Manabu Igawa

Effect of structural variation within cationic azo-surfactant upon photoresponsive function in aqueous solution

The cationic azo-surfactants possessing different spacers and tail alkyl chain lengths have been synthesized by azocoupling ofp-alkylaniline orop-ethoxyaniline with phenol, followed by alkylation and quaternalization with dibromoalkane and trimethylamine, respectively. These surfactants showed a good solubility in water. A reversibletrans-cis isomerization of the azosurfactants by photoirradiation was assessed by UV-Vis absorption spectra. Due to a difference in HLB between thetrans- andcis-surfactants, the observed critical micelle concentration (CMC) values and the electric conductivity of the surfactant solution at above the CMC were significantly affected by the photoinducedtrans-cis isomerization. The azo-surfactants bearing moderate alkyl chain lengths such as surfactants 6 (R2=C2H4, R3=C4H9) and 9 (R2=C4H8, R3=C2H5) were found to be effective to achieve large CMC changes (3.6 mmol/L for 6 and 5.9 mmol/L for 9) by UV-light irradiation. The replacement of the tail chain species also affected the photoresponsive function. The surfactant 12, possessingp-ethoxy group as the tail chain, was found to form a stable micelle aggregation as compared with the structurally related surfactant 10 having ethyl unit as its tail group, but it exhibited a large CMC change (5.3 mmol/L) by UV-light irradiation.

Deterioration of concrete structures by acid deposition - An assessment of the role of rainwater on deterioration by laboratory and field exposure experiments using mortar specimens

Abstract Deterioration of concrete structures caused by acid deposition was investigated by laboratory and field exposure of portland cement mortar specimens to acid deposition. Laboratory exposure experiment showed that the dissolved amount of calcium hydrates, which were the major components in mortar, increased with the increase in the acidity of simulated acid rain solution and the decrease in the flow rate. There was little difference in their amount among different temperature treatments after each exposure to the solution with the same acidity, namely left at room temperature, heated at 70°C, and cooled at −2°C. The neutralization progressed more deeply under the heated and cooled condition and was accelerated by even acid rain with pH 4.7 during a long period (90 exposure cycles, which correspond to the rainfall amount of 15 years in Japan). A field exposure experiment for two years indicated that the carbonation of calcium hydrates and the formation of other corrosion products such as chloride, nitrate, and sulfate were limited to the surface of mortar specimens. The neutralization progressed more deeply in mortar specimens sheltered from rainwater than in those washed by rainwater.

Fogwater chemistry at a mountainside in Japan

Fogwater had been observed for 4.5 years from July 1988 to December 1992 at the midslope of Mt. Oyama at the southwest of the Kanto plains. Rainwater, aerosol, and gases had been also collected and analyzed at the fog sampling station to investigate the characteristics and acidification mechanism of fogwater. The pH of fogwater ranged from 2.61 to 7.00 and the fog with very low pH values and high ion and aldehyde concentrations were frequently observed in spring and summer. The fogwater at the site was acidified primarily by nitric acid gas absorbed in fogwater and the acid fraction of most of the fogwater ranged from 0.3 to 0.01. The acidity of fogwater is controlled by the amount of the acidic pollutants in the atmosphere, the concentrations of the neutralizing components for the acidic fogwater, primarily NH3 gas concentration, the liquid water content in air, and the distance between the sampling station and the lowest altitude of the fog in upslope fog.

Elevational patterns of acid deposition into a forest and nitrogen saturation on Mt. Oyama, Japan

Virgin fir trees have been dying on Mt. Oyama, which is located in the southwestern part of Kanto Plain, although the frequency of death seems to be reducing recently. We report elevational patterns of acid deposition in precipitation and throughfall under fir and cedar canopies and nitrogen saturation in the forest ecosystem on Mt. Oyama. The deposition fluxes of major inorganic ions in precipitation were nearly constant regardless of elevation except for hydrogen and ammonium ions, whereas the deposition fluxes of all major inorganic ions in throughfall among cedar increased. The 5-year average of annual nitrate deposition in precipitation from 1994 to 1998 showed 19.3 – 23.5 kg ha−1 yr−1 (annual inorganic total N deposition: 9.6 – 10.7 kgN ha−1 yr−1) at four sites ranging in elevation from 500 to 1252 m, whereas the deposition in both cedar and fir throughfall was over 6 times greater than that in precipitation. The average soil surface nitrate concentration in 1998 was 140 µg g−1 (the range: 21.1 – 429 µg g−1, n=80) and the 7-year average of nitrate concentration in stream water from 1992 to 1998 was 4.81 mg L−1 (the range: 2.38 – 20.6 mg L−1, n=317). Our results indicate that nitrogen saturation is occurring in the forest ecosystem because of high N deposition, probably via acid fog, on Mt. Oyama.

