Concentrations Of Inorganic Ions Research Articles

Particles liquid water and acidity determine formation of secondary inorganic ions in Urumqi, NW China

Secondary atmospheric pollutants are an important component of the particles found in Urumqi city, China, Further, secondary inorganic aerosols, in particular, increase significantly during the winter heating period. In this study, samples collected from October 2017 to August 2018 from Urumqi were analyzed. Results showed that the average concentration of water-soluble inorganic ions (WSIs) in the heating period (86.9 ± 31.1 μg·m−3) was significantly higher than that in the non-heating period (14.1 ± 8.67 μg·m−3). SNA (SO42−, NO3−, NH4+) accounted for 90.7% of the total WSIs (TWSIs) in the heating period. Simulations revealed that the in situ pH (3.1) was higher in the heating period than that in non-heating period (0.66) when they were calculated by the aerosol thermodynamic model. The particles were found to be acidity during the entire period. The liquid water content of the particulates (LWC) was found to higher in the heating period (55.5 ± 51.8 μg·m−3) than the non-heating period (21.3 ± 40.3 μg·m−3). The average nitrogen oxidation rate (NOR) and sulfur oxidation rate (SOR) were 0.16 and 0.36, respectively, indicating a significant secondary formation of nitrate and sulfate in the atmosphere of Urumqi. Further analysis indicated that sulfate was significantly affected by the LWC and acidity of the particulates; nitrate was produced under ammonia-rich conditions in Urumqi, and the LWC facilitated the production of nitrate. This study provides information about the formation of secondary sulfate and nitrate aerosols during different periods in suburban Urumqi.

Sunlight-active Cu/Fe@ZnWO4-kaolinite composites for degradation of acetaminophen, ampicillin and sulfamethoxazole in water

This study reports the development of biomass-assisted sunlight-active semiconductor-tungstate-clay photocatalytic composite for the removal of pharmaceutical contaminants (PCs): Acetaminophen (ACT), Ampicillin (AMP) and Sulfamethoxazole (SMX), from water. Materials prepared (Cu@ZnWO4–K, Fe@ZnWO4–K and Cu/Fe@ZnWO4–K) composites, were characterized using Scanning Electron Microscopy (SEM), Fourier Transformed Infrared spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy, High Resolution TEM and X-ray Diffraction (XRD). XRD analysis showed the presence of Scheelite (CuWO4), Ferberite (FeWO4) and Sanmartinite (ZnWO4) crystal phases in the composites. Moreover, results showed that Cu@ZnWO4–K composite gave the best efficiency for the photodegradation of AMP (100%), ACT (83%), and SMX (68%) molecules. This composite showed more preference for the photodegradation of AMP molecules (>98%) even in the presence of ACT and SMX molecules. After five reuse cycles, the composite still had ca. 90% efficiency for AMP molecules but far less for the other two molecules. The presence of anions reduced the photocatalytic efficiency of this composite but increased the photodegradation of SMX molecules. The rate of photodegradation of the PCs was comparably fast, leading to high removal capacity. The concentrations of inorganic ions released as by-products of photodegradation, were far below WHO standard limits for their presence in drinking water.

Chemical and Optical Characteristics and Sources of PM2.5 Humic-Like Substances at Industrial and Suburban Sites in Changzhou, China

