What are the differences in chemical leaching between PVC and polypropylene in landfills?

In landfill environments, PVC (polyvinyl chloride) and polypropylene exhibit significantly different chemical leaching behaviors due to their distinct molecular structures and additive compositions. PVC contains chlorine atoms in its polymer backbone and requires plasticizers like phthalates for flexibility, making it prone to leaching these additives along with heavy metal stabilizers and chlorine compounds. The decomposition process releases hydrochloric acid and potentially forms dioxins under certain conditions. Conversely, polypropylene's hydrocarbon-only structure without chlorine makes it more chemically stable. While both plastics can leach additives, PVC demonstrates substantially higher leaching potential for toxic substances including phthalates, lead, cadmium, and organotin compounds. Polypropylene primarily leaches antioxidant and UV stabilizer additives, generally considered less hazardous. Environmental factors like pH, temperature, and microbial activity affect both plastics, but PVC's leaching persists longer and involves more concerning chemicals that can impact groundwater quality and ecosystem health. The longer-term environmental persistence of both materials means leaching continues for decades, though PVC presents greater concerns due to both its additive package and chlorine content that can form acidic degradation products.