Wind tunnel experiment on polypeptide derivatives in controlling wind erosion

Abstract: The utilization of macromolecular polymers that can improve soil structure to fix sand is one of important measures for controlling soil wind erosion. Indoor wind tunnel experiments were conducted to study the effect of macromolecular polymers and polypeptide derivatives on wind erosion control in drift-sand and sandy loess. The soils used in this study were collected from the wind-water erosion crisscross region on the Loess Plateau. Four macromolecular polymers or polypeptide derivatives were used and they were polyacrylamide (PAM), cationic hydroxypropyl quito sugar (Jag C162), carboxymethyl cellulose (CMC) and hydroxypropyl polysaccharide (HP-120). The application doses of the polymers were 0 (CK), 0.4, 0.6 and 1.2 g/m2. All the tests were repeated for 3 times. The wind tunnel had a length in 24 m. The wind speed could be adjusted in a range of 0-16 m/s. The wind speed was measured by using an AZ-8902 Anemobiagraph with a range of 0.6-35 m/s. The soil tank had the width of 98 cm, the length of 126 cm and the depth of 5 cm. The soil density of the drift-sand and sandy loess was 1.36 and 1.29 g/cm3, respectively. The water content of air-dried sandy loess and drift-sand was 0.25% and 0.21%, respectively. During the experiment, the wind speed was adjusted to 14 m/s for 20 min. The wind erosion rate was calculated and the consolidation layer hardness was determined. The results showed that all the materials with different doses could significantly reduce wind erosion rate (P<0.05) on the disturbed drift-sand and sandy loess surface. Compared with the others, PAM was the best in decreasing wind erosion rate on the surface of sandy loess. Averagely, PAM, Jag C162, CMC and HP-120 on the surface of sandy loess could decrease the wind erosion rate by 65.47%, 51.78%, 62.34% and 50.29% (P<0.05), respectively; On the surface of drift-sand, PAM, Jag C162, CMC and HP-120 could decrease the wind erosion rate by 62.56%, 92.58%, 98.45% and 92.88% (P<0.05), respectively. The CMC had the best effect in reducing wind erosion rate on the surface of drift-sand among the polymers. Compared with the CK, the polymers could increase the consolidation layer hardness of the sandy loess significantly except for the 0.4 g/m2 Jag C162 treatment. For the most treatments, the hardness increased with application doses. At the application dose of 1.2 g/m2, the hardness was the highest after spraying PAM and the least after spraying HP-120 on the surface of sandy loess. Compared with the CK, the hardness could be increased by 356% using the PAM. On the drift-sand, the CMC had the best effect in increasing consolidation layer hardness and the hardness could be increased by 746.15% using the CMC. Overall, the PAM had the best effect in decreasing wind erosion rate and increasing hardness on the surface of sandy loess while the CMC was the best for the drift-sand. At the application dose of 1.2 g/m2, all the polymers showed good wind erosion control capacity to resist against 14 m/s wind for 20 min with little wind erosion.