Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D3977-97 – Standard Test Method Technical Guide
📖 Scope and Overview of ASTM D3977‑97
ASTM D3977‑97 (Reapproved 2019) defines standardized laboratory procedures for determining sediment concentrations in water and wastewater samples from lakes, reservoirs, and flowing streams. In quiescent waters, the measured concentration closely matches the in‑situ condition. For rivers, isokinetic collection is essential; the resulting concentration can be multiplied by the water discharge to calculate sediment discharge. The standard explicitly distinguishes three test methods—Evaporation, Filtration, and Wet‑Sieving‑Filtration—and warns that these mass‑based methods must not be confused with optical turbidity measurements (Test Method D1889).
⚠️ Critical Distinction: D3977‑97 methods quantify sediment mass and are not interchangeable with turbidity measurements. Test Method C specifically provides separate concentration values for sand‑size particles versus the combined silt and clay‑size fractions.
⚙️ Detailed Breakdown of Test Methods A, B, and C
Each method has specific applicability criteria. Test Method A relies on natural settleability, while Methods B and C utilize filtration. The Wet‑Sieving‑Filtration procedure is unique in delivering two discrete concentration values for particle size fractions.
| 🟦 Method | 📏 Principle | 📐 Key Constraints | 🎯 Applicability |
|---|---|---|---|
| A – Evaporation (Sections 8‑13) | Sediment settles naturally; water is evaporated. | Sediment must be settleable. Dissolved‑solids correction required if solids exceed 10 % of sediment concentration. | Samples where solids settle within storage time (days to weeks). |
| B – Filtration (Sections 14‑19) | Filters directly separate water from sediment. | Sand concentration < 10 000 ppm. Clay concentration < 200 ppm. No dissolved‑solids correction required. | Samples with non‑settleable fines and relatively low suspended loads. |
| C – Wet‑Sieving‑Filtration (Sections 20‑25) | Sieving separates sand; filtration captures silt/clay. | Silt‑clay fraction need not be settleable. Yields two separate concentration results. | When both sand‑size and combined silt‑clay concentrations are needed. |
📊 Key Measured Properties and Analytical Limits
Method selection depends on strict adherence to the compositional limits defined in the standard’s scope. The following thresholds guide the technician toward the appropriate laboratory procedure.
| ⚡ Parameter | Method A | Method B | Method C |
|---|---|---|---|
| Max Sand Concentration | Settling dependent | < 10 000 ppm | No upper limit (sieved) |
| Max Clay Concentration | Settling dependent | < 200 ppm | Not limited (filtered after sieving) |
| Dissolved‑Solids Correction | Required if >10 % of sediment conc. | Not required | Not required |
| Settleability Required | Yes | No | No (for silt/clay fraction) |
✅ Technical Note: All values in ASTM D3977‑97 are stated in SI units. The standard is utilized by major federal agencies, including the U.S. Geological Survey, the Natural Resources Conservation Service, the Bureau of Reclamation, and the Agricultural Research Service.
❓ Frequently Asked Questions
🔍 When should Test Method A (Evaporation) be used over Test Method B (Filtration)?
Method A is appropriate when the sediment is entirely settleable within the sample storage time. Method B must be used if the sample contains non‑settleable fines, provided sand is below 10 000 ppm and clay is below 200 ppm.
💡 What is the dissolved‑solids correction factor in Method A?
A correction must be applied to the sediment concentration if the dissolved‑solids concentration exceeds approximately 10 % of the sediment concentration. No such correction is needed for Methods B or C.
⚡ Can the Wet‑Sieving‑Filtration method handle high sand loads?
Yes. Method C uses a sieve to separate sand before filtration, imposing no upper sand concentration limit. It yields distinct values for the sand‑size fraction and the silt‑clay fraction.
📌 Is ASTM D3977 suitable for measuring turbidity?
No. The standard’s scope explicitly warns that these test methods must not be confused with turbidity measurements. Turbidity (Test Method D1889) is an optical measurement of light scattering and does not provide an accurate measure of sediment mass or concentration.