High Concentrations Of NO Research Articles

In Operando Investigation of the Concentration Dependent NO2 Sensing Mechanism of Bi2S3 Nanorods at Low Temperatures and the Interference of O3.

The demand for gas sensors that can detect gases selectively at low temperatures has increased steadily over recent years. Most devices use semiconducting metal oxides as sensing materials which often require high operation temperatures and suffer from a lack of selectivity. Semiconducting metal sulfides were found to be a reasonable alternative for the application in sensing devices at low temperatures. Since metal sulfides are a relatively new class of materials applied in gas sensors, there is little work on sensing mechanisms and overall sensing characteristics of these materials. In this work, the authors investigated the sensing performance of Bi2S3 nanorods operated at 50 °C in the presence of several target gases and found a selective response to oxidizing gases. With the help of DC resistance measurements, diffuse reflectance infrared Fourier transform spectroscopy and work function measurements in a Kelvin Probe setup, the NO2 and O3 sensing mechanisms of Bi2S3 nanorods were revealed. While initially sulfur vacancies were the predominant reaction sites, the formation of nitrates became the key reaction in higher NO2 concentrations. Additionally, it was found that the reaction with O3 healed sulfur vacancies effectively inhibiting the reaction with NO2.

Hydrogeochemical characterization of groundwater and their associated potential health risks.

The present study assessed the human health risk exposure from the consumption of poor quality groundwater in the Lucknow area, a part of Central Ganga alluvial plain in India. Around 27 (n = 27) groundwater samples were collected from the study area. The analytical results of the samples (n = 27) collected indicate silicate and carbonate weathering is the dominant process along with cation exchange, sulfide oxidation, and reverse ion exchange. The type of groundwater is Ca2-Na-HCO3- type having all cations and anions within permissible WHO limits except for iron (Fe2+) and nitrate (NO3-). The high concentrations of Fe2 and NO3- in samples indicate the possibility of a non-geogenic point source for the same in an urban-influenced environment. The ionic concentration of dissolved constituents is used in weighted overlay analysis to generate the water quality index (WQI). WQI indicates that most urban areas (~ 98.52%) have fallen in the good to excellent category except few situated in the highly populated parts of Lucknow. The ionic concentrations of Fe2+ and NO3- have been further used to estimate human health risk by integrating regional urban population density data in Lucknow. The risk map shows alarming risks in the west-central part, where nearly ~ 35% of the total area is at moderate to high health risk.

Using a soft computing OSPRC risk framework to analyze multiple contaminants from multiple sources; a case study from Khoy Plain, NW Iran

Water shortage in arid and semi-arid areas like Iran makes groundwater contamination a crucial issue. In the Khoy aquifer, NW Iran, contaminants (e.g., arsenic (As), nitrate (NO3−), lead (Pb), and zinc (Zn)) may originate from both geological and anthropogenic sources. The objectives of the study are to (1) employ soft modeling framework to abstract available hydrogeochemical information into a perceptual model and (2) build a conceptual model using the risk cells (RCs) by applying the following two steps: (i) study Origin-Source-Pathways-Receptor-Consequence (OSPRC) as a risk system; and (ii) apply “soft modeling” as a set of diverse and classical tools including graphical representations, geological surveys, and multivariate statistical analysis to validate the information by evaluating their convergence or divergence behaviors among different tools used for investigating the groundwater contaminants. According to the perceptual model, the Khoy aquifer contains four RCs. RC4 (southern of plain) and RC2 (northern of the plain) contain high levels of As, while RC2 contains high amounts of Zn. In RC1 (northern of plain) and RC3 (middle of plain), a high concentration of Pb is detected, while in RC3 and RC4, there is a high concentration of NO3−. It was found that a soft modeling approach can only identify the dominant hydrogeochemical processes for each RC as a descriptive model, rather than the use of quantitative models if sufficient data are available.

