Soil Zn Concentrations Research Articles

Biochemical Responses of Medicinal Plant Tussilago farfara L. to Elevated Heavy Metal Concentrations in Soils of Urban Areas.

This study was conducted in Tyumen (Russian Federation) to establish the effects of heavy metals’ (Cu, Zn, Fe, Mn, Pb, and Cd) accumulation in soil and coltsfoot, as well as plants’ biochemical responses to such an accumulation. The mobile and acid-soluble heavy metal fractions in soils, and the heavy metal contents in plants, were determined by atomic absorption spectrophotometry. The Cu, Zn, Fe, Mn, and Pb concentrations in soils exceeded background values. Pb content at the battery manufacturing plant was above the maximum permitted concentration. The percentages of the mobile heavy metal fractions decreased in the following order: Mn > Zn > Cu > Fe. The greatest heavy metal accumulation in soils and plants was found at the battery manufacturing and metallurgical plants examined in our study. Heavy metals’ accumulation in the aboveground part of Tussilago farfara decreased in the following order: Fe > Zn > Cu > Mn > Pb > Cd. The accumulation of heavy metals stimulated the synthesis of photosynthetic pigments by 6–30%. Heavy metals provoked oxidative stress in cells, increasing the concentration of lipid peroxidation in products by up to 80%. Plant phenolics and flavonoids in the urban area of our study decreased compared to those in the control by 1.05, reaching up to 6.5 times. The change in coltsfoot catalase activity both increased and declined. Biochemical responses and heavy metal accumulation in coltsfoot from urban areas limit its use for medicinal purposes.

Zinc Concentration and Distribution in Vineyard Soils and Grapevine Leaves from Valdepeñas Designation of Origin (Central Spain)

(1) Background: The purpose of this study was to investigate zinc contents in leaves and soils of the Valdepeñas Protected Designation of Origin (PDO), situated in central Spain. Zn distribution maps of leaves and soils were obtained. (2) Methods: Ninety soil profiles were described, sampled and analyzed. Furthermore, vineyard leaves were collected randomly in each of the analyzed soil vineyard profiles. Soil and leaf samples were analyzed by X-ray fluorescence. (3) Results: The mean total Zn concentrations in vineyard soils were in the range of 16.2–153.7 mg·kg−1, with a mean of 47.5 mg·kg−1. The obtained values above the 95th percentile (between 81.3 and 153.7 mg·kg−1) could be affected by different parent materials or Zn agricultural treatments in vineyards. Contents in different soils follow the order Entisol > Alfisol > Inceptisol. The average Zn content value in leaves was 23.8 mg·kg−1 and oscillated between 11.5 and 93.3 mg·kg−1; minor differences were detected between soil types, with the highest value in plants grown on soils without carbonates. (4) Conclusions: The obtained values are optimal for vine cultivation. The bioaccumulation factors in leaves were lower than unity (0.24–0.53 range). This means that the Zn bioaccumulation process is relatively low in the soil–grapevine system. This study serves as a reference to identify areas that present Zn deficiencies or risk of contamination.

Long-Term Zinc Fertilization in Calcareous Soils Improves Wheat (Triticum aestivum L.) Productivity and Soil Zinc Status in the Rice–Wheat Cropping System