The chemical and optical properties and sources of atmospheric PM2.5 humic-like substances (HULIS) were investigated from October to December 2016 in both industrial and suburban areas in Changzhou, China, during polluted and fair days. The average PM2.5 concentration in the industrial region was 113.06 (±64.3) μg m−3, higher than 85.27 (±41.56) μg m−3 at the suburban site. The frequency of polluted days was significantly higher in the industrial region. In contrast, the chemical compositions of PM2.5 at the two sampling sites exhibited no statistically significant differences. Rapidly increased secondary inorganic ions (SNA = NH4+ + SO42− + NO3−) concentrations suggested secondary formation played an important role in haze formation. The daily mean concentration of humic-like substance (HULIS) was 1.8–1.9 times that of HULIS-C (the carbon content of HULIS). Our results showed that HULIS accounted for a considerable fraction of PM2.5 (industrial region: 6.3% vs. suburban region: 9.4%). There were no large differences in the mass ratios of HULIS-C/WSOC at the two sites (46% in the industrial region and 52% in the suburban region). On average, suburban HULIS-C constituted 35.1% of organic carbon (OC), higher than that (21.1%) in the industrial region. Based on different MAE (mass absorption efficiency) values under different pollution levels, we can infer that the optical properties of HULIS varied with PM levels. Moreover, our results showed no distinct difference in E2/E3 (the ratio of light absorbance at 250 nm to that at 365 nm) and AAE300–400 (Absorption Angstrom Exponent at 300–400 nm) for HULIS and WSOC. the MAE365 (MAE at 365 nm) value of HULIS-C was different under three PM2.5 levels (low: PM2.5 < 75 μg m−3, moderate: PM2.5 = 75–150 μg m−3, high: PM2.5 > 150 μg m−3), with the highest MAE365 value on polluted days in the industrial region. Strong correlations between HULIS-C and SNA revealed that HULIS might be contributed from secondary formation at both sites. In addition, good correlations between HULIS-C with K+ in the industrial region implied the importance of biomass burning to PM2.5-bound HULIS. Three common sources of HULIS-C (i.e., vehicle emissions, biomass burning, and secondary aerosols) were identified by positive matrix factorization (PMF) for both sites, but the contributions were different, with the largest contribution from biomass burning in the industrial region and secondary sources in the suburban region, respectively. The findings presented here are important in understanding PM2.5 HULIS chemistry and are valuable for future air pollution control measures.

A long-term chemical characteristics and source apportionment of atmospheric rainfall in a northwest megacity of Xi'an, China.

A long-term measurement on rainfall was conducted in urban Xi'an, China, from 2009 to 2016. The seasonal and annual variations of major inorganic components and their chemical properties in the rainfall were studied. The annual rainfall ranged from 165.3 to 916.3 mm. The pH value of the rainfall ranged from 6.36 to 7.19, with an average value of 6.70. The electric conductivity (EC) in the rainfall was in a range of 55.91 to 227.44 μS·cm-1. Ammonium (NH4+), calcium (Ca2+), nitrate (NO3-), and sulfate (SO42-) were the four major components, accounting for 88.5% of the total quantified inorganic ion concentration. Neutralization factors were determined for Ca2+ (1.03), NH4+ (0.57), Mg2+ (0.10), Na+ (0.06), and K+ (0.04). The high abundance of NH4+ that formed from its precursor of ammonia gas (NH3) suggested the contribution of agricultural fertilization. Ca2+ in the rainfall was mainly from natural sources such as soil dust, while anions of NO3- and SO42- originated from fossil fuel combustion. Source apportionment was conducted with positive matrix factorization (PMF) which identified that secondary inorganic formation, crustal dust, coal combustion, and biomass burning are the contributors to the rainfall. In between, secondary inorganic formation was the largest contributor, which accounted for 27.8-58.1% of the total sources, followed by crustal dust of 0.4-42.6%. The results of this long-term study demonstrated the decreasing trends of contributions from coal combustion and biomass burning under a series of air pollution control measures implemented by the government. However, continuous urbanization and development of the city caused substantial increases of the construction activities, inducing more crustal dusts to the environment in urban Xi'an.

Evaluation of black carbon source apportionment based on one year's daily observations in Beijing

Combustion-derived black carbon (BC) is increasingly recognized as a significant pollutant that can have adverse effects on the atmospheric environment, human health, and regional climate. Fossil fuel combustion is the main source of BC, yet understanding of the relative contributions to BC from coal and liquid fuel combustion remains incomplete. Moreover, few studies have assessed the relative contributions based on long-term continuous daily field observations. This study adopted a Bayesian model of a three-dimensional array of a stable carbon isotope and the ratios of non-sea-salt K+ to BC and ΔBC/ΔCO of one year's daily observations (from September 1, 2017 to August 31, 2018) to constrain source apportionment of BC in Beijing (China). Results showed that both the BC and the carbon isotope concentrations exhibited strong seasonal variability, and that the annual BC concentration has decreased significantly in recent years. The Bayesian model results also revealed that the relative contributions from the combustion of coal, liquid fuel, and biomass were 42% ± 18%, 42% ± 18%, and 16% ± 11%, respectively, with a larger contribution from coal (liquid fuel) combustion in winter and spring (summer and autumn). The seasonal variation of source appointment was attributed to local and regional fuel combustion coupled with meteorological conditions. With increasing PM2.5 level, the BC concentration derived from biomass burning increased fastest, followed by that derived from coal combustion. But concentration of secondary inorganic ions increased faster than BC as PM2.5 increased.

