Chemical Composition Of Precipitation Research Articles

Chemical composition of precipitation and snow cover in the Primorsky krai

The chemical composition ofprecipitation from May 2012 to March 2013 and snow cover in the south of the Primorsky krai are studied. The measured parameters are pH and the concentration of principal ions, dissolved organic carbon, silicon, and metals in the samples of precipitation and snow cover taken in Vladivostok and in the background area of the Sikhote-Alin mountain range. Data from Primorskaya, Ternei, and Sadgorod stations are presented for comparison.

Depletion zones and intergranular corrosion of superaustenitic stainless steel Alloy 926

Superaustenitic stainless steel Alloy 926 was evaluated after different isothermal annealing and thermomechanical heat treatments. The impact of two different quenching and tempering processes on sensitization was determined. Since Alloy 926 contains large amounts of molybdenum and chromium, precipitation of various intermetallic phases is strongly favored. Based on SEM and EF‐TEM, it was found that the size as well as the extent of elemental depletion zones is in good agreement with the degree of sensitization (DOS), independently of the applied corrosion test. Elemental depletion zones of two isothermally annealed conditions were obtained quantitatively and related to those of thermo‐mechanically rolled samples. Comparison of both annealed conditions revealed the different operating principles of Streicher test and DL‐EPR‐test. In consequence, morphology, distribution, and chemical composition of precipitates have a considerable impact on corrosion test results. Different microstructural parameters and their relevance on prediction of corrosion properties are pointed out and discussed accurately.

Fly ash-slag interaction during alkaline activation: Influence of activators on phase assemblage and microstructure formation

In this work, the influence of activator on the interaction mechanisms between slag and low-calcium fly ash (FA-F) during alkaline activation was investigated. In particular, the evolution of phase assemblage and microstructure of alkali-activated binary slag and FA-F paste was monitored by means of X-ray diffraction with Rietveld analysis, scanning electron microscopy, and energy-dispersive spectroscopy (SEM/EDS). The results show that the nature of amorphous gels and type of crystalline phases formed are dependent on sample age, initial slag to FA-F ratio, and activator type and dosage. The interaction between FA-F and slag during alkaline activation or geopolymerization is primary demonstrated as: (1) modified nanostructure (e.g. crystallology and lattice parameters) and chemical composition of precipitates, (2) depressing or triggering the formation of some crystalline phases, and (3) spatial heterogeneity of composition in microstructure. The activator is chemically incorporated into interactions between slag and FA-F, and likely affects the dissolution and reaction kinetics.

Chemical compositions of precipitation at three non-urban sites of Hebei Province, North China: Influence of terrestrial sources on ionic composition

Studies on precipitation chemistry were carried out from April to October in 2008 at three non-urban sites in North China. A total of 122 rainwater samples were collected, and all the samples were analyzed for pH, EC and major ions (F−, Cl−, NO3−, SO42−, K+, Na+, Ca2+, Mg2+, and NH4+). The predominant ions in the precipitation were SO42−, NO3− and Ca2+ at all sampling sites. The low VWM pH value (5.29) reflected the increasing air pollution in this region. But there was still more than 60% of the total precipitation had a pH value higher than 6.0, indicating the considerable neutralizing effects of alkaline aerosols in northern China. The volume-weighted mean (VWM) concentrations of major ions and pH values showed obvious seasonal differences, the precipitation had higher pH values and VWM concentrations of major ions in dry season. This is mainly attributed to the different sources of air masses in different seasons and the dilution effect on suspended particles. According to the equivalent ratio of [nssCa2++NH4+]/[nssSO42−+NO3−] and the results of neutralization factors, the strong acid neutralization was mainly brought about by Ca2+ followed by NH4+ and Mg2+. Using Na as an indicator of marine origin, the proportions of sea salt and non-sea-salt were estimated from elemental ratios. Combining with the results of correlation analysis, the main acidic ions (SO42− and NO3−) and NH4+ were mainly derived from anthropogenic activities, and Ca2+ and Mg2+ mostly originated from terrestrial sources. In general, the results reflect that terrestrial source was an important source of major cations in rainwater and strongly influenced the precipitation chemistry, especially in dry season.

