Worcester City - Worcestershire Regulatory Services

2.2 Comparison of Monitoring Results with AQObjectives2.2.1 Nitrogen DioxideDiffusion Tube Monitoring DataWorcester City CouncilMeasured concentrations at the 17 diffusion tube monitoring sites in 2011 arepresented in Table 2.2. Concentrations since 2006, at all sites where monitoring dataare available, are presented in Table 2.3.Data capture for a number of the diffusion tube sites was below 75%, and these datahave been annualised following guidance in LAQM.TG(09). Further details arepresented in Appendix A. The national bias adjustment factor has been applied to thediffusion tube data. Further details are provided in Appendix A.Exceedences of the annual mean objective were measured at seven sites during2011, four of which are outside of existing AQMAs.The sites measuring exceedences outside of the existing AQMAs are:• Castle Street• Sidbury• St Johns• Foregate StreetThe Castle Street diffusion tube has measured exceedences of the annual meanobjective since 2009. The closest relevant exposure is approximately 5m from themonitoring site. Using the fall off with distance calculator, an estimate of theconcentration at the façade of the closest property can be made. In 2011, theestimated concentration at the closest property is 32.7µg/m 3 . From May 2012, thistube has been relocated to the façade of 925 The Tything, where residentialexposure exists at first floor level.The Sidbury site is not representative of relevant exposure, as it is located in themiddle of the road. This tube will be relocated to more accurately represent relevantexposure. From May 2012, three new tubes have been deployed on London Roadwhere it meets Sidbury. Data will be reported in the 2013 Progress Report.The need for an AQMA at the St Johns site was identified in the 2010 DetailedAssessment, and an AQMA will be declared at this location pending the outcome ofthe decision to be taken by Worcester City Council, following the consultationregarding the declaration of a City Wide AQMA, in November 2012.LAQM USA 2012 8