Lake Naivasha is unique in the chain of East African Rift Valley lakes in being the only freshwater ecosystem in an otherwise soda/saline lake series. Catchment rivers have never previously been surveyed. Valley topography, precipitation patterns and geology create a diversity of river systems draining into Lake Naivasha. Semi-quantitative assessment using the River Habitat Survey technique demonstrates a diversity of habitats and erosion/sedimentation patterns, reflecting the tectonic origin of the area. The survey descriptions form a basis for identification of areas where efforts will need to be directed for physical and biological protection.
Pollutants deposited on the Severn Estuary from the atmosphere derive mainly from local industrial and urban centres. Atmospheric deposition accounts for 50% of the lead and zinc inputs, I0-20"/, of the cadmium, copper and nickel to the Estuary, but only a small proportion of the chromium, iron and manganese. Most of the cadmium, copper and lead comes from the lower atmosphere near Avonmouth and Cardiff Bay. Westerly winds have much higher sodium and chloride concentrations but generally carry lower pollution loads than the less frequent, offshore easterlies. Strong winds recycle pollutants into the atmosphere via sea spray. The hills on both sides of the Estuary encourage deep vertical mixing, and effluents may be carried well inland. Stable atmospheres, associated with southerly and easterly airflows, cause trapping and entrainment of stack emissions. Thus easterlies may deposit much higher levels of pollutants. This paper reviews present knowledge regarding the deposition of metals from the atmosphere into the waters of the Severn Estuary. Preliminary results (1989) indicate that, while distribution patterns remain broadly similar, the quantities deposited were considerably less than they were six years previously.ADDITIONAL KEY WORDS:-Air pollutionheavy metalsdeposition.
CONTENTS
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.