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Graeme I Paton

Publications and source records attributed to Graeme I Paton.

11 recordsLinked to original sources
PubMed2006

The impact of sampling techniques on soil pore water carbon measurements of an Icelandic Histic Andosol.

The carbon in soil pore water from a Histic Andosol from Western Iceland was studied at three different scales; in the field, in undisturbed outdoor mesocosms and in laboratory repacked microcosms. Pore water was extracted using suction cup lysimeters and hollow-fibre tube sampler devices (Rhizon samplers). There were significant differences in all measured variables, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and pH values between the scales of the experiment. Gaseous constituents of soil solution and pH were more susceptible to changes in scale and the type of sampling devices used. Dissolved inorganic carbon concentrations did not differ significantly between field and mesocosm solutions but where up to 14 times lower in microcosms compared to mesocosms solutions. Rhizon samplers yielded solutions with up to 4.7 times higher DIC concentrations than porous cup lysimeters. Mesocosm surface horizon DOC concentrations were 20 and 2 times higher than in field and microcosms respectively. There was difference in DOC concentration between sampling methods (up to 8 times higher in suction cups than rhizon samplers) above 50 cm depth. Soil solution pH values did not differ between field and mesocosms and mesocosms and microcosms respectively down to 80 cm depth. Direct comparison between field and microcosms was not possible due to the nature of sampling devices. Soil solutions sampled with Rhizon samplers yielded lower pH values (up to 1.3 pH units) than those sampled with suction cups. Twenty percent of annually bound organic carbon at the soils surface under field conditions was lost by leaching of DOC and through decomposition to DIC in disturbed non-vegetated microcosms. This percentage increased to 38% in undisturbed vegetated mesocosms highlighting the importance of surface vegetation in importing carbon to soils. Increased influx of nutrients will increase growth and photosynthesis but decrease carbon sequestration in near surface horizons. Although field studies considering long-term anthropogenic changes in pedogenesis require considerable experimental duration, more rapid experiments can be conducted with confidence in micro- and mesocosms as in this research.

Aluminum↗
PubMed2005

An ecotoxicity assessment of contaminated forest soils from the Kola Peninsula.

Point source copper and nickel contamination emanating from smelters of the Kola Peninsula, NW Russia, has been observed since the mid-1960s. Previous studies have concentrated on the spatial distribution of heavy metals and their effects on forest ecology and indigenous mammals and birds. Soil is perceived as the major repository for the metal pollutants but there is a need to link the soil concentration of pollutants on the Kola Peninsula with biological parameters. Many standard methods currently used in soil ecotoxicology are developed and refined with artificial amendments and rarely modified for use in historically contaminated environments. In this study, forest soils were sampled along a 34 km transect from the smelter and analysed both chemically and with a range of ecologically relevant biological tests. Soil respiration, total nematode count, microbial heterotrophic numbers and minimal inhibitory concentrations to copper and nickel were carried out on bulk soil. The soil pore water was tested with bacterial and fungal bioluminescence-based biosensors. The heterotrophic numbers and their inhibitory concentration showed strong correlation with heavy metal concentrations while decreasing biosensor luminescence was related to increasing copper concentrations present in the pore waters. Overall, there were considerable impacts on some microbial parameters but other measures including respiration and nematode populations were insensitive to pollutant levels. While chemical analysis of heavy metals proved essential in defining the extent of contamination, environmentally relevant ecotoxicological tests complemented these data by demonstrating pollutant impact. Ecotoxicological approaches that study both the bulk soil and pore water may represent the key to understanding the fate of heavy metal in soils.

Agaricales↗
PubMed2005

Biosensor-based diagnostics of contaminated groundwater: assessment and remediation strategy.

Shallow groundwater beneath a former airfield site in southern England has been heavily contaminated with a wide range of chlorinated solvents. The feasibility of using bacterial biosensors to complement chemical analysis and enable cost-effective, and focussed sampling has been assessed as part of a site evaluation programme. Five different biosensors, three metabolic (Vibrio fischeri, Pseudomonas fluorescens 10568 and Escherichia coli HB101) and two catabolic (Pseudomonas putida TVA8 and E. coli DH5alpha), were employed to identify areas where the availability and toxicity of pollutants is of most immediate environmental concern. The biosensors used showed different sensitivities to each other and to the groundwater samples tested. There was generally a good agreement with chemical analyses. The potential efficacy of remediation strategies was explored by coupling sample manipulation to biosensor tests. Manipulation involved sparging and charcoal treatment procedures to simulate remediative engineering solutions. Sparging was sufficient at most locations.

