Salt Beds Research Articles

The Vendian–Cambrian Cyclometric Stratigraphic Scale for the Southern and Central Siberian Platform

Abstract —The general Vendian stratigraphic scale of Siberia, with the uncertain age of the Vendian base ranging from 600 to 630– 640 Ma in most of recent publications, remains worse constrained than the Cambrian scale, in which the boundaries of epochs and stages have been well defined. However, the imperfect classical stratigraphic division has been compensated by data on the cyclicity of the Vendian–Cambrian sedimentary section. The Vendian stratigraphy of the Siberian Platform and the related deposition history with cycles of sedimentation and gaps, as well as the hierarchy of sedimentation processes, can be inferred from the succession of alternating clastic, carbonate, and salt units. The cyclicity of geologic processes and their recurrence are attributed to periodic oscillatory motions of the crust. The ranks of these motions correlate with the cyclicity of sedimentary strata, including regocyclites, nexocyclites, and halcyclites separated by gaps. Each Vendian long-period oscillatory motion begins with a regocyclite and ends with a regional-scale gap. The Cambrian section includes one pre-Mayan regional gap at the end of the early Cambrian long-period cycle. Cambrian regocyclites are composed of carbonate subformations and formations in the lower part and alternating salt and carbonate beds in the upper part.

Alignment of saline springs with evaporite karst structures in northeast Alberta, western Canada: analogue for cretaceous hypogene brine seeps to the surface

Meteoric and glacial meltwater charged groundwater, mixed with dissolved salts from Devonian sources at depth, discharged as saline springs along topographic lows of the Athabasca River Valley, which downcuts into the Cretaceous Athabasca oil sands deposit in northeast Alberta, western Canada. These Quaternary saline seeps have TDS measurements, isotope signatures and other chemical characteristics indicative of the groundwater flows coming in contact with Prairie Evaporite (M. Devonian) salt beds, 200 m below the surface. Migrations up-section of groundwater with dissolved chloride and sulphate salts occurred along salt dissolution collapse breccia zones that cross-cut Upper Devonian limestone strata. Seeps discharged along the karstic Devonian limestone paleotopography, the unconformity surface flooring the Lower Cretaceous McMurray Formation. Saline to brine springs along the Athabasca River Valley have TDS measurements that can exceed 100,000 mg/L. Quaternary salt removal was insignificant compared to the voluminous removal of the 80-130 m thick salt section for 1000s km2 during the Early Cretaceous configuration of the Devonian paleotopography, which partially controlled depositional patterns of the overlying McMurray Formation, principal host rock of the Athabasca oil sands. Little is known of the storage or disposition of voluminous brines that would have resulted from this regional-scale removal of the salt beds below the Athabasca deposit during the Cordilleran configuration of the foreland Alberta Basin. Holocene dissolution trends and discharges at the surface as saline springs are proposed as a modern analogue for voluminous Early Cretaceous brine seeps to the surface along salt dissolution collapse breccia zones, concurrent with deposition of the McMurray Formation. This model links several characteristics of the McMurray Formation as responses to Aptian brine seeps to the surface. These include: (1) the emplacement of a drainage-line silcrete along the margins of the Assiniboia PaleoValley, now partially exhumed by the Athabasca River Valley, (2) distribution of brackish-water burrowing organisms, and (3) diagenesis of calcite-cemented sand intervals.

