City In Southwest China Research Articles

Effects of short-term exposure to ambient airborne pollutants on COPD-related mortality among the elderly residents of Chengdu city in Southwest China

BackgroundChronic obstructive pulmonary disease (COPD) has become a severe global burden in terms of both health and the economy. Few studies, however, have thoroughly assessed the influence of air pollution on COPD-related mortality among elderly people in developing areas in the hinterland of southwestern China. This study is the first to examine the association between short-term exposure to ambient airborne pollutants and COPD-related mortality among elderly people in the central Sichuan Basin of southwestern China.MethodsData on COPD-related mortality among elderly people aged 60 and older were obtained from the Population Death Information Registration and Management System (PDIRMS). Data on airborne pollutants comprised of particulate matter < 2.5 μm in aerodynamic diameter (PM2.5), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3) were derived from 23 municipal environmental monitoring sites. Data on weather conditions, including daily mean temperature and relative humidity, were obtained from the Chengdu Meteorological Bureau. All data were collected from January 1, 2015, to December 31, 2018. A quasi-Poisson general additive model (GAM) was utilized to assess the effects of short-term exposure to airborne pollutants on COPD-related mortality among elderly people.ResultsA total of 61,058 COPD-related deaths of people aged 60 and older were obtained. Controlling the influences of daily temperature and relative humidity, interquartile range (IQR) concentration increases of PM2.5 (43 μg/m3), SO2 (8 μg/m3), NO2 (18 μg/m3), CO (0.4 mg/m3), and O3 (78 μg/m3) were associated with 2.7% (95% CI 1.0–4.4%), 4.3% (95% CI 2.1–6.4%), 3.6% (95% CI 1.7–5.6%), 2.7% (95% CI 0.6–4.8%), and 7.4% (95% CI 3.6–11.3%) increases in COPD-related mortality in people aged 60 and older, respectively. The exposure-response curves between each pollutant and the log-relative risk of COPD-related mortality exhibited linear relationships. Statistically significant differences in the associations between pollutants and COPD-related mortality were not observed among sociodemographic factors including age, gender, and marital status. The effects of O3 remained steady after adjusting for PM2.5, SO2, NO2, and CO each time in the two-pollutant models.ConclusionsIncreased concentrations of ambient airborne pollutants composed of PM2.5, SO2, NO2, O3, and CO were significantly and positively associated with COPD-related mortality in the central Sichuan Basin, which is located in the hinterland of southwestern China. The adverse effects of O3 were stable, a finding that should receive more attention.

WHO DELIVERS IT AND HOW IT IS DELIVERED: EFFECTS OF SOCIAL-EMOTIONAL LEARNING INTERVENTIONS ON LEARNING ANXIETY AND DROPOUT INTENTION

Purpose – Given the prevalence of mental health issues among young adolescents and its detrimental effects on academic functioning, Social- Emotional Learning (SEL) interventions are becoming extremely valuable. The current study aims to investigate the effectiveness of two types of SEL interventions delivered by two different types of teachers to determine their effectiveness for SEL knowledge, learning anxiety, and intention to drop-out. Methodology – This study employed a 2 x 2 factorial and between-subject quasi-experimental design, in which intervention type and teacher type were manipulated to produce four different versions of experiments. A total of 209 students (107 boys, 102 girls) from Grade 8 with a mean age of 14.3 years from Qinzhou City in Southwest China participated in the study. Findings – Factorial and between-group MANOVA revealed that while psychology teacher was more effective in enhancing SEL knowledge and reducing dropout intention, regular teacher was more effective in reducing learning anxiety. TASSEL intervention was more effective in enhancing SEL knowledge while SEL regular intervention was more effective in reducing learning anxiety. Nevertheless, within-group analysis suggested TASSEL with psychology teacher was the best combination in reducing dropout intention while SEL with psychological teacher was the best combination in reducing learning anxiety. Significance – The results have significance for schools and mental health counselling services. The findings can guide the effective design of SEL intervention and appropriate teachers to deliver it.