Association between ambient air pollution and polycystic ovarian syndrome: A 2010-2019 national populational-based cohort study in Korea

Background: Several studies have indicated that prenatal exposure to ambient air pollution is associated with an increased risk of gestational diabetes mellitus, hypertensive disorder during pregnancy, preterm birth, and stillbirth. However, no previous study has focused on the association between the number of pregnancy complications and exposure to ambient air pollution. Objectives: To investigate the association between prenatal exposure to ambient air pollutants and the number of pregnancy complications in high-risk pregnancies. Methods: We collected data on gestational diabetes mellitus, hypertensive disorder during pregnancy, preterm birth, and stillbirth from the National Health Information Databases, provided by the Korean National Health Insurance Service. To assess individual-level exposure to air pollutants, a spatial prediction model and area-averaging approach were used. Results: From 2015 to 2018, data of 789,595 high-risk pregnancies were analyzed. The ratio of gestational diabetes mellitus in the country was the highest, followed by preterm birth, hypertensive disorder during pregnancy, and stillbirth. Approximately 71.7% of pregnant women (566,143) presented with one pregnancy complication in identical pregnancies, 27.5% (216,714) presented with two, and 0.9% (6738) presented with three or more. Multiple logistic regression models with adjustments for age, residence, and income variables indicated that the risk of having two or more pregnancy complications was positively associated with the exposure to higher levels of PM10 (odds ratio [OR], 1.11; 95% confidence interval [CI], 1.09–1.12) and PM2.5 (OR, 1.14; 95% CI, 1.12–1.15). The highest quartile presented higher odds of two or more pregnancy complications compared with the lower three quartiles of PM10, PM2.5, CO, NO2, and SO2 exposures (p < 0.001). Conclusion: The results indicate that the risk of pregnancy complications is positively associated with the exposure to the high concentrations of PM10, PM2.5, CO, NO2, and SO2.

Effects of Urban Landscapes on Pollutant Concentrations in Chengdu Plain Urban Agglomeration

Frequent air pollution due to urbanization poses a severe threat to urban environments. In this study, the effects of urban landscapes on pollutant concentrations at different spatial and temporal scales are examined using “3S” technology, based on land-use (LU) classification maps for two time phases (2015 and 2018) in conjunction with monitoring data for air pollutants of the same periods. The results showed that: (1) A very high overall LU ratio was found for Chengdu Plain urban agglomeration (CPUA), with only 0.3% of the land being unused. Farmlands (43%), forests (36.45%), and grasslands (14.17%) were identified as the main landscape types. A decrease in the proportions of the total area occupied by farmlands and grasslands was 0.44% and 0.72%, respectively, and 0.10%, 0.04%, and 0.97% increased in the proportions of the total area occupied by forests, water bodies, and developed lands, respectively, were found from 2015 to 2018. (2) NO2, PM2.5, and PM10 were mainly distributed in the central and eastern parts of the study area, while SO2 was mainly distributed in the southwest. In 2018, compared with 2015, the maximum concentration of NO2 decreased from 60.36 μg/m3 to 49.75 μg/m3, and the distribution range of high concentration NO2 was reduced and concentrated in Chengdu; the concentrations of PM10 and PM2.5 decreased significantly, and the maximum concentration decreased by 20.53% and 23.93%, respectively, but the concentration of pollution in the northeast increased significantly. The scope of SO2 pollution had shifted from the south to the southwest, and the pollution level had decreased from south to north. (3) The effects of various landscape types on pollutant concentrations were complex. At a patch-type level, increasing the area proportions of “pollution-reducing” landscape types could reduce pollutant concentrations. Specifically, increasing the area, largest patch index, and patch cohesion of forests and grasslands, as well as reducing the area, largest patch index, and patch cohesion of farmlands and developed lands, could effectively lower pollutant concentrations. From a landscape pattern perspective, high shape regularity and low diversity of landscape patches resulted in high concentrations of NO2, PM10, and PM2.5. In contrast, high levels of dominance and aggregation of landscapes lead to low concentrations of SO2.

