Heavy Pollution Periods Research Articles

Growth, healthy status and seed production of differently aged allochtonous and autochtonous Pinus mugo stands in the Giant Mts. over 30 years

Plant communities with Dwarf pine (Pinus mugo var. pumilio) form characteristic vegetation in the subalpine belt of the Giant Mountains (Krkonose, Karkonosze and Riesengebirge, Czech Republic). This “island” of arcto-alpine tundra represents the northernmost edge of Dwarf pine natural range. We asked how concentration of sulphur in needles, growth, healthy status and fructification changed over three decades (1981–2011) with different air pollution in differently aged (45–120 years) autochtonous and allochtonous (introduced from the Alps) Dwarf pine stands. Different Dwarf pine stands above the alpine timberline were able to withstand 1980s, the period of heavy air pollution, without any decrease in growth rate or remarkable decrease in healthy status. Dwarf pine is thus highly tolerant to deposition of sulphur compounds. High concentration of SO2 in the air positively affected sulphur concentration in needles and eliminated thus sulphur deficiency. Higher germination rate of seeds in 2000s in comparison with 1980s indicate that the air pollution could decrease germination ability of seeds. High insect outbreaks (by Thecodiplosis brachyntera and Neodiprion sertifer) in 1990s and 2000s caused decrease in needle year classes. As there was a gradual increase in mean annual temperature over years 1981–2011, Dwarf pine stands can be more and more endangered by insect outbreaks in the future. There was no remarkable difference between autochtonous and allochtonous stands in all measured growth, healthy status and fructification characteristics. To determine real effects of air pollution and insect outbreaks on Dwarf pine stands from year to year fluctuations, decade-long monitoring is necessary.

Impact of national NOx and SO2 control policies on particulate matter pollution in China

China's air pollution control policies during the 12th Five Year Plan (2011–2015) are characterized by the targets of 10% nitrogen oxides (NOx) reduction and 8% sulfur dioxide (SO2) reduction from the 2010 levels. In this study, the Community Multi-scale Air Quality (CMAQ) modeling system was used to evaluate the impact of only SO2, only NOx, and joint SO2/NOx control measures on particulate matter pollution, the greatest concern for urban air quality in China. Four emission scenarios were developed for 2015, including a business-as-usual scenario, a reference NOx control scenario based on the governmental plan, an accelerated NOx control technology scenario, and a scenario assuming joint controls of NOx and SO2 based on the governmental plan. Under the planned NOx control measures, the annual mean concentrations of particulate matter less than or equal to 2.5 μm (PM2.5) decline by 1.5–6 μg m−3, i.e. 1.6%–8.5%, in the majority of eastern China. The largest reduction occurs in the middle reach of the Yangtze River. Under accelerated NOx control measures, the annual average PM2.5 concentration reductions (compared with the business-as-usual scenario) in eastern China are 65% higher than the reductions under planned control measures. The unusual increase of PM2.5 concentrations in the North China Plain and the Yangtze River Delta during January after the reductions of NOx emissions was an integrated effect of excessive NOx, the ammonia-rich inorganic aerosol chemistry, and the non-methane volatile organic compounds (NMVOC) sensitive photochemical regime. Under the joint controls of NOx and SO2, the annual mean PM2.5 concentrations decline over 3 μg m−3, i.e. 3.2%–13%, in the majority of eastern China, and some areas in the middle reach of the Yangtze River have reductions as large as 6–8.3 μg m−3, i.e. 5.0%–13%. The average PM2.5 concentration reductions in eastern China are 1.20 μg m−3, 3.14 μg m−3, 3.57 μg m−3, 4.22 μg m−3 in January, May, August, and November, respectively. The corresponding declining rates are 2.3%, 12.2%, 14.3%, and 8.1%, respectively. More stringent policies should be implemented in winter to reduce the heavy pollution periods. The annual average PM2.5 concentration reductions in three major city clusters are comparable with the average reductions of eastern China. Stringent regional control policies are required for the significant improvement of particulate air quality in major city clusters.

