Soil Mn Concentrations Research Articles

Distribution of manganese in surface soils and ecological risk assessment: a case study in the Pb-Zn mining and smelting area in the Mitrovica Region, Kosovo

ABSTRACT This study was conducted on the distribution of manganese content in the soils of the city of Mitrovica and its surroundings in Kosovo. A total of 156 topsoil samples were taken in the entire study region (sampling grid of 1.4 × 1.4 km2). The average Mn content of the entire study area is 1600 mg/kg (range 170–17000 mg/kg), which is 4.2 times higher than the EU average and 3.3 times higher than the global average. The spatial distribution maps show that the higher Mn contents occur mainly in soils from Miocene latite as well as quartz-latite and from Triassic volcanic-sedimentary formations in the eastern and north-eastern part of the study area. The lower values were found in the Flysch and Cretaceous flysch outcrops. It was found that the increased Mn contents in soils from this area are mostly of lithogenic origin. The values of the enrichment factor (EF) show that the soils of the entire study area are very highly enriched with Mn (20 < EF < 40). The values of the geo-accumulation index (1< I-geo ≤ 2), show that the soils of the entire study area are moderately contaminated with Mn.

Metals Transfer in Mushroom Tricholoma matsutake from Regional High Geochemical Background Areas: Environmental Influences and Human Health Risk.

Wild-grown edible mushrooms are important in world diets and are also efficient metal accumulators. Yunnan, Southwest China, is the main producing region, with typically high levels of geochemical metals. The environmental factors, bioaccumulation, distribution and human health risks of metals were examined in paired soil and Tricholoma matsutake (n = 54). T. matsutake grows on acidified soils (pH = 3.95-6.56), and metals show a strong heterogeneity, with Fe, Mn, Zn and Cu in the ranges of 16-201, 0.046-8.58 g kg-1, and 22.6-215, 3.7-155 mg kg-1. High soil Fe content led to great accumulation in T. matsutake (0.24-18.8 g kg-1). However, though the soil Mn content was higher than that of Zn and Cu, their concentrations in T. matsutake were comparable (21.1-487 vs. 38.7-329 and 24.9-217 mg kg-1). This suggested that T. matsutake prefers to accumulate Zn and Cu compared to Mn, and this is supported by the bioaccumulation factors (BAFs = 0.32-17.1 vs. 0.006-1.69). Fe was mainly stored in stipes, while Mn, Zn and Cu were stored in caps, and the translocation factors (TFs) were 0.58 vs. 1.28-1.94. Therefore, stipe Fe showed the highest health risk index (HRI) at 1.28-26.9, followed by cap Cu (1.01-2.33), while 98-100% of the Mn and Zn were risk-free. The higher concentration and greater risk of Fe was attributed to the significant effect of soil Fe content (R = 0.34) and soil pH (R = -0.57). This study suggested that Fe, as an essential mineral, may exert toxic effects via the consumption of T. matsutake from high geochemical background areas.

Rapid estimation of soil Mn content by machine learning and soil spectra in large-scale

Manganese (Mn) is an essential element in both plants and the human body; however, traditional methods for monitoring Mn in soil are costly and inefficient. As such, it is necessary to establish a model for environmental research uses that can accurately predict soil Mn content over large areas. This study aims to develop a multilayer perceptron (MLP) model capable of accurately predicting Mn content in diverse soils based on visible and near-infrared (VNIR) spectroscopy. A dataset containing 18,675 soil samples compiled from the Land Use and Coverage Area Frame Survey was used to train and adjust the model, following which the optimal model was applied globally. The correlation coefficient, root mean square error, and mean absolute error values for the optimal model on the test set were 0.76, 140.52, and 97.30, respectively. Feature importance analysis revealed crucial spectral bands at approximately 1400, 2200, 2300, and 2400–2500 nm, which enabled the Mn content to be estimated. The presence of these spectral bands indicates that clay minerals, H2O, and OH− groups had significant influence on Mn content. The MLP model developed can effectively identify regions with potentially high or low soil Mn content. With improvement of the spectral database, this model can provide effective assistance in evaluating soil Mn distribution at the global scale.

