The biodegradation of cable oil components: impact of oil concentration, nutrient addition and bioaugmentation

The effect of cable oil concentration, nutrient amendment and bioaugmentation on cable oil component biodegradation in a pristine agricultural soil was investigated. Biodegradation potential was evaluated over 21 d by measuring cumulative CO₂ respiration on a Micro-Oxymax respirometer and ¹⁴C-phenyldodecane mineralisation using a ¹⁴C-respirometric assay. Cable oil concentration had a significant effect upon oil biodegradation. Microbial respiratory activity increased with increasing cable oil concentration, whereas ¹⁴C-phenydodecane mineralisation decreased. Bioaugmentation achieved the best cable oil biodegradation performance, resulting in increases in cumulative CO₂ respiration, and maximum rates and extents of ¹⁴C-phenyldodecane mineralisation. Generally, nutrient amendment also enhanced cable oil biodegradation, but not to the extent that degrader amendment did. Cable oil biodegradation was a function of (i) cable oil concentration and (ii) catabolic ability of microbial populations. Bioaugmentation may enhance cable oil biodegradation, and is dependent upon composition, cell number and application of catabolic inocula to soil.     

The effect of soil:water ratios on the induction of isoproturon, cypermethrin and diazinon mineralisation

The rate of pesticide biodegradation does not remain constant with time, and is dependent on the physico-chemical properties of the soil and of the pesticide as well as on the biology of the soil. Prolonged or repeated contact between soil microbes and pesticides has been shown to result in an increase in the rate and extent of biodegradation. This work assessed the impact of the soil:water ratio on measurement of catabolic induction for ¹⁴C-isoproturon, ¹⁴C-diazinon and ¹⁴C-cypermethrin. Slurrying (1:1 and 1:3 soil:water) with agitation resulted in significantly higher rates and extents of mineralisation than the non-slurried system (P ? 0.05; 1:0 soil:water), except for the mineralisation of ¹⁴C-diazinon where the greatest extent of mineralisation occurred in non-slurried soil. Slurrying without agitation resulted in the significant lower mineralisation in all cases (P ? 0.05). There was a significant interaction between the soil:water ratio and length of contact (P ? 0.05). Whilst the use of slurried systems can enhance the extent and rate of mineralisation, there is no improvement in reproducibility, and so for the measurement of catabolic induction, the use of field conditions will lead to a more environmentally relevant measurement.     

Fish Migration, Dams, and Loss of Ecosystem Services in the Mekong Basin

The past decade has seen increased international recognition of the importance of the services provided by natural ecosystems. It is unclear however whether such international awareness will lead to improved environmental management in many regions. We explore this issue by examining the specific case of fish migration and dams on the Mekong river. We determine that dams on the Mekong mainstem and major tributaries will have a major impact on the basin’s fisheries and the people who depend upon them for food and income. We find no evidence that current moves towards dam construction will stop, and consider two scenarios for the future of the fisheries and other ecosystems of the basin. We conclude that major investment is required in innovative technology to reduce the loss of ecosystem services, and alternative livelihood strategies to cope with the losses that do occur.     

Application of enzyme-linked immunosorbent assay analysis for determination of monensin in environmental samples

There is growing concern that antibiotic use in livestock production is contributing to contamination of soil and aquatic environments. Monensin, a polyether ionophore antibiotic, accounts for approximately 13% of total subtherapeutic livestock antibiotic usage in the USA and has been widely detected in aquatic environments. Due to insufficient ultraviolet absorbance, liquid chromatography analysis of monensin in environmental samples is limited to equipment with mass spectrometry (e.g., liquid chomatography-mass spectrometry [LC-MS]). However, LC-MS equipment is costly, and extensive sample preparation and clean-up is often required. Rapid, low-cost analytical techniques are needed to monitor for monensin residues in the environment. In this study, a commercially available enzyme-linked immunosorbent assay (ELISA) for detecting monensin in animal feed extracts was evaluated for determination of monensin in water, soil, and manure. The monensin ELISA was highly sensitive, with limits of detection and quantification at 1.5 and 3.0 microg L(-1), respectively. Recovery of monensin in spiked water samples was approximately 100%. Cross-reactivity was not observed with similar polyether ionophores, tetracyclines, macrolides, or sulfonamides. Concentrations of monensin using ELISA were greater than concentrations measured with LC-MS. This is attributed to cross-reactivity of the monensin ELISA toward structurally similar monensin compounds, such as factors (slight naturally produced structural variants) and metabolites. Results from this study showed that ELISA can be a reliable, rapid, and low-cost alternative to LC-MS analysis of environmental samples.     