Measurement report: Seasonality, distribution and sources of organophosphate esters in PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; from an inland urban city in Southwest China

Abstract. Organophosphate esters (OPEs) are contaminants of emerging concern, and studies have concluded that urban areas are a significant source of OPEs. Samples were collected from six ground-based sites located in Chengdu, a typical rapidly developing metropolitan area in Southwest China, and were analyzed for seven OPEs in atmospheric PM2.5 (Σ7 OPEs). The concentrations of Σ7 OPEs in PM2.5 ranged from 5.83 to 6.91 ng m−3, with a mean of 6.6 ± 3.3 ng m−3, and the primary pollutants were tris-(2-butoxyethyl) phosphate (TBEP), tri-n-butyl phosphate (TnBP), tris-(2-chloroethyl) phosphate (TCEP) and tris-(2-chloroisopropyl) phosphate (TCPP), which together made up more than 80 % of the Σ7 OPEs. The concentrations of Σ7 OPEs were higher in autumn and winter than in summer. Nonparametric tests showed that there was no significant difference in Σ7 OPE concentrations among the six sampling sites, but the occurrence of unexpectedly high levels of individual OPEs at different sites in autumn might indicate noteworthy emissions. A very strong correlation (R2 = 0.98, p &lt; 0.01) between the OPEs in soil and in PM2.5 was observed. Backward trajectory analysis indicated that the OPEs in PM2.5 were mainly affected by local sources. Principal component analysis (PCA) revealed that the OPEs in PM2.5 were largely sourced from the plastics industry, interior decoration and traffic emission (34.5 %) and the chemical, mechanical and electrical industries (27.8 %), while the positive matrix factorization (PMF) model revealed that the main sources were the plastics industry and indoor source emissions, the food and cosmetics industry and industrial emissions. In contrast to coastal cities, sustained and stable high local emissions in the studied inland city were identified, which is particularly noteworthy. Chlorinated phosphates, especially TCPP and TCEP, had a high content, and their usage and source emissions should be controlled.

Urban growth and topographical factors shape patterns of spontaneous plant community diversity in a mountainous city in southwest China

Urban ecosystems can host a considerable amount of biodiversity because of the varying habitats created during urban development processes. Spontaneous vegetation is a neglected element of urban biodiversity, and the roles of a city’s natural floristic resources, geomorphic features, and topographic characteristics in shaping spontaneous plant diversity patterns have not been fully clarified. We explored the impact of urban growth and elevation and slope on the diversity patterns of urban spontaneous plant communities in a mountainous city in southwest China. We recorded 279 species belonging to 210 genera and 70 families, with native species accounting for about 85% of the urban spontaneous plants. The magnitude of urban growth and elevation were the most important drivers and they were positively correlated with the γ-diversity patterns in Chongqing. Thus, both urban forms and the city’s natural conditions are important in affecting the urban biodiversity patterns. Furthermore, urban spontaneous plant communities in Chongqing metropolis were mainly dominated by a few widespread, cosmopolitan species, with nearly 50% of the 279 species we recorded being narrowly distributed and rarely occurring species. The distribution of the rare, spontaneous species may be highly dependent on chance dispersal, the legacies of earlier land-use, and the availability of specific habitats. We propose that urban construction and landscape design should maintain appropriate configurations for the habitat type to preserve rarely occurring plant species to increase biodiversity in urban landscapes.

Association between NO2 cumulative exposure and influenza prevalence in mountainous regions: A case study from southwest China

While accumulating evidence shows that air pollution exposure is an important risk factor to influenza prevalence, their association has been inadequately investigated in mountainous regions with dense populations and high humidity. We aim to estimate the association and exposure-outcome effects between exposure to nitrogen dioxide (NO2) and influenza prevalence in a mountainous region with a dense population and high humidity. We investigated 14,993 patients with confirmed influenza cases from January 2013 to December 2017 in Chongqing, a mountainous city in southwest China. We developed distributed lag non-linear models with quasi-Poisson link to take into account the lag and non-linear effects of NO2 exposure on influenza prevalence. We estimated that the cumulative effect of a 10 μg/m3 increase in NO2 with seven-day lag (i.e., summing all the contributions up to seven days) corresponded to relative risk of 1.24 (95% CI: 1.17–1.31) in daily influenza prevalence. Comparing to annual mean of the World Health Organization air quality guidelines of 40 μg/m3 for NO2, we estimated that 14.01% (95% CI: 10.69–17.08%) of the influenza cases were attributable to excessive NO2 exposure. Our results suggest that NO2 exposure could worsen the risk of influenza infection in this mountainous city, filling the gap of relevant researches in densely populated and mountainous cities. Our findings provide evidence for developing influenza surveillance and early warning systems.

