Hans M. Seip

Structure of cyclohexane determined by two independent gas electron-diffraction investigations

Abstract The results of two independent electron-diffraction investigations of cyclohexane are compared. By averaging the results the following parameters and error limits are obtained: r g (CC) = 1.536±0.002 A, r g (CH) = 1.121±0.004 A, and ∠CCC = 111.4±0.2°.

Co-benefits of climate policy--lessons learned from a study in Shanxi, China

We analyse health benefits and socio-economic costs of CO2-abating options related to coal consumption in Shanxi, China. Emission reductions are estimated for SO2 and particles in addition to CO2. Co-benefits of each option are estimated in terms of how effectively it improves local air quality and thereby reduces health damage from pollution. The population-weighted exposure level for particles and SO2 is estimated using air quality monitoring data, and a simplified methodology is applied to estimate the reduced exposure to the population that may result from implementing the abatement measures. Exposure–response functions from Chinese and international epidemiological studies are used to estimate the ensuing health effects. A method for estimating the impact of chronic PM10 exposure on life expectancy in the affected population is developed and applied. An economic evaluation of the reduced health effect is made by determining unit prices of health impacts based partly on damage costs and partly on the willingness-to-pay approach. Our assessment of CO2-reducing abatement options in Shanxi demonstrates that these measures entail large co-benefits and are highly profitable in a socio-economic sense.

Dissolved organic carbon fractions in soil and stream water during variable hydrological conditions at Birkenes, southern Norway

Spatial and temporal variations in the composition of dissolved organic carbon (DOC) in stream and soil water of the acidified Birkenes catchment were studied during summer and autumn 1990. Hydrophobic and hydrophilic acids were the dominant fractions in the soils (dominated by podzols and peats) and brook, accounting for ∼90% of total DOC. The podzol displayed a vertical gradation of DOC fractions, with hydrophobic acids dominating in the O horizon (∼65%) and hydrophilic acids dominating in the E and B horizons (∼60%). In the bogs, hydrophilic acids were the dominant fraction at all depths. Temporal variations in the relative contributions of the various DOC fractions were most pronounced in the podzol O horizon and the brook during successive autumn rainstorms, and small in the mineral soils and bogs. In the brook, DOC increases at peak discharge were dominated by hydrophilic acids. If stream water was assumed to be a conservative mixture of water from the podzol O and B horizons and from the deeper layers in the bog surrounding the stream, 92% of the variability in the concentration of hydrophobic and hydrophilic acids in the stream could be explained. This mixing analysis suggested that base flow largely originated in the deeper layers of the bogs, while peak flow was primarily made up of B horizon (∼50–65%) and O horizon (∼35–50%) water.

Acid deposition and its effects in China: an overview

Acid rain is an increasing environmental problem in China. At present SO2 emission is about 20–22 million tons. However with a growing number of large power plants the long-range transport of air pollutants is expected to increase. The highest acid deposition is near the emission sources. Wind-blown, alkaline soil dust is important in neutralizing the acidity of the emissions, especially in large parts of northern China. In the south, where alkaline soil dust contributes less to acid neutralization, the annual pH in precipitation was below 4.5 at monitoring stations in several provinces and as low as 4.1 in some urban areas. Total sulfur deposition has been estimated to be about 10 g S m−2 year−1 in heavily exposed areas. Negative effects on forests, including die-back, have been reported for relatively small areas near large cities. Since large, regional surveys have not been carried out, there are large uncertainties about effects on a regional level. The high concentrations of gaseous pollutants, especially within and near the cities, are likely to have severe effects on human health as well as on materials and vegetation. Several field and laboratory studies, as well as computer simulations, indicate that acidification of soil and soil water has occurred in the past few decades. This has probably caused elevated concentrations of toxic aluminum in soil water. At present, the toxic effect of Al is likely to be counteracted by high concentrations of calcium at many places. The Chinese authorities have recognized air pollution and acid rain as serious environmental problems, however, there are difficulties in implementing effective measures to reduce the problems. With respect to ecological effects we lack a comprehensive regional overview of the extent of the acid deposition problem in China. Such information is necessary before effective countermeasures can be developed.

Surface Ozone in China and its Possible Impact on Agricultural Crop Yields

Abstract Emissions of ozone precursors are expected to multiply the next 20 years in China, and the levels of photo-oxidants may increase substantially. Increased surface ozone gives cause for concern regarding the prospects for Chinese agricultural production. We show that crop production may be substantially reduced in the future due to elevated ozone concentrations, and that productivity may already be affected for some crops. However, crop-yield loss estimates obtained by using alternative exposure-response functions vary substantially. Spring wheat, soybean, and corn may be especially vulnerable to future ozone increases, due to a likely concurrence of peak levels of ozone and the growth season of these crops.

