Modelling metaldehyde in catchments: a River Thames case-study

Environmental Science: Processes & Impacts

Being able to effectively monitor the molluscicide metaldehyde in river catchments is now of major importance in the UK.

Water Science and Technology, 1998

River water quality models are used extensively in research as well as in the design and assessment of water quality management measures. The application of mathematical models for that purpose dates back to the initial studies of oxygen depletion due to organic waste pollution. Since then, models have been constantly refined and updated to meet new and emerging problems of surface water pollution, such as eutrophication, acute and chronic toxicity, etc. In order to handle the complex interactions caused by the increased influence of human activities in rivers it is today mandatory to couple river water quality models with models describing emissions from the drainage and sewerage system (such as the IAWQ Activated Sludge model No.1). In this paper-which is the first of a three-part series by the IAWQ Task Group on River Water Quality Modellingthe state of the art is summarized with the above aim in mind. Special attention is given here to the modelling of conversion processes but also the methods and tools to work with the models, i.e. parameter estimation, measurement campaign design, and simulation software, are discussed.

EGS - AGU - EUG Joint Assembly, 2003

The object of the presented study is to estimate the emissions of seven heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn) into the river systems of the federal state Baden-Wuerttemberg (Germany). The estimation is accomplished with the help of the model MONERIS (Behrendt et al., 2000) which was developed to calculate the input of nutrients into river systems. For an application on heavy metal emissions the model MONERIS has to be upgraded. In addition to a basic module heavy metal typical transport processes and specific pathways are integrated in the MONERIS framework. For substance and pathway specific data an extensive data inquiry has been accomplished. The input data is regionalised with the help of a Geographical Information System (GIS). For verification of the results the estimated total emissions diminished by the loss of heavy metals due to retention processes within the river systems are compared with the heavy metal load measured at monitoring stations. Today's emissions of heavy metals into the river systems of Baden-Wuerttemberg are dominated by the input from diffuse sources, e.g. paved urban areas, erosion and inflow of groundwater (Fuchs et al., 2002). For different types of heavy metals different sources and pathways play an important role.

Abstract The regulatory requirements imposed by the Habitats Directive (EU 93/43/EEC) require the Environment Agency for England and Wales (EA) to review consented discharges and determine whether they are compliant with Environmental Quality Standards (EQS). Since the EQS are annual averages, model predictions, and sample comparisons, should be made on an annual average basis. Advection and dispersion of metal contaminants in the Severn Estuary were computed using a coupled 1-D and 2-D hydrodynamic-water quality model. The external inputs of dissolved copper, arsenic, mercury and chromium to the model were from 66 industrial discharges and sewage treatment works and 30 rivers. The annual average predicted concentrations were compared with the annual average dissolved metal concentrations from the 2004 and 2005 monitoring programme, and any discrepancy used to identify the role of additional processes, mainly involving the sediments. This ability to separate anthropogenic inputs from internal estuarine processes contributes to a better understanding of the functioning of the estuary and hence an improved management capability. The paper discusses the approach in designing scenarios and characterising uncertainty, when decision-making in the regulatory context.

Ecological Modelling, 2014

The modelling of trace metals (TM) in rivers is highly dependent on hydrodynamics, the transport of suspended particulate matter (SPM) and the partition between dissolved and particulate phases. A mechanistic, dynamic and distributed model is proposed that describes the fate of trace metals in rivers with respect to hydrodynamics, river morphology, erosion-sedimentation processes and sorptiondesorption processes in order to identify the most meaningful parameters and processes involved at the reach scale of a large river. The hydraulic model is based on the 1-D Saint Venant equation integrating real transects to incorporate the river's morphology. The transport model of dissolved species and suspended sediments is based on advection-dispersion equations and is coupled to the one-dimensional transport with inflow and storage (OTIS) model, which takes transient storage zones into account. The erosion and sedimentation model uses Partheniades equations. Finally, the transfer of trace metals is simulated using two parameters, namely the partition coefficient (Kd) and the concentration of TM in the eroded material. The model was tested on the middle course of the Garonne River, southwest France, over an 80 km section under two contrasting hydrological conditions (80 m 3 s À1 and 800 m 3 s À1 ) based on measurements (hydrology, suspended sediments, particulate and dissolved metals fractions) taken at 13 sampling stations and tributaries. The hydrodynamic model was calibrated with discharge data for the hydraulic model, tracer experiments for the dissolved transport model and SPM data for the erosion-sedimentation model. The TM model was tested on two trace metals: arsenic and lead. Arsenic was chosen for its large dissolved fraction, while lead was chosen for its very important particulate fraction, thus providing contrasting elements. The modelling of TM requires all four processes to be simulated simultaneously. The presented model requires the calibration of ten parameters divided in four submodels during two hydrological conditions (low and high flow). All parameters could be explained by the physical properties of the case study, suggesting that the model could be applied to other case studies. The strategy of using different datasets under different hydrological conditions highlights: (a) the importance of transient storage in the study case, (b) a detailed description of the erosion and sedimentation processes of SPM, and (c) the importance of TM eroded from the sediment as a secondary delayed source for surface water.

