Alkaline Components Research Articles

Monitoring Method of Steel Reinforcement Corrosion Rate in Concrete

Steel reinforcement concrete is one of the most widely used composite materials in architectural and civil engineering. The alkaline of concrete makes steel passive state, so the steel bars in conrete are kept in anti-corroded phase. Carbon dioxide in atmosphere, however, chemically reacts to the alkaline components in long term, and the passive state of steel is missing. Steel corrosion in concrete is not visible but it may cause decaying buildings or civil construction. The author developed the electrochemical measurement method of monitoring steel corrosion rate in concrete. With the measurement method, the author measured the variety of corrosion rates of steel reinforcement in several atmospheres, such as indoors, outdoors, in-water, underground, and so on. In this paper, found and analyzed mechanisms of steel corrosion in those atmospheres are mainly shown. For an interesting result, the most corroded sample is not the sample exposed outdoor, nor exposed in water, but the sample exposed in wet room. This may cause the diffusion balance of oxygen and water in concrete.

Superface energy of several construction materials

Inverse gas chromatography at infinite dilution was used to characterize the surface of different construction materials (marble, sandstone, granite and brick). Surface energy can be divided into two components: dispersive and polar or acid-base. The highest dispersive energy value was found for sandstone, while the values for the other three materials were all very similar. The lower dispersive energy variation exhibited by sandstone with temperature changes is an indication that substances interact equally well with its surface at any temperature. All the materials were found to be amphoteric, with both acid and alkaline components, although acidity was greater in granite and brick and sandstone and marble had higher alkalinity.

소나무재와 고추나무대재 합성에 관한 연구

The development of Korean glaze originated from the development of ash glazes. Ash not only has strong solubility but also can shows the glaze a variety of different colors according to what the glaze has in it as the main component. In addition, it gives a feeling of lucidness and softness. For these reasons, there are a lot of needs for ash and many potters want to take advantage of ashes as glaze. But natural ashes have not been widely used as glaze primarily because it is relatively hard to find or manufacture. Considering the difficulty of finding or manufacturing natural ashes, this study aims to formulate synthetic ash which not only is available to the potters in general but also has the same characteristics as the natural ashes. To achieve this aim, this study examines the characteristics of the pine tree ash, the main component of the glaze of celadon porcelains, and the red pepper stem ash, the main component of the brown glaze, both of which have been used by the Korean traditional potters. In this study, the alkaline component of the glaze. A important ingredient when the ashes are synthesized, was supplied by mixing of Na₂CO₃, Chungju limestone and rice straw ash. Furthermore, the synthetic ash, when it shows no change of pH in its composition rate of 6:2:2, was found to be usable as the most stable material. In conclusion, the formula which frits some raw materials-Na₂CO₃, Chungju limestone and rice straw ash-can duplicate the synthetic ash which is simila to the natural ash.

Chemical Characteristics of Rain Water at an Urban Site of South Western Turkey

In this study, chemical composition of the rain water in Mugla was investigated from February to April 2002. Rain water samples were obtained from Mugla, a small city in south western Turkey. The Yatagan Power Plant is located 30 km northwest of Mugla city. The values of pH and the concentrations of major ions (Ca2+, Na+, K+, SO4(2-), NO3-, NH4+) in the rainwater samples were analyzed. The pH varied from 4.5 to 7.7 with an average of 6.9 which was in alkaline range considering 5.6 as the neutral pH of cloud water with atmospheric CO2 equilibrium. In the total 30 rain events, only two events were observed in acidic range (< 5.6) which occurred after continuous rains. The equivalent concentration of components followed the order: Ca2+ > SO4(2-) > NH4 + > NO3- > Na+ > K+ > H+. The volume-weighted mean (VWM) of the measured ionic sum is 371.62 microeq/l. The ratio of between sum cations and sum anions (Sigma cations /Sigma anions) is 1.52 microeq/l. The alkaline components (Ca2+, Na+, K+) contribute 52%, NH4 + 8%, whereas, the contribution from the acidic components is relatively small (40%). The low concentrations of H+ found in rainwater samples from Mugla suggest that an important portion of H2SO4 and HNO3 have been neutralized by alkaline particles in the atmosphere. The dust-rich local and surrounding limestone environment might have caused the high concentration of Ca2+ in Mugla area. The relatively high concentration of NH4+ observed at Mugla is suspected to be due to surrounding agricultural. The results obtained in this study are compared with those other studies conducted at various places in the world.

