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General A pollutant load is a mass, or weight, of a chemical
entering or leaving an area, and is the product of the volume of
water that the chemical is using as its transport medium and the
concentration of the chemical in the water. The measurement of load has the advantage over concentration in that it can better assist the identification and help set priorities the source of contaminants. Whereas concentration data can help in identifying degrading processes on the environment that are independent of flow. Protocol Automatic samplers are installed at either natural or constructed portions of waterways where samples can be drawn from the creek and the depth of water can be determined. Depth is commonly determined by back pressure on a nitrogen bubbler. The cross sectional area for a large range of storm events is also required to calculate flow. If a natural section of waterway can not be found a “V” notch weir can be constructed which can be calibrated (cross sectional area for flow) to the range of storm events likely to be encountered. The tube to extract the water sample is then located behind the weir and attached to the autosampler which is located securely on the bank above any storm event. Autosamplers can be of two types, or some combination. They either take samples for later laboratory analysis or analyse samples in situ for some common parameters such as Dissolved Oxygen, pH, Temperature, Salinity etc. It is recommended that at least 10 storm events of varying intensity are sampled to determine the mean loads in wet weather. Between 5 and 10 dry weather samplings should also be included to complete the estimation of load through time. Autosamplers can be programmed to take samples at discrete points of the hydrograph during a storm event or they can take a composite sample which integrates the whole storm. Analytes; Faecal coliforms (refrigerated sampler), Ammonical nitrogen, Total nitrogen, Oxidised nitrogen, Total phosphorus, Filterable phosphorus and Suspended solids References: Cost Purchase Autosampler (one set) = $15,000 By contractor = Approx. $50,000 for installation and one years operation, including 5 dry and 5 wet weather sampling events Case Studies EPA Load license Murrumbidgee River Person Contact Peter Coad Advanced Reference Load Monitoring of Lake Okeechobee, Florida Chesapeak Bay River Input Monitoring Program |
Internal Links Constructed Wetland Monitoring Desktop Monitoring Using Satellite Data Fish Monitoring for Water Quality Gross Pollutant Trap Monitoring |
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