Monitoring the soil and sediment Mercury contamination in East Fork Poplar Creek (EFPC) Habibur Rahman Howlider*, Maruthi Sridhar Balaji Bhaskar

Department of Environmental and Interdisciplinary Science, Texas Southern University, Houston, Texas *h.howlider6094@student.tsu.edu

Introduction

●The East Fork Poplar Creek (EFPC) is contaminated historically by several heavy metals, especially mercury (Hg) and methyl mercury (MeHg), due to the presence of a Department of Energy (DOE) facility upstream of the creek.

● East Fork Poplar Creek originates from a spring beneath the Y-12 plant at the DOE Oak Ridge Reservation and flows through the residential, commercial, recreational and open-land sections of the city of Oak Ridge for 12 miles.

● In 1996 and 1997, DOE removed mercury-contaminated floodplain soils with greater than 400 ppm of mercury from two locations in the East Fork Poplar Creek floodplain.

Objectives and Goals

● To characterize the heavy metal contamination in flood plain soils and sediments of EFPC watershed and other Tennessee watersheds using spectral reflectance and remote sensing.

● To analyze and map the land cover changes by using  SPOT satellite imagery.

● To correlate the soil metal concentration to the spectral reflectance changes and identify the spectral regions sensitive to the changes in soil characteristics.

Conclusion

Geospatial image Analysis:

●To understand the land cover change in the study area, a total of 19 SPOT  imagery obtained during cloud free days over the EFPC study area were downloaded from the USGS Website.

● The SPOT imagery of Jan 9,1987; Jan 30,1987 ; Feb 25, 1987 ; Mar 2, 1987 ; Jan 26, 1990 ; Sep 9, 1998 and Sep 25, 1998 were selected for analyzing the land cover changes.

● All the SPOT satellite data was processed and visually analyzed by making the color composite imagery and spectral ratio images by using the ER MAPPER image processing software.

Materials and Methods

Jan 9 1987 Jan 30 1987 Feb 25,1987 March 2,1987 Jan 26 1990 Jan 26 1990 another Sep 09 1998 Sep 25 19980

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Seasonal Vegetation changes from 1987-1998

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Fig 1: Hand held portable spectrometer setup for obtaining the spectra of the soil samples using ASD spectrometer (with 350-1050 nm spectral range) and spectral evolution spectrometer (with 350-2500 nm spectral range)

Fig 3 : The satellite imagery of the study area showing the vegetation and impervious surface areas.

Fig 5: Seasonal vegetation surface area changes between 1987-1998 derived from the SPOT imagery.

Spectral Analysis:● Spectral reflectance is a non-destructive, cost-effective, environmental friendly approach to monitor the soil and sediment contamination.

● The spectral reflectance was obtained inside the laboratory with a 100W Quartz Tungsten Halogen (QTH) lamp as a source of illumination.

Chemical Analysis :● Selected soil samples were analyzed for Hg concentrations using the AMA 254 Mercury analyzer (LECO corporation, St. Joseph, MI).

Soil sampling and Analysis:

● A total of 74 soil and sediment samples were collected from EFPC during the summer of 2015.

● The soil samples were air dried, grinded and sieved through a 2mm sieve and then prepared for spectral analysis using an Analytical Spectral Devices (ASD) Spectrometer (350-1050 nm) and Spectral Evaluation Spectrometer (350-2500 nm).

Analytical Spectral Devices (ASD) Experimental Setup

Spectral Evolution Spectrometer Experimental Setup

Fig 2. Soil and sediment sampling locations along the East Fork Poplar Creek (EFPC)

Results and Discussion

Spectral reflectance of soil in 350-2500 nmSpectral range.

Spectral reflectance of soil in 350-1050 nmSpectral range)

Fig 6: Changes in the soil spectral reflectance in response to changes in soil Hg concentration.

Our soil spectral reflectance analysis showed that the soils with higher Hg concentration showed lower reflectance compared to the soils with lower Hg concentration.

NDVI SPOT pseudo color image, (Sep 05,1998)

The masked NDVI image of the study area showing the robust vegetation (Sep 05,1998)

The masked NDVI image of the study area showing the impervious surface (Sep 05,1998)

Fig 4: Spectral reflectance of soil covering the visible (400-700 nm) and Near Infrared (NIR) wavelengths (700-2500 nm) obtained by using ASD and spectral evolution spectrometers

• Soil with higher Hg concentrations showed lower reflectance in the 350 to 2500 nm spectral range compared to the soils with lower Hg concentration.

• In the visible region of the spectrum, the spectral reflectance of the Hg contaminated and control soils shows less difference in the 400-700 nm wavelengths. The spectral difference between the Hg contaminated and control soils are significantly higher in the NIR region (700 – 2500 nm).

• Soil heavy metal contamination can be mapped using the spectral reflectance of the soils in the visible and near infra red region of the spectrum.

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• Our spectral analysis showed that the soils collected from areas with higher Hg concentrations of 31.78 ppm showed lower reflectance compared to the areas with lower Hg concentrations of 2.99 ppm for both of Analytical Spectral Devices (ASD) Spectrometer and Spectral Evolution Spectrometer.