Roshan T Ramessur

Isotopic, geophysical and biogeochemical investigation of submarine groundwater discharge: IAEA-UNESCO intercomparison exercise at Mauritius Island

Submarine groundwater discharge (SGD) into a shallow lagoon on the west coast of Mauritius Island (Flic-en-Flac) was investigated using radioactive ((3)H, (222)Rn, (223)Ra, (224)Ra, (226)Ra, (228)Ra) and stable ((2)H, (18)O) isotopes and nutrients. SGD intercomparison exercises were carried out to validate the various approaches used to measure SGD including radium and radon measurements, seepage rate measurements using manual and automated meters, sediment bulk conductivity and salinity surveys. SGD measurements using benthic chambers placed on the floor of the Flic-en-Flac Lagoon showed discharge rates up to 500 cm/day. Large variability in SGD was observed over distances of a few meters, which were attributed to different geomorphological features. Deployments of automated seepage meters captured the spatial and temporal variability of SGD with a mean seepage rate of 10 cm/day. The stable isotopic composition of submarine waters was characterized by significant variability and heavy isotope enrichment and was used to predict the contribution of fresh terrestrially derived groundwater to SGD (range from a few % to almost 100%). The integrated SGD flux, estimated from seepage meters placed parallel to the shoreline, was 35 m(3)/m day, which was in reasonable agreement with results obtained from a hydrologic water balance calculation (26 m(3)/m day). SGD calculated from the radon inventory method using in situ radon measurements were between 5 and 56 m(3)/m per day. Low concentrations of radium isotopes observed in the lagoon water reflected the low abundance of U and Th in the basalt that makes up the island. High SGD rates contribute to high nutrients loading to the lagoon, potentially leading to eutrophication. Each of the applied methods yielded unique information about the character and magnitude of SGD. The results of the intercomparison studies have resulted a better understanding of groundwater-seawater interactions in coastal regions. Such information is an important pre-requisite for the protection and management of coastal freshwater resources.

Determination of lead, chromium and zinc in sediments from an urbanized river in Mauritius.

The mean concentration of Cr (105 +/- 30 mg kg(-1)), Zn (167 +/- 30 mg kg(-1)) and Pb (14 +/- 7 mg kg(-1)) in the sediments along St. Louis River situated in an urbanized and industrialized area in Mauritius were well below the limits of 600, 2500 and 700 mg kg(-1) quoted for contaminated sediments adopted from the draft standards (24% clay and 10% organic matter by weight) from the Netherlands [Van Veen RJ, Stortelder PBM. Research on contaminated sediments in the Netherlands. In: Wolf K, Van de Brink WJ, Colon FJ, editors. Contaminated soil. Academic Publisher, 1998. p. 1263-1275.]. Industrial contamination appeared to undergo rapid dilution in the estuary as Cr had high levels near point sources from industries, but decreased rapidly in amount in the estuary possibly because of dilution by other sediments. The significant levels of Zn in sediments from upstream to the estuary suggest that the potential sources could be from the adjacent motorway and road runoff causing significant quantities to be trapped within the St. Louis River. Pb was two folds higher in the sediments in the estuary of St. Louis River compared to upstream and downstream indicating accumulation of Pb in estuarine sediments, which could be released continuously into the lagoon. The potential sources of Pb in sediments from upstream to the estuary were from the adjacent motorway and road runoff causing significant quantities to be trapped within the St. Louis River. Pb and Zn were significantly positively correlated in the sediments along St. Louis River indicating a common source for Pb and Zn. Significant negative correlations were also found for both Pb and Zn with dissolved oxygen in summer along St. Louis River which indicated that the presence of anoxic waters influenced the trapping of Zn and Pb in the sediment phase. This study has also highlighted that a phasedown of Pb in petrol is necessary and with the introduction of unleaded petrol and vehicles equipped with catalytic converters, studies on levels of Pd and Pt to provide baseline data need to be done in the near future and integrated in environmental development schemes and effective coastal zone management of small island states.

The relationship of dissolved Pb to some dissolved trace metals (Al, Cr, Mn, and Zn) and to dissolved nitrate and phosphate in a freshwater aquatic system in Mauritius

The relationship of some dissolved trace metals (Al, Cr, Mn, Zn, and Pb) with one another and to dissolved phosphate and nitrate in a freshwater aquatic system at Flic en Flac and Grand River North West (GRNW) in Mauritius (1850 km2, 20 degrees S and 57 degrees E, Western Indian ocean) is reported following trace metal determination using inductively coupled plasma mass spectrometry (ICP-MS). Dissolved Al (<200 ng ml(-1)), Cr (<50 ng ml(-1)), Mn (<50 ng ml(-1)), Zn (< 100 ng ml(-1)), and Pb (<50 ng ml(-1)) upstream, downstream GRNW and in the marshes and rivulet at Flic en Flac were found to be below the recommended EEC maximum admissible concentrations and within the ambient drinking water quality standards in Mauritius. Dissolved Pb was significantly positively correlated to both dissolved Cr and Zn suggesting that the cycling for dissolved Pb is linked to the cycling of both dissolved Cr and Zn along GRNW. The common influential cycling of Pb and Zn was further reinforced as both dissolved Pb and Zn were significantly positively correlated to dissolved phosphate, which suggested a biological role in the cycling of Zn and Pb. The role of biological activity or adsorption to biological systems in Pb cycling along GRNW is further suggested as dissolved Pb was significantly correlated to dissolved nitrate. The apparent absence of the dissolved Al, Cr, and Mn with dissolved nitrate and phosphate could be attributed to factors such as the lower sensitivity of the GRNW to metal uptake during biological activity during the time frame considered. The cycling of dissolved Al and Mn was also not linked to the cycling of Cr, Zn, and Pb as no significant correlation was found along GRNW.

