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Kirk T Semple

Publications and source records attributed to Kirk T Semple.

At least 19 recordsLinked to original sources
PubMed2007

Biogenic volatile organic compounds as potential carbon sources for microbial communities in soil from the rhizosphere of Populus tremula.

Catabolism of a (14)C-labelled volatile monoterpene compound (geraniol) to (14)CO(2) was investigated in soils taken from the rhizosphere at distances up to 200 cm from the trunks of three small Populus tremula trees growing at different sites in Slovenia. Emissions of limonene of up to 18 microg m(-2) h(-1) were detected from the soil surface at each site. Evolution of (14)C-labelled CO(2) was measured as a product of catabolism of (14)C-labelled geraniol introduced into the soil samples. Indigenous soil microorganisms degraded the geraniol rapidly. There was a significant difference in relative lag times and rates of catabolism along the gradient from the tree trunks, with relatively longer lag times and lower rates occurring in soil samples from the farthest point from the tree.

Acyclic Monoterpenes↗
PubMed2006

Further validation of the HPCD-technique for the evaluation of PAH microbial availability in soil.

There is currently considerable scientific interest in finding a chemical technique capable of predicting bioavailability; non-exhaustive extraction techniques (NEETs) offer such potential. Hydroxypropyl-beta-cyclodextrin (HPCD), a NEET, is further validated through the investigation of concentration ranges, differing soil types, and the presence of co-contaminants. This is the first study to demonstrate the utility of the HPCD-extraction technique to predict the microbial availability to phenanthrene across a wide concentration range and independent of soil-contaminant contact time (123 d). The efficacy of the HPCD-extraction technique for the estimation of PAH microbial availability in soil is demonstrated in the presence of co-contaminants that have been aged for the duration of the experiment together in the soil. Desorption dynamics are compared in co-contaminant and single-PAH contaminated spiked soils to demonstrate the occurrence of competitive displacement. Overall, a single HPCD-extraction technique proved accurate and reproducible for the estimation of PAH bioavailability from soil.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2006

Prediction of mono- and polycyclic aromatic hydrocarbon degradation in spiked soils using cyclodextrin extraction.

In this study, an aqueous-based hydroxypropyl-beta-cyclodextrin (HPCD) extraction technique was assessed for its capacity to determine the microbially degradable fraction of mono- and polycyclic aromatic hydrocarbons in four dissimilar soils. A linear relationship (slope=0.90; R2=0.89), approaching 1:1 between predicted and observed phenanthrene mineralization, was demonstrated for the cyclodextrin extraction; however, the water only extraction underestimated the microbially available fraction by a factor of three (slope=3.35; R2=0.64). With respect to determining the mineralizable fraction of p-cresol in soils, the cyclodextrin extraction (slope=0.94; R2=0.84) was more appropriate than the water extraction (slope=1.50; R2=0.36). Collectively, these results suggested that the cyclodextrin extraction technique was suitable for the prediction of the mineralizable fraction of representative PAHs and phenols present in dissimilar soils following increasing soil-contaminant contact times. The assessment of the microbial availability of contaminants in soils is important for a more representative evaluation of soil contamination.

Carbon Radioisotopes↗
PubMed2005

Linking catabolism to cyclodextrin extractability: determination of the microbial availability of PAHs in soil.

When assessing the potential of a contaminated site for bioremediation, it is desirable to know how much of the contaminant(s) is available for microbial degradation, thus allowing the likelihood of successful bioremediation to be predicted. The aims of this study were to investigate the degradation of PAHs in two soils by a catabolic inoculum and indigenous soil microflora and link this to the cyclodextrin extractable fraction in the presence of transformer oil (0.05, 0.01, or 0.005%). This study showed very little difference between indigenous and inoculum-derived degradation for phenanthrene in laboratory-aged soil, and strong relationships were also observed between both of the microbial degradative conditions and the amount of phenanthrene extracted by cyclodextrin. Furthermore, the indigenous degradation of PAHs in a field-contaminated soil showed significant linear correlations with the cyclodextrin extractable fraction, with gradients approximating to 1. There are several novel facets to this study. First, in aged, contaminated soils, indigenous microflora gave an equally sensitive determination of degradative availability as that measured by the catabolic inoculum. Second, this is the first time intrinsic biodegradation of PAHs has been predicted by the cyclodextrin extraction in laboratory-spiked and field-contaminated soils. The cyclodextrin extraction technique represents a powerful tool for predicting the extent of intrinsic and augmented microbial degradation and will be useful in the assessment of contaminated land prior to bioremediation.

Biodegradation, Environmental↗
PubMed2005

Distribution of aged 14C-PCB and 14C-PAH residues in particle-size and humic fractions of an agricultural soil.

