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Zinc

  • January 2013
DOI:10.1007/978-94-007-4470-7_17
Authors:
Jelle Mertens at European Precious Metals Federation
Jelle Mertens
  • European Precious Metals Federation
Erik Smolders at KU Leuven
Erik Smolders
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Abstract

Zinc (Zn) is naturally present in all soils in typical background concentrations 10–100 mg Zn kg–1. Human activities have enriched topsoils with Zn through atmospheric depositions, fertilization and sewage sludge application. Zinc contaminated soils with negative impact on the soil ecosystem are found around Zn smelters, near Zn mining sites and under galvanized structures. The solubility of Zn in soils is almost invariably controlled by sorption reactions. Pure Zn minerals (carbonates, silicates, hydroxides) have been detected at high total soil Zn concentrations (>1,000 mg Zn kg−1) but are rarely controlling Zn solubility. Zinc is specifically sorbed as Zn2+ on pH-dependent binding sites of oxyhydroxides and organic matter and, at high concentrations, by ion exchange reactions on clay minerals. In general, soil solution Zn concentrations increase fivefold per unit pH decrease. Zinc deficiency for agricultural crops is found in about 1/3 of worldwide soils due to low total Zn concentrations and/or high pH. Soils containing less than 0.5 mg Zn kg−1 diethylenetriaminepentaacetic acid (DTPA) extractable Zn are potentially Zn deficient. Dietary Zn deficiency in humans is often associated with Zn deficient soils and crop Zn biofortification is now a global initiative through selection for Zn-efficient crops or judicious fertilisation. Zinc toxic soils are less widespread than deficient ones. Risk of Zn toxicity is manifested by effects on soil dwelling organisms, i.e. plants, invertebrates and soil microorganisms. Toxic effects are identified at total Zn concentrations 100 to >1,000 mg kg−1 and toxicity decreases with increasing soil CEC. Risk assessments of Zn have proposed maximal additions as low as 26 mg added Zn kg−1 in the EU to maintain soil ecosystem structure and function.
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All content in this area was uploaded by Jelle Mertens on Jun 22, 2015
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All content in this area was uploaded by Jelle Mertens on Jun 22, 2015
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... Basic igneous rocks contain up to 240 mg kg −1 Zn, generally higher than silica-rich igneous rocks that contain up to 140 mg kg −1 (Nagajyoti et al., 2010). The Zn concentration in sedimentary rocks can range between 20 and 200 mg kg −1 , with the highest Zn concentrations in clays and shales (Alloway, 2008;Mertens and Smolders, 2013). At the local scale, relatively higher Zn concentrations can be found in Europe due to the presence of geological deposits rich in Zn, for example, in Ireland, Poland, Sardinia, Portugal, and Spain (Salminen et al., 2005). ...
... This inert Zn pool is occluded within the mineral soil matrix, and becomes only available for organisms by slow weathering processes (Rodrigues et al., 2010). Rock types that result in clayey soils upon weathering contain the highest Zn content (Alloway, 2008;Mertens and Smolders, 2013), explaining the higher Zn levels in clay soils compared to sandy soils found in Europe with our model. ...
Spatial assessment of topsoil zinc concentrations in Europe
Article
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Zinc (Zn) is essential to sustain crop production and human health, while it can be toxic when present in excess. In this manuscript, we applied a machine learning model on 21,682 soil samples from the Land Use and Coverage Area frame Survey (LUCAS) topsoil database of 2009/2012 to assess the spatial distribution in Europe of topsoil Zn concentrations measured by aqua regia extraction, and to identify the influence of natural drivers and anthropogenic sources on topsoil Zn concentrations. As a result, a map was produced showing topsoil Zn concentrations in Europe at a resolution of 250 m. The mean predicted Zn concentration in Europe was 41 mg kg-1, with a root mean squared error of around 40 mg kg-1 calculated for independent soil samples. We identified clay content as the most important factor explaining the overall distribution of soil Zn in Europe, with lower Zn concentrations in coarser soils. Next to texture, low Zn concentrations were found in soils with low pH (e.g. Podzols), as well as in soils with pH above 8 (i.e., Calcisols). The presence of deposits and mining activities mainly explained the occurrence of relatively high Zn concentrations above 167 mg kg-1 (the one percentile highest concentrations) within 10 km from these sites. In addition, the relatively higher Zn levels found in grasslands in regions with high livestock density may point to manure as a significant source of Zn in these soils. The map developed in this study can be used as a reference to assess the eco-toxicological risks associated with soil Zn concentrations in Europe and areas with Zn deficiency. In addition, it can provide a baseline for future policies in the context of pollution, soil health, human health, and crop nutrition.
