The potential for anaerobic mineralisation of hydrocarbon constituents of oily drill cuttings from the North Sea seabed

The potential for natural attenuation of hydrocarbons in oily drill cuttings from the seabed beneath a North Sea oil platform was investigated. The study focused on the anaerobic degradation of n-hexadecane, n-octacosane and naphthalene using additions of 14C-labelled analogues to drill cuttings samples and was conducted under realistic seabed conditions (except pressure) over an 11-month period. No mineralisation of naphthalene was detected over this time period and mineralisation of octacosane represented only 0.5-1.5% of the added label. In contrast, mineralisation of hexadecane was 10-49% after 11 months of incubation. Selective inhibition of key functional bacterial groups revealed the key role of both sulfate reduction and methanogenesis in the degradation process. This study demonstrates the potential for natural attenuation of at least some hydrocarbon constituents of oily drill cuttings under realistic environmental conditions and highlights the involvement of a wide functional consortium in the natural attenuation process.     

The importance of site selection in monitoring the macroinvertebrate communities of the Yarra River,Victoria

The condition of the macroinvertebrate fauna of the Yarra River deteriorates progressively downstream from the virtually pristine headwater areas, through cleared rural areas in the mid-Yarra, to urban areas in the lower sections of the Yarra. It was found during a four year study, that the physico-chemical parameters affecting the fauna varied substantially in relation to the different physical characteristics of each site. In general, it is suggested that nutrients and the riparian vegetation had greatest impact on the riffle communities, and turbidities had greatest impact on the pool communities. The physical characteristics of each site also influenced the type and degree of response in the fauna to fluctuations in flow. Full consideration should therefore be given to the type of stream habitat sampled when attempting to determine which water quality parameters have significant long-term effects on the condition of the fauna.     

Effects of along-shore wind stress and surface cooling on the formation of shelf sea fronts in a simple air-sea interaction model

This paper presents numerical simulation results from a set of control and sensitivity experiments on the effects of winter-time air-sea interaction on the variability of sea surface temperature (SST) on a two-dimensional continental shelf which is uniform in the along-shore direction and is bounded to the west by a straight coast and to the east by a prescribed Gulf Stream front. In the control experiment, the model ocean circulation is driven by a time-dependent wind forcing which is parameterically coupled to the cross-shelf SST gradient. In the sensitivity experiments, wind stress, diabatic cooling and air-sea coupling are turned on separately to estimate the individual contribution of each effect to the cross-shelf SST variation. Experiments have also been carried out for different coupling strengths and diabatic cooling rates to examine the model sensitivity to these paramenters. The model results indicate that air-sea interaction could induce a secondary SST front on the shelf. Comparisons of model results with observations obtained during the Genesis of Atlantic Lows Experiment conducted off the east coasts of the Carolinas during January and February 1986 qualitatively confirm our finding.     

Effects of chemically spiked sediments on estuarine benthic communities: a controlled mesocosm study

Ambient sediments were collected from a reference site in the North Edisto River, SC and transferred to a laboratory facility to investigate effects of chemical contaminants on estuarine infaunal communities under controlled mesocosm conditions. Sediment contaminant slurries were prepared using dried sediments collected from the reference site and spiked with a metal (copper), a polycyclic aromatic hydrocarbon (pyrene), and a pesticide (4,4^′-dichlorodiphenyltrichloroethane) to yield nominal mean effects range–median (ERM) quotients of <0.01 (no addition), 0.1, and 1.0 and applied to control, low dose (TRT A), and high dose (TRT B) treatment groups, respectively. Sediment samples for contaminant and benthic analyses were collected at the start of the experiment, 1 month after dosing, and 3 months after dosing. Near-nominal mean ERM quotients of 0.001, 0.075, and 0.818 were measured initially after dosing and remained fairly constant throughout the experiment. Measures of benthic condition, diversity, and richness were significantly reduced in both treatment groups relative to the control 1 month after dosing and persisted in TRT B at 3 months. The results demonstrate that benthic community effects can be observed at mean ERM quotients that are about an order of magnitude lower than levels that have been shown to be associated with significant toxicity in acute laboratory bioassays with single species (e.g., amphipods) in other studies.     