Organic matter is considered to be the single most importantfactor limiting availability and mobility of persistent organic pollutants (POPs) in soil. This study aimed to characterize the distribution of 14C-PCB (congeners 28 and 52) and 14C-PAH (fluoranthene and benzo[a]pyrene) residues in an Orthic Luvisol soil obtained from two lysimeter studies initiated in 1990 at the Agrosphere Institute (Forschungszentrum Jülich GmbH, Germany). The lysimeter soils contained a low-density OM fraction, isolated during soil washing, which contained a significant fraction (3-12%) of the total 14C-activity. Soils were also fractionated according to three particle sizes: >20, 20-2, and <2 microm. Relative affinity values of 14C-activity for the different particle sizes varied in the order 20-2 microm > (<2 microm) approximately (>20 microm) for the PCBs. Relative affinity values of 14C-activity for the different particle sizes varied in the order 20-2 microm > (<2 microm) > (>20 microm) for the PAHs. The distribution of 14C-PCB or 14C-PAH residues in the organic and inorganic matrixes of the particle-size fractions was determined using methyl isobutyl ketone (MIBK). 14C-PCB and 14C-PAH-associated activities were primarily located in the humin fraction of the 20-2 and <2 microm particle-size fractions of the soil. A small fraction was associated with the fulvic and humic acid fractions; these were quantitatively more important for the PAHs than the PCBs. There appeared to be a high degree of association of 14C-activity with the mineral fraction following MIBK separation of the humic fractions, ranging between 8 and 52% for 14C-PCBs and 57-80% for 14C-PAHs. The mineral (inorganic) component of the soils apparently played a significant (previously unreported) role in the sequestration of both PCBs 28 and 52 and the PAHs fluoranthene and benzo[a]pyrene.

Agriculture↗
PubMed2005

Can microbial mineralization be used to estimate microbial availability of organic contaminants in soil?

The aim of this study was to characterize the behaviour of a PAH-degrading bacterium to determine whether mineralization plateaus as a result of substrate removal, a decrease in microbial activity or nutrient availability in sterile soils over time. To investigate this, the mineralization of 14C-phenanthrene was measured until it plateaued; subsequently, additional 14C-phenanthrene, catabolic inocula or nutrients were introduced and mineralization was measured for a further 10 d. Cell numbers were also measured together with 14C-uptake into microbial biomass. Freshly added 14C-phenanthrene was rapidly metabolised by the microorganisms. Neither the addition of a catabolic inoculum nor nutrients affected the extent of 14C-phenanthrene mineralization. Cell numbers remained constant over time, with only a small amount of the 14C-activity incorporated into the microbial biomass. This study indicated that the termination of mineralization was due to the removal of available phenanthrene and not decreasing cellular activity or cell death. The mineralization values also correlated with 14C-phenanthrene extractability using beta-cyclodextrin.

Bacteria↗
PubMed2005

Long-term fate of polychlorinated biphenyls and polycyclic aromatic hydrocarbons in an agricultural soil.

Laboratory studies are useful for understanding the behavior of persistent organic pollutants (POPs) in soil, although such investigations do not always relate directly to field conditions. Outdoor lysimeter studies may be used to overcome this problem. This work aimed to investigate the behavior of two polycyclic aromatic hydrocarbons (PAHs) (fluoranthene and benzo[a]pyrene) and two polychlorinated biphenyls (PCBs; congeners 28 and 52) in soil, using lysimeters established in 1990 atthe Agrosphere Institute (Forschungszentrum Julich GmbH, Germany). The two PAHs were in one lysimeter, and the PCBs were in a second lysimeter. Afurther aim of the study was to determine soil half-lives for each of the contaminants. The overall decline in PAH concentrations was considerably greater than forthe PCBs over the 152 month study. The PCBs exhibited greater chemical extractability than the PAHs and were demonstrated to have migrated through the soil column to a greater extent than the PAHs. Loss of PCBs from surface soil was not considered to have been congener specific for the two PCB congeners in this study. The two PAHs varied in their extents of total loss and movement through the soil column. Soil half-lives were determined as 10.9 y for [12C]PCB 28, 11.2 yr for [12C]PCB 52, 2.7 yr for benzoqpyrene, and 32 d (phase 1) to 38 yr (phase 2) for fluoranthene. These are shown to disagree with some previous estimates of POP half-lives in soil, suggesting that previous studies underestimated persistence by 10-fold or more.

Agriculture↗
PubMed2005

Formation and release of non-extractable 14C-Dicamba residues in soil under sterile and non-sterile regimes.

