A review of source tracking techniques for fine sediment within a catchment

Excessive transport of fine sediment, and its associated pollutants, can cause detrimental impacts in aquatic environments. It is therefore important to perform accurate sediment source apportionment to identify hot spots of soil erosion. Various tracers have been adopted, often in combination, to identify sediment source type and its spatial origin; these include fallout radionuclides, geochemical tracers, mineral magnetic properties and bulk and compound-specific stable isotopes. In this review, the applicability of these techniques to particular settings and their advantages and limitations are reviewed. By synthesizing existing approaches, that make use of multiple tracers in combination with measured changes of channel geomorphological attributes, an integrated analysis of tracer profiles in deposited sediments in lakes and reservoirs can be made. Through a multi-scale approach for fine sediment tracking, temporal changes in soil erosion and sediment load can be reconstructed and the consequences of changing catchment practices evaluated. We recommend that long-term, as well as short-term, monitoring of riverine fine sediment and corresponding surface and subsurface sources at nested sites within a catchment are essential. Such monitoring will inform the development and validation of models for predicting dynamics of fine sediment transport as a function of hydro-climatic and geomorphological controls. We highlight that the need for monitoring is particularly important for hilly catchments with complex and changing land use. We recommend that research should be prioritized for sloping farmland-dominated catchments

A review of source tracking techniques for fine sediment within a catchment

Excessive transport of fine sediment, and its associated pollutants, can cause detrimental impacts in aquatic environments. It is therefore important to perform accurate sediment source apportionment to identify hot spots of soil erosion. Various tracers have been adopted, often in combination, to identify sediment source type and its spatial origin; these include fallout radionuclides, geochemical tracers, mineral magnetic properties and bulk and compound-specific stable isotopes. In this review, the applicability of these techniques to particular settings and their advantages and limitations are reviewed. By synthesizing existing approaches, that make use of multiple tracers in combination with measured changes of channel geomorphological attributes, an integrated analysis of tracer profiles in deposited sediments in lakes and reservoirs can be made. Through a multi-scale approach for fine sediment tracking, temporal changes in soil erosion and sediment load can be reconstructed and the consequences of changing catchment practices evaluated. We recommend that long-term, as well as short-term, monitoring of riverine fine sediment and corresponding surface and subsurface sources at nested sites within a catchment are essential. Such monitoring will inform the development and validation of models for predicting dynamics of fine sediment transport as a function of hydro-climatic and geomorphological controls. We highlight that the need for monitoring is particularly important for hilly catchments with complex and changing land use. We recommend that research should be prioritized for sloping farmland-dominated catchments

Leaching characteristics of CCA-treated wood waste: A UK study

CCA-treated wood is expected to increase in the UK waste stream over the next 20-50years. The potential pollution from this waste has been evaluated through two leaching studies, one based upon batch leaching tests and another based upon a series of lysimeter tests. The aim of the studies was to characterise the behaviour of arsenic (As), chromium (Cr) and copper (Cu) from this wood when applied to soil as a mulch. Results demonstrate that all three elements leach from CCA waste wood, occasionally in concentrations exceeding regulatory thresholds by two to three orders of magnitude. In the lysimeter study, wood mulch monofills and wood mulch in combination with soil were used to monitor the leaching of As, Cr and Cu. Peak concentrations for As, Cr and Cu were 1885μg/l, 1243μg/l and 1261μg/l, respectively. Freshly treated wood leached 11, 23 and 33 times more Cu, Cr and As, respectively than weathered wood. The toxic and mobile species of arsenic (As III, As V) were detected. Leaching in the CCA wood monofill was influenced by rainfall, with higher concentrations of metal(loid)s produced in lower intensity events. As and Cu were mobilised preferentially, with all metals exhibiting similar temporal trends. Retention of leached metal(loid)s was observed in lysimeters containing soil. Leaching processes appear to be favoured by the chipping process, diffusion and weathering. This study has shown that weathered waste wood mulch can cause significant pollution in soil water with potential impacts on both the environment and human health

Application of geophysical monitoring techniques as aids to probabilistic risk-based management of landfill sites

Increasingly stringent regulatory regimes, in conjunction with landfill development in environmentally sensitive locations and the large number of abandoned landfill sites, are significantly increasing the responsibilities of local authorities and environmental agencies. These responsibilities include the identification and/or monitoring of: locations of contaminated land; boundaries of waste sites; nature of the landfill content; location, extent, content and depth of closed landfill sites; leachate plumes escaping from both operational and closed sites and the performance of landfill liners. Probabilistic risk based modelling is a standard methodology for monitoring and managing the environmental impact of landfill sites. A critical problem in the implementation of probabilistic risk based modelling is the large uncertainty in the shallow geology, internal structure and leachate distribution of landfills caused by the severe lack of both surface and subsurface information from within and outside the landfill site. The utility of two non-invasive ground based geophysical monitoring techniques, ground penetrating radar and reflectance spectroscopy, as aids to characterising the three-dimensional structure and distribution of leachate within a landfill has been investigated. Strong correlations between red edge inflection position and chlorophyll and metal concentration have been demonstrated from grassland species affected by leachate contamination of the soil adjacent to the landfill study site. The results of this study have demonstrated how recent advances in equipment, techniques and software mean that field-based reflectance spectroscopy and Ground Penetrating Radar can now provide environmental scientists with cost-effective, rapid techniques to characterise landfill sites in three dimensions, aid landfill managers in positioning additional boreholes and field sampling surveys, and provide data as inputs to leachate migration modelling

Adapting to extreme events related to natural variability and climate change: the imperative of coupling technology with strong regulation and governance

In recent years there has been an increase in extreme events related to natural variability (such as earthquakes, tsunamis and hurricanes) and climate change (such as flooding and more extreme weather).1 Developing innovative technologies is crucial in making society more resilient to such events. However, little emphasis has been placed on the role of human decision-making in maximizing the positive impacts of technological developments. This is exacerbated by the lack of appropriate adaptation options and the privatization of existing infrastructure, which can leave people exposed to increasing risk. This work examines the need for more robust government regulation and legislation to complement developments and innovations in technology in order to protect communities against such extreme events