Rice–wheat cropping system (RWCS) is considered as the furthermost vital system in the Indo-Gangetic Plains of South-Asia, including India, Pakistan, Bangladesh, and Nepal. Recently, the deficiency of micronutrients like zinc (Zn) has emerged as one of the prime limitations for the sustainability issues of this RWCS in Zn deficient calcareous soils, particularly in India, as a result of the calcareous typic ustifluvents taxonomic nature of the soils. Therefore, a new Zn fertilization approach for soils is very much needed in the intensive RWCS. Thus, a six-year-long investigation was designed with three different modes of Zn application, viz., the application of Zn only in the first year of study, application in alternative years, and application in every year. Four different rates of Zn applications in a hectare of area for a single year, viz., 2.5, 5.0, 7.5, and 10 kg ha−1 year−1, and times of Zn application, viz., only at first year, alternative years, and in each year. The major aims of the study were to determine Zn concentration in soil; yield; and Zn accumulation by wheat crop under different application methods of Zn. From this study, it was found that a large portion of the applied Zn was present in the residual fraction, and it was also revealed that increasing the frequency of Zn application resulted in the increment in the crystalline fraction. Significant correlation of water-soluble and exchangeable Zn (WS+EX-Zn), complexed Zn (COM-Zn), amorphous Zn (AMO-Zn), organic Zn (ORG-Zn), total Zn (TOT-Zn), grain yield, and grain Zn uptake by wheat indicated that these Zn fractions were dominant forms in the soil to be utilized by plants under rice–wheat rotation. Concerning yield and Zn uptake by wheat, it was noted that the Zn application at 10 kg ha−1 in alternate years was the best Zn application method, while application of Zn at 7.5 kg ha−1 in each year also resulted in comparable yield.

Human risk associated with the ingestion of artichokes grown in soils irrigated with water contaminated by potentially toxic elements, Junin, Peru.

The contamination of water, air and soil with potentially toxic elements (PTE) compromises the supply of contaminant free food. Vegetables grown in contaminated soils can absorb and accumulate PTE at concentrations that are toxic to human health. In this context, the human risk associated with the intake of artichokes grown in soils irrigated with PTE contaminated water was assessed. 120 samples of surface soil and artichoke heads were collected and the concentrations of Cu, Fe, Pb, Zn and As were determined. The results showed that the concentrations of Cu, Fe and Zn in soil did not exceed the standards of the Ministry of Environment of Peru, but they did exceed those of Pb (125.45 mg kg−1) and As (28.70 mg kg−1). The decreasing order of mean PTE concentration in artichoke heads was Fe > Zn > Cu > Pb > As, exceeding the permissible levels of FAO/WHO CODEX Alimentarius. However, the concentrations of As comply with the maximum limits of inorganic contaminants in vegetables (0.3 mg kg−1) established in the MERCOSUR regulations. The non-carcinogenic and carcinogenic risk of Pb and As indicated that the ingestion of artichoke heads does not represent a health risk.

Local and downstream cumulative effects of traditional meadow management on stream-water quality and multiple riparian taxa

Water quality and riparian communities are among the most affected stream components by agriculture. However, little is known about the effects of riparian management for both aquatic and terrestrial taxa at different spatial scales. Here, we surveyed aquatic (diatoms) and terrestrial taxa (bryophytes, vascular plants, litter-dwelling snails, and ground and volant arthropods), to compare the abundance and richness of riparian taxa and chemical quality between reference and exposed sites in two stream reaches each of c. 3.5 km in northwestern Spain. Impacts in exposed sites were mainly due to traditional farming practices (TFPs), which included traditional meadow management, weirs built for now-unused water mills and sporadic timber harvesting. Therefore, we measured ten covariates and predictors related to the intensification of TFPs at local and within-stream scales and explored associations with riparian and water-quality measures to study the potential effects of TFPs in more detail. Reference and exposed sites did not differ significantly in water properties (diatom-biotic indices, conductivity, total organic carbon and nitrates), but exposed sites had less concentrations of soil metals Cd, Cu, Ni and Zn and less cover and richness of riparian trees, as inferred by the index QBR. Exposed sites had more volant insect decomposers and reference sites a greater abundance or richness of snails, ground predators and decomposers. Bryophyte richness was greater in reference sites. Our inferences may inform the joint cumulative downstream effects of weirs, meadow uses and riparian alterations but were generally consistent with most riparian taxa benefiting from having larger forested areas. Given the contrasting responses among taxa, we argue that land snails, terrestrial flies, and centipedes may be valuable additions to current riparian assessments mostly based on plants, beetles and spiders as indicator taxa. Our study also suggests caution when inferring farming impacts on streams from the surface area of pastoral land.

Source and Health Risk Assessment of Heavy Metals in Soil-Ginger System in the Jing River Basin of Shandong Province, North China.

