A novel method for quantitative determination of multiple substances using Raman spectroscopy combined with CWT.

The identification of mixed solutions is a challenging and important subject in chemical analysis. In this paper, we propose a novel workflow that enables rapid qualitative and quantitative detection of mixed solutions. We use a methanol-ethanol mixed solution as an example to demonstrate the superiority of this workflow. The workflow includes the following steps: (1) converting Raman spectra into Raman images through CWT; (2) using MobileNetV3 as the backbone network, improved multi-label and multi-channel synchronization enables simultaneous prediction of multiple mixture concentrations; and (3) using transfer learning and multi-stage training strategies for training to achieve accurate quantitative analysis. We compare six traditional machine learning algorithms and two deep learning models to evaluate the performance of our new method. The experimental results show that our model has achieved good prediction results when predicting the concentration of methanol and ethanol, and the coefficient of determination R2 is greater than 0.999. At different concentrations, both MAPE and RSD outperform other models, which demonstrates that our workflow has outstanding analytical capabilities. Importantly, we have solved the problem that current quantitative analysis algorithms for Raman spectroscopy are almost unable to accurately predict the concentration of multiple substances simultaneously. In conclusion, it is foreseeable that this non-destructive, automated, and highly accurate workflow can further advance Raman spectroscopy.

[Analysis of Seasonal Variations in Chemical Characteristics and Sources of PM2.5 During Summer and Winter in Ji'nan City].

To investigate seasonal variations in the chemical compositions of aerosols in Ji'nan City, PM2.5 samples were collected during summer and winter in 2015. The sampling period lasted one month during each season. PM2.5 samples were analyzed for the composition, concentration, and sources of water-soluble inorganic ions, organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC). Results showed that mass concentrations of PM2.5 in winter were about twice those in summer, and concentration levels varied between fine and excellent. The concentrations of total water-soluble inorganic ions were also higher in winter than in summer, with SO42-, NO3-, and NH4+ being the dominant species and well correlated with each other. NH4+ in PM2.5 mostly existed in the form of (NH4)2SO4 and NH4NO3 in both summer and winter. There was strong secondary oxidation of SO2 and NO2. The sulfate oxidizing rate (SOR) was higher in summer than in winter, while the nitrate oxidizing rate (NOR) showed the opposite trend. The ratio of anions to cations in both summer and winter were less than one, suggesting that PM2.5 were slightly alkaline. The ISORROPIA-Ⅱ mode showed that acidity in winter was stronger than in summer. Concentations of OC and EC were both higher in winter than in summer. The ratios of OC to EC and WSOC to OC and estimated concentrations of secondary organic carbon (SOC) showed that secondary pollution was more serious in winter than in summer. Principal component analysis(PCA)indicated that the major sources contributing to inorganic ions were secondary oxidation and biomass burning in summer, and coal combustion and secondary pollutants formed by chemical oxidation of precursors emitted from coal combustion in winter.

[Seasonal Variation and Sources of Dicarboxylic Acids and Related Compounds in PM10 from Mt. Huangshan].

To identify the seasonal variation of dicarboxylic acids and related compounds in PM10 from Mt. Huangshan. PM10samples were collected during the summer and winter of 2015, which were then analyzed for dicarboxylic acids, ketocarboxylic acids, and α-dicarbonyls. The results showed that oxalic acid(HOOC-COOH, C2) was the dominant species in the summer and winter months, followed by malonic acid(HOOC-CH2-COOH, C3), and succinic acid[HOOC-(CH2)2-COOH, C4], being consistent with that in other high-altitude regions. Most of the diacids were more abundant in the summer months than in the winter months, while adipic acid(C6) and phahalic acid(Ph) were twice lower in the summer months, suggesting significant impact of anthropogenic pollution on the wintertime alpine atmosphere. Moreover, as major precursors of C2, glyoxal(Gly) and methylglyoxal(mGly) were also lower in the summer months than in the winter months, which were opposite to those of the diacids, indicating that the mountain troposphere was more oxidative in the summer months than in the winter months. Principal component analysis(PCA) further revealed that the wintertime SOA in the Mt. Huangshan troposphere mostly originated from the anthropogenic pollutants from long-distance transport. Conversely, the summertime SOA mostly originated from the further oxidation of the mountainous biogenic sources. The AIM(Aerosol Inorganic Model) calculation results showed that the aqueous-phase C2 production was the primary mechanism of C2 formation in ambient aerosol and was driven by acid-catalyzed oxidation in summer.

[Variations in depth and chemistry of groundwater in interval of water delivery at the lower Tarim River].

Variations in groundwater depth and groundwater chemistry influenced by ecological water delivery in the lower Tarim River result in ecological changes. Based on the monitoring data during March, 2007 to September, 2009, the changes of both depths and chemistry of groundwater were studied. It is found that the depth of groundwater at the upper section of lower reaches increased, the major ions, such as Cl-, Na+, showed an increased change. The variations in groundwater depth in groundwater at middle section of lower Tarim River increased, and the concentrations of the major ions showed an opposite trend after the 11th water delivery. At lower section, the depths of groundwater decreased from August, 2008 till September, 2009. At the same time, the major ions in groundwater increased gradually. The groundwater depth and groundwater chemistry far away from the watercourse had a complex change.

[Correlationships between the coverage of vegetation and the quality of groundwater in the lower reaches of the Tarim River].