A Monitoring and Modeling Study to Investigate Regional Transport and Characteristics of PM2.5 Pollution

In this study, the regional transport and characteristics of PM2.5 pollution were examined through a case study in Beijing, China. The results from an intensive monitoring program indicate that the inorganic particles (sulfate, nitrate, and ammonium), organic carbons, and the elements accounted for 35.5, 24.2, and 15.3% of the total PM2.5 on an annual average basis, respectively. The proportions of such PM2.5 components also showed clear seasonal variations. An integrated MM5-CMAQ modeling system was then developed to examine the regional transport of PM2.5 and its components in Beijing within four typical months of 2010. The results indicate that the annual average total trans-boundary contribution ratio (TBCR) is 42.2, 46.3, 77.4, and 61.6% for the concentrations of PM2.5, sulfate, nitrate, and ammonium, respectively. A logarithmic relationship was found between the total TBCR and the PM2.5 concentrations in Beijing for different seasons. Further investigations showed that trans-boundary transport played a major role in Beijing’s PM2.5 concentrations during the period of high pollution levels, with an annual average TBCR of 54.6%. As a result, the control of PM2.5 pollution in Beijing needs effective cooperation between Beijing and its surrounding regions, especially during periods of heavy pollution.

Nonlinear response of ozone to precursor emission changes in China: a modeling study using response surface methodology

Abstract. Statistical response surface methodology (RSM) is successfully applied for a Community Multi-scale Air Quality model (CMAQ) analysis of ozone sensitivity studies. Prediction performance has been demonstrated through cross validation, out-of-sample validation and isopleth validation. Sample methods and key parameters, including the maximum numbers of variables involved in statistical interpolation and training samples have been tested and selected through computational experiments. Overall impacts from individual source categories which include local/regional NOx and VOC emission sources and NOx emissions from power plants for three megacities – Beijing, Shanghai and Guangzhou – were evaluated using an RSM analysis of a July 2005 modeling study. NOx control appears to be beneficial for ozone reduction in the downwind areas which usually experience high ozone levels, and NOx control is likely to be more effective than anthropogenic VOC control during periods of heavy photochemical pollution. Regional NOx source categories are strong contributors to surface ozone mixing ratios in three megacities. Local NOx emission control without regional involvement may raise the risk of increasing urban ozone levels due to the VOC-limited conditions. However, local NOx control provides considerable reduction of ozone in upper layers (up to 1 km where the ozone chemistry is NOx-limited) and helps improve regional air quality in downwind areas. Stricter NOx emission control has a substantial effect on ozone reduction because of the shift from VOC-limited to NOx-limited chemistry. Therefore, NOx emission control should be significantly enhanced to reduce ozone pollution in China.

Atmospheric aerosol concentration level and chemical characteristics of water-soluble ionic species in wintertime in Beijing, China.

Total suspended particulate (TSP) samples were collected during wintertime from November 24, 1998 to February 12, 1999 in Beijing. Ionic species including Cl-, NO3(-), SO4(2-), Na+, NH4(+), K+, Mg2+ and Ca2+ were determined by Ion Chromatography (IC). The sum average concentration of all the determined ions accounted for 18.9% of the TSP concentration, and SO4(2-) appeared the dominant ion with an average concentration of 30.84 microg m(-3); the sum mass concentration of SO4(2-), NO3(-), Ca2+ and NH4(+) accounted for about 83.2% of all the eight ions measured. The study indicated that the chemical form of sulfate and ammonium varies with TSP concentration levels. During heavy pollution periods, the average TSP concentration was 0.66 mg m(-3), and the NH4(+)/SO4(2-) molar ratio was low (0.58). It indicated that sulfate may present as CaSO4 and (NH4)2SO4 x CaSO4 x 2H2O. When TSP concentration (average 0.186 mg m(-3)) was relatively low, the NH4(+)/SO4(2-) molar ratio was 1.94, close to the theoretical ratio of 2 of (NH4)2SO4. Under this condition (NH4)2SO4 is expected to exist as the major form of sulfate. When the TSP concentration level was medium (average 0.35 mg m(-3)), the NH4+/SO4(2-) molar ratio appeared an average value (1.27), (NH4)2SO4, (NH4)2SO4 x CaSO4 x 2H2O and CaSO4 are expected to be present in those aerosol particles. Meteorological conditions including wind speed and wind direction were related to the TSP concentration level.

