Analysis of research hotspots and trends in groundwater nitrate contamination

Groundwater nitrate contamination is a worldwide water environment problem with few phased summaries in this field. Here, 14 407 articles were selected from the Web of Science database for the years 1968—2022 to analyze the development trends and current hotspots in the field of groundwater nitrate contamination research with bibliometric visualization analysis software (VOS viewer). The results showed that: (1) The number of relevant publications has been exponentially increasing. The published journals are mainly related to environmental science and water resources, indicating an important role in this field. (2) The results from the publication institutions and funding institutions show that more than half of the total number of articles from the top ten publication institutions and funding institutions are from the United States and China. (3) The main issues in groundwater nitrate contamination research can be summarized as four subsets: source tracing, migration and transformation mechanisms, pollution remediation, and risk assessment. Among them, pollution remediation has the most keywords, demonstrating the importance of this research area. (4) From 1990 to 2014, the research hotspots in groundwater nitrate research were mainly focused on source tracing and migration and transformation mechanisms. Specifically, the main topic was the identification of nitrate pollution sources during the stage from 1990 to 1998, while the focus shifted to the methods for identifying nitrate pollution sources from 1999 to 2014, with isotopes and models being particularly effective. For the recent stage from 2015 to 2022, the research hotspots have shifted to risk assessment. The bibliometric analysis results in the field of groundwater nitrate pollution can provide some reference for the direction of this field.