This study investigated the characteristics and sources of heavy metals in a soil–ginger system and assessed their health risks. To this end, 321 topsoil samples and eight soil samples from a soil profile, and 18 ginger samples with root–soil were collected from a ginger-planting area in the Jing River Basin. The average concentration of heavy metals in the topsoil followed the order: Cr > Zn > Pb > Ni > Cu > As > Cd > Hg. In the soil profile, at depths greater than 80 cm, the contents of Cr, Ni, and Zn tended to increase with depth, which may be related to the parent materials, whereas As and Cu contents showed little change. In contrast, Pb content decreased sharply from top to bottom, which may be attributable to external environmental and anthropogenic factors. Multivariate statistical analysis showed that Cr, Ni, Cu, Zn, and Cd contents in soil are affected by natural sources, Pb and As contents are significantly affected by human activities, and Hg content is affected by farmland irrigation. Combined results of the single pollution index (Pi), geo-accumulation index (Igeo), and potential ecological risk assessment (Ei and RI) suggest that soil in the study area is generally not polluted by heavy metals. In ginger, Zn content was the highest (2.36 mg/kg) and Hg content was the lowest (0.0015 mg/kg). Based on the bioconcentration factor, Cd and Zn have high potential for enrichment in ginger. With reference to the limit of heavy metals in tubers, Cr content in ginger exceeds the standard in the study area. Although Cr does not accumulate in ginger, Cr enrichment in soil significantly increases the risk of excessive Cr content in ginger.

Heavy metal accumulation and genotoxic effect of long-term wastewater irrigated peri-urban agricultural soils in semiarid climate

Water scarcity is becoming an alarming issue in the Mediterranean countries. Therefore, using the treated wastewater in the irrigation is considered as a valuable option. However, uncontrolled and long-term irrigation by wastewater leads to human health and environmental damages, mainly related to some specific pollutants. The assessment of the availability and toxicity of the heavy metals after long term irrigation, under semi-arid climate, is not yet well documented. In this study, physicochemical properties, genotoxicity (Vicia faba micronucleus test), total and available (CaCl2-extractable) concentrations of Cr, Pb, Cu, Zn, Co and Cd in eight soils of peri-urban farms irrigated with wastewater were examined to evaluate their accumulation.The results indicated that long-term irrigation with wastewater induced significant increase of electrical conductivity, organic matter, calcium carbonate equivalent and nutrient availability. Total and available concentration of heavy metals were significantly higher (P < 0.05) in irrigated soils by wastewater. The total concentrations of Zn, Pb, Cu, Cr, Cd and Co in irrigated soils by wastewater at 0–40 cm depth were 85.69, 43.94, 34.86, 14.62, 9.94 and 7.17 mg kg−1, respectively. Furthermore, the increase of the available metal fraction in irrigated soils by wastewater at 0–40 cm depth followed the following order: Co (1270.1%) > Cd (914.5%) > Cu (881.5%) > Cr (471.2%) > Pb (230.8%) > Zn (223.8%). The micronucleus assay indicated significant increase of micronucleus frequencies (41.25‰, 35.48‰, 21.66‰, 16.23‰ and 13.62‰ respectively for P1, P2, P3, P4 and P7) which were higher than the negative control (0‰) and the irrigated soil by fresh water (3.29‰). The micronucleus induction was significantly correlated with the high available fraction of Cd, Co and Zn at P1, P2 and P7. The genotoxicity can be a powerful test to assess the ecological effects associated with the interactions of heavy metals with other pollutants.

Spatial Distribution and Evaluation of Arsenic and Zinc Content in the Soil of a Karst Landscape

