Spatial information of soil hydraulic conductivity and performance of cokriging over kriging in a semi-arid basin scale

Unlike the studies in small parcels by systematic measurements, the spatial variability of soil properties is expected to increase in those over relatively large areas or scales. Spatial variability of soil hydraulic conductivity (K _h) is of significance for the environmental processes, such as soil erosion, plant growth, transport of the plant nutrients in a soil profile and ground water levels. However, its variability is not much and sufficiently known at basin scale. A study of testing the performance of cokriging of K _h compared with that of kriging was conducted in the catchment area of Sarayköy II Irrigation Dam in Cank?r?, Turkey. A total of 300 soil surface samples (0–10 cm) were collected from the catchment with irregular intervals. Of the selected soil properties, because the water-stable aggregates (WSA) indicated the highest relationship with the hydraulic conductivity by the Pearson correlation analysis, it is used as an auxiliary variable to predict K _h by the cokriging procedure. In addition, the sampling density was reduced randomly to n = 175, n = 150, n = 75 and n = 50 for K _h to determine if the superiority of cokriging over kriging would exist. Statistically, the results showed that all reduced K _h was as good as the complete K _h when its auxiliary relations with WSA were used in cokriging. Particularly, the results of the “Relative Reduction in MSE” (RMSE) revealed that the reduced data set of n = 75 produced the most accurate map than the others. In this basin-scaled study, there was a clear superiority of the cokriging procedure by the reduction in data although a very undulating topography and topographically different aspects, two different land uses with non-uniform vegetation density, different parent materials and soil textures were present in the area. Hence, using the statistically significant auxiliary relationship between K _h and WSA might bring about a very useful data set for watershed hydrological researches.     

Case study of PM pollution in playgrounds in Istanbul

In a world where at least 50% of the population is living in urban environments, air pollution and specifically particulate matter (PM) have become one of the most critical issues for human health. Children are more susceptible than adults to air pollution and its adverse effects because they inhale and retain larger amounts of air pollutants per unit of body weight. In this study, PM pollution, particularly PM₁₀ and PM_2.5, at selected playgrounds were investigated in Istanbul city. Istanbul is a megacity of over 15 million inhabitants, and on-road traffic is increasing rapidly (over 3 million vehicles on the road). To estimate the effect of traffic emissions on children, the location of the playgrounds were selected according to traffic density. Measurements were carried out at five different playgrounds throughout the city in 2009. Field results show that the values of PM₁₀ and PM_2.5 have reached critical limits at the playgrounds close to the main roads, especially at P-1. Thus, we focused on this location and investigated a source other than traffic emissions. One of the episode days has been observed on 5–7 March 2009. Evaluations of meteorological events are very important to determine air pollution sources and their long-range transport. Therefore, the Weather Research and Forecasting model (WRF) was used to simulate and forecast meteorological parameters and the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) applied to investigate long-range transport. According to the WRF model outputs, there was a low-pressure system over Geneva gulf on the 500-hPa level, and its core had been located over Britain on 5 March 2009 00UTC. The system had been sweeping dust from the Sahara Desert and carrying the air particles over Istanbul. Similarly, backward HYSPLIT analysis showed that air particles had moved through Istanbul from Northern Africa.     

Assessment of shrinkage–swelling influences in coal seams using rank-dependent physical coal properties

Characterization of coal reservoirs and determination of in-situ physical coal properties related to transport mechanism are complicated due to having lack of standard procedures in the literature. By considering these difficulties, a new approach has been developed proposing the usage of relationships between coal rank and physical coal properties. In this study, effects of shrinkage and swelling (SS) on total methane recovery at CO₂ breakthrough (TMRB), which includes ten-year primary methane recovery and succeeding enhanced coalbed methane (ECBM) recovery up to CO₂ breakthrough, and CO₂ sequestration have been investigated by using rank-dependent coal properties. In addition to coal rank, different coal reservoir types, molar compositions of injected fluid, and parameters within the extended Palmer & Mansoori (P&M) permeability model were considered. As a result of this study, shrinkage and swelling lead to an increase in TMRB. Moreover, swelling increased CO₂ breakthrough time and decreased displacement ratio and CO₂ storage for all ranks of coal. Low-rank coals are affected more negatively than high-rank coals by swelling. Furthermore, it was realized that dry coal reservoirs are more influenced by swelling than others and saturated wet coals are more suitable for eliminating the negative effects of CO₂ injection. In addition, it was understood that it is possible to reduce swelling effect of CO₂ on cleat permeability by mixing it with N₂ before injection. However, an economical optimization is required for the selection of proper gas mixture. Finally, it is concluded from sensitivity analysis that elastic modulus is the most important parameter, except the initial cleat porosity, controlling SS in the extended P&M model by highly affecting TMRB.     

