Highest NO2 Research Articles

Land-Use–Land Cover Changes in the Urban River’s Buffer Zone and Variability of Discharge, Water, and Sediment Quality—A Case of Urban Catchment of the Ngerengere River in Tanzania

The physical integrity of the Ngerengere River and its three tributaries drains within Morogoro Municipality were evaluated by assessing the variations in land-use–land cover (LULC) in the river’s buffer zone, the discharge, and the contamination of river water and sediment from nutrients and heavy metals. Integrated geospatial techniques were used to classify the LULC in the river’s buffer zone. In contrast, the velocity area method and monitoring data from the Wami-Ruvu Basin were used for the discharge measurements. Furthermore, atomic absorption spectrophotometry was used during the laboratory analysis to determine the level of nutrients and heavy metals in the water and river sediment across the 13 sampling locations. The LULC assessment in the river’s buffer during the sampling year of 2023 showed that bare land and built-up areas dominate the river’s buffer, with a coverage of 28% and 38% of the area distribution. The higher discharge across the sampling stations was in the upstream reaches at 3.73 m3/s and 2.36 m3/s at the confluences. The highest concentrations of heavy metals in the water for the dry and wet seasons were 0.09 ± 0.01, 0.25 ± 0.01, 0.03 ± 0.02, 0.73 ± 0.04, 4.07 ± 0.08, and 3.07 ± 0.04 mg/L, respectively, for Pb, Cr, Cd, Cu, Zn, and Ni. The order of magnitude of the heavy metal concentration in the sediments was Zn > Ni > Cr > Cu > Cd > Pb, while the highest NO2−, NO3−, NH3, and PO43− in the water and sediment were 2.05 ± 0.01, 0.394 ± 0.527 0.66 ± 0.05, and 0.63 ± 0.01 mg/L, and 2.64 ± 0.03, 0.63 ± 0.01, 2.36 ± 0.01, and 48.16 ± 0.01 mg/kg, respectively, across all sampling seasons. This study highlights the significant impact of urbanization on river integrity, revealing elevated levels of heavy metal contamination in both water and sediment, the variability of discharge, and alterations in the LULC in the rivers’ buffer. This study recommends the continuous monitoring of the river water quality and quantity of the urban rivers, and the overall land-use plans for conserving river ecosystems.

Long-term observations of NO2 using GEMS in China: Validations and regional transport

In 2019, South Korea launched the Geostationary Environment Monitoring Spectrometer (GEMS) to observe trace gases with an hourly temporal resolution. Compared to previous payloads on polar-orbiting satellites, the GEMS payload has significant advantages in detecting the diurnal variation characteristics of NO2. However, there is still a lack of ground-based validations regarding the overall accuracy of GEMS in the Chinese region. In this study, we conducted a systematic ground validation of GEMS NO2 data in China for the first time. We validated the accuracy of GEMS NO2 data in four typical pollution regions in China, namely the Beijing-Tianjin-Hebei region (JJJ), the Yangtze River Delta region (YRD), the Pearl River Delta region (PRD), and the Sichuan Basin region (SCB), based on MAX-DOAS and CNEMC data. The averaged correlations using the two datasets for validation were 0.81 and 0.57, respectively, indicating a high level of accuracy for the data in China. Using the GEMS seasonal averaged NO2 data, we studied the distribution of NO2 levels in the four regions. We found that the highest NO2 in all four regions occurred during winter with concentrations of 1.84 × 1016 molecules cm−2, 1.59 × 1016 molecules cm−2, 1.58 × 1016 molecules cm−2 and 9.47 × 1015 molecules cm−2, respectively. The distribution of NO2 was closely related to the terrain. Additionally, we observed a significant underestimation issue with TROPOMI, exceeding 30 % in many regions. Based on MAX-DOAS, we investigated the vertical distribution of NO2 in the four regions and found that NO2 was mainly concentrated below 0.5 km. with the HNU station having the lowest concentration, averaging only 2.12 ppb, which was approximately 41 % of the highest concentration recorded at the CQ station. Furthermore, we conducted a study on regional and cross-regional transport using a combination of MAX-DOAS and GEMS data. We found that the transport flux of NO2 could increase by over 500 % within 1 h, making a significant contribution to local NO2 concentrations. The joint observations of GEMS and MAX-DOAS will provide reliable data support for NO2 research and control in China, making a substantial contribution to environmental protection and sustainable development.

