Chlorophyll Fluorescence Applied in the Analysis on Vertical Movement of Herbicides in Soil

Five photosynthesis inhibiting herbicides were com pared for their mobility in soil colum ns used as the penetration m odel. The vertical m ovem ent o f these com pounds in soil was an a ­ lyzed by a newly developed technique in which herbicide distribution was determ ined by the intensity o f chlorophyll fluorescence in Chlorella cells suspended in aqueous extracts o f soil samples from various depths. W ith the aid o f a fluorescence m icroplate scanner, m easurem ent o f chlorophyll fluorescence was perform ed with great efficiency. Photosynthesis inhibiting activity o f tested herbicides was determ ined beforehand by the same m ethod and served in cal­ culating herbicide concentrations in sample extracts. Among tested com pounds, hexazinone showed the greatest m obility and diuron the smallest, suggesting w ater solubility is one o f the factors which govern the soil mobility o f herbicides.