Bioaccumulation of anthropogenic contaminants by detritivorous fish in the Río de la Plata estuary: 1-aliphatic hydrocarbons.

The temporal variability and bioaccumulation dynamics of C(12-25)n-alkanes, isoprenoids and unresolved aliphatic hydrocarbons (UCM) were studied in a detritivorous fish (Sábalo: Prochilodus lineatus) collected from 1999 to 2005 in the sewage impacted Buenos Aires coastal area. Fish muscles contain huge amounts of n-C(12-25) (165+/-93, 70+/-48 or 280+/-134 microg g(-1), dry, fresh and lipid weight, respectively) and UCM (931+/-560, 399+/-288 and 1,567+/-802 microg g(-1)) reflecting the chronic bioaccumulation of fossil fuels from sewage particulates. On a temporal basis, lipid normalized aliphatic concentrations peaked by the end of 2001-2002 during the rainiest period over the last four decades (1,750 vs. 1,083+/-4.6mm in 1999, 2004 and 2005), reflecting an enhanced exposition due to massive anthropogenic fluxes from Metropolitan Buenos Aires in wet years. The hydrocarbon composition in fish muscles is enriched in n-C(15-17) and isoprenoids relative to a fresh crude oil and settling particulates, with fresher signatures during the 2001-2002 maxima. Fish/settling material bioaccumulation factors (BAFs: 0.4-6.4 dry weight or 0.07-0.94 lipid-organic carbon) plotted against K(ow) showed a parabolic pattern maximizing at n-C(14-18) and isoprenoids. The optimal bioaccumulation window corresponds to highly hydrophobic (log K(ow): 7.2-9.9), intermediate-size C(14-18)n-alkanes and C(15-20) isoprenoids (MW: 198-282; length: 17.9 to 25.4A) with melting points ranging from -19.8 to 28 degrees C. The uptake efficiency is inversely correlated to melting points and increased from 75% for n-C(25) to above 90% for n-C(14-15) and isoprenoids.