SALT PROCESSING AT THE NAKHICHEVAN SALT DEPOSIT

One of the topical issues is the study of the formation conditions, geological structure, chemical composition and methods of development of the "Duzdag" salt deposit, formed in the Babek region of the Nakhchivan depression on the territory of Azerbaijan, in order to meet the salt needs of the population. The field is divided into two sections: southern - Nakhchivan and Sust, located 4.5 km north-west of it. The physical and mechanical properties of both sections are close to each other. Losses are allowed during field development due to the fact that salt layers alternate with clay layers. The constantly growing demand for salt has predetermined the need to develop more advanced and progressive production methods based on the mechanization of technological processes, the use of new technologies and world experience. Depending on the formation of salt deposits, different methods of salt extraction are used in world practice. The main method of production of table salt in the world should be its extraction in the form of a solution and evaporation in the sun. The share of each of these methods is about 35%, and about 30% of the salt is extracted from an underground mine. The productive layer of the Nakhchivan rock salt deposit is 93-95% halite and is of high quality. The excess content of clay minerals in the field forces them to be used only in animal husbandry. Frosts drilled in the Nakhchivan rock salt deposit can be widely used in the treatment of liver diseases. The mountain has 130 million tons of natural salt reserves that are effective in treating respiratory ailments. Since the ice is horizontal, patients adapt to the underground part. To open new production facilities and treatment facilities in Duzdag, it is necessary to continue the installation of equipment that meets modern standards, the introduction of mines into a fully automated, controlled technological regime, equipped with a modern ventilation system. Keywords: Nakhchivan salt deposit, processing methods, salt beds.

Mechanism of deformation in rock mass surrounding intersection of mine shaft and salt bed

A bed of rock salt in Komsomolsky Mine occurs in sedimentary strata enclosing cage and skip shafts. When water enters rock salt via underground excavations, boreholes and fractures, rock salt can dissolve and wash out, and voids appear in rock mass. Voids at the lining and rock interface should be eliminated so that never re-appear or grow during shaft operation. Materials used to eliminate voids should ensure stable mechanical linkage both with enclosing rocks and lining. Assessment and analysis of geomechanical processes induced by leaching need monitoring of deformations in a shaft. To this effect, one of the simplest and most informative methods is arrangement of an observation station directly in the shaft lining to measure varying distances between check points. The article briefly describes activities aimed to eliminate voids using different composition grouts. From the analysis of monitoring data, the deformation mechanism is described, and the interaction between different deformation stages and grouting steps is determined. The authors appreciate participations of experts M. P. Sergunin, I. A. Shishkina, A. K. Ustinov, V. V. Tsatskin, V. S. Orlov.

Overview of current compressed air energy storage projects and analysis of the potential underground storage capacity in India and the UK

Compressed air energy storage (CAES) is an established and evolving technology for providing large-scale, long-term electricity storage that can aid electrical power systems achieve the goal of decarbonisation. CAES facilities often utilise large underground storage caverns to ensure high capacity systems. This results in the need of locations with suitable geological features to develop a CAES plant. This paper examines recent and ongoing large-scale CAES projects and presents candidate methods of storing high pressure air using underground features. An assessment of the overall potential for CAES in India is presented by examining its geological features and locations with the greatest potential for CAES plants are determined. This is combined with an analysis of the renewable electricity generation potential in India to identify candidate areas for renewable generation and CAES integrated systems. Up to 1.05% of Indian land area is deemed suitable for CAES plant development and if fully utilised would be sufficient to meet the energy storage needs of India, however, practically a very small fraction of the total suitable land that could be developed so other competing energy storage technologies should be considered. Conversely, the UK possesses a very good potential for CAES, enough to greatly exceed necessary energy storage, owing to the abundance of salt beds not present in India. For CAES to garner serious consideration in India, aquifer storage based CAES needs to be demonstrated.

Construction Progress of Deep Underground Salt Cavern Gas Storage and Challenges of its Drilling and Completion Technology

With the rapid development of the national economy and the increasing demand for energy, and the acceleration of natural gas storage strategies, underground gas storage has become more and more important in China’s oil and gas consumption and energy safety. Underground salt cavern gas storage has many advantages and is very suitable for gas storage and peak shaving。However, most of the underground salt rocks in China are layered salt beds, and some of the salt beds are deeply buried. This article introduces the development history of deep underground salt cavern gas storage and the technical challenges faced in the process of drilling and completion of salt cavern construction.