Chemical characterization of dew at a regional representative site of North-Central India

Dew and rainwater samples were collected during winter and monsoon periods in 1997–1998 at Rampur, India, a semiarid site with minimal anthropogenic activities. The study revealed that the decreasing order of ionic concentration in dew is Ca 2+ > SO 4 2− > Cl − > Mg 2+ > NH 4 + > Na + > NO 3 − > K + > HCO − 3 > HCOO − > CH 3COO −, while the range of pH was between 6.0 and 7.7 with a volume weighted mean pH value of 6.8. Rainwater pH varied from 5.9 and 7.4 with volume weighted mean pH of 6.6. The percentage contribution of alkaline components (Ca 2+, Mg 2+, Na + and K +) was 43.9% and NH 4 + 11.1%, while the contribution from acidic components was 45%. Similarly in rainwater the percentage contributions of alkaline, NH 4 + and acidic components were 40.4%, 14.4% and 45.2%, respectively. The difference between the sum of cations and the sum of anions in dew was 233.8 μeq l − 1 , while in rainwater it was 27.8 μeq l − 1 and their ratio was 1.2 in both dew and rainwater. A comparison of the ratios of Cl −/Ca 2+, SO 4 2−/Ca 2+, Mg 2+/Ca 2+, Na +/Ca 2+ and NO 3 −/Ca 2+ in dew with soil indicated that 63 to 96 percentile samples in dew correspond to ratios in soil. Statistically significant correlation between Ca 2+, Mg 2+, K +, NO 3 −, SO 4 2−, HCOO − and CH 3COO − in dew indicate a significant contribution of NO 3 −, SO 4 2−, HCOO − and CH 3COO − from soil or they are associated with Ca 2+, Mg 2+ and K + after neutralization. At the present site, in dew, NH 4 + is 6 times, Ca 2+ and Mg 2+ more than 7 times, K + and Na + greater than 10 times and Cl −, NO 3 −, and SO 4 2− are more than 9 times higher than those of rainwater. The steps governing dew composition are: (i) formation on dry deposition solids, (ii) dissolution of the soluble portion of the dry deposition by dew water, and (iii) sorption of gaseous NH 3, formate and acetate into dew water.

Different immersion periods and aqueous solutions effects upon the corrosion resistance of zinc and aluminium specimens

Several metallic materials form spontaneously an oxide film at the surface when is exposed in a corrosive environment. It is well known that the type of corrosive media may develop different results at the material corrosion resistance. The aim of the present paper is to investigate the influence of immersion periods and different solutions upon the corrosion resistance of pure Zn and Al specimens presenting different grain morphologies. The specimens were monitored for several periods in a 3 % NaCl solution at room temperature. Tests were also performed with variations of the 3 % NaCl solution modified by additions of acid and alkaline components. Both the electrochemical impedance spectroscopy (EIS) and polarization methods were applied.

