Tracing the anthropogenic lead sources in coastal sediments of SE-pacific (36 degrees Lat. S) using stable lead isotopes.

This study evaluates the main sources of antropogenic Pb in one of the most industrialized centers of the southern Chilean coast (36 degrees S). Stable lead isotopes ((206)Pb/(207)Pb, (208)Pb/(207)Pb) were used to trace main Pb sources to coastal sediments, considering the suspended particulate matter (SPM) from marine (traps), continental (rivers) and industrial effluents, sediments and leaded gasoline samples. The atmospheric input was evaluated through natural collectors; i.e. Raqui-Tubul salt marsh. Results show that marine samples lie on a trend between industrial effluents ( approximately 1.16, 2.44) and natural sources (1.20, 2.50), not related to gasoline consumption. Salt marsh sediments show comparable isotopic composition to marine samples, suggesting the importance of the atmospheric input in the coastal sediments, not related to the leaded gasoline composition either. The continental input (1.18, 2.48) is highly influenced by precipitation, being difficult to separate both sources (atmosphere and continental runoff), showing also similar isotopic ratio to marine sediments. The signal of industrial emissions is masked with the introduction of Pb with higher isotopic ratios, compared to the values observed in the material collected from traps (SPM approximately 1.19, 2.48). The contribution of more radiogenic Pb by the upwelling is suggested.

Input of atmospheric lead to marine sediments in a south-east Pacific coastal area (approximately 36 degrees S).

Atmospheric input of Pb to coastal sediments in the south-east Pacific (approximately 36 degrees S) was estimated using: (1) a salt marsh (non-local emission sources) as a natural collector of atmospheric fluxes and (2) Pb concentrations in rain and air samples, both considered to be representative of the atmospheric input in the study area. A radioisotopic geochronology technique ((210)Pb) was used to estimate the total Pb atmospheric supply to the sediments. The results show that atmospheric input to Concepción Bay accounts for 13-68% of Pb in near shore sediments, evaluated through salt marsh and rain, both showing comparable results. Consequently, there are other relevant Pb sources to explain the higher concentrations in this area. Sediments in the shelf are subject to important influence of upwelling waters, estimated by Salamanca [Sources and sinks of (210)Pb in Concepción Bay, Chile (1993) PhD thesis, Marine Science Research Center, State University of New York at Stony Brook, USA] using (210)Pb. The atmospheric input, however, is mainly responsible for the total Pb input, since the salt marsh (natural atmospheric collector) shows similar Pb(xs) inventories than the shelf, corresponding to a regional-scale Pb emissions.