Assessment of phenol infiltration resilience in soil media by HYDRUS-1D transport model for a waste discharge site

The movement of contaminants through soil imparts a variety of geo-environmental problem inclusive of lithospheric pollution. Near-surface aquifers are often vulnerable to contamination from surface source if overlying soil possesses poor resilience or contaminant attenuation capacity. The prediction of contaminant transport through soil is urged to protect groundwater from sources of pollutants. Using field simulation through column experiments and mathematical modeling like HYDRUS-1D, assessment of soil resilience and movement of contaminants through the subsurface to reach aquifers can be predicted. An outfall site of effluents of a coke oven plant comprising of alarming concentration of phenol (4–12.2 mg/L) have been considered for studying groundwater condition and quality, in situ soil characterization, and effluent characterization. Hydrogeological feature suggests the presence of near-surface aquifers at the effluent discharge site. Analysis of groundwater of nearby locality reveals the phenol concentration (0.11–0.75 mg/L) exceeded the prescribed limit of WHO specification (0.002 mg/L). The in situ soil, used in column experiment, possess higher saturated hydraulic conductivity (K _S ?=?5.25?×?10^?4 cm/s). The soil containing 47 % silt, 11 % clay, and 1.54 % organic carbon content was found to be a poor absorber of phenol (24 mg/kg). The linear phenol adsorption isotherm model showed the best fit (R ²?=?0.977, RMSE?=?1.057) to the test results. Column experiments revealed that the phenol removal percent and the length of the mass transfer zone increased with increasing bed heights. The overall phenol adsorption efficiency was found to be 42–49 %. Breakthrough curves (BTCs) predicted by HYDRUS-1D model appears to be close fitting with the BTCs derived from the column experiments. The phenol BTC predicted by the HYDRUS-1D model for 1.2 m depth subsurface soil, i.e., up to the depth of groundwater in the study area, showed that the exhaustion point was reached within 12 days of elapsed time. This clearly demonstrated poor attenuation capacity of the soil to retard migration of phenol to the groundwater from the surface outfall site. Suitable liner, based on these data, may be designed to inhibit subsurface transport of phenol and thereby to protect precious groundwater from contamination.     

Effects of climate and landcover change on stream discharge in the Ozark Highlands,USA

Stream discharge of a watershed is affected and altered by climate and landcover changes. These effects vary depending on the magnitude and interaction of the changes, and need to be understood so that local water resource availability can be evaluated and socioeconomic development within a watershed be pursued and managed in a way sustainable with the local water resources. In this study, the landcover and climate change effects on stream discharge from the Jacks Fork River basin in the Ozark Highlands of the south-central United States were examined in three phases: site observation and data collection, model calibration and simulation, and model experiment and analysis. Major results of the study show that climate fluctuations between wet and dry extremes resulted in the same change of the basin discharge regardless of the landcover condition in the basin. On the other hand, under a specified climate condition landcover change from a grassland basin to a fully forested basin only resulted in about one half of the discharge change caused by the climate variation. Furthermore, when landcover change occurred simultaneously with climate variation, the basin discharge change amplified significantly and became larger than the combined discharge changes caused by the climate and landcover change alone, a result indicating a synergistic effect of landcover and climate change on basin discharge variability. Agricultural Research Division, University of Nebraska-Lincoln, Contribution Number 13437.Qi Hu: Corresponding author: Dr. Qi Hu, Climate and Bio-Atmospheric Sciences Group, School of Natural Resource Sciences, 237 L.W. Chase Hall, University of Nebraska-Lincoln, Lincoln, NE 68583-0728, USA. E-mail: qhu2@unl.edu.     

