.01 for the vegetables irrigated with wastewater and freshwater, respectively. The TCR data reveal adverse carcinogenic risks induced by Ni, Cr, and Cd through the consumption of wastewater irrigated vegetables and Ni and Cd from the consumption of freshwater fed vegetables. The principal component analysis (PCA) to predict the sources of metals and Monte Carlo simulation were conducted to reduce the uncertainty in the data. The results indicate that higher significant health risks (carcinogenic and non-carcinogenic) would be posed to the adult population through the consumption of wastewater irrigated vegetables comparatively.

Biochemical metabolism of young plants of Ucuúba (Virola surinamensis) in the presence of cadmium

Virola surinamensis is a forest species widely distributed in the estuaries of the Amazon. These ecosystems are susceptible to contamination by Cadmium (Cd), indicating that the plant has strategies for tolerating this metal. The aim of this study was to assess the nitrogen and carbon metabolism of young plants of Ucuúba (Virola surinamensis) in the presence of cadmium with the perspective of the phytoremediation of contaminated environments. The used experimental design was a completely randomized design with five Cd concentrations (0, 15, 30, 45, and 60 mg L^- 1), for 60 days. In general, Cd did not affect nitrate concentration in the root but had a positive effect on leaves. The reduction of nitrate reductase (NR) in plants exposed to Cd was followed by a decrease in ammonia, total soluble amino acids (TSA), and total soluble proteins (TSP). Cd promoted an increase in the concentration of total soluble carbohydrates (TSC), proline, sucrose, and reducing sugars in the plants. The increase in TSC, sucrose and proline, suggests a metabolic regulatory mechanism of V. surinamensis against Cd stress.

Azolla incorporation under flooding reduces grain cadmium accumulation by decreasing soil redox potential

Cadmium (Cd) presents severe risks to human health and environments. The present study proposed a green option to reduce bioavailable Cd. Rice pot experiments were conducted under continuous flooding with three treatments (T1: intercropping azolla with rice; T2: incorporating azolla into soil before rice transplantation; CK: no azolla). The results showed that azolla incorporation reduced soluble Cd by 37% compared with the CK treatment, which may be explained by the decreased soil redox potential (Eh) (r = 0.867, P < 0.01). The higher relative abundance of Methylobacter observed in azolla incorporation treatment may account for dissolved organic carbon increase (r = 0.694; P < 0.05), and hence decreased the Cd availability for rice. Azolla incorporation increased the abundance of Nitrospira, indicating the potentially prominent role of nitrogen mineralization in increasing rice yields. Further, lower soluble Cd decreased the expression of OsNramp5, but increased OsHMA3 levels in rice roots, which decreased Cd accumulation in grains. Through these effects, azolla incorporation decreased Cd concentrations in rice grains by 80.3% and increased the production by 13.4%. The negligible amount of Cd absorbed by azolla would not increase the risk of long-term application. Thus, intercropping azolla with early rice and incorporating azolla into soil before late rice transplantation can contribute to safe production at large scales of double rice cultivation.

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.

Effects of foliar fungicide on yield, micronutrients, and cadmium in grains from historical and modern hard winter wheat genotypes

