diff --git a/bld/build-namelist b/bld/build-namelist
index 258b54f048..7a5ec905eb 100755
--- a/bld/build-namelist
+++ b/bld/build-namelist
@@ -2285,7 +2285,7 @@ if ($chem eq 'trop_mam3') {
 if ($phys =~ /cam6/ or $phys =~ /cam7/) {
 
     # OASISS (ocean) DMS emissions
-    if (!$aqua_mode and !$scam) {
+    if (!$aqua_mode and !$scam and chem_has_species($cfg, 'DMS')) {
         my $rel_filepath = get_default_value('dms_ocn_emis_file');
         my $abs_filepath = set_abs_filepath($rel_filepath, $inputdata_rootdir);
         my $val = quote_string("DMS -> ". $abs_filepath);
diff --git a/bld/namelist_files/namelist_defaults_cam.xml b/bld/namelist_files/namelist_defaults_cam.xml
index ab4a8e28f8..5c9187be4f 100644
--- a/bld/namelist_files/namelist_defaults_cam.xml
+++ b/bld/namelist_files/namelist_defaults_cam.xml
@@ -2994,9 +2994,6 @@
 <fv_nsplit hgrid="0.9x1.25" waccm_phys="1">16</fv_nsplit>
 <fv_nsplit hgrid="0.47x0.63"    waccmx="1">32</fv_nsplit>
 
-<fv_nspltvrm hgrid="1.9x2.5" waccm_phys="1" aquaplanet="1">4</fv_nspltvrm>
-<fv_nspltrac hgrid="1.9x2.5" waccm_phys="1" aquaplanet="1">4</fv_nspltrac>
-
 <fv_del2coef                >3.e+5</fv_del2coef>
 
 <fv_filtcw                  >0</fv_filtcw>
diff --git a/src/physics/cam/nucleate_ice.F90 b/src/physics/cam/nucleate_ice.F90
index ac7268c068..42db39a083 100644
--- a/src/physics/cam/nucleate_ice.F90
+++ b/src/physics/cam/nucleate_ice.F90
@@ -226,9 +226,11 @@ subroutine nucleati(  &
 
          if ( ((tc.le.0.0_r8).and.(tc.ge.-37.0_r8).and.(qc.lt.1.e-12_r8)).or.(tc.le.-37.0_r8)) then
 
-            A = -1.4938_r8 * log(soot_num+dst_num) + 12.884_r8
-            B = -10.41_r8  * log(soot_num+dst_num) - 67.69_r8
-            regm = A * log(wbar1) + B
+            if ( (soot_num+dst_num) > 0._r8)   then
+               A = -1.4938_r8 * log(soot_num+dst_num) + 12.884_r8
+               B = -10.41_r8  * log(soot_num+dst_num) - 67.69_r8
+               regm = A * log(wbar1) + B
+            end if
 
             ! heterogeneous nucleation only
             if (tc .gt. regm .or. so4_num < 1.0e-10_r8) then
@@ -260,8 +262,11 @@ subroutine nucleati(  &
                   nihf = 0._r8
                   n1   = niimm + nidep
 
-                  osoot_num = soot_num * (niimm + nidep) / (soot_num + dst_num)
-                  odst_num  = dst_num  * (niimm + nidep) / (soot_num + dst_num)
+                  if ( (soot_num+dst_num) > 0._r8)   then
+                     osoot_num = soot_num * (niimm + nidep) / (soot_num + dst_num)
+                     odst_num  = dst_num  * (niimm + nidep) / (soot_num + dst_num)
+                  end if
+
                endif
 
             ! homogeneous nucleation only
@@ -322,8 +327,10 @@ subroutine nucleati(  &
                      oso4_num  = nihf
                   endif
 
-                  osoot_num = soot_num * (niimm + nidep) / (soot_num + dst_num)
-                  odst_num  = dst_num  * (niimm + nidep) / (soot_num + dst_num)
+                  if ( (soot_num+dst_num) > 0._r8)   then
+                     osoot_num = soot_num * (niimm + nidep) / (soot_num + dst_num)
+                     odst_num  = dst_num  * (niimm + nidep) / (soot_num + dst_num)
+                  end if
 
                   nihf      = nihf      * fhom * ((regm - tc) / 5._r8)**2
                   oso4_num  = oso4_num  * fhom * ((regm - tc) / 5._r8)**2
@@ -582,4 +589,3 @@ subroutine frachom(Tmean,RHimean,detaT,fhom)
 end subroutine frachom
 
 end module nucleate_ice
-