Evaluating the impact of odors from the 1,955 landfills in China using a bottom-up approach
Neighborhoods in the proximity of municipal solid waste landfills are often burdened with a series of adverse consequences of the practice of solid waste disposal. One of the major impacts is the unpleasant odors generated from wastes decomposition. According to the “12369” environmental complaints hotline by the Ministry of Environmental Protection in China, there were 25 cases complaining about landfill odors, accounting for 1.5 percent of the total cases. [lxj1] Landfill odors problems have become the major reason by residents to oppose the implement of landfills. The evaluation of population exposure to landfill odors, however, has been rarely thoroughly studied in China. Such research has been hindered by the lack of data and the limitation of computation capacity.
In this study, we proposed a methodology to estimate the odors impact on landfills’ surrounding residents using landfill information and population data. Our bottom-up method can ensure the accuracy of calculation as well as the full coverage of China. We collected and processed data from 1,955 landfills in China, including both sanitary landfill and open dump. Detailed information about each landfill contained the annual total amount of landfilled waste, waste composition, management level, and meteorological and hydrological features (Cai et al., 2014). The emissions of odors, represented by H2S, from each landfill were estimate using the FOD (First Order Decay) model. The odor impact range of each landfill was estimated using the GSGDM (Ground-Level Sources Gaussian Dispersion Model), as one of the most widely accepted models for landfill odor dispersion (Tagaris et al., 2012). The average impact distance was 796m, with predominant impact distances ranging from 400m to 1000m (46.85%) and very few (0.15%) that were larger than 10,000m.
Using LandScan 1km gridded population data and the odor impact ranges, we estimated the population exposure to the impact of landfill odors across China in 2012, as shown in Figure 1. The total impacted population has reached to 12.28 million, accounting for 0.90% of total population in China. The affected population was largely concentrated in the east of China. Guangdong and Hunan provinces have the largest impacted population with over 1 million, respectively. Individual landfill with largest impacted residents (900,699 persons) was also located in Guangdong province. In total, there were 150 landfills that were associated with over 100,000 impacted residents, and only 65 landfills had zero odor impacts on surrounding population.
We also applied high resolution images to visualize the odor impact pattern of 4 typical landfills. As shown in Figure 2, Beijing Gaoantun landfill and Nanjing Tianjingwa landfill are located very close to the residences, with a few hospitals and schools falling inside the affected areas. Based on Weibo data (China’s version Tweeter), we could identify the human activity intensity around landfills. The more weibos, the higher the activity intensity. For example, we found that a large amount of weibos were posted around the airport on the east of Mianyang landfill and in villages on the southwest of Xi’an Jiangcungou landfill. This information further helps us identify the key areas with high frequencies of people appearance among the general affected areas.
Further improvements could be made to understand the detailed characteristics of odors and dispersion patterns, and to propose mitigation technical measurements and policy recommendations.
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