Influence Of Local Sources Research Articles

Measurements of nitrogen dioxide concentrations at rural sites in the United Kingdom using diffusion tubes

Nitrogen dioxide concentrations have been measured at rural sites in the United Kingdom and have revealed a marked spatial variation. The annual mean NO 2 concentration varies from ∼ 1 μg Nm −3 in Northern Ireland to ∼ 7 μg Nm −3 in East Anglia. Though the temporal resolution of the diffusion tube method is limited by exposure periods of 2–4 weeks, it was possible to detect a marked seasonal variation in NO 2 concentration at all sites, with higher values in the winter than in the summer. This is in contrast to the small seasonal variation previously observed at sites in London. Sulphur dioxide concentrations were measured daily using a bubbler method and, if expressed in terms of mass of sulphur and nitrogen, the SO 2 and NO 2 annual mean concentrations were similar. This is in contrast to an S/N ratio of greater than 3 in total UK emissions of SO 2 and NO x. It seems likely that this difference is due to a combination of the different spatial distributions and heights of emissions of SO 2 and NO x, the influence of local sources of NO x, and the smaller S/N ratio in Continental European emissions.

Accumulation and distribution of biogenic and pollutant hydrocarbons, pcbs and ddt in tissues of western mediterranean fishes

Abstract Data on hydrocarbons, PCBs and total DDT in muscle, liver and gonads of Mullas barbatus. Trachurus trachurus, Merluccius merluccius, Engraulis enchrasicholus and Micromesistius poutassou collected along the Catalan Coast (NW Mediterrenean) are reported for the first time. The species and the collection sites—off Barcelona to the north (Palamos) and to the south (Ehro Delta)—were selected for the assessment of the effects of coastal pollutant sources on commercially valuable organisms. Mullus barbatus reflects the influence of local sources, and is therefore a useful bioindicator for organic pollutants. Despite some scattering of the results, concentrations are in general of the same order of magnitude for juvenile and adult specimens, although the pollutants considered exhibit different biological fates. Hydrocarbons are accumulated primarily in liver, whereas organochlorinated compounds are accumulated in gonads. Liver and muscle contents could reflect acute and chronic pollutants inputs respectively. The accumulation in muscle is more important for aromatic and chlorinated hydrocarbons than for the saturated ones, which are probably metabolized in the liver.

Objective analysis of air pollution monitoring network data; spatial interpolation and network density

To obtain meaningful interpretations of the results of fixed air pollution monitoring stations, quantitative information on the spatial representativity of these results is of crucial importance. On the basis of data of the Dutch Air Pollution Monitoring Network a study was undertaken to estimate the absolute and relative errors which are involved in extrapolating the results beyond the actual spatial argument of measurement. In the first place, three interpolation techniques, optimum interpolation, eigenvector interpolation and so called distance-density interpolation, were compared for SO 2, NO, NO 2 and O 3. The differences between the results of these techniques proved to be small. It was further concluded that the interpolation errors and the associated persistence in space and time, as given by mutual correlations, should be specified with respect to pure space- or space-time variability. In the second place, the interpolation errors were generalized to other network densities on the basis of the optimum interpolation scheme and empirical observations. From the resulting relation between interpolation error and network density it was concluded that the SO 2-network of 108 stations over the measurement area of 150 × 220 km 2 results in relative errors of 20 %, small enough to detect mesoscale transports downwind of major source areas. The effect of sampling error, i.e., the small scale influences of local sources combined with the effect of measurement error, appeared to be of overriding importance in the efficiency of reconstruction of pollutant concentration fields at a given confidence level from monitoring network data.