Change Detection of Landuse-landcover in and around Cox’s Bazar-Teknaf Coastal Area of Bangladesh Using Satellite Images

The prime objective of this study is to detect changes of the biophysical resources (or landuse-landocver) of the Cox’s Bazar-Teknaf area from 1999 to 2015 using Landsat TM/ETM+/OLI sensors images after applying classifications and indices approaches. The normalized differential vegetation index (NDVI) result showed that water bodies reduced by about 20% of the study area from 1999 to 2015. Bared land or beach decreased by 6% from 1999 to 2005 and then increasing trend is observed in this study from 2005 to 2015. Mixed land was more or less an increasing trend in this study area. Vegetation cover increased from 1999 to 2005 and then suddenly decreased a lot from 2009 to 2015. The declining trend of water bodies is mostly in the northern part of the study area, which is mostly shallow area where shrimp or salt farms exist. The result of normalized differential water index (NDWI) showed that the water bodies decreased from 1999 to 2015 about 10% of the study area. Land area was increased from 1999 to 2005 and then increased a little from 2005 to 2009 and afterward it decreased. The normalized differential salinity index (NDSI) result shows that the area of non-saline zone increased from 1999 to 2015. Low saline zones reduced from 1999 to 2005 but it increased after 2005 due to absence of high and medium salinity signature from NDSI value. The low saline zone is mostly in the northern side of Cox’s Bazar where shrimp farms or salt bed exist. In unsupervised thematic maps, the water bodies increased in this region from 1999 to 2009 and then declined again. The declining trend of water bodies indicates the erosion activities from 1999 to 2009. The fallow lands including beach also decreased from 2005 to 2015, indicates more agricultural activities including fisheries, salt production in this study area. On the other hand, the vegetated region decreased but settlements area including vegetation increased in this area. In supervised thematic map, the result showed that the shrimp cultivation and salt bed increased in this region from 1999 to 2015 and agricultural land has decreasing trend. On the other hand, the vegetated region was ups and down trend from 1999 to 2009. The study indicates that the Landsat images are quite efficient to map biophysical resources of the study area with various techniques.
 The Dhaka University Journal of Earth and Environmental Sciences, Vol. 8(1), 2019, P 1-9

Origin and Evolution of Gas in Salt Beds of a Potash Mine

Abstract. In order to better understand both the fixation and migration of gases in evaporites, investigations were performed in five horizontal boreholes drilled in an underground potash seam. One of the five boreholes was pressurised with Ar and the pressure signal and chemical gas composition were then monitored in the other holes. A further gas sample from a separate borehole was characterised for the chemical composition and for noble gas and carbon isotopic compositions to conclude on the origin and evolution of the gas in the salt rocks. Additionally, in order to determine the total gas amount in the salt rocks, a potash-bearing salt sample was dissolved in water and from the mass of 1 kg salt sample, 9 cm(STP)3 gas was liberated. Due to the relatively large permeability of the disturbed salt rocks (4×10-17 to 4×10-18 m2), which is about 3–4 orders of magnitude higher than in undisturbed salt rocks, we assume that the migration of injected Ar most likely takes place along micro-cracks produced during the mining process. The geogenic gas concentrations found in the observation holes correlate directly to the Ar concentration, suggesting that they were stripped from the rocks in between the holes. According to the He-isotopes (0.092 Ra), a small contribution of mantle gas can be found in the geogenic salt gas. The δ13CCO2-isotopic composition (−7.8 ‰ to 6.7 ‰) indicates a magmatic source, whereas 13C∕12C of CH4 (−22.2 ‰ to −21.3 ‰) is typical for a thermogenic gas. We assume that CO2 and CH4 are related to volcanic activity, where they isotopically equilibrated at temperatures of 513 to 519 ∘C about 15–16 Ma ago.

Characteristics, genetic mechanism and oil & gas exploration significance of high-quality sandstone reservoirs deeper than 7000 m: A case study of the Bashijiqike Formation of Lower Cretaceous in the Kuqa Depression, NW China