Can arbuscular mycorrhizal fungi and biochar enhance plant resistance to low‐temperature stress?

AbstractImproving plant resistance to abiotic stress, such as low temperature, is conducive to plant normal growth and development. The aim of this study was to clarify whether arbuscular mycorrhizal fungi (AMF) and biochar have a synergistic effect on plant growth and resistance to low‐temperature stress in perennial ryegrass (Lolium perenne L.). A pot experiment was conducted to measure the effects of AMF (Glomus intraradices) inoculation, biochar addition (4%, w/w), and their combination on the biomass, inorganic ion contents, antioxidant enzyme activities, and osmotic regulator contents in L. perenne plants growing under room temperature and low temperature conditions. A saline soil with the total salt content of 5.21 g kg–1 was used in the experiment. Results showed that the AMF‐only treatment decreased biomass growth under room temperature condition, whereas the biochar‐only treatment increased total biomass under low temperature condition. The combined treatment with AMF and biochar evidently increased biomass growth via a synergistic effect under both room temperature and low temperature conditions. Under low‐temperature stress, the AMF‐ and biochar‐only treatments increased proline content in the plant leaves. Meanwhile, superoxide dismutase and peroxidase activities were enhanced substantially in the AMF‐only group compared to the control group. The combined treatment with AMF and biochar considerably increased catalase activity and proline content and reduced malondialdehyde content in the plant leaves under low‐temperature stress. In conclusion, AMF and biochar exhibited a synergistic effect in promoting plant growth of L. perenne and played a role in improving plant resistance to low‐temperature stress in the saline soil.

Enhanced photocatalytic activity of Bi24O31Br10 microsheets constructing heterojunction with AgI for Hg0 removal

A range of AgI modified Bi24O31Br10 heterojunction microsheets were produced by a hydrothermal subsequent deposition-precipitation method for highly efficient photocatalytic removal of Hg0 under fluorescent light irradiation. Diverse characterization techniques such as XRD, BET, SEM, TEM, UV − vis DRS, XPS, PL, and ESR were implemented to investigate the properties of the as-fabricated materials. The experimental parameters such as AgI content, sample dosage, pH value of solution, reaction temperature, FSL illumination, inorganic anions, SO2 and NO were employed to evaluate the activity of the materials. It was found that the AgI material was successfully deposited on the surface of Bi24O31Br10 microsheets. In comparison, the dramatic enhancement photocatalytic performance of AgI-Bi24O31Br10 could be assigned to synergies of Bi24O31Br10 and AgI under fluorescent light irradiation, including effective electron-hole separations and generation of photocatalytic active substances at the interfaces of the two semiconductors. AgI loading, inorganic carbonate ion contents and SO2 gas all had significant influence on the removal of Hg0. The 2% AgI-Bi24O31Br10 sample was testified to exhibit an extraordinary enhanced photocatalytic activity. On the basis of the results of ESR detection and radical trapping experiments, reactive substances O2− and h+ were significant players in the photocatalytic reaction.

Source Apportionment of Urban Ammonia and its Contribution to Secondary Particle Formation in a Mid-size European City

ABSTRACT Ambient air pollution caused by fine particulate matter (PM) and trace gases is a pressing topic as it affects the vast majority of the world's population, with a particularly heavy influence in densely populated urban environments. Alongside nitrogen oxides (NOx) and PM, ammonia (NH3) is also a relevant air pollutant due to its role as a precursor of particulate ammonium. This is a study about the short-term temporal dynamics of urban NH3 concentrations in Munster, northwest Germany, the role of road traffic and agriculture as NH3 sources and about the importance of ammonia for secondary particle formation (SPF). The NH3 mixing ratio was rather high (mean: 17 ppb) compared to other urban areas and showed distinct diurnal maxima around 10 a.m. and during the night at 9 p.m. The main source for ammonia in Munster was agriculture, but road traffic also contributed through local emissions from vehicle catalysts. NH3 from surrounding agricultural areas accumulated in the nocturnal boundary layer and contributed to SPF in the city center. Modeled emissions of NH3 as estimated by the Handbook for Emission Factors in combination with traffic counts were in the same magnitude for NH3. The size-resolved chemical composition of inorganic ions in PM10 was dominated by NH4+ (8.66 µg m–3), followed by NO3– (3.89 µg m–3), SO42– (1.58 µg m–3) and Cl– (1.33 µg m–3). Particles in the accumulation range (diameter: 0.1–1 µm) showed the highest inorganic ion concentrations. The ammonium neutralization index J (111%) indicated an excess of NH4+ leading to mostly alkaline PM. High ammonia emissions from surrounding agricultural areas combined with large amounts of NOx from road traffic play a crucial role for SPF in Munster.

