Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
The box plots of δ15N values of NO3− from different sources. Note: (1) data source: literature [39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71]; number of samples: atmospheric deposition NO3−: n = 61; manure: n = 58; sewage: n = 24; soil nitrogen: n = 23; NO3− chemical fertilizer: n = 18; NH4+ chemical fertilizer: n = 117; atmospheric deposition NH4+: n = 31.
