Browsing by Author "Whelan, Michael J."

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    A tiered assessment of human health risks associated with exposure to persistent, mobile and toxic chemicals via drinking water
    (Elsevier, 2025-01-01) Whelan, Michael J.; Pemberton, Emma; Hughes, Christopher B.; Swansborough, Chesney; Goslan, Emma Harriet; Gouin, Todd; Bell, Victoria A.; Bird, E.; Bull, S.; Segal, L.; Cook, S. H.; Jephcote, Calvin; Fane, Sarah
    There is increasing interest in chemicals which are persistent, mobile and toxic (PMT), primarily to protect drinking water. We present a tiered assessment of drinking water exposure and associated human health risks for 22 PMT substances. Worst-case exposure via drinking water is assumed to occur when wastewater is discharged to rivers which are then abstracted for water supply. Screening-level exposures assume daily per capita emissions based on REACH tonnage estimates, with removal in wastewater treatment calculated using SimpleTreat and no riverine dilution. Removal in water treatment was estimated for each substance assuming either conventional or advanced treatment processes. Higher tier spatially-resolved exposures used a gridded routing model which transfers chemical through the landscape based on flow directions derived from a 1 km digital elevation model. Emission was assumed to be proportional to population and no in-stream degradation was assumed. Exposures were calculated for 296 locations containing drinking water treatment works (WTWs) under mean discharge and Q95 (discharge exceeded 95% of the time). At low tiers, risk characterisation ratios (RCRs) were < 1 for all substances, assuming realistic tonnage and conventional treatment. If drinking water is assumed to represent only 20 % of total chemical intake, total RCRs (RCRT) were > 1 for three substances under conventional treatment but were < 1 for all substances under advanced treatment. Highest exposure and RCRs were predicted in highly populated areas with low dilution. RCRT values were > 1 for tetrachloroethylene (highest RCR) at up to 18 % of WTW locations under Q95 conditions assuming conventional treatment. However, RCRT was <1 for all locations assuming advanced treatment. Actual exposures will depend on catchment characteristics, but the model usefully allows prioritising higher risk chemicals and WTWs. Overall, the substances evaluated are unlikely to currently pose health risks, provided an appropriate level of water treatment is employed.
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    An assessment of the risk to surface water ecosystems of groundwater P in the UK and Ireland
    (Elsevier , 2010-03-15T00:00:00Z) Holman, Ian P.; Howden, Nicholas J. K.; Bellamy, Patricia H.; Willby, N.; Whelan, Michael J.; Rivas Casado, Monica
    A good quantitative understanding of phosphorus (P) delivery is essential in the design of management strategies to prevent eutrophication of terrestrial freshwaters. Most research to date has focussed on surface and near-surface hydrological pathways, under the common assumption that little P leaches to groundwater. Here we present an analysis of national patterns of groundwater phosphate concentrations in England and Wales, Scotland, and the Republic of Ireland, which shows that many groundwater bodies have median P concentrations above ecologically significant thresholds for freshwaters. The potential risk to receptor ecosystems of high observed groundwater P concentrations will depend on (1) whether the observed groundwater P concentrations are above the natural background; (2) the influence of local hydrogeological settings (pathways) on the likelihood of significant P transfers to the receptor; (3) the sensitivity of the receptor to P; and, (4) the relative magnitude of P transfers from groundwater compared to other P sources. Our research suggests that, although there is often a high degree of uncertainty in many of these factors, groundwater has the potential to trigger and/or maintain eutrophication under certain scenarios: the assumption of groundwater contribution to river flows as a ubiquitous source of dilution for P-rich surface runoff must therefore be questioned. Given the regulatory importance of P concentrations in triggering ecological quality thresholds, there is an urgent need for detailed monitoring and research to characterise the extent and magnitude of different groundwater P sources, the likelihood for P transformation and/or storage along aquifer- hyporheic zone flow paths and to identify the subsequent risk to receptor ecosystems. (C) 2009 Elsevier B.V. All rights reserved.
