Soil Cadmium Concentration Research Articles

Influencing Factors of Cadmium Content in Wheat Grain: A Meta-analysis and Decision Tree Analysis

Rapid urbanization, industrialization, and agricultural intensification have resulted in serious soil problems, such as soil acidification and cadmium pollution, affecting food security and human health. Wheat is the second largest food crop in China and has a strong accumulation capacity for cadmium. Understanding the influencing factors of cadmium content in wheat grain is crucial to realize the safe production of wheat. However, a comprehensive and quantitative analysis of how soil physicochemical properties and cultivars affect wheat cadmium accumulation is lacking. The Meta-analysis and decision tree analysis of 56 related studies published in the past 10 years showed that the proportion of cadmium content in soil and wheat grain exceeding the national standard was 52.6% and 64.1%, respectively. Among soil physical and chemical properties, pH, organic matter, available phosphorus, and total soil cadmium content were the important factors affecting the cadmium content in wheat grains. When soil pH ≤ 5.5 and 5.5<pH ≤ 6.5, the proportion of cadmium content in wheat grain exceeding the national standard was 99.4% and 76.2%, respectively. When 20 g·kg-1<soil organic matter content ≤ 30 g·kg-1, the proportion of cadmium content in wheat grain exceeding the national standard was the highest (61.0%). Soil pH ≥ 7.1 and total cadmium content <1.60 mg·kg-1 was suitable for wheat safety production. There were significant differences in grain cadmium content and cadmium enrichment factors among different wheat cultivars. Planting wheat cultivars with low cadmium accumulation is an economical and effective measure to decrease cadmium content in wheat grains. The current study can provide guidance for the safe production of wheat in cadmium-contaminated farmland.

Effect of Modified Illite on Cd Immobilization and Fertility Enhancement of Acidic Soils

Cadmium pollution in the soil induces significant hazards to agricultural growth and public health. Therefore, new routes are needed to develop low-cost soil amendments that can effectively stabilize cadmium and improve soil fertility. This study introduces modified illite (MIT) with the enhanced ability to stabilize heavy metal Cd through the mixing of illite with calcium carbonate, silicate and sulfate in specific proportions by using the well-known calcination-hydrothermal process. The characterization findings revealed that the modified MIT is predominantly composed of gehlenite and akermanite, with greatly improved specific surface area, pore structure and cation exchange capacity. The main purpose of the present study is to unravel a plausible mechanism on how MIT can stabilize Cd(II) in the soil and to investigate the effect of MIT on the fertility of the contaminated soil. Experiments on soil remediation revealed that MIT has a more profound stabilizing impact on Cd(II) compared to natural illite, resulting in a 22.84% reduction in acid-soluble Cd of the soil when MIT was dosed at 0.5%. The potential mechanism of Cd(II) immobilization by MIT involves the ionic exchange of Cd2+ with the exchangeable Ca2+ and Mg2+. In addition, the hydrolysis products of gehlenite and akermanite are prone to form silicate precipitates with free Cd, leading to soil pH increment. The pot experiments showed that MIT significantly reduces the cadmium content of soil and improves the growth of water spinach organs. Meanwhile, enhancement of the indicators in rhizosphere soil further proved that MIT effectively increases the nutrient content, improves the soil structure and promotes microorganism growth.

Human Health and Ecological Risks Associated with Total and Bioaccessible Concentrations of Cadmium and Lead in Urban Park Soils.

This study investigated the total and bioaccessible concentrations of cadmium (Cd) and lead (Pb) in urban soils and their associated human health and ecological risk. Total and bioaccessible metal concentrations were found within the safe limits except for Cd, surpassing the State Environmental Protection Administration (SEPA) China limit in 9.5% of parks. Bioaccessible concentrations were higher in the gastric (G) phase than the intestinal (I) phase, while Cd showed more bioaccessibility compared to Pb. Bioaccessible concentrations reduced Hazard Quotient (HQing) values by 2-22 times and 0-2 times for children and adults, respectively, while hazard index (HI) declined by 1.7 times, and the mean total bioaccessible risk of Pb decreased by 20.8 times. Further, the study revealed a low level of contamination factor (CF < 1) and a low degree of contamination (CD < 6), and Potential Ecological Risk Index (PERI) values for all the cities were less than 150, indicating low ecological risk.

