Photodegradation of the Fungicide Isopyrazam in Aqueous Solution: Kinetics, Photolytic Pathways, and Aquatic Toxicity

Abstract

Photodegradation behavior of a new fungicide isopyrazam in water under simulated sunlight and ultraviolet (UV) irradiation was studied. The photolysis half-life (t 1/2 ) of isopyrazam in purified water was 195 h under simulated sunlight, which was decreased to 46−88 h, 28−51 h, and 13−18 h in the presence of NO 3 − , Fe 3+ , and riboflavin, respectively. UV irradiation accelerated the photolysis of isopyrazam with a half-life of 30 min and revealed varied degradation rates in acidic (0.011 min −1 ), neutral (0.024 min −1 ), and alkaline solutions (0.022 min −1 ). Nine transformation products under simulated sunlight and UV were found, and photolytic pathways were proposed to include cleavage of C−N bonds, hydroxylation, nitration, demethylation, dehydrofluorination, and photoisomerization. The acute toxicity of defluorinated isopyrazam (TP 4) and the chronic toxicity of isomerized isopyrazam (TP 9) to aquatic organisms were approximately twice that of isopyrazam. These findings provide insights into environmental risk assessment and management of water pollution.

Se-Pair Search for Deciphering Selenium-Encoded Peptide and a Pyrolysis-Thermolysis Dietary Model for Minimizing Loss of “KKSe(M)R” during Processing

“…Simultaneously, when the C–N and C–C bonds that remain linked to the N-terminal lysine were broken, Se­(M)­R, C 14 H 27 N 5 O 4 Se “ m / z 408.11445” was formed. Available evidence shows that the C–N bond is cleaved owing to the low bond energy of the C–N bond. , Whereas the C–N bond is more probable to be cleaved due to its lower bond energy by comparison to the C–C bond, the C–N bond on the N-terminal lysine, as well as the C–C bond on the C-terminal methionine, was cleaved according to the selenoproteomic analysis mentioned in KSe­(M), C 10 H 19 N 2 OSe “ m / z 264.07354”. Additionally, the absorption of thermal energy by the selenium-encoded peptide KKSe­(M)­R cleaved the C–N bond of the C-terminal arginine to form a new product KKSe­(M), C 22 H 44 N 6 O 5 Se “ m / z 551.24547”.…”

“…The content of pyrolysis-thermolysis intermediates underwent variations at pyrolysis-thermolysis time and temperature matrices (Figure c–f). Although the real-time variations of pyrolysis-thermolysis intermediates at pyrolysis-thermolysis matrices are elusive to quantify, the mathematical fitting model proposed an auxiliary method for estimating the two selenopeptide intermediates . It can be hypothesized that the produced pyrolysis-thermolysis intermediate variable m / z 482.19885 (or m / z 465.17230) has a content ratio of “1”.…”