Karst features such as polje are highly vulnerable to natural and anthropogenic pollution. The main objectives of this study were to investigate the soil quality in the Ioannina polje (north-west Greece) concerning arsenic (As) and zinc (Zn), and delineate their origin as well as compare the As and Zn content in soil with criteria recorded in the literature. For this purpose, the geomorphological settings, the land use, and the soil physicochemical properties were mapped and evaluated, including soil texture and concentrations of aqua-regia extractable As and Zn. The concentration of elements was spatially correlated with the land use and the geology of the study area, while screening values were applied to assess land suitability. The results reveal that 72% of the total study area has a very gentle slope. This relief favors urban and agricultural activity. Thus, the urban and agricultural land used cover 92% of the total area. The spatial distribution for As and Zn in the soil of the study area is located on very gentle slopes and is strongly correlated with the geological parent materials and human-induced contamination sources. Arsenic and Zn can be considered enriched in the soil of the area studied. The median topsoil contents (in mg kg−1) for As (agricultural soil 16.0; urban soil 17.8) and Zn (agricultural soil 92.0; urban soil 95.0) are higher compared to the corresponding median values of European topsoils. Land evaluation suitability concerning criteria given from the literature is discussed. The proposed work may be helpful in the project of land use planning and the protection of the natural environment.

Environmental determinants of plant species diversity in organic and conventional vineyards

The factors affecting the plant biodiversity in organic (manure application) and conventional vineyards (variety “Agiorgitiko for both) in southern Greece were examined separately for each vineyard type. The index for plant biodiversity was chosen to be the Shannon one (SH). The Pearson correlation coefficients disclosed that the common factors in both vineyards types affecting the SH were the concentrations of the soil organic C and organic N, the nitrates –N, the available (Olsen) P, available Cu, exchangeable K and the CaCO3 percentage. The C/N ratio in soils affected positively and significantly the SH index in both vineyards types. That means that the supply of N is not a problem with regard to decomposition but the organic C as a source of energy can be a limiting factor to plant diversity. The earthworm population density in the two vineyards types was also a significant positive factor to the SH. The concentrations of the available Mg, Zn and ammonium-N in soils affected the SH index significantly only in the conventional vineyards although their concentrations in soils did not differ. We can conclude that chemical fertilization can also affect plant variability.

Predicting Bioaccumulation of Potentially Toxic Element in Soil–Rice Systems Using Multi-Source Data and Machine Learning Methods: A Case Study of an Industrial City in Southeast China

Potentially toxic element (PTE) pollution in farmland soils and crops is a serious cause of concern in China. To analyze the bioaccumulation characteristics of chromium (Cr), zinc (Zn), copper (Cu), and nickel (Ni) in soil-rice systems, 911 pairs of top soil (0–0.2 m) and rice samples were collected from an industrial city in Southeast China. Multiple linear regression (MLR), support vector machines (SVM), random forest (RF), and Cubist were employed to construct models to predict the bioaccumulation coefficient (BAC) of PTEs in soil–rice systems and determine the potential dominators for PTE transfer from soil to rice grains. Cr, Cu, Zn, and Ni contents in soil of the survey region were higher than corresponding background contents in China. The mean Ni content of rice grains exceeded the national permissible limit, whereas the concentrations of Cr, Cu, and Zn were lower than their thresholds. The BAC of PTEs kept the sequence of Zn (0.219) &gt; Cu (0.093) &gt; Ni (0.032) &gt; Cr (0.018). Of the four algorithms employed to estimate the bioaccumulation of Cr, Cu, Zn, and Ni in soil–rice systems, RF exhibited the best performance, with coefficient of determination (R2) ranging from 0.58 to 0.79 and root mean square error (RMSE) ranging from 0.03 to 0.04 mg kg−1. Total PTE concentration in soil, cation exchange capacity (CEC), and annual average precipitation were identified as top 3 dominators influencing PTE transfer from soil to rice grains. This study confirmed the feasibility and advantages of machine learning methods especially RF for estimating PTE accumulation in soil–rice systems, when compared with traditional statistical methods, such as MLR. Our study provides new tools for analyzing the transfer of PTEs from soil to rice, and can help decision-makers in developing more efficient policies for regulating PTE pollution in soil and crops, and reducing the corresponding health risks.