Weed Species’ Diversity and Composition as Shaped by the Interaction of Management, Site, and Soil Variables in Olive Groves of Southern Greece

Gaining a comprehensive understanding of how weed communities respond to both environmental and human-induced factors is of paramount importance in developing effective and ecologically sound weed control strategies. The objectives of the current research were to (1) assess the effect of the main weed management practices used in Greek olive groves on weed species’ diversity; (2) explore the filtering effect of management, site, and soil variables in determining weed species’ composition; and (3) shed light on the association between weed species’ composition and the diversity of the understory vegetation of olive groves. To accomplish these objectives, winter weed species’ coverage was assessed in 116 olive groves, both conventional and organic, distributed across three provinces in southern Greece. The investigation encompassed 29 explanatory variables, categorized into three groups: soil (22), management practices (6), and site conditions (1). It was confirmed that glyphosate use may lower biodiversity and species richness; however, this trend was not universal. In fact, the negative influence of the presence of Oxalis pes-caprae L. on species richness and diversity far outweighed the effect of spraying glyphosate. Redundancy analysis (RDA) revealed that among the 29 variables used to describe the ecological niche, eight (i.e., Mn, Mg, chemical spraying, mowing, rotary tiller, grazing, irrigation, and elevation) were significant and explained 21.5% of the total variation in weed species’ data. Interestingly, the soil Mn concentration was identified as the most influential one, highlighting the importance of soil micronutrients in determining weed species’ composition. The variation partitioning procedure demonstrated that the effect of the management variables on weed species’ composition accounted for 2.2 times the variance of soil variables and 4.5 times the variance of elevation. The present findings might help to enhance optimal management in olive groves that can sustain the biodiversity of flora and, in turn, provide various ecosystem services to agro-ecosystems.

Diversity and botanical composition of native species in the Pampa biome in vineyards cultivated on soils with high levels of copper, zinc and manganese and phytoremediation potential

Viticulture allows the preservation of native species inside vineyards in the Pampa biome. However, phytosanitary treatments in these areas can increase the levels of Cu, Zn and Mn. The study aimed to (i) verify the influence of Cu, Zn and Mn contents in Pampa biome soils; (ii) identify variables related to Cu, Zn and Mn that most contribute to the variation in richness, diversity, and dry matter production of native vegetation, (iii) investigate the phytoremediation potential of species present in vineyards. Botanical composition, Cu, Zn, Mn available in the soil, and plant nutritional composition in two vineyards (V1 and V2) and native field (NF) were evaluated. Vineyards showed higher Cu, Zn and Mn contents in the soil, resulting in the lowest biomass, richness, and diversity of native species. Mn in tissue was the most important variable in explaining the variation in dry matter. Zn in the soil helped to explain the difference in species richness and diversity. P concentration in tissue was important in elucidating the variation in species diversity. Paspalum plicatulum and Paspalum notatum have potential for phytostabilization of metals in vineyards.

Field pea/spring triticale mixtures influenced iron and manganese concentrations in soil and forage plant uptake

AbstractThe use of legumes for cultivation in mixtures with cereals has a positive effect not only on the yield of green mass but also on its chemical composition. This research evaluated the influence of different seeding rate proportions of field pea (Pisum sativum L.) with spring triticale (×Triticosecale Wittm.) at different growth stages on Fe and Mn contents in soil and plants. The two factors examined in the study were as follows: proportional seeding rate of components in the mixture (kg ha−1)—field pea/spring triticale 240:0, 180:55, 120:110, 60:165, and 0:220; and harvest stage—field pea flowering versus field pea flat green pod. The greatest soil contents of Fe at 952 mg kg−1 and Mn at 102.2 mg kg−1 were found in the soil at 0–30 cm depth following harvest of field pea. The greatest dry matter concentrations of Fe at 146 mg kg−1 and Mn at 68.5 mg kg−1 in the mixtures were determined in the forage of field pea/spring triticale at 180:55 harvested at the field pea flat green pod stage. The field experiment demonstrated that a 180:55 mixture of pea and spring triticale should be recommended for cultivation. This mixture provides the greatest Fe and Mn content in soil and forage for cattle.