Field Measurements of Aerosol Particle Dry Deposition on Tropical Foliage at an Urban Site

This paper presents dry deposition of major ions on tropical foliage (leaves of Ashok (Polyalthia longifolia) and Cassia (Cassia siamea)) at St. John's, Agra, an urban site of tropical India on nonrainy, nondewy, and nonfoggy days. The deposition flux was higher on Cassia leaf than Ashok leaf probably due to a rougher surface as shown by scanning electron microscopy. Dry deposition of cations varies from 0.46 to 12.16 mg m(-2) day(-1) while anions vary from 0.04 to 3.24 mg m(-2) day(-1). The percentage contribution of alkaline components is greater than that of acidic components, indicating the alkaline nature of dry deposition. Two-way analysis of variance results reveal significant seasonal variation only for K+, SO4(2-), and F-; however, values varied season to season for Na+, Ca2+, Mg2+, Cl-, NO3-, and NH4+ also. The large seasonal variation in deposition flux may be due to meteorological conditions, diameter of particles, and variation in atmospheric level. SO42- and NO3- show significant correlation, indicating their origin from similar sources while significant correlation between Ca2+ and Mg2+ implies their origin from soil. Poor correlation between Ca2+ and SO4(2-), Ca2+ and NO3-, and Mg2+ and SO4(2-) indicates that in addition to soil other sources also contribute to dry deposition. Low dry deposition fluxes of SO2- and NO3- compared to Ca2+ and Mg2+ may be due to low mass medium diameters of SO4(2-) and NO3- and may be due to uptake through the stomatal pores abundant on leaf surfaces. Factor analysis was employed to identify the sources. F-, Cl, SO4(2-), NO3-, and K+ are grouped together in the first factor, indicating their probable contribution from combustion, Ca2+, Mg2+, and NH4+ are grouped in factor II, which may be attributed to road dust and soil, and factor III includes mainly Na+ and F-, probably contributed from brick-kiln industries. Atmospheric concentrations of F-, Cl-, NOs-, SO4(2-), Na+, K+, Ca2+, Mg2+, and NH4+ were found to be 0.38, 2.28, 1.31, 2.74, 0.44, 0.59, 1.21, 1.2, and 2.29 microg m(-3), respectively.

加湿および添加物混合による石炭灰の固化防止方法の検討

The aim of this study is to prevent the hardening of coal ash during transportation from power plants and storage. In order to prevent the coal ash from hardening, humidification and mixing with additives were applied.As a result, (1) humidification of coal ash at 40°C with air of 50-90%RH, the hardenability of coal ash greatly decreased because sulfur trioxide on the surface of the coal ash reacted with alkaline components such as calcium carbonate by humidification, (2) miximg coal ash with lime stone is the most effective method in reducing the hardenability because it reacts with the sulfur trioxide. The addition of 1-10% lime stone is necessary to prevent hardening.

CLEANING MILKING SYSTEMS USING ELECTROLYZED OXIDIZING WATER

Electrolyzed oxidizing (EO) water is a novel cleaning and disinfecting agent, produced by separating a weak sodium chloride solution into alkaline and acidic components. A pilot-scale pipeline milking system was soiled using raw milk inoculated with common microorganisms. The milking system was then washed with alkaline EO water followed by acidic EO water. After cleaning, the effectiveness of the EO water treatment was evaluated by ATP bioluminescence and microbiological analysis. A 10 min wash with 60°C alkaline EO water followed by a 10 min wash with 60°C acid EO water successfully removed all detectable bacteria and ATP from the non-porous milk contact surfaces. Shorter treatment times (5 and 7.5 min) with EO water were also evaluated, along with a control treatment using conventional dairy cleaning chemicals. There were no significant differences between the 10 min and 7.5 min EO water treatments and the conventional treatment. In a longer-term soiling-washing simulation, only the 7.5 min EO water treatment was evaluated after ten soiling and cleaning cycles, and it was