Plant breeding and disease management practices have increased the grain yield of hard winter wheat (Triticum aestivum L.) adapted to the Great Plains of the United States during the last century. However, the effect of genetic gains for seed yield and the application of fungicide on the micronutrient and cadmium (Cd) concentration in wheat grains is still unclear. The objectives of this study were to evaluate the effects of fungicide application on the productivity and nutritional quality of wheat cultivars representing 80 years of plant breeding efforts. Field experiments were conducted over two crop years (2017 and 2018) with eighteen hard winter wheat genotypes released between 1933 and 2013 in the presence or absence of fungicide application. For each growing season, the treatments were arranged in a split-plot design with the fungicide levels (treated and untreated) as the whole plot treatments and the genotypes as split-plot treatments in triplicate. The effects on seed yield, grain protein concentration (GPC), micronutrients, phytic acid, and Cd in grains were measured. While the yield of wheat was found to increase at annualized rates of 26.5 and 13.0 kg ha-1 yr-1 in the presence and absence of fungicide (P < 0.001), respectively, GPC (-190 and -180 mg kg-1 yr-1, P < 0.001), Fe (-35.0 and -44.0 μg kg-1 yr-1, P < 0.05), and Zn (-68.0 and -57.0 μg kg-1 yr-1, P < 0.01) significantly decreased during the period studied. In contrast to the other mineral elements, grain Cd significantly increased over time (0.4 μg kg-1 yr-1, P < 0.01) in the absence of fungicide. The results from this study are of great concern, as many mineral elements essential for human nutrition have decreased over time while the toxic heavy metal, Cd, has increased, indicating modern wheats are becoming a better vector of dietary Cd.

Reducing cadmium bioavailability and accumulation in vegetable by an alkalizing bacterial strain

Cadmium (Cd) contamination in agricultural soils is a widespread environmental problem that can affect food safety and human health. Effective remediation methods are needed to reduce Cd bioavailability in soil and Cd accumulation in food crops. In the present study, we isolated a Cd-resistant and alkalizing bacterium strain XT-4 from a Cd-contaminated soil and evaluated its potential application in Cd bioremediation. Based on its morphological, physiological and biochemical characteristics, together with 16S rRNA gene sequence analysis, strain XT-4 was identified as a member of the Bacillus genus. Strain XT-4 showed a strong ability to increase the pH and decrease Cd solubility in the medium. A greenhouse-based pot experiment with a Cd-contaminated soil was conducted to evaluate the effect of strain XT-4 inoculation on the growth and Cd accumulation of the vegetable Pak choi (Brassica rapa ssp. chinensis). Inoculation increased the rhizosphere pH, decreased CaCl₂-extractable Cd in the soil and decreased Cd concentration in the edible part of Pak choi by 28-40%. The results suggest that inoculation with alkalizing bacterial strain XT-4 represents an effective solution to increase rhizosphere pH and decrease Cd uptake by vegetable crops in Cd-contaminated acid soils.

Postnatal cadmium administration affects the presence and distribution of carbohydrates in the sperm membrane during maturation in the epididymis in adult Wistar rats

Cadmium (Cd) is a heavy metal related to a decrease in sperm parameters. The transit of spermatozoa through the epididymis is necessary to generate changes in the sperm membrane, such as the assembly of various carbohydrates that are added to the spermatazoan's surface to prepare it for successful fertilisation of the oocyte. No studies have yet analysed whether Cd alters the presence and distribution of these carbohydrates. We aimed to evaluate the changes induced by Cd in the distribution pattern of N-acetylglucosamine, sialic acid, mannose and fucose on the sperm membrane in the epididymis (e.g. caput, corpus, cauda) and if it alters the epididymal epithelium. Male Wistar pups were treated with Cd doses (0.125, 0.25 and 0.5mg/kg) on postnatal days 1-49. At postnatal day 90, they were humanely killed, sperm samples were obtained from the epididymis and tissue samples were taken for histological analysis. Cd concentrations in the blood and epididymis increased in proportion to the dose administered and decreased the serum testosterone levels and sperm quality. Histological analysis revealed alterations in the epithelium in all Cd-treated groups. Cd altered the distribution patterns of carbohydrates and fluorescence indices. All these alterations affected the structure and functioning of sperm.

