Complex sentence: These xenobiotic compounds tend to form partially insoluble layers called dense non-aqueous phase liquids (DNAPLs) at the bottom of ground-water aquifers, which solubilize in a slow, reservoir-like manner, making TCE and PCE among the most common groundwater pollutants.
Split into simpler sentences: These xenobiotic compounds tend to form partially insoluble layers called dense non-aqueous phase liquids (DNAPLs) at the bottom of ground-water aquifers. These accumulations solubilize in a slow, reservoir-like manner, making TCE and PCE among the most common groundwater pollutants.