Analysis and Risk Assessment of Organic Pollutants in Surface Water from Xujiahe Basin, China

Review of scientific literature on available methods of assessing organochlorine pesticides in the environment

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs) widely used in agriculture and industry, causing serious health and ecological consequences upon exposure. This review offers a thorough overview of OCPs analysis emphasizing the necessity of ongoing work to enhance the identification and monitoring of these POPs in environmental and human samples. The benefits and drawbacks of the various OCPs analysis techniques including gas chromatography-mass spectrometry (GC-MS), gas chromatography-electron capture detector (GC-ECD), and liquid chromatography-mass spectrometry (LC-MS) are discussed. Challenges associated with validation and optimization criteria, including accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ), must be met for a method to be regarded as accurate and reliable. Suitable quality control measures, such as method blanks and procedural blanks, are emphasized. The LOD and LOQ are critical quality control measure for efficient quantification of these compounds, and researchers have explored various techniques for their calculation. Matrix interference, solubility, volatility, and partition coefficient influence OCPs occurrences and are discussed in this review. Validation experiments, as stated by European Commission in document SANTE/11813/2017, showed that the acceptance criteria for method validation of OCP analytes include ≤20 % for high precision, and 70-120 % for recovery. This may ultimately be vital for determining the human health risk effects of exposure to OCP and for formulating sensible environmental and public health regulations.

Screening and Risk Evaluation of Organic Contaminants in an Urban Wetland Fed with Wastewater Effluents

Wastewater release in an urban wetland in Mexico City entails discharging complex mixtures of hundreds of chemical substances into the aquatic system. Therefore, in order to identify the most important contaminants, a GC-MS screening method coupled with deconvolution software was used. LC₅₀ values from ECOSAR and Toxic Units were obtained to identify the organic pollutants-of-concern and to pinpoint the most ecotoxic sites. The results showed that, even though the area has intensive farming, agrochemicals are not of concern. Industrial and domestic groups make up from about 30%-66% of the pollutants for all sites. Of the 189 identified substances, 17 were detected 44% of the time and the Toxic Unit showed that terbutol, coprostanol, and hexadecane were capable of generating considerable adverse effects on the aquatic ecosystem. Total Toxic Units for each site exhibited a decreasing trend as they distanced from the urban and agricultural area.

A batch microfabrication of a microfluidic electrochemical sensor for rapid chemical oxygen demand measurement

Chemical oxygen demand (COD) is one of the key water quality parameters in environmental monitoring. However, fabricating a COD sensor with the characteristic of batch-processing and rapid measurement is always a challenging issue. This paper reports a microfluidic electrochemical sensor for the organic matter measurement based on advanced oxidization within a fixed microvolume detection chamber by a microfabrication technique/MEMS. By fabricating a silicon-based Ag/AgCl reference electrode and employing PbO₂ as the working electrode with Pt as the counter electrode, we verified the superiority of the as-fabricated sensor by continuous potassium acid phthalate detection; an acceptable limit of detection (4.17 mg L^-1-200 mg L^-1), a low limit of detection (2.05 mg L^-1), a desirable linearity (R² = 0.982) and relative stability at different pH values and Cl^- concentrations was witnessed. Particularly, a shorter detection time (2 s) was witnessed for the as-proposed sensor compared with traditional organic matter measurement methods. Each sensing process takes only 2 seconds for sensing because a micro-cavity with a volume of 2.5 μL was fabricated and used as a detection pool. Moreover, as the sensor was fabricated by a mass-production technique, potential response consistency of multiple sensors was expected and was verified via a series of parallel experiments. In this paper, a miniaturized (8 mm × 10 mm), low-cost and reliable COD sensor was designed and fabricated by MEMS, and it provided a core sensor component for construction of an online water environment monitoring network to meet the substantial demand for COD sensors in the Internet of Things (IOT) era.