Isotopic and chemical composition of precipitation in Riyadh, Saudi Arabia

Only limited data on the isotopic and chemical composition of Riyadh rain are currently available. In this study, we complement these data by analyzing integral samples covering 28 precipitation events between 2009 and 2013. Results of stable isotope analyses are used to establish a Local Meteoric Water Line: δ2H=5.22(±0.38)·δ18O+14.8(±0.9) ‰. Moisture source-related isotopic fingerprints are masked by the continental effect, the altitude effect, sub-cloud evaporation, and moisture recycling. The study of one event for intra-storm variability revealed strong isotopic depletion due to rainout and Rayleigh distillation processes, thus highlighting the general need for integral samples. Tritium analyses of grab samples from 12 events yielded concentrations between 2.8 and 6.4tritium units (TU), which are close to the natural background of a few TU.Major ion concentrations and ratios indicate that solutes are predominantly derived from atmospheric dust originating from limestone outcrops and sabkha deposits. The latter play a role with respect to the elevated Cl−and Na+ contents, but are probably also responsible for the SO42−and a part of the Ca2+ found in Riyadh rain. Observed intra- and inter-storm variabilities of major ion levels necessitate the collection of integral samples and the calculation of precipitation-weighted means, respectively.The obtained isotopic signatures and the precipitation-weighted mean Cl−concentration (9.5mgL−1) may be useful in groundwater assessments, e.g., for the identification of modern recharge and quantification thereof by means of the Chloride Mass Balance method.

Corrosion Behaviour of Al–4Mg–1Cu (wt%) Microalloyed with Si and Ag

The microstructure, hardness, and corrosion behavior of Al–4Mg–1Cu–0.5Si and Al–4Mg–1Cu–0.5Si–0.4Ag (wt%) following various aging times is investigated. Potentiodynamic polarisation and immersion tests reveal an apparent insensitivity in corrosion rates for the alloys studied with aging, along with a higher pitting corrosion resistance for the Ag containing alloy. The addition of Ag to the base Al–4Mg–1Cu–0.5Si composition increases the age hardening response and corrosion performance by modifying the morphology, size, and chemical composition of precipitates (from S‐phase to Z‐phase).

Climatic and environmental characteristics of Moscow megalopolis according to the data of the Moscow State University Meteorological Observatory over 60 years

Analyzed are the results of meteorological and environmental measurements performed over the 60-year period (1954–2013) at the Meteorological Observatory of Lomonosov Moscow State University. The significant positive temperature trend (0.04°C/year for 1954–2013) was obtained; it increased up to 0.07°C/year in 1976–2012. Considered are the features of seasonal variations of different atmospheric characteristics. Discussed are the type and causes of low-frequency changes in meteorological parameters, radiation balance components, radiation in different spectral ranges, and chemical composition of precipitation. Demonstrated are possible mechanisms of the more significant increase observed in air temperature in Moscow as compared with that in Central Federal District and their connection with the greenhouse effect in the urban atmosphere.

Natural versus anthropogenic influences on the chemical composition of bulk precipitation in the southern Apennines, Italy: A case study of the town of Potenza

