Geochemical Baseline and Contamination Level Assessment of Antimony (Sb) in Sediment around Agbaou Gold Mine, Côte d’Ivoire

Agbaou is one of the most recent gold mine exploitation sites in Côte d’Ivoire. Little studies are discussed on the geochemical baseline concentration of trace metals in the wetland sediments around Agbaou gold mine. The main objectives of this study were to establish geochemical baseline values and to assess the pollution status of antimony (Sb). The geochemical baseline concentration of Sb (GBCSb) was estimated using linear regression method. In this study, total Sb concentration was analysed in sediment (10 sediment samples) collected around Agbaou gold mine site. The average Sb concentration was 5.63 ± 2.50 µg.g-1 ranging from 2.50 to 11.3 µg.g-1. The spatial distribution of Sb showed a tendency to accumulate near gold mine site. Moreover, the GBCSb (5.72 µg.g-1) was slightly higher than the average concentration found in sediments. GBC of Sb was used to calculate the anthropogenic contribution rate (R) which exhibited a positive value (R > 0) for all samples, indicating that the sediments were influenced by gold mining activities. Due to lack of local baseline value in the study area, the GBCSb obtained could be used as reference value for Sb contamination level assessment in the sediments.

In situ continuous monitoring of dissolved gases (N2, O2, CO2, H2) prior to H2 injection in an aquifer (Catenoy, France) by on-site Raman and infrared spectroscopies: instrumental assessment and geochemical baseline establishment

An original monitoring system allowing in situ and continuous quantification of gases dissolved in an aquifer and combining Raman and infrared fiber sensors. The gas baseline was established before an experimental simulation of hydrogen injection.

Sedimentological, Mineralogical and Geochemical Features of Late Quaternary Sediment Profiles from the Southern Tuscany Hg Mercury District (Italy): Evidence for the Presence of Pre-Industrial Mercury and Arsenic Concentrations

Southern Tuscany (Italy) is an important metallogenic district that hosts relevant S-polymetallic deposits that have intensely been exploited for centuries. Consequently, potential toxic elements, such as Hg and As, are widely distributed in the surrounding environment. In this paper, an extensive sedimentological, mineralogical and geochemical study of two Late Quaternary sediment profiles, partially outcropping along the coast of southern Tuscany (Ansedonia area), was carried out to evaluate the contents and mobility of Hg and As with the aims to contribute to the definition of the geochemical baseline of southern Tuscany before the human intervention and evaluate the potential dispersion of these harmful elements. The sedimentological, mineralogical and geochemical (major elements) features revealed that the studied profiles are mostly related to the local geological characteristics and the Quaternary geological history of the area. The concentrations and the normalized patterns of trace and rare earth elements highlighted the absence of any anthropogenic activity. This implies that the studied samples are to be regarded as good proxies for evaluating the geochemical baseline of southern Tuscany before the intense mining activity. The enrichment factors (EF) of most trace elements were indeed lower or close to 2, indicating a variability close to the average concentration of the Upper Continental Crust (UCC), while other elements slightly enriched, such as Pb, were in agreement with the natural baseline reported for southern Tuscany. Mercury and As displayed EF values >40 when compared to the average contents of UCC, although they decrease down to 4 when compared to the suggested baseline for southern Tuscany. The higher Hg and As contents detected in this study, inferred to natural sources, evidenced (i) the great natural variability occurring in largely mineralized areas and (ii) the importance of estimating reference environmental parameters in order to avoid misleading interpretations of the detected anomalies. Moreover, the results of leaching test on sediment samples denoted a relatively low mobility of Hg and As, suggesting that these elements are preferentially mobilized by transport of clastic sediments and such anomalies may be preserved for relatively long times in Quaternary sediments. However, leachable Hg (0.6–9.7 μg/L) and As (2.1–42.2 μg/L) concentrations are significantly high when compared to those of the Italian limit for groundwater (1 µg/L for Hg and 10 µg/L for As). Quaternary sediments from southern Tuscany could then be a potential, though natural, source of Hg and As to groundwater systems.

