Palynostratigraphy and vegetation characteristics of Neogene continental deposits interbedded with the Cappadocia ignimbrites (Central Anatolia, Turkey)

A palynological analysis of the Late Miocene and Early Pliocene successions of the Cappadocian Volcanic Province (Central Anatolia, Turkey) has been carried out with the aim of reconstructing the palaeovegetation and palaeoclimatic conditions. The samples are collected from outcrop sections from three different localities (A: Akda?, B: Bayramhac?l? and G: Güzelöz). The pollen spectra reveals the existence of a steppe vegetation dominated by Amaranthaceae–Chenopodiaceae and Artemisia, typical of present day arid and semi-arid continental areas (i.e. Middle East), and Asteraceae Asteroideae in the A section (Late Miocene) developed in arid climatic conditions. The flora of the G (Early Pliocene) and lower part of the B (Late Miocene) sections reflects steppes on which Asteraceae Asteroideae was dominant. This flora also indicates arid conditions. The development of trees in the upper part of the B section was possibly related to local paleoenvironmental conditions rather than a climatic change. This study provides the first palynological data to reveal the presence of an Amaranthaceae–Chenopodiaceae and Artemisia steppe already during the Late Miocene in Turkey.     

Groundwater recharge in irrigated semi-arid areas: quantitative hydrological modelling and sensitivity analysis

For semi-arid regions, methods of assessing aquifer recharge usually consider the potential evapotranspiration. Actual evapotranspiration rates can be below potential rates for long periods of time, even in irrigated systems. Accurate estimations of aquifer recharge in semi-arid areas under irrigated agriculture are essential for sustainable water-resources management. A method to estimate aquifer recharge from irrigated farmland has been tested. The water-balance-modelling approach was based on VisualBALAN v. 2.0, a computer code that simulates water balance in the soil, vadose zone and aquifer. The study was carried out in the Campo de Cartagena (SE Spain) in the period 1999–2008 for three different groups of crops: annual row crops (lettuce and melon), perennial vegetables (artichoke) and fruit trees (citrus). Computed mean-annual-recharge values (from irrigation+precipitation) during the study period were 397 mm for annual row crops, 201 mm for perennial vegetables and 194 mm for fruit trees: 31.4, 20.7 and 20.5% of the total applied water, respectively. The effects of rainfall events on the final recharge were clearly observed, due to the continuously high water content in soil which facilitated the infiltration process. A sensitivity analysis to assess the reliability and uncertainty of recharge estimations was carried out.     

Modelling shallow landslide susceptibility: a new approach in logistic regression by using favourability assessment

A new method for estimating shallow landslide susceptibility by combining Geographical Information System (GIS), nonparametric kernel density estimation and logistic regression is described. Specifically, a logistic regression is applied to predict the spatial distribution by estimating the probability of occurrence of a landslide in a 16 km² area. For this purpose, a GIS is employed to gather the relevant sample information connected with the landslides. The advantages of pre-processing the explanatory variables by nonparametric density estimation (for continuous variables) and a reclassification (for categorical/discrete ones) are discussed. The pre-processing leads to new explanatory variables, namely, some functions which measure the favourability of occurrence of a landslide. The resulting model correctly classifies 98.55% of the inventaried landslides and 89.80% of the landscape surface without instabilities. New data about recent shallow landslides were collected in order to validate the model, and 92.20% of them are also correctly classified. The results support the methodology and the extrapolation of the model to the whole study area (278 km²) in order to obtain susceptibility maps.     

The Response of Estuarine Macrobenthic Communities to Natural- and Human-Induced Changes: Dynamics and Ecological Quality

Anthropogenic activities are a disturbance factor of coastal systems and can be widely recognized as a major threat to the health of coastal systems. However, natural events cannot be disregarded from management issues because of their significant influence on the communities living in these areas. Based on long-term subtidal data from the Mondego Estuary (Portugal), the effects of natural events (e.g., floods and droughts) on macrobenthic communities were compared with the anthropogenic events. Sampling stations were grouped into characteristic zones (mouth, north arm, south arm) so the community dynamics of each of these estuarine areas could be followed over time. Environmental assessment was performed for stations using the Benthic Assessment Tool (BAT), and compared with the existing pressures. Human impacts persist over a number of years and gradually reduce ecosystem health, as discussed in the European Water Framework Directive. Paradoxically, natural events cause stronger impacts but are of a shorter duration, which allows for a faster recovery of macrobenthic communities. The study showed that caution should be taken when developing and implementing water policies so as not to disregard the importance of the different events (natural and human-caused) on the ecosystem health (e.g., community degradation and water quality and ecological quality status assessment).     

Procedure for the selection of runout model parameters from landslide back-analyses: application to the Metropolitan Area of San Salvador, El Salvador

The existing procedures for the selection of runout model parameters from back-analyses do not allow integrating different types of runout criteria and generally lack a systematic approach. A new method based on receiver operating characteristic (ROC) analyses and aimed at overcoming these limitations is herein proposed. The method consists of estimating discrete classifiers for every runout simulation associated with a set of model parameters. The set of parameters that yields the best prediction is selected using ROC metrics and space. The procedure is illustrated with the back-analyses of a rainfall-triggered debris flow that killed 300–500 people in the Metropolitan Area of San Salvador in 1982. The selected model parameters are used to estimate forward predictions for scenarios that correspond to different return periods. The proposed procedure may be useful in the assessment of areas potentially affected by landslides. In turn, this information can be used in the production or updating of land use plans and zonations, similar to that currently being carried out by the Office for Urban Planning of the Metropolitan Area of San Salvador in El Salvador.     