Impact of exposure to urban air pollution on grey squirrel (Sciurus carolinensis) lung health

The increased rate of global urbanisation has recently exacerbated the significant public health problem of traffic related air pollution. Despite the known significant impact on human health, little is known about the effects of air pollution on wildlife health. The lung is the primary target organ for the effects of exposure to air pollution, leading to lung inflammation, altering the lung epigenome, culminating in respiratory disease. In this study, we aimed to assess lung health and DNA methylation profiles in Eastern grey squirrel (Sciurus carolinensis) populations living across an urban-rural air pollution gradient. Squirrel lung health was assessed in four populations situated across the most polluted inner-city boroughs to the less polluted edges of Greater London. We also assessed lung DNA methylation across three London sites and a further two rural sites in Sussex and North Wales. Lung and tracheal diseases were present in 28% and 13% of the squirrels respectively. Specifically, focal inflammation (13%), focal macrophages with vacuolated cytoplasm (3%) and endogenous lipid pneumonia (3%). There was no significant difference in prevalence of lung, tracheal diseases, anthracosis (carbon presence) or lung DNA methylation levels between urban sites and urban and rural sites respectively or NO2 levels. BALT (Bronchus-Associated Lymphoid Tissue) was significantly smaller in the site with highest NO2 and contained the highest carbon loading compared to sites with lower NO2, however differences in carbon loading in between sites were not significant. High pollution site individuals also had significantly higher numbers of alveolar macrophages which suggests that grey squirrels are exposed to and respond to traffic-related air pollution and further research is needed to understand the impact of traffic-related air pollutants on wildlife health.

Indoor and Outdoor Air Quality Assessment of So2 and No2 in Suburban Schools in Imphal, Manipur

Air quality assessments for NO2 and SO2 levels in indoor and outdoor environments were conducted in three suburban schools in Imphal. Season-wise, the highest NO2 and SO2 concentrations were observed during winter, while the lowest occurred during the monsoon. The concentration of SO2 in the indoor air was comparatively cleaner than in the outdoor air. Similarly, indoor air was found to be cleaner than outdoor air with respect to NO2. The overall concentration obtained for the entire study period for SO2 was 4.9±1.5 µg m-3, and for NO2, it was 9.2±3.0 µg m-3. The concentrations of the two gases obtained during the study were below the NAAQs and WHO permissible limits. Seasonal variation of SO2 concentrations between the pre-monsoon period and monsoon months and also between the monsoon period and winter months (at p<0.001) was significant. For NO2, seasonal variation in the concentrations between the monsoon and winter (at p<0.001) was found significant. The estimated I/O ratios for the two studied gases, which were below one, plus the positive correlation between the classroom and campus environment concentrations of NO2 (r=0.96), and SO2 (r=0.96), reflected the influence of the indoor air quality by outdoor pollution sources. Data on similar studies for the country’s northeastern region, in particular, is scanty, and that’s why it may provide valuable insights to the scientific world.

