Distribution of Arsenic in Fresh and Weathered Rocks in Sri Lanka

2021 ◽  
Author(s):  
U.de S. Jayawardena
Keyword(s):  
Sri Lanka ◽  
Arsenic Concentration ◽  
Residual Soil ◽  
Residual Soils ◽  
Minor Elements ◽  
Geological Processes ◽  
Arsenic Distribution ◽  
Weathered Rocks ◽  
Parent Rocks ◽  
Fresh Rock

Abstract This study was carried out to determine the distribution of arsenic, which may slowly harm human health, in the weathered rocks of different parent rocks in the country. 293 samples were collected from different crystalline rocks and in-situ weathered formations above the particular parent rock in 50 localities. Selected minor elements (including arsenic) were analysed by X-ray fluorescence spectrometry on RIGAKU KG-X system (Japan). Results indicated that the maximum arsenic amount in the fresh rock was 12 and 48 ppm in completely weathered rocks. About 86.9% of fresh rocks showed less than 5 ppm of arsenic, while 89.8% of their weathered grades showed the arsenic concentration to be less than 10 ppm. Average arsenic in all fresh rock samples was 3.5ppm (lowest); it was 7.6 ppm (highest) in residual soils. This is the normal condition of arsenic distribution worldwide. Under this condition, the arsenic concentration in natural groundwater in the residual soil areas should be below the acceptable limit. Therefore, the amount of arsenic released from parent rocks and their weathered products due to natural geological processes is very low in Sri Lanka.

Macrostructural and Microstructural Properties of Residual Soils as Engineered Landfill Liner Materials

2021 ◽  
Author(s):  
Lee Li Yong ◽  
Vivi Anggraini ◽  
Mavinakere Eshwaraiah Raghunandan ◽  
Mohd. Raihan Taha
Keyword(s):  
Tap Water ◽  
Chemical Precipitation ◽  
Soil Samples ◽  
Residual Soil ◽  
Diffuse Double Layer ◽  
Microstructural Properties ◽  
Residual Soils ◽  
Soil Leachate ◽  
Landfill Liner ◽  
X Ray

ABSTRACT This study assessed the performance of residual soils with regard to their macrostructural and microstructural properties and compatibility with leachate in pursuit of exploring alternative cost-effective and efficient landfill liner materials. A series of laboratory investigations was conducted on three residual soil samples by using tap water and leachate as permeation fluid to achieve the objectives of the study. The zeta potential measurements revealed that the presence of multivalent cations in the leachate decreased the diffuse double layer (DDL) thickness around the soil particles. The reduced DDL thickness caused a decrease in Atterberg limits of soil-leachate samples and changes in the classification of fine fractions. Additionally, the effects of pore clogging attributed to chemical precipitation and bioclogging were responsible for the reduction in measured hydraulic conductivities of soil-leachate samples. These effects can be clearly observed from the field-emission scanning electron microscopy images of soil-leachate samples with the appearance of less visible voids that led to a more compact and dense structure. The formation of new non-clay minerals and associated changes in the Al and Si ratio as reflected in the x-ray diffraction diffractograms and energy-dispersive x-ray analyses, respectively, were attributed to the effects of chemical precipitation. This study concluded that S1 and S2 residual soil samples are potential landfill liner materials because they possess adequate grading characteristics, adequate unconfined compressive strength, low hydraulic conductivity, and good compatibility with leachate. In contrast, the S3 sample requires further treatment to enhance its properties in order to comply with the requirements of landfill liner materials.

Small strain stiffness for granite residual soil: effect of stress ratio

2021 ◽  
Author(s):  
Xianwei Zhang ◽  
Xinyu Liu ◽  
Lingwei Kong ◽  
Gang Wang ◽  
Cheng Chen
Keyword(s):  
Stress Ratio ◽  
Small Strain ◽  
Residual Soil ◽  
Resonant Column ◽  
Residual Soils ◽  
Column Tests ◽  
Small Strain Stiffness ◽  
Deviator Stress ◽  
Granite Residual Soil ◽  
Stress Ratios

Most previous studies have focused on the small strain stiffness of sedimentary soil while little attention has been given to residual soils with different properties. Most studies also neglected the effects of the deviator stress, which is extensively involved in civil engineering. This note considers the effects of the deviator stress on the small-strain stiffness of natural granite residual soil (GRS) as established from resonant column tests performed under various stress ratios. Although increasing the stress ratio results in a greater maximum shear modulus for both natural and remolded residual soils, remolded soil is more sensitive to changes in the stress ratio, which highlights the effects of soil cementation. The data herein offers new insights to understand the stiffness of residual soil and other weathered geomaterials.

scholarly journals Mineralogical and Geochemical Trends in the Residual Soils above Basement Rocks in Ore Area, Southwestern Nigeria

