Concentrations Of Chemical Constituents Research Articles

Solvent and stoichiometry-dependent versatile organogelation and robust crystallization from the supramolecular association of adipic acid and triethanolamine

Depending on stoichiometry, concentrations of chemical-constituents and solvent media, the formation strategy of robust supramolecular crystalline systems and two diverse supramolecular organogels is explored and characterized.

Unveiling the Impact of Drying Methods on Phytochemical Composition and Antioxidant Activity of Anthemis palestina.

Different drying techniques may alter the chemical composition of plant extracts and consequently affect their bioactivity potential. The current study was designed to reveal the effect of four different drying methods on the phytochemical composition and antioxidant activity of hydrodistilled essential oil (HD-EO) and methanolic (APM) extract obtained from the aerial part of Anthemis palestina from Jordan. Aerial parts of A. palestina in their fresh (FR) form and after drying in shade (ShD), sun (SD), oven at 40 °C (O40D) and 60 °C (O60D), in addition to microwave (MWD), were used to extract their essential oils by hydrodistillation and to prepare the different methanolic extracts (APM). GC/MS analysis of the different HD-EOs revealed qualitative and quantitative differences among the different samples. While FR, O40D, O60D, and MWD EO samples contained mainly sesquiterpene hydrocarbons (35.43%, 29.04%, 53.69%, and 59.38%, respectively), ShD sample was rich in oxygenated monoterpenes (33.57%), and SD-EO contained mainly oxygenated sesquiterpenes (40.36%). Principal component analysis (PCA) and Cluster analysis (CA) grouped the different drying methods based on their impact on the concentration of chemical constituents. SD-EO demonstrated high DPPH and ABTS antioxidant activity (1.31 ± 0.03) × 10-2; (1.66 ± 0.06) × 10-2 μg/mL, respectively). Furthermore, A. paleistina methanolic extracts (APM) obtained after subjecting the plant to different drying methods showed interesting patterns in terms of their TPC, TFC, antioxidant activity, and phytochemical profiling. Of all extracts, SD-APM extract had the highest TPC (105.37 ± 0.19 mg GA/g DE), highest TFC (305.16 ± 3.93 mg Q/g DE) and demonstrated the highest DPPH and ABTS scavenging activities ((4.42 ± 0.02) × 10-2; (3.87 ± 0.02) × 10-2 mg/mL, respectively); all were supported by correlation studies. LC-MS/MS analysis of the different extracts revealed the richness of the SD-APM extract in phenolic acids and flavonoids.

A Comparative Study on Ascorbic Acid Concentration, Total Phenol, and Flavonoid Content in Citrus Species Grown in a Different Region of Western Nepal.

Different genetic and environmental factors like altitude, temperature, light radiation, etc. affect the production of phytoconstituents like ascorbic acid, phenol, flavonoid, tannin, etc. So, it is necessary to evaluate phytoconstituents quantitatively and qualitatively because of their different medicinal values. This study is aimed at evaluating and comparing ascorbic acid concentration, total phenol, and flavonoid content in citrus species grown in different places in Western Nepal. For this, fruit collected from Lamjung and Nawalparasi was peeled, and collected juice was extracted with ethanol. Ascorbic acid was estimated using titration with dichlorophenolindophenol dye, and total phenol was estimated using Folin reagent; whereas, flavonoid content was determined by aluminum chloride colorimetric assay. The result showed the maximum ascorbic acid concentration in the fruit juice of Citrus maxima collected from Lamjung, i.e., 2.98 ± 0.161 mg/100 ml, and the least concentration was recorded on extract of Citrus limon collected from Nawalparasi, i.e., 1.005 ± 0.205 mg/100 ml. The total phenol content was comparatively higher in Citrus maxima and Citrus aurantifolia collected from Lamjung, i.e., 12.48 ± 0.40 mg GAE/gm, respectively. Flavonoid content was comparatively higher in Citrus maxima collected from Nawalparasi, i.e., 484.466 ± 3.055 mg QE/gm. This study showed a variation in the concentration of chemical constituents between different places in Western Nepal. This might be due to differences in climatic conditions, environmental factors, altitude, temperature, etc. This study helps to reflect the best-suited altitude for commercial cultivation of the citrus species as these phytochemicals have different medicinal values. Also, this study can help the food industry to use an alternative source of synthetic antioxidant such as ascorbic acid, phenol, and flavonoid. And local people will economically benefit by the commercial cultivation of citrus fruits.