Multi-methods to investigate spatiotemporal variations of nitrogen-nitrate and its risks to human health in China's largest fresh water lake (Poyang Lake)

Nitrogen-nitrate contamination has been recognized as the main threaten to the large lake surrounding with the intensive agriculture activities. However, there are still insufficient studies on the interannual evolution of nitrogen-nitrate, source and its impact on the environment and human health in the large fresh water lake. In this study, 248 samplings were collected in Poyang Lake from 2013 to 2018, multi-methods (mathematical statistics method, grey correlation analysis, person correlation analysis and human health risk assessment) to investigate the spatiotemporal variations, impact factors and potential health risks of NO2−-N, NO3−-N and NH4+-N. The results showed that the middle region had the highest NO2− concentration (mean 0.04μg/l), the northern region had the highest NO3− concentration (mean 1.12 mg/l), and the southern region had the highest NH4+ concentration (mean 0.48 mg/l). For NO3− and NH4+, the concentration was higher than in the wet season. While the concentration of NO2− had the reverse trend. Grey correlation analysis and person correlation analysis results indicate that nitrogen fertilizer, waste water, pH, CODMn and temperature were main factors affecting the nitrogen concentration in Poyang Lake. Health risk assessment results revealed that potential hazards in the study area were acceptable (HR < 1). NO3− provided the highest health risks, and oral ingestion is the major source of local nitrogen health risk. Those results can provide the reference for developing the treatment methods of the international large freshwater lake.

Effects of salinity on nitrite and elemental sulfur accumulation in a double short-cut sulfur autotrophic denitrification process

Double short-cut sulfur autotrophic denitrification (DSSADN) coupled with Anammox is of great significance in the low-carbon treatment of nitrogen-containing wastewater. In order to achieve high salinity autotrophic nitrogen removal, the effects of different salinities on the accumulation characteristics of NO2−-N and S0 and microorganisms in DSSADN process were studied. The results showed that the effect of salinity on the DSSADN process could be categorized into the stimulation, stable, and inhibition. When the salinity gradually increased to 2.5 %, the highest NO2−-N production rate (NiPR) and S0 production rate (S0PR) of DSSADN were 0.54 kg/(m3·d) and 1.1 kg/(m3·d) respectively. NiPR and S0PR gradually decreased as the salinity increased to more than 3 %. However, salinity had a relatively low impact on nitrite accumulation efficiency and S0 accumulation efficiency, which were 80 % and 81.5 %, respectively, when the salinity reached 5 %. Salinity has a great influence on the structure and abundance of microbial communities in the system.

Spatiotemporal variability of nitrogen dioxide (NO2) pollution in Manchester (UK) city centre (2017–2018) using a fine spatial scale single-NOx diffusion tube network

Nitrogen dioxide (NO2) is linked to poor air quality and severe human health impacts, including respiratory and cardiovascular diseases and being responsible annually for approximately 23,500 premature deaths in the UK. Automated air quality monitoring stations continuously record pollutants in urban environments but are restricted in number (need for electricity, maintenance and trained operators), only record air quality proximal to their location and cannot document variability of airborne pollutants at finer spatial scales. As an alternative, passive sampling devices such as Palmes-type diffusion tubes can be used to assess the spatial variability of air quality in greater detail, due to their simplicity (e.g. small, light material, no electricity required) and suitability for long-term studies (e.g. deployable in large numbers, useful for screening studies). Accordingly, a one passive diffusion tube sampling approach has been adapted to investigate spatial and temporal variability of NO2 concentrations across the City of Manchester (UK). Spatial and temporal detail was obtained by sampling 45 locations over a 12-month period (361 days, to include seasonal variability), resulting in 1080 individual NO2 measurements. Elevated NO2 concentrations, exceeding the EU/UK limit value of 40 µg m−3, were recorded throughout the study period (N = 278; 26% of individual measurements), particularly during colder months and across a wide area including residential locations. Of 45 sampling locations, 24% (N = 11) showed annual average NO2 above the EU/UK limit value, whereas 16% (N = 7) showed elevated NO2 (> 40 µg m−3) for at least 6 months of deployment. Highest NO2 was recorded in proximity of highly trafficked major roads, with urban factors such as surrounding building heights also influencing NO2 dispersion and distribution. This study demonstrates the importance of high spatial coverage to monitor atmospheric NO2 concentrations across urban environments, to aid identification of areas of human health concern, especially in areas that are not covered by automated monitoring stations. This simple, reasonably cheap, quick and easy method, using a single-NOx diffusion tube approach, can aid identification of NO2 hotspots and provides fine spatial detail of deteriorated air quality. Such an approach can be easily transferred to comparable urban environments to provide an initial screening tool for air quality and air pollution, particularly where local automated air quality monitoring stations are limited. Additionally, such an approach can support air quality assessment studies, e.g. lichen or moss biomonitoring studies.