Chromatographic Separation and Analytic Procedure for Priority Organic Pollutants in Urban Air

A separation procedure was developed for analysis of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in urban air, while simultaneously eliminating the interfering compounds. This was carried out by optimization of a column chromatograph with regard to the eluent type (n‐hexane and n‐pentane), volume of eluent, type of sorbent material (silica gel and florisil) and activation level of the sorbent material. The determination of the level of PCBs and PAHs was carried out using gas chromatography (GC) equipped with a mass selective detector (MSD), while determination of the OCPs was carried out by GC equipped with an electron capture detector (μ‐ECD). The use of a silica gel column (10 g, 5% deactivated with H₂O) with 70 mL of n‐hexane gave satisfactory separation of PCBs from PAHs and OCPs. After collecting the PCBs with 70 mL of n‐hexane, 3·20 mL of n‐hexane:ethyl acetate, (1:1, v:v) was adequate for elution of the PAHs and OCPs from the column. The primary aim of this study was to develop a multimethod for analyses of PCBs, PAHs, and OCPs in urban air as well as reducing solvent and sorbent consumption and analysis time during the clean‐up procedure compared to the US EPA standard methods (EPA methods TO‐13A for PAHs and TO‐4A for both PCBs and OCPs).     

Evaluation of burial history, thermal maturity and source-rock assessment of the Upper Paleozoic succession of the eastern Taurus region, southern Turkey

The regional burial history pattern, thermal maturity variations and source rock assessment of the sedimentary succession in the eastern Taurus region, in the southern part of Turkey, have been studied on surface samples collected from the six different sections which represent the entire region. Organic petrography (Thermal Alteration Index) and geochemical data (TOC content, T_max and HI values) were obtained from transmitted-light microscopy and Rock-Eval pyrolysis.The Lower Paleozoic (Cambrian, Ordovician and Silurian) strata were not investigated and modeled in terms of the maturity and hydrocarbon source rock potential, because of their poor organic matter content and their over maturity resulting from great burial depth (more than 7630 m). Other Paleozoic strata, except the Lower Devonian Ayitepesi Formation, generally have the values of more than 0.5% TOC. Organic matter of the Middle Devonian Safaktepesi sediments are composed of highly terrestrial organic material (type III kerogen), while samples from other three formations (Gumusali, Ziyarettepe and Yigilitepe Formations), while samples from other organic matter (type II and type III kerogen). The average TAI values are as high as 3.4 (equivalent to 1.42 of R₀%) for Ayitepesi and as low as 2.75 (equivalent to 0.77 of R₀%) for Yigilitepe Formations. Time-temperature index values (TTI) indicate that Ziyarettepe and Yigilitepe sediments are marginally mature to mature, while the Devonian strata are overmature. There are minor discrepancies between ΣTTI values and geochemical data in terms of the organic maturity for Devonian strata. In contrast, the e is a consistency between those values for the Ziyarettepe and the Yigilitepe Formations. The onset of oil generation time in the region was initiated from as early as the Norian (216 Ma) to as late as the Lutetian (45 Ma).Regional variations in the level of thermal and source-rock maturities of the Upper Paleozoic sediments in the eastern Taurus region largely depend on burial depth.     