2017 ◽  
Vol 9 (3) ◽  
pp. 42
Author(s):  
Adewole John Adeola ◽  
Emmanuel Tamunobelema Tubonemi
Keyword(s):  
Inductively Coupled Plasma ◽  
Soil Layer ◽  
Clay Mineralogy ◽  
Lateritic Soil ◽  
Residual Soils ◽  
Southwestern Nigeria ◽  
Thin Sections ◽  
Tropical Regions ◽  
Basement Rocks ◽  
Parent Rocks

Residual clays and laterite of economic values often occur within weathering profiles above basement rocks in tropical regions due to supergene enrichment and leaching of liable components. Previous studies in Ore area mainly on geochemistry of the basement rocks with scanty information on the weathered profiles. This study was carried out to determine the compositional characteristics of the basement rocks, the geochemical trends within the profiles above the parent rocks and the evaluation of their economic potentials.Petrographic study was carried out on thin sections of the rock samples. Elemental compositions of the rocks, clay, laterite, and top-soil were determined using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Clay mineralogy was determined using X-ray Diffraction (XRD) analysis. Chemical index of Alterations (CIA) was calculated from geochemical data.Weathering of granite and banded gneiss in Ore resulted in the formation of soil layer, which ranged 0-0.5m, laterite 1.2-3m and clayey zone 2.9-3.0m. Quartz, plagioclase feldspars, microcline, biotite and hornblende were the essential minerals in the parent rocks. Granite and banded gneiss is high SiO2 (>65%) but low in MgO (<2.0%) and CaO (<4.0%). Kaolinite (60-80%), goethite (3-12%) and microcline (4-10%) were the dominant minerals in the XRD of the weathering profiles. Traces of illite were present only in granite. The CIA was generally > 85 indicating advanced state of weathering producing lateritic soil. The lateritic profiles over granite and banded gneiss of Ore area varied with the composition of the parent rocks. The clay layer has economic potential for ceramics, fertilizer and structural wares.

scholarly journals Influence of the structure on the collapse potential and shear strength of a residual soil in the semiarid region of Northeast Brazil

2021 ◽  
Vol 337 ◽  
pp. 01003
Author(s):  
Valteson da Silva Santos ◽  
Allan B.Silva de Medeiros ◽  
Romário S.Amaro da Silva ◽  
Olava F. Santos ◽  
Osvaldo de Freitas Neto ◽  
...  
Keyword(s):  
Shear Strength ◽  
Expansive Soils ◽  
Friction Angle ◽  
Semiarid Region ◽  
Original Structure ◽  
Residual Soil ◽  
Residual Soils ◽  
Strength Parameters ◽  
Effective Measure ◽  
Two Samples

In the last decades, several engineering works have been developed in the Northeast of Brazil, a region marked by the occurrence of collapsible and expansive soils. This work aimed to characterize and study the behavior of two samples of residual soils collected in the municipality of Salgueiro-PE regarding their collapse potentials and shear strength parameters, in natural and disturbed conditions, evaluating the influence of the applied vertical stresses and the structural arrangement in these properties. The results obtained showed that the two samples analyzed show collapsible behavior, however, the observed potential for collapse was lower after the original structure arrangement was undone. From the direct shear strength tests, the strength parameters of the two soils were obtained, which pointed effective friction angle close to 30° and cohesive intercept close to 0 kPa. The destructuring of the samples did not cause a considerable variation in these parameters. Thus, it was possible to conclude that for these samples the microstructure has a predominant influence on the occurrence of collapsibility, but does not have the same relevance on the shear strength, such that the material’s destructuring can be considered as an effective measure to reduce the potential collapse.

Interaction of lateritic soil and steel grid reinforcement

1993 ◽  
Vol 30 (2) ◽  
pp. 376-384 ◽  
Author(s):  
D. T. Bergado ◽  
K. C. Macatol ◽  
N. U. Amin ◽  
J. C. Chai ◽  
M. C. Alfaro ◽  
...  
Keyword(s):  
Laboratory Test ◽  
Frictional Resistance ◽  
Lateritic Soil ◽  
Residual Soil ◽  
Residual Soils ◽  
Passive Resistance ◽  
Friction Resistance ◽  
Pullout Resistance ◽  
Backfill Material ◽  
Pullout Tests

Laboratory and field pullout tests were carried out to study the interaction of welded steel grid reinforcements embedded in lateritic residual soil backfill. The laboratory pullout tests were conducted on various reinforcement sizes, mesh geometries, normal pressures, and compaction conditions of the backfill material. Field pullout tests were conducted at representative overburden, field-moisture, and density conditions. From the test results, it was found that the longitudinal members yielded frictional resistance from 8 to 15% of the total grid pullout resistance. Thus, the major contribution to the pullout resistance of grid reinforcements consists of the passive resistance mobilized in front of the transverse members. The maximum pullout resistance is shown by a bilinear curve which displayed similarity with the failure envelope from direct shear tests of the backfill material. This bilinear envelope reinforced the previous observation regarding the effect of particle breakage phenomenon inherent to lateritic residual soils subjected to high normal pressures. Comparisons between laboratory and field pullout resistances and between the predicted passive resistance and the laboratory test data are also presented. Key words : reinforcement, laboratory test, earthfill, compaction, friction resistance.

