A Review of Rapid Detections for Emerging Contaminants in Groundwater

In recent years, emerging contaminants, such as antibiotics, endocrine disruptors, perfluorinated and polyfluoroalkyl substances, are of great worldwide concern. These contaminants enter the water environment through runoff, diffusion, infiltration and other ways. Due to their bioaccumulation, biological toxicity, and environmental sustainability, emerging contaminants pose a potential threat to aquatic organisms, human health, and ecological safety¹. Therefore, it is urgent to detect and investigate the pollution status of emerging contaminants in the water environment. Many investigations and evaluations have been carried out, making rapid detection methods a research hotspot. The detection methods of emerging contaminants in the water environment based on recent literature is reviewed, comparing the advantages and disadvantages of the emerging contaminants detection methods, summarizing the research progress of rapid detection technology for emerging contaminants in water, and prospecting its development trend.　　Emerging contaminants were widely detected in the water environment. For instance, antibiotics have been detected in groundwater in cities such as Harbin² and Shijiazhuang³, in surface rivers such as the Fuyang River and Qin River⁴, and in the source water such as Yichang City⁵ and the Tuojiang River Basin⁶, as well as in groundwater from major urban-rural settings of Pakistan⁸. Similarly, endocrine disruptors have been detected in different types of water in China, such as the Minjiang River Basin¹¹, as well as in groundwater of the Wuxi—Changzhou region⁹ and Xuzhou region¹⁰. Some endocrine disruptor pollutants have been detected in seawater along the Romanian Black Sea coast¹². In addition, perfluorinated and polyfluoroalkyl substances have been detected in the surface water of Beijing’s reclaimed groundwater irrigation area¹³ and in Hongze Lake¹⁵. There is perfluoroalkyl acid pollution in the groundwater environment of farmland in some regions of Hainan Province¹⁴. Perfluorinated compounds have also been detected in major Southern Indian rivers¹⁶. There are emerging contaminants in the water environment both domestically and internationally. The concentrations and detection rates are high in some areas, posing a serious threat to groundwater and surface water resources.　　Nowadays, the emerging contaminants are mainly detected in the laboratory using advanced instruments. The emerging contaminants are widely present in the environment, but their concentrations are quite low, of which the content is in the nanogram to microgram level. In order to reduce the detection limits, the emerging contaminants samples will be concentrated and then tested using high-resolution instruments. Instrument detection technology has the advantages of high throughput, high accuracy, low detection limit, and low false positive rate. While the pre-treatment of samples is very complex, and the analytical instruments used are costly, this is not something that all laboratories can afford. Therefore, the analysis of emerging contaminants takes a long time from sampling to getting analysis results.　　Sensor detection technology is a commonly used on-site detection method in the field of environmental monitoring. It mainly includes electrochemical, optical, and biological sensing. The field rapid detection of emerging contaminants in water environment is a promising research direction. Electrochemical sensing has been extensively studied. Sensor detection technology can give results in minutes for emerging contaminants. However, most of the work was focused on detecting a single contaminant; significant progress has been made in the laboratory, but it has not yet been promoted for field testing; there were fewer examples of field rapid detection of emerging contaminants. Further research is needed on the technology for simultaneously determining multiple emerging contaminants in the meantime.　　Immunoassay detection technology is suitable for on-site rapid screening of emerging contaminants in the water environment. Enzyme linked immunosorbent assay can preliminarily screen for the emerging contaminants in the water environment, while immunochromatography can perform qualitative or semi-quantitative detection of emerging contaminants. Immunoassay technology has high specificity, strong sensitivity, simplicity, convenience, and no need for expensive instruments. It has great advantages in rapid detection of large amounts of samples and on-site detection. However, it is prone to false negatives and positives⁸⁹.　　There are various types of rapid detection methods for emerging contaminants. Further, the focus of research should be on utilizing new materials to improve traditional detection methods to meet the needs of rapid and on-site detection of contaminants. Besides, researchers could combine multiple detection techniques to make detection methods simpler, faster, and more cost-effective, and with high sensitivity and accuracy to achieve rapid detection of multiple pollutants simultaneously.