Impact of low-level mercury exposure on intelligence quotient in children via rice consumption

Wanshan is a city in southwest China that has several inactive mercury (Hg) mines. The local population are exposed to methylmercury (MeHg) due to the consumption of Hg contaminated rice. The relationship between Hg exposure and the cognitive functions of local children is unknown. This study investigated the relationship between hair Hg concentrations and the intelligence quotient (IQ) of 314 children aged 8-10 years, recruited from three local primary schools in Wanshan area in 2018 and 2019. IQ was evaluated using Wechsler Intelligence Scale for Children - Fourth Edition (WISC-IV). The average THg concentration in children's hair samples was 1.53μgg-1 (range: 0.21-12.6μgg-1), and 65.6% exceeded the United States Environment Protection Agency (USEPA) recommended value of 1μgg-1. Results of logistic regression analysis showed that children with hair Hg≥1μgg-1 were 1.58 times more likely to have an IQ score <80, which is the clinical cut-off for borderline intellectual disability (R2=0.20, p=0.03). Increasing of 1μgg-1 hair Hg resulted in 1 point of IQ loss in Wanshan children, which was.much higher than that via fish consumption. The economical cost due to Hg exposure was estimated to be $69.8 million (9.43% of total GDP) in the Wanshan area in 2018.

Research on the sustainable development process of low-carbon pilot cities: the case study of Guiyang, a low-carbon pilot city in south-west China

China plans to pursue low-carbon development in its low-carbon pilot cities to control greenhouse gas emissions. The low-carbon city development is an important method to achieve sustainable development strategy, while it is also a new city development mode to promote natural ecology, low-carbon economy and social happiness. However, the evaluation process of the low-carbon city is a multiple objective and decision problem. A single indicator cannot comprehensively and objectively evaluate a city’s low-carbon development level, so a comprehensive evaluation index system should be established. So taking Guiyang as a case study, this article constructs 35 evaluating indicators that are based on the basic urban development level and low-carbon urban development level to analyse the economic development, social progress and environmental quality transmutation comprehensively by using the entropy method. The results show that in the whole process of sustainable development, the economic development, social progress and the environmental quality have been greatly improved, but the low-carbon level had been on the low side from 2003 to 2016 in Guiyang. Therefore, Guiyang still has a long way to go to become a low-carbon city, and concrete policies and countermeasures should be taken to promote the low-carbon level. In particular, Guiyang has to strengthen the dual constraint of carbon emission intensity and total carbon emissions, adhere to the development path characterized by low carbon and strive to achieve leapfrog development.

The Application of the Fuzzy Analytic Hierarchy Process in the Assessment and Improvement of the Human Settlement Environment

With the development of urbanization in developing countries, some large cities have experienced rapid population growth and industrial expansion in a short period of time. In order to reasonably expand the scale of the city and guide the orderly outward movement of population and industries, it is urgent to improve the human settlement environment (THSE) in the surrounding areas of large cities. In the case of limited financial funds, different areas around the city need to be improved one by one according to the order of improvement grades. Since THSE is a comprehensive system involving multiple levels and indexes, it is difficult to assess it in a simple way. The previous assessment of THSE mainly focused on qualitative and semi-quantitative aspects, with poor accuracy. In this paper, the author takes JianYang County under the jurisdiction of Chengdu City in Southwest China as an example and uses the Fuzzy Analytic Hierarchy Process (FAHP) to quantitatively calculate the improvement grade of THSE in 55 townships of JianYang County. The author carried out an investigation for more than one year. According to the actual situation of JianYang County, five primary indexes and 22 secondary indexes were selected to establish a comprehensive evaluation index system. This index system contains 1210 statistical data points, and more than 30,000 data points were calculated and derived in this article. Finally, the author calculated the improvement grade of 55 townships by FAHP quantitatively and carried out a horizontal comparison of townships within the same grade to further determine the order of improvement of THSE.