The association between air pollution, meteorological factors, and daily outpatient visits for urticaria in Shijiazhuang, Hebei Province, China: a time series analysis.

The associations of air pollution and meteorological factors with the outpatient visits of urticaria remain poorly studied. This study aimed to assess the association between air pollution, meteorological factors, and daily outpatient visits for urticaria in Shijiazhuang, China, during 2014-2019. Daily recordings of air pollutant concentrations, meteorological data, and outpatient visits data for urticaria were collected during the 6years. Descriptive research methods were used to describe the distribution characteristics and demographic features of urticaria. A combination of the generalized linear regression model (GLM) and distribution lag nonlinear model (DLNM) was used to evaluate the lag association between environmental factors and daily outpatient visits for urticaria. Stratified analyses by gender (male; female) and age (< 18years; 18-39years; > 39years) were further conducted. The dose-response relationship between daily urticaria visits and CO, NO2, O3, temperature, and relative humidity was nonlinear. High concentrations of CO, NO2, O3, and high temperatures increased the risk of urticaria outpatient visits. The maximum cumulative association of high concentrations of CO, NO2, and O3 was lag 0-14days (CO: RR = 1.10, 95%CI: 1.06, 1.31; NO2: RR = 1.09, 95%CI: 1.01, 1.08; O3: RR = 1.16, 95%CI: 1.08, 1.25), and high temperatures was lag 0-7days (RR = 1.27, 95%CI: 1.14, 1.41). Low concentrations of NO2, O3, and high humidity, on the other hand, act as protective factors for urticaria outpatient. The maximum cumulative association of low concentrations of NO2 was the 0-day lag (RR = 0.97, 95%CI: 0.95, 0.99), O3 was lag 0-5days (RR = 0.94, 95%CI: 0.88, 0.99), and high humidity was lag 0-10days (RR = 0.93, 95%CI: 0.89, 0.98). Stratified analyses showed that the risk of urticaria outpatient visits was higher for the males and in the < 18years age group. In conclusion, we found that the development of urticaria in Shijiazhuang has a distinct seasonal and cyclical nature. Air pollutants and meteorological factors had varying degrees of influence on the risk of urticaria outpatient visits. This study provides indirect evidence for a link between air pollution, meteorological factors, and urticaria outpatient visits.

Increased risk of emergency department presentations for bronchiolitis in infants exposed to air pollution.

Air pollution has been linked to an increased risk of several respiratory diseases in children, especially respiratory tract infections. The present study aims to evaluate the association between pediatric emergency department (PED) presentations for bronchiolitis and air pollution. PED presentations due to bronchiolitis in children aged less than 1 year were retrospectively collected from 2007 to 2018 in Padova, Italy, together with daily environmental data. A conditional logistic regression based on a time-stratified case-crossover design was performed to evaluate the association between PED presentations and exposure to NO2 , PM2.5, and PM10. Models were adjusted for temperature, relative humidity, atmospheric pressure, and public holidays. Delayed effects in time were evaluated using distributed lag non-linear models. Odds ratio for lagged exposure from 0 to 14 days were obtained. Overall, 2251 children presented to the PED for bronchiolitis. Infants' exposure to higher concentrations of PM10 and PM2.5 in the 5 days before the presentation to the PED increased the risk of accessing the PED by more than 10%, whereas high concentrations of NO2 between 2 and 12 days before the PED presentation were associated with an increased risk of up to 30%. The association between pollutants and infants who required hospitalization was even greater. A cumulative effect of NO2 among the 2 weeks preceding the presentation was also observed. In summary, PM and NO2 concentrations are associated with PED presentations and hospitalizations for bronchiolitis. Exposure of infants to air pollution could damage the respiratory tract mucosa, facilitating viral infections and exacerbating symptoms.