Short-Term Associations between Morbidity and Air Pollution in Metropolitan Area of Monterrey, Mexico

Short-term effects of air pollution on the number of hospital admissions in eight municipalities of the Metropolitan Area of Monterrey, Mexico, were assessed from 2016 to 2019 using a time-series approach. Air quality data were obtained from the Atmospheric Monitoring System of Nuevo Leon State (SIMA) which belongs to SINAICA (National System of Air Quality Information), providing validated data for this study. Epidemiological data were provided by SINAIS (National System of Health Information), considering admission by all causes and specific causes, gender and different age groups. Guadalupe had the highest mean concentrations for SO2, CO and O3; whereas Santa Catarina showed the highest NO2 concentrations. Escobedo and Garcia registered the highest levels for PM10. Only PM10 and O3 exceeded the permissible maximum values established in Mexican official standards. A basal Poisson model was constructed to assess the association between daily morbidity and air pollutants, from this, a second scenario in which daily mean concentrations of air pollutant criteria increase by 10% was considered. Most of pollutants and municipalities studied showed a great number of associations between an increase of 10% in their current concentrations and morbidity, especially for the age group between 5 and 59 years during cold months, excepting ozone which showed a strongest correlation during summer. Results were comparable to those reported by other authors around the world, however, in spite of relative risk index (RRI) values being low, they are of public concern. This study demonstrated that considering the nature of their activities, economically active population and students, they could be more vulnerable to air pollution effects. Results found in this study can be used by decision makers to develop public policies focused on protecting this specific group of the population in metropolitan areas in Mexico.

Isolation and selection of nitrite metabolising bacteria from the bottom mud of lobster culture area in Xuan Dai bay, Phu Yen province

The study had isolated and selected groups of bacteria that metabolise nitrite from the bottom mud of lobster cages in Xuan Dai bay, Phu Yen province. Analysis results from 21 sludge samples taken from 11 cages of lobster farming area isolated 16 strains of bacteria capable of nitrite metabolism. After investigating biological characteristics and nitrite metabolism of bacteria strains, 10 strains of bacteria were collected with the ability to metabolise nitrite over 95% in 72 hours. In addition, 10 strains of bacteria with the highest NO2- treatment efficiency, identified by genetic analysis and looked up on BLAST, defined as Stenotrophomonas pavanii, Chryseobacterium gleum, Stenotrophomonas maltophilia, Delftia lacustris, Acinetobacter junii

"Freedom to Breathe": Youth Participatory Action Research (YPAR) to Investigate Air Pollution Inequities in Richmond, CA.

Air pollution is a major contributor to human morbidity and mortality, potentially exacerbated by COVID-19, and a threat to planetary health. Participatory research, with a structural violence framework, illuminates exposure inequities and refines mitigation strategies. Home to profitable oil and shipping industries, several census tracts in Richmond, CA are among the most heavily impacted by aggregate burdens statewide. Formally trained researchers from the Center for Environmental Research and Children’s Health (CERCH) partnered with the RYSE youth justice center to conduct youth participatory action research on air quality justice. Staff engaged five youth researchers in: (1) collaborative research using a network of passive air monitors to quantify neighborhood disparities in nitrogen dioxide (NO2) and sulfur dioxide (SO2), noise pollution and community risk factors; (2) training in environmental health literacy and professional development; and (3) interpretation of findings, community outreach and advocacy. Inequities in ambient NO2, but not SO2, were observed. Census tracts with higher Black populations had the highest NO2. Proximity to railroads and major roadways were associated with higher NO2. Greenspace was associated with lower NO2, suggesting investment may be conducive to improved air quality, among many additional benefits. Youth improved in measures of empowerment, and advanced community education via workshops, Photovoice, video, and ”zines”.

