Isotopic, trace element and nutrient characterization of coastal waters from Ubatuba inner shelf area, south-eastern Brazil

Povinec, P.; Oliveira, Joselene de; Braga, Elisabete S.; Comanducci, J.-F.; Gastaud, J.; Groening, Manfred; Levy-Palomo, I.; Morgenstern, Uwe; Top, Zafer

doi:10.1016/j.ecss.2007.07.041

Cited by 24 publications

(20 citation statements)

References 35 publications

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“…When comparing this result with our previous studies (e.g. offshore Ubatuba, Brazil (Povinec et al, 2008b)), this sample is very depleted both in δ 2 H and δ 18 O (the values for Brazil were -17.5‰…”

Section: Rain and Groundwater Samplessupporting

confidence: 76%

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

Povinec¹,

Burnett²,

Beck³

et al. 2012

Journal of Environmental Radioactivity

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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 a reasonable agreement with results obtained from 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 management of coastal freshwater resources.

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Section: Rain and Groundwater Samplessupporting

confidence: 76%

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

Povinec¹,

Burnett²,

Beck³

et al. 2012

Journal of Environmental Radioactivity

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“…Several approximations have to be made for estimation of SGD fluxes from measured 222 Rn concentrations (Burnett and Dulaiova, 2003;Burnett et al, 2008;Povinec et al, 2008). SGD rates estimated from the continuous alpha-spectrometry measurements of 222 Rn decay products had a similar pattern (Fig.…”

Section: Estimation Of Sgd Fluxesmentioning

confidence: 89%

“…An ideal SGD tracer should be highly enriched in groundwater relative to seawater, behave conservatively, and be easy measured. Deuterium and 18 O are useful conservative tracers of mixing processes at the groundwater-seawater interface, as they clearly distinguish between onshore meteoric groundwater and seawater (Povinec et al, 2008). Radium also fulfils the above mentioned conditions for a good SGD tracer.…”

Section: Introductionmentioning

confidence: 86%

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Isotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil: results of the IAEA–UNESCO SGD project

Povinec

Bokuniewicz

Burnett

et al. 2008

Journal of Environmental Radioactivity

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Results of groundwater and seawater analyses for radioactive ( 3 H, 222 Rn, 223 Ra, 224 Ra, 226 Ra, 228 Ra) and stable ( 2 H, 18 O) isotopes are presented together with in situ spatial mapping and time-series 222 Rn measurements in seawater, direct seepage measurements using manual and automated seepage meters, pore water investigations using different tracers and piezometric techniques, and geoelectric surveys probing the coast. This study represents first time that such a new complex arsenal of radioactive and non-radioactive tracer techniques and geophysical methods have been used for simultaneous submarine groundwater discharge negative correlation between the SGD rates and tidal stage. This is likely caused by sea level changes as tidal effects induce variations of hydraulic gradients. The geoelectric probing and piezometric measurements contributed to better understanding of the spatial distribution of different water masses present along the coast. The radium isotope data showed scattered distributions with offshore distance, which imply that seawater in a complex coast with many small bays and islands was influenced by local currents and groundwater/seawater mixing. This has also been confirmed by a relatively short residence time of 1-2 weeks for water within 25 km offshore, as obtained by short-lived radium isotopes. The irregular distribution of SGD seen at Ubatuba is a characteristic of fractured rock aquifers, fed by coastal groundwater and recirculated seawater with small admixtures of groundwater, which is of potential environmental concern and has implications on the management of freshwater resources in the region.

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“…2 H and 18 O are effective conservative tracers of mixing processes at the groundwater-seawater interface because clear isotopic distinctions exist between terrestrial meteoric groundwater and seawater. When combined with other isotopic tracers in the mixing zone, 2 H and 18 O serve as useful indicators of the mixing dynamics (Schiavo et al, 2007;Povinec et al, 2008b). In groundwater system studies, the water's isotopes can provide insights into the water's source, recharge areas, residence time in the aquifer, hydrologic cycles and mixing with other fluids (Gibson et al, 2005;Schiavo et al, 2009;Mandal et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

18O and 226Ra in the Minjiang River estuary, China and their hydrological implications

Liu

Guo

Gao

et al. 2016

Estuarine, Coastal and Shelf Science

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Isotopic, trace element and nutrient characterization of coastal waters from Ubatuba inner shelf area, south-eastern Brazil

Cited by 24 publications

References 35 publications

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

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

Isotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil: results of the IAEA–UNESCO SGD project

18O and 226Ra in the Minjiang River estuary, China and their hydrological implications

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