Bioaccumulation of Pb, Cd and As by Euphorbia prostrata growing in sites having different contamination levels

ABSTRACT Many rural people in developing countries rely on herbal remedies, but these derive from plants which may be subject to heavy metal pollutants. Lead, cadmium and arsenic are confirmed carcinogens and may produce toxic effects if present above the recommended levels in medicinal herbs. The study assessed the uptake and associated health risk of Pb, Cd and As by Euphorbia prostrata exposed to different contaminating sources. The levels of Pb were within safe limits of the World Health Organization both in soil (200 mg/kg) and plant (10 mg/kg). Cadmium concentration in soil from all sites exceeded the allowable range (0.6 mg/kg), exceeding the safe permissible limit of 0.3 mg/kg in plants growing in contaminated sites. E. prostrata and other medicinal herbs growing in polluted sites should not be used therapeutically.

Effect of Thermal Activation Temperature of Nanoscale Phosphate and Silicate on the Morphological Transformation Characteristics of Cd in Heavy Metal Contaminated Soils

Purpose. The problem of heavy metal Cd pollution in the soil is still very serious. The widely used treatment measure is in situ passivation chemical remediation technology. Some studies have shown that the single application of phosphate or silicate can control soil cadmium pollution, but few studies have been conducted on the effect of the thermal activation temperature of nano phosphate and silicate-combined application on the transformation of Cd form in the soil. Materials and methods. Cadmium-contaminated soil was indoor-simulated, after which the 2.0% soil-weight dose of potassium dihydrogen phosphate was mixed with thermal activation nano serpentine or nano zeolite (potassium dihydrogen phosphate: thermal activation nano serpentine or nano zeolite = 1:2) at different temperatures (0, 350, 550, 700, 850 °C) and compared with the simulated cadmium-contaminated soil without adding a mixture of phosphate and silicate; cadmium content in soil was determined by Tessier five-step continuous extraction method after incubating for 0, 7, 14, 28, and 56 d in jars in the constant-temperature box. Results and discussion. Thermal activation temperature of nano phosphate and silicate could reduce the amount of exchangeable Cd content in the soil to a different degree; the content of Cd in carbonate-bound form, Fe–Mn–oxide-bound form, organically-bound form, and residual form increased. The order of effect of nanoscale potassium dihydrogen phosphate and serpentine or zeolite thermal activation temperature on remediation of Cd contaminated soil is nPS700-2.0 &gt; nPS550-2.0 &gt; nPS850-2.0 &gt; nPS350-2.0 &gt; nPS0-2.0, nPF700-2.0 &gt; nPF550-2.0 &gt; nPF850-2.0 &gt; nPF350-2.0 &gt; nPF0-2.0 (n, P, S, and F represent nanometer, KH2PO4, serpentine, and zeolite, respectively; 0, 350, 550, 700, and 850 represent different activation temperatures T); 700 °C treatments performed better than other thermal activation temperature treatments, and nPS700-2.0 was better than nPF700-2.0. Conclusion. Thermal activation temperature of nano phosphate and silicate-combined application can stabilize heavy metal Cd to some extent and promote the transition of Cd from a bioavailable state to a biounavailable state. The results showed that the combined application of thermal activation temperature of nano phosphate and silicate has a certain potential to control soil cadmium pollution.

Combined Effects of Biochar-Sedum plumbizincicola on Cadmium Concentration in Cd-Contaminated Limestone Soil and Cadmium Absorption in Lactuca sativa

Combined Effects of Biochar-Sedum plumbizincicola on Cadmium Concentration in Cd-Contaminated Limestone Soil and Cadmium Absorption in Lactuca sativa

Prediction of the concentration of cadmium in agricultural soil in the Czech Republic using legacy data, preferential sampling, Sentinel-2, Landsat-8, and ensemble models