Characterization of some trace metals from the export processing zone and a coastal tourist area in Mauritius using inductively coupled plasma mass spectrometry

Abstract The concentrations of six trace metals - chromium, nickel, copper, zinc, cadmium, and lead (Cr, Ni, Cu, Zn, Cd, and Pb) were determined in the freshwater system at Flic en Flac and upstream and downstream Grand River North West (GRNW) to assess the impact of hotel and industrial activities of the Export Processing Zone (EPZ) in Mauritius during 1996–1997. The trace metals Cr and Pb exceeded the proposed revised pollution limit in either river or marsh at Flic en Flac and upstream and downstream GRNW. Cr, Zn, and Pb were significantly higher in rainwater compared to upstream GRNW values, indicating that airborne lead and zinc are significant from vehicle emissions. The concentration of Cr increased about two-fold downstream GRNW. For comparison purposes, Cr was about two-fold significantly higher downstream GRNW compared to downstream Flic en Flac, indicating the release of effluents containing chromates by the textile industries in the EPZ. The contamination of rainwater by airborne lead and zinc was significant and considered to arise from the heavy use of leaded petrol and lubricating oils containing zinc additives.

A Review of Coastal Zone Management Facing Climate Change and Natural Disasters in Mauritius

The National Climate Change Adaptation Policy (NCCAPF) enabling framework in Mauritius has been designed to address key barriers such as lack of financing options, lack of institutional framework and low levels of adaptation technology transfer and aims to integrate and mainstream climate change into core development policies, strategies and plans of Mauritius. The long term energy Strategy 2009-2025 now aims to meet 35% of the energy demand throughrenewable energy sources by the year 2025. The limits of the EEZ of Mauritius (1850 km2, 20°S, 58°E, South Western Indian Ocean, 1.3 million inhabitants) have been defined by geographical coordinates through subsequent regulations under the Maritime Zones Act 1977 as the Maritime Zones (EEZ) Regulations 1984. Flash floods in Port-Louis have become increasingly frequent with floods of March 2013, dubbed as the ‘Black Saturday’ due a death toll of 11. Swells with wave heights of about 10 m occurred on the western coast in May 2007 whereas floods were recorded on the island in March 2008 as a consequence of climatic change. The Capability Approach would ensure that social arrangements target at increasing people’s capabilities and would consider indicators that reflect the importance of assessing the quality of processes rather than simply outcomes of policies and the significance of measures to enhance the ownership and participation of local communities in the management of their natural resources under integrated coastal zone management ICZM. The overall objective should be to develop climate compatible projects for vulnerable coastal regions. The paper reviews measures to strengthen coastal zone management facing climate change and natural disasters and to further improve natural disaster risk management in Mauritius in line with climate compatible development schemes and effective integrated coastal zone management of small islands states under the DPSIR Framework.

Climate Compatible Development: Legal Implications in the Coastal Zone and Inclusive Development for Mauritius

Climate change impacts as well as coastal development affect the livelihoods of the coastal communities mainly the fishermen, agriculturalist and farmers who are highly dependent on the coastal resources to earn a living. There is at present a need to strengthen coastal zone management to cater for climate change impacts as well as to provide room for inclusive coastal development so that the main economic sector (tourism), highly dependent on coastal resources, continues to flourish but not at the cost of the livelihoods of the coastal communities. At the same time coastal resources have the characteristics of “a common good” so that property rights issues become prominent and legal implications have to be taken on board. Given the nature of the topic, the authors will deal with it from a multidisciplinary perspective, with highlights from the natural science, legal and social lenses. With facts and figures they will rely on secondary data and relevant legislations to demonstrate the importance of coastal management to foster inclusive development in the fragile economies of Small Island Development States (SIDS) with particular reference to the Mauritian case study. What shall come out of this paper shall eventually achieve public consciousness to sustainable coastal inclusive development for a better Maurice Ile Durable (MID).

Investigation of Dissolved Nutrients in Tropical Coastal Waters in Mauritius

This study investigated the concentration ratios of dissolved nitrate: phosphate in tropical coastal waters in Mauritius (1,850 km2, 20°S and 57°E, Western Indian ocean) during winter 2008 and summer 2009 arising from both surface and submarine groundwater sources. Dissolved nutrients in lagoon waters were statistically compared between winter and summer periods and between urban and rural estuaries at Grand River North West (GRNW), Albion and Flic en Flac. A low ratio of 7 was computed for dissolved [nitrate]: [phosphate] for the Flic en Flac lagoon situated in a rural area, lying in the range from 2 to 15 as usually found for coastal waters globally suggesting denitrification whereas the ratio of dissolved [nitrate]: [phosphate] in lagoon waters computed for GRNW and Albion situated in urban areas were lower and less than 2 and may be attributed to possible high phosphate input. The sources of dissolved phosphate may come from the run-off of phosphate fertilizers from sugar cane plantations and submarine groundwater discharges. This high concentration of dissolved phosphate in the freshwater system can be harmful as it can cause an algal bloom. A high concentration of dissolved phosphate was recorded in September during a flood. The mean values for dissolved nitrate were 11.8 ± 11.0 μmol/L during winter and 11.7 ± 5.0 μmol/L during summer at Flic en Flac. Dissolved nitrate levels were observed to be abnormally high which probably were due to the lagoon water being mixed with the submarine groundwater discharge in the lagoon. In addition, a strong positive correlation was observed between phosphate and nitrate (R2 = 0.74) during the period of winter 2009 to summer 2010 for all the stations at Flic en Flac.