Reductions in sulfur pollution in the Pearl River Delta region, China: Assessing the effectiveness of emission controls

Abstract

Total emission control of sulfur has been stringently implemented in the last two five-year plans (2000–2010), as a key national environmental policy in China. As a result of this policy, SO2 emissions in the Pearl River Delta (PRD) region were reduced by 212.5 kilotons. The regional monitoring network data indicate a 39% reduction of ambient SO2 concentrations between 2006 and 2009. SCIAMACHY satellite data show a 27% decrease in the whole column SO2 concentration during the same period. To assess what role changes in meteorology contributed to the observed changes in concentrations in this time period, sensitive experiments for November of 2006 and 2009 where different combinations of changing emissions under constant meteorology and vice versa were simulated using the MM5-STEM model. In general, the model can well capture the day-to-day variation patterns of meteorology and ambient SO2. At the regional scale, long-term emission controls constantly reduce ambient SO2 and sulfate concentrations, while meteorology has negative and positive effects in the PRD. The contribution of meteorological effects to the composite difference of SO2 concentration varied in different cities, ranging from −20% to 33%. According to meteorological effects, three categories of cities were established and indicated the meteorological role in different cities. Regional transport is very important to WQS site, ranging from −39 to +67 μg m−3 for the SO2 concentration. Both the meteorological conditions and trans-boundary transport play important and complex role in the linkage between emission and ambient concentration.