Effect of simulated acid fog on needles of fir seedlings

Abstract Fir seedlings ( Abies firma ) were treated with simulated acid fog from September 1992 to April 1995. The simulated acid fog was at pH 3 and consisted of 1 mM nitric acid, 1 mM sodium chloride, and 1 mM ammonium sulfate. In 1993 spring, needles of the seedlings treated with the simulated acid fog became greener than those of the control, which were treated with pH 5 fog water of one hundredfold diluted solution of pH 3 fog water. However, from June 1993 in the acid-fog-treated seedlings, the needles shed, and the growth in height declined. Many buds with their bearing sprouts died in 1993, and few twig tips put forth new sprouts in the spring of 1994. Other symptoms also developed because of the treatment with the simulated acid fog: the water loss from the needles increased and the needles became susceptible to water stress, the weight per area of the needles decreased, and chlorophyll concentration increased. The results were observational in nature and the data were generated from plants exposed to the atmosphere in Yokohama so that there is a possibility of interaction with other pollutants. The long-term treatment with simulated acid fog at pH 3 induced a decline of fir seedling growth and general well-being, although the data warrant further study of the effects of chronic exposure of acid fog on plant growth.

Fog Water Chemistry at Mt. Oyama and its Dominant Factors

We have observed acid fog in Mt. Oyama since 1988. Fog events occur frequently in Mt. Oyama; 47% of the time the mountain top is covered with fog. The pH of fog is lower than that of rain collected at the fog sampling station by about 1 unit and the lowest pH was 1.95. We have also collected gas and aerosol components at the station and observed fog events by a video camera from the mountain base, where there is an air pollution monitoring station. The air quality at the fog sampling station was affected by not only the air quality at the base but also the wind direction, valley or mountain wind. It is ascertained by using back trajectory analyses that polluted air masses are transported to the base from the Kanto plains or other big urban areas, Osaka and Nagoya. When the base is polluted, the relative humidity increases, and the valley wind blows, acid fog is formed at the mountainside. In the acid fog, nitrate ion is the most abundant anion. Nitrate ion concentration correlates well with hydrogen ion concentration. The annual mean total ion concentration has not changed much since 1988, but the concentration ratio of nitrate ion to sulfate ion has increased in recent years. The nitric acid gas concentration in the station is comparable to that in urban areas, while other gas concentrations are much lower.

Severe leaching of calcium ions from fir needles caused by acid fog

We have measured the components of the throughfall under fir trees (Abies firma) in the field around Mt. Oyama, where the forest appears to be declining, for the period 1994-1998. Exposure experiments of a simulated acid fog to fir twigs were performed under field conditions. There was a similarity between the acid response in the field and that in the laboratory. In both studies, the severe leaching of calcium ions from the needle surface was caused by exposure to acid fog. We also applied acid fog to fir seedlings over 1 year and observed a decrease in the growth of the seedlings due to this application in the dormant season. These results suggest that the severe leaching of calcium ions due to acid fog may cause the deficiency of calcium and be responsible for the decline of the fir trees.

Permeation of complexed metal ions through a hydrophobic membrane

Abstract Selective concentration of a heavy metal complex with acetylacetone (acac) through a hydrophobic polystyrene membrane was carried out under a pressure gradient. A chelate forming heavy metal was selectively concentrated about 2 fold by this method. When using a coating membrane with a high water flux, the permeabilities increased with increasing complex fraction in the aqueous solution, while using a membrane with a low water flux, a bulky complex was not highly concentrated because of steric hindrance. The complex partitioned on the membrane surface was transported and concentrated under a pressure gradient and a linear relationship was found to exist between permeabilities and partition coefficients. It will be possible to concentrate hydrophobic organic solutes by this method, for acac was concentrated when the Cu—acac complex was formed. As the permeabilities increased with decreasing pressure and membrane compaction was strong for a coating membrane, it seems effective to permeate at a low pressure.

Facilitated transport of carbohydrates via complexation with borate ion fixed on an anion-exchange membrane

Abstract The transport of sugar was facilitated via complexation with borate ion fixed on an anion-exchange membrane. The sugar was highly distributed on the membrane and was transported by the carrier-relay mechanism. The flux across the borate ion type membrane increased with increasing concentration but became constant at a lower flux than across a chloride ion type membrane. Sugars were selectively transported and the permeability of the sugar depends on its distribution in the membrane.

Leaching of cell wall components caused by acid deposition on fir needles and trees

Virgin fir forests have been declining since the 1960s at Mt. Oyama, which is located at the eastern edge of the Tanzawa Mountains and adjacent to the Kanto plain in Japan. An acid fog frequently occurs in the mountains. We collected throughfall and stemflow under fir trees and rainfall every week during January-December 2004 at Mt. Oyama to clarify the influence of acid fog on the decline of fir (Abies firma) needles. In relation to throughfall and stemflow, D-mannose, D-galactose, and D-glucose are the major neutral sugar components; only D-glucose is a major component of rainfall. The correlation coefficient between the total neutral sugars and uronic acid (as D-galacturonic acid), which is a key component of the cross-linking between pectic polysaccharides, was high except for rainfall. The leached amount of calcium ion, neutral sugars, uronic acid, and boron is related to the nitrate ion concentration in throughfall. Results of a laboratory exposure experiment using artificial fog water simulating the average composition of fog water observed at Mt. Oyama (simulated acid fog: SAF) on the fir seedling needles also shows a large leaching of these components from the cell walls of fir needles. The leaching amount increased concomitantly with decreasing pH of the SAF solution. We also observed that a dimeric rhamnogalacturonan II-borate complex (dRG-II-B) that exists in the cell wall as pectic polysaccharide was converted to monomeric RG-II (mRG-II) by the leaching of calcium ion and boron. Results not only of field observations but also those of laboratory experiments indicate a large effect of acid depositions on fir needles.