Biogeochemical Assessment of Trace Metal and Mercury Pollution in Two Tropical Estuaries Impacted by Multiple Pollution Sources.

This study evaluated trace metal pollution in sediments and fishes from two tropical estuarine systems in Northeast Brazil: the Santa Cruz Channel Estuary (ITAP) and the Sirinhaém River Estuary (SIR). An integrative approach combining several environmental and toxicological assessment indices was employed. In general, concentrations of trace metals in sediments-including cadmium (Cd), chromium (Cr), lead (Pb), and zinc (Zn) in ITAP and Cd, Cr, Pb, Zn, and total mercury (THg) in SIR-were below the Threshold Effect Levels (TEL), suggesting a low likelihood of adverse effects on benthic biota. However, elevated THg concentrations exceeding the Probable Effect Levels (PEL) were observed at specific sites within the ITAP system, indicating a high potential for ecological harm. Environmental quality indices identified THg and Copper (Cu) pollution in ITAP and Cu pollution in both estuaries. Ecological risk and Nemerow multi-factor indices suggested that SIR is subject to low ecological risk, with Cu being the dominant pollutant. In contrast, ITAP exhibited high ecological risk driven primarily by Cu and THg. Among the species examined, Bairdiella ronchus and Centropomus undecimalis, which are frequently consumed by local populations in ITAP, exhibited Hg concentrations exceeding established safety thresholds for human consumption. The application of multiple assessment indices provided a comprehensive understanding of environmental degradation caused by anthropogenic pressures, particularly in the Santa Cruz Channel. These findings underscore the need for effective public policy enforcement aimed at long-term pollution monitoring and safeguarding food security for local communities.