The current study assesses and predicts cadmium (Cd) concentration in agricultural soil using two Cd datasets, namely legacy data (LD) and preferential sampling-legacy data (PS-LD), along with four streams of auxiliary datasets extracted from Sentinel-2 (S2) and Landsat-8 (L8) bands. The study was divided into two contexts: Cd prediction in agricultural soil using LD, ensemble models, 10 and 20 m spatial resolution of S2 and L8 (context 1), and Cd prediction in agricultural soil using PS-LD, ensemble models and 10 and 20 m spatial resolution of S2 and L8 (context 2). In context 1, ensemble 1, L8 with PS-LD was the cumulative optimal approach that predicted Cd in agricultural soil with a higher R2 value of 0.76, root mean square error (RMSE) of 0.66, mean absolute error (MAE) of 0.35, and median absolute error (MdAE) of 0.13. However, with R2 = 0.78, RMSE = 0.63, MAE = 0.34, and MdAE = 0.15, ensemble 1, S2 of PS-LD was the best prediction approach in predicting Cd concentration in agricultural soil in context 2. Overall, the predictions from both contexts indicated that ensemble 1 of S2 combined with PS-LD was the most appropriate and best model for Cd prediction in agricultural soil. The modeling approaches' uncertainty in both contexts was assessed using ensemble-sequential gaussian simulation (EnSGS), which revealed that the degree of uncertainty propagated in the study area was within 5% in both contexts. The combination of the PS dataset and the LD along with ensemble models and the remote sensing dataset, produced promising results. Nonetheless, the results demonstrated that the 20 m spatial resolution band dataset used in the prediction of Cd in agricultural soil outperformed the 10 m spatial resolution. When PS is combined with LD, an appropriate modeling approach, and a well-correlated remote sensing dataset are used, good results are obtained.

Effects of pH on Available Cadmium in Calcareous Soils and Culture Substrates

Abstract The effect of pH on available Cd in calcareous soils and culture substrate was studied by adding exogenous Cd and artificially adjusting the pH to create different pH conditions. It is expected to provide reference for the control of Cd pollution by adjusting pH. The cadmium chloride was added to the calcareous soil and culture substrate to make the total cadmium content 1.0 mg kg–1. The pH of soil and substrate was adjusted, and then the available cadmium content in soil and cultivation substrate was detected under different pH conditions. The content of available Cd in calcareous soil decreased with increasing pH in the range of pH 3.40 to 8.97, showing a significant negative correlation. At a pH range of 3.03 to 4.37, the available Cd content in the culture substrate increased significantly with increasing pH, while the available Cd content in the culture substrate at a pH range of 4.37 to 9.47 was not significantly different.

Impact of soil types and root exudates on cadmium and petroleum hydrocarbon phytoremediation by Sorghum sudanense, Festuca arundinace, and Lolium perenne

With the development of industrialization, soils around the world have been polluted by heavy metals and oil to different degrees in recent years, and soil remediation has become a global problem. Phytoremediation has a wide application prospect because of its environmental friendliness and easy availability of materials.ObjectiveTo explore the effects of soil types and root exudates on the removal of cadmium and petroleum hydrocarbon in soils.MethodA pot experiments with three soil types (sandy, loamy and clayey) of the Changning-Weiyuan area of Sichuan province and three root exudates (citric acid, glycine, and maltose) were carried out using Sorghum sudanense (Piper) Stapf., Lolium perenne L., and Festuca arundinacea L. as test materials. Plants were grown in soils contaminated by cadmium and petroleum at different concentrations.ResultThe biomass of S. sudanense, the translocation ratio and removal rate of cadmium in S. sudanense decreased gradually with increasing soil cadmium concentration. The promotion effects of the three root exudates on S. sudanense were in the following order: citric acid &amp;gt; glycine &amp;gt; maltose. At the same cadmium pollution conditions, the biomass levels of S. sudanense in sandy, loamy, and clayey soils were in the following order: clayey soil &amp;gt; loamy soil &amp;gt; sandy soil. On the contrary, the concentration, translocation ratio, and removal rate of cadmium in S. sudanense grown in the different soils treated with root exudates were in the following order: sandy soil &amp;gt; loamy soil &amp;gt; clayey soil. Under the three soil conditions, the fresh weight of F. arundinacea (0.36 ~ 0.68 g) and S. sudanense (0.51 ~ 0.99 g) increased significantly (p &amp;lt; 0.05). The total petroleum hydrocarbons degradation efficiencies of F. arundinacea, L. perenne, and S. sudanense were high in sandy soil (34.27% ~ 60.52%). Changing the type of root exudate had a significant impact on the degradation of total petroleum hydrocarbons in sandy soil (p &amp;lt; 0.05).ConclusionThis study showed that soil types impacted the accumulation of cadmium and petroleum in plants. Phytoremediation of cadmium and petroleum contaminated soil could be enhanced by the application of root exudates. This study recommend that the method is suitable for field remediation of soils contaminated with mild cadmium and petroleum hydrocarbons.