Assessment, Distribution and Regional Geochemical Baseline of Heavy Metals in Soils of Densely Populated Area: A Case Study

To understand the content, pollution, distribution and source and to establish a geochemical baseline of heavy metal elements in soil under the influence of high-density population, the concentrations of heavy metal elements Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Hg, Pb and Fe were determined in 23 soil samples in Suzhou University, and geo-accumulation index, enrichment factor, principal component analysis, spatial analysis and regression analysis were completed. The results showed the following: The elements Cu and As were slightly polluted, while the other heavy metal elements were not. The elements Cd, Cu, Ni and As in soils were mainly caused by agricultural activities of chemical fertilizer, whereas the elements Zn and Hg were impacted by the chemicals and batteries. The heavy metal elements in the north were lower than in the south of the campus, as a whole. The enrichment of elements Cu, As and Cd was caused by the east–west river on the campus, and the enrichment of the elements Mn, Ni and Zn was induced by the reservoir. Biochemical experiments and vehicle parking influenced the spatial enrichment of Cr, Co and Pb, while domestic waste led to the spatial differentiation of Hg concentrations. The regression curve between heavy metal elements and Fe was established, and the background values of the heavy metals Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Hg and Pb are 50.90, 489.37, 11.76, 37.74, 55.70, 58.22, 20.07, 0.09, 0.08 and 24.13 mg/kg, respectively.

Spatial distribution maps of Cu, Pb, Zn, Cr, As and V in rural soils in northern part of Chile: The use of geochemical baseline values as an index in environmental assessment.

<p>Soil pollution is a worldwide concern and several countries are established guidelines. In the case of Chile, the very diverse soils characteristics along the country made difficult to set guidelines to acceptable levels of potentially toxic elements (PTEs) in soils. However, due to several reasons such as anthropogenic contamination, and increment of erosion rates there is urgency in to establish guidelines values to this parameters. In Chile, the most of abandoned mining wastes are located in the northern part which could negatively have impacted the ecosystem and human health. Thus, in absence of guidelines to PTEs in soils, the use of regional geochemical baseline (GBL) as a reference values could be a first approach to preliminary determine pollution levels of PTEs in soils. The objective of this study was to use the calculated GBL values to determine the influence of mining activities on the levels of PTEs in soils and to determine the spatial distribution maps of PTEs. A regional mapping of soils was conducted in northern part of Chile during 2017-2018 and the pH, electrical conductivity, redox potential and concentration of PTEs was determined. A systematic sampling in a 20,000 square-kilometer area was conducted and 467 rural top and sub soil samples were taken to determine their physical and chemical composition. The content of PTEs was determined by ICP-OES. The GBL values were estimated following the upper-whisker limit method. The pH, electrical conductivity, and redox potential of soils were 4.9-9.5, 10.5-56,000 mS/cm, and 89.7-348.3 mV, respectively. The median concentration of Mn (695.9 mgkg<sup>-1</sup>) was the highest followed by V (148.4 mgkg<sup>-1</sup>), Ni (75.2 mgkg<sup>-1</sup>), Zn (59.7 mgkg<sup>-1</sup>), Cu (59.0 mgkg<sup>-1</sup>), Sb (34.0 mgkg<sup>-1</sup>), As (18.3 mgkg<sup>-1</sup>), Cr (17.9 mgkg<sup>-1</sup>), Sn (17.5 mgkg<sup>-1</sup>), Pb (14.6 mgkg<sup>-1</sup>), Co (13.0 mgkg<sup>-1</sup>), Cd (12.9 mgkg<sup>-1</sup>), Hg (3.6 mgkg<sup>-1</sup>), and Mo (3.3 mgkg-1). The GBL for Cu, Zn, V, As, Mo, and Sb were higher than the reported average for world soils. The spatial distribution maps of Cu, Pb, Zn, Cr, As and V were used to determine pollution levels. Statistical correlation models showed the influence of either abandoned mining sites or active mining operation on the pollution levels of PTEs in the surrounding soils. The geochemical baseline values could contribute for government decision-makers to choose the best available remediation technologies for the impacted area.</p><p> </p>