Quantitative Fractal Evaluation of Herbicide Effects on the Water‐Absorbing Capacity of Superabsorbent Polymers

Abstract

The water absorption capacity of superabsorbent polymers (SAPs) is important for agricultural drought resistance. However, herbicides may leach into the soil and affect water absorption by damaging the SAP three‐dimensional membrane structures. We used 100‐mesh sieves, electron microscopy, and fractal theory to study swelling and water absorption in SAPs in the presence of three common herbicides (atrazine, alachlor, and tribenuron‐methyl) at concentrations of 0.5, 1.0, and 2.0 mg/L. In the sieve experiments it was found that 2.0 mg/L atrazine reduces the capacity by 9.64–23.3% at different swelling points; no significant diminution was observed for the other herbicides or for lower atrazine concentrations. We found that the hydrogel membrane pore distributions have fractal characteristics in both deionized water and atrazine solution. The 2.0 mg/L atrazine destroyed the water‐retaining polymer membrane pores and reduced the water‐absorbing mass by modifying its three‐dimensional membrane structure. A linear correlation was observed between the fractal analysis and the water‐absorbing mass. Multifractal analysis characterized the membrane pore distribution by using the range of singularity indexes Δα (relative distinguishing range of 16.54–23.44%), which is superior to single‐fractal analysis that uses the fractal dimension D (relative distinguishing range of 2.5–4.0%).