Stimulation of high-concentration dissolved nitrogen and reactive phosphorus in Lake Taihu sediments on the initiation and maintenance of cyanobacterial blooms

The spatio-temporal variation of dissolved inorganic nitrogen (DIN: NH4+-N, NO2−-N, and NO3−-N) and dissolved reactive phosphorus (DRP) in Meiliang Bay of Lake Taihu sediments and their potential effects on the cyanobacterial blooms were studied. Monthly sampling was performed using high-resolution dialysis sampling devices (HR-Peeper) and two important results were observed in April (the initiation period of cyanobacterial bloom) and June–August (the maintenance period of cyanobacterial blooms). In April, high concentrations of dissolved NO2−-N and NO3−-N, probably caused by the groundwater influx, were observed in deep anoxic sediments (below 110 mm). NO2−-N and NO3−-N are good electron acceptors for the mineralization of organic P under anaerobic conditions and should lead to an increase in DRP concentrations in sediments, DRP released from sediments thus further stimulating the cyanobacterial growth and the outbreak of severe cyanobacterial blooms in May due to the extremely low concentrations of DRP in the water body. From June to August, high concentrations of NO2−-N, NO3−-N, and DRP were observed in the surface sediment, which was caused by the release of NH4+-N from the mineralization of cyanobacterial debris. This should play an important role in maintaining cyanobacterial growth, especially in stimulating the occurrence of cyanobacterial blooms during September, when N and P were co-limited. This study revealed high-concentration DIN and DRP in Lake Taihu sediments potentially stimulated the initiation and maintenance of cyanobacterial blooms.

Denitrification kinetics during aquifer storage and recovery of drainage water from agricultural land

An aquifer storage transfer and recovery (ASTR) system was studied in which tile drainage water (TDW) was injected with relatively high NO3 (about 14 mg/L) concentrations originating from fertilizers. Here we present the evolution of denitrification kinetics at 6 different depths in the aquifer before, and during ASTR operation. First-order denitrification rate constants increased over time before and during the first days of ASTR operation, likely due to microbial adaptation of the native bacterial community and/or bioaugmentation of the aquifer by denitrifying bacteria present in injected TDW. Push-pull tests were performed in the native aquifer before ASTR operation. Obtained first-order denitrification rate constants were negligible (0.00–0.03 d−1) at the start, but increased to 0.17–0.83 d−1 after a lag-phase of about 6 days. During the first days of ASTR operation in autumn 2019, the arrival of injected TDW was studied at 2.5 m distance from the injection well. First-order denitrification rate constants increased again over time (maximum >1 d−1). Three storage periods without injection were monitored in winter 2019, fall 2020, and spring 2021 during ASTR operation. First-order rate constants ranged between 0.12 and 0.61 d−1. Denitrification coupled to pyrite oxidation occurred at all depths, but other oxidation processes were indicated as well. NO3 concentration trends resembled Monod kinetics but were fitted also to a first-order decay rate model to facilitate comparison. Rate constants during the storage periods were substantially lower than during injection, probably due to a reduction in the exchange rate between aquifer solid phases and injected water during the stagnant conditions. Denitrification rate constants deviated maximally a factor 5 over time and depth for all in-situ measurement approaches after the lag-phase. The combination of these in-situ approaches enabled to obtain more detailed insights in the evolution of denitrification kinetics during AS(T)R.

Groundwater Quality Assessment in the Northern Part of Changchun City, Northeast China, Using PIG and Two Improved PIG Methods.

As a numerical indicator, the pollution index of groundwater (PIG) has gained a great deal of popularity in quantifying groundwater quality for drinking purposes. However, its weight-determination procedure is rather subjective due to the absolute dependence on experts’ experience. To make the evaluation results more accurate and convincing, two improved PIG models (CRITIC-PIG and Entropy-PIG) that integrate subjective weights and objective weights were designed, and they were employed to appraise groundwater suitability for drinking purposes in the northern part of Changchun City. A total of 48 water samples (34 unconfined water samples and 14 confined water samples) with abundances of Ca2+ and HCO3− were collected and tested to obtain the data for the analyses. The results showed that 60.4%, 47.9% and 60.4% of the water samples manifested insignificant pollution and were marginally potable based on the values of the PIG, CRITIC-PIG and Entropy-PIG, respectively. Though 48% of the water samples had different evaluation results, their level difference was mostly 1, which is relatively acceptable. The distribution maps of the three sets of PIG values demonstrated that the quality of groundwater was the best in Dehui City and the worst in Nongan County. Groundwater contamination in the study area was mainly caused by the high concentrations of TDS, TH, Fe3+, F− and NO3−, which not only came from geogenic sources but also anthropogenic sources.

