Afforestation for reduction of NOX concentration in Lanzhou China.

Lanzhou is one of the major industrial cities in northwest China, the capital of Gansu Province, and located at a northwest-to-southeast oriented valley basin with elevation about 1500-1600-m. Due to topographic and meteorological characteristics, Lanzhou is one of the most polluted cities in China. Meteorological conditions (low winds, stable stratification especially inversion), pollutant sources and sinks affect the air quality. Lanzhou government carried out afforestation and pollutant-source reduction (closing several heavy industrial factories) to improve the air quality for the past two decades. In this study, effect of afforestation on reducing the NO(X) concentration is investigated numerically using RAMS-HYPACT model.