Petrography and geochemistry of Jurassic sandstones from the Jhuran Formation of Jara dome,Kachchh basin,India: Implications for provenance and tectonic setting

Sandstones of Jhuran Formation from Jara dome, western Kachchh, Gujarat, India were studied for major, trace and rare earth element (REE) geochemistry to deduce their paleo-weathering, tectonic setting, source rock characteristics and provenance. Petrographic analysis shows that sandstones are having quartz grains with minor amount of K-feldspar and lithic fragments in the modal ratio of Q ₈₉:F ₇:L ₄. On the basis of geochemical results, sandstones are classified into arkose, sub-litharenite, wacke and quartz arenite. The corrected CIA values indicate that the weathering at source region was moderate to intense. The distribution of major and REE elements in the samples normalized to upper continental crust (UCC) and chondrite values indicate similar pattern of UCC. The tectonic discrimination diagram based on the elemental concentrations and elemental ratios of Fe₂O₃ + MgOvs. TiO₂, SiO₂ vs. log(K₂O/Na₂O), Sc/Cr vs. La/Y, Th–Sc–Zr/10, La–Th–Sc plots Jhuran Formation samples in continental rift and collision settings. The plots of Ni against TiO₂, La/Sc vs. Th/Co and V–Ni–Th ?10 reveals that the sediments of Jhuran Formation were derived from felsic rock sources. Additionally, the diagram of (Gd/Yb) _N against Eu/Eu ^? suggest the post-Archean provenance as source possibly Nagar Parkar complex for the studied samples.     

Noble metals in graphite-bearing rocks of the Liumao deposit (China)

Native gold, platinum, nickel, and other ore minerals have been discovered in graphite-bearing rocks of the Liumao deposit (Heilongjiang province, China). The results obtained are similar to the previously published materials on the mineralogy of carbon-rich formations of the Tamga and Turgenevo deposits (Primorye, Russian Far East) located in the same region of graphitization in the Khankai terrane as the Chinese object. The defined similarities are most likely explained by participation of deep reduced fluids in the process of ore genesis.     

Episodic Biogeochemical Variability in a Low-Flow Mediterranean Estuary

To investigate to what extent episodic physical processes regulate nutrient availability and phytoplankton assemblages of the Mahon estuary (Minorca Island), we carried out an intensive field study during 2010–2011. During the study period, environmental conditions spanned from intense stratification to a continuous mixing and from lack of riverine inflow to intense runoff. Our data reveals a sequence of biogeochemical states of the estuary that result from the interplay between runoff, other non-periodic forcings (winds, sea level oscillations), and variations in water renewal. Seasonal runoff was revealed as a major driver of winter circulation and of the influx of inorganic nutrients, in particular nitrate. However, because of the combination between runoff and flushing time, the effects of floodwater events on phytoplankton are short-lived (days). Conversely, during summer, when freshwater influx declines, water renewal relies on pulsed atmospheric forcing that may be of local or remote origin. As depicted from the low nitrate concentrations (<1 μM) and enhanced ammonium (>1 μM), this change in circulation and external loads carries nutrient assimilation within the estuary head and forces the use of remnant nutrients through regenerating pathways to sustain an enhanced phytoplankton biomass at the lower estuary. Episodic variability represented between 52 and 65% of the annual chlorophyll variance. Despite the fact that episodic pulses represented intense departures from base biogeochemical state of the estuary, at time scale larger than weeks, the phytoplankton community composition and dynamics was largely regulated by the integrated effect of these episodes and other environmental drivers associated with seasonality rather than by individual storm events only. Our results suggest that even though the system presents good recovery capacity to individual storm episodes, it may be more vulnerable to increased nutrient fluxes during summer, as well as to changes in episode timing and frequency.     

Spatial and Temporal Patterns in <Emphasis Type="Italic">Thalassia testudinum</Emphasis> Leaf Tissue Nutrients at the Chandeleur Islands,Louisiana, USA

