Solar radiation triggers atmospheric nitrous acid (HONO) photolysis, producing OH radicals, thereby accelerating photochemical reactions, leading to severe secondary pollution formation. Missing ...daytime sources were detected in the extensive HONO budget studies carried out in the past. In the rural North China Plain, some studies attributed those to soil emissions and more recent studies to dew evaporation. To investigate the contributions of these two processes to HONO temporal variations and unknown production rates in rural areas, HONO and related field observations obtained at the Gucheng Agricultural and Ecological Meteorological Station during spring and autumn were thoroughly analyzed. Morning peaks in HONO frequently occurred simultaneously with those of ammonia (NH
) and water vapor both during spring and autumn, which were mostly caused by dew and guttation water evaporation. In spring, the unknown HONO production rate revealed pronounced afternoon peaks exceeding those in the morning. In autumn, however, the afternoon peak was barely detectable compared to the morning peak. The unknown afternoon HONO production rates were attributed to soil emissions due to their good relationship to soil temperatures, while NH
soil emissions were not as distinctive as dew emissions. Overall, the relative daytime contribution of dew emissions was higher during autumn, while soil emissions dominated during spring. Nevertheless, dew emission remained the most dominant contributor to morning time HONO emissions in both seasons, thus being responsible for the initiation of daytime OH radical formation and activation of photochemical reactions, while soil emissions further maintained HONO and associated OH radial formation rates at a high level, especially during spring. Future studies need to thoroughly investigate the influencing factors of dew and soil emissions and establish their relationship to HONO emission rates, form reasonable parameterizations for regional and global models, and improve current underestimations in modeled atmospheric oxidation capacity.
Haze and fog are both low visibility events, but with different physical properties. Haze is caused by the increase of aerosol loading or the hygroscopic growth of aerosol at high relative humidity, ...whereas visibility degradation in fog is due to the light scattering of fog droplets, which are transited from aerosols via activation. Based on the difference of physical properties be- tween haze and fog, this study presents a novel method to distinguish haze and fog using real time measurements of PM2.5, visibility, and relative humidity. In this method, a criterion can be developed based on the local historical data of particle number size distributions and aerosol hygroscopicity. Low visibility events can be classified into haze and fog according to this criterion.
We established an evaluation framework for sustainable forest management (SFM) development based on locals’ perspectives using the importance-performance analysis (IPA) method in a rural area of ...Taiwan. It identified the factors that affected local people’s participation in and awareness of SFM based on local demographics, development factors of SFM, and perceptions of SFM, through the logistic regression method (LRM). Both the levels of importance and performance (I-P) of the SFM indicators were rated by the local residents and the differences between importance–performance among indigenous and non-indigenous people were examined. The factors that affected differentiation of local people’s participation in the SFM program were: (1) forestry workers, (2) indigenous people, and (3) SFM development factors. The findings provide both theoretical constructs and policy implications for SFM mechanisms for the forest stewardship council (FSC) and sustainable development goals (SDGs) in a sustainable rural development.
Public perception of endangered species is crucial for successful management of community-based conservation and sustainability of national parks. By the method of choice experiment, our study ...evaluated conservation preferences and willingness to donate money for flagship and non-flagship species using a choice experiment with 409 residents living near the Lanstang river source of Sanjiangyuan National Park, China. We found that flagship species such as the Snow leopard ( Pristine plateau ) and White-lipped deer ( Przewalskium albirostris ) generated more conservation funds than non-flagship species. However, not all flagship species were accepted. Respondents disliked Tibetan brown bears ( Ursus arctos pruinosus ) due to direct human-wildlife conflicts such as bodily injury and property damage. Heterogeneity of preference was influenced by household income, religious beliefs, ethnicity, culture, and conservation awareness. Results can be used to establish a local community-participative framework by combining conservation motivations that alleviate human-wildlife conflict.
Southeast Tibet is significant in maintaining key ecological functions and providing irreplaceable ecosystem services but is also extremely vulnerable and susceptible to the impacts of human ...activities. Understanding the attitudes of local residents toward ecosystem conservation is considered essential for nature resource management. We therefore aimed to conduct an evaluation framework under hypothetical scenarios to measure communities’ willingness to participate in ecosystem conservation using the contingent valuation method (CVM). Second, this study determined the underlying factors that might affect local’s willingness to participate and then compared the willingness to pay (WTP) and willingness to work (WTW) for different types of nature reserves. We found that income, education, community attachment, and acceptance of a payment scheme are significant factors determining the average amount that residents are willing to pay for ecosystem conservation, while their income, acceptance of a work scheme, and education are significant factors influencing the average service time that residents are willing to devote to work. Our results revealed that community residents have considerable willingness to participate in ecosystem conservation, which points not only to the great value attached to the ecosystem service function of Southeast Tibet nature but also suggests that people’s willingness to participate is influenced by a conglomeration of socio-economic characteristics and their previous experience. The information herein can be used to implement conservation planning that involves community co-management and policymaking for sustainable development and will be beneficial to the dynamic conservation and adaptive management of Tibetan nature reserves.