Soiling Patterns on a Tall Limestone Building: Changes over 60 Years

Soiling of limestone caused by air pollution has been studied at the Cathedral of Learning on the University of Pittsburgh campus. The Cathedral was constructed in the 1930s during a period of heavy pollution in Pittsburgh, PA. Archival photographs show that the building became soiled while it was still under construction. Reductions in air pollutant concentrations began in the late 1940s and 1950s and have continued to the present day. Concurrent with decreasing pollution, soiled areas of the stone have been slowly washed by rain, leaving a white, eroded surface. The patterns of white areas in archival photographs of the building are consistent with computer modeling of rain impingement showing greater wash off rates at higher elevations and on the corners of the building. Winds during the rainstorms are predominantly from the quadrant SW to NW at this location, and wind speeds as well as rain intensities are greater when winds are from this quadrant as compared with other quadrants; the sides of the building facing these directions are much less soiled than the opposing sides. Overall, these results suggest that rain washing of soiled areas on buildings occurs over a period of decades, in contrast to the process of soiling that occurs much more rapidly.

Red blood cell antioxidants in human volunteers exposed to ozone.

Indices of red blood cell (RBC) antioxidant capacity can undergo changes upon exposure to oxidants, either acutely or chronically. To investigate whether these changes might provide a biochemical marker for acute environmental ozone exposure, we assessed RBC glutathione (GSH) and catalase (CAT) responses in seven normal volunteers exposed to 0.16 ppm ozone for 7.5 hours compared to the same measurements following sham exposure to clean air. For each subject, an interim period of two weeks separated the two exposure studies. Investigators performing the RBC assays were unaware of the environmental conditions. No changes in either GSH or CAT were observed for any study condition when compared to pre-study values. Our conclusion is that RBC antioxidants do not accurately reflect in vivo exposure to ozone at concentrations readily attainable during periods of heavy urban pollution. Our data dispute the value of these indices as markers of acute environmental photochemical oxidant exposure.

Analysis of polycyclic aromatic hydrocarbons in air particulate matter from a lightly industrialized urban area

Levels of polycyclic aromatic hydrocarbons (PAH) have been measured in the air particulate matter (APM) of a lightly industrialized urban area in which the main sources of PAH are domestic fires and automobiles. The PAH were analyzed by glass capillary gas chromatography combined with mass spectrometry. Statistical analysis of the results using 26 PAH allows the relative contribution of the two sources to be estimated and shows that during periods of heavy pollution (APM > 100 ..mu..g m/sup -3/) domestic fires are the main contributors. A simpler ratio, ln (1 + (benzofluoranthenes)/(total PAH)) - ln (1 + (benzo(ghi)perylene)/(total PAH)), gives similar discrimination.

Chronosequences in alluvial soils with special reference to historic lead pollution in Cardiganshire, Wales

Soils have developed on an enlarging meander loop in the River Rheidol valley following a period of severe heavy metal pollution in the nineteenth century. Successive zones of the alluvium have been identified according to age of deposition. Soils in these zones comprise a normal chronosequence with regard to humus and free iron oxide content. Heavy metal contamination is worst in the oldest section, contemporaneous with maximum lead mining activity, but is appreciable even in the most recent section. The relevance of these results to other alluvial regions is discussed.