Development of nitrate profiles database

[摘要] The Predatory Bird Monitoring Scheme (PBMS) covers a long-term monitoring programme that examines the levels of pollutants in avian wildlife species in Britain. It was instrumental in securing the phased withdrawals of the permitted uses of organochlorine insecticides and has since provided a measure of the effectiveness of regulatory bans in reducing the exposure of wildlife. The PBMS has expanded over the years and currently monitors carcasses and/or eggs of various (terrestrial, freshwater and marine) predatory birds for organochlorine (OC) pesticides and their metabolites, polychlorinated biphenyls (PCBs), mercury and second-generation rodenticides (carcasses only). Since 1974, the PBMS has been the subject of a series of contracts (known as the Wildlife & Pollution contracts) from the Nature Conservancy Council, as was, and subsequently from the Joint Nature Conservation Committee (JNCC). This enables the JNCC and country agencies to monitor trends and advise on the effectiveness of measures to restrict the use and entry into the environment of some of these compounds. The concentrations of organochlorine pesticides in many predatory bird species have declined to levels below those likely to have toxic effects. As a result, concerns about the environmental hazards posed by these pesticides have, at least in part, been superseded by those posed by new groups of chemicals. In the last review of the work of the PBMS (Shore et al. 2002a), a number of possible new activities that could be incorporated into the PBMS were specified. Any such refocusing of the PBMS within existing resources would require revision of the current sampling intensity of organochlorine pesticides in order to free resources for new monitoring. The first objective of the current report was to assess the implications of reducing sampling intensity on the ability to detect long-term trends in the extent of wildlife contamination. This is described in Section 3. The other objectives of the current report were to consider in greater detail some of the potential activities that had been outlined in the original review. These were specifically to: explore whether monitoring for polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) could be incorporated into the PBMS (Section 4); describe how the link between environmental residue data and toxicity could be improved for PCBs (Section 5); demonstrate the ways in which the PBMS data can be used to identify hotspots of contamination and so provide information on potential sources (Section 6); examine the frequency with which unknown compounds occur in predatory birds and describe a strategy by which they might be identified (Section 7). Statistical analyses of the trends in contaminants in Eurasian sparrowhawks Accipiter nisus, merlins Falco columbarius and barn owls Tyto alba suggest that such studies require annual sampling for probably a minimum of ten years to detect long-term changes. The sensitivity with which trends are likely to be detected is reduced if sampling is on a biennial or triennial basis or carried out for a shorter period. Implementation of new monitoring programmes designed to determine whether contaminant levels in birds are changing should therefore envisage a commitment of at least ten years. The data collected over this initial period can be used to determine whether there is evidence of any change, the power of the study to detect such change, and the likely impacts of subsequent changes in sampling frequency on ability to detect trends. Large-scale contaminant studies that are carried out over shorter periods of time or with lower sampling frequency are likely to have relatively low power and only reveal large changes. Analysis of PBDEs and PAHs by the PBMS is feasible. PBDEs could be monitored in both livers and eggs of samples currently collected under the PBMS. PAH analysis would be better restricted to eggs. The costs of incorporating these analyses within the PBMS could be met within current resourcing if the sampling strategy of the scheme is revised. Preliminary analysis of congener concentrations and associated Toxicity Equivalents Quotient (TEQ) values in sparrowhawk livers indicated that although there was some correspondence between total PCB concentrations and TEQ values, total PCB concentration was not necessarily a good predictor of TEQ. This is because the TEQ value is particularly influenced by the concentrations of the dioxin-like congeners (such as congeners 77 and 126) that have relatively high toxicity equivalency factor (TEF) values. Monitoring TEQ values as well as total PCB values in future would be worthwhile so that changes over time in PCB accumulation can be more clearly linked to likely toxicity. This could be done equally well for PCB monitoring in eggs as well as livers and may be more important when examining the eggs for some species, such as merlin and particularly white-tailed eagle Haliaeetus albicilla eggs, where PCB concentrations remain relatively high. The costs of doing this within the scheme would be relatively minor as all the congeners are determined simultaneously within the same analytical run and the only additional costs are relatively minor ones in terms of using extra standards and in data-handling and analysis. Preliminary analysis of unknown peaks on chromatograms of sparrowhawk livers has demonstrated that up to 40 unknown compounds occur in individual samples. Individuals that have high concentration of total PCBs also have the highest number of unknown compounds. The frequency with which each unknown compound, as identified by its retention time, occurred in birds was highly variable and ranged from 3.7% to 85.7%. On average, each compound occurred in 18?28% of birds. A strategy as to how to identify unknown compounds is outlined. If PBDEs and PAHs are to be incorporated into the monitoring of the PBMS, it is recommended that this is done in the first instance using the species and samples that are currently collected. Sampling would be maintained on an annual basis but analysis would be carried out on a triennial (or equivalent) basis. This would mean that the sensitivity with which long-term trends could be detected would lower than if analysis was carried out on all samples but this strategy would allow PBDEs and PAHs to be monitored and PCBs to be reported on a congener and TEQ basis. Samples not analysed immediately would be archived for future use in other studies or future monitoring should there be a requirement to increase the number of samples analysed. It is also recommended that mercury, lead and cadmium residues are monitored by the PBMS as the additional costs of doing so are minimal. Sampling and analysis for rodenticides should continue unchanged. Further investigation of unknown compounds in birds and identification of contaminant hotspots is also recommended. These studies would require additional, one-off, funding.

[发布机构] British Geological Survey

[学科分类] 地球科学(综合)