Effects of an oil spill on soil physico-chemical properties of a spill site in the Niger Delta Area of Nigeria

Physico-chemical analysis of soil samples at an oil spill site in the Niger Delta Area of Nigeria showed that the total hydrocarbon content of top soil layers ranged from 0.8 to 12.4 ppm in the heavy impact zone and the oil had penetrated to a depth of 7.2 m. Hydrocarbon concentration in the medium impact zone ranged from 0.02 to 0.40 ppm while hydrocarbons were not detected in 75% of samples from the unimpacted reference zone. Measurement of heavy metal concentrations in the soils revealed a significant build-up (p<0.05) of lead, iron and zinc in the heavy impact zone. Other parameters including electrical conductivity, exchangeable cations, available phosphorus and total nitrogen in impacted soils were comparatively low while the total organic carbon was high, compared with the reference site. Textural class of soil from the different depths showed a predominantly brown sand at the top soil, loamy sand at medium depths and grey coarse sand at greater depths.     

Influence of environmental properties on macrobenthos in the northwest Indian shelf

The paper deals with the standing stock of macrobenthic infauna and associated environmental factors influencing the benthic community in the shelf region of the northwest Indian coast. The data were collected onboard FORV Sagar Sampada during the winter monsoon (January–February, 2003) to understand the community structure and the factors influencing the benthic distribution. The environmental parameters, sediment characteristics and macrobenthic infauna were collected at 26 stations distributed in the depths between 30 and 200 m extending from nobreak{Mormugao} to Porbander. Total benthic abundance was high in lower depths (50–75 m), and low values noticed at 30 m depth contour was peculiar. Polychaetes were the dominant group and were more abundant in shallow and middle depths with moderate organic matter, clay and relatively high dissolved oxygen. On the other hand crustaceans and molluscs were more abundant in deeper areas having sandy sediment and low temperature. High richness and diversity of whole benthic groups observed in deeper depths counter balanced the opposite trend shown by polychaete species. Generally benthos preferred medium grain sized texture with low organic matter and high organic matter had an adverse effect especially on filter feeders. Deposit feeding polychaetes dominated in shallow depths while carnivore species in the middle depths. Ecologically, benthos were controlled by a combination of factors such as temperature, salinity, dissolved oxygen, sand and organic matter and no single factor could be considered as an ecological master factor.     

Effects of Hurricane Katrina on benthic macroinvertebrate communities along the northern Gulf of Mexico coast

The effects of Hurricane Katrina on benthic fauna and habitat quality in coastal waters of Louisiana, Mississippi, and Alabama, USA, were assessed in October, 2005, 2 months after the hurricane made landfall between New Orleans, LA and Biloxi, MS. Benthic macrofaunal samples, sediment chemical concentrations, and water quality measurements from 60 sites in Lake Pontchartrain and Mississippi Sound were compared with pre-hurricane conditions from 2000–2004. Post-hurricane benthic communities had significant reductions in numbers of taxa, H′ diversity, and abundance as well as shifts in composition and ranking of dominant taxa. These effects were not associated with changes in chemical contamination, organic enrichment of sediments, or hypoxia and were likely due to hurricane-related scouring and changes in salinity.     

Ratio and population density of psammolittoral meiofauna as a perturbation indicator of sandy beaches in South Africa

Since 1975, pollution surveys have been carried out along the South African south and west coasts as part of a monitoring program of unpolluted areas and known and anticipated impact areas. To evaluate these data a reference or baseline level was needed. In unpolluted beaches a close relationship between meiofauna and sediment grain size was found and granulometric analysis was found to be important. This relationship was used to evaluated perturbation effects. It was found that contamination by chemical effluent depressed numbers of the nematodes and harpacticoids drastically. Mechanical perturbation increased the number of harpacticoid copepods but did not affect nematode densities. Oil in beaches decreased the number of harpacticoids, while normal nematode densities were found. Organic enrichment increased the number of nematodes, harpacticoid numbers remained normal while the perturbation effect due to sewage increased the number of both taxa.Explanations for these effects are given, together with related chemical analyses. The application of these results to other sandy beaches elsewhere is discussed briefly.     

