Search Results (7)

Huelva is a city in SW Spain with 150,000 inhabitants, located in the proximity of two heavy chemical industry complexes, the highest naturally occurring radioactive material (NORM) waste (phosphogypsum) stacks of Europe and a highly polluted estuary, with elevated cardiovascular disease and cancer mortality rates. This study analyses the association between cumulated exposure levels to 16 metal(loid)s (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, Tl, U, V, and Zn) measured in the toenail of a sample (n = 55 participants) of the general control population of Huelva City who were involved in the MCC-Spain study and the spatial proximity patterns to the local polluting sources. Residents of the city of Huelva have higher levels of Fe, Ni, Cr, Se, As, and Co in their toenails compared to the levels found in populations with similar characteristics living in non-polluted areas. Moreover, the highest concentrations of As, Pb, Cd, Mo, and Se were found in toenails of participants living near the NORM waste stack, while the highest Cu, Zn, and Al contents corresponded to people residing near the industrial area. The spatial distribution of most of the metal(loid)s studied appears to be mainly controlled by anthropogenic factors. Full article

Human activities directly impact estuaries, where the biota is exposed to sediment contamination. A contamination assessment was carried out in several estuaries in the Southern Iberian Peninsula. Sediment samples were analyzed for the presence of metals/metalloids, and bioaccumulation tests were conducted with clams (Ruditapes philippinarum). Huelva Estuary had the highest contamination levels, while the inner bay of Cádiz and the outer stations of the estuaries from Guadiana, Guadalquivir, Palmones, and Guadarranque were the lesser contaminated. All sampling points (except Huelva) had low contamination levels of As and Cd, but they had high concentrations of Cu. The elements Pb, Cd, Zn, Cu, As, and Hg displayed correlations between the concentrations in sediments and the biota. High bioaccumulation of Zn, Cu, and As was observed in Huelva and Barbate. Important insights into the sediment contamination in Southern Iberian Peninsula estuaries suggest greater management and conservation efforts in these critical ecosystems. Full article

The mouth of the Tinto River is located on the southwest coast of the Iberian Peninsula in the northwest of the Gulf of Cadiz. The river flows into an estuarine system shared with the Odiel River, commonly known as the “Ría de Huelva”. In the 1960s, a wide area of ancient salt marshes was transformed by a stockpile of industrial wastes of phosphogypsum, reaching a height of 35 m above the level of the salt marsh at its highest point. Two surveys using high-resolution seismic reflection in conjunction with a parametric profiler were carried out in 2016 and 2018. The purpose of these geophysical studies was the realization of a 3D model of the sedimentary units constituting the most recent filling of the estuary. The records present abundant extrusion structures located on the margins of the waste stockpiles, which break the visible stratification of the surficial units of the estuary. In some sectors, these structures have reached the estuarine surface and have, therefore, a morphological expression on the estuarine floor. The origin of these structures is interpreted as a vertical escape of fluidized sediments from lower units caused by overpressure from stacking. Full article

Past waste disposal practices have left large volumes of sulphidic material stockpiled in a Ramsar wetland site on the Atlantic coast of southwestern Spain, leading to severe land degradation. With the aim of addressing this legacy issue, soil core samples were collected along two transects extending from the abandoned stockpiles to the adjacent marshland and subjected to XRD, SEM-EDS, ICP-OES and ICP-MS analyses. Sulphide oxidation has been shown to be a major driver of acid generation and metal leaching into the environment. The marsh soil receiving acid discharges from the sulphide wastes contains elevated levels (in mg kg⁻¹) of Pb (up to 9838), As (up to 1538), Zn (up to 1486), Cu (up to 705), Sb (up to 225) and Tl (up to 13), which are retained both in relatively insoluble secondary minerals (mainly metal sulphates and oxides) and in easily soluble hydrated salts that serve as a transitory pool of acidity and available metals. By using a number of enrichment calculation methods that relate the metal concentrations in soil and their baseline concentrations and regulatory thresholds, there is enough evidence to conclude that these pollutants may pose an unacceptable risk to human and ecological receptors. Full article

