AIR POLLUTION AND ITS EFFECTS ON PLANTS IN CHINA.

(1) Atmospheric pollution in China comes mainly from human activities such as urbanization and industrialization. Such activities have become more prominent in the last 10 years, and in urban and industrial areas air pollution is typically a coal-smoke smog. (2) Air pollution monitoring indicates that in 22.2% of sixty-four cities the second grade National Air Quality Standard for sulphur dioxide (24-h mean concentration 015 tug m-3) is exceeded by 30%. The 24-h mean concentration of total suspended particulates in all. cities exceeds the second grade National Air Quality Standard (0mg m-3) by 97%, whilst nitrogen oxides are below the second grade standard (0.3 mg m-3). The quality of air in most cities continues to deteriorate. (3) Simulation studies on the effects of air pollution typical of some urban and industrial areas on local crops and vegetables suggested that ambient concentrations of sulphur dioxide and fluoride could reduce the growth and yield of crops. by 5-25%. (4) Fumigation studies on the physiological and biochemical responses of plants to air pollution demonstrated a reduction in chlorophyll content; inhibition of photosynthesis; increases in potassium leakage, stomatal resistance, respiration and proline; and increases in superoxide dismutase and peroxidase activities as the concentration and exposure time of sulphur dioxide and fluoride increase, Preliminary studies on the injury mechanisms of sulphur dioxide indicate that free radicles participate in the course of injury. [ABSTRACT FROM AUTHOR]