Water absorption process effect on strength of Ayazini tuff,such as the uniaxial compressive strength (UCS), flexural strength and freeze and thaw effect

Tuffs have been used as a construction material possibly since ancient times. In Afyonkarahisar, Turkey, there are numerous buildings constructed by tuff. Tuff has been a local construction material, during the Roman, Seljuk and Ottoman periods. Even though tuffs have relatively low durability and low strength values compared to marble, etc., they have survived with no major deterioration failures on many historical buildings. It has also been preferred because of its high porous texture, lightweight and easy shaping and process properties in the building sector. Naturally, it would be easily affected by water and humidity because of its porous structure. However, having this kind of structure leads to poor durability properties due to keeping water in it. The main objective of this study was to evaluate the physical and mechanical properties of the tuff quarried from the region and possible water effect, which may lead to degradation of its strength and durability of the material, thereby shortening the life span of the building structure used. Samples, which were tested after exposing to water and the freeze and thaw effects, were measured at a certain time. In this study, uniaxial compressive strength and flexural strength tests were conducted on test samples. The test results indicate that water may deteriorate the tuff’s strength properties and durability of the materials in due time.     

Geology and geochemistry of jasperoids from the Gold Bar district, Nevada

Gold Bar is one of several Carlin-type gold mining districts located in the Battle Mountain–Eureka trend, Nevada. It is composed of one main deposit, Gold Bar; five satellite deposits; and four resources that contain 1.6 Moz (50 t) of gold. All of the deposits and resources occur at the intersection of north-northwest- and northeast-trending high-angle faults in slope facies limestones of the Devonian Nevada Group exposed in windows through Ordovician basin facies siliciclastic rocks of the Roberts Mountains allochthon. Igneous intrusions and magnetic anomalies are notably absent. The Gold Bar district contains a variety of discordant and stratabound jasperoid bodies, especially along the Wall Fault zone, that were mapped and studied in some detail to identify the attributes of those most closely associated with gold ore and to constrain genetic models. Four types of jasperoids, J₀, J₁, J₂, and J₃, were distinguished on the basis of their geologic and structural settings and appearance. Field relations suggest that J₀ formed during an early event. Petrographic observations, geochemistry, and δ¹⁸O values of quartz suggest it was overprinted by the hydrothermal event that produced ore-related J₁, J₂, and J₃ jasperoids and associated gold deposits. The greater amount of siliciclastic detritus present in J₀ jasperoids caused them to have higher δ¹⁸O values than J_1,2,3 jasperoids hosted in underlying limestones. Ore-related jasperoids are composed of main-ore-stage replacements and late-ore-stage open-space filling quartz with variable geochemistry and an enormous range of δ¹⁸O values (24.5 and −3.7‰). Jasperoids hosted in limestones with the most anomalous Au, Ag, Hg, ±(As, Sb, Tl) concentrations and the highest δ¹⁸O values are associated with the largest deposits. The 28‰ range of jasperoid δ¹⁸O values is best explained by mixing between an ¹⁸O-enriched fluid and an ¹⁸O-depleted fluid. The positive correlation between the sizes of gold deposits and the δ¹⁸O composition of jasperoids indicates that gold was introduced by the ¹⁸O-enriched fluid. The lowest calculated δ¹⁸O value for water in equilibrium with late-ore-stage quartz at 200°C (−15‰) and the measured δD value of fluid inclusion water extracted from late-ore-stage orpiment and realgar (−116‰) indicate that the ¹⁸O-depleted fluid was composed of relatively unexchanged meteoric water. The source of the ¹⁸O-enriched ore fluid is not constrained. The δ³⁴S values of late-ore-stage realgar, orpiment, and stibnite (5.7–15.5‰) and barite (31.5–40.9‰) suggest that H₂S and sulfate were derived from sedimentary sources. Likewise, the δ¹³C and δ¹⁸O values of late-stage calcite (−4.8 to 1.5‰ and 11.5 to 17.4‰, respectively) suggest that CO₂ was derived from marine limestones. Based on these data and the apparent absence of any Eocene intrusions in the district, Gold Bar may be the product of a nonmagmatic hydrothermal system.     

