The Impact of Pesticides - Academy Publish

Accumulated ExceedanceIt is useful to express surface water pesticide loads in a single environmental qualityindicator that takes in all the compounds detected at a given location. For thispurpose the indicator Accumulated Exceedance (AE) is used, defined as follows:AENRCnx1concx NRC NRCxxwhere conc x is the measured concentration of compound x, n the total number ofcompounds and NRC x the negligible risk level of compound x (= MPC/100).For each monitoring site and each monitoring day the AE is calculated asindicated, summing the results for all the compounds for which monitoring data areavailable and then aggregating the results over a whole year. If fewer than tencompounds are measured in a particular sample, however, that sample is notincluded in the analysis. If the compound is present at a concentration below orequal to the NRC, it follows from the formula that the compound’s contribution tothe sum is zero. For compounds with a measured value below the limit of report(LOR) the concentration is taken to be zero, even though the actual concentrationmay have exceeded the NRC, and in some cases even the MPC. This proceduremeans that measurements reported as