Linking Environmental Magnetism to Geochemical Studies and Management of Trace Metals. Examples from Fluvial, Estuarine and Marine Systems

Estimating remobilization of potentially toxic elements in soil and road dust of an industrialized urban environment

The mobility of potentially toxic elements (PTEs) is of paramount concern in urban settings, particularly those affected by industrial activities. Here, contaminated soils and road dusts of the medium-size, industrialized city of Volos, Central Greece, were subjected to single-step extractions (0.43 M HNO₃ and 0.5 M HCl) and the modified BCR sequential extraction procedure. This approach will allow for a better understanding of the geochemical phase partitioning of PTEs and associated risks in urban environmental matrices. Based on single extraction procedures, Pb and Zn exhibited the highest remobilization potential. Of the non-residual phases, the reducible was the most important for Pb, and the oxidizable for Cu and Zn in both media. On the other hand, mobility of Ni, Cr, and Fe was low, as inferred by their dominance into the residual fraction. Interestingly, we found a significant increase of the residual fraction in the road dust samples compared to soils. Carbonate content and organic matter controlled the extractabilities of PTEs in the soil samples. By contrast, for the road dust, magnetic susceptibility exerted the main control on the geochemical partitioning of PTEs. We suggest that anthropogenic particles emitted by heavy industries reside in the residual fraction of the SEP, raising concerns about the assessment of this fraction in terms of origin of PTEs and potential environmental risks. Conclusively, the application of sequential extraction procedures should be complemented with source identification of PTEs with the aim to better estimate the remobilization of PHEs in soil and road dust influenced by industrial emissions.

Environmental regeneration processes in the Anthropocene: The Bilbao estuary case (northern Spain)

This work tackles a multidisciplinary study on the recent sedimentary record of the Bilbao estuary (northern Spain), which is the backbone of a city that was primarily industrial and now is widely recognized as a successful example of urban transformation. Although hotspots of heavily polluted materials still remain at the mouth of the two main tributaries (Galindo and Gobelas), the data obtained confirm the ongoing formation of a new layer of sediments (here called "postindustrial zone") covering historically polluted and azoic deposits. It is characterized by largely variable levels of metals and magnetic susceptibility and moderate-to-high abundances of benthic foraminifera. Monitoring of the evolution of this layer appears a key factor to assess environmental improvement and decision-making in polluted estuaries.

Can we document if regulation and Best Available Techniques (BAT) have any positive impact on the marine environment? A case based on a steel mill in Greece

In order to document the impact of Best Available Techniques (BAT) and implementation of regulation on the improvement of the coastal marine environment state, we examined the case of a representative steel mill located at the Gulf of Elefsis (Greece). The evaluation of metal pollution was based on the analysis of major and trace elements, organic carbon, magnetic properties, and sediment accumulation rates, in sediment cores obtained from the vicinity of the plant. The analytical data are discussed in relation to steel production, changes of production routes, and adoption of BAT introduced in order to fulfill EU and national legislation. The results show that the input of pollutants to sediments and the degree of contamination were reduced by approximately 40-70% in the decade 2003-2015 in comparison to the periods of high discharges (1963-2002), whereas the toxicity risks from "high-to-extremely high" were reduced to "medium-to-high."

Distribution of heavy metals around the Barakah nuclear power plant in the United Arab Emirates

Inductively coupled plasma emission spectroscopy was used to measure the concentrations of heavy metals in 58 samples collected from the Barakah nuclear power plant (BNPP) area, UAE. The grain size distribution was symmetric, but the samples ranged from fine to coarse sand. The inverse relationship between grain size and heavy metal contaminations was validated. The pre-operational average heavy metal contaminations around the BNPP were 0.03, 0.40, 1.2, 2.05, 1.66, 1.6, 5.9, 7.3, 7, 8.8, 60, and 2521 ppm for Cd, Mo, Co, Cu, Pb, As, Zn, Ni, V, Cr, Mn, and Fe, respectively. The spatial distribution was more compact in the south compared to the north, with less severe contaminations in the east and west. The negative geoaccumulation indices suggest an uncontaminated area, and the BNPP has minor enrichments. All concentrations were significantly below the safe limits set by the Dutch guidelines. The levels of heavy metals reported in the UAE were lower than levels reported in countries around the world.

Insights into the chemical partitioning of trace metals in roadside and off-road agricultural soils along two major highways in Attica's region, Greece

We report in this study the magnetic properties and partitioning patterns of selected trace metals (Pb, Zn, Cu, Cd, Ni) in roadside and off-road (>200m distance from the road edge) agricultural soils collected along two major highways in Greece. Sequential extractions revealed that the examined trace metals for the entire data set were predominantly found in the residual fraction, averaging 37% for Cd up to 80% for Cu. Due to the strong influence of lithogenic factors, trace metal pseudototal contents of the roadside soils did not differ significantly to those of the off-road soils. Magnetic susceptibility and frequency dependent magnetic susceptibility determinations showed a magnetic enhancement of soils; however, it was primarily related to geogenic factors and not to traffic-derived magnetic particles. These results highlight that in areas characterized by strong geogenic backgrounds, neither pseudototal trace metal contents nor magnetic properties determinations effectively capture traffic-related contamination of topsoils. The vehicular emission signal was traced by the increased acid-soluble and reducible trace metal contents of the roadside soils compared to their off-road counterparts. In the case of Cu and Zn, changes in the partitioning patterns were also observed between the roadside and off-road soils. Environmental risks associated with agricultural lands extending at the margins of the studied highways may arise from the elevated Ni contents (both pseudototal and potentially mobile), and future studies should investigate Ni levels in the edible parts of plants grown on these agricultural soils.