The variations vegetation coverage is the result of conjunct effects of inner and outer energy of the earth, however, the human activity always makes the coverage of vegetation change a lot. Based on the monitoring data of chemistry of groundwater and the coverage of vegetation from 2002 to 2007 in the lower reaches of Tarim River, relations between vegetation coverage and groundwater chemistry were studied. It is found that vegetation coverage at Sector A was more than 80%, and decreased from sector to sector, the coverage of Sector I was less than 10%. At the same sector, samples near to water source owned high coverage index, and samples far away from the river had low coverage index. The variations of pH in groundwater expressed similar regulation to vegetation coverage, that is, Sectors near the water source had higher pH index comparing than those far away. Regression between groundwater quality and vegetation coverage disclosed that the coverage of Populus euphratica climbed up along with increase of pH in groundwater, change of Tamarix ramosissima coverage expressed an opposite trend to the Populus euphratica with the same environmental factors. This phenomenon can interpret spatial distribution of Populus euphratica and Tamarix ramosissima in lower reaches of the Tarim River.

Influence of intermittent water releases on groundwater chemistry at the lower reaches of the Tarim River, China.

Based on the data of the depths and the chemical properties of groundwater, salinity in the soil profile, and the basic information on each delivery of water collected from the years 2000 to 2006, the varied character of groundwater chemistry and related factors were studied. The results confirmed the three stages of the variations in groundwater chemistry influenced by the intermittent water deliveries. The factors that had close relations to the variations in groundwater chemistry were the distances of monitoring wells from the water channel, the depths of the groundwater, water flux in watercourse, and the salinities in soils. The relations between chemical variation and groundwater depths indicated that the water quality was the best with the groundwater varying from 5 to 6 m. In addition, the constructive species in the study area can survive well with the depth of groundwater varying from 5 to 6 m, so the rational depth of groundwater in the lower reaches of the Tarim River should be 5 m or so. The redistribution of salts in the soil profile and its relations to the chemical properties and depths of groundwater revealed the linear water delivery at present combining with surface water supply in proper sections would promote water quality optimized and speed up the pace of ecological restoration in the study area.

[Three stages of the groundwater chemical properties reacting on the intermittent water deliveries in lower Tarim River, China].

Based on the monitored data of groundwater chemical properties and groundwater depth influenced by five intermittent water deliveries in the lower reaches of the Tarim River, the regulation of groundwater chemistry varying was analysed, the variations in groundwater chemical properties unfolded a clear three-stages changing character under the influence of water deliveries: the initial stage--concentrations of major ions and total dissolved solids (TDS) increasing; the intermediate stage-the concentrations decreasing; the late stage--the chemical properties increasing once more. The variation of groundwater chemistry resulted from many factors, such as the salinities in soil profile, the quality of transported water, the distance from watercourse, the amount and the season of the delivery. However, "salts coming with the water flow, and leaving with it" is the main reason that led to the increase and decrease of chemical properties at first stage and second stage, and with the uprising water level, more and more salinities in soil profile dissolved into ground water and the severe evaporation resulted the concentrations of major ions and TDS increase at late stage. Furthermore, the variations of groundwater chemistry at the intermission of water deliveries have close relationship to the three stages. It should be pointed out that the mode of water transport in surface scope is infeasible due to the climate characteristics of the lower reaches of the Tarim River.

[Analysis of carbon flux of soil and its related factors from Tamarix spp. community in the middle and lower reaches of Tarim River].

This study utilized LI-8100 automated soil CO2 flux system to monitor the day change of carbon flux of soil from Tamarix spp. community in the middle and lower reaches of Tarim River. The influence of temperature, groundwater, and soil water on Carbon flux of soil were analyzed. The study show that the curves of day change of soil respiration have a simple peak value, but the maximum flux normally appear until 12 o'clock noon to 16 o'clock differently. Because of influence of cloud cover and wind speed in that time, difference of the day change of carbon flux of soil are obvious. The relations between the soil respiration and underground water, temperature and soil water content in every depth are close; the relations between carbon flux of soil and underground water are extremely prominent, suitable for Cubic model curve. The relations between carbon flux of soil and air temperature and air temperature near the ground surface, ground surface temperature become positively correlated, suitable for Exponent models curves. However, the relations between carbon flux of soil and soil temperature in the 15 cm, 20 cm, 25 cm, 30cm are negatively correlated, suitable for Cubic model curve. At last, this study analyzed the relations between carbon flux of soil and temperature and soil water content by multi- regression, which explain 67% of the changes in carbon flux of soil.

Degradation of Populus euphratica community in the lower reaches of the Tarim River, Xinjiang, China.

To investigate the relationships between the degradation of plant community and groundwater level in the lower reaches of the Tarim River, nine monitored sections were set along the main stream, where there had been no runoff for nearly 30 years. The characteristics of plant communities were analyzed. It was found that the coverage of trees gradually decreased along the groundwater depth gradient, while the coverage of shrubs slightly increased rather than decreased at first and then gradually decreased, and the coverage of herbs steadily decreased at the beginning and then quickly decreased. The species diversity and species richness of both herbs and woody plants showed obvious degrading trends, while the variations in species evenness were slight. The degrading sequences of species were related to their physiological and ecological characteristics, especially their sensitivity to changes of groundwater table. The herbs with shallow roots first degenerated or disappeared when the groundwater table fell, and then did the deep-rooted herbs, and finally the trees and shrubs with strong tolerance to drought degenerated. The Populus euphratica communities showed typical degrading characteristics, namely the dominant species Populus euphratica remained its dominant status during the degradation. Overall, the existence of strongly tolerant-drought species was the obvious indication of plant species degradation; while simplification of community structure and the decrease of species richness were the obvious indication of plant community degradation.