Adaptive potential of Typha laxmannii Lepech to a heavy metal contaminated site

To study the adaptive potential of the plant Typha laxmannii Lepech. to heavy metal (HM) stress on the basis of analysis of its morphological and anatomical features under the conditions of an anthropogenically transformed ecosystem of the Don River Delta. The soils on the monitored plots are of the Fluvisol type. The soil characteristics and total concentrations of Mn, Ni, Cd, Cu, Zn, Pb and Cr in soils and cattail plants were analysed. Anatomical-morphological and electron-microscopic examinations revealed the toxic effect of HMs on the roots and leaves of T. laxmannii plants. The studied soils were found to contain high levels of the Zn, Cr, Pb and Cu. It was shown that the sources of Zn, Pb and Cu in the soils were anthropogenic in nature. The high Cr level in soils was due to the natural lithogenic factor. The contents of HM mobile forms in the soils exceeded the maximum permissible concentrations of Cd, Zn, Pb and Ni. An examination of communities of T. laxmannii grown in the impact zone revealed, proliferation anomalies. Ultrastructural studies of plants showed changes in cell membranes, as well as in the main cytoplasmic organelles. The revealed structural changes are assumed to contribute to a slowdown in the ontogenetic development of plants and a decrease in their morphometric parameters under anthropogenic pollution. No significant ultrastructure changes were observed in the roots compared with the leaves, which indicates their high adaptive potential.

The effect of phosphorus split application on use efficiency and dynamic of phosphorus and zinc at the soil, aerial parts, and grain, and Zinc biofortification of two rice varieties (Oryza sativa L.) (Hashemi and Guilaneh)

Introduction: Despite the P vitality for rice cultivation, its recovery index in paddy soils is very low and less than 25% of added P, and the rest goes out of reach of rice plant through the P fixation by soil particles at different fractions. Also, despite abundant studies on the effect of basal soil P application, we face a lack of knowledge on research findings of the P splitting application and its effect on soil Zn concentration and tissues Zn content. Thus, the current research project was done to explore the effect of P splitting application at flooded conditions on the soil and rice plant tissues P and Zn variation trend at the different rice growth stages of two more common varieties (Hashemi and Guilaneh varieties). Materials and methods: The outdoor pot experiment was conducted on a three factors factorial experiment in a randomized complete block design with three replications in 2017 at the research farm of the rice research institute of Iran, Rasht. The experimental treatments were: phosphorus fertilizer split application at five levels, soil at two levels, and rice varieties at two levels (Hashemi (local variety) and Guilaneh(improved variety)), The P application treatments were: control (no added P), 100% basal, P split application at 50% basal and 50% at 20 days after transplanting (DAT), P split application at 50% basal and 50% at 60 days after transplanting (DAT), P split application at 50% basal, 25% at 20 days after transplanting, and 25% at 60 days after transplanting. Results: The results indicated that the highest soil available P and Zn concentrations were recorded at the flowering stage about 95.3 and 90.10, and 8.6 and 8.7 mgkg-1by two and three P split for Hashemi and Guilaneh, respectively. Also, the maximum P of rice grain was obtained about 0.17 and 0.20 mgkg-1 for Hashemi and Guilaneh, respectively. The Zn content of rice grain at P split pots was significantly more than control and 100% basal application. The highest agricultural recovery (13.31 and 12.72), physiological (693.19 and 740.10) and physiological-agricultural efficiency (482.00 and 753.00), P use efficiency (5.34 and 5.66), and apparent recovery (1998 and 1272.22 kg kg-1) were found for Hashemi and Guilaneh, respectively, in the two and three P split application. Furthermore, stepwise multiple regression analysis revealed that the soil available P concentration at ripening stage, Zn content of the grain, and Zn concentration at rice aerial parts can explain 52% of grain yield variations for studied rice cultivars. Conclusion: The three-stage P splitting (50% soil basal, 25% 20 DAT, and 25% 60 DAT) increased the Zn content of the Hashemi variety by about 54.72% at slit loam soil, whereas the Guilaneh rice variety was received a 37.5% increase in Zn content of grain in silty clay through two-stage P splitting (50% soil basal and 50% 20 DAT) compare to control (100 % basal). It can be concluded both three and two-stage P splitting might be positively significantly effective on rice grain nutritional quality.

Nano Zero Valent Iron (nZVI) as an Amendment for Phytostabilization of Highly Multi-PTE Contaminated Soil.