Application of Machine Learning for Prediction and Monitoring of Manganese Concentration in Soil and Surface Water

This study explored the application of machine learning, specifically artificial neural network (ANN), to create prediction models for manganese (Mn) concentration in soil and surface water (SW) on the island province with two open mine pits overflowing to two major rivers that experienced mining disasters. The two ANN models were created to predict Mn concentrations in soil and SW from 12 and 14 input parameters for soil and SW, respectively. These input parameters were extracted from extensive field data collected at the site during sampling program in 2019, 2021, 2022, and initially processed with spatial analysis via geographic information system (GIS). All datasets were then divided for model training and validation, using 85% and 15% ratio, respectively. Performance evaluation of each model with mean absolute percentage error (MAPE) and root mean squared error (RMSE) confirmed the accuracy of both models. The soil Mn model achieved MAPE and RMSE values of 2.01% and 23.98, respectively. The SW Mn model was split into two models based on SW Mn values within the 0–1 mg/L range and &gt;1 mg/L range. The SW Mn model for &gt;1 mg/L performed better with MAPE and RMSE of 4.61% and 0.17, respectively. Feature reduction was also conducted to identify how the models will perform if some input parameters were excluded. Result showed sufficient accuracy can still be obtained with the removal of 4–5 input parameters. This study and these models highlight the benefit of ANN to the scientific community and government units, for predicting Mn concentration, of similar environmental conditions.

Interaction Mechanism of Fe, Mg and Mn in Karst Soil-Mango System

Manganese (Mn), an essential trace element for plants in which it is involved in redox reactions as a cofactor for many enzymes, represents an important factor in environmental contamination. Excess Mn can lead to toxicity conditions in natural and agricultural sites. Manganese toxicity is one of the most severe growth limiting factors in acid soil, which accounts for 21% of the total arable lands in China. The more significant part of Mn-toxicity is its interactions with other mineral elements, in particular with phosphorus (P), calcium (Ca) and iron (Fe). The application of P or Ca can be beneficial in the detoxification of manganese, whereas Mn seems to interfere with Fe metabolism. Manganese toxicity varies with plant species, nutrients, and the soil environment. Mango is the main economic fruit in the karst area of the subtropical region of China. The karst soil in the mango orchard is characterized by high Fe, Mn and Mg. In order to explore the interaction among Fe, Mg, and Mn in karst soil and mango systems under high Mn conditions, a typical mango orchard in the karst depression landform in Baise in southern China was selected to study the effects of Fe and Mg on the toxic expression of Mn in mango plants and the interaction mechanism of Fe-Mn-Mg in mango plants. The results show that: (1) the mango growth status is closely correlated with Fe2+ (active iron) and Mg under the same soil Mn concentration; (2) The black spots on mango leaves were mainly caused by Fe and Mn. There is a lot of Fe3+ and Mn3+ in the black spots, which accounts for more than 90% of the total; (3) In addition, the studies also showed that the Fe and Mg inhibited the expression of Mn toxicity in mango. Conclusively, the interaction effect of Fe, Mn, and Mg is an important factor that affects mango growth, which can indicate the status of the soil and plants.