A non-threshold model to estimate carcinogenic risk of nitrate-nitrite in drinking water

Understanding nitrate–nitrite ( NO 3 − − NO 2 − ) levels in drinking water and the associated non-carcinogenic and carcinogenic health risks are essential to protect public health. The non-carcinogenic risk assessment of NO 3 − – NO 2 − in drinking water has been well documented, however, there remains a knowledge gap in understanding and quantification of the carcinogenic risk of NO 3 − – NO 2 − . This study develops a non-threshold–based model for estimation of carcinogenic risk of NO 3 − – NO 2 − ingested through drinking water for a densely populated urban area with a case study of Tehran's potable water (TPW). In this regard, 200 tap water samples from different parts of the city were taken in wet (May 2018) and dry (October 2018) periods to determine NO 3 − – NO 2 − concentration in the TPW and the associated health risks across different groups of end-users. Sampling results reveal higher concentrations of NO 3 − – NO 2 − during the dry period, which can be associated to the significant contribution of nitrogen–rich groundwater in supplying the city's water demands during the dry period. Findings suggest concerns associated with the non-carcinogenic risk of NO 3 − – NO 2 − in the TPW, especially for children. More than 55% of the samples taken during the dry period show a positive carcinogenic risk for all groups of end-users (68% for men, 72% for women, and 56% for children) whilst just 8% of the samples are deemed unsafe with regards to the permissible NO 3 − level in drinking water, i.e. 50 mg/L. Approximately, 45% of the samples taken during the wet period show a positive carcinogenic risk for adults whilst the maximum concentration of NO 3 − was about 23 mg/L, i.e. two times less than the permissible level in drinking water. The findings emphasize on the necessity of reducing the permissible level of NO 3 − in drinking water, set out by the existing water quality standards , to safeguard public health against the carcinogenic risks. The model developed within this study recommends the urgent need for reduction of NO 3 − level in Tehran's water resources to protect public health of over 13 M population who incessantly use the TPW. • A model is developed to estimate carcinogenic risk of NO 3 − in drinking water. • Non-carcinogenic risk of NO 3 − – NO 2 − was observed in Tehran's drinking water. • Majority of samples taken in dry period show a positive carcinogenic risk of NO 3 − • The permissible level of NO 3 − does not safeguard human health vs carcinogenic risks.

Vertical distributions and potential sources of wintertime atmospheric pollutants and the corresponding ozone production on the coast of Bohai Sea

This study investigated the wintertime vertical distributions and source areas of aerosols, NO2, and HCHO in a coastal city of Dongying from December 2020 to March 2021, using ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) and a potential source contribution function (PSCF) model, respectively. Moreover, the chemical production sensitivity of O3 at different height layers was analyzed using HCHO/NO2 ratios. The results revealed that the wintertime averaged highest concentrations of aerosol (1.25 km−1), NO2 (14.81 ppb), and HCHO (2.32 ppb) were mainly distributed at the surface layer, 100–200 m layer, and 200–300 m layer, respectively. Regarding the diurnal cycles, high concentrations of aerosol (>1.4 km−1) and NO2 (>16.0 ppb) usually appeared in the early morning and late afternoon, while high concentrations of HCHO (>2.5 ppb) usually occurred during 12:00–15:00. The PSCF model revealed that the wintertime aerosol mainly originated from Shandong, northern Jiangsu, Korea, and the northwestern Mongolian Plateau. Below 200 m, NO2 was mainly from western Shandong, whereas above 600 m, it was mainly from northern Shandong and the Beijing-Tianjin-Hebei (BTH) region. The corresponding sources for HCHO were central and southern Shandong (below 200 m) and northern Shandong, northern Jiangsu, and southeastern BTH (above 600 m). In addition, the chemical production sensitivity of O3 below 100 m was observed only in the VOC-limited regime. The percentages of O3 production under the NOx-limited, NOx-VOC-limited, and VOC-limited regimes were 10.75% (31.18%), 4.30% (19.35%), and 84.95% (49.47%) at the 500–600 m (900–1000 m) layer. This study has guiding significance for the coordinated control of PM2.5 and O3, and can assist in the implementation of regional joint prevention and control strategies for air pollutants.