Heavy Metals Concentration In Soils And Bioaccumulation In Earthworm (Lumbricus Terrestris) At Lemna Solid Wastes Dumpsite, Calabar, Cross River State

This study investigated the concentrations of heavy metals and their bioaccumulation in earthworm in Lemna solid wastes dumpsite in Calabar, Cross River State, Nigeria. Three composite samples of the depth of 30 cm each were collected from Lemna dumpsites and control from the University of Calabar Botanical garden, making a total of four composite soil samples, while samples of earthworms were collected at each sampling point. The samples were analysed for Pb, Cd, Zn and Cu. The result showed that the levels of heavy metals were all higher in dumpsite and significantly different from the control. The respective means of metal concentrations from both Lemna and control were Pb(323.99mg/kg , 89.88mg/kg), Cd(1.12 mg/kg, 0.072 mg/kg), Zn(281 mg/kg, 7.60 mg/kg) and Cu(21.58 mg/kg, 4.89 mg/kg). Pb, Cd, Zn and Cu were also higher in earthworm of dumpsite than earthworm of the control soil. Correlation between Cadmium and Zinc concentration in soil and Cadmium and Zinc concentration in earthworm displayed strong and positive relationship while weak and negative correlation was observed between Cu and Pb concentrations in soil and Cu and Pb concentrations in earthworm. Bioaccumulation of the heavy metals by earthworm was in the order of Zn (0.382) &gt; Cd (0.170) &gt; Pb (0.076) &gt; Cu (0.020). The dumpsite soil was found to be contaminated with Cd, Pb and Zn as their concentrations were high above maximum permissible limits except Cu. For safe consumption of crops from Lemna dumpsite soil, remediation of heavy metals in the soil in advocated.

Accumulation Detection of Cadmium in some land-use soil of Baghdad city, Iraq

This study aims to detect cadmium accumulation in the soil of Baghdad. Twenty soil samples were collected randomly during November 2020 to cover the study area, emphasizing the nature of each area (agricultural, commercial, industrial, residential, roadside, and waste dumping sites). All soil samples were subjected to geochemical analysis using atomic absorption spectrometry (ASS) to determine the concentration of cadmium in Baghdad soil. The laboratory data was utilized to design the spatial analysis map using Arc GIS 10.4.1 to investigate the spatial distribution of cadmium. The results demonstrated that the total content of cadmium in the study area ranged from 0.121to 1.78 mg/kg. All results of cadmium concentrations are within the allowable limits of WHO (3 mg/kg), and the mean concentration of cadmium according to the type of land use is shown by the following decreasing order: roadside &gt; agricultural areas &gt; residential areas &gt; industrial areas &gt;waste dumping site&gt; commercial. In addition, the spatial analysis map showed the accumulation of cadmium concentration on the Al-Karkh side than on the Al-Rissafa side of Baghdad city. A comparison between cadmium concentration in the soil of some land- use for the current study and cadmium concentration in previous studies showed that the concentration of cadmium decreased from previous years, except roadside sites recorded a higher cadmium concentration than the cadmium concentration of roadside areas according to [12].

APPROACHES TO RISK ASSESSMENT ASSOCIATED WITH SOIL CONTAMINATION IN URBAN AREAS (BASED ON FOREIGN EXPERIENCE)

Environmental risk assessment associated with soil contamination is one of the most important elements of effective management of contaminated sites, since it allows to identify the most important intake routs of contaminates to the human organism and to determine the risk of soil contamination in terms of impact on human health. The territories of industrial enterprises that are а subject to development and transformation into urban landscapes deserve special attention in cities.&#x0D; Methodological approaches to hazard assessment due to soil contamination based on the concept of risk to public&#x0D; health are analyzed. Models CalTOX, USETox, MMSoils, 3MRA, SADA and others that are developed and used in foreign countries, are characterized.&#x0D; It is shown that the SADA model has the maximum advantage for the practical application in Belarus due to its availability and built-in GIS technologies, which make it possible to obtain a visual indicative picture of the risks distribution.&#x0D; The SADA model has been tested for a post-industrial site located in Minsk, subject to use as a residential area. The&#x0D; results of a selective investigation of the industrial site and the determination of the heavy metals content in the soil as&#x0D; initial data were used. On the example of zinc and cadmium, it has been demonstrated that their measured concentrations do not pose a significant risk to the health of adults and children by inhalation, oral and contact intake routes. It has been established that it is possible to change the functional use of the territory, including the residential use, without soil cleanup activities. The levels of cadmium content in soils, which pose risk of non-carcinogenic effects for humans living in the territory are demonstrated.

