Philomena Gangaiya

Trace Element Studies in Laucala Bay, Suva, Fiji

The trace metal distribution in the sediments of Laucala Bay, a coastal lagoon with a barrier reef and significant freshwater input, adjacent to Suva, the capital of Fiji (150,000 people), was studied from the point of view of assessing the significance of anthropogenic sources relative to natural ones. Surface sediments from 25 sites in the Bay were analysed for particle size distribution, organic carbon and major (Si, Al, Fe, Ca, Mg) and trace metal (Mn, Zn, Cu, Pb, Cd, Hg) contents. Suspended sediments from one site and shellfish samples from five sites were also analysed. The sediments were found to be mostly of terrigenous origin. Particle size distribution, organic carbon and major elemental composition of the sediments were generally related to location within the Bay. A significant natural source of trace metals in the sediments is the suspended solids transported into the Bay by rivers. The spatial distribution of trace metals could not be fully explained by the particle size distribution and mineral composition of the sediments. Contributions from anthropogenic sources were also suspected, but the degree of enrichment from such sources is not great at the present time.

Heavy metal contamination of the Lami coastal environment, Fiji

Contamination of the coastal environment of small island countries is of concern because peoples livelihoods in these countries are intimately linked to the resources of the coastal zone. The Lami estuary in Fiji is located downstream of an industrial area and is used extensively for fishing and other recreational activities. Sediment samples from twenty-nine sites within the area were analysed for copper, lead and zinc to determine whether the area is contaminated with heavy metals. Within the estuary, significant enrichment is evident, with heavy metal concentrations exceeding some of those from other known contaminated sites in the country. Although copper contamination appears to be restricted to a few sites within the estuary, contamination with lead and zinc seems to be spreading to areas further away from the shore. Metal distribution patterns clearly indicate adjacent factories to be the main source of contamination. The results show that contrary to popular belief, highly contaminated sites do exist in the relatively pristine coastal environments of island countries like Fiji.

Enteromorpha flexuosa (Wulfen) J. Agardh (Chlorophyta: Ulvales) – Evaluation as an Indicator of Heavy Metal Contamination in a Tropical Estuary

The use of bioindicators for contaminant monitoring ispopular in all sectors of the environment but quite oftenbioindicators are utilised without rigorous evaluation oftheir viability as an indicator. We report field andlaboratory investigations into the value of a commonlyfound macroalga, Enteromorpha flexuosa (Wulfen) J.Agardh (Chlorophyta: Ulvales) as an indicator of copper,zinc and lead contamination in a tropical estuary inFiji. In the laboratory, metal content of E.flexuosa after 60 days of growth in seawater containingincreasing concentrations of the metals showed almostperfect correlation with metal concentrations in waterfor all three metals, and concentration factors obtainedwere generally higher than values reported for otherspecies of Enteromorpha. Performance in the fieldwas evaluated by a one-year monitoring of metals in E. flexuosa, water and sediments from a contaminatedestuary. Metal concentrations in water were always belowdetection limits and field concentration factors couldnot be determined but the concentration of lead in E. flexuosa showed a high correlation with the leadcontent of sediments. Lack of such correlation forcopper and zinc in the field suggests that otherenvironmental factors besides metal load in the physicalenvironment could be controlling the bioaccumulation ofthese two metals. Whilst demonstrating E. flexuosato be a viable bioindicator for lead, these results alsohighlight the need for proper assessment before anorganism is considered for environmental monitoring.

The potassium status of some Pacific Island soils

Abstract The potassium (K) status of 22 soil samples from 12 pedons originating in 6 Pacific Island countries has been investigated by several techniques. The total K contents of the soils studied were found to be low to very low. Use of various methods available for measuring exchangeable cations in soils showed exchangeable K to be dependent on factors such as ionic strength and displacement cation of the extracting solution. The proportions of non‐exchangeable K that are plant available were found to be very low for most soils. Data obtained from quantity/intensity measurements suggest that the soils would be responsive to added K.

A review of the problems associated with applying the terms surface charge and zero point of charge to soils

Abstract Many soil properties are determined by the surface charge on the soil particles. A range of methods for determining the surface charge properties is available from the literature. However, the interpretation of the results obtained and the theoretical basis of some of the methods is confusing with different terms having different meanings for different authors. Thus, the study of surface charge properties and the theoretical basis is particularly difficult for a newcomer to the field. This paper presents a review of the major concepts as used in the current literature and highlights the problems encountered when applying these concepts to the determination of the surface charge properties.

A simple non‐atomic absorption procedure for determining the effective cation exchange capacity of tropical soils

Abstract A simple non‐atomic absorption procedure for determining the effective cation exchange capacity of tropical soils has been developed. The method involves the shaking of soil samples (10g) with ammonium chloride (3 x 25 cm3, 1 mol/L) to displace the exchangeable cations. The soil is then equilibrated with dilute ammonium chloride (3 x 25 cm3, 0.01 mol/L). After the final equilibration the ammonium ions retained by the soil are determined to facilitate the calculation of the ECEC. Data obtained for 22 tropical soils ranging in ECEC values from 1–50 cmol(+)/kg show a highly significant correlation with values derived using the compulsive exchange or summation procedures. The silver thiourea procedure data gave significantly poorer correlations with that obtained using all three of the above methods.

First screening study of metal content in soil from a mixed waste receptacle

We report the first screening study for the metals copper, zinc, lead, nickel and cadmium in the Lami municipal disposal facility, in Suva, Fiji where virtually uncontrolled dumping has been carried out for over fifty years. Soil from three parts of the facility having had different degrees of usage was analysed for a range of heavy metals, and evaluated according to international guidelines. The results show copper (100–220 mg kg–1), lead (200–500 mg kg–1) and zinc (220–350 mg kg–1) concentrations exceeded commonly used eco-toxicity threshold values (copper, 160 mg kg–1; lead, 210 mg kg–1; and zinc, 220 mg kg–1). Moreover, there were indications that considerable leaching may have been occurring for long periods of time at the site. Overall, this study shows that even in areas with little industrialization, lack of adequate waste management controls can result in unusually high levels of contamination. The results raise concerns about the wellbeing of the communities living adjacent to the facility that depend on the adjacent marine environment for subsistence.