Subsurface drip irrigation reduces cadmium accumulation of pepper (Capsicum annuum L.) plants in upland soil

Given that Cd pollution in dry land has aroused wide public concern, numerous remediation technologies has been utilized, yet there are limited cost-effective techniques that do not affect the original planting patterns. Fortunately, irrigation management can meet these requirements, while the effects of irrigation practices on Cd uptake by crops in slightly Cd-polluted upland soil remain elusive. Here, we aimed to investigate how the irrigation methods altered the Cd availability in soil, Cd accumulation in plants, microorganism population in soil, root morphology, and enzyme activities in soil and plants. We examined three irrigation treatments - surface drip irrigation (DI), subsurface drip irrigation (SDI), alternate-rows irrigation (ARI), and the control conventional furrow irrigation (CFI). The results showed that SDI remarkably reduced Cd content in roots, shoots and fruits, increased yield, and improved root growth and activity in soil of 20-40 cm compared to other treatments, though the Cd concentration in rhizosphere was not decreased significantly. The microbial population and enzyme activities in rhizosphere and enzyme activities in leaves and roots in SDI and ARI were basically higher than DI and CFI. Therefore, SDI has the prominent potential to reduce Cd uptake by crops in upland soil polluted with low Cd.

Cadmium toxicity in Salvia sclarea L.: An integrative response of element uptake, oxidative stress markers, leaf structure and photosynthesis

The herbal plant Salvia sclarea L. (clary sage) is classified to cadmium (Cd) accumulators and considered as a potential plant for phytoremediation of heavy metal polluted soil. However, the effect of Cd only treatment on the function of the photosynthetic apparatus of S. sclarea, as well as the mechanisms involved in Cd tolerance have not yet been studied in detail. This study was conducted to examine the integrative responses of S. sclarea plants exposed to a high Cd supply (100 µM) for 3 and 8 days by investigating element nutrient uptake, oxidative stress markers, pigment composition, photosynthetic performance and leaf structure. Measurements of the functional activities of photosystem I (PSI, by P700 photooxidation), photosystem II (PSII, by chlorophyll fluorescence parameters), the oxygen-evolving complex (oxygen evolution by Joliot- and Clark-type electrodes), as well as the leaf pigment and phenolic contents, were used to evaluate the protective mechanisms of the photosynthetic apparatus under Cd stress. Data suggested that the molecular mechanisms included in the photosynthetic tolerance to Cd toxicity involve strongly increased phenolic and anthocyanin contents, as well as an increased non-photochemical quenching and accelerated cyclic electron transport around PSI up to 61%, which protect the function of the photosynthetic apparatus under stress. Furthermore, the tolerance of S. sclarea to Cd stress is also associated with increased accumulation of Fe in leaves by 25%. All the above, clearly suggest that S. sclarea plants employ several different mechanisms to protect the function of the photosynthetic apparatus against Cd stress, which are discussed here.

A multiannual survey of cadmium content in pig tissues collected in the Czech Republic during the years 2015–2019

The assessment of cadmium content in the muscle, liver and kidneys of fattening pigs and sows was conducted in the Czech Republic during the period of 2015–2019. The samples were collected from a total of 32 sows and 210 fattening pigs. The mean cadmium content in the livers and kidneys of all sows was 0.102 ± 0.010 and 0.361 ± 0.032 mg·kg-1, respectively. The mean cadmium content in the livers and kidneys of all fattening pigs was 0.028 ± 0.001 and 0.141 ± 0.005 mg·kg-1, respectively. The maximum residual limit for human consumption was not exceeded in any sample. The cadmium content in the liver did not differ significantly between sows and fattening pigs in any particular year. In contrast, the cadmium content in kidneys differed significantly between sows and fattening pigs, being higher in sows (P < 0.05). No significant decreasing trend was observed for the cadmium content in tissues during the whole time period. It can be concluded that there is a need for further monitoring of the cadmium content in pig tissues in the Czech Republic.