Alterations of IL-1beta and TNF-alpha expression in RAW264.7 cell damage induced by two samples of PM2.5 with different compositions.

Fine particulate matter 2.5 (PM2.5) has been demonstrated by previous studies to be associated with cell damage. To explore the impact of the composition of PM2.5 on PM2.5-mediated inflammation, this study investigated the composition of PM2.5 collected during the wintertime indoor heating season and observed its inflammatory effect. Samples were collected during the heating season from December 5, 2017, to January 8, 2018, in Xi'an. Compositions of organic carbon (OC), elemental carbon (EC), and water-soluble ions were analysed. Two representative samples (sample 1 and 2) were selected with significant differences in compositions. They were configured into four concentrations (0.1 μg/mL, 1 μg/mL, 10 μg/mL, 20 μg/mL) and used as interventions on RAW264.7 cells for 4 h and 24 h separately. Cell viability was detected by CCK-8. Tumour necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) gene and protein expression levels were detected by real-time quantitative real-time polymerase chain reaction (RT-qPCR) and western blotting. The results showed that the cell viability of sample 1 intervened cells at 4 h and 24 h was lower than that of sample 2. IL-1β gene in most PM2.5 intervention groups was lower than in the control group. Protein expression was higher at 4 h than at 24 h. In conclusion, PM2.5 components influence cell viability and expression of IL-1β and TNF-α, while high concentrations of NO3-, Cl-, Na+, K+, Mg2+, Ca2+, and others in the PM2.5 composition have a significant harmful effect.

Does Long-Term Air Pollution Exposure Affect Self-Reported Health and Limiting Long Term Illness Disproportionately for Ethnic Minorities in the UK? A Census-Based Individual Level Analysis

Previous studies have investigated the impact of air pollution on health and mortality. However, there is little research on how this impact varies by individuals’ ethnicity. Using a sample of more than 2.5-million individuals aged 16 and older from the 2011 UK census linked to 10-years air pollution data, this article investigates the effect of air pollution on self-reported general health and limiting long-term illness (LLTI) in five main ethnic groups and by country of birth in UK. The association of air pollution with self-reported health and LLTI by individual’s ethnicity was examined using two levels mixed-effects generalised-linear models. Pakistani/Bangladeshi, Indian, Black/African/Caribbean, and other ethnic minorities and people born outside UK/Ireland were more likely to report poorer health and the presence of LLTI than White-group and UK/Ireland born individuals. Higher concentrations of NO2, SO2 and CO pollutants were associated with poorer self-reported health and the presence of LLTI in the UK population. Analysis by ethnicity showed a more pronounced effect of NO2, PM10, PM2.5, and CO air pollution on poor self-reported health and the presence of LLTI among ethnic minorities, mostly for people from Black/African/Caribbean origin compared to White people, and among non-UK/Ireland born individuals compared to natives. Using a large-scale individual-level census data linked to air pollution spatial data, our study supports the long-term deteriorating effect of air pollution on self-reported health and LLTI, which is more pronounced for ethnic minorities and non-natives.

