Paul Kay

The sorption and transport of a sulphonamide antibiotic in soil systems

Veterinary medicines are administered to animals to treat disease and protect their health. After administration, the substances can be metabolised and a mixture of the parent compound and metabolites may be excreted in the urine and faeces. For animals on pasture, the excreta will be released directly to soil whereas for intensively reared animals, the main route of entry will be through slurry and manure spreading. Whilst the behaviour of other classes of substance (e.g. pesticides and nutrients) that are applied to soil is well understood, limited information is available on the transport and fate of veterinary medicines applied to soils. Laboratory and field studies were, therefore, performed to investigate the sorption behaviour of the sulfonamide antibiotic, sulfachloropyridazine, in soil and to assess the potential for sulfachloropyridazine to move from soil to surface waters and groundwaters. Sorption coefficients (K(D)) for the compound in soil and soil/slurry mixtures were low (ranging from 0.9 to 1.8 l kg(-1)) and indicated that the substance would be highly mobile. Field studies on a clay field supported these observations and demonstrated that, after application, the compound was rapidly transported to surface waters, concentrations of up to 590 microg l(-1) being observed in drainage waters. Leaching studies at a sandy site indicated that the substance had a low potential to leach to groundwaters, concentrations in the soil pore water being below or close to analytical detection limits. An assessment of currently available models for predicting concentrations of veterinary medicines entering surface waters indicated that for sulfachloropyridazine, the methods provide reasonable estimates, predicted concentrations being within a factor of two of the maximum measured concentrations. The approaches may not, however, be appropriate for use on highly hydrophobic substances or for predicting groundwater concentrations.

Global Synthesis and Critical Evaluation of Pharmaceutical Data Sets Collected from River Systems

Pharmaceuticals have emerged as a major group of environmental contaminants over the past decade but relatively little is known about their occurrence in freshwaters compared to other pollutants. We present a global-scale analysis of the presence of 203 pharmaceuticals across 41 countries and show that contamination is extensive due to widespread consumption and subsequent disposal to rivers. There are clear regional biases in current understanding with little work outside North America, Europe, and China, and no work within Africa. Within individual countries, research is biased around a small number of populated provinces/states and the majority of research effort has focused upon just 14 compounds. Most research has adopted sampling techniques that are unlikely to provide reliable and representative data. This analysis highlights locations where concentrations of antibiotics, cardiovascular drugs, painkillers, contrast media, and antiepileptic drugs have been recorded well above thresholds known to cause toxic effects in aquatic biota. Studies of pharmaceutical occurrence and effects need to be seen as a global research priority due to increasing consumption, particularly among societies with aging populations. Researchers in all fields of environmental management need to work together more effectively to identify high risk compounds, improve the reliability and coverage of future monitoring studies, and develop new mitigation measures.

Fate of veterinary antibiotics in a macroporous tile drained clay soil

The environment may be exposed to veterinary medicines administered to livestock through the application of organic fertilizers to land. For other groups of substances that are applied to agricultural land (e.g., pesticides), preferential flow in underdrained clay soils has been identified as an extremely important mechanism by which pollution of surface waters can occur. This study, therefore, was performed to investigate the fate of three antibiotics from the sulfonamide, tetracycline, and macrolide groups. Pig slurry was applied to a field in arable production in two consecutive years and the fate of the compounds was monitored in the soil and drainage water. Both sulfachloropyridazine and oxytetracycline were detected in soil at concentrations up to 365 and 1691 microg/kg, respectively. Subsequently, peak concentrations of the two substances in drainflow were 613.2 and 36.1 microg/L, although mass losses to the receiving water were less than 0.5%. In contrast, tylosin was not detected at all. These findings could be explained by the persistence and sorption characteristics of the antibiotics, while preferential flow via desiccation cracks and worm channels to the tile drains was found to be the most important route for translocation of the chemicals. Thus, when the soil was disced prior to slurry application, losses were reduced significantly. It is evident that processes governing pesticide fate also apply to veterinary antibiotics.

