An improved method and apparatus for simultaneously monitoring the fluid flux and the target chemical mass fluxes in fluid flow systems is provided comprising the use of a body or shell that is inserted into the flow field. Inside or outside this body is a bundle of one or more permeable sorptive columns. The extremes of each column are hydraulically connected to the outside flow field around the body of the device through a pair of small openings in the body. The known non-uniform flow velocity distribution around the body of the invention causes a pressure difference between pairs of openings used to connect internal or external column units. A preferred shape of the body is a hydrofoil. Alternatively, instantaneous measurement of the fluid flux and contaminant composition is possible using pressure transducers and a chemical sensor. The method of monitoring comprises placing the invention in contact with the contaminated flow field, thereby allowing target chemicals in the in the fluid to be transported through internal column units and be sorbed on the insoluble sorbent matrix. The permeable sorptive column unit is then removed and the sorptive matrix is analyzed directly or visually (if visible tracers are used) to determine cumulative fluid fluxes and cumulative target chemical mass fluxes.