Ultra-deep clastic reservoirs generally have poor physical properties and low single-well productivity, but Well BZ9, which is newly drilled in the Kuqa Depression of Tarim Basin, NW China, encounters a thick high-quality reservoir in the Bashijiqike Formation of Lower Cretaceous deeper than 7600 m and produces a high-yield industrial gas flow. In order to reveal the characteristics and genesis of the Bashijiqike Formation reservoir and reduce the exploration risk of ultra-deep oil and gas layers, we discussed its characteristics, genetic mechanism and oil & gas exploration significance based on cores, well logging and experimental analysis, combined with regional temperature–pressure conditions and burial evolution history. The following research results were obtained. First, the rock types of ultra-deep reservoir of the Bashijiqike Formation in this area are medium- and fine-grained feldspathic litharenite and lithic arkose with point-line contact between grains, and its reservoir space is dominated by primary intergranular pores. At present, it is still at its middle diagenetic stage. Second, different from other ultra-deep fractured low-porosity sandstone reservoirs, this set of ultra-deep reservoir is a pore-type reservoir with porosity of 4–13%, permeability of 0.1–50.0 mD and better porosity and permeability correlation. Third, during the sedimentation of the Bashijiqike Formation, thick sand bodies of delta front were widely developed, medium- and fine-grained sandstones accounted for more than 85% and grains had strong compressive capacity. After that, this reservoir experienced long-term shallow burial during the early–medium stage and rapid deep burial during the late stage, and the burial compaction effect was weaker. During the late stage, a canopy structure was formed from the overlying Paleogene thick gypsum salt bed due to thrust and compression, and it further suppressed vertical compaction. In the meantime, the study area was far from the orogenic belt and the structural transition zone, so the lateral compressive stress was weak. Therefore, the primary intergranular pores were preserved in large quantities. It is concluded that coarse lithology, weak compaction and low tectonic stress are the key factors to the development of this ultra-deep high-quality reservoir. In addition, the development of large-scale effective reservoirs deeper than 7000 m provides favorable material conditions for the high-abundance enrichment of natural gas and the reserves of trillion cubic meters in the Kuqa Depression, and the oil and gas exploration potential is huge.

The effect of solvent chemistry on potassium dissolution extraction from low-grade solid potash ore in Qarhan Salt Lake, China

Qarhan Salt Lake contains approximately 296 million tonnes of low-grade solid potash ores. The exploitation and utilization of this low-grade solid potash ore represents the fundamental framework for the sustainable development of Qarhan Salt Lake's potash fertilizer industry. It also alleviates the shortage of potash resources of China. In this paper, we studied species and characteristics of the low-grade solid potash minerals from the Bieletan area in Qarhan Salt Lake and analyzed the solvent that affected the dissolution extraction of low-grade solid potash ore. The major potash minerals in the Bieletan Subbasin are polyhalite, carnallite and sylvite. An effective solvent for dissolving these potash minerals is prepared with old bittern and water from Senie Lake, which contains average Mg2+, Cl−, K+ and Na+ values as 3.69%, 15.23%, 0.23% and 1.60%, respectively. Theoretically calculating by PHREEQC shows that the chemical composition of the solvent is nearly in equilibrium with halite and far away from equilibrium with polyhalite, carnallite and sylvite. This solvent does not significantly cause dissolution and precipitation of halite. Thus its influence on the porosity and permeability of the salt bed in the strata is minimum, which enables the solvent to flow to deeper and farther areas and dissolve more low-grade solid potash ores, showing excellent ability to selectively dissolve K+-bearing saline minerals. After dissolution extraction experiments, the concentration of K+ in the solvent increased from 0.23% to 0.68%, showing the higher-dissolution effect of the solvent for the low-solid potash ores. Hence, the solvent plays an important role in developing of the low-grade potash ores.

Prediction of shallow salt cavity geometry from surface subsidence configurations

Physical model tests are used to simulate surface subsidence induced by shallow salt cavity occurred at the interface between salt bed and overlying soil formation. Uniform fine sand with properties similar to the overburden soil is used in the models. The width and depth of sinkhole or subsidence trough induced under various cavity widths, heights, and depths are measured using 3-D laser scanner. The results indicate that for relatively shallow cavity, the increase of sinkhole depth closely relates to the increase of cavity height. The extent of subsidence area is sensitive to depth and width of the cavity. The maximum subsidence is not sensitive to cavity depth. The physical model results are fitted to empirical equations. They can be used to estimate the cavity height and width from the subsidence configurations under similar geologic conditions.

