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.

 

Keep up to date

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Editorial 2018-12-11
  • Chemical fractionation of heavy metals in fine particulate matter and their health risk assessment through inhalation exposure pathway 2018-12-11

    Abstract

    Samples of PM2.5 were collected from an urban area close to a national highway in Agra, India and sequentially extracted into four different fractions: water soluble (F1), reducible (F2), oxidizable (F3) and residual fraction (F4) for chemical fractionation of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni) and lead (Pb). The metals were analyzed by inductively coupled plasma optical emission spectroscopy in each fraction. The average mass concentration of PM2.5 was 93 ± 24 μg m−3.The total concentrations of Cr, Pb, Ni, Co, As and Cd in fine particle were 192 ± 54, 128 ± 25, 108 ± 34, 36 ± 6, 35 ± 5 and 8 ± 2 ng m−3, respectively. Results indicated that Cd and Co had the most bioavailability indexes. Risk Assessment Code and contamination factors were calculated to assess the environmental risk. The present study evaluated the potential Pb hazard to young children using the Integrated Exposure Uptake Biokinetic Model. From the model, the probability density of PbB (blood lead level) revealed that at the prevailing atmospheric concentration, 0.302 children are expected to have PbB concentrations exceeding 10 μg dL−1 and an estimated IQ (intelligence quotient) loss of 1.8 points. The predicted blood Pb levels belong to Group 3 (PbB < 5 μg dL−1). Based on the bioavailable fractions, carcinogenic and non-carcinogenic risks via inhalation exposure were assessed for infants, toddlers, children, males and females. The hazard index for potential toxic metals was 2.50, which was higher than the safe limit (1). However, the combined carcinogenic risk for infants, toddlers, children, males and females was marginally higher than the precautionary criterion (10−6).

  • Effects of steel slag and biochar amendments on CO 2 , CH 4 , and N 2 O flux, and rice productivity in a subtropical Chinese paddy field 2018-12-07

    Abstract

    Steel slag, a by-product of the steel industry, contains high amounts of active iron oxide and silica which can act as an oxidizing agent in agricultural soils. Biochar is a rich source of carbon, and the combined application of biochar and steel slag is assumed to have positive impacts on soil properties as well as plant growth, which are yet to be validated scientifically. We conducted a field experiment for two rice paddies (early and late paddy) to determine the individual and combined effects of steel slag and biochar amendments on CO2, CH4, and N2O emission, and rice productivity in a subtropical paddy field of China. The amendments did not significantly affect rice yield. It was observed that CO2 was the main greenhouse gas emitted from all treatments of both paddies. Steel slag decreased the cumulative CO2 flux in the late paddy. Biochar as well as steel slag + biochar treatment decreased the cumulative CO2 flux in the late paddy and for the complete year (early and late paddy), while steel slag + biochar treatment also decreased the cumulative CH4 flux in the early paddy. The biochar, and steel slag + biochar amendments decreased the global warming potential (GWP). Interestingly, the cumulative annual GWP was lower for the biochar (55,422 kg CO2-eq ha−1), and steel slag + biochar (53,965 kg CO2-eq ha−1) treatments than the control (68,962 kg CO2-eq ha−1). Total GWP per unit yield was lower for the combined application of steel slag + biochar (8951 kg CO2-eq Mg−1 yield) compared to the control (12,805 kg CO2-eq Mg−1 yield). This study suggested that the combined application of steel slag and biochar could be an effective long-term strategy to reduce greenhouse gases emission from paddies without any detrimental effect on the yield.