I have been influenced to decide that the environment around the area in which a reaction is taking place has some influence on the reation and possibly the alchemist itself based on the research of a man named HitokoriNero...

"Nero's First Law of Elemental/Environmental Pull": The [four base] elements, and sometimes other forms of prima materia, in the surrounding environment play an effective and crusial role in alchemic processes.

"Nero's Second Law of Elemental/Environmental Pull":Based on a person's zodiac sign, birthdate, preference, childhood, training, and/or personal beliefs, a person might show higher alchemic prowess and/or overall advantage in a specific environment.

Beaches
At beach areas, there is a high concentration of all four elements. They intermingle with each other and the constant battle of elements conquring over other elements can be seen if payed close atention to. The high concentration is posibly the reason to attract so many of our own species (see 2nd law, above).

Deserts
Deserts are one of the most harshest environments in the world. It fully embraces te fire element and attempts to stagnate the others. Deserts are mostly avoided because of the fire element's tendancies to destroy anything that attempts to aquire it's power.

Churches, monestaries, other religious sites
When you step into these locations, there is some large spiritual enrichness that a sensitive alchemist can feel. Because spirituality can only be represented by the four elements but no measured, it is apparent that the alchemic pull is of a prima materia that hasn't been identified yet. Athiest alchemist are at a severe disadvantage in this environment (As a side note, athiest alchemists are at another disadvantage in that they can not recieve the advantages of spiritual heightening. This nearly defetes the purpose of alchemy as a whole) .

Open Plains
For the few open plains that exist in this age, the air element thrives in this zone. Without trees, buildings, or other erected structures in the way, the wind is free to blow through this environment.

Caves
Caves are characterized by their heavy aquaitnance with the earth element. For the alchemist that majors in using earth alchemy it is not suggested to battle in this area as caves are usualy unstable and collapse easily.

Bodies of water
Oceans, lakes, rivers, streams, etc., all of which benefit from the enormity of water. It would be wise to exert causion near the larger bodies of water. An experiment or a battle can take place somewhere else and at another time, a human life, however, is much more difficult to ressurect once it has drowned.