Year: 2014
Type: report
Abstract: Regulations on construction site runoff are tightening and will likely lead to adoption of improved erosion control practices, including the application of polyacrylamide (PAM) to soil to enhance erosion and sediment control.While the benefits of PAM applications in reducing erosion have been well demonstrated for agricultural applications, it is not clear how the applied PAM differing in formations interact with soil material and how much of the applied PAM can be lost, impacting the end result for the construction site application.The project was initiated to investigate the soil-PAM interactions to obtain the maximum benefits from the PAM applied for erosion and sediment control.The project was conducted in three phases: 1) method development for quantifying dissolved PAM, 2) rainfall simulation study, and 3) laboratory column and sorption experiments.In the first phase, we developed a modified turbidimetric method using cationic surfactant (hyamine 1622) and it was proven to be a quick and reliable method for quantifying PAM in soil extracts at low carbon content.In the second phase, a rainfall simulation study was conducted to evaluate the performance of an excelsior erosion control blanket (cover) and two PAM application methods (dissolved vs granule).Runoff turbidity and total suspended solids (TSS) from PAM treatments with cover were at least 28times less than those of control (2315 nephelometric turbidity units, 2777 mg TSS L -1 ), with the cover + dissolved PAM being the most effective in delaying runoff initiation and reducing TSS.As a result of flocculation, eroded sediments collected from PAM treatments had 7-to 9-times greater median particle diameter than those from the control (12.4 µm).Loss of PAM for the granular PAM treatment was 19% of applied PAM, but was only 2% of applied PAM for the dissolved PAM treatment.While both PAM formulations applied with a temporary groundcover were effective in improving runoff water quality, applying dissolved form resulted in greater benefits with a lower PAM loss.In the third phase, we investigated dissolved PAM penetration in 2-cm thick sandy clay loam soils under saturated condition in two application modes (pulse and continuous).The pulse input of dissolved PAM applied at the typical hydroseeding rate (30 kg ha -1 in 500 mg PAM L -1 ) decreased the hydraulic conductivity (HC) by a 100-fold and allowed 14 % of the applied PAM to leached out.Continuously applied 25 mg L -1 of dissolved PAM solution decreased the HC by a 10,000-fold and leached PAM only accounted for 23 % of the total amount of applied PAM with given 130 pore volume of PAM throughput, demonstrating strong retardation of the dissolved PAM within the 2-cm soil layer.The PAM transport simulation by the CXTFIT was best described with a dual-porosity model (mobile and immobile), suggesting that the viscous PAM solution used in our study established physical nonequilibrium condition in the soil columns.Under typical conditions, it does not appear significant amounts of PAM applied for erosion control will wash away or leach very far into the soil.
Language: English
Subfield: Soil Science
Domain: Life Sciences
SDG: Life on land
Open Access status: green
OpenAlex ID: W2550808468