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Geochemical Analysis of Fe Enriched Soil of Meherrin, Virginia

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Meherrin is located in the Piedmont region of Virginia. The Piedmont region is at the foot of the Blue Ridge Mountain range, which is part of the Appalachian Mountain system. The Piedmont features rolling hills and deeply weathered bedrock.

Geology of the Piedmont Region
• Most of the igneous and metamorphic rocks in the province range in age from Proterozoic to Paleozoic. They form the internal core of the Appalachian Mountain belt.
• Triassic sedimentary rocks, diabase dikes, and basalt flows are present in several grabens and half-grabens that formed during rifting associated with the opening of the Atlantic Ocean.
• Rivers and streams carrying sand, silt, and mud flowed into these lowland rift basins, burying swamps and marshes and later producing small coal measures.

Sampling Locations
• Site “MA” consists of Lloyd Clay Loam and not prime farmland.
• Site “MB” consists of Iredell Loam and farmland of state-wide importance.
• Site “MC” is a bit southwest of our site in Keysville, VA. It is much like site “MA.”

Area Soil Description
• Northeast of Meherrin, the soil consists of a yellow to brown decomposed granite with streaks and patches of red.
• The soil in the county is generally fertile, but the ridges are thin and poor. The lower eastern part of the county is a light gray or sandy soil.
• There is a strip of land, running almost through the center of the county, that is about 10 miles wide and has stiff red soil.
• Stream clay is known to occur one mile southwest of Meherrin. Between Meherrin and Keysville (also Southwest), the town of Simplicity has pre-Cambrian volcanics that yield a residual clay 3 to 4 feet in depth.

Aim and Objective
• Consisting of Ultisols of the Georgeville series, Meherrin’s soil has a high amount of clay (27%) in comparison with the rest of the Georgeville series.
• A geochemical analysis was conducted to understand the differences of the soil characteristics in Meherrin, with respect to the nearby soils of the Piedmont region.
• Several nearby sites have been assessed for comparison.

Analytical Approach
• Samples were size partitioned by wet sieving.
• The sample fractions, less than 63 microns and greater than 63 microns, were analyzed by an X-ray fluorescence (XRF) spectrophotometer to understand elemental composition, soil color, and properties.
• After thoroughly washing and drying the greater than 63-micron fractions, magnetic particles were manually separated using a strong hand magnet, and the composition was studied using XRF.
• Separated magnetic particles were analyzed with an Olympus® TERRA® X-ray diffraction (XRD) analyzer.
• A scanning electron microscope (SEM) was used for micromorphological and elemental analysis.

For more information, visit: https://www.olympus-ims.com/en/innovx-xrf-xrd/

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Geochemical Analysis of Fe Enriched Soil of Meherrin, Virginia

