Search

Application of chelating and reductive agents in soils can increase the availability of potentially toxic elements facilitating their uptake by plants. This study discusses the effect of single or combined EDTA (E), sodium dithionite (SD), and olive mill wastewater (OMW) treatments on As, Pb, and Zn mobility over time in a heavily contaminated mine-affected soil. Soil samples were incubated for 1, 3, 7, 15, 30, 60, and 90 days and at each incubation time the easily mobilizable fraction obtained by (NH 4 ) 2 SO 4 (for As) and CH 3 COOH (for Pb/Zn). The results showed that the highest availability of As (mean value 41 mg kg -1 ) was observed for the EDTA treatment followed by E+OMW (mean value 32 mg kg -1 ) and E+SD+OMW (mean value 27 mg kg -1 ). For Pb and Zn, significantly higher available concentrations were obtained by the EDTA and E+OMW treatments (mean values 2532 mg kg -1 and 1427 mg kg -1 for Pb and Zn respectively) followed by the E+SD (mean value 2259 and 1333 mg kg -1 for Pb and Zn) and E+SD+OMW treatments (mean value 2388 and 1340 mg kg -1 for Pb and Zn). Moreover, the incubated for 90 days soil samples subjected to two different sequential extraction protocols (SEPs): Wenzel (for As) and BCR (for Pb, Zn, Fe, and Mn). The results showed that As, Pb, and Zn mobility was mainly regulated by the amorphous Fe oxides. Our findings suggest that OMW application in soils should focus more attention since when combined with other amendments produced contradictory results.

Emissions from civil airports are similar to those observed in industrial and urban areas. While air pollution and noise levels are regularly monitored and assessed, information on the status of heavy metals in soils close to airport facilities is limited. In this study, we monitored and assessed heavy metal distribution in soils close to Athens International Airport (AIA) in Attica, Greece. Following a grid sampling scenario, topsoil samples were collected from 86 sites at the periphery of AIA and total and available forms of Cu, Zn, Fe, Mn, Ni, Cr, Pb, and Ba concentrations were determined in aqua regia and DTPA soil extracts, respectively. Median concentration values for both metal forms are not considered as particularly high. However, 90th percentile concentration values for some metals are high, indicating soil enrichment. Evaluation of enrichment factor (EF) and availability ratio (AR) values and EFs spatial distribution have led to consistent conclusions of secondary and ongoing metal accumulation in the soils of the studied area. Tessier sequential extraction procedure was applied to 10% of the soil samples and the results showed high potential availability of Pb, Mn, Cu, and Ni, further supporting the continuous metal accumulation in the studied soils.

Organic farming has been proposed as an alternative agricultural system to help solve environmental problems, like the sustainable management of soil micronutrients, without inputs of chemical fertilizers. The purposes of this study were: i) to assess Fe, Mn, Zn and Cu bioavailability through the determination of sequentially extracted chemical forms (fractions) and their correlation with foliar micronutrient concentrations in mature organic olive (cv. 'Chondrolia Chalkidikis') groves; ii) to determine the soil depth and the available forms (fractions) by which the 4 metals are taken up by olive trees. DTPA extractable (from the soil layers 0-20, 20-40 and 40-60 cm) and foliar micronutrient concentrations were determined in two organic olive groves. Using the Tessier fractionation, five fractions, for all the metals, were found: exchangeable, bound to carbonates (acid-soluble), bound to Fe-Mn oxides (reducible), organic (oxidizable), as well as residual form. Our results indicated that Fe was taken up by the olive trees as organic complex, mainly from the soil layer 40-60 cm. Manganese was taken up from the exchangeable fraction (0-20 cm); Zinc was taken up as organic complex from the layers 0-20 and 40-60 cm, as well as in the exchangeable form from the upper 20 cm. Copper was taken up from the soil layers 0-20 and 40-60 cm as soluble organic complex, and as exchangeable ion from the upper 20 cm. Our data reveal the crucial role of organic matter to sustain metal (Fe, Zn and Cu) uptake -as soluble complexes-by olive trees, in mature organic groves grown on calcareous soils; it is also expected that these data will constitute a thorough insight and useful tool towards a successful nutrient and organic C management for organic olive groves, since no serious nutritional deficiencies were found., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The Thriassio plain is located 25 km west of Athens city, the capital of Greece. Two major towns (Elefsina and Aspropyrgos), heavy industry plants, medium to large-scale manufacturing, logistics plants, and agriculture comprise the main land uses of the studied area. The aim of the present study was to measure the total and available concentrations of Cr, Zn, Ni, Pb, Co, Mn, Ba, Cu, and Fe in the top soils of the plain, and to asses soil contamination by these metals by using the geoaccumulation index (I geo), the enrichment factor (EF), and the availability ratio (AR) as soil pollution indexes. Soil samples were collected from 90 sampling sites, and aqua regia and DTPA extractions were carried out to determine total and available metal forms, respectively. Median total Cr, Zn, Ni, Pb, Co, Mn, Ba, Cu, and Fe concentrations were 78, 155, 81, 112, 24, 321, 834, 38, and 16 × 10(3) mg kg(-1), respectively. The available fractions showed much lower values with medians of 0.4, 5.6, 1.7, 6.9, 0.8, 5.7, 19.8, 2.1, and 2.9 mg kg(-1). Though median total metal concentrations are not considered as particularly high, the I geo and the EF values indicate moderate to heavy soil enrichment. For certain metals such as Cr, Ni, Cu, and Ba, the different distribution patterns between the EFs and the ARs suggest different origin of the total and the available metal forms. The evaluation of the EF and AR data sets for the soils of the two towns further supports the argument that the EFs can well demonstrate the long-term history of soil pollution and that the ARs can adequately portray the recent history of soil pollution.