Enhancement of lignite microwave dehydration by cationic additives

The addition of materials with high dielectric parameters can improve lignite’s microwave absorption, thereby, enhancing lignite microwave dehydration. In order to explore the promotion effect of cationic additives on this process, five kinds of same and different valence state additives were studied in this paper. The physicochemical properties of the solid and liquid products under each condition were compared and analyzed in detail. Process characteristics, dehydration kinetics, and moisture diffusion coefficient results showed that the higher the cationic valence, the weaker the promotion effect of additives on lignite dehydration. When the cationic valence was the same, the promotion effect of additives was affected by the hydration radius of cations and solubility of additives. After microwave treatment, the pore structure of solid products at first decreased, then increased, ultimately developing into mesopore and micropore regions. Their absorption capacity was weakened according to contact angle tests. The significance was that the combustion of solid products was more complete, and the number of pollutants released was reduced. For liquid products, the content of organic matter and inorganic ions increased greatly. The surface tension first increased, followed by a decrease, indicating that the removal of organic matter gradually exceeded that of inorganic matter, and that additive had an effect on the microwave process of lignite sequentially through dehydration, dissolution of inorganic substances, and destruction of organic structure.

The quality of Slovenian chestnut honey and its specific properties relevant for medical application and functional nutrition

Chestnut honey is well-described in terms of sensory properties, pollen and chemical composition. Specific bitter taste is accompanied with other typical sensory properties derived from its chemical composition, especially in the nectar of sweet chestnut. Compounds from other sources of nectar and honeydew, especially linden, fir and spruce, with smaller amounts from meadow plants, create the specific sensory and chemical properties of Slovene chestnut honey. Based on the chemical composition of the honey, especially the content and proportions of different inorganic ions, it is possible to track the geographical origin of the pasture. Bees contribute significantly to recognized antimicrobial properties of honey by secretion of enzymes and antimicrobial peptides via the food processing glands. When the honey is used for medical purposes, we have to take precautions to avoid microbial and chemical contamination. For the planning of specific use of honey as a medical application we need to explore in detail specific pharmacological properties of single compounds from the chestnut honey and its contribution to the whole activity during wound treatment. In this paper we present a review of most distinct properties of chestnut honey important for its medical application.

Combined measurements of microscopic leaf wetness and dry-deposited inorganic compounds in a spruce forest

Hygroscopic particulate salts on leaf surfaces may facilitate the formation of microscopic leaf wetness, wax degradation, and enhanced of trace gas exchange in forest environments. In order to investigate the interaction of microscopic leaf wetness and dry-deposited inorganic compounds, a field campaign that combined measurements using electrical conductance sensors and leaf washing techniques was carried out in a coniferous forest in Germany during the summer period. Within the canopy, electrical conductivity was directly and continuously measured across a needle surface exposed to the air and covered with branches. Inorganic ion concentrations of washed samples at the top and middle of the canopy were measured and used to estimate leaf-level dry deposition rates of inorganic compounds. The results of both electric conductance and washed ion concentrations indicated the presence of deposited salts on needles within the canopy. Sulfate (SO42−) and nitrate ions (NO3−) were dominant among soluble mass compounds in washed samples. A higher deposition rate of oxidized nitrogen (measured as NO3−) was estimated at the top of the canopy (0.59 μmol m−2 h−1) than in the middle (0.15 μmol m−2 h−1), indicating that dry deposition of oxidized nitrogen mainly occurs near the canopy top. The deliquescent behavior of deposited hygroscopic salts was suggested by a hysteresis effect depending on increasing or decreasing relative humidity in our leaf wetness measurements. The results indicate that deposition of atmospheric inorganic compounds on needles and leaves can facilitate the formation of leaf wetness on the vegetation surface.