Emergence of human avian influenza A(H7N9) virus infections in Wenshan City in Southwest China, 2017

BackgroundThe emergence of human infection with avian influenza A(H7N9) virus was reported in Wenshan City, southwestern China in 2017. The study describes the epidemiological and virological features of the outbreak and discusses the origin of the infection.MethodsPoultry exposure and timelines of key events for each patient were collected. Samples derived from the patients, their close contacts, and environments were tested for influenza A(H7N9) virus by real-time reverse transcription polymerase chain reaction. Genetic sequencing and phylogenetic analysis were also conducted.ResultsFive patients were reported in the outbreak. An epidemiological investigation showed that all patients had been exposed at live poultry markets. The A(H7N9) isolates from these patients had low pathogenicity in avian species. Both epidemiological investigations of chicken sources and phylogenetic analysis of viral gene sequences indicated that the source of infection was from Guangxi Province, which lies 100 km to the east of Wenshan City.ConclusionsIn the study, a sudden emergence of human cases of H7N9 was documented in urban area of Wenshan City. Chickens were an important carrier in the H7N9 virus spreading from Guangxi to Wenshan. Hygienic management of live poultry markets and virological screening of chickens transported across regions should be reinforced to limit the spread of H7N9 virus.

Chemical characterization and source analysis of water-soluble inorganic ions in PM2.5 from a plateau city of Kunming at different seasons

Abstract Water-soluble inorganic ions (WSIIs) in PM2.5 from different cities have been studied in previous studies. However, the studies of WSIIs in plateau cities are relative deficient. Due to differences in topography, climate and emission sources, the WSIIs characteristics of plateau cities are expected to be different. Here, we determined the concentrations of WSIIs (SO42−, NO3−, NH4+, Ca2+, Mg2+, Na+, K+, F−, Cl−, NO2−) in PM2.5 from different seasons of Kunming, a typical plateau city in southwest China. The data will improve our understanding of the chemical characterization and source of PM2.5 in plateau environment. Our results showed that the secondary aerosols were the main pollutants (contributing >50% to PM2.5) in PM2.5 of Kunming, which mainly from coal combustion, agricultural activities and vehicle exhaust. Seasonally, high volatility of the NO3− and NH4+ and washout effects of rainfall in hot months (wet seasons) were favorable for the decreased of pollutants, while high emission, poor dispersion conditions and low removal rate could lead to the increased of pollutants in cold months (dry seasons). It suggested that adequate NH3 and intense solar radiation promotes the photochemical reactions of SO2, NOx and NH3 to form NH4HSO4, (NH4)2SO4 and NH4NO3. High temperature in hot months would promote the volatilization of NH4NO3 in Kunming.

Contamination, morphological status and sources of atmospheric dust in different land-using areas of a steel-industry city, China

To know about the element composition, morphology and potential Pb-sources of the atmospheric dust in a steel-industry city in southwest China, the atmospheric dust samples were collected from three different land-using areas, including heavy traffic areas (HTA), residential areas (RA) and industrial areas (RA) were analysed by ICP-MS, SEM-EDX and MC-ICP MS. Results showed the atmospheric dust particles in Panzhihua were characterized by spherical, massive, columnar, layered, and irregular morphologies, and the particles containing minerals were mainly composed of quartz, calcite, gypsum, feldspar, dolomite, iron and titanium minerals. The average concentrations of Zn (795.9 μg/g), Pb (225.3 μg/g), Cr (507.3 μg/g), Cu (134.7 μg/g) in atmospheric dust were higher than the local soil background values except Cd (0.86 μg/g). Lead was enriched in these areas, and it was on “significant enrichment” level. The potential ecological risk index (RI) is in low pollution risk in these three areas. The results of lead isotopic ratios showed that the main sources of lead in atmospheric dust in Panzhihua City were smelting, motor vehicle exhaust and soil. Based on the results of the Pb ternary mixed model, these sources contributed an average of 50.97%, 29.41% and 19.62% of the lead in atmospheric dust, respectively.

Spatiotemporal clusters of HIV/AIDS infections caused by drug use and heterosexual contact in Ruili city, China 1989\u20132016