Impacts of anthropogenic activity on the ecology of class 1 integrons and integron-associated genes in the environment

The impact of human activity on the selection for antibiotic resistance in the environment is largely unknown, although considerable amounts of antibiotics are introduced through domestic wastewater and farm animal waste. Selection for resistance may occur by exposure to antibiotic residues or by co-selection for mobile genetic elements (MGEs) which carry genes of varying activity. Class 1 integrons are genetic elements that carry antibiotic and quaternary ammonium compound (QAC) resistance genes that confer resistance to detergents and biocides. This study aimed to investigate the prevalence and diversity of class 1 integron and integron-associated QAC resistance genes in bacteria associated with industrial waste, sewage sludge and pig slurry. We show that prevalence of class 1 integrons is higher in bacteria exposed to detergents and/or antibiotic residues, specifically in sewage sludge and pig slurry compared with agricultural soils to which these waste products are amended. We also show that QAC resistance genes are more prevalent in the presence of detergents. Studies of class 1 integron prevalence in sewage sludge amended soil showed measurable differences compared with controls. Insertion sequence elements were discovered in integrons from QAC contaminated sediment, acting as powerful promoters likely to upregulate cassette gene expression. On the basis of this data, >1 × 1019 bacteria carrying class 1 integrons enter the United Kingdom environment by disposal of sewage sludge each year.

Ultrasonic extraction of veterinary antibiotics from soils and pig slurry with SPE clean-up and LC-UV and fluorescence detection.

A simple and rapid analytical method is presented in which the three veterinary antibiotics oxytetracycline (OTC), sulfachloropyridazine (SCP) and tylosin (TYL) are simultaneously extracted and determined in four different soils. Extractions were carried out by a combination of ultrasonic agitation and vortex mixing using a mixture of methanol, EDTA and McIlvaine buffer at pH 7 as the extractant solution. The extracts were then cleaned-up by a tandem solid phase extraction (SPE) method using an Isolute SAX anion exchange cartridge to remove natural organic matter and an Oasis HLB polymeric cartridge to retain the study compounds. Analysis was by HPLC-UV with additional fluorescence detection for SCP. Recoveries were in the range 68-85% for SCP in all soil types, 58-75% for OTC in sandy soils, 27-51% for OTC in clay containing soils, 74-105% for TYL and 47-61% in a clay soil. OTC and SCP were also extracted from liquid pig manure using a mixture of EDTA and McIlvaine buffer at pH 7 with ultrasonic agitation and vortex mixing with SPE clean-up and HPLC-UV analysis. Recoveries were greater than 77% and 58% for OTC and SCP, respectively. Limits of detection were 18mugkg(-1) for OTC and SCP and 40mugkg(-1) for TYL in soils and 70mugL(-1) for OTC and 140mugL(-1) for SCP in pig slurry.

Prevalence of Sulfonamide Resistance Genes in Bacterial Isolates from Manured Agricultural Soils and Pig Slurry in the United Kingdom

ABSTRACT The prevalences of three sulfonamide resistance genes, sul1, sul2, and sul3 and sulfachloropyridazine (SCP) resistance were determined in bacteria isolated from manured agricultural clay soils and slurry samples in the United Kingdom over a 2-year period. Slurry from tylosin-fed pigs amended with SCP and oxytetracycline was used for manuring. Isolates positive for sul genes were further screened for the presence of class 1 and 2 integrons. Phenotypic resistance to SCP was significantly higher in isolates from pig slurry and postapplication soil than in those from preapplication soil. Of 531 isolates, 23% carried sul1, 18% sul2, and 9% sul3 only. Two percent of isolates contained all three sul genes. Class 1 and class 2 integrons were identified in 5% and 11.7%, respectively, of sul-positive isolates. In previous reports, sul1 was linked to class 1 integrons, but in this study only 8% of sul1-positive isolates carried the intI1 gene. Sulfonamide-resistant pathogens, including Shigella flexneri, Aerococcus spp., and Acinetobacter baumannii, were identified in slurry-amended soil and soil leachate, suggesting a potential environmental reservoir. Sulfonamide resistance in Psychrobacter, Enterococcus, and Bacillus spp. is reported for the first time, and this study also provides the first description of the genotypes sul1, sul2, and sul3 outside the Enterobacteriaceae and in the soil environment.