Aliivibrio fischeri↗
PubMed2005

Prediction of [3-(14)C]phenyldodecane biodegradation in cable insulating oil-spiked soil using selected extraction techniques.

This study investigated the use of an aqueous hydroxypropyl-beta-cyclodextrin (HPCD) shake extraction in predicting microbial mineralisation and total loss of [3-(14)C]phenyldodecane associated activity in soils spiked with cable insulating oil; phenyldodecane represents a major constituent of cable insulating oil. Direct comparisons were made between freshly spiked and aged soils, and following composting. Soil was spiked with [3-(14)C]phenyldodecane (10mg kg(-1)) and stored in microcosms and aged for 1, 23, 44, 65, 90 and 153 d. At each sample time point, a variety of analyses were performed to assess the relationship between chemical and biological techniques in determining mineralisation and loss of (14)C-activity in soils under composting and non-composting conditions. Methods included determination of total (14)C-activity remaining, dichloromethane (DCM) and HPCD extractions. Mineralisation assays were also carried out to quantify the fraction of (14)C-phenyldodecane associated activity available for degradation in the soil at each time point. DCM and HPCD extractability were compared to contaminant mineralisation and to total loss of (14)C-phenyldodecane associated activity from the microcosms, after 153 d incubation. Poor relationships were found between (i) the amount of (14)C-activity mineralised and the fraction removed from the soils using DCM extraction and (ii) DCM extraction and total loss of [(14)C]phenyldodecane associated activity from the soil systems. Good relationships were observed between (i) the amount of (14)C-activity mineralised and the fraction removed from the soils using the HPCD extraction and (ii) HPCD extraction and total loss of [(14)C]phenyldodecane associated activity from the soil systems. The results of this study indicate that an aqueous HPCD extraction may be a useful tool in assessing the microbial availability of phenyldodecane in freshly and aged spiked soils.

Alkanes↗
PubMed2005

Cultivation-independent in situ molecular analysis of bacteria involved in degradation of pentachlorophenol in soil.

The central aim of this study was to determine which components of an indigenous bacterial community in pristine grassland soil were capable of degrading pentachlorophenol (PCP) using two cultivation-independent, in situ, molecular techniques. The first involved polymerase chain reaction (PCR) and reverse transcription polymerase chain reaction (RT-PCR) amplification of 16S rRNA genes from DNA and RNA, respectively, extracted from PCP-amended soil. The second involved stable isotope probing (SIP), with incubation of soil with 13C-PCP and molecular analysis of 13C-labelled RNA, derived from cells incorporating PCP or its breakdown products, after separation from 12C-RNA by ultracentrifugation. Bacterial communities were characterized by denaturing gradient gel electrophoresis (DGGE) analysis of amplification products. PCP was degraded at an approximate rate of 1.18+/-0.25 (SEM) mg kg-1 day-1 and 39% of the measurable PCP fraction was degraded after incubation for 63 days. PCP degradation was associated with significant changes in bacterial community structure, leading to the appearance of seven bands in both DNA- and RNA-based DGGE profiles, the latter providing clearer evidence of qualitative shifts in community structure. The majority of novel bands increased in relative intensity during the first 35 days and subsequently decreased in relative intensity as incubation continued. Sequence and phylogenetic analysis of six of these bands indicated most to have closest database relatives that were uncultured bacteria with sequence homologies to reported hydrocarbon degraders. No band could be detected in RNA-SIP-DGGE profiles derived from 13C-RNA fractions at day 0 but several faint bands appeared in these fractions after incubation of soil for 4 days, indicating assimilation of PCP or its degradation products. These bands increased in intensity during subsequent incubation for 21 days and decreased with further incubation. With one exception, RNA-SIP-DGGE and RNA-DGGE profiles were similar, indicating that RNA-targeted DGGE, in this case, provided a good indication of the metabolically active microbial community.