Inversion study of cadmium content in soil based on reflection spectroscopy and MSC-ELM model

Heavy metal pollution in saline-alkali land has a significant impact on the ecological environment and human health. Rapid and accurate inversion of cadmium (Cd) element content in the saline-alkali land is important for environmental protection, saline-alkali soil improvement and conversion of saline-alkali land to cultivated land. Using traditional chemical detection methods to detect the content of heavy metal elements requires a long testing time and has the drawback of high prices. In this paper, we select the saline-alkali land of Zhenlai County as the study area and combine visible-NIR spectroscopy with machine learning models to invert the Cd content in the saline-alkali land. We preprocess the original reflection spectra using fractional order derivatives (FOD), then construct six three-band spectral indices (TBIs) and obtain the corresponding optimal band combination parameters by the optimal band combination (OBC) algorithm. To address the shortcomings of two-hidden-layer extreme learning machine (TELM), this paper introduces new weight parameters among the nodes of the first hidden layer, further extends it to multiple layers on this basis, and proposes the MSC-ELM model. The improved model is compared with several models, such as random forest (RF), partial least squares (PLS) and extreme learning machine (ELM). And the model performance is analyzed and compared by introducing several performance indicators, such as root mean square error (RMSE) and the ratio of the performance to interquartile (RPIQ). The experimental results show that the FOD transformation can eliminate the baseline drift and reduce the spectral noise. The constructed TBIs can effectively enhance the correlation with Cd content relative to the original single band, reduce redundant information and enhance the spectral features. The MSC-ELM model achieves better performance metrics compared to the other models and obtains the optimal prediction performance. This study provides an accurate and rapid method for the detection of Cd content in saline soil, which is important for the improvement and ecological recovery of saline soil.

Changes of Microbial Diversity in Rhizosphere of Different Cadmium-Gradients Soil under Irrigation with Reclaimed Water

Water scarcity and the uneven distribution of water resources in China have resulted in water shortages for agricultural irrigation in arid and semi-arid areas. Reclaimed water used for agricultural irrigation has become an effective solution in the context of the global water shortage. In order to improve soil productivity and solve the shortage of water resources, we carried out reclaimed water irrigation experiments on polluted soil. Compared with full irrigation treatments, the EC value of reclaimed water under deficit irrigation treatments decreased by 2.89–42.90%, and the content of organic matter increased by 6.31–12.10%. The proportion of Acidobacteria community in soils with different cadmium concentration gradients irrigated with reclaimed water ranged from 13.6% to 30.5%, its relative abundance decreased with the increase of soil cadmium concentration. In particular, the relative abundance of Pseudomonas pathogens in deficit irrigation treatments was lower than that of the full irrigation treatments. RDA analysis showed that the environmental factors that played a leading role in the change of microbial community structure were organic matter and pH. Furthermore, the metabolic function potential of the rhizosphere soil bacterial community in deficit irrigation treatments was higher than that of full irrigation treatments with reclaimed water. This study proved that reclaimed water irrigation for cadmium contaminated soil did not aggravate the pollution level and promoted the soil ecological environment with better microbial community diversity.

Study of the Effect of Mercury Salt on the Presence of Annelida (Lumbricus terrestris) in Soil and the Histological Changes on the Skin Tissue

The earthworm is the most beneficial organism for assessing metallic contamination due to the fact that critical high-quality correlations have been determined between earthworm steel concentrations and soil cadmium, copper, lead, zinc, and mercury concentrations. The mercury compounds are very poisonous for most organisms. Here, we investigated the ability of earthworms (Lumbricus terrestris) to HgCl2 (below laboratory conditions). A study of the effect of five different salt concentrations of mercury chloride (HgCl2) 1 ppm, 5 ppm, 10 ppm, 50 ppm, and 100 ppm was studied on worm survival and calculation of the concentration required to destroy half the number of worms (LC50). The results showed that there is an inverse relationship between these salt concentrations and the time required to perish 100% of worms. It was found that the concentration of 100 ppm is the lethal concentration of half the number (LC50) of the earthworm (Lumbricus terrestris). The effects of the salt concentrations used confirmed their effect on the experimental worm weights as well, so the concentration of 50 ppm was the most influential on earthworm weights of the type of Lumbricus terrestris, as it caused a reduction 12% of worm weights with a significant difference, while the concentrations 1 ppm and 100 ppm were the least effective, as they caused the worms to decrease by only (5%), while the remaining two concentrations 5 ppm and 10 ppm caused their effect to decrease by 7% only. Thus, it can be concluded that lower worm weights have nothing to do with the lethal concentrations of the heavy metal salt (HgCl2). The histological study also showed that low concentrations of mercury chloride salt have less effect on earthworms’ skin tissue compared to higher concentrations.

