Effects of accelerating and decelerating flows in a channel with vegetated banks and gravel bed

Experiments were conducted in an 8 m long,40 cm wide,and 60 cm deep re-circulating fiume with vegetated banks and gravel bed to study the effects of accelerating and decelerating flows on the flow stru...     

Geochemical Investigation of the Cretaceous Crude Oil Reservoirs and Source Rock Samples in One of the Abadan Plain Oilfields, SW Iran

Crude oil and source rock samples from one of the main oilfields of the Abadan Plain, Zagros, Iran were analyzed geochemically. Rock-Eval pyrolysis was conducted on Kazhdumi (Upper Cretaceous) and Gadvan (Lower Cretaceous) formations, which are the probable source rocks for the oil in the region. The results indicated that the Kazhdumi Formation can be classified as a fair-to-excellent source rock, while the Gadvan Formation can be identified as having poor-to-good source rock in the basin. Based on the cross-plots of HI versus OI and S2 versus TOC, types II and III kerogen were identified from studied source samples in the area. Determination of the main fraction percentages of the Sarvak and Fahliyan crude oils represented that the oils from the Sarvak reservoir are paraffinic-naphthenic and aromatic-intermediate, whilst that from the Fahliyan reservoir is paraffinic and paraffinic-naphthenic. Biomarker ratios of the saturated fractions of oil from both reservoirs indicate that the source rocks formed in reducing marine environments with carbonate-shale lithology. Furthermore, biomarker data helped to distinguish the degree of biodegradation in the studied oils. According to geochemical analysis, oil samples from the Fahliyan reservoir were generated at a higher thermal maturity than the Sarvak reservoir samples.     

A multifractal cross-correlation investigation into sensitivity and dependence of meteorological and hydrological droughts on precipitation and temperature

Natural Hazards - Several studies have been conducted on droughts, precipitation, and temperature, whereas none have addressed the underlying relationship between nonlinear dynamic properties and...     

Long-term change of surface temperature in water bodies around Iran – Caspian Sea,Gulf of Oman,and Persian Gulf – using 2001–2015 MODIS data

ABSTRACT

To answer the question “what has changed the surface temperatures of water bodies around Iran under climate change conditions,” Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) data with 9.2-km spatial resolution and monthly time step were evaluated. A significant increasing trend was obtained using Pearson’s correlation coefficient and Mann-Kendall trend test on data from the Caspian Sea (June) and the Southern Gulfs (September). High correlations of 0.69 and 0.97 between remotely sensed data and ERA-Interim reanalysis data were also obtained for June and September, respectively. To assess the impact of some climatic parameters on SST variability in those two months, zonal and meridional wind at 10 m, wind speed at 10 m, air temperature at 2 m, and mean sea level pressure were evaluated. High correlations between meridional wind and the Southern Gulf SST, and meridional wind and Caspian SST were ?0.86 and 0.75, respectively. Moreover, the results showed an important role of air temperature (0.96) and sea level pressure (?0.77) in the rising temperature trends of the Southern Gulfs. Wind speed was also detected in both regions as a booster of the trend.     

Effects of sheet flow rate and slope gradient on sediment load

Sheet erosion is known as one of the most important forms of erosion, particularly in agricultural land. The purpose of this study was to investigate the effect of flow rate and slope gradient on runoff and sediment discharges in two different soils. Experiments were conducted using a tilting flume facility with the test area of 0.2?×?1.0 m. Overall, 24 experiments on two soils (clay loam and sandy clay loam textures) including six flow rates (75, 100, 125, 150, 175, and 200 ml/s) and two slope gradients (1.5 and 2 %) were performed. The selected flow rates and flume slopes were generated to simulate sheet erosion. The results showed that for both soils and slopes, unit flow discharge (q) and sediment concentration increased with increasing flow rate; however, the effect of slope gradient on flow discharge depends on soil type. In addition, sandy clay loam exhibited higher values of q and sediment concentration and consequently, it showed greater amounts of sediment load. At the start of event, sediment concentration was high but it decreased to approach a steady state. In addition, the time needed to reach a steady state condition was shorter for sandy clay loam than that for clay loam soil and in lower flow rates than higher flow rates. For each soil and slope, there was a direct relationship between sediment load and flow rate. The result implied that the effect of slope gradient on sediment load was almost greater in sandy clay loam soil than clay loam soil. Moreover, the differences between sediment loads of two soils are enlarged at slope 2 %.     