  1. 1. GEOCHEMICAL ANALYSIS OF THE IRON- ENRICHED SOIL OF MEHERRIN, VIRGINIA Sara Irena Chojna1, Arif M. Sikder1, Jose Brum2, Xin-Chen Liu1, Elizabeth Keily1, Dustin M. Clifford3,Carlos E. Castano Londono3 1. Center for Environmental Studies (CES); Virginia Commonwealth University (VCU), 1000 West Cary Street, Richmond, VA 23284 2. Olympus Scientific Solutions Americas, 48 Woerd Ave, Suite 105, Waltham, MA 02452 3. Nanomaterial Characterization Center (NCC),Virginia Commonwealth University (VCU) 620 West Cary Street,Richmond, VA 23284
  2. 2. Meherrin is located in the Piedmont region of Virginia. The Piedmont region is at the foot of the Blue Ridge Mountain range, which is part of the Appalachian Mountain system. The Piedmont features rolling hills and deeply weathered bedrock.
  3. 3. • Most of the igneous and metamorphic rocks in the province range in age from Proterozoic to Paleozoic. They form the internal core of the Appalachian Mountain belt. • Triassic sedimentary rocks, diabase dikes, and basalt flows are present in several grabens and half-grabens that formed during rifting associated with the opening of the Atlantic Ocean. • Rivers and streams carrying sand, silt, and mud flowed into these lowland rift basins, burying swamps and marshes and later producing small coal measures. Geology of the Piedmont Region
  4. 4. Sampling Locations • Site “MA” consists of Lloyd Clay Loam and not prime farmland. • Site “MB” consists of Iredell Loam and farmland of state-wide importance. • Site “MC” is a bit southwest of our site in Keysville, VA. It is much like site “MA.”
  5. 5. Area Soil Description There is a strip of land, running almost in the center of the county about 10 miles in width that has stiff red soil. Stream clay is known to occur one mile southwest of Meherrin. Between Meherrin and Keysville (also Southwest), the town of Simplicity has pre-Cambrian volcanics that yield a residual clay 3 to 4 feet in depth. • Northeast of Meherrin, the soil consists of a yellow to brown decomposed granite with streaks and patches of red. • The soil in the county is generally fertile, but the ridges are thin and poor. The lower eastern part of the county is a light gray or sandy soil.
  6. 6. Area Soil Description • There is a strip of land, running almost through the center of the county, that is about 10 miles wide and has stiff red soil. • Stream clay is known to occur one mile southwest of Meherrin. Between Meherrin and Keysville (also Southwest), the town of Simplicity has pre-Cambrian volcanics that yield a residual clay 3 to 4 feet in depth.
  7. 7. Meherrin Soil • Meherrin consists of fine cut residual clay that is 18-feet deep. It is red and fairly sticky. The soil in this image (left) is from site “MA.”
  8. 8. MA: color red (10R 4/8) MB: color green (10Y 5/2) The samples from each site were collected by core sampling at 6-inch intervals. For this study, sites were coded as MA, MB, and MC and located within 3 miles of each other. MA and MB differ considerably in their color.
  9. 9. Aim and Objective • Consisting of Ultisols of the Georgeville series, Meherrin’s soil has a high amount of clay (27%) in comparison with the rest of the Georgeville series. • A geochemical analysis was conducted to understand the differencesof the soil characteristics in Meherrin, with respect to the nearby soils of the Piedmont region. • Several nearby sites have been assessed for comparison.
  10. 10. Analytical Approach • Samples were size partitioned by wet sieving. • The sample fractions, less than 63 microns and greater than 63 microns, were analyzed by an X-ray fluorescence (XRF) spectrophotometer to understand elemental composition, soil color, and properties. • After thoroughly washing and drying the greater than 63-micron fractions, magnetic particles were manually separated using a strong hand magnet, and the composition was studied using XRF. • Separated magnetic particles were analyzed with an Olympus® TERRA® X-ray diffraction (XRD) analyzer. • A scanning electron microscope (SEM) was used for micromorphological and elemental analysis.
  11. 11. Result of Elemental Analysis by XRF • The Fe₂O₃ content in bulk samples is relatively high, varying between 10% and 30%. • The concentration of Fe₂O₃ increases with depth in samples for location MA, yet the highest concentration is observed in the most shallow samples. • In all locations, the distribution of alkali metals does not show a trend. • Chemical index of alteration (CIA): 100–80 is highly weathered; 60–80 is glacial to moderate; below 60 is a cold glacial environment. • CIA values between 50 and 60 indicate incipient weathering, between 60 and 80 indicate intense weathering, and more than 80 for extreme weathering.
  12. 12. Result of Elemental Analysis by XRF CIA=(Al2O3/Al2O3+CaO*+Na2O+K2O) × 100
  13. 13. Distribution of Magnetic Particles
  14. 14. Distribution of Magnetic Particles Sample ID Bulk Dry Weight (gm) Fractions > 63 um (gm) Fractions > 63 um (wt%) Magnetics > 63 um (gm) Magnetics > 63 um (gm) 200a 21.51 8.86 41.19014412 0.12 1.35440181 200b 8.75 5.73 65.48571429 0.09 1.57068063 200c 160.12 35.67 22.27704222 0.44 1.23352958 400a 21.61 13.64 63.11892642 0.22 1.61290323 400b 37.73 17.3 45.85210708 0.21 1.21387283 400c 90.81 15.39 16.94747275 0.23 1.49447693 800a 89.24 23.85 26.72568355 0.32 1.34171908 800b 46.47 23.66 50.91456854 0.66 2.78951817 800c 40.68 23.5 57.76794494 0 0 1600a 35.83 17.97 50.15350265 0.89 4.95269894 1600c 47.44 12.82 27.02360877 0 0
  15. 15. More Results of Elemental Analysis
  16. 16. Mineralogical Analysis by XRD MA7: Kaolinitic MB5: Much less clay mineral
  17. 17. XRD Analysis of the Magnetic Particles: Cobalt Target
  18. 18. XRD Analysis of the Magnetic Particles: Cobalt Target • 11% akaganeite: akaganeite is formed by the weathering of pyrrhotite. The occurrences in meteorites and lunar samples are thought to have been produced by interaction with Earth's atmosphere. • 51% magnetite and 29% hematite: the mineral form of ferric oxide iron(III) oxide (Fe2O3) is one of several iron oxides. Only 1% goethite is an iron oxyhydroxide containing ferric iron. It is the main component of rust and bog iron ore.
  19. 19. SEM Analysis of Magnetic Particles
  20. 20. SEM Analysis for Magnetic Particles
  21. 21. Widmanstӓtten Pattern
  22. 22. SEM EDS Analysis
  23. 23. Observations Microscopic analysis of separated magnetic particles reveals the presence of well preserved euhedral crystals of magnetite, hematite, and potentially wustite (cubic FeO). Furthermore, the SEM analysis revealed magnetic spherules and relic grains with apparent Widmanstӓtten patterns. Such patterns may indicate an extra-terrestrial or volcanic source of iron-enriched mineral phases, accountable for the special characteristics of Meherrin soil.
  24. 24. Acknowledgements VCU Center for Environmental Studies Dr. Rodney Dyer Dr. Leigh McCallister Jen Ciminelli Mack Barnes

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