Search

A reliance on diesel generated power and a history of imperfect fuel management have created a legacy of petroleum hydrocarbon contamination at subantarctic Macquarie Island. Increasing environmental awareness and advances in contaminant characterisation and remediation technology have fostered an impetus to reduce the environmental risk associated with legacy sites. A funnel and gate permeable bio-reactive barrier (PRB) was installed in 2014 to address the migration of Special Antarctic Blend diesel from a spill that occurred in 2002, as well as older spills and residual contaminants in the soil at the Main Power House. The PRB gate comprised of granular activated carbon and natural clinoptilolite zeolite. Petroleum hydrocarbons migrating in the soil water were successfully captured on the reactive materials, with concentrations at the outflow of the barrier recorded as being below reporting limits. The nutrient and iron concentrations delivered to the barrier demonstrated high temporal variability with significant iron precipitation observed across the bed. The surface of the granular activated carbon was largely free from cell attachment while natural zeolite demonstrated patchy biofilm formation after 15 months following PRB installation. This study illustrates the importance of informed material selection at field scale to ensure that adsorption and biodegradation processes are utilised to manage the environmental risk associated with petroleum hydrocarbon spills. This study reports the first installation of a permeable bio-reactive barrier in the subantarctic., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The application of controlled release nutrient (CRN) materials to permeable reactive barriers to promote biodegradation of petroleum hydrocarbons in groundwater was investigated. The longevity of release, influence of flow velocity and petroleum hydrocarbon concentration on nutrient release was assessed using soluble and ion exchange CRN materials; namely Polyon™ and Zeopro™. Both CRN materials, assessed at 4 °C and 23 °C, demonstrated continuing release of nitrogen, phosphorus and potassium (N-P-K) at 3500 bed volumes passing, with longer timeframes of N-P-K release at 4 °C. Zeopro™-activated carbon mixtures demonstrated depletion of N-P-K prior to 3500 bed volumes passing. Increased flow velocity was shown to lower nutrient concentrations in Polyon™ flow cells while nutrient release from Zeopro™ was largely unchanged. The presence of petroleum hydrocarbons, at 1.08 mmol/L and 3.25 mmol/L toluene, were not shown to alter nutrient release from Polyon™ and Zeopro™ across 14 days. These findings suggest that Polyon™ and Zeopro™ may be suitable CRN materials for application to PRBs in low nutrient environments., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Bioremediation has been used to remediate petroleum hydrocarbon (PHC)-contaminated sites in polar regions; however, limited knowledge exists in understanding how frozen conditions influence factors that regulate microbial activity. We hypothesized that increased liquid water (θ(liquid) ) would affect nutrient supply rates (NSR) and gas diffusion under frozen conditions. If true, management practices that increase θ(liquid) should also increase bioremediation in polar soils by reducing nutrient and oxygen limitations. Influence of θ(liquid) on NSR was determined using diesel-contaminated soil (0-8,000 mg kg(-1)) from Casey Station, Antarctica. The θ(liquid) was altered between 0.007 and 0.035 cm(3) cm(-3) by packing soil cores at different bulk densities. The nutrient supply rate of NH 4+ and NO 3-, as well as gas diffusion coefficient, D(s), were measured at two temperatures, 21°C and -5°C, to correct for bulk density effects. Freezing decreased NSR of both NH 4+ and NO 3-, with θ(liquid) linked to nitrate and ammonia NSR in frozen soil. Similarly for D(s), decreases due to freezing were much more pronounced in soils with low θ(liquid) compared to soils with higher θ(liquid) contents. Additional studies are needed to determine the relationship between degradation rates and θ(liquid) under frozen conditions., (Copyright © 2011 SETAC.)

Potential microbial activities are commonly used to assess soil toxicity of petroleum hydrocarbons (PHC) and are assumed to be a surrogate for microbial activity within the soil ecosystem. However, this assumption needs to be evaluated for frozen soil, in which microbial activity is limited by liquid water (θ(liquid)). Influence of θ(liquid) on in situ toxicity was evaluated and compared to the toxicity endpoints of potential microbial activities using soil from an aged diesel fuel spill at Casey Station, East Antarctica. To determine in situ toxicity, gross mineralization and nitrification rates were determined by the stable isotope dilution technique. Petroleum hydrocarbon-contaminated soil (0-8,000 mg kg(-1)), packed at bulk densities of 1.4, 1.7, and 2.0 g cm(-3) to manipulate liquid water content, was incubated at -5°C for one, two, and three months. Although θ(liquid) did not have a significant effect on gross mineralization or nitrification, gross nitrification was sensitive to PHC contamination, with toxicity decreasing over time. In contrast, gross mineralization was not sensitive to PHC contamination. Toxic response of gross nitrification was comparable to potential nitrification activity (PNA) with similar EC25 (effective concentration causing a 25% effect in the test population) values determined by both measurement endpoints (400 mg kg(-1) for gross nitrification compared to 200 mg kg(-1) for PNA), indicating that potential microbial activity assays are good surrogates for in situ toxicity of PHC contamination in polar regions., (Copyright © 2011 SETAC.)