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    The fate and effects of triclosan in soils amended with biosolids
    (Cranfield University, 2012-09) Butler, Emma; Whelan, Michael J.; Sakrabani, Ruben
    Many hydrophobic pollutants can be emitted to agricultural soils if sewage sludge is used as a fertiliser. The fate and effects of pollutants in such receiving environments are relatively poorly understood compared with our knowledge of chemical behaviour and impact in surface waters. One chemical of particular concern is triclosan because it has antimicrobial properties which could affect important soil functions. Triclosan is hydrophobic, which means it will sorb appreciably to organic solids and is not readily biodegradable. It is also used extensively in personal care products. These factors have prompted considerable attention in the literature with respect to its environmental profile. In recent years, this attention has shifted away from the water environment to terrestrial systems. This thesis bridges some of the knowledge gaps considering the fate (specifically mineralisation, primary degradation and the formation of bound residues) and the effects (to the soil function and phenotype) of triclosan in soils amended with biosolids. Cont/d.
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    Identifying adaptation options and constraints: the role of agronomist knowledge in catchment management strategy
    (Springer Science Business Media, 2014-01-31T00:00:00Z) Dolan, Tom; Howsam, Peter; Parsons, David J.; Whelan, Michael J.; Varga, Liz
    Water suppliers in parts of Europe currently face occasional Drinking Water Directive compliance challenges for a number of pesticide active substances including metal- dehyde, clopyralid and propyzamide. Water Framework Directive (WFD) Article 7 promotes a prevention-led (catchment management) approach to such issues. At the same time, European pesticide legislation is driving reduced active substance availability. In this context, embedding agronomic drivers of pesticide use into catchment management and regulatory decision making processes can help to ensure that water quality problems are addressed at source without imposition of disproportionate cost on either agriculture or potable water suppliers. In this study agronomist knowledge, perception and expectations of current and possible future pesticide use was assessed and the significance of this knowledge to other stakeholders involved with pesticide catchment management was evaluated. This was then used to provide insight into the possible impacts of active substance restrictions and associated adaptation options. For many arable crops, further restrictions on the range of pesticides available may cause increased use of alternatives (with potential for "pollution swapping"). However, in many cases alternatives are not available, too costly or lack a proven track record and other adaptation options may be selected which catchment managers need to be able to anticipate.
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    Modelling of pesticide exposure in ground and surface waters used for public water supply
    (Cranfield University, 2014-01) Pullan, Stephanie; Holman, Ian P.; Whelan, Michael J.
    Diffuse transfers of pesticides from agricultural land to ground and surface waters can lead to significant drinking water quality issues. This thesis describes the development and application of a parameter-efficient, numerical model to predict pesticide concentrations in raw water sources within an integrated hydrological framework. As such, it fills an unoccupied niche that exists in pesticide fate modelling for a computationally undemanding model that contains enough process complexity to be applicable in a wide range of catchments and hydrogeological settings in the UK and beyond. The model represents the key processes involved in pesticide fate (linear sorption and first-order degradation) and transport (surface runoff, lateral throughflow, drain flow, percolation to the unsaturated zone, calculated using a soil water balance) in the soil at a daily time step. Soil properties are derived from the national soil database for England and Wales and are used to define the boundary conditions at the interface between the subsoil and the unsaturated zone. This is the basis of the integrated hydrological framework which enables the application of the model to both surface water catchments and groundwater resources. The unsaturated zone model accounts for solute transport through two flow domains (accounting for fracture flow and intergranular matrix flow) in three hydrogeological settings (considering the presence and permeability of superficial deposits). The model was first applied to a small headwater sub-catchment in the upper Cherwell. Performance was good for drainflow predictions (Nash Sutcliffe Efficiency > 0.61) and performed better than the MACRO model and as well as the modified MACRO model. Surface water model performance was evaluated for eight pesticides in five different catchments. Performance was generally good for flow prediction (Nash Sutcliffe Efficiency > 0.59 and percentage bias below 10 %, in the validation period for all but two catchments). The 90th percentile measured concentration was captured by the model in 62 % of catchment-pesticide combinations. In theremaining cases predictions were within, at most, a factor of four of measured 90th percentile concentrations. The rank order of the frequency of pesticides detected over 0.1 μg L-1 was also predicted reasonably well (Spearman’s rank coefficient > 0.75; p < 0.05 in three catchments). Pesticide transport in the unsaturated zone model was explored at the point scale in three aquifers (chalk, limestone and sandstone). The results demonstrate that representing the unsaturated zone processes can have a major effect on the timing and magnitude of pesticide transfers to the water table. In comparison with the other catchment scale pesticide fate models that predict pesticide exposure at a daily time-step, the model developed stands out requiring only a small number of parameters for calibration and quick simulation times. The benefit of this is that the model can be used to predict pesticide exposure in multiple surface and groundwater resources relatively quickly which makes it a useful tool for water company risk assessment. The broad-scale approach to pesticide fate and transport modelling presented here can help to identify and prioritise pesticide monitoring strategies, to compare catchments in order to target catchment management and to highlight potential problems that could arise under different future scenarios.