Trace elements apportionment in forage, soil, and livestock in rangeland ecosystems along climatic gradients

BackgroundAlpine meadows, typical steppes, and deserts are among the globally important rangeland types that are generally distributed along temperature and precipitation gradients. Mineral losses caused by grazing are one of the key factors that can lead to instability or even degradation of these rangeland ecosystems. MethodsWe examined the concentrations of Cu, Fe, Mn, and Zn in soil, forage, and livestock dungs from diverse rangeland types in northwest China, to determine the relationships between these trace elements (TEs) concentrations and climatic factors (i.e., temperature, precipitation, and humidity), and to evaluate the potential risks of TEs deficiencies or excesses in these rangeland ecosystems. ResultsForage Zn concentrations in forage of all three types of rangeland, and Cu concentrations in forage of the alpine meadow did not meet the growth requirements of grazing livestock. Concentrations of Cu, Fe, and Mn in forage and Fe, Mn, and Zn in livestock dungs had quadratic parabola relationships with temperature, precipitation, and humidity, but the relationships between climate factors and Cu, Fe, and Mn concentrations in soil were not significant. In addition, the abilities of the plant to absorb Cu, Fe, and Zn from soil were stronger in the typical steppe than that in the alpine meadows and desert. Also, the abilities of livestock to return TEs to soil were stronger in the alpine meadow than that in the typical steppe and desert. ConclusionWe derived a conceptual mode that the ratio of TE concentrations of the plant to soil and of livestock dung to forage represents the abilities of plants to absorb TEs from the soil matrix and livestock to return TEs to soil or to absorb TEs from forage, respectively. Results indicate potentially more serious risks of TEs deficiencies, especially that of Zn than previously considered in typical steppes and desert rangelands.

THE INFLUENCE OF SEASONS ON METAL BIOACCUMULATIONAND OXIDATIVE STRESS IN SENTINEL ORGANISMS IN SOUTHAFRICAN URBAN FORESTS

Variations in Al, Fe and Mn concentrations in soil, leaf litter, moss, lichen and pill millipedes, as well as the induced oxidative stress effect of metals on the organisms, between the dry and the wet season within two Afromontane forests in the Western Cape were investigated. The two forests in the closest proximity of the Cape Town city centre and urban pollution sources were chosen to determine the difference of metal contamination between the dry, hot and cold, wet season. Three sampling sites were chosen within each forest at different altitudes on Table Mountain, as well asa control site, where the soil, leaf litter and each organism were randomly collected in both the dry and the wet seasons for metal and biochemical analysis. The metals in the wet season in both of the forests showed higher concentrations, as did the forest closest to the Cape Town city centre.This is indicative of higher levels of pollution due to increased anthropogenic activities in the wetseason. Oxidative stress in organisms was apparent in the varying tGSH levels, of which the dryseason mostly revealed the higher concentrations. Oxidative lipid damage (measured as MDA) levels were generally increased during the wet season when the metal concentrations were higher as a result of prominent brown haze episodes in winter. Urban forest ecosystems in urban cities may suffer irreparable damage resulting from metal contamination, more so in the colder wet season.

Geo-Accumulation Index of Manganese in Soils Due to Flooding in Boac and Mogpog Rivers, Marinduque, Philippines with Mining Disaster Exposure

