The presence of environmental fluoride and its impact on human health is well documented. When consumed in adequate quantity, fluoride prevents dental caries, assists in the formation of dental enamels, and prevents deficiencies in bone mineralization. At excessive exposure levels, ingestion of fluoride causes dental fluorosis skeletal fluorosis, and manifestations such as gastrointestinal, neurological, and urinary problems. The distribution of fluoride in the environment is uneven and largely is believed to derive from geogenic causes. The natural sources of fluoride are fluorite, fluorapatite, and cryolite, whereas anthropogenic sources include coal burning, oil refining, steel production, brick-making industries, and phosphatic fertilizer plants, among others. Among the various sources of fluoride in the environment, those of anthropogenic origin have occasionally been considered to be major ones. The gourndwater is more susceptible to fluoride accumulation and contamination than are other environmental media, primarily because of its contact with geological substrates underneath. The high fluoride concentration in water usually reflects the solubility of fluoride (CaF₂). High concentrations are also often associated with soft, alkaline, and calcium-deficient waters. The fluoride compounds that occur naturally in drinking water are almost totally bioavailable (90%) and are completely absorbed from the gastrointestinal tract. As a result, drinking water is considered to be the potential source of fluoride that causes fluorosis. Because the bioavailability of fluoride is generally reduced in humans when consumed with milk or a calcium-rich diet, it is highly recommended that the inhabitants of fluoride-contaminated areas should incorporate calcium-rich foods in their routine diet. Guidelines for limiting the fluoride intake from drinking water have been postulated by various authorities. Such limits are designed to protect public health and should reflect all fluoride intake sources, including dietary fluoride. The toxicological risks posed by fluoride could be better understood if epidemiological surveillance for dental and skeletal fluorosis would be systematically conducted in fluoride-affected areas. Such input would greatly improve understanding of the human dose-response relationship. Such surveillance of potentially high fluoride areas is also important because it would help to delineate, much earlier, the remedial measures that are appropriate for those areas.

Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been combined to yield powerful new insights to reservoir tar mats. The asphaltene nanoscience model, the modified Yen model, also known as the Yen−Mullins model, has enabled development of the industry's first predictive equation of state for asphaltene concentration gradients. This equation of state (EOS) is a modified Flory−Huggins regular solution model for the asphaltene part that has been referred to as the Flory−Huggins−Zuo (FHZ) EOS for asphaltene concentration gradients in oil reservoirs. Measurement of these gradients using "downhole fluid analysis" coupled with analysis using the FHZ EOS has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The EOS model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple formthe gravity term only for low GOR black oils and heavy oilsand heavy oils are shown to exhibit enormous asphaltene concentration gradients in contrast to predictions from conventional models. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs. Two types of tar mats are discussed: one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a heavy oil column due to an exponential increase in viscosity with asphaltene content. Both types of tar mats are consistent with the Yen−Mullins model of asphaltenes within the FHZ EOS analysis discussed herein. The predictions are in good agreement with the laboratory and field observations, and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading and tar mat formation in oil reservoirs by integrating the Yen−Mullins model and the FHZ EOS with DFA technology.

Participatory variety selection (PVS) for the selection and testing of salt tolerant varieties/genotypes and breeding accessions of rice was conducted at Central Soil SalinityResearch Institute, Regional Research Station, Lucknow, Uttar Pradesh, India from 2001 to 2007. This aimed to identify high yielding, adaptable, and acceptable rice cultivars for sodic soils through farmers' participation. Typically, plant breeders develop varieties isolated from active farmers and release varieties that are most productive under ideal conditions; often they are not suitable for marginal farm conditions, like sodic lands. Therefore, PVS facilitates development of varieties suitable for marginal soils and farmers' interests. A collection of modern rice varieties/genotypes was screened and evaluated under researcher-managed trials during 2001. From 2002 to 2008, farmers became a part of the variety/genotype selection and testing process in order to incorporate their preferences, which were crucial for the large-scale adoption of the selected variety/genotype. With farmer support, genotype CSR-89IR-8 was identified as superior and not only performed better in different locations in the state of Uttar Pradesh, but was also readily adopted Downloaded by [University of Connecticut] at 06:57 01 April 2015 428 Y. P. Singh et al. by many farmers in sodic areas. This genotype is tolerant to sodicity (up to pH 2 ∼9.9) and yields more grain in sodic soil than other varieties/genotypes tested. In view of the successful testing and large scale adoption of CSR-89IR-8 in the target sodic areas of Indo-Gangetic plains, this genotype was officially released as variety CSR 43 by Uttar Pradesh State Variety Release Committee in 2011for widespread cultivation. The successful use of PVS in these sodic environments convinced researchers, stakeholders, and partner organizations to more broadly adopt this approach for new rice variety development, particularly for other salt affected areas.

