diff --git a/CHANGELOG.md b/CHANGELOG.md
index a5b34b3a0..027adda2d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,14 @@
 # AtChem2 - CHANGELOG
 
+## v1.2.1 (January 2021)
+
+- new environment variable `ASA` (aerosol surface area)
+- fix bug in the C-binding for `gfortran` version 9 and above
+- remove tabs from the configuration files
+- update the Travis configuration file
+- tidy the comments and printout messages of various source files
+- update the manual
+
 ## v1.2 (May 2020)
 
 - implement argument parser and named arguments for the  `atchem2` executable
@@ -20,7 +29,7 @@
 - new script to set the version of AtChem2 before a release (`tools/version.sh`)
 - minor improvements to the install procedure
 - move the example chemical mechanism file to the `mcm`/ directory, and add a minimal .fac file (`mechanism_skel.fac`)
-- tidy and improve comments of various source files and scripts
+- tidy and improve comments in various source files and scripts
 - minor fixes and updates
 
 ## v1.1.1 (January 2019)
diff --git a/doc/AtChem2-Manual.pdf b/doc/AtChem2-Manual.pdf
index 1744e11f0..daf87ef67 100644
Binary files a/doc/AtChem2-Manual.pdf and b/doc/AtChem2-Manual.pdf differ
diff --git a/doc/latex/AtChem2-Manual.tex b/doc/latex/AtChem2-Manual.tex
index e9893dd30..cb82730f8 100644
--- a/doc/latex/AtChem2-Manual.tex
+++ b/doc/latex/AtChem2-Manual.tex
@@ -51,7 +51,7 @@
   \hspace{0.05\textwidth}
   % Box for the title page text
   \parbox[b]{0.75\textwidth}{
-    {\Huge\bfseries AtChem2\\[0.5\baselineskip] v1.3-dev}\\[2\baselineskip]  % Title
+    {\Huge\bfseries AtChem2\\[0.5\baselineskip] v1.2.1}\\[2\baselineskip]  % Title
     {\LARGE\textit{User Manual}}\\[4\baselineskip]  % Subtitle
     {\Large\textsc{R. Sommariva\\S. Cox}}  % Author(s)
     \vspace{0.5\textheight}\\
diff --git a/doc/latex/Installation.tex b/doc/latex/Installation.tex
index f21b6f604..58b862c0a 100644
--- a/doc/latex/Installation.tex
+++ b/doc/latex/Installation.tex
@@ -22,12 +22,12 @@ \section{Requirements} \label{sec:requirements}
 
 \begin{itemize}
 \item Fortran -- the model compiles with GNU \texttt{gfortran}
-  (version 4.8.5) and with Intel \texttt{ifort} (version 17.0)\\
+  (version 4.8 and above) and with Intel \texttt{ifort} (version 17.0)\\
   $\hookrightarrow$ default compiler: \texttt{gfortran}
 \item Python~\footnote{All Python scripts used in AtChem2 work equally
-    with Python v2 and v3. Support for Python v2 may be removed in
-    future versions of AtChem2.}
-\item cmake
+  with Python v2 and v3. Support for Python v2 will be removed in
+  future versions of AtChem2.}
+\item make and cmake
 \item Ruby (optional)
 \end{itemize}
 
@@ -38,9 +38,9 @@ \section{Requirements} \label{sec:requirements}
 AtChem2 has the following dependencies:
 
 \begin{itemize}
+\item BLAS and LAPACK
 \item CVODE
 \item openlibm
-\item BLAS and LAPACK
 \item numdiff (optional)
 \item FRUIT (optional)
 \end{itemize}
@@ -99,9 +99,10 @@ \section{Dependencies} \label{sec:dependencies}
 anywhere and given any name. In this manual, the \depdir\ is
 assumed to be: \texttt{\$HOME/atchem-lib/}.
 
-Before installing the dependencies, make sure that a Fortran compiler,
-Python, cmake and (optionally) Ruby are installed on the operating
-system, as explained in Sect.~\ref{sec:requirements}.
+Before installing the dependencies, make sure that a Fortran compiler
+(e.g., \texttt{gfortran}), Python, make, cmake and (optionally) Ruby
+are installed on the operating system, as explained in
+Sect.~\ref{sec:requirements}.
 
