I am finding this challenge somewhat broad. It seems like you can go in any direction with. When something is pure it means that it has not been contaminated or adulterated by some external factor. The contaminating or adulterating factor can also be completely vague, and can change within the context in which the term is being applied. Pureness can be defined in the human context in many ways, and it can also be defined in the experiential context in many other ways. Many examples can be found here.
Pureness can sometimes be seen in opposition to complexity, with an absence of factors that complicate your visualization of the subject. It is sometimes associated with a certain simplicity of the subject matter. With that in mind, here are some pictures with my interpretation of the theme.
I am not sure if I have interpreted the theme of the challenge in a proper manner, and if so, if the context in which the adjective “pure” is being used can be clearly expressed in words. But that is all I have…
FYI, the first picture was taken at White Sands National Monument. The rest of the pictures are generic.