This paper presents new data on the chemical composition of precipitation in a selected area of the southern Apennines of Italy; these data are used to assess natural and anthropogenic contributions to the precipitation. The town of Potenza was used as a representative urban site, and the major and minor element (Na+, K+, Ca2+, Mg2+, NH4+, Cl−, NO3−, SO42−, and Li+, NO2−, F−, Br−, PO43−) and trace element (Zn, Fe, Al, Sr, Mn, Ba, Cu, Cr, V, As, Pb, Ni, and Cd) concentrations of bulk precipitation from three different sampling sites within the study area were determined between June 2011 and May 2012. The majority of the collected rainwater has pH values higher than 5.6. The composition of this rainwater was dominated by Ca2+ the element with the highest total volume-weighted mean concentration (TVWA), followed by Cl−, SO42−, Na+, NO3− , K+, Mg2+, and NH4+. The TVWA of the trace metals decreased in the order Zn>Fe>Al>Ba>Sr>Mn>Pb>Cu>As. Neutralising factor (NFXi) values indicate that Ca2+ is the dominant neutralising cation within this rainwater, with lower contribution from NH4+ and Mg2+. The precipitation analysed during this study has a negligible marine influence as determined using Cl− concentrations as a proxy for the abundance of sea salts. Precipitation Fi values (marine fraction of element i) indicate that Na+ is the element with the highest seawater component, and we found partial marine contributions for the SO42−and Mg2+ concentrations within this rainwater. Enrichment factors (EF) of selected elements were calculated to identify the sources of non-crustal elements: K+, Mg2+, Fe, and Ca2+ are the only elements dominantly sourced from the crust, whereas Mn and Ba have highly variable EF values (10–100) suggesting that a small proportion of these elements was derived from anthropogenic sources in addition to a more significant crustal contribution. Sr, Cu, Pb, Zn, and As are highly enriched with respect to average crustal compositions, confirming that the concentrations of these elements within precipitation are significantly controlled by human activities.

Physicochemical modeling of composition of the organic matter in precipitation over the White Sea Islands

Carried out is a broadened study of the chemical composition of precipitation obtained by the direct analytic determination using the physicochemical modeling (the Selektor software package) within the framework of the Al-B-Br-Ar-He-Ne-C-Ca-Cl-F-K-Mg-Mn-N-Na-P-S-Si-Sr-Cu-Zn-H-O-e system with the addition of thermodynamic parameters of low-molecular alifatic acids. The results of the modeling enable the supposition that the composition of precipitation can be determined at the metastable state in the case of weak complex formation of metals and dominance of simple salts of low-molecular organic acids (formates and acetates). The analysis of the obtained information indicates the urgency of taking account of the organic matter impact for predicting the migration activity of pollutants and the determination of the critical load on marine ecosystems.

Chemical Composition of Precipitation and River Water in Southern Iceland: Effects of Eyjafjallajökull Volcanic Eruptions and Geothermal Power Plants.

Samples of precipitation have been collected and analysed from four sampling stations in southern Iceland. Sea-salt in the precipitation has the same elemental ratios as in seawater and its concentration decreases with distance from the shore. The sampling station at Mjóanes, at Thingvallavatn Lake, is located around 100km west of Eyjafjallajökull and during and after its eruption in 2010, the concentration of fluoride in precipitation increased from 10-20μg/l to 90μg/l and the annual average concentration elevated from 11μg/l to 28μg/l. From 1980 to 1998, pH of rainwater at Írafoss increased due to emissions reductions of anthropogenic sulphur. Since 1998, pH of the precipitation has decreased again at Írafoss. Similar pH changes are seen in Mjóanes, which is close to Írafoss, but not in other sampling stations further away. River water samples collected in the vicinity of the rainwater samplers, from the spring fed river Sog have elevated non-SO4 sulphur concentration from 2005-2010 and decreased δ34S from 2005-2007. Írafoss and Mjóanes are located approximately 12-20km away from two geothermal power plants, Nesjavellir- and Hellisheidi power plants that emit large quantities of CO2 and H2S, among other gases, to the atmosphere. The data presented here suggest that geothermal power production can cause local environmental effects, like rainwater acidification and increases in dissolved sulphur in rivers in the vicinity of the power plants.