Species-specific Cd-detoxification mechanisms in lumbricid earthworms Eisenia andrei, Eisenia fetida and their hybrids

Hermaphroditic lumbricid Eisenia sp. earthworms are ubiquitous and highly resistant to a variety of environmental stressors, including heavy metals. Among the progeny of laboratory mated inter-specific pairs of Eisenia fetida (Ea) and Eisenia andrei (Ef) there are fertile Ha hybrids derived from Ea ova fertilized by Ef spermatozoa and very rare sterile Hf hybrids from Ef ova fertilized by Ea spermatozoa. The aim of the first part of the experiment was to compare the life traits and whole body accumulation of cadmium in adult earthworms from genetically defined Ea, Ef and their hybrids (Ha) exposed for four weeks to commercial soil either unpolluted (control) or cadmium-spiked leading to moderate (M) or high (H) soil pollution (M = 425 and H = 835 mg kg^-1 dry soil weight). Such exposure impaired cocoon production but not affected earthworm viability despite the massive Cd bioaccumulation in the whole earthworm bodies reaching at M and H groups 316-454, 203-338, 114-253, and 377-309 mg kg^-1 dry body weights of Ea, Ef1, Ef2, and Ha, respectively, surprisingly reaching maximum accumulation quantities in hybrids. The second part of the experiment aimed to investigate cadmium-related defense mechanisms at transcriptomic level in coelomocytes non-invasively extruded from coelomic cavities of the new sets of Ea, Ef, Ha, and Hf earthworms exposed to Cd in microcosms for 0 days (control), 2 days, and 7 days (M = 425 mg kg^-1). Expression level of stress-induced Cd-metallothionein (mt) and superoxide dismutase (sod) were gradually up-regulated, while the immune-connected lysenin (lys) was rapidly down-regulated; the expression of glutathione S-transferase (gst) and phytochelatin synthase (pcs) remained unaffected. Mt and sod gene up-regulation and lys gene down-regulation were especially pronounced in Ea-derived hybrids. In sum, capacity of cadmium bioaccumulation and detoxification mechanisms is more efficient in interspecific hybrids than in the pure Ea and Ef species.

Compost application increases the ecological dose values in a non-calcareous agricultural soil contaminated with cadmium

Soil cadmium (Cd) pollution resulting from anthropogenic activities has become a major concern for microbial and biochemical functions that are critical for soil quality and ecosystem sustainability. Organic amendments can reduce Cd toxicity to the microbial community and enzymatic activity in Cd-polluted soils and thus would increase the ecological dose (ED) values. However, there has been less focus on the effect of organic amendments on microbial and biochemical responses to Cd toxicity in non-calcareous soils using the concept ED. The aim of this study was to assess the impact of compost application on microbial activity, microbial biomass, turnover rates of carbon and nitrogen, and enzymatic activities as the key ecological functions in a non-calcareous soil spiked with different Cd concentrations (0-200 mg kg^-1). Results showed that soil amendment with compost decreased Cd availability by 48-76%, depending on the total soil Cd content. The application of compost reduced the negative influence of Cd eco-toxicity on most soil microbial and biochemical functions by 20-122%, depending on the Cd level and the assay itself. The ED values, derived from the sigmoidal dose-response and kinetic models, were 1.10- to 2.24-fold higher in the compost-amended soils than the unamended control soils at all Cd levels. In conclusion, the potential risks associated with high levels of Cd pollution can be alleviated for microbial and biochemical indicators of soil quality/health with application of 2500 kg ha^-1 compost as a cost-effective source of organic matter to non-calcareous soils. The findings would have some useful implications for organic matter-limited non-calcareous soils polluted with Cd.

Detection of Cadmium Toxicity in Plant

Cadmium (Cd) is widespread in the soil, water, and atmosphere, so Cd toxicity to human can happen by breathing in air, drinking water, and eating food from plant grown in Cd-contaminated soil. Cd pollution draws a lot of attention from the scientific community and also regulatory agents and is researched widely by using both plant and animal system. In this protocol, the detection of cadmium (Cd) is described in soil and mature maize (Zea mays) plant with the atomic absorption spectrometer. The Cd uptake, translocation factor, and Cd health risk index are also introduced. The protocol can be modified slightly to measure Cd in different types of plants.

