Climate Risks and Their Impact on Agriculture and Forests in Switzerland

There is growing evidence that, as a result of global climate change, some of the most severe weather events could become more frequent in Europe over the next 50 to 100 years. The paper aims to (i) describe observed trends and scenarios for summer heat waves, windstorms and heavy precipitation, based on results from simulations with global circulation models, regional climate models, and other downscaling procedures, and (ii) discuss potential impacts on agricultural systems and forests in Switzerland. Trends and scenarios project more frequent heavy precipitation during winter corresponding, for example, to a three-fold increase in the exceedance of today's 15-year extreme values by the end of the 21st century. This increases the risk of large-scale flooding and loss of topsoil due to erosion. In contrast, constraints in agricultural practice due to waterlogged soils may become less in a warmer climate. In summer, the most remarkable trend is a decrease in the frequency of wet days, and shorter return times of heat waves and droughts. This increases the risk of losses of crop yield and forage quality. In forests, the more frequent occurrence of dry years may accelerate the replacement of sensitive tree species and reduce carbon stocks, and the projected slight increase in the frequency of extreme storms by the end of the century could increase the risk of windthrow. Some possible measures to maintain goods and services of agricultural and forest ecosystems are mentioned, but it is suggested that more frequent extremes may have more severe consequences than progressive changes in means. In order to effectively decrease the risk for social and economic impacts, long-term adaptive strategies in agriculture and silviculture, investments for prevention, and new insurance concepts seem necessary.     

The Precision of "Rapid" Rock Analysis And the Homogeneity of New USGS Standard Rock Samples

Additional analytical data for the thirteen oxides usually determined in a rock analysis by wet methods and estimates and, conclusions from the analysis of variance are presented for the eight new USGS rock standards STM-1, RGM-1, QLO-1, SCo-1, MAG-1, SDC-1, BHVO-1 and SGR-1. The "single-solution" method of sample dissolution, and the "rapid methods" described by Shapiro were used. Three bottles of each standard were analyzed in duplicate, providing six replicate analyses of each sample. Relative standard deviations ranged from 0. 00 to 202 %, with only 12 of the possible 104 sample-oxide combinations exceeding 10 %. Most deviations exceeding 10 % occur with oxides at very low concentrations or with the determi-nation, of H₂O⁺ and CO₂, all of which often yield poor precision. These data indicate that the rapid wet chemical methods, except possibly for H₂O⁺ and CO₂, or when very low concentrations are present, can be considered reliable. Of the 104 F-ratios calculated during the analysis of variance for sample-oxide combinations, only eight equal or exceed the tabled value of 9. 55 for F_0.95 (d. f. 2, 3). These data strongly support the conclusion that the contents of the bottles may be considered homogeneous for most oxides determined. When our data for an oxide in the several samples are plotted versus similar data in the USGS Prof. Paper 840 by several methods, the plots generally show good agreement for most sample-oxide combinations, but approximately thirty of the 104 show substantial differences, with no obvious correlation between the various methods used or the nature or magnitude of the differences.     

Mass transfer at the air/water interface: Mass accommodation coefficients of SO2, HNO3, NO2 and NH3

We present here experimental determinations of mass accommodation coefficients using a low pressure tube reactor in which monodispersed droplets, generated by a vibrating orifice, are brought into contact with known amounts of trace gases. The uptake of the gases and the accommodation coefficient are determined by chemical analysis of the aqueous phase.We report in this article measurements of _exp=(6.0±0.8)×10^–2 at 298 K and with a total pressure of 38 Torr for SO₂, (5.0±1.0)×10^–2 at 297 K and total pressure of 52 Torr for HNO₃, (1.5±0.6)×10^–3 at 298 K and total pressure of 50 Torr for NO₂, (2.4±1.0)×10^–2 at 290 K and total pressure of 70 Torr for NH₃.These values are corrected for mass transport limitations in the gas phase leading to =(1.3±0.1)×10^–1 (298 K) for SO₂, (1.1±0.1)×10^–1 (298 K) for HNO₃, (9.7±0.9)×10^–2 (290 K) for NH₃, (1.5±0.8)×10^–3 (298 K) for NO₂ but this last value should not be considered as the true value of for NO₂ because of possible chemical interferences.Results are discussed in terms of experimental conditions which determine the presence of limitations on the mass transport rates of gaseous species into an aqueous phase, which permits the correction of the experimental values.     

Long-term earthquake prediction in the Aegean area based on a time and magnitude predictable model

The Aegean and surrounding area (34°N–43°N, 18°E–30°E) is separated into 76 shallow and intermediate depth seismogenic sources. For 74 of these sources intervent times for strong mainshocks have been determined by the use of instrumental and historical data. These times have been used to determine the following empirical relations: $$\begin{gathered} \log T_t = 0.24M_{\min } + 0.25M_p - 0.36\log \dot M_0 + 7.36 \hfill \\ M_f = 1.04M_{\min } - 0.31M_p + 0.28\log \dot M_0 - 4.85 \hfill \\ \end{gathered} $$ whereT ₁ is the interevent time, measured in years,M _min the surface wave magnitude of the smallest mainshock considered,M _p the magnitude of the preceding mainshock,M _f the magnitude of the following mainshock, \(\dot M_0 \) the moment rate in each source per year. A multiple correlation coefficient equal to 0.74 and a standard deviation equal to 0.18 for the first of these relations were calculated. The corresponding quantities for the second of these relations are 0.91 and 0.22. On the basis of the first of these relations and taking into consideration the time of occurence and the magnitude of the last mainshock, the probabilities for the occurrence of mainshocks in each seismogenic source of this region during the decade 1993–2002 are determined. The second of these relations has been used to estimate the magnitude of the expected mainshock.     

