Metal(loid)s (As, Cd, Cu, and Zn) in three fish species from a dam after a mine-tailing spill: differential bioaccumulation and potential health risk

The failure of a tailings dam occurred in January 2013 at the Santa María de Otáez mining region (Mexico) released a spill (~ 300,000 m3) on Los Remedios River, which was transported through the San Lorenzo River, and finally to El Comedero (EC) dam. The concentrations of metal(loid)s in the muscle, liver, gills, and guts of three fish species (Cyprinus carpio, Oreochromis aureus, Micropterus salmoides) collected from EC dam were examined twenty months later to assess the performance of the cleaning operations. The bioaccumulation patterns of the metal(loid)s in the tissues were different in the three fish species. Tilapia had the highest Cd (11.23 ± 8.53 µg g-1) and Cu (871 ± 1261 µg g-1) concentrations in the liver, as well as As concentration (83.6 ± 61.7 µg g-1) in the gut, while the highest Zn concentration (745 ± 356 µg g-1) was measured in the gills of the carp. Such variability can be caused by the variant bioavailability of the metal(loid)s and by the feeding habits of each species; and also by the fact that some metals are essential and better regulated by organisms than other non-essential. Compared to a study of tilapia carried out 90 days after mine spill, a decrease was evident in the liver for As, Cd, Cu, and Zn by 129, 5, 10, and 1.7 times, respectively. This revealed that cleaning operations were more efficient for As. The target hazard quotient and the hazard index were < 1, which indicates there will be no risk of consuming muscle in moderated rations of the three fish species.

High accumulation of metals and metalloids in the liver of the blue tilapia (Oreochromis aureus) during a massive mortality event induced by a mine tailing spill

In this study, the concentration of six metal(loid)s was examined in the fish Oreochromis aureus collected from El Comedero dam during a massive mortality event induced by a mine tailing spill. A major spill (~ 300,000 m³) of waste was released into the San Lorenzo River System following a rupture in the tailing dam of a mining plant in NW Mexico; consequently, the discharged material flowed into El Comedero dam. The accumulation of metal(oid)s in the tissues of O. aureus showed higher levels in the liver than in the guts and muscle. Concentrations in the liver were high (As, 1.1-1063; Cd, 8.9-392; Cu, 372-59,129; Hg, 0.46-19.79; Se, 8.7-748; and Zn, 116-820 μg g^-1), revealing that these fish were exposed to high concentrations of these elements. The mortality of fish could have resulted from the combined effect of the six analyzed metal(loid)s, as well as other residues present in mine tailings.

Monitoring of inland waters for culturing shrimp Litopenaeus vannamei: application of a method based on survival and chemical composition

This study evaluated the suitability of 21 inland waters (16 well waters and 5 surface waters) from Northwest Mexico via short- (48 h) and medium-term (28 days) tests using postlarvae (PL18) of Litopenaeus vannamei. In the short test, survival was assessed at 48 h after shrimp were placed in groups of 10 postlarvae into 2-L containers of inland water, to which they had been previously acclimated. The second, medium-term test consisted of four replicates with 10 postlarvae, and each group was placed in 15-L containers with the treatment water. Weights (initial and final) and survival were evaluated weekly for 28 days. In those waters for which the short test was positive and the medium-term test was negative and which also had a deficiency of potassium and/or magnesium, a third test was conducted. These last waters were supplemented with salts, and the shrimp survival and weights (initial and final) were recorded for 28 days. The water samples from San Jose, Mochicahui, Sinaloa River, Caimanero inner Lagoon, La Pipima, Campo Santa Fe, Escopama, and Fitmar had >60% survival in the short test. The Caimanero inner Lagoon water had the highest survival (87.5 ± 9.6%) and final mean weight (201.3 ± 86.2 mg). In the third test, it was found that shrimp in the water from La Pipima, Campo Santa Fe, and Fitmar exhibited 100% survival for 2 weeks. Finally, in this work, a decision tree to evaluate the suitability of low-salinity water for shrimp farming was proposed, which can be applied in other regions.