Fig. 3.

The co-occurrence network map of the research keywords relevant to brownfields from Web of Science, with 1506 publication records downloaded from Web of Science from 1968 to 2020, integrated into this analysis. The colour of a keyword was determined by the cluster to which the keyword belonged. Lines between keywords represent links, and 1000 lines were displayed at most to avoid the overlapping of keywords, representing the 1000 most occurrences between keywords. The size of the label and the circle of a keyword were determined by the occurrence of the keyword. The higher the occurrence of a keyword, the larger the label and the circle of the keyword.