 \subsection{Required dependencies} \label{subsec:required-dependencies}
 
diff --git a/src/atchem2.f90 b/src/atchem2.f90
index 7d02437f6..3b0571085 100644
--- a/src/atchem2.f90
+++ b/src/atchem2.f90
@@ -150,7 +150,7 @@ end subroutine FCVFUN
   rout(:) = -1.0_DP
   rpar(:) = -1.0_DP
 
-  write (*, '(A)') 'AtChem2 v1.3-dev'
+  write (*, '(A)') 'AtChem2 v1.2.1'
   write (*,*)
   write (*, '(A)') '-------------'
   write (*, '(A)') ' Directories'
diff --git a/tools/version.sh b/tools/version.sh
index 6014fc3e7..bd4145ae1 100755
--- a/tools/version.sh
+++ b/tools/version.sh
@@ -14,8 +14,8 @@
 #
 # N.B.: the script MUST be run from the main directory of AtChem2.
 
-VERS_OLD="v1.2"
-VERS_NEW="v1.3-dev"
+VERS_OLD="v1.3-dev"
+VERS_NEW="v1.2.1"
 
 find ./ -type f ! -name "version.sh" -print | xargs perl -pi -e "s/$VERS_OLD/$VERS_NEW/g"
 
diff --git a/travis/tests/firstorder/firstorder.out.cmp b/travis/tests/firstorder/firstorder.out.cmp
index ab87eb236..6c5f2d86e 100644
--- a/travis/tests/firstorder/firstorder.out.cmp
+++ b/travis/tests/firstorder/firstorder.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/secondorder/secondorder.out.cmp b/travis/tests/secondorder/secondorder.out.cmp
index a04bc4bac..ebb8c0862 100644
--- a/travis/tests/secondorder/secondorder.out.cmp
+++ b/travis/tests/secondorder/secondorder.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/short/short.out.cmp b/travis/tests/short/short.out.cmp
index 377552876..4dbd1f488 100644
--- a/travis/tests/short/short.out.cmp
+++ b/travis/tests/short/short.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/short_dense/short_dense.out.cmp b/travis/tests/short_dense/short_dense.out.cmp
index f6d80ba17..bbbb248eb 100644
--- a/travis/tests/short_dense/short_dense.out.cmp
+++ b/travis/tests/short_dense/short_dense.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/short_end_of_day/short_end_of_day.out.cmp b/travis/tests/short_end_of_day/short_end_of_day.out.cmp
index bbc4fb39b..a9e2fd4ec 100644
--- a/travis/tests/short_end_of_day/short_end_of_day.out.cmp
+++ b/travis/tests/short_end_of_day/short_end_of_day.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/short_ext1/short_ext1.out.cmp b/travis/tests/short_ext1/short_ext1.out.cmp
index 95f0b7757..49633cec4 100644
--- a/travis/tests/short_ext1/short_ext1.out.cmp
+++ b/travis/tests/short_ext1/short_ext1.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/short_ext2/short_ext2.out.cmp b/travis/tests/short_ext2/short_ext2.out.cmp
index 1b1c73751..0e38d59b3 100644
--- a/travis/tests/short_ext2/short_ext2.out.cmp
+++ b/travis/tests/short_ext2/short_ext2.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/short_ext3/short_ext3.out.cmp b/travis/tests/short_ext3/short_ext3.out.cmp
index 04093e8ba..260ba59c2 100644
--- a/travis/tests/short_ext3/short_ext3.out.cmp
+++ b/travis/tests/short_ext3/short_ext3.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/short_ext4/short_ext4.out.cmp b/travis/tests/short_ext4/short_ext4.out.cmp
index c3ffaf215..e953eef5c 100644
--- a/travis/tests/short_ext4/short_ext4.out.cmp
+++ b/travis/tests/short_ext4/short_ext4.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/short_no_pre/short_no_pre.out.cmp b/travis/tests/short_no_pre/short_no_pre.out.cmp
index ffeb6f197..db7c679dc 100644
--- a/travis/tests/short_no_pre/short_no_pre.out.cmp
+++ b/travis/tests/short_no_pre/short_no_pre.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/spec_no_env_yes1/spec_no_env_yes1.out.cmp b/travis/tests/spec_no_env_yes1/spec_no_env_yes1.out.cmp
