Synchrotron radiation-induced micro-X-ray fluorescence (SR-mu XRF) was employed to elucidate the elemental characteristics of contaminated biodegradable fraction of municipal solid waste (BFMSW). Six sectioned BFMSW samples were selected for SR-mu XRF mapping and 50 individual fine particles sorbed onto BFMSW were analyzed using SR-mu XRF point scanning. The results showed that heavy metals tended to be concentrated on the surface of BFMSW and highly localized to some "hot-spots". Marked differences in heavy metal sequestering potentials among various kinds of BFMSW, and the significant role of heavy metal "hot-spots" in BFMSW contamination were identified. The lower heavy metal levels in the simulated samples compared to field samples (with longer and more intense mixing) indicated that inter-contamination during waste handling contributed significantly to heavy metal accumulation in BFMSW. Furthermore, additional information regarding elemental characteristics of individual particles could be acquired using SR-mu XRF. (C) 2013 Elsevier Ltd. All rights reserved.