NO2 catalytic removal by nickel catalyst supported on multi-walled carbon nanotubes

ABSTRACT In this study, nickel-based catalyst supported on multi-walled carbon nanotube (Ni/MWCNT) was synthesized and used in NO2 removal from polluted air. Scanning Electron Microscopy (SEM) and Energy Distribution Spectrum (EDS), X-Ray Diffraction (XRD) and H2-Temperature-Programmed Reduction (H2-TPR) were used to determine the characteristics of the synthesized Ni/MWCNT catalysts and multi-walled carbon Nanotube. To Optimize the catalytic process, the effects of space velocities (15,000–25,000 hr−1), NO2 concentrations (3000–5000 ppm) and temperatures (150–450°C) were investigated on the NO2 removal efficiency. The highest NO2 removal efficiency was 96% by using 20% Wt of nickel-based supported on the MWCNT (20% Ni/MWCNTs) at temperature of 450°C, NO2 concentration of 3000 ppm and space velocity of 15,000 hr−1. Our findings indicated that increasing space velocity from 15,000 to 25,000 hr−1 did not have a strict effect on removal efficiency. Increasing temperature from 150 to 450°C led to increase in removal efficiency of about 20%.

Study on spatiotemporal distribution of the tropospheric NO2 column concentration in China and its relationship to energy consumption based on the time-series data from 2005 to 2013

ABSTRACT The spatial and temporal distribution of the tropospheric NO2 column concentration in China and its relationship with energy consumption were analyzed based on spatial analysis and Grey Relation using the remote sensed data from 2005 to 2013. The results show that the spatial distribution of NO2 in China shows close relationships with population distribution and terrain properties. NO2 distribution is divided into the eastern and the western part by HU Line, a geographical division line of the population of China. The NO2 concentration is on the rise in most provincial-level regions, but has remained stable in a few provincial-level regions over a long period. In general, China’s NO2 concentration reached its peak approximately in 2011. During the years from 2005 to 2010, China’s NO2 concentration grew rapidly and reached its peak in 2011, following with a steady growth or a slight decline during the years 2011 to 2013. There shows a U-shaped variation in monthly NO2 concentration, with the highest NO2 concentration in winter and spring, lower one in the summer, and a distinct increase in autumn, which demonstrates a seasonal variation of NO2 concentration. At a national-scale, the NO2 concentration distribution shows a strong positive correlation with the total coal and oil consumption per unit area, implying that the total coal and oil consumption contributes significantly to the NO2 concentration and should be controlled to reduce the NO2 concentration. In regions with a high NO2 concentration, the provincial-scale NO2 concentration is affected by the types of energy consumed, or to be more specific, is affected by the total coal consumption in northern China versus the total oil consumption in southern China, and by the total oil consumption in eastern China versus the total coal consumption in western China.

Assessment of nitrate and nitrite levels in treated wastewater, soil, and vegetable crops at the upper reach of Zarqa River in Jordan.

