Abstract
As the number of legal and illegal gold mining sites increases in the Andes–Amazonia region, integrative methods to evaluate the effects of mining pollution on freshwater ecosystems are of paramount importance. Here, we sampled water and sediments in 11 sites potentially affected by gold mining activities in the Napo province (Ecuador). The environmental impacts were evaluated using the following lines of evidence (LOEs): water physicochemical parameters, metal exposure concentrations, macroinvertebrate community response (AAMBI), and toxicity by conducting bioassays with Lactuca sativa and Daphnia magna. Dissolved oxygen and total suspended solids were under (<80%) and above (>130 mg/Ls) quality standards 65% of the sites. Ag, Al, As, Cd, Cu, Fe, Mn, Pb, and Zn in water and V, B, and Cr in sediments were detected above quality standards at sampled sites. Nine out of eleven sites were classified as having bad environmental quality based on the AAMBI. L. sativa seed germination in both water (37% to 70%) and sediment (0% to 65%) indicate significant toxicity. In five sites, neonates of D. magna showed a 25% reduction in survival compared to the control. Our integrated LOEs index ranked sites regarding their environmental degradation. We recommend environmental impact monitoring of the mining expansion at the Andes–Amazonia region using multiple LOEs.
Highlights
The Amazon basin has been historically impacted by mining activities [1,2,3]
dissolved oxygen (DO) and total suspended solids (TSS) were above the thresholds set by TULSMA, CCME, and EPA (130 mg L−1, respectively)
Cd was above quality standards for all sites, and in Sites P2 and P6, it was detected above the limit for chronic contamination
Summary
The Amazon basin has been historically impacted by mining activities [1,2,3]. Illegal mining has recently expanded in several parts of the Amazon basin, which has resulted in an environmental impact whose extension is difficult to ascertain [4,9]. Given the importance of gold mining to Ecuador’s economy and the proliferation of mining concessions, information on the environmental impacts caused by this activity is crucial. Even though artisanal small-scale gold mining (i.e., mining without heavy machinery and granted to small companies or local communities) is the most common authorized concession, industrial gold mining represents 98% of the total territory for the exploitation of gold in the Napo province (33,718 ha).
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