Long-term (1970-2017) temporal trends of polychlorinated biphenyls in fish, settling material, and sediments from populated and remote sites in Río de la Plata estuary, Argentina

Abstract

Temporal trends of polychlorinated biphenyls (PCBs) were studied for detritivorous fish (1996-2017) and settling material (2002-2017) from polluted Buenos Aires coast and for a dated sediment core (1970-2013) from the outer Río de la Plata estuary. In spite of contrasting concentrations [5.3 ± 6.3 μg·g -1 dry weight (dw) for fish, 48 ± 26 ng·g -1 dw for settling material, and 1.5 ± 0.7 ng·g -1 dw for core], all three revealed exponentially decreasing trends over time (97%, 83%, and 83%, respectively). Time trends showed peak maxima coincident with Argentina's period of maximum PCB usage in 1973-1980 (80 cm depth in the core) and pulse discharges related to PCB banning in 2001-2002 (fish) with a lighter signature enriched in less persistent tri- and tetrachlorobiphenyls. The log-linear PCB time trends compare well with the predicted decrease for a high emission scenario from global emission data; the best fit was observed for the less impacted sediment core (-2%·year -1 versus -3%·year -1 for emission scenario). Steeper slopes are observed for the more polluted settling material (-5%·year -1 ) and especially for fish, in which the background decline trend tripled after the 2001 PCB pulse (from -7%·year -1 to -21%·year -1 ). These PCB time trends in related environmental compartments from contrasted sites provide rare evidence for evaluating the effectiveness of control measures in southern South America.