In recent years, a lot of attention has been given to searching for new additives which will effectively facilitate the process of immobilizing contaminants in the soil. This work considers the role of the enhanced nano zero valent iron (nZVI) strategy in the phytostabilization of soil contaminated with potentially toxic elements (PTEs). The experiment was carried out on soil that was highly contaminated with PTEs derived from areas in which metal waste had been stored for many years. The plants used comprised a mixture of grasses—Lolium perenne L. and Festuca rubra L. To determine the effect of the nZVI on the content of PTEs in soil and plants, the samples were analyzed using flame atomic absorption spectrometry (FAAS). The addition of nZVI significantly increased average plant biomass (38%), the contents of Cu (above 2-fold), Ni (44%), Cd (29%), Pb (68%), Zn (44%), and Cr (above 2-fold) in the roots as well as the soil pH. The addition of nZVI, on the other hand, was most effective in reducing the Zn content of soil when compared to the control series. Based on the investigations conducted, the application of nZVI to soil highly contaminated with PTEs is potentially beneficial for the restoration of polluted lands.

Heavy metals and related properties in farming soils adjacent to a future copper mine, interpretation using GIS, and statistical methods

Exploitation of mines can lead to the entrance of heavy metals into the environment. There is a possibility of water, soil, and plant pollution in Darreh Zereshk area in the near future. To assess the soil contamination and determine the origin of selected heavy metals, enrichment factor (EF) and geoaccumulation index (Igeo) accompanied with principle factor analysis (PCA) and map of spatial distribution of the elements were conducted. A total of 30 agricultural soil samples and 12 background soil samples were collected from Darreh Zereshk area in central Iran which is going to be one of the richest copper mines in Iran and the Middle East. Total and soluble concentration of heavy metals (Cu, Pb, Zn, Mn, As, Fe, Ni, and Cr) and some physico-chemical properties of soils were determined. The results showed that contamination of the agricultural soils is more severe for Pb, Cu, and Zn and less severe for As. The origin of Ni and Cr did not seem to be anthropogenic. The average concentration of Cu, Pb, Zn, Mn, As, Fe, Ni, and Cr in agricultural soils of the area were 36.87 mg/kg, 190.78 mg/kg, 170.33 mg/kg, 367.41 mg/kg, 69.42 mg/kg, 15494.1 mg/kg, 29.25 mg/kg, and 25.01 mg/kg, respectively. Since the Fe and Mn with geogenic origin were located in the same component with Cu, Zn, Pb, and As; it can be inferred that the source of these elements is controlled by both parent material of soil and anthropic activity.

Liming impacts barley yield over a wide concentration range of soil exchangeable cations

Liming has widespread and significant impacts on soil processes and crop responses. The aim of this study was to describe the relationships between exchangeable cation concentrations in soil and the relative yield of spring barley. The hypothesis was that yield is restricted by the concentration of a single exchangeable cation in the soil. For simplicity, we focused on spring barley which was grown in nine years of a long-term experiment at two sites (Rothamsted and Woburn). Four liming rates were applied and in each year the relative yield (RY) and the concentrations of exchangeable cations were assessed. Liming had highly significant effects on the concentrations of most exchangeable cations, except for Cu and K. There were significant negative relationships (either linear or exponential) between the exchangeable concentrations of Mn, Cd, Cr, Al, Fe, Cu, Co, Zn and Ni in soil and soil pH. The relationships between RY and the concentrations of selected exchangeable cations (Mn, Ca and Al) were described well using log-logistic relationships. For these cations a significant site effect was probably due to fundamental differences in soil properties. At both sites the concentrations of exchangeable soil Al were excessive (> 7.5 mg kg−1) and were most likely responsible for reduced barley yields (where RY ≤ 0.5) with soil acidification. At Rothamsted barley yield was non-limited (where RY ≥ 1) at soil exchangeable Mn concentrations (up to 417 mg kg−1) greater than previously considered toxic, which requires further evaluation of critical Mn concentrations.

Long-term effects of phytoextraction by a poplar clone on the concentration, fractionation, and transportation of heavy metals in mine tailings.