Use of Hydrodistillation to Obtain and Fractionate Essential Oils Simultaneously

A simple method was developed to obtain and fractionate essential oil simultaneously by hydrodistillation. With this method it was possible to obtain essential oils from the leaves of Piper arboreum with the cadinol content ranging from 17.7 to 57.9%. In the essential oils from the leaves of P. aduncum was identified dillapiole with content ranging from 4.6 to 96.9%; and further, essential oil from P. marginatum with the presence of phenylpropanoids as minor compounds. The essential oils of the three Piper species varied in antimicrobial activity when fractionated, with P. marginatum oil exhibiting the lowest minimum inhibitory concentration at 19.5 µg mL-1 for the Pseudomonas aeruginosa bacterium. The method was efficient for the separation and concentration of chemical constituents of essential oils from the same plant, able to distinguish the different chemical profiles, both qualitatively and quantitatively.

Comparison of the effects of three types of heating tobacco system and conventional cigarettes on indoor air quality

Environmental tobacco smoke (ETS) from conventional cigarettes is reported to affect indoor air quality (IAQ) in various real indoor environments. Recently, Japan Tobacco Inc. introduced three types of tobacco product that are heated rather than combusted. These comprise one direct heating tobacco system and two in-direct heating tobacco systems. In this study, the impact of using these products on IAQ was evaluated in an environmentally controlled chamber. Two environmental conditions, simulating restaurant and residential spaces, were examined. Under the same conditions, cigarette smoking and the presence of people only were used as positive and negative controls, respectively. The indoor air concentrations of 48 constituents (tobacco-specific nitrosamines, carbonyls, volatile organic compounds, total volatile organic compounds, polycyclic aromatic hydrocarbon, polycyclic aromatic amines, mercury, metals, ETS markers, propylene glycol, glycerol, carbon monoxide, carbon dioxide, suspended particle matter, ammonia, and nitrogen oxides) were measured. Compared with the presence of people, the concentrations of some constituents were actually increased when using heating tobacco products under both environmental conditions, simulating restaurant and residential spaces. However, the constituent concentrations were lower than those obtained by cigarette smoking, except for propylene glycol and glycerol, and below the exposure limits for constituents in air, as defined by air quality guidelines or regulations. Based on these data, the use of heating tobacco systems in appropriate indoor environments has less impacts compared to conventional cigarettes.Article HighlightsWe measured the indoor air concentrations of chemical constituents generated when using three heating tobacco systems with different heating mechanisms in two environment conditions simulating restaurant and residential spaces (positive control: when smoking cigarettes, negative control: the presence of people only).In the measurement and analysis method used this study, it was possible to find not only that the air concentration generated when using the heating tobacco systems in this study were considerably lower than that when smoking cigarettes, but also the differences of the concentrations between heating tobacco systems with different heating mechanisms.We showed some constituents which actually increased the air concentrations when using heating tobacco systems compared with the presence of people only.

A Low-Cost Digital Colorimetry Setup to Investigate the Relationship between Water Color and Its Chemical Composition.

Developments in digital image acquisition technologies and citizen science lead to more water color observations and broader public participation in environmental monitoring. However, the implications of the use of these simple water color indices for water quality assessment have not yet been fully evaluated. In this paper, we build a low-cost digital camera colorimetry setup to investigate quantitative relationships between water color indices and concentrations of optically active constituents (OACs). As proxies for colored dissolved organic matter (CDOM) and phytoplankton, humic acid and algae pigments were used to investigate the relationship between water chromaticity and concentration. We found that the concentration fits an ascending relationship with xy chromaticity values and a descending relationship with hue angle. Our investigations permitted us to increase the information content of simple water color observations, by relating them to chemical constituent concentrations in observed waters.