The purpose of this study is to examine the impact of treated wastewater irrigation on agricultural soils and vegetables along the upper reach of Zarqa River (Jordan). Multiple samples of reclaimed wastewater, soil pits from farms, and vegetables (spinach, parsley, cabbage cauliflower, radish, and onion) were collected and analyzed for pH, total dissolved solids (TDS), and/or NO3- and NO2- contents. The average levels of NO3- and NO2- in treated wastewater samples varied from 167.2 to 209.9mg/l for NO3- and from 80.3 to 106.1μg/l for NO2-. Values of TDS and pH exhibited relatively comparable spatial patterns, with higher values in the downstream channel and lower in the upper reach, adjacent to Al-Samra Wastewater Treatment Plant. The average values of NO3- and NO2- showed broadly decreasing trends down-gradient towards King Talal Dam. In soil pits, a marginal increase of pH values with depth was noted, whereas TDS showed a remarkable decrease in soil profile by ~ 2 to 3 folds. Concurrently, the levels of NO3- and NO2- in all soil pits markedly decreased from top to bottom. In vegetables irrigated with treated wastewater, substantially elevated levels of NO3- were observed, compared with those irrigated with rainwater, with leafy vegetables demonstrating higher levels than the root crops. Spinach exhibited higher capacity for NO3- accumulation (4614.1mg/kg), while onion showed the lowest content (1722mg/kg). The highest NO2- level was observed in parsley (1.19mg/kg), and the lowest concentrations were found in cauliflower (0.25mg/kg). The markedly high accumulation of NO3- in vegetables is an indicator of pollution activities around Zarqa River and poses potential health risks to humans when they are consumed.

Preparation of (La0.8Sr0.2)2FeNiO6-Δ Nanopowder by Pechini Method and Its Sensitivity to NO2

The nano-sized (La0.8Sr0.2)2FeNiO6-Δ (LSFN) double perovskite powder without impurity phase was successfully prepared using the Pechini method. The result demonstrated that the electrode sensing properties to NO2 were affected by the sintering temperature. The sensor with 1300°C-sintered LSFN sensing electrode exhibited the highest NO2 sensitivity.

Satellite-sensed tropospheric NO2 patterns and anomalies over Indus, Ganges, Brahmaputra, and Meghna river basins

ABSTRACTThis study presents trends, seasonality, hot spots, and anomalies of tropospheric NO2 pollution over four basins of Indus, Ganges, Brahmaputra, and Meghna rivers in South Asia using observations from Ozone Monitoring Instrument (OMI) on-board Aura satellite during 2004–2015. For the first time this area, a highly populated and industrialized region with significant emissions of air pollutants, has been discussed collectively. OMI data reveal significantly elevated NO2 column over the region averaged at (1.9 ± 0.1) × 1015 molecules cm–2 (average ± standard deviation of observations) with an increase of 21.12% (slope (0.036 ± 0.004) × 1015 molecules cm–2, y-intercept (1.705 ± 0.024) × 1015 molecules cm–2, R2 = 0.92) during the study period. According to MACCity anthropogenic emissions inventory transportation, energy, residential, and industrial sectors are the major contributors of high NOx emissions. NO2 pollution hot spots are identified and their tendencies have been discussed. The hot spots of megacities Lahore (Pakistan) and Dhaka (Bangladesh) are found to be strengthening and expanding over the time. Eastern Ganges Basin shows the highest NO2 concentration at (2.63 ± 0.22) × 1015 molecules cm–2 and growth rate of 3.22% per year mainly linked to power generation, fossil fuel extraction, mining activities, and biomass burning. NO2 over Indus–Ganges–Brahmaputra–Meghna Basin exhibits seasonal maximum in winter and minimum in monsoon. The highest seasonality is found over Meghna Basin due to large variations in meteorological conditions and large-scale crop-residue burning. Some anomalies in NO2 levels have been detected linked to intense crop-residue burning events. During these anomalies, exceptionally high levels of daily NO2 reaching up to 76.23 × 1015 molecules cm–2 have been observed over some places in Indus and Meghna Basins.

Diagnostic Accuracy of Brain-derived Neurotrophic Factor and Nitric Oxide in Patients with Schizophrenia: A pilot study.

