Local versus regional processes: can soil characteristics overcome climate and fire regimes by modifying vegetation trajectories?

We analysed charcoal and pollen from sediments obtained from two lakes in the northwestern mixed‐wood Canadian boreal forest in order to reconstruct fire‐return intervals and vegetation dynamics over the last 8000 years. Sites were selected with contrasting soil properties (mesic versus dry‐sandy soils), allowing an estimation of the potential influence of soils on long‐term vegetation and fire dynamics. The sites likely experienced fewer fires during the period extending from 8000 to 4000 cal. a BP than over the last 4000 years. At both sites, eastern white pine (Pinus strobus) populations were most extensive shortly after deglaciation, with vegetation later shifting towards mixed woodlands with less P. strobus and more extensive Picea and Pinus banksiana populations. This gradual vegetation shift was probably induced by the establishment of colder and moister conditions along with a fire‐regime change. In spite of the parallel long‐term vegetation trajectories, vegetation composition differed between the two sites in both the past and present. Whereas Picea was more abundant at the mesic site, the fire‐adapted P. banksiana populations were more extensive at the sandy‐soil site. These differences in vegetation composition indicate that, in addition to climate changes and fire occurrence, soil properties also influenced vegetation dynamics. A likely increase in fire frequency in the Canadian boreal forest during the 21st century might therefore favour the expansion of these two disturbance‐adapted trees with spatial heterogeneity in the populations due to varying soil types. Copyright © 2012 John Wiley & Sons, Ltd.     

Mesozoic to Cenozoic tectono‐metamorphic history of the South Pamir–Hindu Kush (Chitral,NW Pakistan): Insights from phase equilibria modelling,and garnet–monazite petrochronology

The Karakoram–Hindu Kush–Pamir and adjacent Tibetan plateau belt comprise a series of Gondwana‐derived crustal fragments that successively accreted to the Eurasian margin in the Mesozoic as the result of the progressive Tethys ocean closure. These domains provide unique insights into the thermal and structural history of the Mesozoic to Cenozoic Eurasian plate margin, which are critical to inform the initial boundary conditions (e.g. crustal thickness, structure and thermo‐mechanical properties) for the subsequent development of the large and hot Tibetan–Himalaya orogen, and the associated crustal deformation processes. Using a combination of microstructural analyses, thermobarometry modelling and U–Th–Pb monazite and Lu–Hf garnet geochronology, the study reappraises the metamorphic history of exposed mid‐crustal metapelites in the Chitral region of the South Pamir–Hindu Kush (NW Pakistan). This study also demonstrates that trace elements in monazite (especially Y and Dy), combined with thermodynamical modelling and Lu–Hf garnet dating, provides a powerful integrated toolbox for constraining long‐lived and polyphased tectono‐metamorphic histories in all their spatial and temporal complexity. Rocks from the Chitral region were progressively deformed and metamorphosed at sub‐ and supra‐solidus conditions through at least four distinct episodes from the Mesozoic to the Cenozoic. Rocks were first metamorphosed at ~400–500°C and ~0.3 GPa in the Late Triassic–Early Jurassic (210–185 Ma), likely in response to the accretion of the Karakoram during the Cimmerian orogeny. Pressure and temperature subsequently increased by ~0.3 GPa and 100°C in the Early‐ to Mid Cretaceous (140–80 Ma), coinciding with the intrusion of calcalkaline granitic plutons across the Karakoram and Pamir regions. This event is interpreted as the record of crustal thickening and the development of a proto‐plateau within the Eurasian margin due to a long‐lived episode of slab flattening in an Andean‐type margin. Peak metamorphism was reached in the Late Eocene–Early Oligocene (40–30 Ma) at conditions of 580–600°C and ~0.6 GPa and 700–750°C and 0.7–0.8 GPa for the investigated staurolite schists and sillimanite migmatites respectively. This crustal heating up to moderate anatexis likely resulted in the underthrusting of the Indian plate after a NeoTethyan slab‐break off or to the Tethyan Himalaya–Lhasa microcontinent collision and subsequent oceanic slab flattening. Near‐isothermal decompression/exhumation followed in the Late Oligocene (28–23 Ma) as marked by a pressure decrease in excess of ~0.1 GPa. This event was coeval with the intrusion of the 24 Ma Garam Chasma leucogranite. This rapid exhumation is interpreted to be related to the reactivation of the South Pamir–Karakoram suture zone during the ongoing collision with India. The findings of this study confirm that significant crustal shortening and thickening of the south Eurasian margin occurred during the Mesozoic in an accretionary‐type tectonic setting through successive episodes of terrane accretions and probably slab flattening, transiently increasing the coupling at the plate interface. Moreover, they indicate that the south Eurasian margin was already hot and thickened prior to Cenozoic collision with India, which has important implications for orogen‐scale strain‐accommodation mechanisms.     