Fuel spills in Antarctica typically occur in rare ice-free oases along the coast, which are areas of extreme seasonal freezing. Spills often occur at subzero temperatures, but little is known of ecosystem sensitivity to pollutants, in particular the influence that soil liquid water and low temperature have on toxicity of petroleum hydrocarbons (PHC) in Antarctic soil. To evaluate PHC toxicity, 32 locations at an aged diesel spill site in Antarctica were sampled nine times to encompass frozen, thaw, and refreeze periods. Toxicity was assessed using potential activities of substrate-induced respiration, basal respiration, nitrification, denitrification, and metabolic quotient as well as microbial community composition and bacterial biomass. The most sensitive indicator was community composition with a PHC concentration effecting 25% of the population (EC25) of 800 mg/kg, followed by nitrification (2,000 mg/kg), microbial biomass (2,400 mg/kg), and soil respiration (3,500 mg/kg). Despite changes in potential microbial activities and composition over the frozen, thaw, and refreeze period, the sensitivity of these endpoints to PHC did not change with liquid water or temperature. However, the variability associated with ecotoxicity data increased at low liquid water contents. As a consequence of this variability, highly replicated (n = 50) experiments are needed to quantify a 25% ecological impairment by PHCs in Antarctic soils at a 95% level of significance. Increases in biomass and respiration associated with changes in community composition suggest that PHC contamination in Antarctic soils may have irrevocable effects on the ecosystem.

Sub-Antarctic islands have been subjected to petroleum hydrocarbon spills, yet no information is available regarding the toxicity of petroleum hydrocarbons to these subpolar soils. The purpose of the present study was to identify soil biogeochemical toxicity end points for petroleum hydrocarbon contamination in sub-Antarctic soil. Soil from Macquarie Island, a sub-Antarctic island south of Australia, was collected and exposed to 10 concentrations of Special Antarctic Blend (SAB) diesel fuel, ranging from 0 to 50,000 mg fuel/kg soil, for a 21-d period. The sensitivity of nitrification, denitrification, carbohydrate utilization, and total soil respiration to SAB fuel was assessed. Potential nitrification activity was the most sensitive indicator of SAB contamination assessed for nitrogen cycling, with an IC20 (concentration that results in a 20% change from the control response) of 190 mg fuel/ kg soil. Potential denitrification activity was not as sensitive to SAB contamination, with an IC20 of 950 mg fuel/kg soil for nitrous oxide production. Nitrous oxide consumption was unaffected by SAB contamination. Carbohydrate utilization (respiration caused by sucrose) was a more sensitive indicator (IC20, 16 mg fuel/kg soil) of SAB contamination than total respiration (IC20, 220 mg fuel/kg soil). However, total soil respiration was a more responsive measurement end point, increasing soil respiration over a 72-h period by 17 mg of CO2, compared to a change of only 2.1 mg of CO2 for carbohydrate utilization. Our results indicate that IC20s varied between 16 to 950 mg fuel/kg soil for Macquarie Island soil spiked with SAB diesel fuel. These results indicate that current cleanup levels derived from temperate zones may be too liberal for soil contamination in sub-Antarctic islands.

Clean sediment collected from O'Brien Bay, East Antarctica, was artificially contaminated with a mix of Special Antarctic Blend diesel fuel and lubricating oil and deployed in two uncontaminated locations (O'Brien and Sparkes Bays) and a previously contaminated bay (Brown Bay) to evaluate whether a history of prior contamination would influence the biodegradation process. Detailed analysis of the hydrocarbon composition in the sediment after 11 weeks revealed different patterns of degradation in each bay. Biodegradation indices showed that hydrocarbon biodegradation occurred in all three bays but was most extensive in Brown Bay. This study shows that even within a relatively small geographical area, the longevity of hydrocarbons in Antarctic marine sediments can be variable. Our results are consistent with faster natural attenuation of spilt oil at sites with previous exposure to oil but further work is needed to confirm this. Such information would be useful when evaluating the true risk and longevity of oils spills.