Vulnerability of municipal solid waste: An emerging threat to aquatic ecosystems

Dumping waste materials into aquatic ecosystems leads to pollution, which directly and indirectly poses a danger to all life forms. Currently, huge quantities of wastes are generated at a global scale with varying constituents, including organic fractions, emerging contaminants and toxic metals. These wastes release concentrated contaminants (leachates), which are lethal for all ecosystems around the globe because they contain varying concentrations of chemical constituents with BOD5 and COD in the order of 2 × 104–2.7 × 104 mg/L, and 3.4 × 104–3.8 × 104 mg/L, respectively. Herein, in-depth knowledge of municipal solid waste dumping into the aquatic ecosystems, changes in physicochemical characteristics, availability of in-/organic contaminants, and long-term unhealthy effects are presented. Moreover, an attempt has been made here to summarize the facts related to identifying the deadly impacts of waste on different ecosystem components. The unresolved challenges of municipal waste management are emphasized, which will help employ suitable waste management techniques and technologies to conserve the everlasting freshwater resources on earth.

Differences in fine particle chemical composition on clear and cloudy days.

Clouds are prevalent and alter PM2.5 mass and chemical composition. Cloud-affected satellite retrievals are often removed from data products, hindering estimates of tropospheric chemical composition during cloudy times. We examine surface fine particulate matter (PM2.5) chemical constituent concentrations in the Interagency Monitoring of PROtected Visual Environments network during Cloudy and Clear Sky times defined using Moderate Resolution Imaging Spectroradiometer (MODIS) cloud flags from 2010-2014 with a focus on differences in particle hygroscopicity and aerosol liquid water (ALW). Cloudy and Clear Sky periods exhibit significant differences in PM2.5 and chemical composition that vary regionally and seasonally. In the eastern US, relative humidity alone cannot explain differences in ALW, suggesting emissions and in situ chemistry exert determining impacts. An implicit clear sky bias may hinder efforts to quantitatively to understand and improve model representation of aerosol-cloud interactions.

Potential health risk and levels of heavy metals in water resources of lead\u2013zinc mining communities of Abakaliki, southeast Nigeria

Heavy metals are potential health risk, especially in mining sites where they deteriorate from sulfide-rich ore bodies. Lead, cadmium, arsenic and mercury are very carcinogenic, while others are toxic. The assessment of the levels of these metals in water resources of the lead–zinc mining communities of Enyigba, Mkpuma Akpatakpa, Ameka, Amorie, Amanchara and Alibaruhu was carried out, and the potential health risk has been investigated. These areas make up the main mining communities of Abakaliki, where active and abandoned mines are located. One hundred and six water samples were analyzed in two seasons using atomic absorption spectrophotometric and ultra-violet/visible spectroscopy. Result indicates levels of Pb2+ > Hg2+ > As2+ > Cd2+ > Mn2+ > Ag2+ > Se2+ > Ni2+ > Cr2+ > Cu2+ in water sources. High levels of Mn2+(63.45 mg/L), Pb2+(11.42 mg/L), Cr3+(14.60 mg/L), Ni2+(1.260), Cd2+(15.67 mg/L), Ag+(6.06 mg/L), Hg2+(2.60 mg/L), As(4.13 mg/L), Se2+(2.68 mg/L), Zn2+(10.53 mg/L) and Co2+(0.9 mg/L) above the WHO recommended standard for drinking water were observed. Only Cu2+ recorded safe concentrations in 100% samples analyzed. Levels of associated metals including Pb2+, As, Hg2+, Se2+ and Cd2+ are higher in groundwater especially in areas close to the active mines; this is due to mineralization in the area. Seasonal analysis shows a decreased concentration of chemical constituents in the rainy season relative to the dry season. Potential health risk is associated with accumulation of toxic heavy metals in tissues including Parkinson disease, arsenicosis, acrodynia, selenoises, Alzheimer’s disease, hair loss, mental imbalance and abortion in women abound in the areas. Alternative water supply sources and sensitization on the potential health risk are highly advocated in these communities.