BackgroundRuili is a border city in southwest China along the heroin trafficking route. In recent decades, the city has witnessed increased in HIV transmission. The current study aims to explore the spatiotemporal trends in HIV prevalence identify and map the spatial variation and clustering of factors associated with HIV transmission through drug use and heterosexual contact transmissions at the village level from 1989 through 2016.MethodsGeographic information system-based spatiotemporal analyses, including global and local spatial autocorrelation analyses and space-time scanning statistics, were applied to detect the location and extent of HIV/AIDS high-risk areas.ResultsDrug use and heterosexual contact were identified as the major transmission routes causing infection in Ruili. Results of global spatial analysis showed significant clustering throughout the city caused by transmission via drug use in the early phase of the epidemic and transmission via heterosexual contact in the late phase of the epidemic during the study period. Hotspots of transmission from drug use were randomly distributed throughout the city. However, the hotspots of transmission by heterosexual contact were located in the central area only around the Jiegao China-Myanmar land port. Space-time scanning showed that transmission from drug use clustered in the southwest area between 1989 and 1990, while transmission by heterosexual contact clustered in the central area between 2004 and 2014.ConclusionsHeterosexual contact has become the dominant mode of transmission. Interventions should focus on highly clustered area where is around the Jiegao land port.

Estimation of the Effects of Air Pollution on Hospitalization Expenditures for Asthma

This article aims to estimate the effects of air pollutants (PM2.5, PM10, SO2, and NO2) on the hospitalization expenses of adult patients admitted due to asthma. The data is sourced from the medical health database of a city in Southwest China, which involves approximately 14 million residents. A generalized additive model using a Poisson distribution was utilized to identify the effects of air pollution on the cost of hospitalization due to asthma. Hospital admissions were stratified by sex, age, season, and type of medical insurance to specialize the results. Air pollution significantly affects hospitalization expenses for asthma. These effects were more significant in the male, non-senior subgroups than in the female, senior subgroups. The difference also significantly existed in different insurance type subgroups. Air pollution has adverse effects on hospitalization expenses for asthma. Climate change is now deeply affecting the world in the aspects of economy and health. Based on our research, policymakers can establish more effective air pollution reduction policies and measures that can control the levels of ambient air pollutants, which help save health care resources and improve the welfare of the population by easing the climate change.

Correlation between indoor air pollution and adult respiratory health in Zunyi City in Southwest China: situation in two different seasons

BackgroundIndoor environmental quality significantly influences the occurrence of asthma attack. Zunyi District has abundant coal reserves and is regarded as one of the cities that are most severely polluted by high levels of particulate matter in China. This study aimed to examine the correlation of indoor exposure with adult respiratory health, as well as the differences in effect between winter and summer.MethodsA cross-sectional epidemiological study was conducted among 1207 adult residents in Zunyi, Guizhou Province of Southwest China in winter and summer. Data on health variables related to asthma and home environmental factors were collected using a modified European Community Respiratory Health Survey II questionnaire. The following data were obtained: samples of particulate matter 2.5 (PM2.5) inside and outside the households under study (n = 20); lung function status, including peak expiratory flow rate, forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and FEV1/FVC ratio.ResultThe odds ratio (OR) for asthma-like symptoms and asthma in adults using coal stove for cooking or warming, relative to non-users, was 1.73 (95% CI, 1.11–2.69) in winter vs. 1.30 (95% CI, 0.79–2.14) in summer. Adult residents with exposure to cooking oil fumes were at a considerably higher risk of asthma-like symptoms and asthma [OR = 2.65 (95% CI, 1.25 to 5.61) in winter vs. OR = 7.93 (95% CI, 2.54 to 24.75] in summer] than those without such exposure. The prevalence of asthma-like symptoms and asthma was significantly higher in adults with high kitchen risk scores or high sleeping-area risk scores than in those with low scores in both seasons (p < 0.05). The relative kitchen and sleeping area PM2.5 concentrations were higher in winter than in summer (p < 0.05). Lung function was negatively associated with indoor kitchen and sleeping area relative PM2.5 concentration in winter rather than summer (p < 0.001). The effect of exposure to indoor risk factors on lung function among the residents was greater in winter than in summer (p < 0.001).ConclusionExposure to indoor risk factors, such as aerocontaminants from coal combustion, causes asthma symptoms and reduces pulmonary function. The effect of indoor risk factors on respiratory health among adults with such exposure was greater in winter than in summer.