Distinct element modeling and analysis of mining-induced subsidence

Summary The influence of rock discontinuities on mining-induced subsidence is addressed in this paper. A two-dimensional rigid block computer model was used to simulate discontinuities within strata overlying a longwall coal mine. Input for the model was available from a previous field study and numerical experiments were performed by varying the simulated joint stiffness, joint roughness, and vertical joint density. A comparison of simulated and measured displacements both within the overburden and on the surface provides insight into the influence of rock discontinuities. For the case in which all contacts had a relatively low stiffness, the maximum simulated subsidence was 293 mm whereas the case involving variable, but higher contact stiffness produced a maximum subsidence of only 73 mm reflecting the influence of increased overall stiffness. By comparison, the maximum measured subsidence was 580 mm. Consequently, the model behaved more stiffly than the actual rock mass but still provided a reliable simulation of block caving and strata separation. A comparison of simulated and observed displacements within the overburden suggests that horizontal discontinuities not included in the rigid block mesh above the zone of caving controlled rock mass compliance.List of Symbols c joint stiffness ratio [dimensionless] - d strata thickness ratio [dimensionless] - e strata modulus ratio [dimensionless] - E _a modulus of stratum a [MPa] - E _b modulus of stratum b [MPa] - E _equiv equivalent rock mass modulus [MPa] - E _u unconfined compression modulus of intact rock [MPa] - F _n contact normal force [N] - h overburden thickness [m] - k _a normal spring stiffness of stratum a [N/m] - k _b normal spring stiffness of stratum b [N/m] - k _equiv equivalent rock mass spring stiffness [N/m] - K _n normal material stiffness of joint [MPa/m] - K _s shear material stiffness of joint [MPa/m] - m mined thickness of coal seam [m] - q _u unconfined compressive strength of intact rock [MPa] - Sh shale - Ss sandstone - Sh/Ss shale/sandstone interbeds - S _max maximum subsidence [m] - SLEX Slope Indicator inclinometer/Sondex extensometer - T _a thickness of stratum a [m] - T _b thickness of stratum b [m] - T _j joint thickness [m] - u _a compression of stratum a [m] - u _b compression of stratum b [m] - u _j compression of joint [m] - u _total total compression of strata and included joint [m] - w width of longwall panel [m] - _n normal stress [MPa]     

Nitrate pollution of groundwater in the alsatian plain (France)—A multidisciplinary study of an agricultural area: The Central Ried of the ill river

The area studied is part of the Ried Central of the Ill river (Middle Alsatian plain in northeastern France). This area is located mainly in the present floodplain of the Ill. The closeness of the water table to the surface results in quasi general soil hydromorphism.The economic constraints of the last two decades led to deep changes in agricultural activities in the study area. These have essentially involved a marked extension of intensive cultivation of grain corn at the expense of grasslands. The study of the influence of this change on the parallel increase in the concentration of nitrate in groundwater is only feasible when a multidisciplinary approach is adopted.The analyses carried out in the field and in the laboratory show that nitrate reduction occurs in gleyed or peaty horizons of hydromorphic soils. The aptitude and efficiency of the permanent ambient vegetation (alluvial forests and grasslands) in retaining nitrate must be emphasized. The amount of nitrate eliminated from the aquifer by rivers fed by this aquifer is considerable. This evacuation of nitrate into the Ill is a fine example of waste and illustrates the absurdity of the economic situation responsible for excessive nitrogen fertilization of farmlands.In determining hazard zones, this study also proposes practical solutions to the problem of nitrate pollution: diminution of land area under cultivation, reintroduction of grasslands, and a more judicious use of nitrogen manure.     

A forward test of the Decelerating–Accelerating Seismic Strain model to western south and central America

Global observations show that strong mainshocks are preceded by decelerating preshocks which occur in the focal (seismogenic) region of the ensuing mainshock and by accelerating preshocks which occur in a broader (critical) region of the mainshock. Predictive properties of these preshocks have been expressed by empirical relations supported by theory and form the Decelerating–Accelerating Seismic Strain (D–AS) model. A respective algorithm has been developed which is used to identify the critical and seismogenic region and estimate (predict) the corresponding ensuing mainshock. In the present work a forward test of this model is performed by attempting intermediate-term prediction of future big (M ≥ 7.7) mainshocks along the western coast of south and central America. Three regions of decelerating shocks and three corresponding regions of accelerating shocks have been identified. The parameters (origin time, magnitude, epicenter coordinates) as well as their uncertainties have been estimated (predicted) for the corresponding probably ensuing three mainshocks. This forward test allows an objective evaluation of the model's ability for an intermediate-term prediction of strong shallow mainshocks.