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The article presents a study on the pollutant retardation potential of permeable riverbed sediments in catchments with significant groundwater-surface water (GW-SW) interaction. It states that the fraction of organic carbon and cation exchange capacity of fluvial sediments in various geomorphologic environments have been quantified, and sediments in chosen reaches of the rivers Tern and Leith in Great Britain, from the underlying Permian sandstone aquifers and from along the length of the rivers Severn and Eden, have been evaluated. It mentions that statistical analyses demonstrate significant variation in the geochemistry and pollutant retardation potential of sediments from different geomorpholgic features, and between upland and lowland rivers.

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Urban areas can impose significant loads of nitrogen, as ammonium or nitrate, onto the underlying groundwater. There are many sources of nitrogen pollution, including diffuse sources (parks and gardens), intense point sources (industrial chemical spills), and multi-point sources (leaking sewers). Data on the loadings associated with the various sources are scarce, although an estimate of the overall load is available for Nottingham. For other cities, a total load could be estimated by factoring the Nottingham result, or by considering each component of the load separately. Both approaches are described, and the integrated method is recommended for its simplicity. [ABSTRACT FROM AUTHOR]

Groundwater is an important and valuable resource for water supply to cities. In order to make full and wise use of the asset value, a clear understanding of the quantities and sources of urban groundwater recharge is needed. The water supply and disposal network is often animportant source of recharge to urban groundwater through leakage from water mains and sewers. An approach to establishing the spatial and temporal amounts of the three urban recharge sources (precipitation, mains and sewers) is developed and illustrated using the Nottingham(UK) urban aquifer. A calibrated groundwater flow model is supplemented by calibrated solute balances for three conservative species (Cl,SO4 and total N), thus providing four lines of evidence to use in the recharge estimation. Nottingham is located on a Triassicsandstone aquifer with average precipitation of 700 mm/year. Using the models, current urban recharge is estimated to be 211 mm/year, of which 138 mm/year (40%) is from mains leakage and 10 mm/year (100%) is from sewer leakage. The wide confidence intervals result from the scarcity of historical field data and the long turnover time in this high volume aquifer, and should be significantly lower for many other aquifer systems. [ABSTRACT FROM AUTHOR]