High concentration of insecticides may appear in waters surrounding paddy fields shortly after application. Capturing the dynamic feature of this insecticide pulse may help control insecticide load to receiving waters. Based on continuous monitoring of the drainage process and two monitoring campaigns of three insecticides—chlorpyrifos, abamectin and thiamethoxam—in a paddy, this study examined the pattern of insecticide concentrations at different locations of paddy waters during the period of insecticide application accompanied with pest-control irrigation, and analyzed the factors affecting the environmental behavior of these insecticides. The results showed that the pulse-type drainage exhibited the following features: short duration (normally less than 1 d), large flow rate (as large as 4 L s⁻¹), frequent occurrence (20 times during a 40-d period) and long time interval (as long as 5 d). Concentrations of the insecticides with higher Henry’s constant and vapor pressure peaked quickly (within several hours) post application in the field ditch; more than half of chlorpyrifos and abamectin loads were detected within merely 1 h after application. The high insecticide concentrations in the ditch were partly attributed to the primary and secondary drift. Moreover, a new kinetic model was proposed to describe the behavior of chlorpyrifos at the field edge. It is recommended that controlled drainage be implemented for at least 1 d post application to prevent the loss of insecticides. Findings from this study may provide new insights into insecticide behavior in the paddy environment for preventing adverse environmental impacts.

Novel method for calculating flow depth in open channels combining the iteration theory and the curve-fitting technique

Viruses are the most abundant and active biological organisms in soil ecosystems. However, their spatial distribution and ecological functions remain inadequately addressed owing to a lack of systematic analysis and the complexity of the soil matrix. Therefore, this review systematically summarizes current knowledge of soil viruses through an examination of research methods, spatiotemporal distribution, and ecological functions. Our review indicates that current progress of soil viruses remains constrained by technological inconsistencies and difficulties in viral isolation techniques within complex soil matrices. Therefore, viral distribution analyses are largely limited to small-scale sections of agricultural land, forest, pastureland, and grassland. There is insufficient exploration of viral distribution across large-scale geographic areas and desert soil environments, as well as RNA virus diversity. The characteristics of soil viral communities are primarily influenced by environmental factors such as temperature, moisture, and pH. Overall, we conclude that soil viruses are pivotal drivers of microbial community dynamics and biogeochemical cycling, although our comprehensive understanding is severely bottlenecked by complex soil matrices and inconsistent viral isolation methodologies. Future research should focus on methodological innovations such as long-read sequencing and single-cell approaches to decipher virus–host interaction networks and their ecological roles across large-scale and extreme environments.