Interpretation and modelling of regional gravity data of the Aveiro Basin (Northwest Portugal)

The gravity map of the Aveiro Basin, North West Portugal was produced in 2000/2001 and some limited two dimensional (2D) interpretation was carried out. It is intended in this article to advance the interpretation and modelling of the original Aveiro basin gravity data. Thus, the data were processed and the horizontal gradient, the second vertical derivative and downward continued field computed. The corresponding maps have been processed and a new interpretation of the basin tectonic features has been proposed. This is compared with the previous geological and tectonic information obtained from former surveys and local boreholes. As the next step a more detailed modelling of the Aveiro Basin took place. Bearing the interpretation of the basin tectonic features in mind, several north–south and east–west gravity profiles were established and modelled. The proposed models were presented and discussed. As a result, a comprehensive mass distribution model for the basin was proposed. Finally, comparison was made between the new gravity model and the previously published tectonic features map. This modelling is particularly useful for groundwater protection, exploration and exploitation and also for the dimensioning of drilling operations. Bearing in mind the geomorphology of the basin the gravity method is a very economical tool for the investigation of basin structures.     

天津市潮间带柱状沉积物中重金属的污染历史及来源判别

利用因子分析和元素含量特征分析两种方法,对天津市潮间带的4个无扰动沉积物柱样的46个样品进行了重金属分析,并探讨了重金属的来源方式和富集原因。研究结果表明,天津市潮间带的重金属可分为3类:1)Fe、Cr、Al及Mn元素主要受环境背景值的影响,2)Hg和Cd受人为活动的影响较大,3)As、Zn、Pb、Cu及Ni受环境背景值及人类活动的双重影响,且影响大小随所在位置的不同而变化。结合210Pb和137Cs测年结果,定量确定了天津市潮间带小于0.063 mm粒级沉积物中Ni等11种重金属元素的环境背景值,并以此为基础,进一步探讨了重金属富集年代、富集量及污染历史和人类活动的关系,发现多数重金属的污染始于1910年代,并在1954年之后富集量增加。     

Grass cover density and metal speciation in profiles of a tailings-pile from a mining zones in Zacatecas,North-Central Mexico

The 7-year-old mine tailings pile P2 from Concepción del Oro has been revegetated spontaneously by xerophyte grasses, covering about the 30% of its surface. To elucidate the effect of the grass cover in the geochemical behavior of the sulfide minerals (SM) and metals, the strata of four selected profiles (P2-I, P2-II, P2-III and P2-IV, with high, middle, low, and null grass cover, respectively) were analyzed mineralogically and chemically, using scanner electron microscopy, X-ray diffractometer and performing a six-step sequential extraction method. An older (50-year-old) and uncovered (without grass cover) profile of the tailings pile P3 was also analyzed. In all the profiles from P2, the SM oxidation is not yet an extended process; however, the samples from the uncovered profile P2-IV showed evidences of SM (pyrite and chalcocite) oxidation, as well as the presence of gypsum and Fe oxides, as the major secondary phases resulted from the SM oxidation. Additionally, the carbonate content and pH values in P2-IV were lower than in the covered profiles from P2. The oldest and uncovered P3-I profile showed an extensive oxidation of sulfurs which resulted in the depletion of carbonates and a pH 2. Another distinctive characteristics of the covered profiles was that Pb, Cu, and Zn were mainly associated with the reducible fractions (carbonates and/or amorphous oxides); meanwhile, in the uncovered (P2-IV and P3-I) such metals were mainly associated with the oxidizable fraction (crystalline oxides). The results suggest that the mineralogical transformations control metal stability in plant-covered impoundments (phytostabilization): the occurrence of a thick grass cover, with an efficient water usage and retention, seems to shun both the acidic dissolution of carbonates and the reductive dissociation of the formerly present oxyhydroxides, which is desired for remediation tasks. This is the first report about the effects of grass cover for a carbonaceous and unsaturated mine tailings from a semiarid region, that can help in a better understanding of the scope of phytoremediation in such conditions.     

Construction of deep tunnel shafts in Mexico city soft clays by the flotation method

The drainage system of Mexico City, one of the largest metropolitan areas in the world, is formed by a large network of interceptors and collectors leading to the main outlet: a 49.3-km-long tunnel with a 6.5 m diameter. To build the access shafts to the tunnels of the system and the deep sumps of the pumping stations in the very soft clays of the lacustrine area of Mexico valley, a technique known as “flotation method” has been commonly used since 1969. The paper presents the main construction steps followed and some aspects of the analysis and design of shafts constructed by this technique. The experience gained obtained after more than 30 shafts have been constructed by this method, and the actual trends in its application are also discussed.     

Soil moisture dynamics under different land uses on karst hillslope in northwest Guangxi,China

Temporal and spatial dynamics of soil moisture are little known on karst hillslope with shallow soil in subtropical region. The objectives of this paper were (1) to investigate the temporal dynamics of soil moisture at depth of 0–10 cm under different land uses; and (2) to understand the relationship between mean and coefficient of variation (CV) of moisture contents on karst hillslope in northwest Guangxi, China. Soil moisture contents had a moderate variation (CV 17.5–30.3%) over an 8-month period and they had a significant difference among different land uses at the 0.01 level with a decreasing order: native scrubland > abandoned cropland and sloping cropland > economic forestland. There were higher mean and lower CV of moisture contents in rainy season than those in drought season. Mean and CV of moisture contents had a significant negative linear relationship except in abandoned cropland with higher soil and vegetation heterogeneity. This suggested that spatial variability of soil moisture within sampling sites would decrease when soils were wet and increase when soils were arid. Compared with rainy season, more soil samples may be needed and the interval for sampling should be shortened in drought season. Such information provided some insights to better understand the dynamics and variability of soil moisture at a larger scale in karst region of southwest China.