Impact of transboundary and natural factors on chemical composition of precipitation in the Far East of Russia

Variability of precipitation components in the Far East of Russia is analyzed using the monitoring of their chemical composition. It is demonstrated that the increase in precipitation acidity in the region is caused by the growing concentrations of sulfates and nitrates in precipitation. Transboundary transport determines about 60% of the concentration of sulfates and nitrates in the precipitation over the south of the region. Impact of marine aerosol on the chemical composition of precipitation is significant at some coastal stations only.

Chemical characteristics of precipitation and wet deposition of major ions in Liaozhong County of Liaoning Province, Northeast China

The chemical characteristics of precipitation were analyzed based on the chemical composition of principal ionic within acid rain (from February 2007 to January 2008) of Liaozhong Meteorological Station located in Malong Village in Liaozhong County of Northeast China, meteorological conditions on the corresponding period ground, and variation of several air pollutants concentration. The results indicated that: (1) The precipitation average pH value of all samples was 4.76; the frequency of acid rain during the observation period was 70.7%; the frequency was 82.8% in summer and autumn. (2) In the chemical composition of precipitation, the primary anions were SO42- and NO3-; the primary cations were NH4+ and Ca2+. (3) All concentration of anions was higher in summer and winter, but relatively low in spring and autumn. This showed that the relationship between regional rainfall acidification and pollution was not significant. (4) Rainwater acidity and nearly floor gaseous pollution concentration were differe...

Kinetics of Precipitation Behavior of Second Phase Particles in Ferritic Ti-Mo Microalloyed Steel

Two types of stress relaxation tests were carried out to investigate the incubation time for incipient precipitation of Ti(C,N) in deformed austenite and (Ti, Mo)C in ferrite of ferritic Ti-Mo microalloyed steel. The size distribution, amount and chemical composition of precipitates were obtained by using physicochemical phase analysis, and calculated according to thermodynamics and kinetics. The experimental results demonstrated that the incubation time was reduced with increasing Ti content, and prolonged with the addition of Mo. After 30% deformation at 850 °C, the nucleation of strain-induced Ti(C,N) was a relatively slow process. On the other hand, the temperature where the nucleation rate of (Ti, Mo)C in ferrite was the highest descended first and then ascended with increasing Ti content, and so did the temperature where the incubation time was the shortest. The key point is that the temperature of steel containing about 0. 09% Ti is the lowest. The mass fraction of MC-type particles with size smaller than 10 nm in steel containing 0. 09% Ti and 0. 2% Mo reached 73. 7%. The size distributions of precipitates in steel containing 0. 09% Ti were relatively concentrated compared with that in steel containing 0. 07% Ti.

Chemical composition of precipitation at coastal and marine sampling sites in Mexico

Chemical characteristics of wet precipitation were measured in Acapulco, Cancun, Tapachula, Puerto Morelos and Tropical Pacific Ocean; from August 1999 to October 2001. The samples were analyzed for pH, Na+, K+, Ca2+, Mg2+, NH4 +, SO4 2-, NO3 - and Cl-. Ionic abundance revealed a significant variation, however, the most abundant ions were sodium, chloride and magnesium in all sites. pH values observed were within the normal pH value considered for rainwater, and agree with that reported by other authors in marine and coastal sites; sea-salt aerosol contributed with most of Na+, Cl- and Mg2+, whereas, a significant proportion of K+ and Ca2+ originated in particles from soil; finally sulfate excess concentration was in agreement with the background hemispheric values. In the other hand, in Puerto Morelos, during sampling campaign performed at the end of the mid-summer drought, NO3 - levels were the highest and also higher than SO4 2- concentrations, exceeding background level; and pH values observed were low. Excluding, Puerto Morelos, where other sources influenced the rain chemistry composition; all remaining sampling sites were clearly influenced by marine aerosol, showing ionic concentrations typical of sites with a minimal anthropogenic influence, and therefore, their ionic concentrations can be considered as representative of background values for this region.