Sources and gas-particle partitioning of atmospheric parent, oxygenated, and nitrated polycyclic aromatic hydrocarbons in a humid city in southwest China

Polycyclic aromatic hydrocarbons (PAHs) derivatives, such as oxygenated PAHs (OPAHs) and nitrated PAHs (NPAHs), some of which are more toxic and persistent than parent PAHs, have been ubiquitously detected in the environment. Gaseous and particulate PAHs, OPAHs, and NPAHs in the air were measured in an urban environment of Chongqing in southwest China in 2016. Annual average concentrations were 79.9 ± 40.5 ng/m³, 93.7 ± 75.2 ng/m³ and 1.65 ± 1.43 ng/m³ for ∑29 PAHs, ∑10 OPAHs and ∑27 NPAHs, respectively. PAHs had highest level in winter and lowest level in summer while NPAHs and OPAHs showed relatively higher concentrations in summer than spring and autumn, which may be explained by stronger secondary formation of NPAHs and OPAHs in summer. Source apportionment analysis revealed that biomass burning, coal combustion, and petroleum combustion were the main sources for PAHs, while secondary formation, especially in summer, contributed greatly to OPAHs and NPAHs. Gas/particle partition coefficient (logKP) of PAHs, OPAHs and NPAHs, calculated from our observation data, was found to correlate well with the corresponding subcooled liquid vapor pressures (logPLo). The shallower slope of the linear regression between logKP and logPLo for PAHs (−0.61 to −0.52) than OPAHs or NPAHs (−2.14 to −0.73) indicated stronger absorption into the atmospheric particles for PAHs. Three gas/particle partitioning models were evaluated, including the Junger-Pankow adsorption model, the KOA absorption model, and the Dual octanol-air/soot-air model. Compared to the measured values of particle-bound fractions, model predicted values were in reasonable range for PAHs, but were underestimated for NPAHs and OPAHs, suggesting that other important factors such as the influence of RH should be incorporated in gas/particle partitioning models for less hydrophobic compounds, especially in humid areas.

An Investigation of Soundscape Factors Influencing Perceptions of Square Dancing in Urban Streets: A Case Study in a County Level City in China.

Square dancing is a popular music-related group physical exercise for health benefits in China mainly participated by mid-aged women and elderly people. This paper investigates the soundscape and enjoyment of the square dancing in urban streets through a case study in Lichuan, a county level city in southwest China, in December 2017. It examines the impact of gender, age, participation and places on perceptions of square dancing soundscape. Two sites along two main urban streets in the city were selected to conduct onsite investigations where residents spontaneously perform square dancing on a daily basis. Ethnographical observations were conducted to identify the social-physical features and sounds of both sites during the dance and without dance. Sound pressure measurements (LAeq and LAmax) were also conducted under the two conditions. An off-site survey was distributed through the local social media groups to understand residents’ everyday experiences and perceptions of square dancing in the city; 106 responses were received for the off-site survey. T-tests and Chi-squared tests were used for statistical analysis of the survey data. The results show gender does appear to be a factor influencing the regularity of participation in square dancing, with a bias towards more female participants. Participation frequency of square dance has an impact on the enjoyment of square dancing. There is no correlation between the dislike of watching square dancing, or dislike of the music and a desire to restrict locations for square dancing.

Modelling spring discharge and solute transport in conduits by coupling CFPv2 to an epikarst reservoir for a karst aquifer

Karst aquifers differ from unconsolidated granular aquifers with respect to their groundwater flow behavior because of the dual-permeability characteristics (discrete conduit network coupled to a fissured matrix), the duality of recharge (point vs. diffuse recharge) as well as the duality of flow (laminar vs. turbulent state). In many karst aquifers, the epikarst frequently plays an important role in redistributing precipitation as diffuse recharge into the fissured matrix and as point recharge into the conduit network as well as for the temporal distribution of recharge input. In this paper, a coupled groundwater model CE (CFPv2 + ERCH) is developed, consisting of a combination of a simple reservoir model generating the recharge source function assuming the concept of an epikarst horizon (ERCH) with CFPv2, a discrete conduit-continuum groundwater flow model of the phreatic karst aquifer. The CE model is applied to simulate spring discharge and a tracer breakthrough in a karst aquifer near Guilin City in southwest China. In order to examine the effect of an added epikarst reservoir model, simulations are carried out with CFPv2 but without including ERCH. Simulation results of both, spring hydrograph and tracer breakthrough, indicate that CFPv2 with ERCH performs much better. A sensitivity analysis of the CE reveals the relative importance of parameters characterizing the epikarst reservoir. Point recharge is a main factor determining the large variation in spring discharge and its proportion to total recharge can reach 58%. These simulation results highlight the importance of the temporal and spatial distribution of recharge to karst spring discharge response. The coupled model provides an effective approach to include the effect of an epikarst zone in CFPv2 and it can easily be applied for the simulation of karst aquifers with similar characteristics as the study site.