Modeling Fate and Transport of Volatile Organic Compounds (VOCs) Inside Sewer Systems

Hazardous waste site investigations have shown that volatile organic compounds (VOCs) can be transported via sewer pipes and migrate into indoor spaces. Despite field data confirming the presence of this exposure pathway, there is lack of context-based numerical models that provide guidance to characterize and predict VOCs concentration in sewer gas at vapor intrusion sites. Particularly, this poses a challenge when assessing and mitigating risks associated with these exposure pathways. Therefore, a numerical model has been developed to simulate the concentration of VOCs in sewer gas in different stages throughout the sewer lines. The developed model considers various input parameters, including temperature, sewer liquid depth, groundwater depth, and sewer construction characteristics to incorporate local and operational conditions. The model's output is verified using field data from a sewer system constructed near a Superfund site. Moreover, a sensitivity analysis was conducted to evaluate the model's response to variation of the external input parameters. To the best of our knowledge, this study is the first attempt to model VOCs concentration in sewer gas, particularly to address vapor intrusion. The developed model can be used as a numerical tool to support the development of sewer assessment guidelines, risk assessment studies, and mitigation strategies.     

Deep learning approaches for improving prediction of daily stream temperature in data-scarce,unmonitored, and dammed basins

Basin-centric long short-term memory (LSTM) network models have recently been shown to be an exceptionally powerful tool for stream temperature (T_s) temporal prediction (training in one period and predicting in another period at the same sites). However, spatial extrapolation is a well-known challenge to modelling T_s and it is uncertain how an LSTM-based daily T_s model will perform in unmonitored or dammed basins. Here we compiled a new benchmark dataset consisting of >400 basins across the contiguous United States in different data availability groups (DAG, meaning the daily sampling frequency) with and without major dams, and studied how to assemble suitable training datasets for predictions in basins with or without temperature monitoring. For prediction in unmonitored basins (PUB), LSTM produced a root-mean-square error (RMSE) of 1.129°C and an R² of 0.983. While these metrics declined from LSTM's temporal prediction performance, they far surpassed traditional models' PUB values, and were competitive with traditional models' temporal prediction on calibrated sites. Even for unmonitored basins with major reservoirs, we obtained a median RMSE of 1.202°C and an R² of 0.984. For temporal prediction, the most suitable training set was the matching DAG that the basin could be grouped into (for example, the 60% DAG was most suitable for a basin with 61% data availability). However, for PUB, a training dataset including all basins with data was consistently preferred. An input-selection ensemble moderately mitigated attribute overfitting. Our results indicate there are influential latent processes not sufficiently described by the inputs (e.g., geology, wetland covers), but temporal fluctuations can still be predicted well, and LSTM appears to be a highly accurate T_s modelling tool even for spatial extrapolation.     

Fundamental constants and high‐resolution spectroscopy

Absorption‐line systems detected in high resolution quasar spectra can be used to compare the value of dimensionless fundamental constants such as the fine‐structure constant, α, and the proton‐to‐electron mass ratio, μ = m_p/m_e, as measured in remote regions of the Universe to their value today on Earth. In recent years, some evidence has emerged of small temporal and also spatial variations in α on cosmological scales which may reach a fractional level of ≈ 10 ppm (parts per million). We are conducting a Large Programme of observations with the Very Large Telescope's Ultraviolet and Visual Echelle Spectrograph (UVES), and are obtaining high‐resolution (R ≈ 60000) and high signal‐to‐noise ratio (S/N ≈ 100) spectra calibrated specifically to study the variations of the fundamental constants. We here provide a general overview of the Large Programme and report on the first results for these two constants, discussed in detail in Molaro et al. (2013) and Rahmani et al. (2013). A stringent bound for Δα /α is obtained for the absorber at z_abs = 1.6919 towards HE 2217‐2818. The absorption profile is complex with several very narrow features, and is modeled with 32 velocity components. The relative variation in α in this system is +1.3 ± 2.4_stat ± 1.0_sys ppm if Al II λ 1670 Å and three FeII transitions are used, and +1.1 ± 2.6_stat ppm in a slightly different analysis with only FeII transitions used. This is one of the tightest bounds on α ‐variation from an individual absorber and reveals no evidence for variation in α at the 3‐ppm precision level (1σ confidence). The expectation at this sky position of the recently‐reported dipolar variation of α is (3.2–5.4) ± 1.7 ppm depending on dipole model used and this constraint of Δα /α at face value is not supporting this expectation but not inconsistent with it at the 3σ level. For the proton‐to‐electron mass ratio the analysis of the H₂ absorption lines of the z_abs ≈ 2.4018 damped Lyα system towards HE 0027–1836 provides Δμ /μ = (–7.6 ± 8.1_stat ± 6.3_sys) ppm which is also consistent with a null variation. The cross‐correlation analysis between individual exposures taken over three years and comparison with almost simultaneous asteroid observations revealed the presence of a possible wavelength dependent velocity drift as well as of inter‐order distortions which probably dominate the systematic error and are a significant obstacle to achieve more accurate measurements. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Geochemistry of garnet in pegmatites from the Boroujerd Intrusive Complex,Sanandaj-Sirjan Zone,western Iran: implications for the origin of pegmatite melts

Mineralogy and Petrology - Pegmatite-hosted garnets from four localities in the Boroujerd region, Lorestan (Western Iran), have been analysed for major and selected trace element compositions. The...