“…Nevertheless, it is known that the presence of natural substances such as humic acids, nitrate and carbonate ions in aqueous systems can exert a great influence on the photodegradation rates of parent herbicide as well as in the nature and the quantities of the by-products formed [6,18,19]. In this sense, previously we performed a kinetic study of the photolysis of sethoxydim in different natural waters under sunlight [20]. We observed that the rate of photodegradation of sethoxydim varied as a function of organic matter content, showing the lowest degradation rate at the highest concentration of organic matter.…”