Settling particles and underlying sediments collected at 1,2.5 and 4 km off the metropolitan Buenos Aires coastwere analyzed to evaluate the sources and accumulationof resolved (RES), unresolved (UCM), and biomarkeraliphatic hydrocarbons. Sedimentary aliphatic concentrations(RES 0.11-14
![](/images/entities/mgr.gif)
g·g
-1; UCM 0.1-800
![](/images/entities/mgr.gif)
g·g
-1) includedvariability associated with north-south gradients and anexponential offshore reduction. Highest concentrations wereregistered close to Buenos Aires port and sewer, comparedto cleaner northern
stations and southward sites affectedby a seaward residue transport. Sediment traps deployedin the sewer area revealed large hydrocarbon (38 and319 mg·m
-2·day
-1, RES and UCM) and total organic carbonfluxes (29 ± 26 g·m
-2·day
-1). The composition of RESand hopanes evaluated by principal component analysisindicated a consistent offshore gradient defined by the relativecontribution of lower vs higher molecular
weightcomponents. Distant sites showed decreasing proportionsof petrogenic
n-C
17-26 alkanes, isoprenoids, and C
20-27terpanes and relative enrichment of
n-C
27,29,31,33 terrestrialplant alkanes and C
31-33 homohopanes. Sedimenthydrocarbon profiles showed an average 2-fold reductiondown to 20 cm depth with preferential removal of lowermolecular
weight components and enrichment of
n-C
23-35alkanes and hopanes. Sediment inventories and trapdepositional fluxes indicate the accumulation of 5800-9700 tons of aliphatic hydrocarbons in the top 0-5 cmsediments with a strong interfacial alteration and selectivepreservation of refractory components:
n-C
13-22 (1.0%)< isoprenoids (3.2%) <
n-C
23-35 (6.1%) < hopanes (47%)~ UCM (50%), compared to intermediate stability of organiccarbon (12%) and quantitative preservation of polychlorinatedbiphenyls (PCBs) (91%).