Effects of composited organic mobilizing agents and their application periods on cadmium absorption of Sorghum bicolor L. in a Cd-contaminated soil

Organic mobilizing agents have been advocated for phytoremediation of heavy metals contaminated soils, while the effects of application period of such agents remain unclear. A pot experiment was conducted, with two composited organic agents (oxalic acid or citric acid + dissolved organic fertilizer (OA + DOF and CA + DOF)) and four application periods (seeding, jointing, flag leaf and heading stages) of sorghum (Sorghum bicolor L.), to investigate their impacts on Cd bioavailability in soil. Results indicated that application of the two composited agents increased soil dissolved organic carbon (DOC) and DTPA extractable Cd by 7.31-49.13%, Cd contents in roots and shoots by 21.49-72.10%, bioaccumulation factor (BCF) and translocation factor (TF) of shoots by 4.44-71.99%, while reduced soil pH by 0.25-0.53 units, respectively. Most of these indices increased with the application periods, and largely peaked with their application during the flag leaf to heading stages. Meanwhile, the maximum sorghum biomass (132.84 g pot^-1) and Cd bioaccumulation quantity (BCQ, 0.71 mg pot^-1) in shoots were obtained for the CA + DOF applied at the heading. The DTPA extractable Cd was closely related to soil pH and DOC. Similar close relationships were observed between the Cd contents in shoots and soil DTPA extractable Cd, pH and DOC. The BCQ of Cd was positively related to the shoots biomass rather than their Cd contents. Therefore, the sorghum combined with the CA + DOF may be advocated as an alternative phytoremediation mode in Cd-contaminated soils, and the mobilizing agent should be primarily applied at the heading stage.

Distribution, contamination status and source of trace elements in the soil around brick kilns

This study reports the distribution, contamination level, and possible sources of 54 metal (oid)s in the soils found around brick kilns in south-western Bangladesh. In total, 40 soil samples were collected from the vicinity of five brick kilns in four directions at 250 m intervals. This study reveals that the mean respective concentrations of caesium (Cs), beryllium (Be), lead (Pb), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), dysprosium (Dy), holmium (Ho), terbium (Tb), erbium (Er), thulium (Tm), ytterbium (Yb), thorium (Th), germanium (Ge), yttrium (Y), zirconium (Zr), niobium (Nb), silver (Ag), hafnium (Hf), tantalum (Ta), and tungsten (W), were 7.83, 3.19, 22.93, 85.93, 9.61, 36.86, 7.30, 1.23, 5.76, 1.13, 0.99, 3.14, 0.45, 2.91, 17.72, 3.04, 30.07, 185.13, 13.99, 0.30, 5.34, 1.26, and 2.61 μg g^-1. Furthermore, those amounts exceeded their respective shale values. The pollution evaluation indices indicated a moderate level of contamination by Cs, Pb, Th, Ag, Hf, Ta, W, and lanthanides but excluding lanthanum (La) and lutetium (Lu). The pollution load index revealed pollution at two brickfields. Multivariate statistics reported that coal combustion in the brick kilns is the primary source of lanthanides, actinides, Y, Zr, and Hf in the soil, while other elements derived mostly from natural sources. A portion originated from coal combustion in brick kilns and agricultural activities. Changes in metal (oid)s concentrations were non-linear with the distance between the kilns and sampling points. Consequently, further studies are required and should consider meteorological factors and severity of human impact in the study area.

