Heavy Metal Contamination In The Marine Sediments Of The Cockburn Sound Region

Landfill leachates are a concern in the Pacific Region where they may contribute contaminants to the coastal marine environment. Poor waste management and pollution of coastal waters are amongst the major environmental problems in Kiribati, particularly in South Tarawa. An investigation of areas adjacent to coastal landfill sites; Betio, Kiribati and Auckland, New Zealand was undertaken. The Kiribati case study investigated metal contamination in marine sediments at an operational landfill while the New Zealand study was adjacent to a coastal landfill decommissioned in the 1970s. Surficial sediments (top 15 cm) were collected along transects. At both the New Zealand and Kiribati sites, 3 transects adjacent to the landfill and 1 control transect were sampled. The sediments were analyzed for particle size distribution, organic matter content, and Cd, As, Cr, Cu, Pb, Hg, Ni and Zn concentrations. The pH was also measured. The study produces some new information for Kiribati where these types of measurements have not previously been undertaken and also provides a clear and comprehensive literature review on the topic

The present survey was designed to assess the degree of contamination of sediments in Table Bay harbour, Cape Town, and to identify the sources of the contaminants. The information will also be used to determine the quantities of heavy metals and hydrocarbons that are dumped in Table Bay as a result of maintenance dredging operation in the harbour.

Metals are naturally present in our environment and trace amounts of metals are essential micronutrients for the growth of many marine organisms. However, excessive amounts of heavy metal can be toxic to marine life. In this book, the authors gather topical research from around the globe in the study of heavy metal sediments. Topics discussed in this compilation include the distribution of heavy metals and total petroleum hydrocarbons in soils near a petrochemical complex in China; heavy metals in coastal sea sediments of the eastern Adriatic Sea; environmental assessments of metal concentrations in select rivers, estuaries and coastal sediments; iron contamination in the Bizerte Lagoon of Tunisia and the correlation between millennial mining activities and heavy metal pollution in Spanish estuaries.

Management of sediments from coastal areas, contaminated with heavy metals and organic substances, is a very critical issue. Management decisions are usually based on total pollutant concentrations and various guidelines that are used by different countries. Heavy metals can be mobilized from polluted sediments if they are exposed to changing environmental conditions that occur during excavation, disposal at sea, or disposal in confined facilities. This paper examines the changes in heavy metals partitioning to binding phases in contaminated marine sediments and the release of metals to the environment. Environmental conditions are simulated by submitting sediments to a modified elutriation test with oxygenated and deoxygenated seawater. A sequential extraction procedure is used to determine the binding fractions of heavy metals in the sediments. Fractionation analysis of excavated marine sediments from the port of Piraeus, Greece showed that copper is primarily associated with organic matter, whereas lead and zinc are primarily associated with iron oxides. Under anoxic conditions, the metals bound to the various binding fractions remain practically stable. On the other hand, under oxic conditions, an increase in the concentration of metals associated with carbonates and a decrease in the concentration of metals associated with organic matter and iron oxides were observed. Both under oxic and anoxic conditions, actual metal mobility was very low and less than 0.5 % of total metal mass was found in the dissolved phase.

The aim of this volume is to draw together state-of-the-art reviews of knowledge onlevels of heavy metals in marine environments (particularly in marine animals), the dynamicprocesses in these systems, toxic effects, and threats presented by heavy metals in foods ofmarine origin.All heavy metals, whether biologically essential or not, have the potential to be toxicto organisms at a threshold bioavailability. Such threshold concentrations vary betweenmetals, between species and with the physicochemical characteristics of the medium, somelike copper being particularly toxic even though essential in trace amounts. Responses ofanimals to metals in their medium or food depend to a large extent on the ability of speciesto regulate levels attained in their tissues. Higher animals have the capacity to regulate levelsof many metals, while marine invertebrates can regulate some within certain limits. Whereanimals cannot regulate physiological levels of metals, an alternative strategy is to detoxifyand store metals in relatively harmless forms. Knowledge of the manner in which animals deal with potentially toxic concentrations of heavy metals is of fundamental importance in the assessment of metal pollution by analysis of metal levels in biological samples. The interaction of heavy metals with biological materials is a key theme running through this volume. Toxic effects may be reflected at the individual, population, or ecosystem level, affecting species composition and production levels, or may be of direct dietary significance to man. The global cycling of metals through the marine environment is crucially affected by biological processes.