Characterization of Rome\u2019s rainwater in the early of 2018 aiming to find correlations between chemical-physical parameters and sources of pollution: a statistical study

Analysis of rainwater in historical cities plays a key role to save ancient monuments from atmospheric agents. In this study we sampled the Rome’s rainwater from February to July of 2018 and we analysed them to determine their chemical and physical parameters: pH, redox potential, conductivity, temperature, and the concentration of the main inorganic ions (Na+, K+, Ca++, Mg++, F−, Cl−, NO3−, SO4−−). The volume of the daily fallen rainwater, the speed and direction of the wind in the sampling site were also collected. In order to find a correlation between all the above data we used the Principal Component Analysis (PCA). Results evidenced that there aren’t authentic “acid rains” as the minimum pH value that we found is 5.2. In some cases high concentrations of nitrates and sulphates were found with maximum values of 12.4 ppm and 18.7 ppm respectively. We also found no correlation between the rainwater’s composition and the seasonal period; on the contrary, the speed and direction of the wind, especially when coming from the sea or industrial country near Rome, play a noticeable role on the rainwater composition.Graphical abstract

Formation of nitrite and ammonium during the irradiation of nitrate-containing water by VUV/UV

Vacuum ultraviolet/ultraviolet (VUV/UV) has been regarded as an efficient chemical-free advanced oxidation process for degradation of micropollutants, but hazardous byproducts, e.g. nitrite, can be formed during the irradiation of nitrate-containing water by VUV/UV. This study investigated the kinetics of nitrite and ammonium formation by VUV/UV irradiation of nitrate. The results indicate that the formation of nitrite and ammonium followed pseudo zero-order reaction kinetics at an initial nitrate concentration of 10 mg L−1. Direct UV photolysis, VUV photolysis, and indirect VUV photolysis contributed to 24.6 %, 44.6 %, and 30.8 % of nitrite formation, and 0%, 65.0 % and 35.0 % of ammonium formation, respectively, in VUV/UV process. Initial nitrate concentration strongly affected not only the final concentrations of nitrite and ammonium but also the kinetics of their formation by VUV/UV. The presence of nitrate inhibited the degradation of alachlor, a typical herbicide, while alachlor had various influence on the formation of nitrite and ammonium depending on its initial concentration. Inorganic anions inhibited nitrate reduction by competing for VUV, while dissolved oxygen inhibited nitrate reduction by scavenging H and eaq−. The surface water had higher rate constants for the formation of nitrite and ammonium than those of the ground water because the former had lower content of inorganic ions but higher content of natural organic matter. When applying the VUV/UV process for water treatment, the formation of nitrite and ammonium should be taken seriously, especially at the presence of nitrate with high concentration.

An interlaboratory comparison of aerosol inorganic ion measurements by ion chromatography: implications for aerosol pH estimate

Abstract. Water-soluble inorganic ions such as ammonium, nitrate and sulfate are major components of fine aerosols in the atmosphere and are widely used in the estimation of aerosol acidity. However, different experimental practices and instrumentation may lead to uncertainties in ion concentrations. Here, an intercomparison experiment was conducted in 10 different laboratories (labs) to investigate the consistency of inorganic ion concentrations and resultant aerosol acidity estimates using the same set of aerosol filter samples. The results mostly exhibited good agreement for major ions Cl−, SO42-, NO3-, NH4+ and K+. However, F−, Mg2+ and Ca2+ were observed with more variations across the different labs. The Aerosol Chemical Speciation Monitor (ACSM) data of nonrefractory SO42-, NO3- and NH4+ generally correlated very well with the filter-analysis-based data in our study, but the absolute concentrations differ by up to 42 %. Cl− from the two methods are correlated, but the concentration differ by more than a factor of 3. The analyses of certified reference materials (CRMs) generally showed a good detection accuracy (DA) of all ions in all the labs, the majority of which ranged between 90 % and 110 %. The DA was also used to correct the ion concentrations to showcase the importance of using CRMs for calibration check and quality control. Better agreements were found for Cl−, SO42-, NO3-, NH4+ and K+ across the labs after their concentrations were corrected with DA; the coefficient of variation (CV) of Cl−, SO42-, NO3-, NH4+ and K+ decreased by 1.7 %, 3.4 %, 3.4 %, 1.2 % and 2.6 %, respectively, after DA correction. We found that the ratio of anion to cation equivalent concentrations (AE / CE) and ion balance (anions–cations) are not good indicators for aerosol acidity estimates, as the results in different labs did not agree well with each other. In situ aerosol pH calculated from the ISORROPIA II thermodynamic equilibrium model with measured ion and ammonia concentrations showed a similar trend and good agreement across the 10 labs. Our results indicate that although there are important uncertainties in aerosol ion concentration measurements, the estimated aerosol pH from the ISORROPIA II model is more consistent.