The role of native soil microorganisms in the formation and release of non-extractable (14)C-residues, previously treated with (14)C-Dicamba, was investigated to examine their significance to the longer-term environmental effects on non-extractable pesticide residues. A 90 d study compared the fate of Dicamba under sterile and non-sterile regimes. In addition, soils were aged for 30 d and repeatedly extracted with a 0.01 M CaCl(2) solution, to an extraction end point, to produce non-extractable residues. The extracted soil containing non-extractable residues was mixed with clean soil that had been freshly spiked with non-labeled Dicamba at 0.2 mg kg(-1) to increase the bulk volume of the soil and stimulate microbial activity. Sub-samples were then introduced into microcosms to compare the extent of microbially facilitated release and mineralisation with release rates in sterile microcosms. The results show that microorganisms play a significant role in the formation and release of non-extractable Dicamba residues. The release of (14)C-activity in sterile microcosms was linked to physical mixing of the extracted soil with field soil prior to the beginning of the incubations. The released (14)C-activity may be further mineralized, reincorporated into humus, or taken up by plants or other soil inhabiting biota.

Biodegradation, Environmental↗
PubMed2005

Influence of plants on the chemical extractability and biodegradability of 2,4-dichlorophenol in soil.

This study investigated the fate and behaviour of [UL-(14)C] 2,4-dichlorophenol (DCP) in planted (Lolium perenne L.) and unplanted soils over 57 days. Extractability of [UL-(14)C] 2,4-DCP associated activity was measured using calcium chloride (CaCl(2)), acetonitrile-water and dichloromethane (DCM) extractions. Biodegradability of [UL-(14)C] 2,4-DCP associated activity was assessed through measurement of (14)CO(2) production by a degrader inoculum (Burkholderia sp.). Although extractability and mineralisation of [UL-(14)C] 2,4-DCP associated activity decreased significantly in both planted and unplanted soils, plants appeared to enhance the sequestration process. After 57 days, in unplanted soil, 27% of the remaining [UL-(14)C] 2,4-DCP associated activity was mineralised by Burkholderia sp., and 13%, 48%, and 38% of (14)C-activity were extracted by CaCl(2), acetonitrile-water and DCM, respectively. However, after 57 days, in planted soils, only 10% of the [UL-(14)C] 2,4-DCP associated activity was available for mineralisation, whilst extractability was reduced to 2% by CaCl(2), 17% by acetonitrile-water and 11% by DCM. This may be due to the effect of plants on soil moisture conditions, which leads to modification of the soil structure and trapping of the compound. However, the influence of plants on soil biological and chemical properties may also play a role in the ageing process.

Biodegradation, Environmental↗
PubMed2005

Formation of non-extractable pesticide residues: observations on compound differences, measurement and regulatory issues.

Six major use pesticides (Atrazine, Dicamba, Isoproturon, Lindane, Paraquat and Trifluralin) with differing physico-chemical properties were evaluated for the significance of 'bound' or non extractable residue formation. Investigations were carried out in purpose-built microcosms where mineralization, volatilisation, 'soil water' extractable and organic solvent extractable residues could be quantified. Extractable residues were defined as those accessible by sequential extraction where the solvent used became increasingly non-polar. Dichloromethane was the 'harshest' solvent used at the end of the sequential extraction procedure. (14)C-labelled volatilised and (14)CO(2) fractions were trapped on exit from the microcosm. The pesticides were categorised into 3 classes based on their behaviour. (i) Type A (Atrazine, Lindane and Trifluralin) in which ring degradation was limited as was the formation of non-extractable residues; the remainder of the (14)C-activity was found in the extractable fraction. (ii) Type B (Dicamba and Isoproturon) in which approximately 25% of the (14)C-activity was mineralised and a large portion was found in the non-extractable fraction after 91 days. Finally, Type C (Paraquat) in which almost all of the (14)C-activity was quickly incorporated into the non-extractable fraction. The implications of the data are discussed, with respect to the variability and significance of regulatory aspects of non-extractable residues.

Atrazine↗
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

A biomarker model of sublethal genotoxicity (DNA single-strand breaks and adducts) using the sentinel organism Aporrectodea longa in spiked soil.

There is a need to develop risk biomarkers during the remediation of contaminated land. We employed the earthworm, Aporrectodea longa (Ude), to determine whether genotoxicity measures could be applied to this organism's intestinal tissues. Earthworms were added, for 24h or 7 days, to soil samples spiked with benzo[a]pyrene (B[a]P) and/or lindane. After exposure, intestinal tissues (crop/gizzard or intestine) were removed prior to the measurement in disaggregated cells of DNA single-strand breaks (SSBs) by the alkaline comet assay. Damage was quantified by comet tail length (CTL, microm). B[a]P 24-h exposure induced dose-related increases (P<0.0001) in SSBs. Earthworm intestine was significantly (P<0.0001) more susceptible than crop/gizzard to B[a]P and/or lindane. However, both tissues appeared to acquire resistance following 7-day exposure. B[a]P-DNA adducts, measured by (32)P-postlabelling, showed a two-adduct-spot pattern. This preliminary investigation suggests that earthworm tissues may be incorporated into genotoxicity assays to facilitate hazard identification within terrestrial ecosystems.