Changes in contaminant mass discharge from DNAPL source mass depletion: evaluation at two field sites

Changes in contaminant fluxes resulting from aggressive remediation of dense nonaqueous phase liquid (DNAPL) source zone were investigated at two sites, one at Hill Air Force Base (AFB), Utah, and the other at Ft. Lewis Military Reservation, Washington. Passive Flux Meters (PFM) and a variation of the Integral Pumping Test (IPT) were used to measure fluxes in ten wells installed along a transect down-gradient of the trichloroethylene (TCE) source zone, and perpendicular to the mean groundwater flow direction. At both sites, groundwater and contaminant fluxes were measured before and after the source-zone treatment. The measured contaminant fluxes (J; ML(-2)T(-1)) were integrated across the well transect to estimate contaminant mass discharge (M(D); MT(-1)) from the source zone. Estimated M(D) before source treatment, based on both PFM and IPT methods, were approximately 76 g/day for TCE at the Hill AFB site; and approximately 640 g/day for TCE, and approximately 206 g/day for cis-dichloroethylene (DCE) at the Ft. Lewis site. TCE flux measurements made 1 year after source treatment at the Hill AFB site decreased to approximately 5 g/day. On the other hand, increased fluxes of DCE, a degradation byproduct of TCE, in tests subsequent to remediation at the Hill AFB site suggest enhanced microbial degradation after surfactant flooding. At the Ft. Lewis site, TCE mass discharge rates subsequent to remediation decreased to approximately 3 g/day for TCE and approximately 3 g/day for DCE approximately 1.8 years after remediation. At both field sites, PFM and IPT approaches provided comparable results for contaminant mass discharge rates, and show significant reductions (>90%) in TCE mass discharge as a result of DNAPL mass depletion from the source zone.     

Development of phenanthrene catabolism in natural and artificial soils

The characteristics of natural soils often vary from those of artificial soil (e.g. OECD), which may lead to substantial differences in the bioavailability of test substances. The aim of this investigation was to characterise the development of phenanthrene catabolism in both natural and artificial soils with varying total organic carbon (TOC) content after 1, 14, 42 and 84 d soil-phenanthrene contact time. Indigenous catabolic activity was measured via the addition of 14C-phenanthrene using the respirometric soil slurry assay. Notably, the lag phases, fastest rates and total extents of 14C-phenanthrene degradation were relatively comparable in soils with similar TOC content after 1 d contact time. However, natural soils generally exhibited significantly shorter lag phases, faster rates and higher extents of mineralisation, than their artificial counterparts after 42 and 84 d contact time. Such findings suggest that the extrapolation of results from artificial soils to real/natural soils may not be straightforward.     

Rapid quantification of polycyclic aromatic hydrocarbons in hydroxypropyl-beta-cyclodextrin (HPCD) soil extracts by synchronous fluorescence spectroscopy (SFS)

Synchronous fluorescence spectroscopy (SFS) was directly applied to rapidly quantify selected polycyclic aromatic hydrocarbons (PAHs: benzo[a]pyrene and pyrene) in aqueous hydroxypropyl-beta-cyclodextrin (HPCD) soil extract solutions from a variety of aged contaminated soils containing four different PAHs. The method was optimized and validated. The results show that SFS can be used to analyse benzo[a]pyrene and pyrene in HPCD based soil extracts with high sensitivity and selectivity. The linear calibration ranges were 4.0x10(-6)-1.0x10(-3)mM for benzo[a]pyrene and 6.0x10(-6)-1.2x10(-3)mM for pyrene in 10mM HPCD aqueous solution alone. The detection limits according to the error propagation theory for benzo[a]pyrene and pyrene were 3.9x10(-6) and 5.4x10(-6)mM, respectively. A good agreement between SFS and HPLC was reached for both determinations of PAHs in HPCD alone and in soil HPCD extracts. Hence, SFS is a potential means to simplify the present non-exhaustive hydroxypropyl-beta-cyclodextrin (HPCD)-based extraction technique for the evaluation of PAH bioavailability in soil.     

DEVELOPMENT OF AN INVERTEBRATE COMMUNITY INDEX FOR AN ALABAMA COASTAL PLAIN WATERSHED1

ABSTRACT: Activities such as agriculture, silviculture, and mining contribute nonpoint pollution to Alabama's streams through polluted runoff and excessive sedimentation. Highly erodible soils characteristic of the Choctawhatchee‐Pea Rivers watershed, combined with intense rainfall and land use practices, contribute large amounts of sediment to streams. Biological monitoring can reflect the acute impacts of pollutants as well as prolonged effects of habitat alteration, and development of biological criteria is important for the establishment of enforceable laws regarding nonpoint source pollution. Macroinvertebrates were collected from 49 randomly selected sites from first through sixth‐order streams in the Choctawhatchee‐Pea Rivers watershed and were identified to genus level. Thirty‐eight candidate metrics were examined, and an invertebrate community index (ICI) was calibrated by eliminating metrics that failed to separate impaired from unimpaired streams. Each site was scored with those metrics, and narrative scores were assigned based on ICI scores. Least impacted sites scored significantly lower than sites impacted by row crop agriculture, cattle, and urban land uses. Conditions in the watershed suggest that the entire area has experienced degradation through past and current land use practices. An initial validation of the index was performed and is described. Additional evaluations of the index are in progress.     

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