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Rationale: The development of analytical screening techniques for pesticides is crucial for preventing and mitigating environmental contamination. Mass spectrometry‐based screening methods differ based on the complexity of the sample matrix and the diversity of the target compounds. One of the major challenges is balancing cost reduction in the extraction process with the optimization of analytical results. This protocol introduces a universal and efficient scheme for the qualitative and quantitative schemes for 45 pesticides within a single analytical run. Methods: Water samples were extracted using an SPE column, with the pH adjusted to 7. Soil samples were processed using a modified QuEChERS method. The pretreatment for water samples emphasized selecting appropriate SPE columns and optimizing pH, while for soil samples, the focus was on choosing suitable extraction solvents and extraction salt packages. The enriched samples were then analyzed using liquid chromatography–tandem mass spectrometry (LC–MS/MS). The method was evaluated for accuracy, precision, detection limits, and matrix effects. Results: The method enabled the simultaneous detection of 45 pesticides within a 15‐minute analysis period. SPE recoveries ranged from 56.1% to 118.8%. Instrumental detection limits varied between 0.02 and 1 pg, while method detection limits extended from 0.05 to 18.47 ng/l in soil and water matrices. The approach was successfully applied to water and soil samples, with the pesticide concentration ranging from 0.1 ng/L to 38 μg/L. Conclusions: The protocol substantially enhances the characterization and quantification of 45 pesticides in environmental samples, achieving a remarkable reduction in detection limits by an order of magnitude compared to previous research. This method enables the simultaneous detection of pesticides in both water and soil matrices using a single system, addressing the challenges of using separate systems for different environmental media. Furthermore, this protocol provides a crucial theoretical foundation for managing and safeguarding against pesticide pollution. [ABSTRACT FROM AUTHOR]

The exchange and transformation of dissolved organic matter (DOM) at the sediment–water interface are crucial factors in regulating watershed biogeochemistry, with the molecular composition of DOM serving as a pivotal determinant in elucidating this process. High-resolution mass spectrometry (HRMS) is an effective tool for resolving the composition of DOM. By analyzing the compositional characteristics of DOM at the sediment–water interface under three different salinities at the same latitude region in northern China, the findings indicate certain variations in component characteristics of DOM between low-salinity inland waters and high-salinity seawaters, with the former exhibiting greater molecular diversity and higher molecular weights, whereas the latter displayed a higher saturation and bioavailability. Notably, the presence of more CHOS substances in the low-salinity inland waters underscores the transformation of the DOM influenced by terrestrial inputs and anthropogenic activities. Conversely, the presence of more CHO and CHNO substances in high-salinity seawater underscores the microbial effects. The chemical transformation process from overlying water to pore water to sediments was characterized by methylation, hydrogenation, decarboxylation, and reduction, as determined by calculating the relations between the H/C and O/C ratios of different compound types. These findings indicate that HRMS can yield more refined results in revealing the process of DOM at the sediment–water interface under different environments, which provides a more reliable basis for a deeper understanding of the source–sink mechanism of sediment organic matter. [ABSTRACT FROM AUTHOR]

Rationale: The sources and chemical compositions of organic aerosol (OA) exert a significant influence on both regional and global atmospheric conditions, thereby having far‐reaching implications on environmental chemistry. However, existing mass spectrometry (MS) methods have limitations in characterizing the detailed composition of OA due to selective ionization as well as fractionation during cold‐water extraction and solid‐phase extraction (SPE). Methods: A comprehensive MS study was conducted using aerosol samples collected on dusty, clean, and polluted days. To supplement the data obtained from electrospray ionization (ESI), a strategy for analyzing OAs collected using the quartz fiber filter directly utilizing laser desorption ionization (LDI) was employed. Additionally, the ESI method was conducted to explore suitable approaches for determining various OA compositions from samples collected on dusty, clean, and polluted days. Results: In situ LDI has the advantages of significantly reducing the sample volume, simplifying sample preparation, and overcoming the problem of overestimating sulfur‐containing compounds usually encountered in ESI. It is suitable for the characterization of highly unsaturated and hydrophobic aerosols, such as brown carbon‐type compounds with low volatility and high stability, which is supplementary to ESI. Conclusions: Compared with other ionization methods, in situ LDI helps provide a complementary description of the molecular compositions of OAs, especially for analyzing OAs in polluted day samples. This method may contribute to a more comprehensive MS analysis of the elusive compositions and sources of OA in the atmosphere. [ABSTRACT FROM AUTHOR]

Extensive reservoir construction has fragmented more than 70% of the world's rivers, significantly impacting river connectivity and carbon cycling. However, the response of riverine dissolved organic matter (DOM) to reservoir influence and its potential downstream effects remains unclear. In this study, we employed multiple analytical techniques, including Fourier transform ion cyclotron resonance mass spectrometry, radiocarbon dating, and environmental factor analysis, to investigate the dynamic changes in DOM and its controlling factors under different hydrological management regimes in the LongTan Reservoir, the largest reservoir in the Pearl River, which is the second largest river in China by water discharge. Our results indicate that the molecular diversity of riverine DOM is reduced in the reservoir. Oxygen‐rich and heteroatomic compounds, such as those containing nitrogen, sulfur, and phosphorus, are preferentially removed through enhanced photo‐ and biodegradation processes in the reservoir, particularly during the storage period. This leads to DOM that is enriched with oxygen‐poor compounds and shows a biodegraded Δ14C value downstream. This study highlights that the composition of riverine DOM is significantly altered by the reservoir, but these effects could potentially be mitigated by optimizing the outlet location. Plain Language Summary: The construction of dams has significantly impacted rivers worldwide, fragmenting them and disrupting the flow of water and carbon. To understand how substances in rivers, particularly dissolved organic matter (DOM), are affected by dams and their potential impact on downstream ecosystems, we studied changes in DOM and the factors controlling these changes in the largest reservoir on the Pearl River in China, the second largest river in the country by water discharge. We found that certain compounds, such as those containing nitrogen, sulfur, and phosphorus, are preferentially removed by natural processes in the reservoir. This phenomenon results in DOM with persistent properties that hinder its participation in downstream biogeochemical processes. Although the reservoir significantly alters riverine DOM, our results suggest that the impact of the reservoir could be mitigated by optimizing the water outlet location. Key Points: Primary production and degradation processes in the river will be significantly enhanced by the reservoirThe reservoir will preferentially remove oxygen‐rich and heteroatomic compounds in the riverThe impact of the reservoir on downstream systems is potentially controlled by establishing an ideal outlet location [ABSTRACT FROM AUTHOR]