Effects of land-based sources on water quality in the Omerli reservoir (Istanbul,Turkey)

The Omerli reservoir is located on the northeastern side of the Istanbul City. It is one of the most important sources of drinking water with a surface area of 23.1 km² and a volume of 220 × 10⁶ m³ in the Marmara Region. Water quality characteristics of the lake investigated from May 2002 to April 2003 enabled us to identify the effect of waste loads on water quality of Omerli Lake. The following parameters were measured in the lake water: temperature (16.1°C), conductivity (250 μS/cm), secchi disk depth (1.9 m), dissolved oxygen (DO) (9.36 mg/L), nutrients [ortho-phosphate (78.9 μg/L), nitrate + nitrite (707.5 μg/L) and ammonia-nitrogen (264 μg/L)], chlorophyll a (9.43 μg/L), total organic carbon (3.33 mg/L), total suspended solids (4.54 mg/L), total poly aromatic hydrocarbon (t-PAH) (0.69 μg/L) and copper (24.5 μg/L). T-PAH (16.5 mg/g-dry-w), Cu (96.5 μg/g-dry-w), organic carbon (org-C) (2.0%) and N (0.44%) were determined in the surface sediment. The values of chlorophyll a and DO in the upper layer were relatively high and low secchi disk depths indicates eutrophic state. There are five channels discharging water, including waste water, into the lake. All channels were sampled during six occasions in order to cover variations between seasons. The following parameters were measured: total organic carbon, total phosphorus, total kjeldahl nitrogen, ammonia and total suspended solids with the flow rates. The Göçbeyli stream has the highest flow into the lake (1.5 × 10⁸ m³/year) but most of the nutrients were discharged from the Pa?aköy channel. It is accounting for 81% of ammonia and 80% of total phosphorus into the lake. Three scenarios were run using AQUATOX model: (1) all existing inflows are discharging into the lake (present situation); (2) none is discharging; (3) all are discharging except the Pa?aköy channel. The first scenario produced concentrations consistent with measurements in the lake. In all stations, a phytoplankton peak value was predicted during November and December 2002, and January 2003. In the second scenario, as expected, a significant decrease in the concentrations was predicted. In the third scenario, a small improvement in the water quality was obtained. To significantly improve the state of the lake, instead of entering Pa?aköy channel, wastewater should bypass the lake.     

A study on geotechnical characterization and stability of downstream slope of a tailings dam to improve its storage capacity (Turkey)

Tailings, waste products of the ore-dressing processes, are usually stored in a slurry form and pumped into sedimentation pond which is surrounded by natural heights and/or artificial walls. The database of International Commission of Large Dams and United Nations Environment Programme showed that several hundreds of tailings dam have failed since 1910. One of the reasons of these failures is slope instability. Construction of mine tailings dams in Turkey has started to increase, particularly in the recent decade. This paper focuses the study undertaken to assess the geotechnical characteristics and stability of downstream slope of a tailings dam at a copper-zinc mine in the Black Sea Region of Turkey. At the mine site there are two tailings dams located at two different elevations. The upper dam was completely filled and is out of service. Increasing amount of tailings filling the pond of the lower dam resulted in a limited storage, and therefore, it has been decided that heightening of the dam about 7 m to improve its storage facility would be necessary. For the purpose, a series of investigations in the vicinity of the tailings dam and some geomechanical laboratory tests were carried in conjunction with the use of empirical methods to determine mechanical properties of the current dam material, tailings and the rockfill material that will be used for heightening of the dam. The results of the static and pseudo-static stability analyses based on the methods of limit equilibrium and numerical modelling indicated that circular and non-circular failures are the most critical modes of failure for the dam and safety factor gradually decreases when the tailings rise up to a specific elevation in the pond. However, the ranges of the calculated safety factors from both methods are considerably similar and suitable for heightening of the dam by 7 m in terms of stability. The results suggest that any instability is not expected under both static and dynamic conditions after the current height of the tailings dam is increased by 7 m, if the slope geometry considered in the analyses is not changed and the tailings in the pond do not rise up to an elevation of about 475 m. In addition, magnitude of permanent settlement of the dam due to a probable earthquake was also assessed using two empirical methods and the results from both methods showed similar amount of settlements which were in tolerable limits.