Study On Environmental Distribution And Health Risk Assessment Of PCDD/F Emissions From Hazardous Waste Incineration

Due to the advantages of high-temperature detoxification, significant volume and mass reduction of hazardous waste, the incineration technology has been booming and applied in China. However, the construction and operation of hazardous waste incinerator (HWI) has stirred public concerns due to the secondary pollution from the facility, especially the environmental toxics and associated adverse health effects of the emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). In order to establish effective countermeasures to control the emissions of PCDD/Fs, it is urgent to understand the contamination status of PCDD/Fs around the HWI and its health risk to ambient people. In this study, by combination of the modeling program AMS/EPA Regulatory Model (AERMOD), environmental monitoring and statistical analysis (Factor Analysis), we firstly investigated the dioxin emission levels of HWIs and estimate their emission factors to the atmosphere, and study the emissions of PCDD/Fs of a typical HWI in China, meanwhile, levels and profiles of PCDD/Fs in soil, air, sediments, water and tree bark around this HWI, the transportation of PCDD/Fs in ambient air and the environmental exposure risk of PCDD/Fs for residents living around the facility were all investigated.The average emission levels of PCDD/Fs from12investigated HWIs was0.33ng I-TEQ/Nm3, only two incinerators showed emission levels above current PCDD/Fs emission standard for HWIs in China (0.5ng TEQ/Nm3). It was estimated that5.0g I-TEQ of PCDD/Fs was annually released from HWIs to the atmosphere in China in2010, which was less than that from HWIs reported in2007. OCDD,2,3,4,7,8-PeCDF,1,2,3,4,7,8-HpCDF and OCDF are main congeners in these three groups, and the congeners fraction of flue gas samples in our study were typical HWI gas profile with a dominant homologue of PCDFs and relatively low PCDDs.The concentrations of the PCDD/Fs emissions during start-up and shut-down exceeded the emission limit (0.5ng I-TEQ/Nm3) for HWIs in China, reach to1.1-10 and2-6times of this limit, separately. The total PCDD/Fs emission during the start-up and shut-down procedure was1.37mg I-TEQ. It is assumed that the start-up and shut-down for one time of HWI accounted for30%of the whole yaer’s normal operations (0.03ng I-TEQ/Nm3) in this study.The mean and median baseline concentration and I-TEQ value of soils were2500.33pg/g (5.61ng I-TEQ/kg),3876.67pg/g (7.35ng I-TEQ/kg), respectively. The PCDD/Fs concentration in soil was at a high level as baseline data. On the other hand, the temporal variations (2009-2013) of the average I-TEQ value in soils increased by23%, which revealed the soil was contaminated by HWI. Four sediments samples data showed that all PCDD/Fs concentration were higher than0.85ng I-TEQ/kg, there were two samples lower than2.5ng I-TEQ/kg, Lake1had the highest concentration. Similar congener I-TEQ profiles were found among the sediment in Lake1and soils, which indicated this sediment was contaminated by soil.The PCDD/Fs concentration of tree bark were not very high, fingerprint analysis showed that the HWI emssion had some influence on the tree bark at downwind direction. The fraction of particle-bound PCDD/Fs are much higher than gas-phase PCDD/Fs were found both in the air samples celected inside the incineration plant and outside, and P5CDF was the dominant congener. Atmospheric concentrations of PCDD/Fs inside the incineration plant were higher than Japanese Air Quality Standard (0.6pg I-TEQ/m3).The PCDD/F emissions of HWI had limited impact on the surrounding atmosphere on normal conditions, its incremental contribution to atmospheric concentration below the Japanese Air Quality Standard (0.6pg I-TEQ/m3). The highest risk area of PCDD/Fs exposure was under the downwind direction within the range of700-1000m, the maximum ground concentration and deposition of PCDD/Fs are within this range. Although PCDD/F emissions of HWI during start-up and shut-down procedure lead to increasing of atmospheric levels, unfavorable weather conditions and high emissions of PCDD/Fs cause atmospheric concentrations of PCDD/Fs higher than Japanese Air Quality Standard (0.6pg I-TEQ/m3). The soil samples in the distance between incinerator less than1km had larger PCDD/Fs increase after a year normal operation of the HWI, the maximum increments concentration in soil is8.5×10-7pg-TEQ/g. The results showed that if the incinerator emissions satisfied standard (0.5ng I-TEQ/Nm3) at normal operating conditions, ambient soil and atmospheric PCDD/Fs concentration increasing amount caused by flue gas is limited, almost negligible.The health risk of urban resident and rural resident living in the vicinity of the HWI showed, hazard index was much lower than all existing standards, and the cancer risk is only slightly higher than the current California standard. The hazard Index ranged from0.12×10-6to11.16×10-6and0.06×10-6to6.73×10-6, for urban resident and rural resident living in the vicinity of the HW incineration plant. The study showed that the potential health risk of residents in this region was in a safe range, but the urban residents had higher health risk. According to the cancer risk threshold we redefined, the scope of urban residents exceeded the cancer risk threshold is bigger than rural residents.