Funding for this research was provided by:
Ministry of Ecology and Environment (#2019HJ2096001006)
National Natural Science Foundation of China (#31600253)
China Scholarship Council (201708515018)
Received: 23 June 2019
Accepted: 5 December 2019
First Online: 26 February 2020
Ethics approval and consent to participate
: The authors assert that all procedures contributing to this work comply with the applicable ethical standards of the relevant national and institutional committees on human experimentation and with the Helsinki Declaration of 1975, as revised in 2008. All interviews were conducted only after oral informed consent was obtained.
: Not applicable.
: The authors declare that they have no competing interests.