The influence of NaOH on the stability of paraffinic crude oil emulsion

The alkaline–surfactant–polymer flooding using sodium hydroxide as the alkali component to enhance oil recovery at the on shore oil fields at Daqing in China has brought new problems for the oil industry. Even though, the reservoir contained paraffinic crude oil, the alkali added formed stable water-in-crude oil emulsion and de-emulsification process was necessary to separate oil and water. The problems related in the enhanced oil recovery process using the alkaline–surfactant–polymer flooding technique in the Daqing oil field have been investigated in the laboratory using fractions of Daqing crude oil. The oil was separated into asphaltene and aliphatic fractions and then used in an additive free jet oil to form model oils. The emulsion stability of each of the water-in-model oil emulsions formed between water or 0.6% sodium hydroxide solution and model oil was investigated. The interfacial properties such as interfacial tension and interfacial pressure of the systems were also measured. These in combination with the chemical nature of the fractions were used to get insight into the problem related to the ASP flooding technique using sodium hydroxide as the alkaline component. The study reveals that the sodium hydroxide solution reacts with fatty acids in the aliphatic fraction of the crude oil and/or with the fatty acids formed from the slow oxidation of long chain hydrocarbons, and form soap like interfacially active components. These accumulate at the crude oil–water interface and contribute to the stability of the oil/water emulsion.

Modeling of leaching from cementitious materials used in underground environment

The purpose of this research is to evaluate the long-term durability of engineered barrier materials used in underground radioactive waste disposal facilities. Radioactive waste repositories are constructed in crystalline rocks, sedimentary rocks, or clay, which are natural barrier materials, using bentonite and/or cementitious materials as additional engineered barriers in those natural barriers. These engineered barriers are required to inhibit leakage of radionuclides for a long period of more than 1000 or 10,000 years. This necessitates the actual evaluation of long-term durability and quantitative evaluation of the interactions of each of these barrier materials. Cementitious materials are considered to come in contact with underground water or bentonite and release alkali components, which may degrade their performance. Furthermore, there is apprehension that the properties of bentonite may be altered due to the effect of alkaline components included in cementitious materials. In view of the above, the estimation of changes with time of various components that leach out of cementitious materials is considered to be important for evaluating the long-term performance of engineered barriers. The authors firstly carried out leaching experiments considering temperature effects to construct a solubility equilibrium model of cement hydrate. Next, leaching of calcium from concrete was modeled using this solubility model and an advection–diffusion model. Furthermore, the degradation due to leaching of actual structures, from 34 to 104 years old, was studied, and it was observed that a degradation of 100 mm maximum occurs over a period of 100 years. The calculated results of the proposed model showed very good agreement with the results of studies on actual structures. Finally, the effects of various factors on the degradation rate were evaluated numerically using this model. In addition, a simple evaluation of the degradation of bentonite was also performed.

Cement content influence in rebar corrosion in carbonated mortars

The cement hydration products protect the concrete rebars of the reinforced concrete due to the production of Ca(OH) 2 , NaOH, and KOH that, upon dissolving in the concrete s aqueous phase, generate a pH above 12.5. However, reinforced concrete structures are exposed to pollutant gases, such as, CO 2 which upon penetrating the concrete, reacts with the alkaline components, consequently reducing the pH of the aqueous phase causing the loss of passivity by the rebar and as a consequence its corrosion when there is the presence of humidity and oxygen. The objective of the current paper is the analysis of the alkaline reserve influence, measured by the cement content, in the corrosion of rebars employing the polarization resistance technique for determining the corrosion intensity. Results for corrosion intensity of rebars embedded in prismatic mortar test specimens are produced with three cement content levels, with equal water/cement ratio. Cylindrical test specimens were also used for verification of the capillary absorption and the porosity by means of mercury porosymetry The results show that the initiation period is shorter and the corrosion intensity of the rebars is higher when the cement content is lower However, there is also an alteration in the microstructure upon altering the cement content, and far this reason one cannot conclude that the alkaline reserve alone is responsible for these results.

Characterization of airborne and bulk particulate from iron and steel manufacturing facilities.

