Continuous-flow centrifugation to collect suspended sediment for chemical analysis
Recent advances in suspended-sediment monitoring tools and surrogate technologies have greatly improved the ability to quantify suspended-sediment concentrations and to estimate daily, seasonal, and annual suspended-sediment fluxes from rivers to coastal waters. However, little is known about the chemical composition of suspended sediment, and how it may vary spatially between water bodies and temporally within a single system owing to climate, seasonality, land use, and other natural and anthropogenic drivers. Many water-quality contaminants, such as organic and inorganic chemicals, nutrients, and pathogens, preferentially partition in sediment rather than water. Suspended sediment-bound chemical concentrations may be undetected during analysis of unfiltered water samples, owing to small water sample volumes and analytical limitations. Quantification of suspended sediment‑bound chemical concentrations is needed to improve estimates of total chemical concentrations, chemical fluxes, and exposure levels of aquatic organisms and humans in receiving environments. Despite these needs, few studies or monitoring programs measure the chemical composition of suspended sediment, largely owing to the difficulty in consistently obtaining samples of sufficient quality and quantity for laboratory analysis.
A field protocol is described here utilizing continuous‑flow centrifugation for the collection of suspended sediment for chemical analysis. The centrifuge used for development of this method is small, lightweight, and portable for the field applications described in this protocol. Project scoping considerations, deployment of equipment and system layout options, and results from various field and laboratory quality control experiments are described. The testing confirmed the applicability of the protocol for the determination of many inorganic and organic chemicals sorbed on suspended sediment, including metals, pesticides, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls. The particle-size distribution of the captured sediment changes to a more fine-grained sample during centrifugation, and the necessity to account for this change when extrapolating chemical concentrations on the centrifuged sediment sample to the environmental water system is discussed.
The data produced using this method will help eliminate a data gap of suspended sediment-bound chemical concentrations, and will support management decisions, such as chemical source-control efforts or in-stream restoration activities. When coupled with streamflow and sediment flux data, it will improve estimates of riverine chemical fluxes, and will aid in assessing the importance and impacts of suspended sediment-bound chemicals to downstream freshwater and coastal marine ecosystems.
Conn, K.E., Dinicola, R.S., Black, R.W., Cox, S.E., Sheibley, R.W., Foreman, J.R., Senter, C.A., and Peterson, N.T., 2016, Continuous-flow centrifugation to collect suspended sediment for chemical analysis: U.S. Geological Survey Techniques and Methods, book 1, chap. D6, 31 p., plus appendixes, https://doi.org/10.3133/tm1D6.
ISSN: 2328-7055 (online)
Table of Contents
- Description of Continuous-Flow Centrifugation Method
- Quality Control Testing of Continuous-Flow Centrifugation Methods
- Results from Field Testing the Continuous-Flow Centrifugation Methods
- References Cited
|Publication Subtype||USGS Numbered Series|
|Title||Continuous-flow centrifugation to collect suspended sediment for chemical analysis|
|Series title||Techniques and Methods|
|Publisher||U.S. Geological Survey|
|Publisher location||Reston, VA|
|Contributing office(s)||Washington Water Science Center|
|Description||Report: viii, 31 p.; Appendixes: A-E|
|Larger Work Type||Report|
|Larger Work Subtype||USGS Numbered Series|
|Larger Work Title||Section D: Water quality in Book 1: Collection of water data by direct measurement|
|Public Comments||This report is Chapter 6 of Section D: Water quality in Book 1: Collection of water data by direct measurement.|
|Online Only (Y/N)||Y|
|Additional Online Files (Y/N)||Y|
|Google Analytic Metrics||Metrics page|