Arsenic record from a 3 m snow pit at Dome Argus, Antarctica

2016 ◽  
Vol 28 (4) ◽  
pp. 305-312 ◽  
Author(s):  
Hua Rong ◽  
Hou Shugui ◽  
Li Yuansheng ◽  
Pang Hongxi ◽  
Paul Mayewski ◽  
...  
Keyword(s):  
South America ◽  
Climate Models ◽  
Source Region ◽  
Ice Core ◽  
Arsenic Concentration ◽  
Copper Smelting ◽  
Sudden Increase ◽  
Transport Pathways ◽  
Dust Transport ◽  
Arsenic Distribution

AbstractThis study presents an arsenic concentration time series from 1964–2009 at Dome Argus, Antarctica. The data show a very large increase in arsenic concentration from the mid-1980s to the late-1990s (by a factor of~22) compared with the values before the mid-1980s. This increase is likely to be related to the increased copper smelting in South America. Arsenic concentration then decreased in the late-1990s, most probably as a result of environmental regulations in South America. The sudden increase in arsenic concentration observed at Dome Argus coincides with similar increases observed at Dome Fuji and in Antarctica Ice Core-6 (IC-6) at the same time, suggesting that arsenic pollution during the period from the mid-1980s to the late-1990s was a regional phenomenon in Antarctica. Investigations of arsenic concentrations at these three Antarctic locations show that, during this time, regional arsenic distribution followed dust transport pathways associated with general climate models with South America as a major source region for the half of Antarctica facing the Atlantic and Indian oceans.

Design of bored piles in residual soils based on field-performance data

1991 ◽  
Vol 28 (2) ◽  
pp. 200-209 ◽  
Author(s):  
M. F. Chang ◽  
B. B. Broms
Keyword(s):  
Load Transfer ◽  
Large Diameter ◽  
Design Procedure ◽  
Field Performance ◽  
Residual Soil ◽  
Residual Soils ◽  
Weak Rocks ◽  
Load Tests ◽  
Bored Piles ◽  
Load Displacement

The current practice for the design of large-diameter bored piles in residual soils in Singapore is based on the calculated static capacity of the piles. Insufficient consideration of the load-transfer mechanism and overreliance on pile load tests have led to conservative designs. A better alternative is to adopt a load–displacement analysis method that provides information on the load distribution along the pile and the complete load–displacement relationship. Results of full-scale load tests on instrumented piles indicate that bored piles in residual soils in Singapore behave in the same way as in stiff clay and weak rocks elsewhere in that the load transfer at the working load is dominated by shaft friction. Simple correlations exist between the standard penetration resistance and the load-transfer parameters. An example illustrates that the proposed design procedure that uses these simple correlations and the load-transfer method is an improvement over present design methods. Key words: bored piles, cast-in-place piles, design, drilled piers, field test, load transfer, residual soil, shaft resistance.

scholarly journals Assess arsenic distribution in groundwater applying GIS in capital of Punjab, Pakistan

2015 ◽  
Vol 3 (3) ◽  
pp. 2119-2147 ◽  
Author(s):  
M. M. Akhtar ◽  
T. Zhonghua ◽  
Z. Sissou ◽  
B. Mohamadi
Keyword(s):  
Health Management ◽  
Anthropogenic Activities ◽  
Groundwater Resources ◽  
Arsenic Concentration ◽  
Arsenic Contamination ◽  
Anova Test ◽  
Arsenic Distribution ◽  
Analysis Technique ◽  
Significant Toxicity ◽  
Concentration Probability

Abstract. Arsenic contamination of groundwater resources threatens the health of millions of people worldwide, particularly in the densely populated river deltas of Southeast Asia. Arsenic causes health concerns due to its significant toxicity and worldwide presence in portable water. The major sources of arsenic pollution may be natural process such as dissolution of arsenic containing minerals and anthropogenic activities. Lahore is groundwater dependent city, arsenic contamination is a major issue of portable water and has recently been most environmental health management issue especially in the plain region, where population density is very high. GIS was used in this study for visualizing distribution of arsenic groundwater concentration through geostatistics analysis technique, and exposure risk zones for two years (2010 and 2012). Town's data was compared and concentration variation evaluated. ANOVA test was also applied to compare concentration between cities and years. Arsenic concentrations widely range 7.3–67.8 and 5.2–69.3 μg L−1 in 2010 and 2012, respectively. Over 71% area is represented arsenic concentration range from 20 to 30 μg L−1 in both analyzed years. However, in 2012 arsenic concentration over 40 μg L−1 has covered 7.6% area of Data Gunjbuksh and 8.1% of Ravi Town, while over 90% area of Allama Iqbal, Aziz Bhatti and Samanabad Town contain arsenic concentration between 20–30 μg L−1. ANOVA test depicts concentration probability less than 0.05, while differences were detected among towns. In light of current results, it needs urgent step to ensure groundwater protection and preservation for future.

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