دانلود رایگان مقاله خصوصیات شیمیایی و سمی انتشار ذرات معلق از احتراق زباله کنار جاده

Abstract

Roadside trash burning is largely unexamined as a factor that influences air quality, radiative forcing, and human health even though it is ubiquitously practiced across many global regions, including throughout India. The objective of this research is to examine characteristics and redox activity of fine particulate matter (PM2.5) associated with roadside trash burning in Bangalore, India. Emissions from smoldering and flaming roadside trash piles (n = 24) were analyzed for organic and elemental carbon (OC/EC), brown carbon (BrC), and toxicity (i.e. redox activity, measured via the dithiothreitol “DTT” assay). A subset of samples (n = 8) were further assessed for toxicity by a cellular assay (macrophage assay) and also analyzed for trace organic compounds. Results show high variability of chemical composition and toxicity between trash-burning emissions, and characteristic differences from ambient samples. OC/EC ratios for trash-burning emissions range from 0.8 to 1500, while ambient OC/EC ratios were observed at 5.4 ± 1.8. Trace organic compound analyses indicate that emissions from trash-burning piles were frequently composed of aromatic di-acids (likely from burning plastics) and levoglucosan (an indicator of biomass burning), while the ambient sample showed high response from alkanes indicating notable representation from vehicular exhaust. Volume-normalized DTT results (i.e., redox activity normalized by the volume of air pulled through the filter during sampling) were, unsurprisingly, extremely elevated in all trash-burning samples. Interestingly, DTT results suggest that on a per-mass basis, fresh trash-burning emissions are an order of magnitude less redox-active than ambient air (13.4 ± 14.8 pmol/min/μgOC for trash burning; 107 ± 25 pmol/min/μgOC for ambient). However, overall results indicate that near trash-burning sources, exposure to redox-active PM can be extremely high.

3.4. Conclusions

In summary, ROS results measured using both the DTT and macrophage assays find that on a per-mass basis, fresh trashburning emissions appear to be less redox active than the PM2.5 in ambient air. Our analyses also find that volume-normalized trash-burning emissions, unsurprisingly, generate considerably higher redox activity than ambient air. On this per-volume basis, the ambient background average (0.79 ± 0.13 nmol/min/m3 ) is significantly lower than trash-burning DTTV consumption rates, taken from in-plume measurements, which range from ~100 to 3500 nmol/min/m3 . In fact, results suggest that ~1 min of direct exposure to trash-burning emissions (i.e., if a person were directly breathing from within the plume, only 0.5 m from the combustion itselfdthis is unrealistic but a useful thought experiment) is equivalent (in DTTV activity) to an entire day of breathing in ambient air. Compositional analyses of trash-burning filters highlight a broad distribution of OC/EC ratios and vastly different fingerprints of organics, including plastic burning signatures. The prevalence of trash burning in India and elsewhere, along with these results on the composition and oxidative activity of actual, in situ, trash-burning emissions provide additional evidence that trash burning represents a significant public health hazard. Further, recent findings on the soiling of the Taj Mahal give added impetus to identifying potential controls (Bergin et al., 2015).