Plutonium uptake and behavior in vegetation of the desert southwest: a preliminary assessment

Eight species of desert vegetation and associated soils were collected from the Nevada National Security Site (N2S2) and analyzed for 238Pu and 239 + 240Pu concentrations. Amongst the plant species sampled were: atmospheric elemental accumulators (moss and lichen), the very slow growing, long-lived creosote bush and the rapidly growing, short-lived cheatgrass brome. The diversity of growth strategies provided insight into the geochemical behavior and bio-availability of Pu at the N2S2. The highest concentrations of Pu were measured in the onion moss (24.27 Bq kg-1 238Pu and 52.78 Bq kg-1 239 + 240Pu) followed by the rimmed navel lichen (8.18 Bq kg-1 and 18.4 Bq kg-1 respectively), pointing to the importance of eolian transport of Pu. Brome and desert globemallow accumulated between 3 and 9 times higher concentrations of Pu than creosote and sage brush species. These results support the importance of species specific elemental accumulation strategies rather than exposure duration as the dominant variable influencing Pu concentrations in these plants. Total vegetation elemental concentrations of Ce, Fe, Al, Sm and others were also analyzed. Strong correlations were observed between Fe and Pu. This supports the conclusion that Pu was accumulated as a consequence of the active accumulation of Fe and other plant required nutrients. Cerium and Pu are considered to be chemical analogs. Strong correlations observed in plants support the conclusion that these elements displayed similar geochemical behavior in the environment as it related to the biochemical uptake process of vegetation. Soils were also sampled in association with vegetation samples. This allowed for the calculation of a concentration ratio (CR). The CR values for Pu in plants were highly influenced by the heterogeneity of Pu distribution among sites. Results from the naturally occurring elements of concern were more evenly distributed between sample sites. This allowed for the development of a pattern of plant species that accumulated Ce, Sm, Fe and Al. The highest accumulators of these elements were onion moss, lichen flowed by brome. The lowest accumulators were creosote bush and fourwing saltbush. This ranked order corresponds to plant accumulations of Pu.     

Effects of subsample size on seasonal and spatial comparisons of stream macroinvertebrate communities

We examined the effect of subsample size on the accuracy of information obtained from aquatic macroinvertebrate assemblage samples. Subsamples containing 100 organisms or 300 organisms were compared on the bases of processing time and the ability to discern ecological differences among samples. Independently of subsample size, assemblages differed between study streams, primarily reflecting an intermittent vs. permanent stream difference, and between seasons at most streams. It required, on average, two additional hours to process the larger subsamples. Larger subsamples gave significantly higher estimates of total richness and Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness, but the relative abundances of many assemblage subsets (e.g., EPT organisms and most functional feeding groups) were similar using both subsample sizes. Larger subsamples did not typically enhance the ability to discriminate between samples from different seasons, but did more accurately distinguish among streams when differences were subtle. They also appeared to avoid Type I error in comparisons of compositionally similar reaches within a study stream.     

Effect of corona discharge on the gas composition of the sample flow in a Gas Particle Partitioner

A Gas Particle Partitioner (GPP) that allows highly efficient separation of gas and particles with no effect on the thermodynamic conditions and substantially no change of the gas composition has been developed. The GPP is a coaxial arrangement with inner and outer electrodes and utilizes a corona discharge to electrically charge the particles and a strong electric field to remove them from the sample flow. Several measures were taken to avoid an influence of the corona discharge on the gas composition. The GPP can be applied for various applications. This paper focuses on the use of the GPP as a pre-filter for gas analyzers, where zero pressure drop and a minimization of the influence of the corona discharge on the gas composition are the main objective. Due to its design, the GPP introduces no changes to the thermodynamic conditions. However, corona discharge is known to produce significant amounts of ozone and oxides of nitrogen. The effect of the corona on the gas composition of the sample flow was determined under various conditions. The gas concentrations strongly depended on several aspects, such as material and diameter of the corona wire and polarity of the corona voltage. Due to the measures taken to minimize an effect on the gas composition, the concentrations of these gases could effectively be reduced. Along with the maximum gas-particle separation efficiency of near 100%, the additional O3 concentration was 42 ppbV and the additional NO2 concentration 15 ppbV. If an efficiency of 95% is acceptable, the added concentrations can be as low as 2.5 ppbV (O3) and 0.5 ppbV (NO2), respectively.     