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    Modelling Soil Bulk Density using Data-Mining and Expert Knowledge
    (Cranfield University, 2013-04) Taalab, Khaled Paul; Corstanje, Ronald; Whelan, Michael J.; Creamer, Rachel E.
    Data about the spatial variation of soil attributes is required to address a great number of environmental issues, such as improving water quality, flood mitigation, and determining the effects of the terrestrial carbon cycle. The need for a continuum of soils data is problematic, as it is only possible to observe soil attributes at a limited number of locations, beyond which, prediction is required. There is, however, disparity between the way in which much of the existing information about soil is recorded and the format in which the data is required. There are two primary methods of representing the variation in soil properties, as a set of distinct classes or as a continuum. The former is how the variation in soils has been recorded historically by the soil survey, whereas the latter is how soils data is typically required. One solution to this issue is to use a soil-landscape modelling approach which relates the soil to the wider landscape (including topography, land-use, geology and climatic conditions) using a statistical model. In this study, the soil-landscape modelling approach has been applied to the prediction of soil bulk density (Db). The original contribution to knowledge of the study is demonstrating that producing a continuous surface of Db using a soil-landscape modelling approach is that a viable alternative to the ‘classification’ approach which is most frequently used. The benefit of this method is shown in relation to the prediction of soil carbon stocks, which can be predicted more accurately and with less uncertainty. The second part of this study concerns the inclusion of expert knowledge within the soil-landscape modelling approach. The statistical modelling approaches used to predict Db are data driven, hence it is difficult to interpret the processes which the model represents. In this study, expert knowledge is used to predict Db within a Bayesian network modelling framework, which structures knowledge in terms of probability.This approach creates models which can be more easily interpreted and consequently facilitate knowledge discovery, it also provides a method for expert knowledge to be used as a proxy for empirical data. The contribution to knowledge of this section of the study is twofold, firstly, that Bayesian networks can be used as tools for data-mining to predict a continuous soil attribute such as Db and that in lieu of data, expert knowledge can be used to accurately predict landscape-scale trends in the variation of Db using a Bayesian modelling approach.
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    Multimedia fate of petroleum hydrocarbons in the soil: Oil matrix of constructed biopiles
    (Elsevier Science B.V., Amsterdam., 2010-12-31T00:00:00Z) Coulon, Frederic; Whelan, Michael J.; Paton, Graeme I.; Semple, Kirk T.; Villa, Raffaella; Pollard, Simon J. T.
    A dynamic multimedia fugacity model was used to evaluate the partitioning and fate of petroleum hydrocarbon fractions and aromatic indicator compounds within the soil: oil matrix of three biopiles. Each biopile was characterised by four compartments: air, water, soil solids and non-aqueous phase liquid (NAPL). Equilibrium partitioning in biopile A and B suggested that most fractions resided in the NAPL, with the exception of the aromatic fraction with an equivalent carbon number from 5 to 7 (EC5-7). In Biopile C, which had the highest soil organic carbon content (13%), the soil solids were the most important compartment for both light aliphatic fractions (EC5-6 and EC6-8) and aromatic fractions, excluding the EC16-21 and EC21-35. Our starting hypothesis was that hydrocarbons do not degrade within the NAPL. This was supported by the agreement between predicted and measured hydrocarbon concentrations in Biopile B when the degradation rate constant in NAPL was set to zero. In all scenarios, biodegradation in soil was predicted as the dominant removal process for all fractions, except for the aliphatic EC5-6 which was predominantly lost via volatilization. The absence of an explicit NAPL phase in the model yielded a similar prediction of total petroleum hydrocarbon (TPH) behaviour; however the predicted concentrations in the air and water phases were significantly increased with consequent changes in potential mobility. Further comparisons between predictions and measured data, particularly concentrations in the soil mobile phases, are required to ascertain the true value of including an explicit NAPL in models of this kind.
