Laboratory Methods and Analysis

Data Series 1059

A Seasonal and Spatial Comparison of Metals, and Stable Carbon and Nitrogen Isotopes, in Chincoteague Bay and the Marsh Deposits of Assateague Island and the Adjacent Vicinity, Maryland and Virginia

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Abstract

Introduction

Field Data Collection

Laboratory Methods and Analysis

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Abbreviations

References

Lab methods for grain-size analyses, bulk density, water content, and LOI can be found in separate publications (Ellis and others, 2015; Smith and others, 2015). The sediment processed for metals and stable isotopes was subsampled from the sediment parameters split. If the sediment parameters split was depleted or lacking in material for the metals and stable isotope analyses, addition material was taken from the frozen, archived sediment split for that sample.

Metals

Metals concentrations were acquired by submitting between 0.9592 and 1.3259 grams (g) of dried and homogenized sediment to the USGS Central Mineral and Environmental Resources Science Center (CMERSC) in 25 mL glass scintillation vials for a 42-element analysis of concentrations (Taggart, 2002). At CMERSC, samples were digested using hydrochloric, nitric, perchloric, and hydrofluoric acids and then aspirated into the inductively coupled plasma-atomic emission spectrometer (ICP-AES) and inductively coupled plasma-mass spectrometer (ICP-MS). The ICP-AES was calibrated using digested rock reference materials as well as a series of multi-element solution standards. The ICP-MS was calibrated with aqueous standards. To account for internal drifts and matrix effects, internal standards were used.

Stable Isotopes

Sediment samples were submitted to the Yale Analytical and Stable Isotope Center (YASIC), a Yale Institute for Biospheric Studies (YIBS) research center, for percent organic carbon, percent nitrogen, carbon-nitrogen ratio, δ¹³C, and δ¹⁵N. Dried and homogenized sediment was placed in 8 x 5 millimeter (mm) silver capsules, wet with 50 microliters (µL) of deionized water, and fumigated in a desiccator with 100 mL of concentrated hydrochloric acid for 6 hours to remove inorganic carbon (Harris and others, 2001). Samples were then dried at 60 °C overnight, and double encapsulated in tin for combustion purposes. Unfumigated sediment samples were also submitted for percent carbon, percent nitrogen, carbon-nitrogen ratio, δ¹³C, and δ¹⁵N by way of dried and homogenized sediments submitted in tin capsules. All samples were analyzed using a Costech ESC 4010 Elemental Combustion System interfaced with a Thermo Finnigan DELTAplus Advantage isotope ratio mass spectrometer. Values are relative to international standards: the VPDB (Vienna Pee Dee Belemnite) for carbon and air for nitrogen. The standard deviation of the provided values is estimated at ±0.4 per mille.