Neutron activation analysis of atmospheric aerosols from a small Pacific Island country: a case study of Suva, Fiji Islands

A systematic study was developed to investigate the quality of air in Suva, the capital city of Fiji Islands. This is the first work of its kind in the South Pacific Islands and was aimed at characterizing the elemental abundances in total suspended particulate (TSP) matter in Suva 19s air. Aerosol samples were collected from 11 locations in Suva during the period 2000 132003 using a high-volume sampler. Concentrations of some heavy metals and other trace elements in these atmospheric aerosols were investigated by neutron activation analysis and gamma spectrometry. Concentrations of total suspended particulates for residential, traffic and industrial areas were found to be in the range 9-43, 20-58 and 33-91 ;Cg/m3, respectively. The elements sodium, iron and zinc have been observed in relatively higher concentrations than other elements. Moreover, calculated enrichment factors for some elements (such as arsenic, bromine, cobalt, chromium and antimony) reveal possible anthropogenic inputs into air mainly through automobile exhaust emissions

Concentrations of 7Be in surface air at Suva, Fiji

A high-volume air sampler and a high-resolution gamma-ray spectrometer have been used during the period 1999-2000 at the University of the South Pacific to measure the activity of 7Be in the surface air at Suva, the capital city of Fiji. The measurements indicate that the average concentration of 7Be in surface air is about 1.6 mBq m-3, which agrees closely with the corresponding values reported for other Pacific islands in the region. 7Be shows a significant correlation with nitrate in the atmosphere. This could imply long-range transport of anthropogenically-derived continental material to Fiji or the intrusion of nitrogen species from the stratosphere to surface air

Sediment deposition rate in the Falefa river basin, Upolu Island, Samoa

The 137Cs method was employed to investigate the recent historical rate of sediment deposition on a lowland alluvial floodplain in the Falefa River basin, Upolu Island, Samoa. Caesium stratigraphy in the floodplain sediment profile was clearly defined, with a broad peak at 145–175 cm depth. The measured rate of vertical accretion over the last 40 years is 4.0 ± 0.4 cm per year. This rate exceeds observations in humid environments elsewhere, but is similar to that recorded on other tropical Pacific Islands. Available flow data for the Vaisigano River in Samoa give a ‘near-catastrophic’ index value of 0.6 for flood variability. This is associated with the occurrence of tropical cyclones and storms in the Samoa area. Large floods therefore probably contribute to the high rate of floodplain sedimentation on Upolu Island. A small but growing body of evidence suggests that fluvial sedimentation rates on tropical Pacific islands are some of the highest in the world

Assessing the utility of 210Pb geochronology for estimating sediment accumulation rates on river floodplains in Fiji

Low-energy gamma ray spectroscopy has been employed to estimate floodplain sedimentation rates using measurements of 210Pb in floodplain alluvium. The utility of the technique is assessed through the analysis of excess (unsupported) 210Pb profiles in three sediment cores taken from the floodplain of the Labasa River on Vanua Levu in northern Fiji. A low-energy germanium spectrometer (LEGe) was used for the nondestructive determination of excess 210Pb in a region cultivated intensively with sugarcane. Measured average historical (c. 25 years) vertical accretion rates are between 2.2 and 4.4 cm yr−1. The findings are broadly comparable with published sedimentation rates from analyses of radionuclide profiles elsewhere in the tropical South Pacific Islands, but the rates are higher than those measured previously at the same Labasa River sites using 137Cs profiles. Accelerated soil erosion owing to cane burning and land tillage seems to be largely responsible for sediment production, although flood-related effects such as channel accretion by coarse bedload and the emplacement of large organic debris also influence floodplain sedimentation. However, application of the 210Pb technique in Fiji (and perhaps neighbouring island countries) is found to have serious drawbacks compared to the more robust 137Cs method, owing principally to the low 210Pb concentrations in the sandy alluvial sediment tested