Photodegradation behavior of a new fungicide isopyrazam in water under simulated sunlight and ultraviolet (UV) irradiation was studied. The photolysis half-life (t1/2) 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 NO3–, Fe3+, 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.
Dan Hu,Xu Xu,Tian Cai,Wei-Ying Wang,Chun-Jie Wu,Li-Ming Ye
ABSTRACT A rapid and sensitive analytical method based on high-performance liquid chromatography–tandem mass spectrometry was developed and validated for the determination of isopyrazam (IZM) and azoxystrobin (AZT) in cucumbers. A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was used as the pretreatment procedure. The samples were extracted with acetonitrile and cleaned up with octadecylsilyl silica (C18) and graphite carbon black. The proposed method resulted in satisfactory recovery of IZM and AZT (91.48 to 114.62%), and relative standard deviations were less than 13.1% at fortification concentrations of 1, 20, and 500 μg kg −1 ( n = 3). The limits of quantification for IZM and AZT were 0.498 and 0.499 μg kg −1 , respectively, which are far below the maximum residue level (0.5 mg kg −1 ) established for this type of sample. Matrix effects were also evaluated. This study established a sensitive and fast method for the detection of IZM and AZT in cucumber samples.
Isopyrazam (IPZ) is a broad spectrum succinate dehydrogenase inhibitor fungicide. Little is known about its potential ecological risks of aquatic organisms recently. The present study examined the embryonic development effects of zebrafish exposed to IPZ under static condition using a fish embryo toxicity test. The lowest observed effect concentration of IPZ was 0.025 mg/L in 4-day exposure. Developmental abnormalities, including edema, small head deformity, body deformation and decreased pigmentation, and mortality were observed in zebrafish embryos of 0.05 mg/L and higher concentrations, which shown concentration dependency. The heart rate of zebrafish was disrupted by IPZ. Moreover, enzyme and gene experiments shown that IPZ exposure caused oxidative stress of zebrafish. Furthermore, it induced a decrease of succinate dehydrogenase (SDH) enzyme activity and gene transcription level in zebrafish larvae. It can be speculated that IPZ may have a lethal effect on zebrafish, which is accompanied by decreased SDH activity, oxidative stress, and abnormality. These results provide toxicological data about the IPZ on aquatic non-target organisms, which could be useful for further understanding potential environmental risks.
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