Determination of iodine content in Fijian foods using spectrophotometric kinetic method

The spectrophotometric kinetic method was validated for the determination of iodine in different food samples. The method is based on the iodide catalysed reduction of Ce4+ to Ce3+ by As3+. The absorbance of the kinetic indicator reaction was measured at 370 nm for exactly 1 min at 37 °C. The change in absorbance per min, as a measure of initial rate, was plotted against the different iodine concentrations to achieve a linear calibration equation with the R2 value of 0.9998 which showed excellent reproducibility. The limit of detection (LOD) was 1.54 ng/mL and the limit of quantification (LOQ) was 4.90 ng/mL. The incineration of the food organic matter was achieved by ashing the food samples at 600 °C using KOH and ZnSO4 in steps for 3 h. Trace levels of iodine (ng) were determined successfully using the validated spectrophotometric kinetic method for the 9 food samples (36 sub-samples). The Fiji seaweeds, lumiwawa (brown seaweed) showed the highest iodine content being 6373.30 ± 0.39 ng/g followed by sea grapes (green seaweed) 1162.81 ± 0.61 ng/g, lettuce 114.81 ± 0.08 ng/g, English cabbage 108.40 ± 0.06 ng/g, Chinese cabbage 104.01 ± 0.06 ng/g, pumpkin 101.24 ± 0.08 ng/g, long bean 97.61 ± 0.10 ng/g, banana 76.18 ± 0.10 ng/g and tomato 40.32 ± 0.04 ng/g. The coefficient of variation for the sample analysis was <5.31% with a mean and standard deviation of 2.55 ± 0.17% for the food samples analysed. The recovery analysis of iodine from standard samples ranged from 99.84 ± 0.91% to 100.24 ± 5.92% with an excellent average recovery of 100.06 ± 3.16%. The analytical coefficient of variation was calculated to be 0.34% for the food samples analysed. This shows exceptional system analytical stability of the method used in this study

A study on tributyl tin (TBT) contamination of marine sediments in the major ports of Fiji

Tri-n-butyltin (TBT) compounds are synthetic, multipurpose chemicals, which have been extensively used, in marine antifouling paints. They have been known to be extremely poisonous to mollusc fishery resources (oysters, clams, scallops, etc.). TBT levels in marine sediments from the main ports in Fiji were analysed using the GC/FPD method. The results indicated that these sites were among the worst polluted with TBT in the world. The most contaminated site recorded a TBT concentration of 360μgg-1. TBT comprised 48-90% of the total organotins measured. Some stringent legislative means are needed to regulate the use of this contaminant in marine anti-fouling paints

Sewage sludge heavy metal analysis and agricultural prospects for Fiji

Insoluble residues produced in Waste Water Treatment Plants (WWTP) as by products are known as sewage sludge (SS). Land application of SS, particularly in agricultural lands, is becoming an alternative disposal method in Fiji. However, currently there is no legislative framework governing its use. SS together with its high nutrient and organic matter contents, constitutes some undesired pollutants such as heavy metals, which may limit its extensive use. The focus of this study therefore was to determine the total concentrations of Pb, Zn, Cd, Cu, Cr, Ni and Mn in the SS produced at the Kinoya WWTP (Fiji) and in the non-fertile soil amended with the SS at 20, 40, 60, 80% application rates and in the control (100% Soil). The bioavailable heavy metals were also determined as it depicts the true extent of metal contamination. The treatment mixtures were then used to cultivate cabbage plants in which the total heavy metal uptake was investigated. Total Zn (695.6 mg/kg) was present in the highest amounts in the 100% SS (control), followed by Pb (370.9 mg/kg), Mn (35.0 mg/kg), Cu (65.5 mg/kg), Cr (20.5 mg/kg) and finally Cd (13.5 mg/kg) and hence a similar trend was seen in all treatment mixtures. The potential mobility of sludgeborne heavy metals can be classified as Ni > Cu > Cd > Zn > Mn > Cr > Pb. Total metal uptake in plant leaves and stems showed only the bioavailable metals Cu, Cd, Zn and Mn, with maximum uptake occurring in the leaves. Ni, despite being highly mobile was not detected, due to minute concentrations in the SS treatments. Optimum growth occurred in the 20 and 40% SS treatments. However maximum Cu and Mn uptake occurred in the 40% SS treatment thereby making the 20% treatment the most feasible. Furthermore the total and bioavailable metal concentrations observed were within the safe and permitted limits of the EEC and USEPA legislations

Landfill gas generation and methane recovery at Naboro landfill, Fiji Islands: a case study from a developing Pacific Island country