Reservoir accumulation conditions and key exploration & development technologies for Keshen gas field in Tarim Basin

The Keshen gas field is located in the central part of Kuqa foreland thrust belt in Tarim Basin, and is another large gas field discovered in Kuqa depression after Kela 2 gas field. Since the breakthrough in 2008, a number of large and medium scale gas reservoirs including Keshen 2, Keshen 5 and Keshen 8 have been discovered, that are characterized by ultra depth, ultra-high pressure, ultra-low porosity, ultra-low permeability, high temperature and high pressure. With natural gas geological reserves of nearly trillion cubic meters and production capacity of nearly 5.5 billion cubic meters, the Keshen gas field is the main natural gas producing area in Tarim Oilfield. The Keshen gas field is located in a series of thrusting imbrication structures in the Kelasu structural belt of Kuqa foreland thrust belt. The salt roof structure, plastic rheology of salt beds and pre-salt faulted anticlinal structure constitute the large wedge-shaped thrust body. The thick delta sandstone of the Cretaceous Bashijike Formation is widely distributed, and it forms the superior reservoir-caprock combination with overlying Paleogene thick gypsum-salt bed. The deep Jurassic-Triassic oil and gas migrate vertically along fault system formed in Late Himalaya, break through the thick Cretaceous mudstone and move laterally along the fracture system of the pre-salt reservoirs, to form anticline and fault anticline high pressure reservoir groups. Through near ten years of studies, the three-dimensional seismic acquisition and processing technology for complex mountainous areas, extrusion salt-related structural modeling technology and fractured low-porosity sandstone reservoir evaluation technology have been established, which lay a foundation for realization of oil and gas exploration objectives. Logging acquisition and evaluation technology for high temperature, high pressure, ultra-deep and low-porosity sandstone gas reservoirs, and efficient development technology for fractured tight sandstone gas reservoirs have been developed, which provide a technical support for efficient exploration & development and rapid production of the Keshen gas field.

Performance of SrBr2·6H2O based seasonal thermochemical heat storage in a novel multilayered sieve reactor

The salt hydrate-based thermochemical heat storage (TCHS) system, based on a reversible solid-gas chemical reaction, is currently a key technique used to store heat for later discharge. Strontium bromide hexahydrate (SrBr2·6H2O) is one of the most promising candidate materials in seasonal heat storage for residential heating due to its lower desorption temperature. This study develops and numerically investigates a novel multilayered sieve reactor that can promote dehydration and hydration reactions. This paper focuses on the interaction between the porous reactive salt beds and the vapor in an open system. The required time to totally dehydrate and hydrate the salt beds are approximately 1180 min and 940 min, respectively. The effects of various operating conditions such as input temperature, inlet velocity, and relative humidity of fluid on charging and discharging are studied, as well as the influence of thermal conductivity, permeability and kinetic factors. For instance, the reaction kinetic factor Rkin = 1.0 × 10−4 is a threshold in this model. The optimized salt beds reduce dehydration time by 11.4% (130 min). High volumetric thermal powers are obtained for the multilayered sieve reactor, although the values decrease with the degree of conversion. The results indicate that the thermal efficiency η, thermal coefficient of performance (COPth), and exergy coefficient of performance (COPex) of charging are 85.2%, 72.4%, and 21.3%, respectively, and the corresponding values for discharging are 94.5%, 71.5%, and 21.1%, respectively, for the model studied.

Structure and mineralogical composition of the tuff horizon of Petrikov potash deposit

Integrated data of the structure and mineralogical composition of the marking tuff horizon in the Upper-Devonian bed of the North-Shestovich synclinal zone are presented in this paper. Dependence of the tuff bed structure on the volcanic activity stage is revealed. Find out that the prevailing mineral of tuff is the structure-ordered illite 1M. Marked tuff horizon is situated inside the Upper-Devonian salt bed within Petrikov synclinal zone and comes up into the overlaying clay-marl formation of the surrounding geological beds.