Water Science and Technology, 1998

This paper is the third of a three-part series summarizing the background to and objectives of the activity of the IAWQ Task Group on River Water Quality Modelling (RWQM). On the basis of the two other papers and a comparison between the best known state of the art river model, QUAL2, and the IAWQ Activated Sludge Model (ASM) No. 1, the Task Group proposes to develop improved conversion models for inclusion in a river water quality model. The model should describe the cycling of oxygen, nitrogen, and phosphorus in both water and sediment, and should be compatible with the ASM to support the development of integrated emission reduction strategies. The model should be particularly well suited to handle problems characterized by significant temporal and spatial influences (e.g. CSOs and NPSs). It should serve for research, education, improved communication, knowledge transfer, regulatory applications such as catchment planning, and improved data collection. Anticipated results of the Task Group effort include (i) standardized conversion sub-models; (ii) a decision support tool to guide model construction and usage; and (iii) case study applications. The model development, which is not intended to result in a software product, is intended to be an open-ended and flexible process to encourage the participation of interested professionals.

Hydrobiologia, 1991

Water, 2011

This paper provides data from two years of monitoring of the chemical quality of rivers and streams in North West England from the clean headwaters to polluted rivers just above the tidal reach and covers 26 sites including the Ribble, Wyre and the tributary rivers of the Calder and Douglas. Across the basins that include areas of rural, urban and industrial typologies, data is presented for three of the priority substances in the Water Framework Directive i.e., nickel (Ni), cadmium (Cd), and lead (Pb). Average concentrations are low and well below the Environmental Quality Standards values for all three of these substances. Cadmium and Pb appear in approximately equal proportions in the dissolved (<0.45 µm) and in the acid available particulate fractions (>0.45 µm) whilst Ni occurs predominantly in the dissolved form (92%). Regional inputs of these metals arise mostly from diffuse sources as the storm-flow concentrations are generally greater than at base-flow condition. Greater concentrations of Ni are transported at the headwaters and smaller tributary sites under storm flow condition than for the main stream of the Ribble. For Ni, amounts increase as the river proceeds from its headwaters down towards the Ribble and Wyre estuaries, whilst Cd and Pb show consistent values throughout the catchment. There is annual cycling of dissolved concentrations of Cd, Pb and Ni for the clean headwater streams that gives maxima during the latter half of the year when the river flow is greater. For the impacted sites the pattern is less distinct or absent. Our estimates

Geology, 2003

Heavy-metal contamination of sediments within river systems is a major environmental problem around the world. Deposited as a by-product of metal mining, contaminated sediments are persistent and widespread, frequently affecting large areas of floodplains, which makes precise assessments of contamination levels and patterns difficult. This paper describes findings from a new, generic, catchment sediment model called TRACER, which uses historical mining records to accurately predict present-day and future levels and patterns of contamination. This model provides detailed views of the extent of contamination and demonstrates how contaminated sediments form into ''hot spots,'' which in turn become secondary sources of pollution. The exceptional longevity of the contamination is also revealed; Ͼ70% of the deposited contaminants remain within the river system for Ͼ200 yr after mine closure. Simulations of the impact of future climate changes in northern England show that increased flood magnitudes are likely to decrease surface contamination through dilution by cleaner sediment from hillslopes unaffected by mining activity.

Polish Journal of Environmental Studies

Environmental flow is required to ensure the ecosystem, as well as the survival of aquatic life in the urban river [1]. However, rivers in urban areas around the world continued to be polluted by untreated wastewater from industrial and domestic sources. As a result, the degree of physicochemical parameters, especially the concentration of heavy metals (HMs) in urban rivers, has reached alarming levels [2, 3].