SEGH Articles

# Fate of smelter dusts in soils

14 October 2016
Winner of the best poster prize at the SEGH meeting in Brussels. Alice Jarosikova, PhD student from Charles University in Prague, describes her research on fate of smelter-derived dust particles in soils.

Areas in the vicinity of metal smelters are inevitably exposed to metal(loid)-bearing particulates, which are emitted and dispersed in the environmental compartments. Especially surrounding soils represent an important sink for the most of these anthropogenic emissions.

1. Dust emitted from the copper smelter

The main objective of our study is to identify the fate of smelter dusts when deposited in soils as well as to clarify subsequent dynamics of smelter-related contaminants in the soil systems, which can interact with water and biota. We use a long-term in situ experimental approach, where polyamide bags filled with smelter dusts are placed for incubation into different depths of soil profiles. Our current 4-year in situ experiment has been initiated in October 2013 in four contrasting soil types and under different vegetation covers using the methodology described by Ettler et al. (2012). We have compared the weathering rates of smelter dusts in the following soils: neutral-to-alkaline Chernozem developed on loess (grass cover), neutral-to-slightly acidic Cambisol (grass cover), and acidic Cambisols developed under the beech and spruce forests. Our study materials are (i) arsenic rich fly ash (composed mostly of arsenolite, As2O3, galena, PbS and gypsum, CaSO4·2H2O) and (ii) copper slag (enriched in Cu, Zn and Pb). We collect experimental bags each 6 months and soil columns are vertically sampled (each 5 cm of depth) using physical rings and when possible, soil pore water is collected using Rhizon samplers. We perform mineralogical analysis on smelter dusts (to identify changes in phase composition), supplemented with bulk chemistry of dusts and soil samples coupled to As speciation analysis in soil pore waters and extracts.

2. Soil sampling after the smelter dust incubation using physical rings

Despite the fact that our field experiment is just in the middle and data collection is still in progress, we find that fly ash particles are highly reactive in soil systems and their dissolution is increasing over time. Arsenic leaching associated with the highest fly ash dissolution was the most significant in soil developed under the beech forest mainly due to specific seepage conditions leading to more rapid flush regime (higher moisture than for other soil types). Observation under the scanning electron microscopy (SEM) indicated that the fly ash incubated in soil under the beech was the most weathered with etched arsenolite surfaces and secondary formation of a complex metal-bearing arsenate phase.

Field experimental studies are always more difficult than laboratory investigations, because a number of parameters cannot be fully controlled. However, they are more suitable for understanding complex processes in real-life scenarios. We are looking forward to the next sampling campaign in October 2016 J

Alice Jarošíková

PhD candidate at Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Czech Republic

Reference:

Ettler, V., Mihaljevič, M., Šebek, O., Grygar, T., Klementová, M., 2012. Experimental in situ transformation of Pb smelter fly ash in acidic soils. Environ. Sci. Technol. 46, 10539-10548.

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• Concentration, fractionation, and ecological risk assessment of heavy metals and phosphorus in surface sediments from lakes in N. Greece 2020-01-13

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The presence of phosphorus (P) and heavy metals (HMs) in surface sediments originating from lakes Volvi, Kerkini, and Doirani (N. Greece), as well as their fractionation patterns, were investigated. No statistically significant differences in total P content were observed among the studied lakes, but notable differences were observed among sampling periods. HM contents in all lakes presented a consistent trend, i.e., Mn > Cr > Zn > Pb > Ni > Cu > Cd, while the highest concentrations were recorded in Lake Kerkini. Most of the HMs exceeded probable effect level value indicating a probable biological effect, while Ni in many cases even exceeded threshold effects level, suggesting severe toxic effects. P was dominantly bound to metal oxides, while a significant shift toward the labile fractions was observed during the spring period. The sum of potentially bioavailable HM fractions followed a downward trend of Mn > Cr > Pb > Zn > Cu > Ni > Cd for most lakes. The geoaccumulation index Igeo values of Cr, Cu, Mn, Ni, and Zn in all lakes characterized the sediments as “unpolluted,” while many sediments in lakes Volvi and Kerkini were characterized as “moderately to heavily polluted” with regard to Cd. The descending order of potential ecological risk $$E_{\text{r}}^{i}$$ was Cd > Pb > Cu > Ni > Cr > Zn > Mn for all the studied lakes. Ni and Cr presented the highest toxic risk index values in all lake sediments. Finally, the role of mineralogical divergences among lake sediments on the contamination degree was signified.