Characterization of odorous gases at landfill site and in surrounding areas.

Concentration levels and seasonal variation of odorous gases at landfill site and in surrounding areas within the city of Incheon, South Korea were investigated. Sampling was conducted at 11 points (5 at landfill site and 6 in surrounding areas). The highest concentrations of odorous gases (complex odor, ammonia, acetaldehyde, and VOCs) at landfill site were found in summer, probably due to fast decomposition of waste in high temperature related with more release of ammonia. In addition, specific weather condition of dominant wind direction, humidity and higher atmospheric pressure with no or lower wind speed caused positive effect of higher aldehyde compounds and VOCs concentration. Similar to other studies, sludge-related sampling site S-2, where a couple of odor generating facilities including sludge mixing and drying treatment process are located, showed the highest concentration levels of odorous gases compared to other sites. Odor generation frequency was in the order of acetaldehyde (68.8%) > ammonia (39.4%) > propionaldehyde (21.9%), which means the main substances generating the unpleasant odor at landfill site was recognized as aldehydes and ammonia due to combined effect of sludge-related facilities and meteorological conditions. Offensive odor was not a big pollution issue in most surrounding areas which are located within a circle of 5 km radius of the landfill except high odor generation frequency of acetaldehyde and propionaldehyde. Relative percentage differences (RPD) of odorous gases between day and night times at landfill site were below 10%, which indicates that the concentration differences in day and night were not severe. The relationship between concentrations of complex odor and designated offensive odor substances was analyzed statistically. At landfill site, the analysis shows that the correlation coefficient between the concentration of complex odor and ammonia was quite high (0.833), but it was much lower (0.129) in the surrounding areas due to considerably lower concentrations of these substances.