Distribution Mapping of Cadmium on Water and Soil in Rice Fields Around The Industrial Area of Sidoarjo Regency

The development of industrial estates in the western part of Sidoarjo Regency include Taman District, Krian District, Balongbendo District, and Tarik District have a major influence on population growth. The existence of the rice fields around the industry indirectly affects the quality of the environment due to industrial activities. The purpose of this research is to identify the spatial distribution of Cadmium heavy metal content in the water in rice fields around the industrial area of Sidoarjo Regency and to identify the spatial distribution it. The parameters taken are cadmium content in soil and water samples in the rice fields. The method used in the study was a survey and laboratory, mapping used the kriging method. The result of the research showed The highest cadmium content is in the rice fields of the Taman sub-district. cadmium content in water is 1.90 ppm while in the soil is 2.43 ppm. The quality level at the four locations was declared to exceed the environmental quality standard. The distribution map showed the area of the Taman sub-district is the highest compared to other sub-districts.

Quantitative analysis of soil cadmium content based on the fusion of XRF and Vis-NIR data

Anthropogenic activities, such as sewage irrigation and the application of pesticides and fertilizers, are the main causes of Cadmium (Cd) pollution, which reduces soil quality and threatens the environment and human health. Although the traditional cadmium measurement methods are accurate, it involves complicated sample processing steps and complicated laboratory analysis, which is time-consuming and costly, and is often unfriendly to the environment. X-ray fluorescence (XRF) and visible near-infrared (vis–NIR) spectroscopy have been recognized as alternatives to measure soil heavy metal contamination in a cheap, fast, non-destructive, and environmentally conscious manner. In this study, 370 paddy soil samples from the Nanji area of Poyang Lake were taken as the research object, and the feasibility and effectiveness of XRF and vis-NIR spectroscopy for estimating soil chromium content were discussed, respectively, and the combination of the two was used to estimate soil Cd content. Combined with some spectral preprocessing methods, the quantitative analysis model of least squares support vector machine (LS-SVM) and leave-one-out cross validation with three different data fusions (Equal Weight Fusion, Coaddition Fusion and Outer Product Fusion) was established. The results showed the accuracy and stability of Equal Weight Fusion and Outer Product Fusion was better than the single spectrum quantitative analysis model. The model of Outer Product Fusion at LOOCV set had the best performance with the determination coefficient (R2) of 0.91, root mean square error of cross validation (RMSECV) of 0.12 ​mg/kg and the relative percent deviation (RPD) of 3.27, with R2 ​= ​0.90, RMSEP ​= ​0.13 ​mg/kg and RPD ​= ​3.11 in Prediction set, which can satisfy the detection requirements. This method was accurate, reliable, and can provide a reference for the research of soil heavy metal distribution investigation methods.

Effects of phosphorus-containing material application on soil cadmium bioavailability: a meta-analysis.

Diverse phosphorus-containing materials (PCMs) were widely applied in remediation of cadmium-contaminated soils, and their effects on the change of soil cadmium availability (SCA) varied with their physicochemical characteristics and environmental conditions. Investigation on the effect of various PCMs on reducing SCA under different conditions favors the safe utilization of Cd-contaminated soil. Herein, a meta-analysis of literature published before August 2021 was carried out. A total of 342 independent observations were obtained from 42 published papers which included 9 factors that may affect the passivation effect of fertilizer content: phosphorus type, phosphorus application rate, soil pH, soil CEC, soil organic matter, experiment type, and time. Results of boosted regression tree analysis showed that the application rate is the most important factor contributing to the SCA, followed by soil pH and duration. Results of this meta-analysis showed that medium P input shows potential for reactivating the SCA. Under alkaline soil conditions and high soil CEC values, PCM input can better deactivate SCA. In addition, the difference from the previous understanding is that under the medium input of phosphorus-containing fertilizer (90-500mg P∙kg-1), it will significantly increase the content of available cadmium in soil. In addition, future recommendation for exploring novel PCMs and suitable strategies for controlling the SCA though PCM application were also proposed. Our works may promote the interpretation of the interference factors on the SCA changes and fill the research gaps on utilization of PCM in Cd-polluted soil remediation.