Occurrence and distribution of heavy metal in arable soils around lead–zinc mining sites of Abakaliki, Southeast Nigeria

This study involved the geochemical assessment of the occurrence and distribution of heavy metals in available agricultural soils and stream sediments in the lead–zinc mining areas of Abakaliki, Southeastern Nigeria. A total area of about 794.2 km2 was assessed, with major communities covered including Enyigba, Mkpuma Akpatakpa, Ameka, Amorie, Amanchara and Alibaruhu where active and abandoned mines are located. One hundred and sixteen soil/stream sediments were collected and subjected to geochemical analysis using the atomic absorption spectrophotometric method. The result shows concentration of Cd > Pb > As > Zn > Cu > Ag > Hg > Cr, especially in the areas close to the active mines. The contamination percentage of metal in samples shows Cd (40.51%), Pb (36.20%), As (23.27%), Zn (17.24), Cu (8.62%) and Cr (0%). This implies that arable soils around the mining areas are not suitable for food crop production as biomagnification can occur in the food chain. The consumption of food produce in these areas can lead to potential health risk as they accumulate. However, the Mkpuma Akpatakpa and Ameka areas show higher distribution of these metals than the Enyigba and Amanchara areas. Seasonal analysis shows a decreased concentration of chemical constituents in the rainy season relative to the dry season except for Cd, Cr and Hg.

Soil Quality as Affected by Municipal Solid Waste Dumping

This paper presents soil quality as affected by dumped municipal solid waste. Landfill leachate was collected from a hole dug 10 m away from the waste dump site for laboratory analysis. Soil samples were also collected from four trial pits in the dumpsites at the depth of 0.3, 0.6 and 0.9 m and at a distance of 10, 20, 30 m and the control 100 m away from the dumping site. The collected soil samples were subjected to physiochemical and geotechnical analysis. This includes particle size distribution, pH, EC, total organic carbon, total organic matter, extractable micronutrients and heavy metals (Zn, Cu, Mn, Fe, Pb, Cd, Cr, Cl and Ni), Attterberg limits, specific gravity and hydraulic conductivity. The physicochemical concentration was then compared with the maximum allowable concentrations of chemical constituents in uncontaminated soil. The Laboratory analysis shows high value of pH (8.51) DO (0.17 mg/l), COD (68mg/l), BOD5 (324 mg/l), Pb (0.31 mg/l) and Cd (0.06 mg/l) in the leachate sample. The physical properties of the soil near the dumpsite indicated that the soil belongs to sandy loam in texture. pH (6.3-8.32), Electrical conductivity (241-2018 s/cm), total organic carbon (0.24-2.16 ) and total organic matter (0.41-3.73%) were higher near the vicinity of the dumpsite and decreased with increase in the depth and distance. Extractable micro nutrient and heavy metal concentration (Zn, Cu, Mn, Fe, Pb, Cd, Cr, Cl and Ni) were also found to be high near the dumpsite and decreased along the soil depth and distance from the dumping site. The variance in the geotechnical properties of soil revealed by the test results was impacted by the dumped municipal solid waste. These effects decrease with increase in depth. These findings will help in facilitating the invention and introduction of site specific technologies.

Heavy metals occurrence, assessment and distribution in water resources of the lead–zinc mining areas of Abakaliki, Southeastern Nigeria

The assessment, occurrence and distribution of heavy metals in water resources of the lead–zinc mining areas of Abakaliki, Southeastern Nigeria, were carried out. Major communities including Enyigba, Mkpuma Akpatakpa, Ameka, Amorie, Amanchara and Alibaruhu where active and abandoned mines are located were assessed. This study compared the prevalence of these metals in the different mining communities. One hundred and six water samples were analyzed in two seasons using Atomic Absorption Spectrophotometer and Ultra-Violet/Visible Spectroscopy. Results were compared with World Health Organization Standard (WHO) for drinking water. Result indicates high concentrations with ranges: Mn2+ (63.45 mg/L), Pb2+ (11.42 mg/L), Cr3+ (14.60 mg/L), Ni2+ (1.260), Cd2+ (15.67 mg/L), Ag+ (6.06 mg/L), Hg2+ (2.60 mg/L), As (4.13 mg/L), Se2+ (2.68 mg/L), Zn2+ (10.53 mg/L), Co2+ (0.9 mg/L). These are above the WHO recommended standard for drinking water. Only Cu2+ and Se2+ recorded safe concentrations in 100% samples analyzed in both surface and groundwater in the rainy season. Percentage contamination shows Pb2+ > Hg2+ > As2+ > Cd2+ > Mn2+ > Ag2+ > Se2+ > Ni2+ > Cr2+>Cu2+especially in areas close to the active mines. Surface water resources recorded higher contamination. However, Pb2+, As, Hg2+, Se2+ and Cd2+ showed high percentage of contamination in groundwater samples. The Ameka and Mkpuma Akpatakpa mining areas recorded higher concentrations of the hydrogeochemical constituents than the Enyigba, Ameka and Amorie mining regions. Seasonal analysis shows a decreased concentration of chemical constituents in the rainy season relative to the dry season.