A Sharp Decline in Nitrogen Input in a N‐Saturated Subtropical Forest Causes an Instantaneous Reduction in Nitrogen Leaching

AbstractIn China, as in other parts of the world, the emission and deposition of reactive nitrogen (N) have been reduced in recent years. Several decades of elevated N deposition in southwest China (40 to 60 kg ha−1 year−1) have resulted in extreme cases of N saturation, where N outputs are nearly equal to N inputs. Doubling N inputs using either NH4NO3or NaNO3fertilizer in a subtropical forest in Tieshanping, near Chongqing city in southwest China, caused an immediate doubling of N leaching (as NO3−). Reducing N inputs to ambient atmospheric deposition levels after 10 years of fertilization led to a rapid decrease in soil water NO3−concentration to levels similar to those in the reference plots that had not receive N fertilizer application. NO3−leaching via the soil water in the NH4NO3plots was even lower than that in the NaNO3plots or the reference plots, confirming the finding of a previous N‐fertilizing experiment that found that NH4+deposition, in contrast to NO3−deposition, increased N retention in the forest ecosystem. The N sink remained for at least 2 years after the cessation of N addition. Even with reduced N inputs, ambient atmospheric N deposition caused significant acidification, buffered partly by SO42−sorption. Therefore, further abatement of reactive N emissions is necessary in the future.

Characterization of water soluble inorganic ions and their evolution processes during PM2.5 pollution episodes in a small city in southwest China

PM2.5 samples were collected in four segregate one-month periods, each representing one season, for analyzing their contents of water soluble inorganic ions (WSIIs) in a small city inside Sichuan Basin. Daily PM2.5 concentrations ranged from 23.2 to 203.1 μg m−3 with an annual mean of 66.9 ± 33.6 μg m−3. Annual mean concentrations of WSIIs was 28.8 ± 20.3 μg m−3, accounting for 43.1% of PM2.5. Seasonal mean concentrations of WSIIs ranged from 17.5 ± 9.3 μg m−3 in summer to 46.5 ± 27.6 μg m−3 in winter. Annual mean mass ratio of NO3−/SO42− was 0.49, demonstrating predominant stationary sources for secondary inorganic aerosols (SNA, including SO42−, NH4+ and NO3−); whereas annual mean molar ratio of [NH4+]/[NO3−] was 3.5, suggesting dominant agriculture emissions contributing to the total nitrogen. During a severe and long-lasting (13 days) winter pollution period when mean PM2.5 concentration reached to 132.5 μg m−3, PM2.5 concentration was enhanced by a factor of 2.6 while that of SNA by a factor of 2.9 compared to those before the pollution event, and the fraction of SNA in PM2.5 only increased slightly (from 46.7% to 50.6%). Thus, local accumulation of pollutants under poor diffusion conditions played a major role causing the extremely high PM2.5 concentration, besides the contributions from the enhanced SNA formation under specific weather conditions.

Nitrogen deposition increases N2O emission from an N-saturated subtropical forest in southwest China

Nitrous oxide (N2O) is a major greenhouse gas, with elevated emission being reported from subtropical forests that receive high nitrogen (N) deposition. After 10 years of monthly addition of ammonium nitrate (NH4NO3) or sodium nitrate (NaNO3) to a Mason pine forest at Tieshanping, near Chongqing city in Southwest China, the simulated N deposition was stopped in October 2014. The results of soil N2O emissions monitoring in different seasons during the nitrogen application period showed that nitrogen addition significantly increased soil N2O emission. In general, the N2O emission fluxes were positively correlated to nitrate (NO3−) concentrations in soil solution, supporting the important role of denitrification in N2O production, which was also modified by environmental factors such as soil temperature and moisture. After stopping the application of nitrogen, the soil N2O emissions from the treatment plots were no longer significantly higher than those from the reference plots, implying that a decrease in nitrogen deposition in the future would cause a decrease in N2O emission. Although the major forms of N deposition, NH4+ and NO3−, had not shown significantly different effects on soil N2O emission, the reduction in NH4+ deposition may decrease the NO3− concentrations in soil solution faster than the reduction in NO3− deposition, and thus be more effective in reducing N2O emission from N-saturated forest soil in the future.