Animals↗
PubMed2005

Prediction of polycyclic aromatic hydrocarbon biodegradation in contaminated soils using an aqueous hydroxypropyl-beta-cyclodextrin extraction technique.

This study investigated the use of an aqueous hydroxypropyl-beta-cyclodextrin (HPCD) shake extraction to predict the degree of microbial degradation of polycyclic aromatic hydrocarbons (PAHs) in soils. Three different aged PAH-contaminated soils were studied: A soil from a former coke works (CW) and two artificially contaminated soils (AC1 and AC2). First, the catabolic activity of the indigenous soil microflora was assessed with 14C-respirometry, using a range of 14C-labeled aromatic compounds. Extensive mineralization of several compounds occurred in the CW and the AC2 soils, suggesting that both soils contained catabolically active microorganisms. No significant mineralization occurred in the AC1 soil, implying that either it did not contain an indigenous PAH-degrading microbial population or that degradation, but not mineralization, occurred. The soils then were subjected to three sets of analyses: dichloromethane (DCM) soxhlet extraction, six-week biodegradation assay followed by DCM extraction, and extraction with HPCD followed by DCM extraction. A general decrease in PAHs present in the soils occurred after the biodegradation assay. In the CW and the AC1 soils, strong correlations were observed between the amount of PAHs biodegraded and the fraction of PAHs removed from the soils using the HPCD extraction. However, the AC2 soil showed a more modest correlation between the biodegradable fraction and the HPCD extractable fraction, with the HPCD extraction slightly underestimating the extent of PAH biodegradation. The results of this study indicated that an aqueous HPCD extraction may be a useful tool in assessing the microbial availability of aged contaminant mixtures in soils, although further validation is required.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2005

Effect of cyclodextrin and transformer oil amendments on the chemical extractability of aged [14C]polychlorinated biphenyl and [14C]polycyclic aromatic hydrocarbon residues in soil.

Sequestration of hydrophobic organic contaminants (HOCs) in soils limits chemical and biological availability. Concerns exist regarding the long-term stability of sequestered contaminants in the environment, and stability needs to be demonstrated if bioavailability considerations are to be adopted into the risk assessment and remediation of contaminated land. The aim of the present study was to test the short-term influence of two organic amendments on the chemical extractability of HOC residues that had been present in soils for more than 12 years. The amendments investigated were cyclodextrin and transformer oil (a light, nonaqueous phase liquid [LNAPL]). The contaminants investigated were fluoranthene and benzo[a]pyrene in one soil and the polychlorinated biphenyls (PCBs) 28 and 52 in a second soil. The addition of cyclodextrin to the soils did not result in a significant increase in chemical extractability of the residues after a 36-d contact time. The addition of transformer oil resulted in an increase in chemical extractability of the PCBs after a 14-d soil-LNAPL contact time and a further increase after a 36-d contact time. The present study demonstrates that the chemical availability of aged HOCs in soil may be influenced by the presence of other chemicals and has implications for the long-term management of contaminated land.

Absorption↗
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↗
PubMed2004

Environmental health impacts: occurrence, exposure and significance, Lancaster University, UK, 9-10 September 2003.

Speakers: John Ashby (Syngenta CTL, UK), Peter A. Behnisch (Eurofins GfA, Germany), Paul L. Carmichael (Unilever Colworth, UK), Curtis C.Harris (National Cancer Institute, USA), Kevin C. Jones (Lancaster University, UK), Andreas Kortenkamp (School of Pharmacy, London, UK), Caroline J. Langdon (Reading University, UK), Anthony M. Lynch (GlaxoSmithKline, UK), Francis L. Martin (Lancaster University, UK), Trevor J. McMillan (Lancaster University, UK), David H. Phillips (Institute of Cancer Research, UK), Huw J. Ricketts (University of Cardiff, UK), Michael N. Routledge (University of Leeds, UK), J. Thomas Sanderson (Utrecht University, The Netherlands) and Kirk T. Semple (Lancaster University, UK) The effects of many environmental exposures to either single contaminants or to mixtures still remain to be properly assessed in ecotoxicological and human toxicological settings. Such assessments need to be carried out using relevant biological assays. On a mechanistic basis, future studies need to be able to extrapolate exposure to disease risk. It is envisaged that such an approach would lead to the development of appropriate strategies to either reduce exposures or to initiate preventative measures in susceptible individuals or populations. To mark the opening of a new Institute, the Lancaster Environmental Centre, an environmental health workshop was held over 2 days (9-10 September 2003) at Lancaster University, UK. The fate, behaviour and movement of chemicals in the environment, together with environmental exposures and human health, biomarkers of such exposures, hormone-like compounds and appropriate genetic toxicology methodologies, were discussed.

Animals↗