Effect of three plant hormone elicitors on the camptothecin accumulation and gene transcript profiling in Camptotheca acuminata seedlings.

Ambient air Volatile Organic Compounds in Benin City was evaluated for their concentrations using active sampling methods, with the objective of determine the mass contributions of the different sources. Air samples were collected at a human breathing height of 1.5 meters and from nine locations comprising industrial, residential and commercial areas with heavy traffic on a four hourly basis using active sampler at flow rate of 0.51min-1. The sampling periods cover both dry and wet seasons. Collected samples were desorbed and analyzed for volatile organic compounds using gas chromatography with flame ionization detector. The concentrations of analytes were read from the calibration graph, which was done with standard solution prepared externally. The data of ambient VOCs analysis were subjected to statistical analysis; correlation analysis, factor analysis, principal component analysis/absolute principal component scores (PCA/APCS) model. The average concentrations of the ambient Volatile Organic Compounds (VOC) in the studied city exhibit higher concentrations in dry season months. The results obtained reveal negative or weak correlation coefficients for most Volatile Organic Compounds species, an indication of importance of other VOCs sources in addition to exhaust emission. The results from the PCA/APCS receptor modelling showed that during the dry season, the highest contribution of 53% comes from vehicular emission in the studied area. Meanwhile, evaporative emission contributes the highest during the wet season with 35% for the same locations. High correlation coefficient (R2 >0.8) between the measured and predicted values suggested that PCA/APCS model is suitable for estimation of sources of VOCs in ambient air.