Risk Control Values and Remediation Goals for Benzo[a]pyrene in Contaminated Sites: Sectoral Characteristics, Temporal Trends, and Empirical Implications.

Benzo[a]pyrene (BaP) is a highly carcinogenic pollutant of global concern. There is a need for a comprehensive assessment of regulation decisions for BaP-contaminated site management. Herein, we present a quantitative evaluation of remediation decisions from 206 contaminated sites throughout China between 2011 and 2021 using the cumulative distribution function (CDF) and related statistical methodologies. Generally, remediation decisions seek to establish remediation goals (RGs) based on the risk control values (RCVs). Cumulative frequency distributions, followed non-normal S-curve, emerged multiple nonrandom clusters. These clusters are consistent with regulatory guidance values (RGVs), of national and local soil levels in China. Additionally, priority interventions for contaminated sites were determined by prioritizing RCVs and identifying differences across industrial sectors. Notably, we found that RCVs and RGs became more relaxed over time, effectively reducing conservation and unsustainable social and economic impacts. The joint probability curve was applied to model decision values, which afforded a generic empirically important RG of 0.57 mg/kg. Overall, these findings will help decision-makers and governments develop appropriate remediation strategies for BaP as a ubiquitous priority pollutant.

Improved estimation of rural residential coal emissions considering coal-stove combinations and combustion modes.

Rural residential coal combustion (RRCC) has detrimental effects on air quality, climate, and human health. There are large uncertainties regarding emissions from RRCC owing to the lack of consideration of several key factors (e.g. combination modes of coal and stoves, combustion modes, and high temporal resolution). In this study, we provided a new estimation framework for RRCC emissions through a case study in the Beijing-Tianjin-Hebei (BTH) region, China. The emission estimations were improved according to four aspects, namely (1) coal-specific and stove-specific coal consumption was calculated based on face-to-face field interviews of 6700 valid volunteers/households covering 288 villages in 50 counties; (2) the influences of combustion modes (flaming and smoldering modes) on emissions were considered; (3) emissions of different fuel-stove combinations were estimated based on coal, stove, and combustion mode-specific RRCC consumption and localised emission factors; and (4) a method for emission estimation with high temporal resolution (1 h) was developed. The results indicated that RRCC emitted 413.6 kt SO2, 55.7 kt NOx, 5717.3 kt CO, 149.4 kt VOCs, 167.1 kt PM2.5, 18.2 kt EC, 32.5 kt OC, and 8.2 kt NH3 in 2016. The combination of bituminous coal and an advanced coal stove was the most significant contributor (20.7-71.8%) to various pollutant emissions. Coal combusted under the flaming mode contributed to most (81.9%) of the total coal consumption, and thus emitted the majority (50.8-99.8%) of pollutants, except for VOCs. Meanwhile, that under the smoldering mode only accounted for 18.1% of the total consumption, but contributed 49.2% and 74.7% of the CO and VOCs emissions, respectively. Two clear emission peaks occurred at approximately 7:00-9:00 and 18:00-20:00. The detailed coal consumption and emissions with high temporal and spatial resolution can provide sound data for further research on rural environmental issues and scientific support to pollution control strategies.

Improved estimation of air pollutant emissions from landing and takeoff cycles of civil aircraft in China.

Civil aircraft emissions during landing and takeoff (LTO) are important air pollutant sources, but have been given insufficient attention in China. Accurate estimation of these emissions is limited by a lack of important parameters, such as detailed flight information and the dynamic time in climb and approach modes during LTO that are dependent on mixing layer height (MLH). We developed a flight-time/flight-height relationship using real-time height information in Aircraft Meteorological Data Relay data, and then calculated the actual time for each flight in those two modes based on the actual MLH from meteorological observation. Hourly emissions of civil aircraft were then estimated based on the database of each flight. Total emissions of NOx, CO, SO2, HC and PM from LTO cycles of domestic flights in China during 2015 were 37.78 Gg, 30.25 Gg, 12.00 Gg, 2.38 Gg and 0.75 Gg, respectively. Substantial monthly, daily and hourly variations of emissions due to the flight schedule as well as MLH were calculated. Large differences were found between the new estimation and emissions calculated based on traditional method. Compared with the emissions estimated based on default parameter obtained from International Civil Aviation Organization, the average difference of annual emission among airports with new estimation for various pollutants was approximately 30.3% in climb mode and 81.4% in approach mode; compared with the emissions estimated based on the method proposed by China National Guide, the average difference of annual emission among airports were 37.4% (NOx), 8.4% (CO), 73.1% (HC) and 58.1% (PM) during LTO process. The monthly airport-specific emissions per LTO were also proposed. These can provide necessary and meaningful support for the revision of the values in National Guide.