Human-induced metals accumulation in sediments of an industrialized bay of northern Chile. An enrichment and ecological risk assessment based on preindustrial values.

Environmental assessment in marine systems is difficult because most of the time their preindustrial characteristics are not available. Four sediment cores taken in Mejillones bay (northern Chile) were used to establish preindustrial metals concentrations, and to assess the environmental status of this industrialized zone. According to historical documents, the beginning of the industrial era start in 1850 CE. Considering this, the preindustrial concentration of some metals was established, by mean of a statistical approach. Most of the metals increase their concentration from the preindustrial to the industrial period. Environmental assessment showed an enrichment of Zr and Cr, a moderately polluted condition, and a low probability of toxic effect on the biological communities. The preindustrial values derived from sediment cores are a good tool to evaluate the environmental condition of Mejillones bay. However new information (backgrounds with a higher spatial representativity, toxicological threshold, and others) it is necessary to improve the environmental assessment of this environment.

Forest fire indicators and mercury deposition in an intense land use change region in the Brazilian Amazon (Alta Floresta, MT).

Black carbon, charcoal and mercury fluxes were measured from sediment cores taken in an artificial water dam in an intense land use change area in the Alta Floresta district in the Brazilian Amazon, in order to characterize the differences in the evolution of human occupation patterns in the region during the last 18 years. A positive correlation between the black carbon and charcoal particle fluxes and the evolution of the Brazilian gross domestic production (GDP) was observed. Mercury fluxes showed a positive correlation with gold production and exhibited a distinct evolution pattern when compared to in relation to the forest fires indicators and Brazilian GDP. The fluxes of forest fires markers showed an increase in deforestation activities in the region after 1993. Mercury deposition showed a substantial decrease after 1994. The patterns of distribution in both forest fires tracers and gold mining tracers indicate substitution of the regional economic model. It also marked different antropogenic impact type in the ecosystem.