Effect of fly ash-lime treatment on the acute toxicity of greywater towards Daphnia magna

Abstract Acute toxicity of raw and treated greywater towards Daphnia magna was assessed in this study. Treatment was performed with exposure of greywater to the fly-lime mixture After 48 h of exposure, 100 % mortality of D. magna was recorded when testing the following volumetric fractions of the raw greywater streams in the tested liquid medium (%; v/v): 10 % for kitchen greywater, 5 – 10 % for bathroom greywater and 1.25 – 10 % for laundry greywater. After greywater treatment with the fly-ash-lime mixture with pH adjustment to 7.0, 80 % of neonates of D. magna survived after exposure to treated laundry greywater in all dilutions at 48 h. At the same time, 100 % of neonates survived exposure to treated bathroom and kitchen greywater at all volumetric fractions. Therefore greywater had acute toxicity to D. magna, i.e. greywater treatment was required before its discharge or reuse. Values of the Pearson’s correlation coefficient between the chemical components of the raw greywater and treated greywater and the survival of D. magna indicated a lack of statistically significant correlation at 5 % level of significance (p-value > 0.05 in all cases), i.e. the survival of D. magna was independent of the concentration of chemical constituents in greywater samples tested. Further studies will have to be conducted on the chronic toxicity of the greywater effluent after treatment with the fly-lime mixture. Experiments from this study will have to be re-run for the fully scaled-up version of the fly-lime mixture-based greywater treatment systems.

A Study on Elevated Concentrations of Submicrometer Particles in an Urban Atmosphere

Mass concentrations of chemical constituents (organics, nitrate, sulfate, ammonium, chloride, and black carbon (BC)) and the number size distribution of submicrometer particles in the ambient atmosphere were continuously measured in urban Gwangju, Korea, during the Megacity Air Pollution Studies (MAPS)-Seoul campaign. Organics (9.1 μg/m3) were the most dominant species, followed by sulfate (4.7 μg/m3), nitrate (3.2 μg/m3), ammonium (2.6 μg/m3), and BC (1.3 μg/m3) in submicrometer particles (particulate matter less than 1 μm (PM1)). The potential source regions of the sulfate were located in the South and East regions of China and South and East regions of Korea, while local sources were responsible for the elevated BC concentration. Diurnal variation showed that concentrations of organics, nitrate, ammonium, chloride, and BC decreased with increasing mixing layer and wind speed (dilution effect), while sulfate and oxidized organics increased possibly due to their strong photochemical production in the afternoon. During the campaign, an elevated mass concentration of PM1 (PM1 event) and number concentration (nanoparticle formation (NPF) event) were observed (one PM1 event and nine NPF events out of 28 days). The PM1 event occurred with Western and Southwestern air masses with increasing sulfate and organics. Long-range transported aerosols and stagnant meteorological conditions favored the elevated mass concentration of submicrometer particles. Most of the NPF events took place between 10:00 and 14:00, and the particle growth rates after the initial nanoparticle formation were 7.2–11.0 nm/h. The times for increased concentration of nanoparticles and their growth were consistent with those for elevated sulfate and oxidized organics in submicrometer particles under strong photochemical activity.

Major Constituents of Different Propolis Samples

In this study, concentrations of chemical constituents of eight propolis samples collected from different geographical locations were examined by Gas Chromatography and Mass Spectrometry (GC-MS). As a result, hydrocarbons, aliphatic acids and their esters, carboxylic acids and their esters, cinnamic acids and their esters, flavonoids, alcohols and terpens were determined in propolis samples. It was found that total flavonoid content of propolis 6 (P6) was significantly higher than other samples. Also, ‘Ethyl oleat’ compound was determined in all samples with different amounts.