Mine tailings are one of main causes of diffused heavy metal pollution since the heavy metals in there may acquire mobility. The current knowledge of the processes at work in long-term phytoremediation by woody species remains insufficient. Through a 4-year field study, we evaluated the phytoextraction efficiency of Populus deltoides CL. 'Xianglin 90' grown on a mine tailing co-polluted by Cd, Cu, Cr, Ni, Pb, and Zn. The concentrations of Cd, Cu, Ni, Pb, and Zn in the rhizospheric soil were reduced by amounts ranging from 12.86 to 42.19% during the study period. Bioconcentration factors and translocation factors showed that the accumulation of Cd and Zn occurring in the shoots was the most effective. Combined with the considerable biomass produced by poplar, the extracted amounts of Cd and Zn could reach 0.61 g and 10.66 g plant-1, respectively, in which the shoots account for 77.3% (Cd) and 89.0% (Zn) of the overall extraction amounts. Acid-soluble Cd and Zn increased by 5.49% and 4.29%, respectively, in the rhizosphere compared to the bulk soil, indicating that poplar enhanced the mobility of Cd and Zn in the rhizosphere, which explained its ability for bioaccumulation and root-shoot translocation. Moreover, calculated time required to address the issue of Cd and Zn pollution was theoretically shortened by more than half from 2015 to 2019. This study brings new insights into the long-term effects of phytoextraction on the concentration, fractionation, and transportation of heavy metals and confirms the potential of poplar as a Cd and Zn remediation species.

High Soil Phosphorus Application Significantly Increased Grain Yield, Phosphorus Content but Not Zinc Content of Cowpea Grains

To ameliorate the impact of soil phosphorus (P) deficiency on cowpea, the use of P-based fertilizers is recommended. Plant zinc (Zn) is an essential nutrient required by plants in a wide range of processes, such as growth hormone production and metabolism. However, a negative association between plant Zn content and high P application has been reported in some crops. There are few reports about soil P application and plant Zn content relationship on cowpea. Thus, this study investigated the response of cowpeas to three P rates in the screenhouse (0, 1.5, and 30 mg P/kg) and field (0, 10, and 60 kg P2O5/ha) and their effects on plant P and Zn content, biomass, and grain yield. In the screenhouse, shoot and root dry weights, and shoot P and Zn content were measured. Shoot dry weight, grain yield, grain P, and Zn contents were determined from field plants. Higher rates of P led to increased shoot biomass and grain yield of the field experiment but were not associated with a significant change in shoot or grain Zn content. There was not a significant correlation between grain yield and Zn content in high soil P (p &lt; 0.05). The effect of higher P application on reduced plant Zn contents may be genotype-dependent and could be circumvented if genotypes with high Zn content under high soil P are identified.

Potential Ecological Risk Assessment and Source Analysis of Heavy Metals in Soil-crop System in Xiong'an New District

In order to evaluate the potential ecological risk of heavy metals in the soil-crop system in the Xiong'an New District, the heavy metal contents and forms in wheat seed and root soil samples are analyzed, and the comprehensive pollution index (IPIN), potential ecological risk index (RI), bio-enrichment coefficient (BFC), risk assessment code (RAC), principal component analysis, and correlation analysis are used to assess the potential ecological risk of heavy metals and analyze their sources. The results indicate that the average content of Cd, Cu, Pb, and Zn in the root soil is significantly higher than the soil background value in Hebei province. The IPIN ranges from 0.2 to 5.18, 94.83% of the soil samples are in the safe and pollution-free grade, and the potential ecological risks of heavy metal are slight and moderate, accounting for 64.66% and 30.17%, respectively. Cd has the greatest potential ecological harm, followed by Hg, Cr, Ni, and Zn. All the heavy metal elements besides Cd in the root soil are dominated by the residual form, which accounts for 60%, and the bioactive form (ion-exchange and water-soluble state) of Cd accounts for 33.43%, indicating relatively high bio-availability. The risk assessment code can be ranked as Cd > Ni > Hg > As > Cu > Cr > Zn > Pb, and the risk of Cd is moderate, while other elements are of low or no risk. The leading potential source of heavy metals is human activity combined with the geological background. The migration and enrichment capability of the wheat seeds is in order from strong to weak of Zn > Cu > Cd > Hg > As > Ni > Pb > Cr, and the biological effective components of As, Cd, Pb, and Zn plays an substantial role in promoting the absorption of heavy metals. The content of heavy metals in the wheat seeds has a negative correlation with the soil pH, and the physical and chemical indices, such as OM and CEC, has bi-directional influence on the biological effective state of the heavy metals.

