add some auxiliary functions in module tracer_h.F90:
is_known_tracer(tname) returns ".true." if "tname" is a known tracer
tracer_index(tname) returns the tracer index of tracer "tname"
add the possibility of "volcanic outgasing" as point sources.
controled by a "callvolcano" flag (default .false.)
details about source location and injection details (frequency, length)
need be provided in a "volcano.def" ASCII file read at runtime.
(see routine "read_volcano" in volcano.F90)