Sepetiba Bay: A Case Study of the Environmental Geochemistry of Heavy Metals in a Subtropical Coastal Lagoon

Major human civilisations have preferably developed along coastal areas, assumed as natural receptors of wastes from their activities. Tropical and sub-tropical coasts, in particular, have typically been this case, since during most of the last two centuries their colony status demanded harbour facilities and coastal commercial cities to export raw materials to their colonial capitals in Europe. Although evidence of environmental depreciation has existed for many centuries, a significant worsening of environmental conditions and natural ecosystems deterioration is only evident after the industrialisation and accelerated population growth of most ex-colonies after the first half of the last century. The environmental deterioration was so large and evident that, starting in the 1960s, increasing public pressure resulted in the creation of various environmental regulations and national and international conventions to cope with the problem. This, together with a worldwide substitution of “dirty” technologies, resulted during the past 30 years in a general decrease in pollutant emissions. Notwithstanding, the degree of contamination of many coastal areas hasn’t decreased with the same velocity and in many areas has remained the same or even increased when compared to situation during the late 1970s. This fact suggests that the properties of coastal ecosystems may result in large concentrations of pollutants even when emissions are very low and their functional processes are able to keep pollutants under permanent remobilisation. This seems most probable when dealing with tropical and sub-tropical coastal ecosystems.