This paper presents the effects of flooding on the accumulation of manganese (Mn) in soils within proximity of the Boac and Mogpog rivers in Marinduque of The Philippines. Marinduque, an island province in the Philippines, experienced two catastrophic tailings storage facility (TSF) failures in the 1990s that released sulfide-rich tailings into the two major rivers. The Philippines experiences 21–23 typhoons every year, 11 of which pass thru Marinduque that causing inundation of floodplain areas in the province. A flood hazard map developed using LiDAR DEM was utilized for the Boac and Mogpog rivers for an accurate representation of flooding events. A portable X-ray fluorescence spectrometer (pXRF) and a Hannah multi-parameter device were used for the on-site analyses of Mn concentration and water physico-chemical properties, respectively. Spatial grid mapping with zonal statistics was employed for a comprehensive analysis of all the data collected and processed. Correlation analysis was carried out on Mn concentrations in soil and surface water, electrical conductivity (EC), total dissolved solids (TDS), pH, temperature, curve number (CN), and flood heights. The curve number indicates the runoff response characteristic of the Mogpog-Boac River basin. The results show that 40% of the total floodplain area of Boac and Mogpog were subjected to high hazards with flood heights above 1.5 m. The Mn content of soils had a statistically significant moderate positive correlation with flood height (r = 0.458) and a moderate negative correlation with pH (r = −0.438). This condition suggested that more extensive flooding promotes Mn contamination of floodplain soils in the two rivers, the source of which includes the mobilization of Mn-bearing silt, sediments, and mine drainage from the abandoned mine pits and TSFs. There is also a strong negative correlation between pH and Mn concentrations in surface water, a relationship attributed to the solubilization of Mn-bearing precipitates based on geochemical modeling results. Using Muller’s geo-accumulation index, 77.5% of the total floodplain of the two rivers was identified as “moderately contaminated” with an average Mn soil content of 3.4% by weight (34,000 mg/kg). The Mn contamination map of floodplain soils in the Mogpog and Boac rivers described in this study could guide relevant regional, national, and local government agencies in planning appropriate intervention, mitigation, remediation, and rehabilitation strategies to limit human exposure to highly contaminated areas.

Broussonetia papyrifera fruits as a potential source of functional materials to develop the phytoremediation strategy

Broussonetia papyrifera is an important environmental restoration tree emerging in recent years, who has a good ability to resist heavy metal pollution such as Mn and Cd. In order to explore the content changes of different components of B. papyrifera’s fruits under Mn stress, the content characteristics of the chemical compounds and antioxidant capacity were determined in the study, comparing Mn mining area with control. The content of total sugar and total protein of B. papyrifera fruits in the Mn mining area is not significantly different from that in the control area, including fruits of different development stages (p > 0.05). However, the content of polyphenols, flavonoids, anthocyanins, K, Ca, Mg and Mn are significantly different (p < 0.05). Except for ABTS, the antioxidant capacity of B. papyrifera’s fruits in the Mn mining area is significantly different from that in the control area (p < 0.05). At the same time, the antioxidant activity of the fruits is closely related to the content of most chemical compounds, especially protein, sugar, polyphenols, anthocyanin, Mg and Mn. Although the Mn content in soil is low, the content of Mn in the rhizosphere soil shows a closer correlation with the content of the analyzed compounds and antioxidant activity of B. papyrifera fruits. The results show that the fruits of B. papyrifera have important development potential to be a source of polyphenols, flavonoids, anthocyanin and minerals in the process of phytoremediation, which may contribute to phytoremediation strategies.

Effects of nitrogen addition on plant manganese nutrition in a temperate steppe

AbstractBackgroundManganese (Mn) is an essential nutrient for plant growth and a key factor driving litter decomposition. Nitrogen (N) deposition is expected to enhance soil Mn availability via soil acidification, and subsequently to increase plant Mn concentrations.AimsWe aimed to quantify the responses of Mn concentrations in green and senesced shoots at both species and community levels to N addition, and determine whether N addition would decrease Mn retranslocation efficiency during plant senescence.MethodsWe examined the changes of Mn concentrations in soil and in green and senesced shoots of all plant species across multiple N addition rates ranging from 0 to 50 g N m−2 y−1 in a temperate steppe after six years treatments. Plant Mn retranslocation efficiency were quantified at species, life form, and community levels. The relationship between plant Mn nutritional parameters and soil Mn availability across the N addition gradient was analyzed.ResultsThere were positive correlations between plant Mn concentrations and N addition rates for most species. Relative to the control plots, community‐level mean Mn concentration in green and senesced shoots in the plots received the highest level of N addition increased by 137.50% (from 0.19 mg kg−1 to 0.08 mg kg−1) and 187.50% (from 0.23 mg kg−1 to 0.08 mg kg−1), respectively. There was no correlation between Mn retranslocation efficiency and N addition rates at species, life form and community levels. Plant Mn status was weakly correlated with soil Mn concentrations for most species.ConclusionsPlant Mn retranslocation showed conserved responses to increasing N addition rates, which would be an adaptive strategy for plants in face of N‐induced higher soil Mn availability.