For more than 40 years, the industrial complex which developed near Huelva (in SW Spain) produced a huge amount of phosphogypsum as a waste product of manufacturing fertilizers. This waste was stockpiled in a stack 25 m high, covering 1200 ha of what was once a salt marsh. The weight of that enormous amount of waste produced active subsidence in the underlying sediment. Part of the sediment was injected into the marginal areas, where the load pressure is minor, causing significant vertical movement in the floor of the estuarine channel. This manuscript describes several surficial features using multibeam echosound. A crest formed by cones and a bulge area could be interpreted as injection structures. The evolution of the topographic position of the floor was also analyzed by comparing different records of the estuarine bed in the margins of the stockpile. The data in this work document the changes in the dynamics of the estuary in relation to these vertical movements. These changes in dynamicsled to erosion and deposition in various areas of the bed. Full article

This paper provides new insights into the geochemical cycling of rare earth elements (REEs) in acid sulfate soils developed on salt marsh sediments of the Huelva estuary (Spain) as a result of sulfide mineral oxidation in abandoned ore stockpiles. The study was aimed at determining the REE abundance, fractionation pattern and mineralogical control of the dispersal and retention of REEs in the soil system. Forty-one samples were collected at 13 core sampling sites along two transects extending across the degraded marshland, and they were subjected to XRD, ESEM-EDS and ICP-MS analyses. Measurements revealed that the soil receiving acid discharges has relatively high concentrations of ΣREEs (174.77 ± 19.77 mg kg⁻¹) compared to local baseline concentrations. Shale-normalized REE patterns are generally flat, but a slight middle REE (MREE) enrichment is consistently apparent in all soil samples, involving relatively low La_N/Gd_N ratios (0.83 ± 0.08) and Gd_N/Lu_N ratios up to 1.42. The convex-upward REE pattern supports the possibility that iron oxy-hydroxide minerals play an important role in MREE retention through adsorption and co-precipitation mechanisms. Efflorescent sulfate salts left on the topsoil by the evaporation of acid waters show a strong depletion of light REEs (La_N/Gd_N = 0.16 ± 0.10) and act as a temporary reservoir of labile MREEs and heavy REEs during dry periods. Full article

Peña de Hierro, located in southwest Spain, encompasses the springs and headwaters for the Rio Tinto River that emerge above normal faults and has been mined for its rich sulfide ore since 2500 BC. The springs are typically characterized by an orange coloration, typical pH of ~2.33, and contain elevated concentrations of heavy metals that are produced by acid rock drainage (ARD). ARD is a natural phenomenon that results from chemolithoautotrophs metabolizing the sulfide ore. Mining has amplified the magnitude of the acidity and concentrations of heavy metals evidenced within sedimentary cores from the Huelva estuary. Acidity, redox state, hydrochemistry and isotopic analyses were examined for the purpose of characterizing the subsurface flows and determining the interconnectivity of the groundwaters. Previous studies have documented the geochemistry of the springs, dating a select few, yet many springs remain uncharacterized. Acidity presented spatial variability throughout the field area, caused by extensive sulfide interactions which generated and modified the pH. Redox exhibited a large range of values due to oxygen diffusivity though the fracture network. The surrounding geology is highly heterogeneous because of intensive deformation during the Variscan and Tertiary periods, and this heterogeneity is shown in the varied aqueous chemistry. Fractionation patterns observed in δ²H and δ¹⁸O values predominantly reflected enrichment by intensive evaporation and depletion in δ¹⁸O as a result of the proposed sulfatic-water model for Rio Tinto’s hydrogeology. The analysis illustrates minimal hydrologic interconnectivity, evidenced by the extensive physical and chemical contrasts within such a small proximity. Full article