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... With increased amounts of soil organic matter, the availability of Zn may decrease due to increased adsorption , or increase due to soil organic matter mineralization (Tella et al., 2016) or formation of soluble organic Zn complexes (Hernandez-Soriano et al., 2013). Different chemical extractions have been formulated to evaluate soil Zn availability for plant uptake, the associated yield response to Zn fertilisation Lindsay and Norvell, 1978;Mertens and Smolders, 2013) and Zn concentrations in the edible plant parts . For example, a soil test with diethylenetriaminepentaacetic acid (DTPA) as chelating agent is widely used for near-neutral and calcareous soils (Lindsay and Norvell, 1978), while others have used acidic soil extracts such as HCl or Mehlich 3 (M3) for more acidic soils (Alloway, 2009;Mertens and Smolders, 2013). ...
... Different chemical extractions have been formulated to evaluate soil Zn availability for plant uptake, the associated yield response to Zn fertilisation Lindsay and Norvell, 1978;Mertens and Smolders, 2013) and Zn concentrations in the edible plant parts . For example, a soil test with diethylenetriaminepentaacetic acid (DTPA) as chelating agent is widely used for near-neutral and calcareous soils (Lindsay and Norvell, 1978), while others have used acidic soil extracts such as HCl or Mehlich 3 (M3) for more acidic soils (Alloway, 2009;Mertens and Smolders, 2013). The DTPA and M3 soil extracts are currently most often used for Zn fertiliser recommendations and critical extractable soil Zn levels have been derived below which a positive maize yield response to Zn-fertilisation can be expected. ...
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... Zinc content in contaminated soils occurs in immobile forms (Sharma et al., 2013). Studies show that most agricultural and industrial activities result in a high fraction (>70%) of inaccessible Zn by plants with availability (exchangeable and carbonate forms) of >30% (Mertens and Smolders, 2013;Liao et al., 2019). ...
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Excess potentially toxic elements (PTEs), including arsenic (As), cadmium (Cd), lead (Pb), and zinc (Zn), above permissible limits in the environment, have detrimental effects on trophic levels. Hence, imperative to devise advertent measures to address this situation, especially in the soil ecosystem: the major reservoir of many PTEs. Using aerial plant parts (shoot) to accumulate As, Cd, Pb, and Zn - hyperaccumulators are considered a permanent approach to PTE removal from soils. This communication expatiated the principles that govern the hyperaccumulation of plants growing on As, Cd, Pb, and Zn-contaminated soils. The contribution of soil microbial communities during hyperaccumulation is well-elaborated to support the preference for this remediation approach. The study confirms a flow direction involving PTE uptake–translocation–tolerance–detoxification by hyperaccumulators. Rhizosphere microbes exhibit a direct preference for specific hyperaccumulators, which is associated with root exudations, while the resultant formation of chelates and solubility of PTEs, with soil physicochemical properties, including pH and redox potential, promote uptake. Different compartments of plants possess specialized transporter proteins and gene expressions capable of influx and efflux of PTEs by hyperaccumulators. After PTE uptake, many hyperaccumulators undergo cellular secretion of chelates supported by enzymatic catalysis and high transport systems with the ability to form complexes as tolerance and detoxification mechanisms. The benefits of combining hyperaccumulators with beneficial microbes such as endophytes and other rhizosphere microbes for PTE removal from soils are vital in enhancing plant survival and growth, minimizing metal toxicity, and supplying nutrients. Inoculation of suitable rhizosphere microbes can promote efficient cleaning of PTEs contaminated sites utilizing hyperaccumulator plants.
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... Nevertheless, soil fertility and crop nutrition research in SSA has mainly focused on macronutrients, i.e. nitrogen (N), phosphorus (P) and potassium (K) ( . For example, a soil test with diethylenetriaminepentaacetic acid (DTPA) as chelating agent is widely used for near-neutral and calcareous soils (Lindsay and Norvell, 1978), while others have used acidic soil extracts such as HCl or Mehlich-3 (M3) for more acidic soils (Alloway, 2009;Mehlich, 1984;Mertens and Smolders, 2013). The DTPA and M3 soil extracts are currently most often used for Zn fertiliser recommendations and critical extractable soil Zn levels have been derived below which a positive maize yield response to Zn-fertilisation can be expected. ...
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Preprint
Full-text available
  • Sep 2022
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Article
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Article
Zinc adsorption by goethite in the presence of 0.1M sodium chloride was found to occur at pH values well below the isoelectric point of the goethite when the surface was positive and the zinc in a cationic form. This confirms data already presented by Forbes et al. (1976). The presence of phosphate or zinc on the goethite surface was found to increase slightly the adsorption of zinc and phosphate respectively. Depending on the pH value, the total adsorption could be larger than for either ion in the absence of the other and the capacity of the surface for each of the ions. As suggested by Stanton and Burger, a surface complex may be formed.
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