Exogenous application of Mn significantly increased Cd accumulation in the Cd/Zn hyperaccumulator Sedum alfredii.

Sedum alfredii is a Cd/Zn hyperaccumulator native to China, which was collected from a mined area where Mn content in soil was extremely high, together with Zn and Cd content. We investigated the tolerance and accumulation ability of Mn and its possible association with Cd hyperaccumulation in this plant species by using MP-AES, SR-μ-XRF, and RT-PCR. The results showed that the hyperaccumulating ecotype (HE) S.alfredii exhibited high tolerance to Mn and accumulating around 10,000 and 12,000mgkg-1 Mn in roots and shoots, respectively, without exhibiting toxicity under 5000mgkg-1 Mn treatment for 4 weeks. Exposure to Cd significantly reduced plant uptake of Mn. In contrast, exogenous Mn application significantly improved root uptake and root-to-shoot translocation of Cd, resulting in the increased Cd accumulation in the shoots of HE S.alfredii. SR-μ-XRF analysis demonstrated that high Mn (20μM) exposure resulted in higher intensities of Cd localized in both stem vascular bundles and cortex, as well as leaf mesophyll cells, than in those treated with low Mn levels (0.2μM or 2.0μM). RT-PCR analysis of several genes possibly involved in Mn/Cd transportation showed that expression of SaNramp3 in roots was significantly reduced under high Mn exposure. These results suggested a significant interaction between Cd and Mn in the HE S.alfredii plants, possibly through their competition for transporters and theoretically provided a strategy to improve the efficiency of Cd extraction from polluted soils by this plant species, after using appropriate nutrient management of Mn.

Regional Diversity of Maritime Antarctic Soil Fungi and Predicted Responses of Guilds and Growth Forms to Climate Change.

We report a metabarcoding study documenting the fungal taxa in 29 barren fellfield soils sampled from along a 1,650 km transect encompassing almost the entire maritime Antarctic (60–72°S) and the environmental factors structuring the richness, relative abundance, and taxonomic composition of three guilds and growth forms. The richness of the lichenised fungal guild, which accounted for 19% of the total fungal community, was positively associated with mean annual surface air temperature (MASAT), with an increase of 1.7 operational taxonomic units (OTUs) of lichenised fungi per degree Celsius rise in air temperature. Soil Mn concentration, MASAT, C:N ratio, and pH value determined the taxonomic composition of the lichenised guild, and the relative abundance of the guild was best predicted by soil Mn concentration. There was a 3% decrease in the relative abundance of the saprotrophic fungal guild in the total community for each degree Celsius rise in air temperature, and the OTU richness of the guild, which accounted for 39% of the community, was negatively associated with Mn concentration. The taxonomic composition of the saprotrophic guild varied with MASAT, pH value, and Mn, NH4+-N, and SO42− concentrations. The richness of the yeast community, which comprised 3% of the total fungal community, was positively associated with soil K concentration, with its composition being determined by C:N ratio. In contrast with a similar study in the Arctic, the relative abundance and richness of lichenised fungi declined between 60°S and 69°S, with those of saprotrophic Agaricales also declining sharply in soils beyond 63°S. Basidiomycota, which accounted for 4% of reads, were much less frequent than in vegetated soils at lower latitudes, with the Ascomycota (70% of reads) being the dominant phylum. We conclude that the richness, relative abundance, and taxonomic composition of guilds and growth forms of maritime Antarctic soil fungi are influenced by air temperature and edaphic factors, with implications for the soils of the region as its climate changes during the 21st century.