index 5ec21338f..2246c3d34 100644
--- a/travis/tests/spec_no_env_yes1/spec_no_env_yes1.out.cmp
+++ b/travis/tests/spec_no_env_yes1/spec_no_env_yes1.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/spec_no_env_yes2/spec_no_env_yes2.out.cmp b/travis/tests/spec_no_env_yes2/spec_no_env_yes2.out.cmp
index 95355cc31..6a2b6bbb6 100644
--- a/travis/tests/spec_no_env_yes2/spec_no_env_yes2.out.cmp
+++ b/travis/tests/spec_no_env_yes2/spec_no_env_yes2.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/spec_yes_env_no/spec_yes_env_no.out.cmp b/travis/tests/spec_yes_env_no/spec_yes_env_no.out.cmp
index b29922a3e..264425932 100644
--- a/travis/tests/spec_yes_env_no/spec_yes_env_no.out.cmp
+++ b/travis/tests/spec_yes_env_no/spec_yes_env_no.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/spec_yes_env_no_with_jfac/spec_yes_env_no_with_jfac.out.cmp b/travis/tests/spec_yes_env_no_with_jfac/spec_yes_env_no_with_jfac.out.cmp
index 5ce101581..66ba5a31d 100644
--- a/travis/tests/spec_yes_env_no_with_jfac/spec_yes_env_no_with_jfac.out.cmp
+++ b/travis/tests/spec_yes_env_no_with_jfac/spec_yes_env_no_with_jfac.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/spec_yes_env_no_with_jfac_fail1/spec_yes_env_no_with_jfac_fail1.out.cmp b/travis/tests/spec_yes_env_no_with_jfac_fail1/spec_yes_env_no_with_jfac_fail1.out.cmp
index f20445cdc..acecf8fe3 100644
--- a/travis/tests/spec_yes_env_no_with_jfac_fail1/spec_yes_env_no_with_jfac_fail1.out.cmp
+++ b/travis/tests/spec_yes_env_no_with_jfac_fail1/spec_yes_env_no_with_jfac_fail1.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/spec_yes_env_no_with_jfac_fixed/spec_yes_env_no_with_jfac_fixed.out.cmp b/travis/tests/spec_yes_env_no_with_jfac_fixed/spec_yes_env_no_with_jfac_fixed.out.cmp
index 4b7b1087e..0e67e376e 100644
--- a/travis/tests/spec_yes_env_no_with_jfac_fixed/spec_yes_env_no_with_jfac_fixed.out.cmp
+++ b/travis/tests/spec_yes_env_no_with_jfac_fixed/spec_yes_env_no_with_jfac_fixed.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/spec_yes_env_no_with_photo/spec_yes_env_no_with_photo.out.cmp b/travis/tests/spec_yes_env_no_with_photo/spec_yes_env_no_with_photo.out.cmp
index 432967e95..47e8fd3eb 100644
--- a/travis/tests/spec_yes_env_no_with_photo/spec_yes_env_no_with_photo.out.cmp
+++ b/travis/tests/spec_yes_env_no_with_photo/spec_yes_env_no_with_photo.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/spec_yes_env_yes/spec_yes_env_yes.out.cmp b/travis/tests/spec_yes_env_yes/spec_yes_env_yes.out.cmp
index 2eddfba10..9c36a4521 100644
--- a/travis/tests/spec_yes_env_yes/spec_yes_env_yes.out.cmp
+++ b/travis/tests/spec_yes_env_yes/spec_yes_env_yes.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/spec_yes_plus_fixed_env_no/spec_yes_plus_fixed_env_no.out.cmp b/travis/tests/spec_yes_plus_fixed_env_no/spec_yes_plus_fixed_env_no.out.cmp
index 01fb87b43..0a9674227 100644
--- a/travis/tests/spec_yes_plus_fixed_env_no/spec_yes_plus_fixed_env_no.out.cmp
+++ b/travis/tests/spec_yes_plus_fixed_env_no/spec_yes_plus_fixed_env_no.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories
diff --git a/travis/tests/static/static.out.cmp b/travis/tests/static/static.out.cmp
index 1c8643fda..c3c78b540 100644
--- a/travis/tests/static/static.out.cmp
+++ b/travis/tests/static/static.out.cmp
@@ -1,4 +1,4 @@
-AtChem2 v1.3-dev
+AtChem2 v1.2.1
 
 -------------
  Directories