Cadmium Accumulation Characteristics of Different Heat Varieties Under Cadmium Stress

In order to provide technical support for the safe utilization of heavy metal-polluted farmland, we screened wheat varieties with a low accumulation of Cd in grain via a pot experiment. For this purpose, we respectively investigated the enrichment and transport characteristics of Cd in various plant parts of 119 wheat varieties under the conditions of 1.5 mg·kg-1 (low content) and 4.0 mg·kg-1 (high content) Cd-contaminated soil and explored the correlation between the Cd content of different organs of wheat and the relationship between Cd content in soil and the uptake of Cd by wheat. The results showed that:① there were significant differences in the ability to accumulate and transport Cd in roots, stems, leaves, and grains of tested wheat varieties (P<0.05). Under the condition of low Cd content, the Cd enrichment ability of each part of the wheat plant was as follows:leaf>stem ≈root>grain; under high-content stress conditions, the Cd enrichment ability of each part of the wheat plant was:leaf>root>stem>grain; under different content conditions, the Cd transport ability of each part of the wheat plant was:leaf>stem>grain. Cd content in the wheat shoot was positively correlated with total Cd content and ion-exchangeable Cd content in soil (P<0.01) and was closely related to strong transpiration under the pot experiment. ② The correlation coefficient r of BCFCd of wheat roots, stems, leaves, and grain was -0.267 to -0.645, showing a very significant negative correlation (P<0.01), indicating that with the increase in soil Cd content, the migration and accumulation degree of Cd in wheat plant organs showed a downward trend. Moreover, the negative correlation between BCFCd and soil Cd content in stems was significantly higher than that in roots, leaves, and grains, indicating that the enrichment of Cd in wheat plants largely depended on the accumulation and transportation of stems. ③ The correlation coefficient r of Cd content between the root and stem, root and leaf, root and grain, stem and leaf, stem and grain, and leaf and grain in low-and high-content groups was 0.450-0.763, showing a very significant positive correlation (P<0.01), indicating that there was a close transport relationship among the wheat organs, and the degree of translocation from the root to stem and stem to leaf was higher than that from the stem to grain and leaf to grain. ④ Using cluster analysis and enrichment and translocation coefficient sequencing, this study screened 16 and 11 wheat varieties with low Cd accumulation under the soil cadmium content of 1.5 mg·kg-1and 4.0 mg·kg-1, respectively. Among them, Luohan 7 could be used as the optimal wheat variety with low Cd accumulation under the conditions of low-, medium-, and high-Cd content.

Forage crops and cadmium: How changing farming systems might impact cadmium accumulation in animals

Production advantages, environmental benefits and increasing parasite resistance are changing the composition of New Zealand pastures. Traditional ryegrass/clover pasture mixes are being replaced by forage herb crops such as lucerne, chicory and plantain that accumulate a higher concentration of contaminants such as cadmium (Cd). To explore the relationship between Cd in forage crops and the Cd concentration accumulated by animals, four-month-old lambs at four farms across the central North Island of New Zealand were grazed on different forage crops (ryegrass, chicory, lucerne and plantain) between weaning and slaughter. Soil and pasture samples, and sequential liver biopsies, were collected and analysed for total Cd. There were significant differences in Cd concentration between the forage crops (chicory > plantain > lucerne > ryegrass) and this ordering was repeated for Cd in liver. There was no exceedance of maximum limits (ML) for Cd in offal set by the EU and NZ/Australia food safety standards authorities for animals of this study, although the highest concentration of Cd in chicory (0.85 mg/kg DW) was considerably lower than has been recorded elsewhere in New Zealand (4.5 mg/kg DW). Provisional Soil Management Values (SMVs) were developed to explore compliance of liver with EU food standards as a function of grazing chicory. For a soil pH of 5, exceedance might occur at a soil cadmium concentration of 0.34 mg/kg. This concentration falls within Tier 0 of the New Zealand Tiered Fertiliser Management System which seeks to ensure soil Cd remains within acceptable limits over the next 100 years and beyond. Increased Cd uptake by fodder crops and its management in these Tier 0 pastoral soils is therefore an emerging issue for pastoral agriculture. The risk of ML exceedance for animals grazing forage crops such as chicory on low Cd soils should be further considered to ensure uninterrupted access to export markets.