Decomposition of selected organic micropollutants under solar radiation

Natural solar radiation is considered a free energy source, continuously reaching the earth's surface. Next to biological processes, it plays a crucial role in the decomposition of pollutants introduced by humans into the environment. Integrating of natural photo-decomposition with other physico-chemical processes becomes a current and effective water purification method. The research focused on investigating the decomposition of selected micropollutant water solutions exposed to the direct action of sunlight. Model aqueous solutions (deionized water, salt water, and surface water) were spiked with analytical standards of diclofenac, triclosan, butylated hydroxytoluene, and 4-tert-octylphenol and subjected to solar radiation during European winter, spring, summer, and fall periods. The samples were tested using gas chromatography, the Microtox bioassay, and the Lemna minor Growth Inhibition Test (GIT). It has been shown that the decomposition rate of all tested compounds strongly depends on the period of the year. It relates to the different intensities of solar radiation reaching the earth's surface. The highest number of by-products of the decomposition of individual compounds was observed in the spring and autumn periods. These post-process solutions were also characterized by higher toxicity than those processed in summer and winter.