Assessment of open thermochemical energy storage system performance for low temperature heating applications

Owing to their high energy storage density, thermochemical energy storage (TCES) systems are promising alternatives for seasonal storage of heat, which can be charged with solar thermal energy during the summers, and employed for space heating application in the winter season. In the present work, an open TCES system with a single reactive bed of solid strontium bromide salt reacted with moist air flow is considered. A two-dimensional model considering diffusion effect of water vapour inside the reactive bed is developed and validated. Parametric studies are carried out for both the charging as well as the discharging phases using the two-dimensional model to evaluate the effect of inlet air temperature, inlet partial pressure of water vapour and inlet air flow rate on the performance of the open TCES system. A case study is carried out for the discharging phase for a single night during the winter season for Pune, India. The use of a suitable humidity control at the inlet of the reactive bed is found to increase the energy saving by 18.9% and is found to be an effective way in maintaining the temperature of the air at the outlet of the reactive bed within comfortable limits for space heating application.

An attempt to apply a slag binder with zeolite in mining construction. Durability and hardness

The paper presents comparative results of strength tests on mortars, hardness of pastes and their microscopic observations. The focus was on alkali activated ground granulated blast furnace slag (GGBFS) to which the zeolite was introduced. Zeolite positively affects the rheological properties, densifies the microstructure by reducing its permeability and binds Ca(OH)2. It causes lower susceptibility of the binder to corrosion, which can be affected by mine mineralized waters or brines flowing from the salt beds. To increase the mechanical properties, polymer scattered reinforcement was used, which does not corrode in contact with saline waters, contrary to steel reinforcement. The paper presents the results of: bending strength and compression strength of mortar bars made of slag (S2), slag with zeolite (S3), slag with zeolite and polymer fibers (S5); the Vickers indenter tests results of slag pastes of S2 and S3 as well, up to 90 days of hydration. The 90 day compressive strength was 64.0 MPa; 27.7 MPa and 64.7 MPa, and bending strength: 6.4 MPa; 2.9 MPa and 6.0 MPa, respectively for S2, S3, S5. The Vickers indenter test at HV 1 was as follows: on average 27.04 MPa and 36.69 MPa, respectively for S2 and S3. Microstructure observations were carried out in SEM. The obtained results require further research work.

Airflow measurement across negatively infiltration processed porous aluminum structures

Detailed structural characterization and experimental measurement of airflow across open‐celled aluminum foam structures with near‐spherical cells varying in pore sizes and interstices are presented herein. The aluminum foam structures were produced by infiltrating liquid aluminum into convergent gaps created by packed beds of near‐spherical hydrosoft salt beds varying in particle sizes, packing densities, and infiltration pressures. A quantitative assessment of the unit pressure drops developed across these structures show that viscous and inertial terms of these structures were observed to greatly depend on the shape and structural macroscopic parameters of the porous medium. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1355–1364, 2019

CALIPSO Recordings and Categorization of Atmospheric Aerosols over the Urmia Lake

The Urmia Lake is suffering from a severe drought scenario that started in recent decades. The lake has lost almost 88% of its surface area in comparison to its value in 1995. This has left a bed of salt around the lake, that has the potential to disperse a significant amount of aerosols (dust and salt) into the atmosphere. We use the recordings of the CALIPSO satellite to investigate the optical parameters of atmospheric aerosols over the Urmia Lake. For this purpose, the aerosol optical depth (AOD) and the particulate depolarization ratio (PDR) at 532 nm have been selected from the whole available recordings of the CALIPSO. To distinguish between the atmospheric particles which are originating from the lake bed and those that are transported from the surrounding sources to the lake area, the PDR has been categorized for two altitude ranges, i.e., from the ground level up to 2 km above the mean sea level (amsl) and above 3 km amsl. Investigating the variations of the PDR at these two altitude ranges, provides information about the type of atmospheric particles at different times of the year. Although it is not easy to distinguish between the transported dust layers and atmospheric particles from the lake bed, it seems that the Urmia Lake is mostly active in the driest times of the year, i.e., June to October. Also, it seems that the particles which are originating from the lake, are mostly dry salt particles, where their corresponding PDR is 0.16 ± 0.05.