Analysis of wet acid deposition in Macau

Records of precipitation in Macau are collected from three local monitoring stations from 1993 to 2003. Chemical compositions of precipitation are analyzed to reveal the causes of wet deposition in Macau. The review of annual rainfall volumes and the volume weighted annual pH values over this period show that there is a slight spatial variation in the rainfall volume and the entire area of Macau is subjected to acidic precipitation. The monthly rainfall volumes and the monthly concentrations of five ionic species including H+, nssSO4 2-, NO3 -, nssCa2+, and NH4 + are analyzed statistically and their distributions are found to have positive skewness and kurtosis. The monthly rainfall volume is found to follow the Gamma distribution which is consistent with the findings in other regions of Asia. In addition, the monthly concentration of each ionic species is found to follow the lognormal distribution. Nonetheless, the distribution of each ionic species exhibits spatial variability across the stations. Therefore, it is suspected that the sources of wet acid deposition in different parts of Macau are different and further correlation analysis on the values of [H+], nss[Ca2+], [NH4 +], nss[SO4 2-], and [NO3 -] of the precipitation is carried out. Correlation analysis on the monthly concentrations of the ionic species shows that the linear correlation between [H+] and nss[SO4 2-] is higher than the linear correlation between [H+] and [NO3 -] at two of the monitoring stations. The result indicates that sulfur dioxide could be a relatively important contributor of acid wet deposition with respect to nitrogen dioxide in Macau as suggested by previous preliminary studies. In addition, the eleven-year averaged ratio of [SO4 2-]/[NO3 -] at Ka-Ho being 5.06 reinforces this conclusion. However, the dominant sources contributing to the acidity in two regions of Macau, namely Fortaleza and Taipa Grande respectively are still unknown since the anions do not show any significant positive correlation to the hydrogen ion at these two stations. It is only ascertained that the dominant source of acidity in Ka Ho can be originated from the emission of SO2 as the relatively strong linear correlation of [H+] and nss[SO4 2-] indicates that the free acidity is mainly contributed from the sulfuric acid. For the other stations, the wet acid deposition is then believed to be controlled by local sources of sulfuric acid, nitric acid and some other acids that are not accounted for in the present study. Finally, the monthly concentrations of the ionic species are found to be negatively correlated with the monthly rainfall volume at three monitoring stations. Hence, it is concluded that longer rainfall duration would reduce the acidity in rainwater.

Chemical Denudation in a Geoecosystem in Acid Immision Conditions / Denudacja Chemiczna W Geoekosystemie W Warunkach Kwaśnej Imisji

Abstract There is an analysis of the physico-chemical properties and the chemical composition of precipitation in a forest geoecosystem in acid immision conditions. The data used in the analysis was collected between 2000 and 2010. In that period, a drop in the immision scale of S-SO2 in the atmospheric air had been observed, which consequently was one of the reasons for a drop in the precipitation acidity. The conclusion was that rainwater, after penetrating treetops and trunks, undergoes a significant transformation whose intensity depends on species composition of the forest stand. Statistically relevant differences were found in coniferous stands, in which a substantial drop in pH was noted, in addition to an increase in the load of components accumulated in the soil in relation to atmospheric precipitation. The calculated indicators of the eco-chemical state of waters (Ma%) have revealed that throughfall waters in coniferous stands and fir and beech stemflow contain significant amounts of aluminium, manganese, iron and hydrogen ions in the sum of cations. Also the indicator of acid-neutralizing capacity (ANCaq) shows that these waters are more enriched with sulfate, nitrate and chloride ions than bulk precipitation. The recorded variation eventuates from processes related to dry and humid deposition, as well as ion-exchange processes occurring within the stand. The obtained results point to an intensification of chemical denudation within the trunks, triggering disadvantageous changes in both biotic and abiotic part of the ecosystem. The effects of the increased inflow of souring agents to the soil through stemflow are significant acidification of the top mineral soil horizon and an increase in the hydrolytic acidity.

Three-decade changes in chemical composition of precipitation in Guangzhou city, southern China: has precipitation recovered from acidification following sulphur dioxide emission control?