To investigate the impacts of relative humidity (RH) on secondary organic aerosol (SOA) concentrations and chemical reactions, the carbonaceous aerosol components i.e., organic carbon (OC) and ...element carbon (EC) were quantified in daily PM
2.5
samples collected at a background site in East China during summer 2015. Based on the method of EC-tracer, the concentration of secondary organic carbon (SOC) demonstrated an obvious negative relationship with RH higher than 60%. Moreover, the ratio of SOC/EC also exhibited obvious decreasing trends with increasing RH, indicating negative effects for chemical production of SOA under high RH conditions. Due to high RH, photochemistry was weakened, gaseous oxidant concentrations was lowered (e.g., significantly decreased O
3
levels), and the production rates of SOA were relatively low. On the other hand, because of more water uptake under higher RH conditions, the aerosol droplet acidity was reduced and enhancement of SOA formation by acidity was accordingly absent. In addition, high RH also plays an important role in changing viscosity of pre-existing aerosol coatings, which can affect reactive uptake yield of SOA. Overall, the results from this study imply that SOA production may be more associated with photochemical processes, while aqueous-phase chemistry is not very important for some SOA formation in a moist ambient environment. In the ambient atmosphere, oxidant concentrations, reaction rates, airborne species, etc., are highly variable. How do these factors affect SOA yields under given ambient environment warrants further detailed investigations.
Atmospheric nitrogen deposition is of great concern to both air quality and the ecosystem, particularly in northern China, which covers one-quarter of China’s cultivated land and has many heavily air ...polluted cities. To understand the characteristics of wet N deposition at rural sites in northern China, one-year wet deposition samples were collected in the Daheitin reservoir region. Due to the intense emissions of gaseous nitrogen compounds from heating activities during cold seasons and distinct dilution effects under different rainfall intensities and frequencies, the volume weighted mean concentrations of wet N deposition showed higher levels in dry seasons but lower levels in wet seasons. In contrast, the wet N deposition rates varied consistently with precipitation, i.e., high during the wet season and lower during the dry season. The annual wet deposition rate of total inorganic ions (the sum of NO3−–N and NH4+–N) at the rural site in North China from July 2019 to June 2020 was observed at 18.9 kg N ha−1 yr−1, still remained at a relatively high level. In addition, biomass burning activities are ubiquitous in China, especially in northern China; however, studies on its impact on wet N deposition are limited. Non-sea salt potassium ion (nss-K+) was employed as a molecular tracer to investigate the characteristics of biomass burning activities as well as their impact on the chemical properties of wet N deposition. Three precipitation events with high nss-K+ levels were captured during the harvest season (June to July). The variations in the patterns of nss-K+, deposited N species, and ratios of nss-K+ to nitrogen species as well as their relationships all indicated that biomass burning emissions contributed remarkably to NO3−–N but had a minor influence on NH4+–N.
From July 2009–April 2011, 304 whole-air samples were collected at urban and suburban sites in four Chinese cities. The results indicated that recent chlorofluorocarbon (CFC) concentrations in all ...four cities are approaching Northern Hemispheric (NH) background levels, suggesting that the phase-out of CFCs in China is underway. However, hydrochlorofluorocarbon (HCFC) and 1,1,1,2-tetrafluoroethane (HFC-134a, CH2FCF3) concentrations have risen far above the NH background levels. Their concentration variability is evident, suggesting significant regional emissions. One-way analysis of variance (ANOVA) and independent-sample t-tests were applied to analyze the spatial distributions and emissions. Monochlorodifluoromethane (HCFC-22, CHClF2) levels at the urban sites were 30% higher than those observed at the suburban sites (P < 0.05), likely owing to larger population density in the urban areas. The largest 1-dichloro-1,1-fluoroethane (HCFC-142b, CH3CClF2) mean concentrations were detected in Beijing (131 and 52 pptv for urban and suburban sites, respectively), likely because of more widespread use of extruded polystyrene board. The variation in HFC-134a concentration levels in different cities was mainly related to the vehicle population. In addition, the different HCFC species exhibited significant positive correlations amongst themselves for each city (P < 0.05), suggesting that either they were emitted from similar or co-located sources or they shared similar emission patterns. These results are helpful to confirm the phase-out of ozone-depleting substances (ODSs) and to provide guidance for implementing effective phase-out strategies for ODSs and greenhouse gases.
•304 air samples were collected at urban and suburban sites in four Chinese cities.•CFC levels are approaching NH background levels, suggesting the underway phase-out.•HCFC and HFC levels far exceed the NH background levels, indicating wide emission.•Their yearly trends and seasonal variations were analyzed.•By using statistical method, spatial variations and emission were also analyzed.
A field experiment was conducted in an intensive fog event between November 5 and November 8, 2009, in a heavily SO2-polluted area in North China Plain （NCP）, to measure SO2 and other air pollutants, ...liquid water content （LWC） of fog droplets, and other basic meteorological parameters. During the fog period, the concentrations of SO2 showed large variability, which was closely related to the LWC in the fog droplets. The averaged concentration of SO2 during non-fog periods was about 25 ppbv, while during the fog period, it rapidly reduced to about 4-7 ppbv. Such large reduction of SO2 suggested that a majority of SO2 （about 70%-80%） had reverted from gas to aqueous phase on account of the high solubility of SO2 in water in the fog droplets. However, the calculated gas to aqueous phase conversion was largely underestimated by merely using the Henry＇s Law constant of SO2, thus suggesting that aqueous reaction of SO2 in fog droplets might play some important role in enhancing the solubility of SO2. To simplify the phenomenon, an ＂effective solubility coefficient＂ is proposed in this study. This variability of SO2 measurement during the extensive fog event provides direct evidence of oxidation of SO2 in fog droplets, thus providing important implications for better understanding of the acidity in clouds, precipitation, and fogs in NCP, now a central environmental focus in China due to its rapid economic development.
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