基于CiteSpace的岩溶地下水硝酸盐示踪研究进展

Research progress of nitrate tracing in karst groundwater based on CiteSpace

硝酸盐(NO_(3)^(-))是地下水中主要的污染物之一,其浓度一旦超标,将会对水生态和人类健康产生不良影响。文章分析2003-2022年岩溶地下水硝酸盐来源的同位素示踪进展,在中国知网(CNKI)收录的全部期刊数据库检索,以“岩溶地下水”“岩溶含水层”“喀斯特地下水”“喀斯特含水层”“硝酸盐”“硝态氮”“氮同位素”“氧同位素”“MixSIAR”“硝酸盐源”“氮转化”“硝酸盐污染”“硝酸盐双同位素”为主题词,得到1191篇论文;并在Web of Science(WOS)核心合集数据库中以“karst groundwater”“karst aquifer”“nitrate”“NOx-N”“nitrogen isotope”“oxygen isotope”“MixSIAR”“nitrate source”“nitrogen transformation”“nitrate contamination”和“dual nitrate isotopes”为主题词,得到2232篇文献。利用知识网络分析软件CiteSpace,对检索到的文献进行统计和研究热点分析。结果表明:在中文文献方面,中国地质科学院岩溶地质研究所在国内岩溶地下水硝酸盐研究领域优势巨大,中文文献发文量最多;关键词聚类知识图谱可概括为岩溶水文与水资源、水化学与水环境、岩溶地下水硝酸盐污染溯源3个研究热点;在英文文献方面,美国、中国和德国的发文数量最多,存在较为密切的合作关系。从研究单位来看,中国科学院的发文量最多;英文关键词聚类知识图谱可以概括为岩溶生态与水文、岩溶地下水硝酸盐的转化(氮循坏)、岩溶地下水硝酸盐污染溯源3个研究热点。硝酸盐氮氧同位素技术为岩溶地下水硝酸盐溯源与生物地球化学研究提供了强有力的支持;在定量溯源时,应考虑同位素分馏效应,以提高结果的准确性。

Nitrate(NO_(3)^(-))is one of the main pollutants in groundwater;therefore,once NO_(3)^(-)concentrations exceed an acceptable level,it will have adverse effects on water ecology and human health.Identifying the sources and biogeochemical transformation process of nitrate in groundwater is of important theoretical and practical significance for pollution prevention and control.The karst groundwater system is characterized by high vulnerability.At present,studies on nitrate in karst groundwater based on nitrogen and oxygen isotope technology have made great progress but most of them were presented by case study,lacking a systematic summary of research progress.CiteSpace,the software of knowledge network analysis,uses bibliometrics and visualization methods,co-citation network,association rules,cluster analysis to analyze the research hotspots in a field in Chinese and foreign literature.CiteSpace enables readers to better understand the knowledge framework,research topics and future hot topics,and plays a very good role in promoting the analysis of research progress in different professional fields.To investigate the research progress of isotope tracing of nitrate sources in karst groundwater in recent years(from 2003 to 2022),and comprehensively analyze the research hotspots of nitrate in karst groundwater,"karst groundwater","karst aquifer","nitrate","nitrate-nitrogen","nitrogen isotope","oxygen isotope","MixSIAR","nitrate sources","nitrogen transformations","nitrate pollution",and"dual nitrate isotopes"were selected as subject terms in CNKI,and 1,191 papers were retrieved after the unrelated subject terms had been excluded.Meanwhile,subject terms of"karst groundwater","karst aquifer","nitrate","NOx-N","nitrogen isotope","oxygen isotope""MixSIAR","nitrate source","nitrogen transformation","nitrate contamination",and"dual nitrate isotopes"were searched in Web of Science(WOS)core collection database,and a total of 2,232 papers were retrieved.CiteSpace was employed to analyze publishing institutions,authors,keywords and research hotspots,and co-citations of both the retrieved Chinese literature and English literature.The results show that the Institute of Karst Geology of the Chinese Academy of Geological Sciences had a great advantage in studies of nitrate in karst water system,because this institute has published the largest number of academic papers written in Chinese.The keyword clustering of"#1 karst groundwater","#2 karst water","#5 karst water resources","#6 karst hydrological model"and"#11 karst aquifer"can be summarized as a research hotspot of karst hydrology and water resources.The keyword clustering of"#7 hydrogeochemistry","#8 hydrochemistry"and"#10 hydrochemical characteristics"can be summarized as a research hotspot of karst hydrochemistry and water environment.The keyword clustering of"#0 nitrate pollution","#3 karst","#4 groundwater","#9 stable isotope","#12 nitrogen and oxygen isotope"and"#13 source analysis"can be summarized as a research hotspot of nitrate pollution tracing in karst groundwater.In terms of English literature,the United States,China and Germany had the largest number of publications,and there was a relatively close cooperative relationship between them.Academic papers published by the Chinese Academy of Sciences ranked top among the researching institutes.The keyword clustering of"#0 karst","#5 macrophytes","#6 ecohydrology","#11 karst hydrology"and"#3 groundwater recharge"can be summarized as a research hotspot of karst ecology and hydrology research.The keyword clustering of"#10 groundwater","#2 nitrogen cycle","#9 nitrogen"and"#8 karst water"can be summarized as a research hotspot of nitrate transformation in karst groundwater(nitrogen cycle).The keyword clustering of"#1 source appointment","#12 nitrate pollution","#4 delta n15","#7 stable isotope"and"#13 nitrogen isotope"can be summarized as a research hotspot of nitrate pollution tracing in karst groundwater.The technology of dual nitrate isotopes provides a strong technical support for the research of nitrate tracing and biogeochemistry in karst groundwater.Isotopic fractionation effect should be considered to improve the accuracy of nitrate pollution tracing results.This paper aims to provide reference for the source tracing and effective prevention of nitrate pollution in karst groundwater in the future.