Improved testing and remediation procedures for sites contaminated with petroleum hydrocarbons are a priority in remote cold regions such as Antarctica, where costs are higher and remediation times are longer. Isoprenoid/n-alkane ratios are commonly used to determine the extent of biodegradation at low levels but are not useful once the n-alkanes have been removed. This study demonstrates how the diastereomers of the acyclic isoprenoids can be used to determine the extent of biodegradation in moderately biodegraded fuel in soils from a bioremediation trial at Casey Station, Antarctica. The biological diastereomers of pristane (meso; RS = SR) are depleted more rapidly during moderate biodegradation than the geological or mature diastereomers (RR and SS), and thus, the ratio of pristane diastereomers can determine the level of biodegradation. The statistical difference among mean diastereomer ratios for samples grouped according to the biodegradation scale and pristane/phytane ratios was highly significant. The ratios of norpristane and phytane diastereomers also change with biodegradation in a similar fashion, and different levels of sensitivity exist for each. Additional benefits are that the method can be performed on conventional gas chromatographs by non-specialist chemists and that the ratios are independent of evaporation and do not necessarily require a non-biodegraded reference (T0) sample. This study details a simple alternative method for determining the extent of biodegradation of fuels at moderate levels that can be applied to a wide range of petroleum products.

Although petroleum contamination has been identified at many Antarctic research stations, and is recognized as posing a significant threat to the Antarctic environment, full-scale in situ remediation has not yet been used in Antarctica. This is partly because it has been assumed that temperatures are too low for effective biodegradation. To test this, the effects of temperature on the hydrocarbon mineralisation rate in Antarctic terrestrial sediments were quantified. 14C-labelled octadecane was added to nutrient amended microcosms that were incubated over a range of temperatures between -2 and 42 degrees C. We found a positive correlation between temperature and mineralisation rate, with the fastest rates occurring in samples incubated at the highest temperatures. At temperatures below or near the freezing point of water there was a virtual absence of mineralisation. High temperatures (37 and 42 degrees C) and the temperatures just above the freezing point of water (4 degrees C) showed an initial mineralisation lag period, then a sharp increase in the mineralisation rate before a protracted plateau phase. Mineralisation at temperatures between 10 and 28 degrees C had no initial lag phase. The high rate of mineralisation at 37 and 42 degrees C was surprising, as most continental Antarctic microorganisms described thus far have an optimal temperature for growth of between 20 and 30 degrees C and a maximal growth temperature <37 degrees C. The main implications for bioremediation in Antarctica from this study are that a high-temperature treatment would yield the most rapid biodegradation of the contaminant. However, in situ biodegradation using nutrients and other amendments is still possible at soil temperatures that occur naturally in summer at the Antarctic site we studies (Casey Station 66 degrees 17(') S, 110 degrees 32(') E), although treatment times could be excessively long.

Two molecular methods were used to investigate the microbial population of Antarctic marine sediments to determine the effects of petroleum and heavy metal pollution. Sediment samples were collected in a nested design from impacted and non-impacted locations. A detailed description of the diversity of the microbial population in two samples was obtained using 16S ribosomal DNA clone libraries constructed from an impacted and a non-impacted location. The clone libraries were very similar with the exception of two sequence clusters containing clones from only the impacted location. All samples were analysed by denaturing gradient gel electrophoresis. The band patterns generated were transformed into a presence/absence matrix and a multivariate approach was used to test for differences in the locations. Statistically significant differences were observed both between and within locations. Impacted locations showed a greater variability within themselves than the control locations. Correlations between the community patterns and environmental variables suggested that pollution was one of a number of factors affecting the microbial community composition. [Copyright &y& Elsevier]