Manganese accumulation and tolerance in Eucalyptus globulus and Corymbia citriodora seedlings under increasing soil Mn availability

Manganese (Mn) is a nutrient that can cause phytotoxicity if above a threshold concentration. Acid soils are prone to excessive Mn levels that under certain environmental conditions may increase availability and exacerbate deleterious effects on plants. Apart from oxidative stress, excess Mn usually affects photosynthetic apparatus. Nonetheless, some plants are known to tolerate high Mn contents without negative consequences. We carried out a greenhouse experiment with two eucalypt species (Eucalyptus globulus and Corymbia citriodora), treated with four Mn additions in the soil substrate (0, 50, 150 and 300 mg kg−1) for 18 weeks. Before harvest, shoot height and the chlorophyll a fluorescence parameters were assessed, then leaves, stems and roots were sampled, weighted and nutrients determined. Manganese addition increased height for both species while biomass production remained unchanged, even though foliar concentrations ranged from 600 to 800 mg kg−1 at the highest Mn in soil. High root-to-shoot translocation of Mn was observed, yet—contrary to our hypothesis—photochemical efficiency of photosystem II was barely affected, except for the slight decrease in C. citriodora under 300 mg kg−1 Mn. The capacity to accumulate high Mn in photosynthetic tissues without chlorophyll damage seems to be a feature of Mn tolerant species. Nutritional imbalances such as magnesium decrease due to Mn exposure was observed, but not enough to cause deficiency. Both eucalypt species were therefore tolerant to high Mn concentrations in soil, especially E. globulus, and have the potential to be employed in reforestation/afforestation of lands with high risk of Mn phytotoxicity.

Toxic effects of soil manganese on tropical trees

Manganese (Mn) is toxic to plants at high concentrations with recent evidence indicating slowed tropical-tree growth by high soil Mn concentrations. However, little information exists about the physiological effects of high Mn on tropical trees. We investigated physiological responses and toxicity effects of Mn in several tropical tree species. Given potential physiological interactions between Mn and phosphorus (P), we also hypothesised that P could be used to detoxify Mn. We conducted two controlled-growth experiments on seedlings of five tree species from Panama. The first experiment tested the effects of increasing concentrations of soil Mn; the second examined whether P availability mitigates Mn toxicity. Severe Mn toxicity occurred at 5 mM Mn, with toxicity symptoms in some species at 1.5 mM Mn. Responses to Mn toxicity were species-specific and depended on P supply. One species intolerant of high Mn responded by using P for detoxification; others either tolerated or detoxified Mn by another mechanism. We conclude that Mn can be toxic to tropical tree species and Mn toxicity increases P demand in some species. Other species are broadly tolerant of high Mn, suggesting that Mn tolerance might contribute to differences in species distributions and growth of tropical trees.

Toxic levels of manganese in an acidic Cambisol alters antioxidant enzymes activity, element uptake and subcellular distribution in Triticum aestivum.

In the Montado system, in Portuguese Alentejo region, some Eutric Cambisols are known to promote manganese (Mn) toxicity in wheat. Variation on bioavailable Mn concentration depends on soil acidity, which can be increased by natural events (e.g. waterlogging) or human activity (e.g. excess use of chemical fertilizers). The effect of increasing soil Mn on crop element uptake, element distribution and oxidative stress was evaluated on winter wheat (Triticum aestivum). Plants were grown for 3 weeks in an acidic Cambisol spiked with increasing Mn concentrations (0, 45.2 and 90.4mg MnCl2/Kg soil). Calcium (Ca), phosphorus (P), magnesium (Mg) and Mn were quantified in the soil solution, root and shoot tissues and respective subcellular fractions. The activity of the antioxidant enzymes ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), guaiacol peroxidase (GPX) and superoxide dismutase (SOD) were determined in extracts of wheat shoots and roots. Overall, increase in soil bioavailable Mn inhibited the uptake of other elements, increased the Ca proportion in the root apoplast, promoted the translocation of Mn and P to shoot tissues and increased their proportion in the shoot vacuoles. Wheat roots showed greater antioxidant enzymes activities than shoots. These activities decreased at the highest soil Mn concentration in both plant parts. Wheat roots appear to be more sensitive to oxidative stress derived from excess soil Mn and promote Mn translocation and storage in shoot vacuoles, probably in Mn and P complexes, as a detoxification strategy. Improvement in wheat production, in acidic soils, may rely on the enhancement of its Mn detoxification strategies.