Insights into measurements of water-soluble ions in PM2.5 and their gaseous precursors in Beijing

To better understand the characteristics and transformation mechanisms of secondary inorganic aerosols, hourly mass concentrations of water-soluble inorganic ions (WSIIs) in PM2.5 and their gaseous precursors were measured online from 2016 to 2018 at an urban site in Beijing. Seasonal and diurnal variations in water-soluble ions and gaseous precursors were discussed and their gas-particle conversion and partitioning were also examined, some related parameters were characterized. The (TNH3) Rich was also defined to describe the variations of the excess NH3 in different seasons. In addition, a sensitivity test was carried out by using ISORROPIA II to outline the driving factors of gas-particle partitioning. In Beijing, the relative contribution of nitrate to PM2.5 has increased markedly in recent years, especially under polluted conditions. In the four seasons, only a small portion of NO2 in the atmosphere was converted into total nitrate (TNO3), and more than 80% of TNO3 occurred in the form of nitrate due to the abundant ammonia. The concentration of total ammonia (TNH3) was much higher than that required to neutralize acid gases, and most of the TNH3 occurred as gaseous NH3. The nitrous acid (HONO) concentration was highly correlated with NH3 concentration and had increased significantly in Beijing compared with previous studies. The total chloride (TCl) was the highest in winter, and ε(Cl−) was more sensitive to variations in the ambient temperature (T) and relative humidity (RH) than ε(NO3−).

Influence of inorganic ions on degradation capability of Fe-based metallic glass towards dyeing wastewater remediation

Metallic glasses (MGs) are promising candidates for catalysts with high efficiency for dyeing wastewater remediation, due to their metastable nature, disordered structure, and large residual stresses. However, dyeing wastewater usually contains a high concentration of inorganic ions which may have adverse effects on the degradation process, while the impacts of these ions on MGs’ degradation capability have often been overlooked and still remain unknown. Thus, the roles of inorganic ions (Cl-, NO3-, SO42-, and H2PO4-) on the degradation of azo dye by Fe-based MG with nominal composition of Fe81Si4B14Cu1 were systematically investigated. The results showed that the inorganic ions have significant influence on MG’s surface morphology, degradation capability, mineralization and durability. All these aspects need to be considered prior to application of MGs for azo dyes degradation in real natural contaminated water or saline wastewater.

Characterization of Two Heavy Pollution Episodes in Tianjin in 2020

High-resolution online monitoring data from January to February in 2020 was used to study the characterization of two heavy pollution episodes in Tianjin in 2020; the heavy pollution episode that lasted from January 16 to 18, 2020 (referred to as episode Ⅰ) and that from February 9 to 10, 2020 (referred to as episode Ⅱ) were analyzed. The results showed that two heavy pollution episodes were influenced by regional transportation in the early stage and local adverse meteorological conditions in the later stage. During these episodes, the average wind speed was low, the average relative humidity was close to 70%, and relative humidity approached the saturated, the boundary layer heights were below 300 m, and the horizontal and vertical diffusion conditions were poor. Compared to episode Ⅰ, the concentration of pollutants decreased during episode Ⅱ, especially for the concentration of NO2. During the episode Ⅱ, the concentrations of PM2.5 and CO were higher in the north of Tianjin. The chemical component concentrations and their mass ratios to PM2.5 changed significantly in both episodes; the concentrations of secondary inorganic ions (NO3-, SO42-, and NH4+), elemental carbon (EC) and Ca2+were higher in episode Ⅰ, the concentrations of organic carbon (OC) and Cl- slightly increased in episode Ⅱ; and the concentrations of K+were higher in episode Ⅱ. Compared to episode Ⅰ, because of the increase in the combustion sources and significant reductions in the number of vehicles, the mass ratios of SO42-, OC, and K+ to PM2.5 increased while the mass ratios of NO3- and EC to PM2.5 decreased in episode Ⅱ; the mass ratios of NH4+ and Cl- to PM2.5 were relatively higher due to the continuity of the industrial production processes; the mass ratios of Ca2+ to PM2.5 were lower in two heavy pollution episodes because construction activities were halted. Source apportionment of PM2.5 was performed using the positive matrix factorization (PMF) model. In episode Ⅰ, the major sources of PM2.5 in Tianjin were secondary sources, industrial and coal combustion, vehicle exhaust, crustal dust, fireworks and biomass burning, with contributions of 53.8%, 20.2%, 18.6%, 6.3%, and 1.1%, respectively. In episode Ⅱ, the same sources were identified in the PMF analysis with contributions of 48.3%, 28.2%, 8.7%, 2.6%, and 12.2%, respectively. Compared to episode Ⅰ, the contributions of industrial and coal combustion, fireworks and biomass burning increased, and the contributions of secondary sources, vehicle exhaust, and crustal dust decreased in episode Ⅱ; contributions of vehicle exhaust and crustal dust decreased by 53.2% and 58.7%, respectively.

