Biomedical subjects

Philip M Haygarth

Publications and source records attributed to Philip M Haygarth.

6 recordsLinked to original sources

PubMed2006

Differential E. coli die-off patterns associated with agricultural matrices.

The investigation of fecal bacterial die-off in various agricultural and catchment related matrices remains important because of the growing concern over pathogens in agricultural environments and watercourses. The aim of this research was to investigate the die-off of Escherichia coli within cattle manure (both slurry [liquid mix of excrement and urine produced by housed livestock] and feces), soil, and runoff water and to determine if cell numbers would be influenced by the presence of cattle manure within soil and runoff water. E. coli survived better within feces than in slurry; cells within feces declined from 7.5 to 3.3 log CFU g(-1) in 76 days. Within slurry, cells fell from 8.5 log CFU g(-1) to below levels of detection by day 42. E. coli died off more quickly within manure and slurry than in soil amended with the same fecal material, and declined significantly faster within microcosms when introduced to the soil via sterile water rather than cattle manure. E. coli was found to decline more rapidly within wet (50% moisture w/w), rather than dry (25% moisture w/w), soil. Conversely, in runoff water, die-off of E. coli was increased in the presence of feces. Overall, E. coli die-off was most rapid in water incorporated with cattle manure > unincorporated cattle manure > soil incorporated with cattle manure. The derived die-off characteristics including half-life and decimal reduction times can now provide (i) input for predictive models and (ii) information upon which to consider mitigation strategies associated with both manure and land management.

Agriculture↗

PubMed2005

Spatial variability of soil phosphorus in relation to the topographic index and critical source areas: sampling for assessing risk to water quality.

A measure of soil P status in agricultural soils is generally required for assisting with prediction of potential P loss from agricultural catchments and assessing risk for water quality. The objectives of this paper are twofold: (i) investigating the soil P status, distribution, and variability, both spatially and with soil depth, of two different first-order catchments; and (ii) determining variation in soil P concentration in relation to catchment topography (quantified as the "topographic index") and critical source areas (CSAs). The soil P measurements showed large spatial variability, not only between fields and land uses, but also within individual fields and in part was thought to be strongly influenced by areas where cattle tended to congregate and areas where manure was most commonly spread. Topographic index alone was not related to the distribution of soil P, and does not seem to provide an adequate indicator for CSAs in the study catchments. However, CSAs may be used in conjunction with soil P data for help in determining a more "effective" catchment soil P status. The difficulties in defining CSAs a priori, particularly for modeling and prediction purposes, however, suggest that other more "integrated" measures of catchment soil P status, such as baseflow P concentrations or streambed sediment P concentrations, might be more useful. Since observed soil P distribution is variable and is also difficult to relate to nationally available soil P data, any assessment of soil P status for determining risk of P loss is uncertain and problematic, given other catchment physicochemical characteristics and the sampling strategy employed.

Databases, Factual↗

PubMed2005

Transfer of Escherichia coli to water from drained and undrained grassland after grazing.

The aim of this study was to determine the load of Escherichia coli transferred via drainage waters from drained and undrained pasture following a grazing period. Higher concentrations (ranging between 10(4) and 10(3) colony forming units [CFU] g(-1)) of E. coli persisted in soil for up to 60 d beyond the point where cattle were removed from the plots, but these eventually declined in the early months of spring to concentrations less than 10(2) CFU g(-1). The decline reflects the combined effect of cell depletion from the soil store through both wash-out and die-off of E. coli. No difference (P > 0.05) was observed in E. coli loads exported from drained and undrained plots. Similarly, no difference (P > 0.05) was observed in E. coli concentrations in drainage waters of mole drain flow and overland plus subsurface interflow. Intermittent periods of elevated discharge associated with storm events mobilized E. coli at higher concentrations (e.g., in excess of 400 CFU mL(-1)) than observed during low flow conditions (often <25 CFU mL(-1)). The combination of high discharge and cell concentrations resulted in the export of E. coli loads from drained and undrained plots exceeding 10(6) CFU L(-1) s(-1). The results highlight the potential for drained land to export E. coli loads comparable with those transferred from undrained pasture.

Agriculture↗

PubMed2005

Phosphatase activity in temperate pasture soils: Potential regulation of labile organic phosphorus turnover by phosphodiesterase activity.

Phosphatase enzymes regulate organic phosphorus (P) turnover in soil, but a clear understanding remains elusive. To investigate this, phosphomonoesterase and phosphodiesterase activities were determined by using para-nitrophenol (pNP) analogue substrates in a range of temperate pasture soils from England and Wales. Substrate-induced phosphatase activity ranged between 2.62 and 12.19 micromol pNP g-1 soil h-1 for phosphomonoesterase and between 0.25 and 2.24 micromol pNP g-1 soil h-1 for phosphodiesterase. Activities were correlated strongly with soil pH and labile organic P extracted in sodium bicarbonate, although the relationships differed markedly for the two enzymes. Acidic soils contained high phosphomonoesterase activity, low phosphodiesterase activity, and high concentrations of labile organic P, whereas the reverse was true in more neutral soils. As most of the organic P inputs to soil are phosphate diesters, it therefore seems likely that phosphodiesterase activity regulates labile organic P turnover in pasture soils. The low phosphodiesterase activity in acidic soils may be linked to the dominance of fungi or an effect of sorption on the enzyme. These results suggest that greater emphasis should be placed on understanding the role of phosphodiesterase activity in the cycling of soil organic P.

Agriculture↗

PubMed2005

Comparison of centrifugation and filtration techniques for the size fractionation of colloidal material in soil suspensions using sedimentation field-flow fractionation.

Sedimentation field-flow fractionation (SdFFF) with UV detection is used to systematically investigate the effect of traditional membrane filtration and centrifugation procedures on the isolation of specific size fractions from soil suspensions. Both procedures were used to isolate the nominal <0.45 and <0.2 microm fractions from a clay soil suspension. Results showed that the membrane filtration approach seriously underestimated the total mass of particulate matter present as compared to the centrifugation approach. This has serious implications forthe interpretation of results for "colloidal" and "soluble" fractions from soil suspensions and other environmental matrices obtained using the standard membrane approach. The results also show that sedimentation FFF has great potential as a robust and relatively mild technology for studying size distributions in the "colloidal" range for soil suspensions and other aquatic matrices.

Centrifugation↗

PubMed2002

Inositol phosphates in the environment.

The inositol phosphates are a group of organic phosphorus compounds found widely in the natural environment, but that represent the greatest gap in our understanding of the global phosphorus cycle. They exist as inositols in various states of phosphorylation (bound to between one and six phosphate groups) and isomeric forms (e.g. myo, D-chiro, scyllo, neo), although myo-inositol hexakisphosphate is by far the most prevalent form in nature. In terrestrial environments, inositol phosphates are principally derived from plants and accumulate in soils to become the dominant class of organic phosphorus compounds. Inositol phosphates are also present in large amounts in aquatic environments, where they may contribute to eutrophication. Despite the prevalence of inositol phosphates in the environment, their cycling, mobility and bioavailability are poorly understood. This is largely related to analytical difficulties associated with the extraction, separation and detection of inositol phosphates in environmental samples. This review summarizes the current knowledge of inositol phosphates in the environment and the analytical techniques currently available for their detection in environmental samples. Recent advances in technology, such as the development of suitable chromatographic and capillary electrophoresis separation techniques, should help to elucidate some of the more pertinent questions regarding inositol phosphates in the natural environment.

Agriculture↗