A field study to predict Cd bioaccumulation in a soil-wheat system: Application of a geochemical model

An accurate model to predict Cd accumulation in crops based on soil properties would facilitate evaluations of soil quality and the potential risk posed by metals. However, given the heterogeneity of soil, such models are difficult to establish on large regional scales. This study for the first time examined the applicability of a multi-surface speciation model (MSM) in predicting Cd accumulation in wheat at a regional field scale, based on 140 soil-wheat paired samples collected from a 205-km² field. The MSM resulted in a better correlation between Cd accumulation in wheat grain (R² = 0.75) and roots (R² = 0.74) than obtained with chemical extraction methods (total Cd in soil, 0.01 M CaCl₂, and 0.43 M HNO₃). In addition, while the performance of the MSM was comparable to that of a traditional multiple regression model, a parameter-fitting process was not required. The predictive ability of the MSM was further used to assess and predict the soil Cd risk and to develop a soil Cd sensitivity map to better localize areas of greatest sensitivity to Cd contamination. The results showed that the MSM can serve as a useful tool for regional soil risk assessments and thus in the development of soil protection measures.

Autophagy: a necessary defense against extreme cadmium intoxication in a multigenerational 2D experiment

Autophagy is a natural process that aims to eliminate malfunctioning cell parts, organelles or molecules under physiological conditions. It is also induced in response to infection, starvation or oxidative stress to provide energy in case of an energy deficit. The aim of this 2-dimensional study was to test if, and if so, how, this process depends on the concentration of cadmium in food (with Cd concentrations from 0 to 352 μg of Cd per g of food (dry weight)-D1 dimension) and the history of selection pressure (160 vs 20 generations of exposure to Cd-D2 dimension). For the study, the 5th instar larvae of a unique strain of the moth Spodoptera exigua that was selected for cadmium tolerance for 160 generations (44 μg of Cd per g of food (dry weight)), as well as 20-generation (11, 22 and 44 μg of Cd per g of food (dry weight)) and control strains, were used. Autophagy intensity was measured by means of flow cytometry and compared with life history parameters: survivability and duration of the 3rd larval stage. The highest values of autophagy markers were found in the groups exposed to the highest Cd concentration and corresponded (with a significant correlation coefficient) to an increased development duration or decreased survivorship in the respective groups. In conclusion, autophagy is probably initiated only if any other defense mechanisms, e.g., antioxidative mechanisms, are not efficient. Moreover, in individuals from pre-exposed populations, the intensity of autophagy is lower.

Enrichment of cadmium in rice (Oryza sativa L.) grown under different exogenous pollution sources

In order to unravel the cadmium (Cd) enrichment patterns in rice (Oryza sativa L.) grown under different exogenous exposure pathways, the pot experiment was conducted in a greenhouse. Cd was added to the soil-rice system via mixing soil with Cd-containing solution, irrigating the pots with Cd-containing water and leaf-spraying with Cd solution to simulate soil pollution (SPS), irrigation water pollution (IPS), and atmospheric deposit pollution sources (APS), respectively. No significant (p > 0.05) differences in plant height and rice grain yield were observed among all treatments including three different Cd pollution sources and control. The contents of Cd in rice plants significantly (p < 0.05) increased with increase in Cd concentrations in three pollution sources. The distribution pattern of Cd in the rice plant organs treated with SPS and IPS followed the order: roots > stems > leaves > husk > brown rice, while it was leaves > roots > stems > husk > brown rice treated with APS. At the same level of treatment, the highest concentration of Cd was observed in rice organs (except for middle and high concentrations treatment roots) grown under APS, followed by IPS and SPS, suggesting that the Cd bioavailability from different pollution sources followed the order of APS > IPS > SPS. It is concluded that the atmospheric pollution contributed more enrichment of rice with Cd. Therefore, in field environment, air deposits should also be analyzed for toxic metals during assessment of food chain contamination and health risk.