Seagrasses are submerged marine plants that are anchored to the substrate and are therefore limited to assimilating nutrients from the surrounding water column or sediment, or by translocating nutrients from adjacent shoots through the belowground rhizome. As a result, seagrasses have been used as reliable ecosystem indicators of surrounding nutrient conditions. The Chandeleur Islands are a chain of barrier islands in the northern Gulf of Mexico that support the only marine seagrass beds in Louisiana, USA, and are the sole location of the seagrass Thalassia testudinum across nearly 1000 km of the coastline from west Florida to central Texas. Over the past 150 years, the land area of the Chandeleur Islands has decreased by over half, resulting in a decline of seagrass cover. The goals of this study were to characterize the status of a climax seagrass species at the Chandeleur Islands, T. testudinum, in terms of leaf nutrient (nitrogen [N] and phosphorus [P]) changes over time, from 1998 to 2015, and to assess potential drivers of leaf nutrient content. Thalassia testudinum leaf nutrients displayed considerable interannual variability in N and P content and molar ratios, which broadly mimicked patterns in annual average dissolved nutrient concentrations in the lower Mississippi River. Hydrological modeling demonstrated the potential for multiple scenarios that would deliver Mississippi River water, and thus nutrients, to T. testudinum at the Chandeleur Islands. Although coastal eutrophication is generally accepted as the proximate cause for seagrass loss globally, there is little evidence that nutrient input from the Mississippi River has driven the dramatic declines observed in seagrasses at the Chandeleur Islands. Rather, seagrass cover along the Chandeleur Islands appears to be strongly influenced by island geomorphological processes. Although variable over time, the often elevated nutrient levels of the climax seagrass species, T. testudinum, which are potentially driven by river-derived nutrient inputs, raises an important consideration of the potential loss of the ecosystem functions and services associated with these declining seagrass meadows.     

Watershed morphometric analysis of Wadi Baish Dam catchment area using integrated GIS-based approach

The integration of Remote Sensing (RS) and Geographic Information Systems (GIS) constitutes a powerful tool for the evaluation of watershed morphometric parameters. The benefits of this integration include saving time and effort as well as improving the accuracy of the analysis. Moreover, this technique is appropriate for describing the watershed and its streams. In this study, a detailed morphometric analysis of the Wadi Baish catchment area has been performed using the Shuttle Radar Topography Mission (SRTM). The performed morphometric analysis includes linear, areal, and relief aspects. The results of the morphometric analysis reveal that the catchment can be described as of eighth stream order and consists of an area of 4741.07 km². Additionally, the basin is characterized by a relatively high mean value of bifurcation (4.012), indicative of the scarcity of permeable rocks with high slope in the area. This value of bifurcation ratio is consistent with the high drainage density value of 2.064 km/km² and confirms the impermeability of the subsurface material and mountainous relief. The hypsometric integral of the catchment is 47.4%, and the erosion integral of the catchment is 52.6%, both were indications of a mature catchment area.     

Origin of nickel in water solution of the chalk aquifer in the north of France and influence of geochemical factors

In the north of France, high registers of nickel are sometimes recorded within the chalk aquifer. In a confined context, the presence of pyrite in the covering clays or in the marcasite nodules encrusted in the clay may constitute a natural source of trace metals. With an objective of sanitary control, the limits of chemical contents regulating the quality of water destined for human consumption have been lowered by the European Framework Directive in the field of water policy (2000/60/EC). As a result, nickel limits have been reduced from 50 to 20 μg/l. The analyses, carried out on three water catchment fields in our area of study, were centred on variable parameters (Eh, O₂(d), pH, Conductivity, T°), major elements (SO₄, NO₃) and metals (Fe, Ni, Mn, Co). The acquired data enabled us to identify from one hand, the conditions which are presented within the site, special thanks to the evolution of nitrate and iron contents and on the other hand, the natural origin (geological) of nickel for two of the three sites studied based essentially on the evaluation of the Nickel/Cobalt ratio. Thus, on the first site, the evolution of nickel content and nitrate content showed the influence of the phenomenon of denitrification on the re-mobilisation of the nickel. Whereas on the second site, a high variation of total iron content and oxygen dissolved in solution highlighted a particular phenomenon of oxidation of the pyrite through molecular oxygen. Finally, the correlation with the sulphates clearly showed behaviour of the nickel, once released, that was entirely dependent on the phenomenon of adsorption on the iron and manganese hydroxides.     

The relationship between runoff and ground temperature in glacierized catchments in China

A single parameter index method, in which ground temperature and air temperature is the sole input variable, respectively, is used to evaluate and compare the glacial runoff in three typical glacier catchments, Dongkemadi glacier catchment in Tibetan plateau, Koxkar glacier catchment and the headwater catchment of Urumqi River catchment in Tianshan Mountains in West China. The method based on ground temperature is an attempt to evaluate glacier runoff in elevated terrains, as few studies have focused specifically on the association between glacier runoff and ground temperature. The results identify ground temperature versus a certain depth, which is a critical factor that affected glacier hydrological processes and showed that runoff data is much better correlated with ground temperature than air temperature. Especially, at the latter two catchments, the largest coefficients of exponential relationship R ² between glacier runoff and ground temperature are 0.9 and 0.83, respectively. The accuracy of the method makes it possible to estimate the glacier runoff with a certain depth ground temperature at a certain site, which may provide a new approach to evaluate the glacier runoff for areas where there is a lack of observation data.     