Characterization of airborne and bulk particulate material from iron and steel manufacturing facilities, commonly referred to as kish, indicated graphite flakes and graphite flakes associated with spherical iron oxide particles were unique particle characteristics useful in identifying particle emissions from iron and steel manufacturing. Characterization of airborne particulate material collected in receptor areas was consistent with multiple atmospheric release events of kish particles from the local iron and steel facilities into neighboring residential areas. Kish particles deposited in nearby residential areas included an abundance of graphite flakes, tens of micrometers to millimeters in size, and spherical iron oxide particles, submicrometer to tens of micrometers in size. Bulk kish from local iron and steel facilities contained an abundance of similar particles. Approximately 60% of blast furnace kish by volume consisted of spherical iron oxide particles in the respirable size range. Basic oxygen furnace kish contained percent levels of strongly alkaline components such as calcium hydroxide. In addition, concentrations of respirable Mn in airborne particulate in residential areas and at local iron and steel facilities were approximately 1.6 and 53 times the inhalation reference concentration of 0.05 microg/m3 for chronic inhalation exposure of Mn, respectively. Thus, airborne release of kish may pose potential respirable particulate, corrosive, or toxic hazards for human health and/or a corrosive hazard for property and the environment.

Developments in the use of image analysis for the assessment of oriental noodle appearance and colour

Canada Prairie Spring Red (8 cultivars) and Canada Prairie Spring White (10 cultivars) wheat were milled on an Allis Chalmers mill to yield straight grade flours of a constant 74% extraction rate. These flours were used to prepare both fresh yellow alkaline and white salted noodles. The appearance of the noodles prepared from the white and red seed coated wheats was measured using two scanner based image analysis systems differing in their means of colour correction. Significant differences in the number of detectable specks ( p<0.0001) within both alkaline and white salted noodles were observed between noodles prepared from either white and red seed coated wheat flour using either system. Speck size and gray level density parameter combinations were found to influence the red, green and blue, RGB, values of the detected specks. Unique differences in both alkaline and white salted noodle colour components were observed using the inexpensive, colour calibrated colour system for noodles prepared from either white or red seed coated wheat flour. These differences were detectable at both 2 and 24 h after production offering noodle manufacturer’s an unique, inexpensive means of monitoring their noodle’s appearance.

Ternary nucleation of inorganic acids, ammonia, and water

Homogeneous ternary nucleation rates of water, ammonia (NH3), and inorganic acids are calculated from classical nucleation theory at various combinations of temperature and ambient vapor concentrations. Mixtures with sulfuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl), and methane sulfonic acid (CH3SO3H or MSA) are considered. The results are compared to assess the relative importance of different nucleation routes. Vapors with an acid and an alkaline (ammonia) component are shown to nucleate more readily than vapors having two acid species. Much lower concentrations of H2SO4 than HNO3 or HCl are required to reach the same nucleation rate at similar vapor concentrations of H2O and NH3. Nucleation rates in H2O–H2SO4–HNO3 and H2O–H2SO4–MSA vapors are close to the limit of H2O–H2SO4 nucleation, even at high concentrations of MSA and HNO3. The results suggest that H2O–H2SO4–NH3 nucleation is the foremost ternary nucleation route in the atmosphere.

Air pollution by concrete dust from the Great Hanshin Earthquake.

Air pollution in the areas affected by the Great Hanshin Earthquake (Hyogo, Japan) of 17 Jan. 1995 was quite serious. We performed three investigations of dust. In the first investigation, we measured the total suspended particulate (TSP) concentration in the greatly damaged areas, located around the Sannomiya Station where a few hundred thousand people walked by during the daytime of 3 February. The maximum concentration at five points reached 150 microg/m3. In the second investigation, eight samples, which were classified into three groups (concrete, mortar, and soil dusts) as sources, were analyzed elementally by X-ray fluorescence. The elements found in concrete dust (Ca and S) were similar to those found in mortar dust. These differed from those found in soil dust (Ti, Fe, and Zr). The elements found in soil dust were important from the viewpoint of heavy metal contamination. In the third investigation, the alkalinity of concrete dust was observed by dissolution. This solution was equivalent to pH 11 to 12 and electrical conductivity 20 to 30 microS/m. We suspect that the alkaline component in the dust from debris in all the devastated areas was approximately comparable with the alkaline solution by which the acid rain falling over the Hanshin district of Osaka Megalopolis in one year could be neutralized into water of pH 7.0.