Temporal and spatial variation of infiltration in urban green infrastructure

Infiltration is the primary mechanism in green stormwater infrastructure (GSI) systems to reduce the runoff volume from urbanized areas. Soil hydraulic conductivity is most important in influencing GSI infiltration rates. Saturated hydraulic conductivity (Ksat) is a critical parameter for GSI design and post-construction performance. However, Ksat measurement in the field is problematic due to temporal and spatial variability and measurement errors. This review paper focuses on a comparison of methods for in-situ Ksat measurement and the causes of temporal and spatial variations of Ksat within GSI systems. Automated infiltration testing methods, such as the Modified Philip–Dunne (MPD) and SATURO infiltrometers, show promise for efficient Ksat measurements. Soil Ksat values can change over time and substantially vary throughout a GSI, which can be attributed to multiple factors, including but not limited to temperature changes, soil composition and properties, soil compaction level, plant root morphology and distribution, biological and macrofauna activities in the soil, inflow sediment characteristics, quality of infiltrating water, and measurement errors. There is evidence that infiltration rates in vegetated urban GSI systems are sustained given an appropriate GSI design, reasonable concentration of suspended sediments in the inflow runoff, and routine maintenance procedures. These observations indicate that clogging can be counteracted by processes that tend to increase the soil hydraulic conductivity (e.g., plant root and biological activities). This self-sustainability underlines that infiltration-based GSI systems are a reliable long-term stormwater management solution. Recommendations on how to incorporate the temporal changes of Ksat in GSI design and on obtaining a spatially-representative Ksat for the GSI design are presented.     

Probability of Peak Ground Horizontal and Peak Ground Vertical Accelerations at Tehran and Surrounding Areas

The active faults near Tehran are capable of producing Mw magnitudes of 6.62?C7.23; at epicentral distances of 25?km from the active faults, and Mw?=?7.23, the peak ground horizontal acceleration, PGH, is between 386 and 730?cm/s² and peak ground vertical acceleration, PGV, is between 192 and 261?cm/s²; the historic earthquake of the fourth century BC, Mw?=?7.16 produced the highest estimated PGH acceleration in Tehran, between 254 and 479?cm/s² and PGV acceleration between 127 and 173?cm/s². Earthquakes from 1909 to 2008, within 300?km from Tehran, are used for calculation of magnitude frequency relation, and results are applied to estimate PGH and PGV accelerations as a function of magnitudes for a set of fixed epicentral distance and site conditions; also as a function of epicentral distances for a set of fixed magnitudes and site conditions. Poisson??s distribution is used for probability calculation of PGH and PGV accelerations for several exposure times, site conditions and epicentral distances; accelerations with very high probability, near 1, are presented. At an epicentral distance of 10?km and exposure time of 450?years, in the northern part of Tehran, close to Mosha and the Northern Tehran faults, PGH acceleration is 800?C420?cm/s² and PGV is 400?C220?cm/s² with high probability. At an epicentral distance of 25?km and 1,000?years exposure time, PGH is 610?C320?cm/s² and PGV is 310?C160?cm/s² with high probability, where larger values are for soft soil and smaller values are for hard rock.     

塔里木盆地大气降尘变化特征及影响因素分析

利用哈密、塔中与和田沙尘暴观测站2005—2008年大气降尘观测资料,结合铁干里克、民丰等18个大气降尘监测点2007年4月以来的大气降尘、沙尘天气等观测资料,分析了塔里木盆地大气降尘变化特征,同时分析了影响大气降尘浓度变化的主要因素。结果表明：①2005—2008年3站中哈密大气降尘量最少,其次为和田,塔中的大气降尘量最多; 2006年是4 a中降尘量最多年份,其次为2005年,2008年相对较少。②春夏季是大气降尘集中季节,秋季略大于冬季。塔里木盆地中部最高,南部及西南部的站点降尘明显高于盆地的东部和西部。③在沙尘暴季节,无论是5月还是6月,2007年大气降尘量基本上都高于2008年。④2007年5月和6月,除盆地东面的哈密、铁干里克以及西缘的阿拉尔3站外,其他18个站沙尘天气较多。沙尘天气是塔里木盆地大气降尘量高的主要因素,沙尘天气越多,大气降尘量越高。     