Mitigation of Nickel Toxicity and Growth Promotion in Sesame through the Application of a Bacterial Endophyte and Zeolite in Nickel Contaminated Soil

Nickel (Ni) bioavailable fraction in the soil is of utmost importance because of its involvement in plant growth and environmental feedbacks. High concentrations of Ni in the soil environment, especially in the root zone, may retard plant growth that ultimately results in reduced plant biomass and yield. However, endophytic microorganisms have great potential to reduce the toxicity of Ni, especially when applied together with zeolite. The present research work was conducted to evaluate the potential effects of an endophytic bacterium Caulobacter sp. MN13 in combination with zeolite on the physiology, growth, quality, and yield of sesame plant under normal and Ni stressed soil conditions through possible reduction of Ni uptake. Surface sterilized sesame seeds were sown in pots filled with artificially Ni contaminated soil amended with zeolite. Results revealed that plant agronomic attributes such as shoot root dry weight, total number of pods, and 1000-grains weight were increased by 41, 45, 54, and 65%, respectively, over control treatment, with combined application of bacteria and zeolite in Ni contaminated soil. In comparison to control, the gaseous exchange parameters (CO₂ assimilation rate, transpiration rate, stomatal- sub-stomatal conductance, chlorophyll content, and vapor pressure) were significantly enhanced by co-application of bacteria and zeolite ranging from 20 to 49% under Ni stress. Moreover, the combined utilization of bacteria and zeolite considerably improved water relations of sesame plant, in terms of relative water content (RWC) and relative membrane permeability (RMP) along with improvement in biochemical components (protein, ash, crude fiber, fat), and micronutrients in normal as well as in Ni contaminated soil. Moreover, the same treatment modulated the Ni-stress in plants through improvement in antioxidant enzymes (AEs) activities along with improved Ni concentration in the soil and different plant tissues. Correlation and principal component analysis (PCA) further revealed that combined application of metal-tolerant bacterium Caulobacter sp. MN13 and zeolite is the most influential strategy in alleviating Ni-induced stress and subsequent improvement in growth, yield, and physio-biochemical attributes of sesame plant.

The new fertilizer regulation: A starting point for cadmium control in European arable soils?

Bioaccumulation of cadmium (Cd) in the agricultural soil constitutes a dangerous risk for the health of both the environment and humans. Especially in the European Union, a large amount of Cd in agricultural topsoil originates from mineral fertilizer application. In this context, the EU has recently adopted the Regulation (EU) 2019/1009 with the aim to establish stricter limits for Cd presence in fertilizer products and to promote a higher use of fertilizers from organic sources. This paper discusses the future implications of the new regulation to limit the presence of cadmium (Cd) in agricultural soils and food products. The Regulation (EU) 2019/1009 represents an important step of the EU circular economy action plan with its aim to encourage the production of low cadmium content fertilizers. This paper focuses on the limits of the Regulation (EU) 2019/1009 and on the need for complementary policy instruments to protect and conserve agricultural soil health. We highlight the recently proposed, and subsequently withdrawn, EU Soil Framework Directive (SFD) as a meaningful complementary policy tool in the context of a renewed effort to pursue protection and conservation of soil health.

Effects of Soil Amendments on Heavy Metal Immobilization and Accumulation by Maize Grown in a Multiple-Metal-Contaminated Soil and Their Potential for Safe Crop Production