Effects of agricultural conditions on the leaching behaviour of veterinary antibiotics in soils

Antibiotics may be released to soils during the application of manure as fertiliser to land. The compounds may subsequently be transported to and contaminate groundwater and surface waters. This paper describes a series of lysimeter-based studies to explore the leaching behaviour of three veterinary antibiotics (sulfachloropyridazine, oxytetracycline and tylosin) under different conditions that could occur in the agricultural environment. The specific objectives were to: (1) explore the influence of slurry amendment and incorporation on leaching; (2) assess the effects of climate on leaching behaviour; and (3) evaluate the predictive capability of a leaching model used in the regulatory assessment of veterinary medicines. Sulfachloropyridazine was detected sporadically in leachate at concentrations up to 0.66 microg L(-1) under typical irrigation conditions and more frequently at concentrations up to 8.5 microg L(-1) under extreme irrigation conditions. Incorporation and timing of rainfall had no effect on leaching behaviour. Oxytetracycline and tylosin were not detected in any leachate samples. These differences in behaviour were explained by the sorption and persistence characteristics of the compounds. Comparison of the experimental measurements with simulations from the leaching model indicated that the model greatly underestimates the transport of antibiotics to groundwater which raises questions over the application of these models in the regulatory risk assessment process.

Integron Prevalence and Diversity in Manured Soil

ABSTRACT The levels of integron abundance and diversity in soil amended with pig slurry were studied. Real-time PCR illustrated a significant increase in class 1 integron prevalence after slurry application, with increased prevalence still evident at 10 months after application. Culture-dependent data revealed 10 genera, including putative human pathogens, carrying class 1 and 2 integrons.

Priority water research questions as determined by UK practitioners and policy makers

Several recent studies have emphasised the need for a more integrated process in which researchers, policy makers and practitioners interact to identify research priorities. This paper discusses such a process with respect to the UK water sector, detailing how questions were developed through inter-disciplinary collaboration using online questionnaires and a stakeholder workshop. The paper details the 94 key questions arising, and provides commentary on their scale and scope. Prioritization voting divided the nine research themes into three categories: (1) extreme events (primarily flooding), valuing freshwater services, and water supply, treatment and distribution [each >150/1109 votes]; (2) freshwater pollution and integrated catchment management [100-150 votes] and; (3) freshwater biodiversity, water industry governance, understanding and managing demand and communicating water research [50-100 votes]. The biggest demand was for research to improve understanding of intervention impacts in the water environment, while a need for improved understanding of basic processes was also clearly expressed, particularly with respect to impacts of pollution and aquatic ecosystems. Questions that addressed aspects of appraisal, particularly incorporation of ecological service values into decision making, were also strongly represented. The findings revealed that sustainability has entered the lexicon of the UK water sector, but much remains to be done to embed the concept operationally, with key sustainability issues such as resilience and interaction with related key sectors, such as energy and agriculture, relatively poorly addressed. However, the exercise also revealed that a necessary condition for sustainable development, effective communication between scientists, practitioners and policy makers, already appears to be relatively well established in the UK water sector.

Drain-blocking techniques on blanket peat: A framework for best practice

In recent years there has been a dramatic increase in artificial drain-blocking in world peatlands. The UK blanket peatlands have been severely drained over the past few decades but now drains are being blocked in an attempt to improve peatland environments. The drain-blocking has been a disparate process with limited knowledge transfer between organisations and within organisations operating in different geographic areas. Consequently, there has been no compilation of techniques used and their effectiveness. During this study thirty-two drain-blocked sites were surveyed and all the key stakeholders interviewed. Drain-blocking using peat turf was preferred by practitioners and was also the most cost-effective method. Peat turves were successful except on steep slopes, in areas of severe erosion, in very wet or very dry locations, or if the mineral substrate was exposed. A drain-blocking best practice guide is offered by this paper, providing information on the most suitable methods for blocking peatland drains under different circumstances. Additional considerations are provided for practitioners to ensure peatland drain-blocking is as successful as possible.