Prevalence and distribution of fecal indicator organisms in South Florida beach sand and preliminary assessment of health effects associated with beach sand exposure

Fecal indicator levels in nearshore waters of South Florida are routinely monitored to assess microbial contamination at recreational beaches. However, samples of sand from the surf zone and upper beach are not monitored which is surprising since sand may accumulate and harbor fecal-derived organisms. This study examined the prevalence of fecal indicator organisms in tidally-affected beach sand and in upper beach sand and compared these counts to levels in the water. Since indicator organisms were statistically elevated in sand relative to water, the study also considered the potential health risks associated with beach use and exposure to sand. Fecal coliforms, Escherichia coli, enterococci, somatic coliphages, and F(+)-specific coliphages were enumerated from sand and water at three South Florida beaches (Ft. Lauderdale Beach, Hollywood Beach, and Hobie Beach) over a 2-year period. Bacteria were consistently more concentrated in 100g samples of beach sand (2-23 fold in wet sand and 30-460 fold in dry sand) compared to 100ml samples of water. Somatic coliphages were commonly recovered from both sand and water while F(+)-specific coliphages were less commonly detected. Seeding experiments revealed that a single specimen of gull feces significantly influenced enterococci levels in some 3.1m(2) of beach sand. Examination of beach sand on a micro-spatial scale demonstrated that the variation in enterococci density over short distances was considerable. Results of multiple linear regression analysis showed that the physical and chemical parameters monitored in this study could only minimally account for the variation observed in indicator densities. A pilot epidemiological study was conducted to examine whether the length of exposure to beach water and sand could be correlated with health risk. Logistic regression analysis results provided preliminary evidence that time spent in the wet sand and time spent in the water were associated with a dose-dependent increase in gastrointestinal illness.     

Precipitation of heavy metals in produced water: influence on contaminant transport and toxicity

Produced water undergoes changes in its physical chemistry including precipitation of heavy metals after being discharged and mixed with ambient seawater. Potential impacts of the precipitation of heavy metals on their transport and toxicity were studied using samples from offshore oil production sites on the Scotian Shelf off eastern Canada. Concentrations of aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, nickel and zinc were measured in total, particulate and dissolved fractions together with Microtox tests for assessment of toxicity. Heavy metals in produced water were transformed from dissolved to particulate phase in a period of hours under oxygenated conditions, and aggregated to larger particles that settle rapidly (>100 m/day) over a few days. In addition, there was production of buoyant particles comprised of heavy metal precipitates sequestered onto oil droplets that were transported to the surface. The particulate fraction was generally more toxic than the dissolved fraction. This was evident at the mixing interface between produced water and seawater where elevated particulate and toxicity levels were observed. Laboratory studies suggest an increase in the toxicity of discharged produced water over time. Time-series experiments showed a sustained toxic response for more than a week following the oxidation of freshly discharged produced water that initially elicited little or no toxic response in the Microtox test. Chemical processes identified in this study, namely precipitation of heavy metals and consequent settling and rising fluxes of particles, will influence the toxicity, the fate and the transport of potential contaminants in the produced water. Therefore, these processes need to be considered in assessment of the environmental impact associated with offshore oil and gas operations.     

Study of mango biomass (Mangifera indica L) as a cationic biosorbent

Unfertilizable fruiting buds of mango plant Mangifera Indica L, an agrowaste, is used as a biomass in this study. The efficacy of the biosorbent was tested for the removal of lead, copper, zinc and nickel metal ions using batch experiments in single and binary metal solution under controlled experimental conditions. It is found that metal sorption increases when the equilibrium metal concentration rises. At highest experimental solution concentration used (150 mg/L), the removal of metal ions were 82.76 % for lead, 76.60 % for copper, 63.35 % for zinc and 59.35 % for nickel while at lowest experimental solution concentration (25 mg/L), the removal of metal ions were 92.00% for lead, 86.84 % for copper, 83.96 % for zinc and 82.29 % for nickel. Biosorption equilibrium isotherms were plotted for metal uptake capacity (q) against residual metal concentrations (C_f) in solution. The q versus C_f sorption isotherm relationship was mathematically expressed by Langmuir and Freundlich models. The values of separation factor were between zero and one indicating favourable sorption for four tested metals on the biosorbent. The surface coverage values were approaching unity with increasing solution concentration indicating effectiveness of biosorbent under investigation. The non-living biomass of Mangifera indica L present comparable biosorption capacity for lead, copper, zinc and nickel metal ions with other types of biosorbent materials found in literature and is effective to remove metal ions from single metal solutions as well as in the presence of other co-ions with the main metal of solution.     

