Air pollution in mega cities in China

Water quality issues are a major challenge that humanity is facing in the twenty-first century. Here, we review the main groups of aquatic contaminants, their effects on human health, and approaches to mitigate pollution of freshwater resources. Emphasis is placed on chemical pollution, particularly on inorganic and organic micropollutants including toxic metals and metalloids as well as a large variety of synthetic organic chemicals. Some aspects of waterborne diseases and the urgent need for improved sanitation in developing countries are also discussed. The review addresses current scientific advances to cope with the great diversity of pollutants. It is organized along the different temporal and spatial scales of global water pollution. Persistent organic pollutants (POPs) have affected water systems on a global scale for more than five decades; during that time geogenic pollutants, mining operations, and hazardous waste sites have been the most relevant sources of long-term regional and local water pollution. Agricultural chemicals and wastewater sources exert shorter-term effects on regional to local scales.

https://www.annualreviews.org/doi/pdf/10.1146/annurev-environ-100809-125342

Global Water Pollution and Human Health

. In this study, 121 daily PM2.5 (aerosol particle with aerodynamic diameter less than 2.5 μm) samples were collected from an urban site in Beijing in four months between April 2009 and January 2010 representing the four seasons. The samples were determined for various compositions, including elements, ions, and organic/elemental carbon. Various approaches, such as chemical mass balance, positive matrix factorization (PMF), trajectory clustering, and potential source contribution function (PSCF), were employed for characterizing aerosol speciation, identifying likely sources, and apportioning contributions from each likely source. Our results have shown distinctive seasonality for various aerosol speciations associated with PM2.5 in Beijing. Soil dust waxes in the spring and wanes in the summer. Regarding the secondary aerosol components, inorganic and organic species may behave in different manners. The former preferentially forms in the hot and humid summer via photochemical reactions, although their precursor gases, such as SO2 and NOx, are emitted much more in winter. The latter seems to favorably form in the cold and dry winter. Synoptic meteorological and climate conditions can overwhelm the emission pattern in the formation of secondary aerosols. The PMF model identified six main sources: soil dust, coal combustion, biomass burning, traffic and waste incineration emission, industrial pollution, and secondary inorganic aerosol. Each of these sources has an annual mean contribution of 16, 14, 13, 3, 28, and 26%, respectively, to PM2.5. However, the relative contributions of these identified sources significantly vary with changing seasons. The results of trajectory clustering and the PSCF method demonstrated that regional sources could be crucial contributors to PM pollution in Beijing. In conclusion, we have unraveled some complex aspects of the pollution sources and formation processes of PM2.5 in Beijing. To our knowledge, this is the first systematic study that comprehensively explores the chemical characterizations and source apportionments of PM2.5 aerosol speciation in Beijing by applying multiple approaches based on a completely seasonal perspective.

/pdf/chemical-characterization-and-source-apportionment-of-pm-2-5-3q6oghogl3.pdf

Chemical characterization and source apportionment of PM 2.5 in Beijing: seasonal perspective

Ozone pollution in China: A review of concentrations, meteorological influences, chemical precursors, and effects

. From 2006 to 2007, the daily concentrations of major inorganic water-soluble constituents, mineral aerosol, organic carbon (OC) and elemental carbon (EC) in ambient PM10 samples were investigated from 16 urban, rural and remote sites in various regions of China, and were compared with global aerosol measurements. A large difference between urban and rural chemical species was found, normally with 1.5 to 2.5 factors higher in urban than in rural sites. Optically-scattering aerosols, such as sulfate (~16%), OC (~15%), nitrate (~7%), ammonium (~5%) and mineral aerosol (~35%) in most circumstance, are majorities of the total aerosols, indicating a dominant scattering feature of aerosols in China. Of the total OC, ~55%–60% can be attributed to the formation of the secondary organic carbon (SOC). The absorbing aerosol EC only accounts for ~3.5% of the total PM10. Seasonally, maximum concentrations of most aerosol species were found in winter while mineral aerosol peaks in spring. In addition to the regular seasonal maximum, secondary peaks were found for sulfate and ammonium in summer and for OC and EC in May and June. This can be considered as a typical seasonal pattern in various aerosol components in China. Aerosol acidity was normally neutral in most of urban areas, but becomes some acidic in rural areas. Based on the surface visibility observations from 681 meteorological stations in China between 1957 and 2005, four major haze areas are identified with similar visibility changes, namely, (1) Hua Bei Plain in N. China, and the Guanzhong Plain; (2) E. China with the main body in the Yangtze River Delta area; (3) S. China with most areas of Guangdong and the Pearl River Delta area; (4) The Si Chuan Basin in S.W. China. The degradation of visibility in these areas is linked with the emission changes and high PM concentrations. Such quantitative chemical characterization of aerosols is essential in assessing their role in atmospheric chemistry and weather-climate effects, and in validating atmospheric models.

