Heavy metal speciation in landfill leachate and its association with organic matter

Abstract: This study investigated the speciation of heavy metals in the landfill leachate, which was collected from Nam Son sanitary landfill site in Hanoi, Vietnam. Physical fractionation was implemented using 1 μm glass fiber to separate the particulate fraction of heavy metals from the dissolved one. Then, supelite™ DAX-8 resin was employed to separate humic substances as the dissolved organic fraction and the dissolved inorganic fraction. Excitation-Emission Matrices (EEMs) fluorescence spectroscopy was applied to estimate the footprint of organic matter’s components. The results suggested that heavy metals in Nam Son landfill leachate were mainly present in the dissolved inorganic fraction, followed by complexes with humic substances, including humic and fulvic acids. A majority of Fe, Cu, Ni, and As formed chelates with humic substances while around 62% of Al existed in the particulate fraction. The existence in the particulate, dissolved organic and dissolved inorganic fractions varied significantly among investigated heavy metals. From heavy metal and organic matter binding, it was discovered that the dissolved organic matter (DOM) played a crucial role in heavy metal speciation in landfill leachate. This finding may be useful for predicting the mobility of heavy metals in the environment as well as the effects of humic substances on the coagulation process used in the landfill leachate treatment.