Tangible usually means you can touch something. For example, Air is not tangible, but is still part of the physical environment. 

If you're wondering about using English words, the website StackExchange/English would be useful for you, more so than ResearchGate. 

http://english.stackexchange.com/

Hello Dear, like mention before for John about Tangible mean you can be touch it, Also is use for countable purpose.  " Physical is more  relating to that which is material:

the physical universe; the physical sciences."(from Dictionary.com). for that reason you are writing about Physical Environment .   From my point of view Physical is more deep relate to material and Tangible to monetary purpose.

Hi,

Physical environment is related to the resources of the three spheres (hydrosphere, atmosphere, lithosphere), however, tangible environment is related to the quality of the environmental system (air quality, water quality, soil quality etc). Thus, tangible environemt implies the bio effect (poitive or negative) on any physical system (3-spheres).

Hello

Complementing what Motasem Saidan said,

In environmental economics, the difference falls into a undefined area.

As said physical is what you can touch,manipulate and, the kind of manipulation made defines the quality of the environment.

However, in economics, there's a trick situation here, because you can have a physical attribute, which you can change, thus changing it's quality, but but is not, in environmental economics, tangible. The best example is the landscape. The landscape have intangible qualities (such as visual appealing) that have a tangible effect into us, but can not be measured by any means, so, it's intangible.

That is a very good question, but as you can see, depending on the field of research it can have different, even controversial, definitions.