No abstract

No abstract

To test the effectiveness of coated and uncoated Zn fertilizers prepared with commercial zinc ethylenediaminetetraacetate (Zn−EDTA) and zinc lignosulfonate (Zn−LS), maize (Zea mays L.) was greenhouse cultivated in calcareous soils dosed with 5, 10, and 15 mg·kg-1 Zn. Crop yield increased from 25 g per pot in control to 42 and 39 g per pot when 15 mg·kg-1 Zn was added by applying Zn−EDTA-3 and Zn−LS-0 fertilizers, respectively. Although big amounts of Zn were taken by plants, concentrations in soil increased from 43 to 55 and 57 mg·kg-1 when 15 mg·kg-1 Zn as Zn−EDTA-3 and Zn−LS-3 was applied. Rosin coating improved the performance of Zn−EDTA fertilizers but scarcely did in fertilizers with Zn−LS. A large part of Zn applied remained in the soil in forms easily available to plants (water soluble plus exchangeable, organic complexed, and DTPA-extractable Zn), more so when the source of Zn was zinc lignosulfonate. Positive, significant correlations were obtained between the variables, yield, Zn concentration, and Zn uptake by the plant with respect to the available Zn and the first two sequentially extracted fractions (water soluble plus exchangeable and organically complexed). The Zn uptake by maize could be fairly accurately predicted from the sequential fractioning in the soil after harvesting using an equation obtained through multiple regression analysis. Keywords: Calcareous soil; maize response; slow release; soil Zn status; Zn−EDTA; zinc lignosulfonate

A total of 32 samples of surficial soil were collected from 16 playground areas in Madrid (Spain), in order to investigate the importance of the geochemistry of the soil on subsequent bioaccessibility of trace elements. The in vitro bioaccessibility of As, Co, Cr, Cu, Ni, Pb and Zn was evaluated by means of two extraction processes that simulate the gastric environment and one that reproduces a gastric + intestinal digestion sequence. The results of the in vitro bioaccessibility were compared against aqua regia extractions ("total" concentration), and it was found that total concentrations of As, Cu, Pb and Zn were double those of bioaccessible values, whilst that of Cr was ten times higher. Whereas the results of the gastric + intestinal extraction were affected by a high uncertainty, both gastric methods offered very similar and consistent results, with bioaccessibilities following the order:As -Cu -Pb -Zn > Co > Ni > Cr, and ranging from 63 to 7 %. Selected soil properties including pH, organic matter, Fe and CaCC>3 content were determined to assess their influence on trace element bioaccessibility, and it was found that Cu, Pb and Zn were predominantly bound to organic matter and, to a lesser extent, Fe oxides. The former fraction was readily accessible in the gastric solution, whereas Fe oxides seemed to recapture negatively charged chloride complexes of these elements in the gastric solution, lowering their bioaccessibility. The homogeneous pH of the playground soils included in the study does not influence trace element bioaccessibility to any significant extent except for Cr, where the very low gastric accessibility seems to be related to the strongly pH-dependent formation of complexes with organic matter. The results for As, which have been previously described and discussed in detail in Mingot et al. (Chemosphere 84: 1386-1391, indicate a high gastric bioaccessibility for this element as a consequence of its strong association with calcium carbonate and the ease with which these bonds are broken in the gastric solution. The calculation of risk assessments are therefore dependant on the methodology used and the specific environment they address. This has impacts on management strategies formulated to ensure that the most vulnerable of society, children, can live and play without adverse consequences to their health.

No abstract

The authors discuss the geochemical behavior of arsenic (As), antimony (Sb), and selenium (Se) in urban gardens and the human health implications associated with urban agriculture. A total of 42 samples from 7 urban gardens in Madrid, Spain, were collected from the top 20 cm of soil. Concentrations of As, Sb, and Se and the main soil properties (i.e., total iron, pH, texture, calcium carbonate, and organic matter) were determined. A significant correlation was found between As and Sb and calcium carbonate, indicating the possibility of surface adsorption or ligand exchange with the carbonate group. Also, Sb seemed to form stable chelates with soil organic matter. On the other hand, Se showed a significant association with clay and iron content. The concentration of Sb in soil exceeded the recommended value for agricultural use in 70% of the urban gardens. A human health risk assessment resulted in acceptable levels of both noncarcinogenic and carcinogenic risks (although with elevated values of the latter), with As as the main risk driver and soil and food ingestion as the main exposure pathways. The numerical results of the risk assessment should be interpreted with caution given the considerable uncertainties in some exposure variables and the lack of quantitative values for the suspected carcinogenicity of Sb and Se. Environ Toxicol Chem 2017;36:544-550. © 2016 SETAC.

No abstract

No abstract