Potentially toxic metal(loid) distribution and migration in the bottom weathering profile of indigenous zinc smelting slag pile in clastic rock region.

BackgroundThere are contaminated by potentially toxic metal(loid)s (PTMs) that the surface soil and the weathering profiles around the indigenous zinc smelting slag piles or smelters in the smelting area. However, few systematic studies are currently focusing on the PTM distribution and migration among the slag and its bottom weathering profile.MethodsThis research determined the concentrations of PTMs and pH values. And we analyzed PTM distribution in the two weathering profiles (slag-covered and slag-absent) with a small horizontal distance in the clastic rock region in the smelting area.ResultsThe soil As and Pb contents, respectively, within the 30 and 50 cm depth in the slag-covered section were higher than those in the slag-absent profile. All soil Cd and Zn contents of the slag-covered core were significantly higher than those in the slag-absent weathering section.ConclusionsCompared with the slag-absent weathering section, some PTMs (i.e., As, Cd, Pb and Zn) in the bottom weathering profile were polluted by these elements in the covered slag in the clastic rock region, and their depths were influenced by the slag to varying degrees. Additionally, with time, some PTMs (especially Cd and Zn) of the slag might finally contaminate the groundwater by leaching and infiltration through its bottom weathering profile in the clastic rock region.

Comparing Biochar-Swine Manure Mixture to Conventional Manure Impact on Soil Nutrient Availability and Plant Uptake—A Greenhouse Study

The use of swine manure as a source of plant nutrients is one alternative to synthetic fertilizers. However, conventional manure application with &gt;90% water and a low C:N ratio results in soil C loss to the atmosphere. Our hypothesis was to use biochar as a manure nutrient stabilizer that would slowly release nutrients to plants upon biochar-swine manure mixture application to soil. The objectives were to evaluate the impact of biochar-treated swine manure on soil total C, N, and plant-available macro- and micronutrients in greenhouse-cultivated corn (Zea mays L.) and soybean (Glycine max (L.) Merr.). Neutral pH red oak (RO), highly alkaline autothermal corn stover (HAP), and mild acidic Fe-treated autothermal corn stover (HAPE) biomass were pyrolyzed to prepare biochars. Each biochar was surface-applied to swine manure at a 1:4 (biochar wt/manure wt) ratio to generate mixtures of manure and respective biochars (MRO, MHAP, and MHAPE). Conventional manure (M) control and manure-biochar mixtures were then applied to the soil at a recommended rate. Corn and soybean were grown under these controls and treatments (S, M, MRO, MHAP, and MHAPE) to evaluate the manure-biochar impact on soil quality, plant biomass yield, and nutrient uptake. Soil organic matter significantly (&lt;0.05) increased in all manure-biochar treatments; however, no change in soil pH or total N was observed under any treatment. No difference in soil ammonium between treatments was identified. There was a significant decrease in soil Mehlich3 (M3) P and KCl extractable soil NO3− for all manure-biochar treatments compared to the conventional M. However, the plant biomass nutrient concentrations were not significantly different from control manure. Moreover, an increasing trend of plant total N and decreasing trend of P in the plant under all biochar-manure treatments than the controls were noted. This observation suggests that the presence of biochar is capable of influencing the soil N and P in such a way as not to lose those nutrients at the early growth stages of the plant. In general, no statistical difference in corn or soybean biomass yield and plant nutrient uptake for N, P, and K was observed. Interestingly, manure-biochar application to soil significantly diluted the M3 extractable soil Cu and Zn concentrations. The results attribute that manure-biochar has the potential to be a better soil amendment than conventional manure application to the soil.