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Gold mining not only introduces mercury (Hg) contamination to soils but also facilitates the mobilization of other toxic substances, including arsenic (As). This study assessed the total content, chemical species, and bioavailable fraction of As in surface soils impacted by mining residues during frequent flooding. Analysis of 207 soil samples across the floodplain region of La Mojana, Colombia, screened to 2 mm with polyethylene mesh, revealed significant correlations (p < 0.05) between inorganic As, the residual phase, sulphur (S), iron (Fe), manganese (Mn), and aluminum (Al), indicating associations with sulfides and oxyhydroxides of Fe and Mn. The origin of toxicity was linked to suspended materials transported by rivers during flooding in areas with intense mining activity. Sites with better oxidizing conditions exhibited a higher presence of phases associated with amorphous and crystalline oxides in non-flooded areas. Although the bioavailable fraction was minimal in flooded sites, reducing conditions facilitated As mobility, resulting in higher concentrations in deeper soil layers, particularly as As(III). The contamination factor (CF) ranged from 1.3 to 11.1, and the geochemical index (Igeo) ranged from -0.2 to 2.9, indicating a moderate to high As contamination level in soils. This poses potential health risks, considering the agricultural use of these soils.

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In recent years, the use of pesticides has increased considerably for pest control and to improve agricultural production. The rural areas of several municipalities of department of Cordoba, north of Colombia, are highly dependent on agriculture. In this study, a questionnaire and field observations about pesticide use and genotoxic damage through the comet assay in peripheral blood lymphocytes of children who live near crop fields was evaluated. Damage Index for Comet Assay (DICA) of five children populations exposed to pesticides (mean of 94.73±53.95 for the municipality of Monteria, the higher damage in this study) were significantly Higher than control children population (mean of 7.56±7.39). Results showed the damage index in children exposed group was higher than in the control group. An inadequate management of pesticides, as well as incorrect disposal of toxic wastes was observed in the study zone.

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The objective of this work is the validation and implementation of an analytical method for the determination of arsenic chemical species in rice grain samples using High-performance liquid chromatography coupled to a hydride generator with atomic fluorescence detector (HPLC-HG-AFS). The extraction protocol developed was based on HNO3 0.28 M (90 °C, 2 h), microwave-assisted. The results showed recovery percentages of arsenite (As (III)) (99-101%), arsenate (As (V)) (91-96%), dimethylarsinic acid (DMA) (92-102%) and monomethylarsonic acid (MMA) (94-97%). The precision of the method presented coefficients of variation lower than 7% and 8% for repeatability and reproducibility respectively. The detection limits were 2.5, 3.75, 7.5 and 4.0 µg kg-1 for As (III), As (V), DMA and MMA respectively. The proposed methodology is reliable for the quantification of As species, because they are conserved during the extraction.•The extraction protocol developed was based on Microwave-assisted acid extraction.•This methodology offers good sensitivity, precision, accuracy, detection and quantification limits.•It was successfully applied to determination of arsenic chemical species in rice grains.

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The concentrations of polycyclic aromatic hydrocarbons and heavy metals were evaluated in shallow sediments, water, fish and seabird samples from the Cispata Bay, Colombia. The heavy metals concentrations in the sediment was in the following order: Cu>Pb>Hg>Cd. The heavy metal concentration was different (p<0.05) in juvenile and adult birds. High concentrations of mercury were registered in the seabird (10.19±4.99mgkg-1) and fish (0.67µgg-1) samples. The total concentration of polycyclic aromatic hydrocarbons ranged from 7.0-41ngg-1 in sediment, 0.03-0.34ngmL-1 in water samples, 53.24ngg-1 in fish, and 66ngg-1 in seabirds. The high concentrations of heavy metals in seabirds may be explained by their feeding habits. The presence of polycyclic aromatic hydrocarbons in the Cispata Bay may be due to hydrocarbon spills during oil transport at the nearby oil port.

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