Suchergebnisse

Acid rain, photochemistry, long-range transport of pollutants, greenhouse gas emissions and aerosols have dominated tropospheric air pollution for the last 30 years of the 20th century. At the start of the 21st century, acid rain is subject to planned improvement in Europe and North America, but is still a growing problem in Asia. Tropospheric ozone is understood much better, but the problem is still with us, and desirable levels are difficult to achieve over continental Europe. The heterogeneous chemistry that is responsible for ozone depletion in the stratosphere is now reasonably clear, but there is on-going interest in the sources and sinks of CFC (chlorofluorocarbon) replacements in the troposphere. There is also increasing interest in indoor air quality, and the origin and health implications of atmospheric particles. Perhaps most important on a global perspective, intensive research has not yet determined the relationship between greenhouse gases, aerosols and surface temperature. The climactic implications of these are now more urgent than ever. This book, the first in the Developments in Environmental Science series, consists of a collection of authoritative reviews and essays on the science and application of air pollution research at the start of this new century

The UK is one of several countries around the world that has enacted legislation to reduce its greenhouse gas emissions. In this study, we present top-down emissions of methane (CH 4 ) and nitrous oxide (N 2 O) for the UK and Ireland over the period August~2012 to August~2014. These emissions were inferred using measurements from a network of four sites around the two countries. We used a hierarchical Bayesian inverse framework to infer fluxes as well as a set of covariance parameters that describe uncertainties in the system. We inferred average UK total emissions of 2.09 (1.65–2.67) Tg yr −1 CH 4 and 0.101 (0.068–0.150) Tg yr −1 N 2 O and found our derived UK estimates to be generally lower than the a priori emissions, which consisted primarily of anthropogenic sources and with a smaller contribution from natural sources. We used sectoral distributions from the UK National Atmospheric Emissions Inventory (NAEI) to determine whether these discrepancies can be attributed to specific source sectors. Because of the distinct distributions of the two dominant CH 4 emissions sectors in the UK, agriculture and waste, we found that the inventory may be overestimated in agricultural CH 4 emissions. We found that annual mean N 2 O emissions were consistent with both the prior and the anthropogenic inventory but we derived a significant seasonal cycle in emissions. This seasonality is likely due to seasonality in fertilizer application and in environmental drivers such as temperature and rainfall, which are not reflected in the annual resolution inventory. Through the hierarchical Bayesian inverse framework, we quantified uncertainty covariance parameters and emphasized their importance for high-resolution emissions estimation. We inferred average model errors of approximately 20 and 0.4 ppb and correlation timescales of 1.0 (0.72–1.43) and 2.6 (1.9–3.9) days for CH 4 and N 2 O, respectively. These errors are a combination of transport model errors as well as errors due to unresolved emissions processes in the inventory. We found the largest CH 4 errors at the Tacolneston station in eastern England, which may be due to sporadic emissions from landfills and offshore gas in the North Sea.