Fluoride is a chemical element that is found most frequently in groundwater and has become one of the most important toxicological environmental hazards globally. The occurrence of fluoride in groundwater is due to weathering and leaching of fluoride-bearing minerals from rocks and sediments. Fluoride when ingested in small quantities (<0.5 mg/L) is beneficial in promoting dental health by reducing dental caries, whereas higher concentrations (>1.5 mg/L) may cause fluorosis. It is estimated that about 200 million people, from among 25 nations the world over, may suffer from fluorosis and the causes have been ascribed to fluoride contamination in groundwater including India. High fluoride occurrence in groundwaters is expected from sodium bicarbonate-type water, which is calcium deficient. The alkalinity of water also helps in mobilizing fluoride from fluorite (CaF2). Fluoride exposure in humans is related to (1) fluoride concentration in drinking water, (2) duration of consumption, and (3) climate of the area. In hotter climates where water consumption is greater, exposure doses of fluoride need to be modified based on mean fluoride intake. Various cost-effective and simple procedures for water defluoridation techniques are already known, but the benefits of such techniques have not reached the rural affected population due to limitations. Therefore, there is a need to develop workable strategies to provide fluoride-safe drinking water to rural communities. The study investigated the geochemistry and occurrence of fluoride and its contamination in groundwater, human exposure, various adverse health effects, and possible remedial measures from fluoride toxicity effects.

In the present study, a total of 53 promising salt-tolerant genotypes were tested across 18 salt-affected diverse locations for three years. An attempt was made to identify ideal test locations and mega-environments using GGE biplot analysis. The CSSRI sodic environment was the most discriminating location in individual years as well as over the years and could be used to screen out unstable and salt-sensitive genotypes. Genotypes CSR36, CSR-2K-219, and CSR-2K-262 were found ideal across years. Overall, Genotypes CSR-2K-219, CSR-2K-262, and CSR-2K-242 were found superior and stable among all genotypes with higher mean yields. Different sets of genotypes emerged as winners in saline soils but not in sodic soils; however, Genotype CSR-2K-262 was the only genotype that was best under both saline and alkaline environments over the years. The lack of repeatable associations among locations and repeatable mega-environment groupings indicated the complexity of soil salinity. Hence, a multi-location and multi-year evaluation is indispensable for evaluating the test sites as well as identifying genotypes with consistently specific and wider adaptation to particular agro-climatic zones. The genotypes identified in the present study could be used for commercial cultivation across edaphically challenged areas for sustainable production.

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Reservoir fluid geodynamics (RFG) has recently been launched as a formal technical arena that accounts for fluid redistributions and tar formation in reservoirs largely after trap filling. Elements of RFG, such as analysis of biodegradation, have long been in place; nevertheless, RFG is now strongly enabled by recent developments: 1) downhole fluid analysis (DFA) allows routine elucidation of reservoir fluid gradients, 2) the development of the first equation of state for asphaltene gradients allows identification of equilibrium vs. geodynamic processes of reservoir fluids and 3) RFG analyses of 35 oilfields systematize a multitude of RFG processes and show their direct impact on wide-ranging production concerns. Thermodynamic analyses identifying reservoir fluid geodynamic processes rely heavily on measurement of fluid gradients to avoid ambiguous interpretations. The unique role of asphaltene gradients and their integration with other data streams are the focus herein. RFG oilfield studies have repeatedly shown that analyses of asphaltene gradients are critical to proper evaluation of RFG processes. Naturally, any reservoir concern that directly involves asphaltenes such as heavy oil, viscosity gradients, asphaltene onset pressure, bitumen deposition, tar mat formation, and indirectly, GOR gradients are strongly dependent on asphaltene gradients. Moreover, as shown in numerous case studies herein, asphaltene gradients can be measured with accuracy and the corresponding thermodynamic analyses allow explicit identification of RFG processes not traditionally associated with asphaltenes, such as analysis of connectivity, fault block migration, baffling, spill-fill mechanisms and many others discussed below. In turn, these processes imply other corroborative reservoir and fluid properties that can then be confirmed. Crude oil chemical compositional data, such as ultrahigh resolution two-dimensional gas chromatography, combined with geochemical interpretation, is highly desirable for understanding RFG processes. Nevertheless, biomarkers and other fluid properties often exhibit small gradients relative to standard deviations (except with biodegradation) but often can still corroborate specific RFG processes. In general, integration of fluid gradient analysis with other data streams including petrophysics, core analysis, stratigraphy, geology and geophysics is critical; nevertheless, which integration is most needed depends on particular reservoir attributes and RFG processes that are in question. Examples of data integration are shown for ten reservoirs undergoing various fluid geodynamic processes. Asphaltene gradient analysis is relatively new, yet it is essential for characterization of RFG processes.