An evaluation of the thermodynamic equilibrium assumption for fine particulate composition: Nitrate and ammonium during the 1999 Atlanta Supersite Experiment

Data obtained during the 1999 Atlanta Supersite Experiment are used to test the validity of the assumption of thermodynamic equilibrium between fine particulate (PM2.5) nitrate (NO3−) and ammonium (NH4+) and gas‐phase nitric acid (HNO3(g)) and ammonia (NH3(g)). Equilibrium is tested by first calculating the equilibrium concentrations of HNO3(g) and NH3(g) implied by the PM2.5 inorganic composition (i.e, Na+, NH4+, Cl−, NO3−, and SO42−), temperature, and relative humidity observed at the site. These calculated equilibrium concentrations are then compared to the corresponding observed gas‐phase concentrations. The observed PM2.5 composition is based on the 5‐min averaged measurements of the Georgia Tech PILS [Weber et al., 2001], while the observed HNO3(g) and NH3(g) concentrations are based on the measurements of Edgerton et al. [2000a] and Slanina et al. [2001], respectively. The equilibrium gas‐phase concentrations are calculated using the ISORROPIA model of Nenes et al. [1998]. Out of the entire Atlanta Supersite database, we were able to identify 272 five‐minute intervals with overlapping measurements of PM2.5 composition, HNO3(g) and NH3(g). Initial calculations using these 272 data points suggest an absence of thermodynamic equilibrium with the calculated equilibrium NH3(g) generally less than its observed concentration and predicted HNO3(g) generally greater than the observed concentration. However, relatively small downward adjustments in the measured PM2.5 SO42− (or apparent acidity) bring the calculated and measured NH3(g) and HNO3(g) into agreement. Moreover, with the exception of 31 of the 272 data points with either anomalously low observed concentrations of SO42− or NH3(g), there is a close correspondence between the SO42− (or acidity) correction needed for HNO3 and that needed for NH3 (slope of 1.04, intercept of ∼0, and r2 = 0.96). The average relative corrections required for equilibrium with HNO3 and NH3 are −14.1% and −13.7%, respectively; significantly larger than the estimated uncertainty arising from random errors in the measurement. One interpretation of our results is that thermodynamic equilibrium does in fact apply to the inorganic PM2.5 composition during the Atlanta Supersite Experiment and either (1) the PM2.5 SO42− concentration measured by the PILS was systematically overestimated by ∼15% or (2) the PM2.5 PILS systematically underestimated the concentration of the alkaline components by ∼15%; and/or 3. The ISORROPIA model systematically underestimated the pH of the PM2.5 encountered during the experiment.

The Activity of the Peroxidase System in the Course of Stress-Induced CAM Development

