The Pearl River Delta is one of the biggest electronics manufacturing regions in the world. Due to the presence of abandoned industrial sites and the proliferation of large-scale electronics companies in the past four decades, it is therefore imperative to investigate the extent of heavy metals and polychlorinated biphenyls (PCBs) contamination in the region. Spatial and temporal distribution of heavy metals (Cr, Cu, Ni, Pb, and Zn) and PCBs (PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, and PCB180) in the Lianhua Mountain reservoir in the Pearl River Delta, Dongguan City, China were examined based on a sedimentary profile analysis. Higher concentrations of the heavy metals detected were recorded in bottom sediments whereas 70% of the detected PCBs recorded maximum concentrations in top sediments. The geo-accumulation indices (Igeo) indicate that the study area is uncontaminated to moderately contaminated. Also, the integrated pollution indices (IPI) were above 1, except Pb, which shows that the study area is contaminated with heavy metals from anthropogenic sources. The concentrations of individual heavy metals and PCBs over a period of 60 years were also analyzed in order to establish a historical trend of pollution in the study area. This study provides baseline information on the level and historical trend of heavy metals and PCBs pollution in the study area.
Supercritical water gasification (SCWG) of food waste was carried out with nickel and alkali catalysts (NaOH, KOH, Ca(OH) 2 , Na 2 CO 3 , NaHCO 3 and K 2 CO 3 ). The food waste was comprised of a variety of food items. The experiment was performed in a batch reactor at supercritical water (SCW) conditions of 400°C and 22.1MPa for 10mins. Hydrogen (H 2 ) gas yield regarding the use of the catalysts was in the sequence; Ni-K 2 CO 3 > Ni-NaOH > Ni-KOH > Ni-NaHCO 3 > Ni > Ca(OH) 2 > Ni-Na 2 CO 3 > No catalyst. The results of this study indicate that using Ni was effective to support the steam reforming reaction. However its effects on the water gas shift reaction (WGSR) was little. Also carbon dioxide (CO 2 ) was the predominant gas product in the presence of metal carbonates and bicarbonate. As a result, H 2 selectivity was in the sequence, Ni-NaOH > Ni-KOH > Ni-K 2 CO 3 > Ni-Ca(OH) 2 > Ni > Ni-Na 2 CO 3 > NiNaHCO 3 > No catalyst. Furthermore, using 4g of NaOH was effective to shift the WGSR forward to produce a higher H 2 yield and selectivity than when 4g of Ni was used. However, when equal amounts of Ni and NaOH were used, the conversion of food waste into gaseous products was necessary to produce more H 2 during the WGSR.
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