SummaryBackgroundBrain-derived neurotrophic factor (BDNF) and nitric oxide (NO) play multiple roles in the developing and adult CNS. Since BDNF and NO metabolisms are dysregulated in schizophrenia, we measured these markers simultaneously in the blood of schizophrenics and assessed their diagnostic accuracy.MethodsThirty-eight patients with schizophrenia classified according to demographic characteristics, symptomatologyand therapy and 39 age- and gender-matched healthy controls were enrolled. BDNF was determined by the ELISA technique while the concentration of nitrite/nitrate () was measured by the colorimetric method.ResultsSerum BDNF levels were significantly lower (20.38±3.73 ng/mL, P = 1.339E-05), whilst plasma concentrations were significantly higher (84.3 (72–121) μmol/L, P=4.357E-08) in patients with schizophrenia than in healthy controls (25.65±4.32 ng/mL; 60.9 (50–76) μmol/L, respectively). The lowest value of BDNF (18.14±3.26 ng/mL) and the highest concentration (115.3 (80–138) μmol/L) were found in patients treated with second-generation antipsychotics (SGA). The patients diseased before the age of 24 and the patients suffering for up to one year had significantly lower serum BDNF levels than those diseased after the age of 24 and the patients who were ill longer than one year. Both BDNF and showed good diagnostic accuracy, but BDNF had better ROC curve characteristics, especially in patients with negative symptomatology.ConclusionsBDNF and nitrite/nitrate showed inverse changes in schizophrenic patients. The most pronounced changes were found in patients treated with second-generation antipsychotics. Although BDNF is not specific of schizophrenia, it may be a clinically useful biomarker for the diagnosis of patients expressing predominantly negative symptoms.

Sources of new nitrogen in the Indian Ocean

AbstractQuantifying the different sources of nitrogen (N) within the N cycle is crucial to gain insights in oceanic phytoplankton production. To understand the controls of primary productivity and the associated capture of CO2 through photosynthesis in the southeastern Indian Ocean, we compiled the physical and biogeochemical data from four voyages conducted in 2010, 2011, 2012, and 2013. Overall, higher NH4+ assimilation rates (~530 µmol m−2 h−1) relative to NO3− assimilation rates (~375 µmol m−2 h−1) suggest that the assimilation dynamics of C are primarily regulated by microbial regeneration in our region. N2 fixation rates did not decline when other source of dissolved inorganic nitrogen were available, although the assimilation of N2 is a highly energetic process. Our data showed that the diazotrophic community assimilated ~2 nmol N L−1 h−1 at relative elevated NH4+ assimilation rates ~12 nmol L−1 h−1 and NO3− assimilation rates ~6 nmol L−1 h−1. The small diffusive deep water NO3− fluxes could not support the measured NO3− assimilation rates and consequently point toward another source of dissolved inorganic NO3−. Highest NO2− values coincided consistently with shallow lower dissolved O2 layers (100–200 m; 100–180 µmol L−1). These results suggest that nitrification above the pycnocline could be a significant component of the N cycle in the eastern Indian Ocean. In our analysis we provide a conceptual understanding of how NO3− in the photic zone could be derived from new N through N2 fixation. We conclude with the hypothesis that N injected through N2 fixation can be recycled within the photic zone as NH4+ and sequentially oxidized to NO2− and NO3− in shallow lower dissolved oxygen layers.

Concentrations of NO2 and NOX across the Perth metropolitan area, Western Australia

