Reduction, Scientific Levels, and Physicalism

The explication of reduction proposed above sheds light onto the notion of a scientific level in a reductive hierarchy. Levels turn out to be concepmal levels, or levels of kinds of property structures. The physical level is distinct from the mental level in a reductive hierarchy because the former employs physical property structures, i.e. structures that present us with an object as physical, whereas the latter employs mental property structures that present us with an object as mental. This is 

van Riel, The Concept of Reduction, Philosophical Studies Series 121, 203 

There is a possible reductive hierarchy in a physicalist world which is such that for some x, x belongs to the, say, biological level of that hierarchy and, thus, not to the physical level of that hierarchy and is, thus, biological and not physical (since in a reductive hierarchy, it cannot be both at the same time). At the same time, since physicalism is true, x is physical. So, doesn t it belong to the physical level This pretty much looks like a contradiction. 

---