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Title: Attenuation of nitrate in the sub-surface environment
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1573, Representation ID: 552, Object ID: 2717
Nitrate is a widespread contaminant in groundwaters and surface waters. Nitrate is commonly thought of as behaving conservatively in the sub-surface environment but under certain circumstances it undergoes a microbially mediated transformation to nitrogen gas (denitrification). In the UK, evidence of denitrification is mostly limited to confined aquifers, where dissolved oxygen is depleted. The rates of reaction in these confined zones are slow compared to the timescale over which nitrate loads have increased in the last halfcentury. With the exception of a number of studies on riparian zones, no UK studies appear to cover attenuation of nitrate in shallow groundwater environments. Riparian zones, wetlands and hyporheic zones appear to be zones of effective, if variable, nitrate cycling, primarily because of high fluxes of organic carbon and saturated conditions near to, or within, the soil zone. Very few UK studies cover this topic but most international studies are thought to be broadly applicable to the UK. Hydrogeological conditions which promote shallow groundwater flow are key to determining the extent of attenuation within the riparian zone. If suitable conditions are present, the rate of biodegradation of nitrate in riparian zones is controlled by the availability and reactivity of organic carbon. Seasonal variation in nitrate attenuation depends on plant growth cycles, the depth of the water table, organic carbon inputs and temperature-controlled rates of plant uptake and denitrification activity.
Publisher: Environment Agency
Subject Keywords: Groundwater pollutionNitratesRiversPollutionCatchment basinsNitrogen cycleDenitrification
Extent: 108
Total file downloads: 34

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