Characterisation of Hydro-Geochemical Processes Influencing Groundwater Quality in Rural Areas: A Case Study of Soutpansberg Region, Limpopo Province, South Africa

Groundwater is often the main or only source of fresh water supply in arid to semi-arid rural areas owing to decreasing rainfall patterns, reduced availability of surface water and socioeconomic activities. It is important to understand the hydro-geochemical processes influencing groundwater quality for improved management and sustainability of resources and to improve rural livelihoods. To understand the hydro-geochemical process influencing the hydro-geochemistry of the Soutpansberg region, this study assessed groundwater quality data from 12 boreholes and 2 geothermal springs collected between 1995 and 2017. This study indicated that the majority of the samples were classified as fresh groundwater dominated by Ca-HCO3 and mixed Ca-Mg-Cl types. Gibbs diagrams, Pearson correlations, bivariate plots and saturation indexes suggested that rock dominance processes, such as weathering of silicates, dissolution of carbonates and halite minerals and ion exchange processes, were the main hydro-geochemical processes influencing the groundwater quality in the Soutpansberg region. The high concentration of F− in the geothermal spring was attributed to the dissolution of fluorite mineral. Point source anthropogenic inputs from fertilisers were attributed to the high concentration of NO3− in the groundwater. This study recommends that research outputs should be used to influence and support policy change and groundwater allocation in arid to semi-arid rural environments for improved management of resources and livelihoods. This study further recommends that suitable deflouridation and denitrification techniques be applied to improve the quality of groundwater for drinking purposes.

Forecasting groundwater quality using automatic exponential smoothing model (AESM) in Xianyang City, China

To reasonably ensure good groundwater quality for the safety of users, it is necessary to monitor the evolution of physicochemical parameters of water. This study assessed the evolution of groundwater quality in Xianyang City (Central China) for 6 years and forecasted the water quality index (WQI) using the automatic exponential smoothing model (AESM). The results revealed that pH, Mn, NH4 +, HCO3 − and Ca2+ increased significantly within 6 years. However, there was a slight decrease in K+, NO3 −, SiO2, and Mg2+. Over the course of 6 years, seven out of fourteen wells maintained excellent or good water quality, whereas groundwater quality in the remaining wells fluctuated from excellent to good or from good to poor. The WQI index increased for nine wells, and five of them including well 173, well 457, well 46, well 26, and well C4 manifested an exponential increase of WQI, which was mainly caused by high concentrations of Mn, NH4 +, and NO3 −. The forecast accuracy verified by MASE and sMAPE, which ranged from 0.35 to 1.06 and from 0.04 to 0.69, respectively, demonstrated that the predictions were reliable. The AESM was tested in groundwater quality prediction, indicating that it might be used for actual scientific studies.

Long-term and seasonal nitrate trends illustrate potential prevention of large cyanobacterial biomass by sediment oxidation in Hamilton Harbour, Lake Ontario

Several studies have shown that large, experimental additions of nitrate (NO3) to eutrophic systems can mitigate large populations of nuisance cyanobacteria and that high NO3 concentrations can oxidize anoxic sediments. These studies are consistent with observations from numerous aquatic systems across a broad trophic range showing development of reduced surficial sediments precedes the formation of large cyanobacteria populations. We use 50+ years of data to explore whether high NO3 concentrations may have been instrumental both in the absence of large populations of cyanobacteria in eutrophic Hamilton Harbour, Lake Ontario in the 1970s when total phosphorus (TP) and total nitrogen (TN) concentrations were high, and in delaying large populations until August and September in recent decades despite much lower TP and TN. Our results indicate that large cyanobacteria population events do not occur at the central station in July-September when epilimnetic NO3 > 2.2 mg N L−1. The results further suggest that remedial improvements to wastewater treatment plant oxidation capacity may have been inadvertently responsible for high NO3 concentrations > 2.2 mg N L−1 and thus for mitigating large cyanobacteria populations. This also implies that large cyanobacteria populations may form earlier in the summer if NO3 concentrations are lowered.

