USGS Iowa Water Science Center

Phosphorus in Kent Park Lake - Methods

Sample collection

A hand core sampler was used to collect bottom material samples from nine lake bed, two dredge spoil ponds, and two sedimentation ponds (table 1). A soil sample was collected at a site in a gulley that was actively eroding.  Lake bed samples were collected from seven sites in the inlet bays and from two deep water site using techniques described by Radtke (2005).  The core sampler was 5.0 cm (2 inches) diameter and 51 cm (20 inches) long. The core sampler generally was pushed the full length of the corer into the bottom material. Material in the sampler was extracted into a glass bowl and was composited with a Teflon spatula. The composited material was subset into two samples; one was put into a 120 ml (4 ounce) glass container and then chilled for shipment to the laboratory and the second was put into a plastic bag for sediment size analysis.

Sample processing

Sediment samples were analyzed by the U.S. Geological Survey contract laboratory using EPA approved methods. Total phosphorus was analyzed using the automated ascorbic acid reduction method 4500-P F (Standard methods, 2011). Moisture content of the sample was determined using the American Society for Testing and Materials (ASTM, 2010) method D2216.

Samples were analyzed for the clay sized (0.002mm and 0.004mm), silt sized (0.008mm, 0.016mm, 0.031mm, and 0.062mm) and sand sized (0.25mm, 0.5mm,and 1mm) particles by methods described by Guy (1969). The sediment samples were placed in an oven set at 103 degrees Celsius for several days until dry and then dry sieved to determine the sand fractions. Material passing through the 0.062mm sieve was used with the visual accumulation (VA) tube-pipet method to determine the silt and clay fractions (Guy, 1969).

Method References

ASTM, 2010, Standard test methods for laboratory determination of water (moisture) content of soil and rock by mass, American Society for Testing and Materials

Guy, H.P., 1969, Laboratory theory and methods for sediment analysis: U.S. Geological Survey Techniques of Water-Resources Investigations, Book 5, Chapter C1,58 p.

Radtke, D.B., 2005, Bottom-material samples (ver. 1.1): U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A8, June 2005, 

Standard methods, 2011, 4500-P Phosphorus: Standard Methods for the Examination of Water and Wastewater