Soil amendments have been proposed for immobilizing metallic contaminants, thus reducing their uptake by plants. For the safe production of crops in contaminated soil, there is a need to select suitable amendments that can mitigate heavy metal uptake and enhance crop yield. The present experiment compared the effects of three amendments, hydroxyapatite (HAP), organic manure (OM), and biochar (BC), on plant growth and heavy metal accumulation by maize in an acidic soil contaminated with Cd, Pb, and Zn, and their potential for safe crop production. Toxicity characteristic leaching procedure (TCLP) tests, energy dispersive X-ray spectroscopy (EDS) analysis, and X-ray diffraction (XRD) analysis were used to evaluate the effectiveness and mechanisms of heavy metal immobilization by the amendments. The results showed that shoot and root biomass was significantly increased by HAP and 1% OM, with an order of 1% HAP > 0.1% HAP > 1% OM, but not changed by 0.1% OM and BC (0.1% and 1%). HAP significantly decreased Cd, Pb, and Zn concentrations in both shoots and roots, and the effects were more pronounced at the higher doses. OM decreased the shoot Cd and Pb concentrations and root Zn concentrations, but only 1% OM decreased the shoot Zn and root Pb concentrations. BC decreased the shoot Cd and Pb concentrations, but decreased the shoot Zn and root Pb concentrations only at 1%. HAP decreased the translocation factors (TFs) of Cd, Pb, and Zn (except at the 0.1% dose). OM and BC decreased the TFs of Cd and Zn, respectively, at the 1% dose but showed no significant effects in other cases. Overall, plant P, K, Fe, and Cu nutrition was improved by HAP and 1% OM, but not by 0.1 OM and BC. Soil pH was significantly increased by HAP, 1% OM, and 1% BC, following an order of 1% HAP > 1% OM > 0.1% HAP > 1% BC. The TCLP levels for Cd, Pb, and Zn were significantly reduced by HAP, which can be partly attributed to its liming effects and the formation of sparingly soluble Cd-, Pb-, and Zn-P-containing minerals in the HAP-amended soils. To some extent, all the amendments positively influenced plant and soil traits, but HAP was the optimal one for stabilizing heavy metals, reducing heavy metal uptake, and promoting plant growth in the contaminated soil, suggesting its potential for safe crop production.

Cadmium Stress Reprograms ROS/RNS Homeostasis in Phytophthora infestans (Mont.) de Bary

Heavy metal pollution causes many soils to become a toxic environment not only for plants, but also microorganisms; however, little is known how heavy metal contaminated environment affects metabolism of phytopathogens and their capability of infecting host plants. In this study the oomycete Phytophthora infestans (Mont.) de Bary, the most harmful pathogen of potato, growing under moderate cadmium stress (Cd, 5 mg/L) showed nitro-oxidative imbalance associated with an enhanced antioxidant response. Cadmium notably elevated the level of nitric oxide, superoxide and peroxynitrite that stimulated nitrative modifications within the RNA and DNA pools in the phytopathogen structures. In contrast, the protein pool undergoing nitration was diminished confirming that protein tyrosine nitration is a flexible element of the oomycete adaptive strategy to heavy metal stress. Finally, to verify whether Cd is able to modify P. infestans pathogenicity, a disease index and molecular assessment of disease progress were analysed indicating that Cd stress enhanced aggressiveness of vr P. infestans towards various potato cultivars. Taken together, Cd not only affected hyphal growth rate and caused biochemical changes in P. infestans structures, but accelerated the pathogenicity as well. The nitro-oxidative homeostasis imbalance underlies the phytopathogen adaptive strategy and survival in the heavy metal contaminated environment.

Effect of Biowastes on Soil Remediation, Plant Productivity and Soil Organic Carbon Sequestration: A Review

High anthropogenic activities are constantly causing increased soil degradation and thus soil health and safety are becoming an important issue. The soil quality is deteriorating at an alarming rate in the neighborhood of smelters as a result of heavy metal deposition. Organic biowastes, also produced through anthropogenic activities, provide some solutions for remediation and management of degraded soils through their use as a substrate. Biowastes, due to their high content of organic compounds, have the potential to improve soil quality, plant productivity, and microbial activity contributing to higher humus production. Biowaste use also leads to the immobilization and stabilization of heavy metals, carbon sequestration, and release of macro and micronutrients. Increased carbon sequestration through biowaste use helps us in mitigating climate change and global warming. Soil amendment by biowaste increases soil activity and plant productivity caused by stimulation in shoot and root length, biomass production, grain yield, chlorophyll content, and decrease in oxidative stress. However, biowaste application to soils is a debatable issue due to their possible negative effect of high heavy metal concentration and risks of their accumulation in soils. Therefore, regulations for the use of biowastes as fertilizer or soil amendment must be improved and strictly employed to avoid environmental risks and the entry of potentially toxic elements into the food chain. In this review, we summarize the current knowledge on the effects of biowastes on soil remediation, plant productivity, and soil organic carbon sequestration.