Evolution of sinkholes over Wink, Texas, observed by high-resolution optical and SAR imagery

Two caprock and cover collapse sinkholes, Wink Sinks #1 and #2, in Winkler County, Texas, collapsed in 1980 and 2002, respectively. They are located in a region underlain by the Salado Formation on the eastern edge of the Delaware Basin. The sinkhole collapses were associated with intense hydrocarbon drilling and production activities in the Hendrick oilfield. Production records and prior investigations imply the sinkholes developed after salt dissolution due to freshwater intrusion, cavity formation, roof failure, and successive upward cavity migration. High-resolution (1 m) aerial photography shows the ensuing expansion of Wink Sink #2 from 2002 through 2010 and relative stability of the ground surface after 2010. Very high-resolution (25 cm) staring spotlight mode TerraSAR-X reveals the spatiotemporal details of Wink sinkhole deformations. The vicinities around the two existing sinkholes (Wink Sinks #1, #2) deformed at a rate of 5 cm/yr in line-of-sight (LOS) direction from October 2015 to March 2016, and the deformation was possibly caused by the gradual deposit of the debris from overlying unconsolidated Alluvium and Santa Rosa sandstones infilling the cavity after the sinkhole collapse. Specifically, the largest deformation of 53 cm/yr in LOS direction was found 1 km east of Wink Sink #2. Our study suggests that severe drought in 2011 widened and created fractures as well as ground fissures in the rocks overlying and underlying the salt formation due to the increased effective stress. Fractures, ground fissures, and the abandoned unplugged boreholes or improperly completed wells opened one or more vertical pathways of freshwater from groundwater flow and precipitation toward the salt bed, finally causing the rapid salt dissolution and the opening of new cavities. To explain the onset of a rapid subsidence near the Wink sinkholes, our study considers the combined effect of natural perturbation (i.e., drought, rock fractures, ground fissures, subsurface drainage, precipitation) and anthropogenic effects (i.e., improper well control). Our method to explore high-resolution imagery can be applied to characterize the sinkhole deformation and mitigate sinkhole-related geohazards.

Degradation of Polycyclic Aromatic Hydrocarbons by Moderately Halophilic Bacteria from Luzon Salt Beds.

Background.Polycyclic aromatic hydrocarbons (PAHs) are common environmental contaminants which are highly toxic due to their carcinogenic and mutagenic effects. They are released into the environment by incomplete combustion of solid and liquid fuels, accidental spillage of oils and seepage from industrial activities. One of the promising processes mitigating PAHs is through biodegradation. However, conventional microbiological treatment processes do not function well at high salt concentrations. Hence, utilization of halophilic bacteria should be considered.Objectives.This study aimed to assess the ability of halophilic bacteria isolated from local salt beds in Pangasinan and Cavite, the Philippines, to degrade PAHs pyrene, fluorene and fluoranthene.Methods.Polycyclic aromatic hydrocarbon-tolerant halophilic bacteria collected from two sampling sites were phenotypically characterized, molecularly identified and tested to determine their potential to degrade the PAHs pyrene, fluorene and fluoranthene at a hypersaline condition. Best PAH degraders were then assayed to identify the optimal degradation using such parameters as pH, temperature and PAH concentration. Testing for enzyme degradation was also done to determine their baseline information. Extraction and analysis of degraded PAHs were performed using centrifugation and UV-vis spectrophotometry.Results.Twelve isolates from both collection sites tolerated and grew in culture with selected PAHs. These were identified into four genera (Halobacillus, Halomonas, Chromohalobacter, and Pontibacillus). Selected best isolates in a series of biodegradation assays with the above-mentioned parameters were Halobacillus B (Collection of Microbial Strains (CMS) 1802) (=trueperi) (Gram-positive) for pyrene and fluoranthene, and Halomonas A (CMS 1901) (Gram-negative) for fluorene. Degrader biomass and PAH degradation were invariably negatively correlated. Qualitative tests with and without peptone as a nitrogen source implied enzymatic degradation.Discussion.Polycyclic aromatic hydrocarbons utilized by these halophilic bacteria served as a sole source of carbon and energy. Implications of biodegradation of the two best isolates show that high molecular weight (HMW) (4-ring) pyrene tends to be degraded better by Gram-positive bacteria and low molecular weight (3-ring) fluorene by Gram-negative degraders.Conclusions.Halophilic bacteria constitute an untapped natural resource for biotechnology in the Philippines. The present study demonstrated their potential use in bioremediation of recalcitrant hydrocarbons in the environment.Competing Interests.The authors declare no competing financial interests.