Transport of dissolved nutrients and chlorophyll a in a tropical estuary,southwest coast of India

Intra-tidal variability in the transport of materials through the Cochin estuary was studied over successive spring and neap tides to estimate the export fluxes of nutrients and chlorophyll a into the adjoining coastal zone. The results showed that there was a substantial increase in the freshwater flow into the estuary following heavy rains (~126 mm) prior to the spring tide observations. The estuary responded accordingly with a relatively larger export through the Cochin inlet during spring tide over neap tide. Despite an increased freshwater discharge during spring tide, the export fluxes of phosphate and ammonia were high during neap tide due to their input into the estuary through anthropogenic activities. The significance of this study is that the export fluxes from the Cochin estuary could be a major factor sustaining the spectacular monsoon fishery along the southwest coast of India.     

Hg bioavailability and impact on bacterial communities in a long-term polluted soil

Different soil samples characterised by a long-term Hg-pollution were studied for Hg total content, fractionation, phytotoxicity and influence on the bacterial community. Hg pollution ranged from 1 to 50 mg kg(-1) and most of it was speciated in scarcely soluble forms. In agreement with this, the biochemical quality indexes were investigated (biomass, enzyme activities) and the bacterial community (viable heterotrophic (VH) bacteria, functional diversity) apparently was not influenced by the degree of Hg pollution. In particular, the investigated soils exhibited a low percentage of Hg-resistant (Hg(R)) bacteria ranging from less than 0.001% to 0.25% of the VH and the addition of available Hg in the form of HgCl(2) induced an enrichment of resistant Hg(R) populations. The general biodiversity of the bacterial community was evaluated by denaturing gradient gel electrophoresis of DNA of Hg spiked soil microcosms and of control soils. Hg(R) bacteria capable to grow in a minimal medium containing HgCl(2) were also isolated and identified. MerA and merB gene PCR fragments were obtained from different Hg(R) strains and the range of similarities at the DNA level and at the deduced amino acid level showed that they carried mercuric reductase and lyase. Differently from bacteria, some influence of soil Hg content on seeds' germination and root elongation was observed for Lepidium sativum L. and Solanum lycopersicum L. In conclusion, most of the Hg in these long-term polluted soils was scarcely mobile and available and did not significantly influence the soil bacterial community. The risk of potential Hg remobilization over time, that could be naturally favoured by the activity of plant roots or other inorganic processes occurring in soil, can be extenuated since bacterial community was resistant and resilient to subsequent Hg stress.     

Trace metal dynamics in fishes from the southwest coast of India

The concentration of Fe, Co, Ni, Cu, Zn, Cd, and Pb in the muscle tissue of marine fishes like Lates calcarifer, Nemipterus japonicus, Caranx melampygus, Rastrelliger kanagurta, and Cyanoglossus macrostomus was estimated from samples collected in the continental shelf waters off Kochi and Mangalore on southwest coast of India. Species-specific and spatially heterogeneous patterns of tissue metals loads were apparent within the pelagic and demersal fish species for the two regions. The concentration ranges of Fe (541.60 to 649.60 ppm), Ni (12.12 to 13.92 ppm), and Cu (3.09 to 3.62 ppm) were higher in the demersal species C. melampygus, whereas Co (9.10 to 11.80 ppm) and Zn (79.30 to 84.30 ppm) were higher in the pelagic species L. calcarifer and Cd (4.35 to 6.38 ppm) were higher in the demersal species N. japonicus, possibly due to enhanced bioavailability of these metals from ecological processes associated with upwelling during the summer monsoon. The fish species showed a great capacity to accumulate metals, with highest bioaccumulation for the essential element iron and lowest bioaccumulation for the non-essential element lead. Among the demersal species, C. melampygus and N. japonicus had high concentration factors for the metals Fe (280,268 to 322,808), Ni (88,252 to 96,891), Cu (2,351 to 2,600), and Cd (29,637 to 32,404). In contrast, the pelagic species L. calcarifer and R. kanagurta had high concentration factors for the metals Zn (40,812 to 46,892), Co (280,285 to 423,037), and Pb (854 to 1,404).     