The activity of the peroxidase system in Mesembryanthemum crystallinum L. plants in relation to the shift from C3 to CAM photosynthesis was studied. In detached leaves of the fourth and fifth stories treated with NaCl (0.3 M), a rapid (after 30 min) transient induction of the ionically bound peroxidase (the first maximum) was observed followed by a second weak increase in the enzyme activity (90 min after salt treatment). In the leaves of intact plants, which received a longer treatment with NaCl, a two-phase change in the enzyme activity was also observed. It was most pronounced at the early stages of the NaCl-induced plant shift from C3 to CAM photosynthesis. In this case, in both detached and intact leaves of juvenile plants, the activity of soluble peroxidase was at a low steady-state level. The situation changed dramatically when M. crystallinum plants transitioned to the reproductive developmental phase and photosynthesis switched from C3 to CAM. The time dependence of the activities of both peroxidase types, the soluble ones in particular, was characterized by marked diurnal oscillations (light–dark), which coincided with the fluctuations of the total titratable acidity. In this case, the activity of the soluble enzyme was several orders of magnitude higher than the activity of the ionically bound peroxidase, even though the optimum pH for both isoforms was similar (pH 5.0). Three acid isoforms of soluble peroxidases, which operated more actively when the cytoplasm had a higher acidity, were distinguished by isoelectrofocusing. Their activity increased under salinity. Alkaline and neutral components were predominant in more than 30 molecular forms of the soluble peroxidase detected. We concluded that the operation of the peroxidase system changed substantially when plants shifted from the juvenile to the reproductive state and switched from C3 to CAM photosynthesis: the activity of stress-induced ionically bound peroxidase was drastically inhibited with a concurrent increase in the activity of soluble peroxidase and a change in the spectrum of its molecular forms.

Mechanism of bioleaching of coal fly ash by Thiobacillus thiooxidans

Bioleaching of aluminum and iron from coal fly ash (CFA) by Thiobacillus thiooxidans ( T. thiooxidans) bacteria is considered. The interactions between bacteria, metabolic products, CFA particles, and leaching products were studied. It is demonstrated that bacterial growth and the amount of metals leached from the CFA are coupled through biological and chemical interactions, which involve the various components in this system. Bioleaching experiments were performed batch wise by suspending up to 10% (w/v) CFA in T. thiooxidans growth medium containing cell inoculum for a typical 3 week period of time. Samples were taken periodically from leached suspensions and relevant parameters including metals’ concentrations, cell counts, pH and extracellular polymeric substances (EPS) were determined. The results show that under the same conditions, similar leaching levels are obtained by sulfuric acid and bioleaching of CFA, and the contribution of other metabolites is insignificant. CFA inhibits the growth rate through two major effects. The first is due to the alkaline components released by the CFA that cause a rise in the pH, and a corresponding delay in growth. The second is attributed to the random attachment of the bacteria to both the sulfur particles (the energy source) and the barren CFA particles, resulting in a so-called “dilution effect” of the sulfur particles, and an inhibition of the initial growth rate. However, after an adaptation period of the bacteria the subsequent growth rate, the maximal cell concentration and minimal pH were similar to those obtained in the control experiment, irrespective of CFA content. Enhanced excretion of EPS was observed in the presence of CFA as well as in calcium and barium enriched growth media. It is presumed that the mechanism of EPS production is related to the presence of the particulate solid phase.

Trends of pollution in rain over East Germany caused by changing emissions

Large changes in emissions also cause a significant change in pollutant concentrations in rain water. The influence of these changes on pollutant concentrations in rain water and wet deposition were investigated in different regions and time periods from 1983 to 1999 in East Germany. Initially, this period is characterized by large emissions of SO2(about 5400 kt a−1), NOx(about 750 kt a−1), and dust (about 2000 kt a−1) at the end of the 1980s. After the reunification of Germany in 1990 and restructuring of industry and agriculture, emissions drastically decreased. For example, from 1990 to 1998 in Saxony emissions of SO2, NOx and dust decreased by 84, 44 and 97%, respectively. Alkaline components also strongly decreased through efficient dust removal, while no desulphurization was used in flue gases of power and heating plants. As a consequence, the mean acidity of precipitation strongly rose by a factor of three from before 1990 up to 1995 (the mean pH value in 1995 was about 3.9, with minimum values down to 3.6). In 1996 desulphurization techniques were established in power plants and resulted in an increase of pH values to the level in the period from 1983 to 1989/1990. The results for ionic composition (Cl−, NO3−, SO42−, Na+, NH4+, K+, Ca2+, and Mg2+, the pH value (acidity), and conductivity) are based on precipitation samples collected in periods > 4 h. The data were classified with backward trajectories and entry sectors which are characterized by similar emissions and/or geographical regions.