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    Towards a conceptual model of the impact zone ecology in rivers
    (Cranfield University, 2014-11) Roche, Nicola; Gill, Andrew B.; Whelan, Michael J.
    In many regions of the world, untreated wastewater is discharged directly into rivers containing sanitary determinands including ammonia, nitrite and organic matter which places a demand on dissolved oxygen in the water. The wastewater may also contain chemical ingredients of home and personal care products. When sewage treatment is lacking, often in developing regions, these sanitary determinands and down-the-drain chemicals may be present at high concentrations in surface waters which may adversely impact the ecological communities present downstream of the effluent outfall. Some studies have studied these ecological effects by sampling the taxa present at regular intervals downstream of an wastewater outfall, from which a common pattern in terms of macroinvertebrate species richness, dominance and diversity throughout the impact zone is evident. The aim of the project was to develop a conceptual model in order to predict the ecological composition downstream of an effluent outfall, as a result of multiple stressors’ concentration gradients. The model combines water quality data and toxicity data of the stressors on aquatic organisms, in the form of species sensitivity distributions (SSDs) to predict this impact. The model was based on selected stressors: ammonia, nitrite and dissolved oxygen which are present, in particular, in untreated wastewater; and two chemical ingredients used in home and personal care products which are washed down-the-drain. The model was applied to data from a field study on the South Elkhorn Creek in Kentucky, USA. Predicted effects on taxonomic composition were in line with field observations, although further enhancements to the model could incorporate more environmental realism. This was a useful step in the direction to creating a conceptual model of the impact zone ecology in rivers.
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    Water Framework Directive Article 7, The Drinking Water Directive and European Pesticide Regulation: impacts on diffuse pesticide pollution, potable water decision making and catchment management strategy
    (Cranfield University, 2013-10) Dolan, Tom; Parsons, David; Howsam, Peter; Whelan, Michael J.; Varga, Liz
    The European Water Framework Directive (WFD) promotes increased awareness of catchment processes and challenges the established dependence on a ‘treatment-led approach’ for the supply of European Drinking Water Directive (DWD) compliant potable water. In particular, WFD Article 7 promotes a ‘prevention-led approach’ to DWD compliance, based on pollution prevention at source to reduce investment in new treatment. In this context the challenge of preventing diffuse pesticide pollution from agricultural sources is significant because metaldehyde (a molluscide) and to a lesser extent the herbicide clopyralid are, despite current treatment, causing DWD non compliance for drinking water in a number of English catchments. Analysis presented here identifies that a successful transition from a ‘treatment-led’ to a ‘prevention-led’ approach will require collective action from, and shared mutual understanding between, a number of stakeholder groups. However, each of these groups has a unique perspective on WFD Article 7 and other elements of the currently uncoordinated legal and voluntary framework for diffuse pesticide pollution prevention. A toolbox of intervention options and a set of criteria to evaluate current catchment management actions are proposed to help the WFD competent authority facilitate WFD Article 7 compliance.Water suppliers need to improve their understanding of the reasons for pesticide use. Through consultation with pesticide agronomists, important drivers of pesticide use, a hierarchy of adaptation options available if a particular pesticide is restricted and key messages for catchment managers and regulators were identified. Based on this foundation a classification system to inform and prioritise water sector decision making for investment in catchment management was developed.Additionally, analysis presented here demonstrates that the DWD standard for pesticides, which determines the level of catchment management required for WFD Article 7 compliance, is not itself consistent with European environmental policy principles, particularly the precautionary principle, and needs to be reviewed.