The impact of partition coefficient data on the interpretation of chemical tracer behaviour in carbon geosequestration projects

Partition (or distribution) coefficients determine the relative equilibrium concentrations of chemical constituents (or chemical tracers) in each of the phases of a multi-phase system under dilute conditions. The various fluid phases in a reservoir have differing transport properties (e.g. varying relative permeability) and to correctly interpret the behaviour of injected chemical tracers it is essential that accurate partition coefficients are known. In the context of carbon geosequestration or long-term storage of CO2, chemical tracers will be predominantly exposed to an environment consisting of supercritical CO2 and formation water as the main fluid phases. To estimate/simulate the reservoir properties relevant to injected CO2 tagged with chemical tracers, it is therefore necessary to incorporate high pressure/temperature CO2/water partition coefficients into any model/simulation. In this paper, we present a method to determine these partition coefficients for gaseous chemical tracers using a variation of the widely used EPICS (or equilibrium partitioning in a closed system) method. With this method, only the concentration in one phase (in this case, CO2) needs to be measured. We then report these values for a series of representative chemical tracers (i.e. krypton, xenon, sulfur hexafluoride, perdeuterated methane and R134a) at pressure/temperature conditions that have been previously used at the CO2CRC's Otway CCS demonstration project in Victoria, Australia. These values were generally lower than the corresponding Henry's Law coefficients at comparable temperatures. Experiments also examined the impact of adding CH4 to the system to mimic feedstock gas at the CO2CRC Otway project and provide data pertinent to scenarios where CO2 is injected into depleted CH4 gas fields. These values are compared with Henry's Law coefficients and another recently published set of high pressure/temperature partition coefficients. With computational simulations, we have shown that these differences are potentially significant and demonstrate their impact in three typical CO2 geo-sequestration scenarios (i.e. injection into two types of aquifers and injection into a depleted reservoir with a gas cap).

Study on Ambient Air Quality of Megacity Delhi, India During Odd–Even Strategy

State Government of Delhi had adopted odd–even scheme on vehicles plying in megacity Delhi to understand and improve the air quality of Delhi. To understand the effect of odd–even scheme on the concentration of pollutants, we have analysed the concentrations of chemical constituents [organic carbon, elemental carbon, water soluble inorganic components, trace elements and stable carbon and nitrogen isotopic composition (δ13CTC) and N (δ15NTN)] of PM2.5 and PM10 along with mixing ratios of trace gases (NOx, CO, SO2 and NH3) data collected at an urban site of megacity Delhi during first phase (Phase-I: winter 2016) and second phase (Phase-II: summer 2016). During the Phase-I of the scheme, mass concentrations of PM2.5 and PM10 were changed by −13 and −5%, respectively, whereas, concentrations of PM2.5 and PM10 were changed by +18 and +16%, respectively during the Phase-II as compared to before the implementation of the scheme. The analysis of chemical constituents of PM2.5 and PM10 reveals that the odd–even strategy marginally changed the concentrations (markers) of vehicular emission. During both the phases, mixing ratios of trace gases (NOx, CO, SO2 and NH3) were reduced non-significantly during the odd–even scheme as compared to before the implementation of the scheme.

A numerical framework for modelling sediment and chemical constituents transport in the Lower Athabasca River