A new pathway for Deep water exchange between the Natal Valley and Mozambique Basin?

Although global thermohaline circulation pathways are fairly well known, the same cannot be said for local circulation pathways. Within the southwest Indian Ocean specifically there is little consensus regarding the finer point of thermohaline circulation. We present recently collected multibeam bathymetry and PARASOUND data from the northern Natal Valley and Mozambique Ridge, southwest Indian Ocean. These data show the Ariel Graben, a prominent feature in this region, creates a deep saddle across the Mozambique Ridge at ca. 28°S connecting the northern Natal Valley with the Mozambique Basin. Results show a west to east change in bathymetric and echo character across the northern flank of the Ariel Graben. Whereby eroded plastered sediment drifts in the west give way to aggrading plastered sediment drift in the midgraben, terminating in a field of seafloor undulations in the east. In contrast, the southern flank of the Ariel Graben exhibits an overall rugged character with sediments ponding in bathymetric depressions in between rugged sub/outcrop. It is postulated that this change in sea-floor character is the manifestation of deep water flow through the Ariel Graben. Current flow stripping, due to increased curvature of the graben axis, results in preferential deposition of suspended load in an area of limited accommodation space consequently developing an over-steepened plastered drift. These deposited sediments overcome the necessary shear stresses, resulting in soft sediment deformation in the form of down-slope growth faulting (creep) and generation of undulating sea-floor morphology. Contrary to previous views, our works suggests that water flows from west to east across the Mozambique Ridge via the Ariel Graben.     

An evaluation of the relative importance of the effects of climate change and groundwater extraction on seawater intrusion in coastal aquifers in Atlantic Canada

To investigate the relative importance of projected sea-level rise, climate change effects on recharge, and groundwater extraction on seawater intrusion in important coastal aquifers in Atlantic Canada, a three-dimensional numerical model of density-dependent groundwater flow coupled with solute transport was developed for the Richibucto region of New Brunswick. The model was used, with an efficient 2^k factorial design approach, to perform simulations for the period 2011–2100. The results of the factorial analyses indicate that the relative importance of the three factors investigated varies depending on the model location considered. The effect of declining recharge is most significant at shallow to intermediate depths along the freshwater–seawater transition zone, while the effect of increasing pumping rates dominates at a location relatively close to the well field. The effect of sea-level rise is shown to be significant only at the much deeper inland toe of the transition zone. The spatial variation in importance is related to how different model boundary conditions influence freshwater flow at the different locations within the model domain. This investigation indicates that sea-level rise has the least significant effect (of the three factors considered) on future seawater intrusion in sandstone aquifers in the Richibucto region.     

Europrobe seismic reflection profiling across the eastern Middle Urals and West Siberian Basin

New deep seismic reflection data provide images of the crust and uppermost mantle underlying the eastern Middle Urals and adjacent West Siberian Basin. Distinct truncations of reflections delineate the late-orogenic strike-slip Sisert Fault extending vertically to ∼28 km depth, and two gently E-dipping reflection zones, traceable to 15–18 km depth, probably represent normal faults associated with the opening of the West Siberian Basin. A possible remnant Palaeozoic subduction zone in the lower crust under the West Siberian Basin is visible as a gently SW-dipping zone of pronounced reflectivity truncated by the Moho. Continuity of shallow to intermediate-depth reflections suggest that Palaeozoic accreted island-arc terranes and overlying molasse sequences exposed in the hinterland of the Urals form the basement for Triassic and younger deposits in the West Siberian Basin. A highly reflective lower crust overlies a transparent mantle at about 43 km depth along the entire 100 km long seismic reflection section, suggesting that the lower crust and Moho below the eastern Middle Urals and West Siberian Basin have the same origin.     