Background Numerous studies have shown that high levels of air pollution are associated with adverse health effects, particularly in the elderly. The Health in Men Air Quality Study is investigating the health effects of long term exposure to air pollution in a cohort of 12,000 older men residing in Perth, Western Australia. This study is being undertaken in affiliation with the The European Study of Cohorts for Air Pollution program. Aims To describe NO2 and NOx concentrations from 43 sites across Perth by season and site type. Methods Ogawa passive diffusion badges were used to collect nitrogen oxide samples. Sites were selected to represent spatial variation of air pollution at the cohort home addresses across 3 categories: regional (n=2) and urban background (n=19) and street sites (n=22). Fourteen day samples were taken during 3 seasons in 2012.The annual average, median and range were determined, stratified by site type. Data were transformed using the square root and ANOVA was used to test for significant differences in means between site types. Results The median concentrations for NO2 and NOx for all sites and seasons were: 12.58µg/m3 (range 2.27–24.87, SD 5.69) and 21.31µg/m3 (range 3.59–59.76, SD 12.43). The highest NO2 and NOx median concentrations were found at street locations: 14.62 µg/m3 (range 5.90–24.87, SD 5.40) and 31.13µg/m3 (range 11.95–59.76, SD 11.74), followed by urban sites: 11.13µg/m3 (range 3.17–19.83, SD 4.32) and 17.64µg/m3 (range 4.79-36.36, SD 7.33) with the lowest concentrations found at regional sites: 2.98µg/m3 (range 2.27-3.70, SD 1.01) and 4.45µg/m3 (range 3.59-5.32, SD 1.22). Mean concentrations for NO2 and NOx were significantly different between each of the site types. Conclusions The NO2 and NOx median concentrations were low and below the Australian National Environmental Protection Measure standard for NO2. Concentrations were consistent with the lower concentrations reported by ESCAPE and showed similar trends by site type.

Trends in Passively-Measured Ozone, Nitrogen Dioxide and Sulfur Dioxide Concentrations in the Athabasca Oil Sands Region of Alberta, Canada

The Athabasca Oil Sands Region (AOSR) in northeastern Alberta, Canada has attracted much international attention in recent years due to the increased level of oil sands operations. A passive sampling program was initiated in 1999 to monitor ozone (O3), nitrogen dioxide (NO2) and sulfur dioxide (SO2) in the AOSR for the estimation of the exposure of the forest monitoring sites and the characterization of temporal trends. Since 1999, highest concentrations of O3 and NO2 occurred in April and winter, respectively. The observed spring O3 maximum is common in the northern hemisphere. The higher winter-time NO2 concentrations were due to low atmospheric mixing height, stable atmosphere, and higher emissions during winter. Sen-Theil trend analysis, a non-parametric analysis for temporal trending, determined that O3 concentrations from 2000 to 2009 did not change. NO2 concentrations increased slightly at three sites, and significantly increased at two sites closer to stationary and mobile sources. SO2 concentration was increasing at JP107 and was decreasing at JP101. SO2 concentrations did not increase at 4 other sites close to the major emissions. This suggests that SO2 emissions were likely stable. Spatial analysis was conducted to characterize the concentration distribution in the region. The O3 concentrations were low near the emission sources (9.4 km) likely due to local O3 titration. Highest NO2 and SO2 concentrations were measured near the main source area. Generally, passively measured monthly average concentrations of O3, NO2 and SO2 stabilized at 20, 48 and 48 km from the main source area suggesting NO2 and SO2 emission influences were limited to < 50 km away from the major sources. However, one site (JP107) located near the Athabasca River Valley, 94 km north of the main source area, had higher SO2 and NO2 concentrations. This could be attributed to influence of valley flow, and/or to additional sources added in the region since 2007.

Influence of salinity on partial nitrification in a submerged biofilter

Partial nitrification under various concentrations of NaCl (0–40g/l) at a constant operational condition was investigated in a submerged biofilter reactor. The highest NO2–N/NOx–N ratio (0.76) was achieved at the NLR of 830g NH4–N/m3 day with salt free wastewater. Small increase the salt content led to higher activities and the NH4–N removal efficiency increased from 92% to 95% at 1g/l NaCl concentration. Over this concentration, each NaCl addition provoked the NH4–N oxidation and a sharp increase of inhibition was observed. The total oxidized NH4–N was achieved at the nitrogen loading rate (NLR) and surface loading rate (SLR) of 0.754kg/m3day and 3.23g/m2day, respectively without salt in the feed wastewater and it was decreased to 0.322kg/m3 day and 1.38g/m2day at the salinity of 40g/l in the PNBR.