Study And Application Of Environmental Radon In Guangzhou

The environment air quality has become the focus of attentions to the public in recent years. The Chinese Government has recognized the potential risks and problems related to environment air pollution, and it has established some new standards(GB/ T18883-2002, GB/T6566-2001 and GB50325-2001) etc. Many researchers in different countries or regions also have conducted studies of environment air pollutions, but there are fewer studies focused on these subjects have been conducted in our country because of various factors. Guangzhou is more developed in society and economy than inland after reform in China, unfortunately, there are only a few studies on the environment air quality have been carried out yet.This study attempts to investigate the environment radon concentration in Guangzhou, includes the soil radon concentration and the radon level of indoor air in the new buildings. The soil radon is the main source of the radon in the air, the indoor radon level is related to the content of the radionuclide in the building materials. The indoor air pollutants also measured in 274 new buildings included the formaldehyde, benzene, TVOC and ammonia.This paper also includes a pilot study — the application of the soil radon measurement in geology structure and geothermal surveying.Based on those studies, we can conclude that:1. The soil radon in Guangzhou is controlled by the geology structure, also related to the strata. In the region from the north of the Shougouling fault to the east of the Guangcong fault, the rock mainly is granite, with some migmatite. The content of the radionuclide is the highest in Guangzhou. The regional background value of the soil radon in this district is 6775 Bq/m3; the regional background value of the soil radon in the south area of the Shougouling fault is 3200 Bq/m3. The strata(foundation) in this area are mainly the red sandstone with some mudstone and gravel of the Cretaceous. The content of the radionuclide is higher than the west andlower than the north. The regional background value of the soil radon in the west of the Guangcong fault is 3883Bq/m3. The content of the radionuclide in this area is the lowest in Guangzhou. The strata in this distract include limestone, limestone with coal, sandstone, mudstone, shale of the Carboniferous, Devonian, Dyas and Trias.2. The soil radon is a good tracer. The soil radon measurement is a good surveying technique for structure and geothermal, but it only effectual to tension faults.3. The radon concentrations in indoor air in the new buildings in Guangzhou are all bellow the IAQ standard except for one room, it has little risk to the people if they often open the door and window. The mean value is 47.7Bq/m3. It is higher than 26Bq/m3(the national mean value) and 35Bq/m3(predecessor's result).The radon concentration is not relevant obviously to the soil radon consistence of the building site, but it is down slightly with the height goes higher. That means the radon level in indoor air in the new buildings is not determined by its foundation's soil radon density. Or say, there are no paths for soil radon to get into the modern buildings. This is because some structure measures have been taken into the consideration in these building's foundations, such as ground floor with certain thickness, closed by fine bricks, etc.; It is important to the radon level in indoor air that the radionulide content of the materials used in the buildings; The geology structure in Guangzhou is developed very much, and the radon level on the faults is very high, so when buildings are constructed on these areas the engineering geology report have to be serious studied for reducing risk and lowing cost especially to the public buildings. It is more important in suburban areas, because the buildings in those areas usually are less than three layers, and mostly no measures are taken in the ground floor.4. The daily change of the indoor radon levels in Guangzhou is similar to the general regulation, and that is higher in the morning and lower in the evening.5. The mixing concrete on the building site was forbidden in Guangzhou. All the concrete used in Guangzhou now is merchandise concrete. Some coal ash powder and chemical additives are added in the merchandise concrete for the need of thepumping and long stance transportation. We found that the radionuclide of the concrete in Guangzhou is higher, and it is not only due to the radionuclide in the broken stone used in it, but also due to the radionuclide in the coal ash powder.6. The radionuclide content of the merchandise concrete can be calculated by the formulation if the radionuclide contents of the materials in the concrete are known.7. The red brick is strictly forbidden and substituted for light bricks in buildings for the farmland and environment protection. The radionuclide of the light wall materials has direct influence to the indoor radon level.8. Our study found that all the consistence of the formaldehyde, benzene, TVOC, ammonia in indoor air is mostly bellow the IAQ standard. The abnormal ratio is not high, and some rooms in which the formaldehyde, benzene, TVOC are higher than IAQ standard were decorated. The highest formaldehyde was 2.25 times of the standard, benzene 321 times, TVOC 173 times, respectively. Attentions and some measures have to be taken in this room, for example, ventilation, later to live in, etc.. At the same time, the supervision for materials sold on market, such as coatings, wood panels adhesives, decorated wood-based panels have to be strengthened immediately, because the decoration was simple and there was no furniture in it, and the formaldehyde, benzene, TVOC all were get out from those materials.9. It was found that the levels of the formaldehyde, benzene, TVOC in indoor air are not relevant to the height of samples, but the ammonia concentration of indoor air is lower with the building's height obviously.