古尔班通古特沙漠积雪覆盖、沙尘天气特征及其相互关系

利用TERRA/MODIS MOD10A2雪盖产品数据和地面观测积雪日数、冻土深度和沙尘天气日数等数据,从不同时间尺度分析古尔班通古特沙漠地表积雪覆盖与沙尘天气的特征及其相互关系。结果表明:①沙尘天气主要发生在4—10月,春季（4—5月）沙尘天气最多,夏秋季逐渐减少。从年际变化看,20世纪80年代前,沙尘天气发生日数呈逐年增加趋势,而积雪日数增减波动较大,二者间关系不明显,80年代后,沙尘天气逐年减少,积雪日数呈波动增加趋势。②冬春季积雪覆盖率、≥1 cm积雪日数、≥5 cm积雪日数、≥10 cm积雪日数与翌年春季沙尘天气发生均呈显著负相关关系,冬春季≥1 cm积雪日数每超过常年平均积雪日数1 d,翌年春季沙尘天气日数则减少4.3 d,而平均冻土深度与沙尘天气呈显著正相关关系。③积雪覆盖使沙漠地表形成冷源性下垫面和近地层逆温层结,增加了大气稳定度,同时春季积雪消融增加了土壤湿度,为荒漠植被生长提供充足的水分,使表层土壤为强风提供沙尘的可能性降低,从而对沙尘天气的发生起到阻碍、消弱作用。     

A simplified method to determine seismic responses of reinforced concrete moment resisting building frames under influence of soil–structure interaction

As the Iranian seismic code does not address the soil–structure interaction (SSI) explicitly, the effects of SSI on RC-MRFs are studied using the direct method. Four types of structures on three types of soils, with and without the soil interaction, are modeled and subjected to different earthquake records. The results led to a criterion indicating that considering SSI in seismic design, for buildings higher than three and seven stories on soil with V_s<175 m/s and 175<V_s<375 m/s, respectively, is essential. A simplified procedure has been presented, on the basis that lateral displacement increments could be applied to the fixed-base models using simple factors.     

An example of application: The ecological “natural flow regime” paradigm in hydroclimatology

According to the concept of “natural flow regime,” introduced and developed in the 1990's in aquatic ecology, streamflow can be described using five basic characteristics: magnitude, frequency, duration, period of occurrence and variability. A sixth could be added to these, namely, distribution curve. Our study, which focused exclusively on the temporal variability of these six characteristics, had these objectives: (1) to compare their stationarity, (2) to determine the links among these characteristics and (3) to analyze, for the first time, their relationship to six climatic indices (Atlantic Multidecadal Oscillation, Artic Oscillation, North Atlantic Oscillation, Niño3.4, Pacific decadal Oscillation and Southern Oscillation Index). To do this, we used the Vermillon River (2670 km²) as an example, analyzing the streamflow of heavy spring floods (equal to or greater than the annual flood streamflow), as measured between 1934 and 2000.     

Comparison of ordinary kriging and artificial neural network for spatial mapping of arsenic contamination of groundwater

In this technical note, we investigate the hypothesis that ‘non-linearity matters in the spatial mapping of complex patterns of groundwater arsenic contamination’. The spatial mapping pertained to data-driven techniques of spatial interpolation based on sampling data at finite locations. Using the well known example of extensive groundwater contamination by arsenic in Bangladesh, we find that the use of a highly non-linear pattern learning technique in the form of an artificial neural network (ANN) can yield more accurate results under the same set of constraints when compared to the ordinary kriging method. One ANN and a variogram model were used to represent the spatial structure of arsenic contamination for the whole country. The probability for successful detection of a well as safe or unsafe was found to be atleast 15% larger than that by kriging under the country-wide scenario. The probability of false hopes, which is a serious issue in public health monitoring was found to be significantly lower (by more than 10%) than that by kriging.     

Removal of the Alphazurine FG Dye from Simulated Solution by Electrocoagulation

The removal of Alphazurine FG (AF) dye from water by an electrocoagulation process has been studied. The effect of some operational parameters, such as anode material, current density, initial dye concentration, pH of solution, conductivity, and inter‐electrode distance, on the removal efficiency was investigated. Iron and aluminum were used as anodes in the electrocoagulation cell. It was found that the efficiency of the iron anode was better than that of the aluminum anode for AF removal. The factors that affected the removal efficiency were the current density and the initial dye concentration. The removal efficiency increased from about 35% at 25 A m^–2 to about 97% at 100 A m^–2, during 4 min of electrocoagulation. The results exhibited pseudo‐first‐order kinetics for AF removal by electrocoagulation. In addition, a mathematical model was successfully established for predicting the removal efficiency. A comparison between the model results and experimental data gave a high correlation coefficient (R² = 0.9925), which indicates that the model is able to predict the removal efficiency of AF.