Delta-X: Sediment Core Grain Size Distribution, Wax Lake Delta, MRD, LA

This dataset provides grain size distribution measurements collected from sediment core samples on Mike Island in the Wax Lake Delta, Louisiana, as part of the Delta-X Spring campaign in March, 2021,and the Fall campaign during August, 2021. The data are for March 26 and 29, and August 18 and 24. Sediment cores were collected using a piston core, then volume-based grain size distribution for each sample was measured using a laser diffraction particle size analyzer. The data are provided in comma separated values (CSV) format.

There is one data file in comma separated values format (.csv) with this dataset.

This dataset provides grain size distribution measurements collected from sediment core samples on Mike Island in the Wax Lake Delta, Louisiana, as part of the Delta-X Spring campaign in March, 2021,and the Fall campaign during August, 2021. The data are for March 26 and 29, and August 18 and 24. Sediment cores were collected using a piston core, then volume-based grain size distribution for each sample was measured using a laser diffraction particle size analyzer. Some sediment cores were sampled in association with a sediment concentration-depth profile (Nghiem et al., 2024).

Project: Delta-X

The Delta-X mission is a 5-year NASA Earth Venture Suborbital-3 mission to study the Mississippi River Delta in the United States, which is growing and sinking in different areas. River deltas and their wetlands are drowning as a result of sea level rise and reduced sediment inputs. The Delta-X mission will determine which parts will survive and continue to grow, and which parts will be lost. Delta-X begins with airborne and in-situ data acquisition and carries through data analysis, model integration, and validation to predict the extent and spatial patterns of future deltaic land loss or gain.

Acknowledgement

This work was supported by NASA Earth Venture Suborbital-3 Program (grant NNH17ZDA001N-EVS3: Delta-X) and Research and Technology Development at NASA's Jet Propulsion Laboratory (Strategic R&TD FY17–19).

Spatial Coverage:  Mike Island, Wax Lake Delta (WLD), Louisiana

 Spatial Resolution: Point

Temporal Coverage: 2021-03-26, 2021-03-29 (Spring) and 2021-08-18, 2021-08-24 (Fall)

Temporal Resolution: One-time measurements

Site Boundaries: Latitude and longitude are given in decimal degrees.

Site	Westernmost Longitude	Easternmost Longitude	Northernmost Latitude	Southernmost Latitude
Louisiana's CRMS sites and on Mike Island in WLD, southern coast of Louisiana	-91.44623	-91.44041	29.5092	29.4822

Data File Information

There is one data file in comma-separated values (.csv) format with this dataset: DeltaX_CoreGrainSizeDistribution_Spring_Fall.csv

Table 1. Variables in the data file.

Parameter	Units	Description
basin	-	“Atchafalaya”
site_id	-	Location within the basin, “Wax Lake Delta”
campaign	-	“Spring_2021” or “Fall_2021”
core	-	Name of the sediment core
sample	-	Name of the sample
upper_depth	cm	Depth from the top of the extruded core to the top of the sample interval
lower_depth	cm	Depth from the top of the extruded core to the bottom of the sample interval
DP	-	Name of the sediment concentration-depth profile associated with the sediment core. If missing, then sample was not collected as part of a concentration-depth profile.
latitude	degrees north	Latitude of sediment core sample site in decimal degrees
longitude	degrees east	Longitude of sediment core sample site in decimal degrees
date_time	YYYY-MM-DD HH:MM:SS	Date and time of sampling in UTC
pipe_sink	cm	Length of pipe pushed into the bed
extruded_length	cm	Length of extruded core
optimized_refractive_index	1	Optimized refractive index (RI)
optimized_absorption_index	1	Optimized absorption index (AI)
fraction_by_grain_size_[lower grain size]_[upper grain size]	1	Volume fraction of sediment by range of grain sizes. There are 100 columns with size range, lower grain size to the upper grain size, listed in field name. Grain size units are in microns.

These detailed field data are required to successfully characterize and model sediment fluxes because settling and accretion of mineral sediment are highly dependent on the sediment grain size. The measurements are compared to numerical models to calibrate and validate its parameters. The hydrology models quantify the mesoscale (i.e., on the order of 1 ha) patterns of soil accretion that control land loss and gain and predict the resilience of deltaic floodplains under projected relative sea-level rise. Understanding and mitigating the impact of the relative sea-level rise on coastal deltas is urgent. If ignored, relative sea-level rise will very soon have devastating consequences on the livelihood of the half-billion people that live in these low-lying coastal regions.

Repeated grain size distribution measurements of samples were run on the laser diffraction particle size analyzer at least five times to characterize the uncertainty of grain size distribution measurements. Relative standard deviations of the D₁₀, D₅₀, and D₉₀ grain sizes across replicates were all below 2.5% for all samples as recommended by Malvern.

Sediment cores were collected in Mike Island, Wax Lake Delta (Fig. 1). Sediment cores were collected using a piston core either 5.08 cm or 6.35 cm (2 or 2.5 inches) in diameter (Fig. 2). Some sediment cores were sampled in association with a sediment concentration-depth profile (Nghiem et al., 2024). For each sediment core, the piston core was pushed by hand into the ground. The piston was held in place at the bed surface while the outer pipe was pushed into the subsurface. The length to which the core was pushed in the bed was measured to represent the in situ length of the sediment core before it was extracted. The pipe and piston were pulled from the ground together to extract the sediment core from the bed. The length of the sediment core after being extruded from the piston core was measured to represent the actual sampled length. The sediment core was sectioned by length intervals using a knife, which was washed in river water between each slice. Not all intervals were sampled or measured. Those handling samples wore nitrile gloves to avoid sample contamination. Each sediment core section was transferred to a labeled plastic sample bag. Samples were frozen until ready for laboratory analysis.

Figure 2: Example of piston core used to sample sediment core.

In the laboratory, the samples were prepared and analyzed for grain size distribution. First, samples were transferred into glass beakers and dried under low heat (50-70°C). The samples were then split for different analyses using the quarter-cone method. The sample splits were decarbonated using 1 M HCl for grain size analysis to remove inorganic carbon. Then, organic matter was removed by oxidation with 30% hydrogen peroxide solution and heat (~80°C). Finally, the samples were treated with sodium hexametaphosphate solution and sonicated to prevent flocculation.

The volume-based grain size distribution for each sample was measured using a Malvern Mastersizer 3000E laser diffraction particle size analyzer. Output grain size distributions were reported from 0.2 to 2100 μm in 100 logarithmically spaced bins. Angular light scattering intensities were inverted using Mie theory in the Mastersizer software to calculate grain size distributions. This inversion is sensitive to the refractive index (RI) and absorption index (AI) of the particles. RI and AI were optimized for each sample by finding the values that minimize the difference between measured and modeled light scattering intensity in the Mastersizer’s optical property optimizer feature (Rawle, 2015; Malvern Panalytical, 2024). In the optimization, RI was limited between 1.5 and 1.7, which covers the range of common sedimentary minerals (Özer et al., 2010), and AI between 0.001 and 0.01, which empirically best suited the samples.

Malvern Panalytical. 2024. Mastersizer User Guide. https://www.malvernpanalytical.com

Özer, M., M. Orhan, and N.S. Isik. 2010. Effect of particle optical properties on size distribution of soils obtained by laser diffraction. Environmental & Engineering Geoscience 16:163-173. https://doi.org/10.2113/gseegeosci.16.2.163.

Rawle, A.F. 2015. Best practice in laser diffraction–a robustness study of the optical properties of silica. Procedia engineering 102:182–189, https://doi.org/10.1016/j.proeng.2015.01.124