Late Quaternary tephra layers around Raoul and Macauley Islands,Kermadec Arc: implications for volcanic sources,explosive volcanism and tephrochronology

A suite of deep‐sea cores were collected along transects up to 100 km across the fore‐arc and back‐arc regions of the predominantly submarine Kermadec arc near Raoul and Macauley islands, southwest Pacific. The cores reveal a macroscopic tephra record extending back >50 ka. This is a significant addition to the dated record of volcanism, previously restricted to fragmented late Holocene records exposed on the two islands. The 27 macroscopic tephra layers display a wide compositional diversity in glass (～50–78 wt% SiO₂). Many tephra layers comprise silicic shards with a subordinate mafic shard population. This could arise from magma mingling and may reflect mafic triggering of the silicic eruptions. Broadly, the glass compositions can be distinguished on diverging high‐K and low‐K trends, most likely arising from different source volcanoes. This distinction is also reflected in the tephra records exposed on Raoul (low‐K) and Macauley (high‐K) islands, the likely source areas. Heterogeneous tephra comprising shards of both high‐ and low‐K affinity, silicic and mafic compositions, and more homogeneous tephra with subordinate outlier shard compositions, are best explained by post‐depositional mixing of separate eruption deposits or contemporaneous eruptions. Evidently, the slow sedimentation rates of the calcareous oozes (～10¹–10² mm ka^?1) were insufficient to adequately separate and preserve closely spaced eruption deposits. This exemplifies the difficulty in assessing eruption frequencies and magmatic trends, and erecting a tephrostratigraphy, using geochemical fingerprinting in such environments. Despite these difficulties, the ca. 5.7 ka Sandy Bay Tephra erupted from Macauley Island can be correlated over a distance of >100 km, extending east and west of the island, showing that the mostly submerged volcanoes are capable of wide tephra dispersal. Hence there is potential for developing chronostratigraphies for the southwest Pacific beyond the region covered by the extensive rhyolite marker beds from the Taupo Volcanic Zone. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermal history of the Hodgkinson Province and Laura Basin,Queensland: Multiple cooling episodes identified from apatite fission track analysis and vitrinite reflectance data

Apatite fission track analysis and vitrinite reflectance data from outcrop and well samples in the Hodgkinson Province and Laura Basin reveal regional Cretaceous cooling. Apatite fission track analysis appears to define two discrete cooling episodes, in the mid‐Cretaceous (110–100 Ma) and Late Cretaceous (80–70 Ma), although in most samples data allow only definition of a single episode. Rocks now at outcrop cooled from Cretaceous palaeotemperatures generally between 50 and 130°C in the south of the region, and from >100°C in the north. Some samples from the Hodgkinson Province also show evidence for an Early Jurassic cooling episode, characterised by maximum palaeotemperatures varying from at least 95°C (from apatite fission track analysis) to ～200–220°C (from vitrinite reflectance), with cooling beginning at around 200 Ma. Apatite fission track analysis data do not reveal the earlier event in the Laura Basin, but on the basis of vitrinite reflectance data from Permian? units this event is also inferred to have affected the pre‐Jurassic basin units in this region. The regional extent of the Cretaceous cooling episode in the Hodgkinson Province suggests that the elevated palaeotemperatures in this region were most likely due to greater depth of burial, with subsequent cooling due to kilometre‐scale denudation. For a palaeogeothermal gradient of 30°C/km and a palaeosurface temperature of 25°C the total degree of Cretaceous cooling experienced by the samples corresponds to removal of between ～0.8 and >3.0 km of Triassic and younger section removed by denudation, beginning some time between ca 110 and 80 Ma. Higher palaeogradients would require correspondingly lower amounts of removed section. The geology of the Laura Basin suggests that an explanation of the observed Cretaceous palaeotemperatures in this region in terms of deeper burial may be untenable. Heating due to hot fluid flow may be a more realistic mechanism for producing the observed Cretaceous palaeothermal effects in the Laura Basin.     

Composition of jovian dust stream particles

The Cassini spacecraft encountered Jupiter in late 2000. Within more than 1 AU of the gas giant the Cosmic Dust Analyser onboard the spacecraft recorded the first ever mass spectra of jovian stream particles. To determine the chemical composition of particles, a comprehensive statistical analysis of the dataset was performed. Our results imply that the vast majority (>95%) of the observed stream particles originate from the volcanic active jovian satellite Io from where they are sprinkled out far into the Solar System. Sodium chloride (NaCl) was identified as the major particle constituent, accompanied by sulphurous as well as potassium bearing components. This is in contrast to observations of gas in the ionian atmosphere, its co-rotating plasma torus, and the neutral cloud, where sulphur species are dominant while alkali and chlorine species are only minor components. Io has the largest active volcanoes of the Solar System with plumes reaching heights of more than 400 km above the moons surface. Our in situ measurements indicate that alkaline salt condensation of volcanic gases inside those plumes could be the dominant formation process for particles reaching the ionian exosphere.