Unfortunately Mono 3.2.8 does not have the System.Diagnostics.Tracing.dll as part of its full .NET framework implementation.
However should be able to workaround this by copying the PCL version of the System.Diagnostics.Tracing.dll into your project and referencing that. This assumes you are not actually using any of the System.Diagnostics.Tracing.dll in your project since the PCL library may not have any implementation.
With Mono 3.4.0 installed you can copy one of the System.Diagnostics.Tracing.dll files. To test everything worked I copied the following file into my project:
/Library/Frameworks/Mono.framework/Versions/3.4.0/lib/mono/xbuild-frameworks/.NETPortable/v4.5/System.Diagnostics.Tracing.dll
This is on the Mac. You will need to find the file since the location will be different on Linux and it may be in different location in Mono 3.2.8. It seems to be in Profile7 which should be included with Mono 3.2.8. The .dll is also available from Microsoft in the Portable Library Reference Assemblies download. Unfortunately that download requires Windows to be able to install a .zip file with the portable library dlls.
The file was copied into the project since you cannot browse to it with Xamarin Studio whilst adding a reference. This is because it is in a directory that is hidden because the directory starts with a dot.
Directly referencing the System.Diagnostics.Tracing.dll in my project I could get Microsoft's example DataFlow code working.