Aluminium speciation: comparison of two spectrophotometric analytical methods and observed concentrations in some acidic aquatic systems in Southern Norway

The toxicity of A1 to aquatic biota varies with speciation. Driscoll (1980) has developed a scheme for determining three A1 fractions using the ferron method (Smith, 1971) to detect Al. We have compared the results obtained with Driscolls method with those obtained when pyrocatechol violet is the complexing agent. The agreement is generally satisfactory. The latter method is more sensitive and less influenced by interferences. Results for water samples, mainly from two streams in southern Norway, are discussed. For most samples the labile monomeric Al-fraction dominates, the major species being either A13+ or AIF2+. Possible equilibria between A13+ and some minerals and the temperature changes in these equilibria, are discussed.

Failure of the CNDO/2 method to predict the barriers and conformations in some conjugated systems

Abstract The potential functions for rotation about the CC single bonds in glyoxal, 1,3-butadiene, benzaldehyde, biphenyl, and 2,2′-difluorobiphenyl have been calculated by the CNDO/2 method. The results show that the method is not accurate enought to be used for calculations of barriers or conformations in this kind of molecules.

A Critique of Models for Freshwater and Soil Acidification

Four types of models quantifying effects of acid deposition on freshwaters are reviewed. These include Henriksens empirical model, an adsorption isotherm model, soil-oriented charge balance models (Reuss-Johnson, Birkenes, MAGIC, ILWAS), and the Trickle Down model. Emphasis is on an assessment of critical assumptions; no attempt has been made to run the various models and compare results. The models range from simple to very complex and from empirical to highly process oriented. The various types have all proven useful and there has been a significant convergence concerning key processes. The importance of anion mobility, sulfate adsorption, ion exchange, dissolution of Al bearing minerals and weathering seems to be accepted by most workers. Future model improvement, however, relies to a large extent on further checking against observations.

VARIATIONS IN CONCENTRATIONS OF AQUEOUS ALUMINIUM AND OTHER CHEMICAL SPECIES DURING HYDROLOGICAL EPISODES AT BIRKENES, SOUTHERNMOST NORWAY

Abstract Concentrations of H + , aluminium species, total fluoride, silica, TOC, and major cations and anions were measured in stream- and soil water in the Birkenes catchment during base-flow and high discharge hydrological episodes from 1984 to 1986. Snow and meltwater were also sampled before and during the spring snowmelt seasons. During all the rainfall and snowmelt hydrological events for the five field periods analysed, the H + concentration increased with flow, whereas inorganic monomeric aluminium, Al i (including Al 3+ ), increased with flow only during episodes preceded by relatively low flow periods; during subsequent events Al i remained nearly constant or even decreased. Concentrations of Al i and H + in soil water sampled under saturated conditions were generally stable over time compared to the variations for these species in streamwater. The considerable fluctuations observed for chloride Cl − and sulphate SO 2− 4 concentrations illustrated that displacement of soil water occurred. The results confirm the importance of hydrological factors in determining episodic aluminium response. Large variations in the saturation indices show that equilibrium with either Al(OH) 3 (gibbsite) or Al 2 Si 2 O 5 (OH) 4 (kaolinite, halloysite) cannot control aluminium concentrations in streamwater at Birkenes; the same is true for Al(OH)SO 4 (jurbanite) although the saturation index for this mineral is less variable. Most probably, different controlling mechanisms predominate in the different soil layers, producing different chemical signatures which are picked up in the stream to varying degrees depending on hydrological conditions.

Potential for rotation about C(sp2)-O and C(sp2)-S bonds: electron diffraction results for CH2CH-OCH3 and CH2

Abstract Electron diffraction of gaseous methyl vinyl ether and methyl vinyl sulphide show that both compounds exist as a mixture of two conformers, one of these is the syn form with a planar heavy atom skeleton. For methyl vinyl ether the second conformer may also have a planar skeleton ( anti form), but a gauche form with a torsional angle close to 180° cannot be ruled out. For the sulphide a gauche form is found. Structural parameters are given in Table 2. Ab initio calculations gave energy minima for syn and anti forms for CH 2 CH-OH and for syn and gauche forms for CH 2 CH-SH.