Incidence of stress in benthic communities along the U.S. Atlantic and Gulf of Mexico coasts within different ranges of sediment contamination from chemical mixtures

Synoptic data on concentrations of sediment-associated chemical contaminants and benthic macroinfaunal community structure were collected from 1,389 stations in estuaries along the U.S. Atlantic and Gulf of Mexico coasts as part of the nationwide Environmental Monitoring and Assessment Program (EMAP). These data were used to develop an empirical framework for evaluating risks of benthic community-level effects within different ranges of sediment contamination from mixtures of multiple chemicals present at varying concentrations. Sediment contamination was expressed as the mean ratio of individual chemical concentrations relative to corresponding sediment quality guidelines (SQGs), including Effects Range-Median (ERM) and Probable Effects Level (PEL) values. Benthic condition was assessed using diagnostic, multi-metric indices developed for each of three EMAP provinces (Virginian, Carolinian, and Louisianian). Cumulative percentages of stations with a degraded benthic community were plotted against ascending values of the mean ERM and PEL quotients. Based on the observed relationships, mean SQG quotients were divided into four ranges corresponding to either a low, moderate, high, or very high incidence of degraded benthic condition. Results showed that condition of the ambient benthic community provides a reliable and sensitive indicator for evaluating the biological significance of sediment-associated stressors. Mean SQG quotients marking the beginning of the contaminant range associated with the highest incidence of benthic impacts (73–100% of samples, depending on the province and type of SQG) were well below those linked to high risks of sediment toxicity as determined by short-term toxicity tests with single species. Measures of the ambient benthic community reflect the sensitivities of multiple species and life stages to persistent exposures under actual field conditions. Similar results were obtained with preliminary data from the west coast (Puget Sound).     

Effects of soil mechanical resistance on nematode community structure under conventional sugarcane and remaining of Atlantic Forest

Nematodes present high potential as a biological indicator of soil quality. In this work, it was evaluated relations between soil physical properties and nematode community under sugarcane cropping and remaining of Atlantic Forest areas in Northeastern Pernambuco, Brazil. Soil samples were collected from September to November 2009 along two 200-m transects in both remaining of Atlantic Forest and sugarcane field at deeps of 0–10, 10–20, 20–30, 30–40, and 40–50 cm. For soil characterization, it was carried out analysis of soil size, water content, total porosity, bulk density, and particle density. The level of soil mechanical resistance was evaluated through a digital penetrometer. Nematodes were extracted per 300 cm³ of soil through centrifugal flotation in sucrose being quantified, classified according trophic habit, and identified in level of genus or family. Data were analyzed using Pearson correlation at 5% of probability. Geostatistical analysis showed that the penetration resistance, water content, total porosity, and bulk density on both forest and cultivated area exhibited spatial dependence at the sampled scale, and their experimental semivariograms were fitted to spherical and exponential models. In forest area, the ectoparasites and free-living nematodes exhibited spherical model. In sugarcane field, the soil nematodes exhibited pure nugget effect. Pratylenchus sp. and Helicotylenchus sp. were prevalent in sugarcane field, but in forest, there was prevalence of Dorylaimidae and Rhabditidae. Total amount of nematode did not differ between environments; however, community trophic structure in forest presented prevalence of free-living nematodes: omnivores followed by bacterial-feeding soil nematodes, while plant-feeding nematodes were prevalent in sugarcane field. The nematode diversity was higher in the remaining of Atlantic Forest. However, the soil mechanical resistance was higher under sugarcane cropping, affecting more directly the free-living nematodes; especially Dorylaimidae which was the most sensible to changes in soil physical properties.