Fluoride and sulfur dioxide indoor pollution situation and control in coal-burning endemic area in Zhaotong, Yunnan, China

摘要

The presented study aims to investigate the gaseous fluoride and sulfur dioxide (SO_2) pollution level in the kitchen, traditional flue-curing barn and outdoor environment and to find economically feasible method to reduce fluorine and sulfur release. The gaseous fluoride and SO_2 concentrations in air of outdoor environment, kitchen and traditional flue-curing barn were determined in 56 households in coal-burning endemic fluorosis areas of Zhaotong. Among these, 21 households in Yujiawan Village, Zhenxiong County, Zhaotong City were chosen for this experiment to reduce gaseous fluoride and SO_2 concentration in traditional flue-curing barn air by using calcined dolomitic siliceous limestone (CDSL) instead of clay mixed with coal. The result showed that: (1) gaseous fluoride and SO_2 concentration in the outdoor air in Mangbu Township area was 0.51 μg dm~(-2)· day and <0.05 mg m~(-3), respectively and in Xiaolongdong Township was 2.7 μg dm~(-2) day and <0.05 mg m~(-3), respectively while in Zhaotong City these concentration were lower than the ambient air standard (3 μg dm~(-2)·day and 0.5 mg m~(-3), respectively). (2) The indoor gaseous fluoride concentration (3.7 μg m~(-3)) in air of kitchen with the improved coal stove was within the reference value (10 μg m~(-3)); SO_2 concentration (0.94 mg m~(-3)) in kitchen air had decline, but its concentration was still higher than indoor air quality standard (0.5 mg m~(-3)). (3) Average concentration of gaseous fluoride and SO_2 in air of traditional flue-curing barn of Xiaolongdong Township was 7.2 μg m~(-3) and 6.8 mg m~(-3) respectively, and in Yujiawan village were 10.1 μg m~(-3) and 14.4 mg m~(-3), respectively. (4) After using the calcined dolomitic siliceous limestone instead of clay mixed with coal, gaseous fluoride and SO_2 concentration in the traditional flue-curing barn air decreased of 45% and 91%, respectively. The gaseous fluoride and SO_2 pollution in the traditional flue-curing barn is very serious. The corn and chili baked by open stoves in traditional flue-curing barn (baking room) was also seriously polluted by fluoride and sulfur. After using the calcined dolomitic siliceous limestone instead of clay mixed with coal, gaseous fluoride and SO_2 concentration in the traditional flue-curing barn air have declined markedly. The way of adding calcined dolomitic siliceous limestone instead of clay as a binder for briquette-making is an economically feasible way to control the indoor pollution of fluorine and sulfur in coal-burning endemic in Zhaotong, Yunnan.