/pdf/atmospheric-aerosol-compositions-in-china-spatial-temporal-21nw523s36.pdf

Atmospheric aerosol compositions in China: spatial/temporal variability, chemical signature, regional haze distribution and comparisons with global aerosols

City clusters are made up of groups of large, nearly contiguous cities with many adjoining satellite cities and towns. Over the past two decades, such clusters have played a leading role in the economic growth of China, owing to their collective economic capacity and interdependency. However, the economic boom has led to a general decline in environmental quality. This paper will review the development and current status of the major environmental problems caused by city clusters, focusing on water and air pollution, and suggest possi- ble strategies for solving these problems. Currently, deteriorating water quality is of major concern to the pub- lic and decision makers alike, and more than three-quarters of the urban population are exposed to air quality that does not meet the national ambient air quality standards of China. Furthermore, this pollution is charac- terized by high concentrations of both primary and secondary pollutants. Environmental pollution issues are therefore much more complex in China than in western countries. China is expected to quadruple its GDP by 2020 (using 2000 as the base year for comparison) and, consequently, will face even more serious environmen- tal challenges. Improving energy efficiency and moderating the consumption of natural resources are essential if China is to achieve a balance between economic development and environmental health.

https://esajournals.onlinelibrary.wiley.com/doi/epdf/10.1890/1540-9295%282006%29004%5B0353%3ACCICAA%5D2.0.CO%3B2

City clusters in China: air and surface water pollution

Seasonal variation of ionic species in fine particles at Qingdao, China

Spatial distribution of traffic-related pollutant concentrations in street canyons

A new apparatus, Steam Jet Aerosol Collector (SJAC) combined with on-line Mobile Ion Chromatograph provides a reliable way to measure both aerosol components and related gas species simultaneously. The SJAC was applied in the field campaigns in Beijing and Guangzhou to investigate aerosol chemical compositions and related gaseous pollutants. The concentration levels and diurnal variations are discussed, which implies differences in atmospheric chemistry of gas-to-particle conversions in Beijing and Guangzhou.

Diurnal variations of aerosol chemical compositions and related gaseous pollutants in beijing and guangzhou

A measurement campaign was performed in two large cities in China, Beijing and Guangzhou, to investigate biogenic emissions of volatile organic compounds (VOCs) using a GC‐FID system and the enclosure chamber technique. Four typical types of trees, namely pine, cypress, poplar and Chinese‐scholar tree were studied. The influences of temperature and light intensity on VOC emissions were analyzed using algorithms derived from what is currently understood about VOC emission mechanisms. Biogenic VOC emission fluxes in these two cities were estimated. A 2‐D air quality model was developed to assess the role of biogenic VOC emissions in the ground‐level ozone formation in Beijing and Guangzhou.

Yuanhang Zhang

Papers

City clusters in China: air and surface water pollution

Seasonal variation of ionic species in fine particles at Qingdao, China

Spatial distribution of traffic-related pollutant concentrations in street canyons

Diurnal variations of aerosol chemical compositions and related gaseous pollutants in beijing and guangzhou

Biogenic vocs emissions and its impact on ozone formation in major cities of China