Base Sequence↗
PubMed2004

Non-exhaustive extraction techniques (NEETs) for the prediction of naphthalene mineralisation in soil.

Non-exhaustive extraction techniques (NEETs) have been shown to measure the putatively bioavailable fraction of hydrophobic compounds in soil. To date, these studies have only considered bioavailability in a single soil type. In this study, naphthalene was amended into five different soil types and mineralisation, bacterial biosensor response and the number of indigenous microbial naphthalene degraders were determined. Two NEETs were used to extract the naphthalene from soil; hydroxypropyl-beta-cyclodextrin (HPCD) and XAD-4. The HPCD extractable fraction correlated closely (R2 = 0.917) with the portion that was mineralised, but the XAD-4 extract did not (R2 = 0.044). HPCD may be ideal for the rapid assessment of the fraction of a hydrophobic organic contaminant that is available for biodegradation. A NEET that complements environmental microbial analysis will enhance our understanding of soil pollution interactions and equip us better in designing risk assessment models that integrate biological parameters. This application, although refined for soil samples, should be transferable to other environmental matrices.

Bacteriological Techniques↗
PubMed2003

Antimony bioavailability in mine soils.

Five British former mining and smelting sites were investigated and found to have levels of total Sb of up to 700 mg kg(-1), indicating high levels of contamination which could be potentially harmful. However, this level of Sb was found to be biologically unavailable over a wide range of pH values, indicating that Sb is relatively unreactive and immobile in the surface layers of the soil, remaining where it is deposited rather than leaching into lower horizons and contaminating ground water. Sb, sparingly soluble in water, was unavailable to the bacterial biosensors tested. The bioluminescence responses were correlated to levels of co-contaminants such as arsenic and copper, rather than to Sb concentrations. This suggests that soil contamination by Sb due to mining and smelting operations is not a severe risk to the environment or human health provided that it is present as immobile species and contaminated sites are not used for purposes which increase the threat of exposure to identified receptors. Co-contaminants such as arsenic and copper are more bioavailable and may therefore be seen as a more significant risk.

Antimony↗
PubMed2002

Assessment of bioavailable arsenic and copper in soils and sediments from the Antofagasta region of northern Chile.

Copper levels of nearly 500 mg l(-1) were measured in aqueous extracts of soil and sediment samples from the lowlands of Antofagasta. Arsenic levels of up to 183 mg l(-1) were found in river sediments, and 27.5 mg l(-1) arsenic was found at the location of a dam where potable water is extracted. This indicates that the arsenic contamination of water supplies reported recently for the pre-Andes may be a widespread problem throughout the region. Copper contamination from smelting activities also provides cause for concern as elevated levels were found in aqueous extracts of soil up to 20 km away from a smelter. This study went beyond traditional chemical analysis by assessing the potential benefits of using microbial biosensors as an alternative to determination of chemical speciation, to provide an environmentally relevant interpretation of soil/sediment residue levels. This approach is simple to use and enables a rapid, low cost assessment of pollutant bioavailability. It may, therefore, be of use for further investigations in the region and beyond.

Arsenic↗
PubMed2002

Evaluation of interactive toxicity of chlorophenols in water and soil using lux-marked biosensors.

An assessment of the toxicity of three chlorophenol compounds (2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP)), individually and in combinations, was made in deionised water, soil extracts and soils using the lux-marked microbial biosensors: Escherichia coli HB101 pUCD607 and Pseudomonas fluorescens 10586r pUCD607. These biosensors responded to the bioavailable fraction of pollutants enabling a rapid and ecologically relevant toxicity test. Toxicity interaction responses of pollutant mixtures were predicted after individual compounds were assessed. Synergistic interactions were observed in the response of P. fluorescens to all combinations of chlorophenols tested, while the toxicity response of E. coli varied with the matrices tested. Soil characteristics influenced the toxicity response when compared with aqueous solutions. These results highlight the significance of interactive factors and physicochemical parameters when evaluating toxicity. To develop an understanding of pollution derived hazard assessment in soils we need to integrate a wide spectrum of parameters.

Anthelmintics↗
PubMed2002

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.

Bacteria, Anaerobic↗