Seasonal Characteristics and Source Analysis of Water-soluble Inorganic Ions in PM2.5 in Suqian City

To study the seasonal pollution characteristics and sources of water-soluble inorganic ions in atmospheric PM2.5 in Suqian City, 171 samples were collected at three monitoring points, which were in the water vapor channel, from May 2017 to January 2018. The mass concentrations of PM2.5 and nine water-soluble inorganic ions were analyzed. The results showed that the annual average concentration of water-soluble inorganic ions in PM2.5 in Suqian City was (44.08±34.61) μg ·m-3, accounting for 41.8% of PM2.5. The concentrations of these species were in the order of ρ(NO3-) > ρ(SO42-) > ρ(NH4+) > ρ(ρl-) > ρ(Na+) > ρ(Ca2+) > ρ(K+) > ρ(F-) > ρ(Mg2+); NO3-, SO42-, and NH4+ accounted for 75.6% of the total water-soluble ions. The annual average ratio of ρ(NO3-) to ρ(SO42-) was 1.53±0.88, indicating that mobile sources contributed more to PM2.5 pollution. Based on the correlation analysis of NH4+ and SO42-, NO3- may exist in the form of (NH4)2 SO4, NH4HSO4, or NH4NO3. According to the principal component analysis, secondary transformation, industrial pollution, biomass burning, and dust were the major sources of water-soluble inorganic ions. PM2.5concentrations were positively related to relative humidity in winter. Water vapor transmission is more likely to promote PM2.5 accumulation in winter.

Physical and chemical characteristics of 1300 lakes and ponds across the Canadian Arctic

Lakes and ponds are a major feature of the Arctic landscape and are recognized as effective ‘sentinels of change’. Here we present water chemistry characteristics of lakes and ponds (n=1300 with 26 variables) across the Canadian Arctic collated from published studies. We also extracted geological and ecoregion data in an attempt to determine the key drivers. In general, most lakes were shallow (85.4%, <10 m), nutrient (phosphorus) poor (oligotrophic = 45.6% and ultra-oligotrophic = 24.8%), located at low elevation (66.5%, <200 m asl), close to coastlines (72.5%, 0-50 km), and underlain by sedimentary geology (66.5%). The first two components from Principal Component Analysis explained 49.3% of the variation in the dataset; the first component was dominated by conductivity/carbonate materials, and the second component suggested allochthonous inputs of phosphorus. In general, bedrock geology is the primary driver of water chemistry; as such, there were major differences between lakes underlain by igneous and sedimentary rocks. Those on sedimentary bedrock tend to have higher pH, nutrients and higher inorganic ion concentrations.

Ammonia control represents the key for PM2.5 elimination: insights for global air pollution control interconnected from PM2.5 events in China

Aerosol particulate represented by PM2.5 is a globally environmental issue, which is associated with severe adverse impacts on human health and global climate. To address that problem, the urgent challenge is to find out the most important factor for PM2.5 formation and therefore conduct more effective control. Herein, the characteristic and control strategy of PM2.5 pollution in China is investigated, aiming to provide new insights for global air pollution control. Spatial and chemical characteristics of PM2.5 in China are analyzed according to large amounts of air monitoring data. Charge analysis of PM2.5 is conducted based on the concentration of water-soluble inorganic ion. Achievement and shortage of recent PM2.5 control strategies are studied through policy analysis. PM2.5 pollution is highly related to local population and economic development. NH4+ represents the main cation in PM2.5 and plays a key role in particulate generation. Ammonia is found to be concentrated in North China Plain of China, which is consistent with PM2.5 spatial distribution. To further abate the PM2.5, ammonia emission from nitrogenous fertilization, livestock manures and industrial denitrification process should be controlled.