We examined if precipitation had recovered from acidification in Guangzhou, the third biggest city in China, and if sulphur deposition in precipitation had decreased, and to what extent if yes, following abatement strategies in sulphur dioxide (SO2) emission and energy use implemented since 2001. SO2 emissions were decreasing steadily since 2001, but a marked recovery of precipitation acidity occurred only since 2005; precipitation pH values decreased from 4.65 in 2001 to 4.34 in 2005 and then increased to 5.08 in 2010, while in the same period acid rain (pH<5.6) frequency increased from 70% to 81% and then decreased to 48%. During this period, the change in pH value and sulphate concentration more reflected the patterns of SO2 emission at provincial and national scales than at the local scale, suggesting that precipitation chemical composition was largely controlled by the emissions of pollutants from surrounding areas of the study city. Since 2001, sulphate deposition in precipitation decreased significantly (by 40%) but nitrogen deposition remained unaltered. More importantly, the current sulphur (43 kg S ha−1 yr−1 as sulphate) and nitrogen depositions (35 kg N ha−1 yr−1 as ammonium plus nitrate in 2010) were still among the highest in China. These results highlight the fact that ambient sulphur and nitrogen deposition still pose a threat to the health of both terrestrial and aquatic ecosystems. Precipitation may become more acidified in the future because the deposition of alkaline dusts containing calcium is also likely to decrease with stricter SO2 emission control policy and reduced construction activities. Additionally, we recommend that a reduction of emissions of nitrogen and chlorine bearing pollutants is urgently required for complete control on acid deposition.

Trend in chemical composition of precipitation during 2005–2009 at a rural station of Bhubaneswar, eastern India

Precipitation samples collected during 2005- 2009 from a rural forest station of Bhubaneswar were ana- lyzed for their chemical composition. The samples were collected through a wet-only (WO) collector and two bulk (B1 and B2) collectors. The ions were evenly balanced indicating good data quality. The overall pH of rainwater was slightly acidic and ~47% of all rain events during the period were acidic (pH<5.6). Multilinear regression analy- sis showed relation between the free acidity (H + ) and other components in rainwater. Enrichment factors (EF) of the major components with respect to their sources such as marine and crustal were calculated. Maximum EF was ob- served for NO3 � for both marine and crustal sources for all the three collectors. Source apportionments were also car- ried for the ions. Trend analysis showed continuous increase in most of the ions over years during the study period driven by anthropogenic emissions. Statistical/factorial analysis established correlation among different ions.

Microstructure and properties of 13Cr5Ni1Mo0.025Nb0.09V0.06N super martensitic stainless steel

Abstract The morphological microstructure, the density and dispersion of high angle boundaries, morphology and micro chemical composition of precipitates and the volume fraction of retained austenite of a commercial super martensitic stainless steel (SMSS) normalized and tempered at various temperatures were characterized by optical microscope, scanning electron microscope (SEM), electron backscattered diffraction (EBSD), transmission electron microscope (TEM) and X-ray diffraction (XRD) in the light of equilibrium phase diagram of the alloy calculated using Thermo-Calc software. The mechanical properties and pitting corrosion resistance were determined to correlate with microstructures. Two kinds of morphology of precipitate were observed in tempered commercial super martensitic stainless. Besides the globular Nb and V rich carbo-nitride precipitates, rod-like Cr rich nitrides were formed due to excess N content. While high density of high angle boundaries and precipitates contribute to strength properties, the dislocation softening of the matrix and retained austenite from tempering restore the ductility and impact toughness properties. The poor resistance to pitting corrosion is attributed to the occurrence of Cr rich precipitates. It is demonstrated that by lowering the nitrogen content and adding niobium, the Cr rich precipitates can be suppressed and the mechanical properties and resistance to pitting corrosion can be significantly improved.

Long Term Trend in the Chemical Composition of Precipitation at Komae, Tokyo

Long Term Trend in the Chemical Composition of Precipitation at Komae, Tokyo