The Naboro landfill in Suva, the capital city of Fiji Islands, is a sanitary engineered landfill, consisting of a compacted clay protective liner and leachate collection system. The waste is selectively placed, compacted and then covered with soil. The landfill was commisioned in 2005 and is currently receiving an average of 70,000 tonnes of waste annually. The municipal solid waste deposited in the landfill undergoes anaerobic decomposition and the methane gas generated escapes into the atmosphere, adding to the national greenhouse gas inventory. Currently there are no methane recovery and biogas utilisation technology in place or methane flaring at the Naboro landfill site. A feasibility study was carried out recently and based on the model output and field experiments, it was noted that methane recovery and utilisation could be a viable option although there could be some challenges associated with it. According to the waste chaacterization data supplied by the landfill operator it was noted that 83% is house hold waste, 11% is garden waste and 5% is food waste and 1% construction and demolition waste. Based on the type of waste deposited and the tropical weather condition it was calculated using the model that approximately 800 m3/h of methane is generated in 2016. Figure below shows the landfill gas generated at the Naboro landfill from stage 1 to stage 4. Due to tropical humid weather condition and waste rich is organic waste that decomposes rapidly results in the yearly average emission of 74% of total methane generated despite methane recovery via vertical wells installed at the end of each stage. The emission equates to 47,000 tons of CO2 equivalent per year despite methane recovery. The emission can be reduced if the methane generated could be extracted using vertical recovery wells half way through each stage rather than at the end of each stage and as a consequence a slight decrease in yearly average emissions of 41,000 tons of CO2 equivalent were noted. Another approach is to lay horizontal wells as the waste is compacted in the active cell and this could increase the efficiency of landfill gas extraction. The model result indicate that the use of horizontal wells reduces the yearly average emission to 55% of total methane generated. This highlights the fact that approximately 45 % of the methane generated could be harnessed and could be utilized to generate energy using gas engines. However a large fraction of the methane generated is still lost as emission to the atmopshere and this can be further reduced by enhancing the oxdising capacity of the soil cover. The methane oxidation in cover soil was measured to be 10.3% by measuring the CH4-CO2 ratios in the static chamber measurements. The experimental value is close to the IPCC default value of 10%. The paper will discuss other challenges associated with methane recovery at Naboro landfill particularly with landfill gas management

Ozone in the Pacific tropical troposphere from ozonesonde observations

Ozone vertical profile measurements obtained from ozonesondes flown at Fiji, Samoa, Tahiti, and the Galapagos are used to characterize ozone in the troposphere over the tropical Pacific. There is a significant seasonal variation at each of these sites. At sites in both the eastern and western Pacific, ozone mixing ratios are greatest at almost all levels in the troposphere during the September‐November season and smallest during March‐May. The vertical profile has a relative maximum at all of the sites in the midtroposphere throughout the year (the largest amounts are usually found near the tropopause). This maximum is particularly pronounced during the September‐November season. On average, throughout the troposphere, the Galapagos has larger ozone amounts than the western Pacific sites. A trajectory climatology is used to identify the major flow regimes that are associated with the characteristic ozone behavior at various altitudes and seasons. The enhanced ozone seen in the midtroposphere during September‐November is associated with flow from the continents. In the western Pacific this flow is usually from southern Africa (although 10‐day trajectories do not always reach the continent) but also may come from Australia and Indonesia. In the Galapagos the ozone peak in the midtroposphere is seen in flow from the South American continent and particularly from northern Brazil. High ozone concentrations within potential source regions and flow characteristics associated with the ozone mixing ratio peaks seen in both the western and eastern Pacific suggest that these enhanced ozone mixing ratios result from biomass burning. In the upper troposphere, low ozone amounts are seen with flow that originates in the convective western Pacific

Heavy metal pollution in Suva harbour sediments, Fiji

In Fiji, contamination of the coastal environment by heavy metals is proving to be a real concern. This work reports for the first time analyses carried out on an extensive basis, to ascertain the extent of anthropogenic contamination by heavy metals in the <0.063 mm surface sediments of Suva harbour. Sediment samples from 40 sites selected within the harbour were collected and analysed for five heavy metals. The levels of the metals range from 21.4 to 143.0 ± 0.1 mg/kg Cu, 1.40 to 4.87 ± 0.07 wt.% Fe, 22.1 to 93.5 ± 0.3 mg/kg Pb, 40.2 to 269.0 ± 0.3 mg/kg Zn and 1.1 to 2.6 ± 0.2 mg/kg Sn. With reference to the pristine area of the Great Astrolabe, in Kadavu, the acquired data from the harbour are indicative of heavy metal pollution. This could be attributed to the numerous industrial and commercial activities at Wailada and Walu Bay industrial areas, the municipal dump located at the Suva foreshore and the Suva wharf. The pollution is further compounded by the high population density in Suva city