Abstract: A laboratory incubation study was conducted on a petroleum-contaminated soil from Macquarie Island in sub-Antarctic Australia to develop a target O2 level for bioventing. The soil was amended with NH4NO3 (175mg Nkg−1 soil) and 14C-hexadecane (250mgkg−1 soil) and placed in sealed respirometry chambers. The headspaces in the chambers were adjusted to 0, 1, 2.6, 5.2, 10.5, and 20.9% O2. Each chamber was connected to an NaOH CO2 trap and to an O2 feed line (except the 0% O2 chambers were connected to an N2 feed line). Chambers were supplied with O2 in response to pressure drop resulting from CO2 trapping. Soils were incubated at 6°C for 12weeks. O2 consumption and petroleum degradation were maximized in chambers with 10.4% O2. There was a slight decline in both O2 consumption and petroleum degradation at 20.9% O2. As O2 concentrations declined below 10.4% O2 both O2 consumption and petroleum degradation declined markedly. 14C collected in the CO2 traps did not follow this pattern, but was greater in the 1% O2 chambers than in 2.6 or 5.2% O2 chambers. Nitrogen remaining at the conclusion of the study indicated that nitrate was completely consumed in the 0, 1, 2.6, and 5.2% O2 chambers. nC17:pristane and nC18:phytane ratios in the soil at the conclusion of the incubation were significantly lower in the 10.4% O2 chambers than in those with 20.9% O2, and more petroleum hydrocarbons were consumed in the 10.4% chambers. Preferential degradation of pristane and phytane in the presence of limited O2 may be the result of denitrification, evidenced by lower residual nitrate levels in the 10.4 than the 20.9% O2 environment. Ten percent O2 is suggested as a target for O2 enhanced bioremediation. [Copyright &y& Elsevier]

Abstract: Many contaminated cold region soils are deficient in nitrogen, and addition of the proper amount of this nutrient can increase the biodegradation rate. However, it has been demonstrated that excess nitrogen can depress the rate of microbial activity and petroleum degradation in contaminated soils due to osmotic soil water potential depression. This study was undertaken to optimize nutrient amendments in a sub-Antarctic soil. Soil collected from a petroleum-contaminated site on Macquarie Island, Australia, located in the sub-Antarctic, contained approximately 5250 mg kg−1 of hydrocarbons and 20.9% H2O. Inorganic nitrogen levels prior to fertilization were <1.0 mg kg−1 of NO3–N and 1.3 mg kg−1 of NH4–N. Inorganic nitrogen, in the form of NH4Cl, was added at rates of 0, 125, 250, 375, 500, and 625 mg nitrogen kg−1 of dry soil. On a soil water basis (NH2O—calculated by dividing inorganic soil nitrogen by the soil water content), applied plus native N levels were 6, 604, 1202, 1800, 2399, and 2997 mg nitrogen kg−1 of soil water for these treatments. The soil was incubated at 6 °C. O2 consumption was monitored for approximately 4 months. Maximum O2 uptake was observed with the 125 and 250 mg nitrogen kg−1 of soil application rates. Respiration in the 625 mg kg−1 treatment was slightly lower than that in the untreated soil, although they were not statistically different. Respiration was maximized when NH2O was 604 mg nitrogen kg−1 H2O, and was depressed when it reached 1800 mg N kg−1 H2O. Residual soil petroleum following incubation was least in soil amended with 125 mg N kg−1 (NH2O =604) and was greater in unfertilized soils or in soils receiving 250 mg N kg−1 or more (NH2O ≥1202). Thus, the rate of bioremediation was maximized when NH2O was maintained below 1200 mg N kg−1 soil H2O. Whereas previous studies have indicated that bioremediation in polar and sub-polar region soils are inhibited by nitrogen amendments above 2500 mg N kg−1 H2O, results from this study indicated inhibition at a lower level of 1200 mg N kg−1 H2O. [Copyright &y& Elsevier]

In situ chemical oxidation (ICO) has been identified as a potential technology for the remediation of petroleum hydrocarbon contaminated sites in Antarctica. ICO involves introducing reactive chemicals to contaminated soils so that organics such as petroleum hydrocarbons are oxidised to environmentally innocuous compounds. This paper details two field trials that were undertaken to evaluate the feasibility of using a surface application of these oxidative treatments (Fenton''s reagent, hydrogen peroxide and sodium hypochlorite) to remediate petroleum contaminated soil at Old Casey Station, East Antarctica. Results show that the ICO technology used at this site, where contamination occurred over a decade ago, did not significantly reduce petroleum hydrocarbon concentrations and would likely hinder biodegradation through the destruction of subsurface microbial communities. Further treatment testing and optimisation is required before ICO would be an effective remediation strategy for petroleum contaminated sites in Antarctica. However, the near complete destruction of subsurface microbiota, coupled with a discoloured orange soil residue and soil heating, mean that other more environmentally sensitive techniques such as bioremediation are our preferred treatment methodology. [Copyright &y& Elsevier]