Copper availability governs nitrous oxide accumulation in wetland soils and stream sediments

Denitrification is microbially-mediated through enzymes containing metal cofactors. Laboratory studies of pure cultures have highlighted that the availability of Cu, required for the multicopper enzyme nitrous oxide reductase, can limit N2O reduction. However, in natural aquatic systems, such as wetlands and hyporheic zones in stream beds, the role of Cu in controlling denitrification remains incompletely understood. In this study, we collected soils and sediments from three natural environments -- riparian wetlands, marsh wetlands, and a stream -- to investigate their nitrogen species transformation activity at background Cu levels and different supplemented Cu loadings. All of the systems contained solid-phase associated Cu below or around geological levels (40–280 nmol g−1) and exhibited low dissolved Cu (3–50 nM), which made them appropriate sites for evaluating the effect of limited Cu availability on denitrification. In laboratory incubation experiments, high concentrations of N2O accumulated in all microcosms lacking Cu amendment except for one stream sediment sample. With Cu added to provide dissolved concentrations at trace levels (10–300 nM), the reduction rate of N2O to N2 in the wetland soils and stream sediments was enhanced. A kinetic model could account for the trends in nitrogen species by combining the reactions for microbial reduction of NO3− to NO2−/N2O/N2 and abiotic reduction of NO2− to N2. The model revealed that the rate of N2O to N2 conversion increased significantly in the presence of Cu. For riparian wetland soils and stream sediments, the kinetic model also suggested that overall denitrification is driven by abiotic reduction of NO2− in the presence of inorganic electron donors. This study demonstrated that natural aquatic systems containing Cu at concentrations less than or equal to crustal abundances may display incomplete reduction of N2O to N2 that would cause N2O accumulation and release to the atmosphere.

Spatialization and Prediction of Seasonal NO2 Pollution Due to Climate Change in the Korean Capital Area through Land Use Regression Modeling.

Urbanization is causing an increase in air pollution leading to serious health issues. However, even though the necessity of its regulation is acknowledged, there are relatively few monitoring sites in the capital metropolitan city of the Republic of Korea. Furthermore, a significant relationship between air pollution and climate variables is expected, thus the prediction of air pollution under climate change should be carefully attended. This study aims to predict and spatialize present and future NO2 distribution by using existing monitoring sites to overcome deficiency in monitoring. Prediction was conducted through seasonal Land use regression modeling using variables correlated with NO2 concentration. Variables were selected through two correlation analyses and future pollution was predicted under HadGEM-AO RCP scenarios 4.5 and 8.5. Our results showed a relatively high NO2 concentration in winter in both present and future predictions, resulting from elevated use of fossil fuels in boilers, and also showed increments of NO2 pollution due to climate change. The results of this study could strengthen existing air pollution management strategies and mitigation measures for planning concerning future climate change, supporting proper management and control of air pollution.

Near-Infrared Light-Triggered Nitric Oxide Nanogenerators for NO-Photothermal Synergistic Cancer Therapy.

Cancer is still one of the major health issues faced by human beings today. Various nanomaterials have been designed to treat tumors and have made great progress. Herein, we used amino-functionalized metal organic framework (UiO-66-NH2) as superior templates and successfully synthesized the UiO-66-NH2@Aushell composite nanoparticles (UA) with high loading capacity and excellent photothermal properties through a simple and gentle method. In addition, due to the rich pore structure and excellent biocompatibility of the as-prepared composite nanoparticles, the hydrophobic NO donor BNN6 (N,N′-Di-sec-butyl-N,N′-dinitroso-1, 4-phenylenediamine) molecule was efficiently delivered. Based on the phenomenon where BNN6 molecules can decompose and release NO at high temperature, when UiO-66-NH2@Aushell-BNN6 composite nanoparticles (UA-BNN6) entered tumor cells and were irradiated by NIR, the porous gold nanoshells on the surface of composite nanoparticles induced an increase in temperature through the photothermal conversion process and promoted the decomposition of BNN6 molecules, releasing high concentration of NO, thus efficiently killing HeLa cells through the synergistic effect of NO-photothermal therapy. This effective, precise and safe treatment strategy controlled by NIR laser irradiation represents a promising alternative in the field of cancer treatment.