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The evaluation of metal contamination, ecological risk, bioavailability, and the environmental dredging depth in sediments of two Colombian riverine systems impacted by artisanal and small-scale gold mining (ASGM) and agricultural activities, was conducted following dredging processes. Results indicated significant contamination by Cd and Pb before dredging, based on the contamination factor (CF) and the geoaccumulation index (Igeo). Additionally, Cu and Hg were found to cause adverse biological effects according to sediment quality guidelines. Post-dredging, surface sediments exhibited a moderate ecological risk index (RI, 150-300), primarily due to increased contamination by Hg, Pb, and Cd. To mitigate this ecological risk (RI < 150), the environmental dredging depth needed to exceed 20 cm for all metals. On average, the bioavailable fraction increased 2.3 times within two months after dredging. However, the low environmental risk (%F1 = 1-10) calculated using risk assessment codes (RAC) indicates a potential risk due to metals entering the water column and bioaccumulating in organisms. These findings provide insights into the dynamics of metals and the impact of dredging activities on sediments in the Colombian Caribbean coast affected by various anthropogenic activities. The research underscores the importance of integrating sustainable practices in mining and agriculture to protect the ecological integrity of these riverine systems., (Copyright © 2024. Published by Elsevier B.V.)

Objectives: To determine and quantify organochlorine pesticide residues in pasteurized cow's milk distributed in the city of Monteria, Colombia., Materials and Methods: 144 samples were collected and analyzed for six months (June-December 2013) from eight commercial brands identified as A, B, C, D, E, F, G, H. Simple sampling by attribute was carried out monthly. The POC (points of contact) were determined using a gas chromatograph with electron capture detector, with a capillary column RTX-5 (30.0 m long x 0.25 mm internal diameter, 0.25 pm film thickness)., Results: The samples analyzed showed organochlorine pesticides, exceeding the maximum residue limit established by the Codex Alimentarius. The concentrations found were: 0.53; 0.15; 0.57; 0.40; 0.22; 0.20; 0.014; 0.002 and 0.028 mg/Kg of Σα-HCH/β-HCH, γ-HCH, δ-HCH, ΣAldrin/Dieldrin, ΣHeptachlor/Heptachlor epoxide, Endrin, α-chlordane, γ- chlordane and Endosulfan I, respectively. The brand with the highest number of pesticide residues detected during the study was A. The G brand had the highest concentration of total pesticide residues with 1.46mg/Kg. The C and D brands had lower concentrations with 0.72 and 0.0016mg/Kg, and δ-HCH and γ- chlordane, respectively., Conclusions: The samples of pasteurized milk under study had organochlorine pesticides residue levels above the maximum residue limit established by the Codex Alimentarius, indicating a risk to public health, especially in children, which the most vulnerable sub-group.