Estimating health damage cost from secondary sulfate particles—a case study of Hunan Province,China

China's coal dominated energy pattern has resulted in large amount of SO 2 emissions. Estimate of the sulfur related health damage cost is necessary to help perform systematic cost benefit analysis and set national energy and emissions control priorities. Current researches were confined to gaseous SO 2 in urban areas; however, secondary sulfate (SO 2- 4) particles can exert serious impact in a wider region. Based on the concept of “intake fraction', CALPUFF long range dispersion model and 180 sample emission sources, multiple regression equation was obtained with good correlation( r =0 85), which illustrates that populations were key parameters to determine intake fraction but source characteristics were insignificant. Based on the formula and the population distribution data, county level intake fractions were mapped for Hunan Province(range: 1 1×10 -6 -3 2×10 -6 ) of China. A combination of county level SO 2 emissions with the intake fractions yields a total 1 98 tons of sulfate(SO 2- 4) inhalation, and resulting total health damage cost to be 0 76(willingness to pay approach, WTP) or 0 16(human capital approach, HC) billion USD in 1997, about 2.1% or 0 45% of GDP in Hunan in 1997. Average health damage cost per ton of SO 2 emission is 930(WTP) or 200 USD(HC). The results demonstrated that more stringent regulation should be forced.

Performance of personalized ventilation in mitigating short-range airborne transmission under the influence of multiple factors

The effectiveness of using personalized ventilation(PV)in mitigating airborne transmission risk was found to be easily affected by multiple factors.The aim of this study was hereby to evaluate the impacts of several important factors on the performance of PV in airborne disease control for closely ranged occupants.Orthogonal experiments were designed for CFD simulations under different levels of four selected factors.Results indicated that the order of significance of these four factors affecting the intake fraction(IF)of the exposed occupant was as follows:mode of PV use>relative distance between occupants>PV airflow volume>background ventilation.The best combination of the four tested factors was PV of 15 L/s for both the infected source and the exposed occupant,with a relative distance of 2 m between them and mixing ventilation,which would yield an IF of merely 0.0246%.The worst combination was PV of 6 L/s for the exposed occupant only,with a relative distance of 0.86 m under displacement ventilation,indicating an elevated IF of 0.2919%.The increase of PV air volume and relative separation distance both contributed to lower exposure risk,but they were not as influential as the mode of PV use.PV integrated with mixing ventilation and utilized for both infected and susceptible occupants were recommended.The findings in this study will be helpful to provide guidance for the implementation of PV in indoor environment for airborne infection control.

Effect of traffic tidal flow on pollutant dispersion in various street canyons and corresponding mitigation strategies

Increasing traffic emission presents a high risk of exposure to residents in near-road buildings.Traffic tidal flow(TTF)has gradually become one of the most important components of urban traffic congestion.By computational fluid dynamics simulation,the present study examines the airflow,spatial distribution of pollutant concentration,and personal intake fraction(IF_p)of CO in five street canyon structures(shallow,regular,deep,step-up,and step-down street canyons),with non-uniform TTF-induced traffic emission considered.Optimal urban design devices(wind catchers)are subsequently introduced to reduce IF_p.The results suggest that leeward IF_p is far higher in concentration than the windward wall in the shallow,regular,step-up,and step-down street canyons but lower than the windward side in the deep street canyon under different TTF conditions.Moreover,the TTF condition S L(leeward source)/S W(windward source)=3/1 leads to a higher leeward IF_p in the shallow,regular,deep,and step-up street canyons,compared with S L/S W=1/3;however,no significant difference in windward IF_p is found under the different TTF conditions.The highest IF_p and lowest IF_p for both TTF configurations occur in the step-down and shallow street canyons,respectively.Finally,the effect of wind catchers(WCs)varies between the street canyon structures under different TTF conditions.WCs can lead to at least 30.6%reduction in leeward overall average IF_p(<IF_p>)in the shallow,regular,step-up,and step-down street canyons,as well as 12.8%-78.4%decrease in windward<IF_p>owing to the WCs in the regular,deep,step-up,and step-down street canyons.