The transport of fine sediments and associated chemical constituents originating from potential anthropogenic and natural sources is becoming an issue of increasing importance in the Lower Athabasca River (LAR) ecosystem in northern Alberta, Canada. This study aims to (1) establish an integrated numerical modelling framework to investigate the transport of fine cohesive sediments and associated chemical constituents during both ice-covered and open-water periods and (2) apply the modelling framework to investigate the state and temporal/spatial variation in sediment and selected chemical constituents within the LAR. One-dimensional hydrodynamic and transport models, combined with a river ice model, are used to predict the flow characteristics, transport of sediments and a selection of three metals and three polycyclic aromatic hydrocarbons (PAHs) within a ∼200 km reach of the LAR, both in open-water and ice-covered conditions. The models are validated using available field measurements and are applied to investigate the state and variation of sediment and chemicals for a baseline period as well as to assess the effect of various hypothetical pollution scenarios. The model simulations successfully reproduce the hydrodynamics and sediment transport patterns as well as the state and variation of selected metal and PAH constituents. The results generally show that the concentration of chemical constituents in the bed sediment is the major factor in determining the state and variation of their concentration in the water column, and the high-flow season is the critical period for the transport of sediment and chemicals in the system. The scenario simulation results indicate that increases in the concentrations of chemical constituents in tributary streams have to be orders of magnitude higher to have a noticeable effect on their corresponding water column concentration in the LAR. Those effects are also found to be higher only within the immediate vicinity of the tributary confluences and gradually diminish with distance downstream of the confluences. The numerical modelling framework developed in this study provides a tool for investigation and understanding of the state and temporal/spatial variation of sediment and associated chemical constituents within cold region rivers such as the LAR. By conducting additional scenario-based studies (such as future climate and chemicals loading), the models can be used to identify possible future states of sediment and water quality constituents in the LAR ecosystem.

Study of an adaptable calibration model of near-infrared spectra based on KF-PLS

The key to the quantitative analysis of near-infrared spectra is the establishment of an accurate and adaptable model. In this paper, a calibration method of a dynamic evolutionary model combined with Kalman filter (KF) and partial least squares (PLS) algorithms is proposed. First, an initial quantitative calibration model is built by applying the method of PLS regression to calculate the spectral data samples and their chemical constituent concentrations. Second, inspired by the dynamic evolution characteristics of the KF, the main PLS factor coefficient iterative method is set up based on the KF, by which the calibration model is dynamically corrected. Finally, to prove the validity of the proposed method, a near-infrared spectral dataset from a real corn sample is tested, and the standard PLS method and KF-PLS method are compared. For the 40 external samples (2015), the root mean square error of prediction (RMSEP) of the PLS model was 0.7046% (moisture) and 0.9352% (protein), which is obviously worse than the effects of the KF-PLS model (moisture, 0.3726%, and protein, 0.5451%). Moreover, the R2val (validation decision coefficient) of the KF-PLS model was 0.9035 (moisture) and 0.8565 (protein), which is better than the result of the PLS model (moisture, 0.5659, and protein, 0.6654). Regarding the ability to adapt to equipment (disturbance factor equal to 15%), KF–PLS (RMSEP: moisture, 0.1942%, and protein, 0.3299%; R2val: moisture, 0.9221, and protein, 0.8936) had less prediction error than PLS (RMSEP: moisture, 0.8546%, and protein, 1.0881%; R2val: moisture, 0.5077, and protein, 0.4946). The proposed method has satisfactory accuracy in tracking the evolution of the near-infrared spectrometry measurement state. The novel algorithm can effectively detect the moisture and protein concentration in corn and is also more compatible with outdated equipment, environmental changes and external samples than the PLS algorithm. Thus, this study explores a new approach towards a highly adaptive near-infrared spectrum calibration model.

A model-based approach for imputing censored data in source apportionment studies.

Sources of particulate matter (PM) air pollution are generally inferred from PM chemical constituent concentrations using source apportionment models. Concentrations of PM constituents are often censored below minimum detection limits (MDL) and most source apportionment models cannot handle these censored data. Frequently, censored data are first substituted by a constant proportion of the MDL or are removed to create a truncated dataset before sources are estimated. When estimating the complete data distribution, these commonly applied methods to adjust censored data perform poorly compared with model-based imputation methods. Model-based imputation has not been used in source apportionment and may lead to better source estimation. However if the censored chemical constituents are not important for estimating sources, censoring adjustment methods may have little impact on source estimation. We focus on two source apportionment models applied in the literature and provide a comprehensive assessment of how censoring adjustment methods, including model-based imputation, impact source estimation. A review of censoring adjustment methods critically informs how censored data should be handled in these source apportionment models. In a simulation study, we demonstrated that model-based multiple imputation frequently leads to better source estimation compared with commonly used censoring adjustment methods. We estimated sources of PM in New York City and found estimated source distributions differed by censoring adjustment method. In this study, we provide guidance for adjusting censored PM constituent data in common source apportionment models, which is necessary for estimation of PM sources and their subsequent health effects.