Concentration of Heavy Metals in Soils under Cemetery Occupation in Amazonas, Brazil

ABSTRACT The study aimed to quantify Cd, Cr, Cu, Ni, Pb, Zn, Al, Fe, and Mn concentrations in soils due to cemetery occupation in the Brazilian Amazon in order to assess the potential of environmental contamination. Atotal of 45 samples were collected in the 0.00–0.40, 0.40–0.80, and 0.80–1.20m layers, with trenches opened in a Gleysol (Cemetery - I) and Cambisol (Cemetery - II) to determine Fe, Al, Mn, Cr, Cu, Cd, Ni, Pb, and Zn contents. Chemical and particle size analyses were also performed. Soil sample digestion was based on the EPA 3051A method and metal concentrations were determined by ICP-OES. The results were submitted to descriptive statistics, control charts, and multivariate statistics by principal components. The effective increase in Fe, Cr, Cu, Ni, Pb, and Zn concentrations indicates ahigher potential of contamination by these metals due to cemetery activity, with concentrations above the recommended reference values for Brazilian Amazon sediment soils. Soil shows ability to return, resilience, to the chemical quality and natural concentrations of potentially toxic elements with the inactivation of cemetery activities. The clay fraction and organic matter are the main coordinators of metal dynamics in soil profiles.

Occurrence and environmental impact of industrial agglomeration on regional soil heavy metalloid accumulation: A case study of the Zhengzhou Economic and Technological Development Zone (ZETZ), China

Abstract To clarify whether industrial agglomeration affects soil heavy metalloid (HM) accumulation and pollution and whether industrial agglomeration results in less soil HM pollution than in areas without industrial agglomeration, an investigation of the HM concentration and pollution in soils in an industrial agglomeration area, the national Zhengzhou Economic and Technological Development Zone (ZETZ), was conducted. Determinations of the Hg, Pb, Cr, As, Zn, Cd, Ni, Co, Cu and Mn concentrations in soils were performed using inductively coupled plasma-mass spectrometry, inductively coupled plasma-atomic emission spectrometry and atomic fluorescence spectrometry (ICP-MS, ICP-AES). The contamination factor (CF) of different elements, and the comprehensive pollution load index (PLI) of multiple HMs were calculated. Furthermore, to quantify the relationships between industrial output and soil HM accumulation, the concept of the toxic equivalent mass of soil HM accumulation per capital output (TEM) is proposed. The key results are as follows: (1) The average concentrations for all the studied HMs were higher than the local background concentration (BC) values. The distribution of the soil HM concentrations showed significant spatial heterogeneity, and the regions with the highest soil HM concentrations were generally affected by local industrial activities. (2) The pollution load index (PLI) values indicate that the extent of the human impacts on the soil environment in the study area correspond to the slight pollution level as a whole. (3) The PLI values, the total accumulated mass of soil HMs over time per million industrial capital output (PMt), and the TEM values for the ZETZ, Kaifeng Carbon Factory (KCF), and Wanyang Lead Smelter (WLS) were subjected to comparative analyses, with the KCF and WLS showing markedly higher levels than the ZETZ. Accordingly, although slight HM accumulation occurred in the soil of the ZETZ, the industry-related accumulation of soil HMs in the ZETZ is significantly less than that in the KCF and WLS; thus, industrial agglomeration may be effective for reducing the intensity of HM accumulation.