Assessment of heavy metal pollution in lake sediments of Katedan Industrial Development Area,Hyderabad, India

Spatial distribution and temporal trends studies were carried out at Katedan Industrial Development Area (KIDA) near Hyderabad, capital of Andhra Pradesh state, India under Indo-Norwegian Institutional Cooperation Program, to find out the extent of contamination in streams and lake sediments from the discharge of industrial effluents. Stream and lake sediment samples were collected from the five lakes in the study area and connecting water streams. The samples were analyzed by XRF spectrometer for toxic elements. The studies reveal that the stream sediments with in the KIDA and the impounded Noor Mohammed Lake down stream have high concentration of some of the toxic elements like chromium, nickel, lead, arsenic, zinc etc. The geology of the area indicates that the study area consists of residual soil of acidic rocks, which are predominantly of Archaean gneisses and granites having low to medium concentrations of chromium and nickel. The source of these high concentration of elements like lead 2,300 mg/kg, copper 1,500 mg/kg, arsenic 500 mg/kg, chromium 500 mg/kg etc. cannot be derived from the surrounding acidic rocks and may be attributed to the industrial effluents released in the ditches and random dumping of hazardous solid waste. It was observed that the metal concentrations increased in the streams during the dry season (pre-monsoon period). After the monsoon rains, the metal concentrations in the streams were reduced by half which may be due to dilution. The eroded sediments are deposited in the lake where very high concentrations were encountered. Overflowing of the lake will spread the contamination further downstream. The lake sediments will remain as a major source of contamination by desorption to the water phase regardless of what happens to the effluent discharge in the KIDA. However, some samples showed enrichment of lead, arsenic and nickel during post-monsoon, which were collected near the dumpsite due to the leaching of toxic elements from the dump site to the lakes. Some of the toxic elements like nickel and copper have not shown any dilution but have increased after the rains, which could be due to the leaching of arsenic from the dumpsite to the lake along with rainwater. Geochemical maps showing the distribution of heavy/trace elements in streams and lakes are prepared and presented in this paper. Effect of toxic elements on the health of the residents in the surrounding residential areas is also discussed.     

爆炸荷载作用下深埋圆形隧洞的饱和黏弹性土-衬砌系统动力响应

假定土骨架服从标准线性固体黏弹性本构关系,研究了深埋圆形隧洞的饱和黏弹性土-弹性衬砌耦合系统在轴对称爆炸作用下的瞬态动力响应。首先,基于饱和土的Biot模型和衬砌的弹性理论,通过引入势函数和Laplace变换,利用弹性衬砌和饱和黏弹性土界面处的连续性条件以及边界条件,得到饱和黏弹性土体和弹性衬砌位移、应力和孔隙水压力等在Laplace变换域中的解析解。其次,利用Laplace数值Crump逆变换得到耦合系统在时间域的动力响应,数值分析了不同土体模型下土体-衬砌耦合系统的径向位移和环向应力以及土体孔隙水压力等。结果表明：对不同土体模型的土体-衬砌耦合系统,其在爆炸载荷作用下的动力响应性态基本一致,但动力响应的振动周期和幅值等具有明显的差异。同时,对于饱和黏弹性土-弹性衬砌系统,土体黏性参数对土体径向位移和孔隙水压力有明显的影响,但对土体环向应力影响较小。     

Long-term seasonal rainfall forecasting: efficiency of linear modelling technique

Using the lagged (past) climate indices, including El Nino–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) as input parameters and long-term spring rainfall as outputs, calibration and validation of the linear multiple regression (MR) models have been performed. Since Australian rainfall varies both temporally and spatially, the analysis on the linear MR models was performed on regional scale. These models show the capability of linear MR technique for long-term predictions of Western Australian spring rainfall. The emphasis was given to assess the statistical correlations between Western Australian spring rainfall and dominating large-scale climate modes. The efficiency of linear modelling technique was evaluated to predict seasonal rainfall forecasting. At the same time, the Pearson correlation (R), mean absolute error, root-mean-square error and Willmott index agreement (d) were used to assess the capability of MR models. The models which fulfilled the limits of statistical significances were used for the prediction of future spring rainfall using independent data set. The results indicate that during calibration periods maximum achievable correlations varied from 0.47 to 0.53 for the selected stations. In regard to predict peaks and troughs of rainfall time series, it was found that correlations between predicted and actual peaks varied from 0.82 to 0.94 and between predicted and actual troughs varied from 0.53 to 0.91.