Acid-activated bentonites are utilized in many applications, including those that depend on their rheological properties and behavior, but little information is available regarding the rheological characteristics of this important industrial material. The purpose of this study was to investigate the effects of solids concentration, salt concentration, and pH value on the shear rate, shear stress, and other flow parameters of acid-activated bentonite suspensions. Activated Na-bentonite was prepared using sulfuric acid. Flow curves of the suspensions were modeled using the Herschel-Bulkley equation, which performed well for this system. The Herschel-Bulkley yield stress increased with the solids concentration and showed a maximum and minimum at the NaCl concentrations of 0.001 M and 0.01 M, respectively, and increased again slightly with further increases in NaCl concentration. The yield stress was at a maximum and a minimum at pH values of ≈5 and ≈7, respectively, followed by a slight increase with pH under alkaline conditions. The variations in dispersion rheological properties can be attributed to the change in the particle-association modes under different conditions.

Giant chickweed [Myosoton aquaticum (L.) Moench], a troublesome broadleaf weed species, is widespread in winter wheat (Triticum aestivum L.) fields in China. However, limited information is available on its germination and seedling emergence ecology. Thus, three M. aquaticum populations (JS, HN, and AH) from different geographic regions were studied under laboratory conditions to determine the effects of different environmental factors on germination or seedling emergence. The seeds germinated at a relatively wide constant temperature range of 5 to 25 C; however, the optimal temperature for germination varied among the populations. Compared with constant temperatures, fluctuating temperatures with the same mean significantly improved the final germination of all populations. Light was not required for germination. The seeds germinated under a wide pH range of 3 to 10, and the optimum pH was 6 to 7, with a final germination percentage of 81% to 95%. The seeds of all populations showed similar sensitivities to osmotic potential and similar high tolerances of saline conditions. The seedling emergence of all populations decreased with increasing burial depth, and no emergence was observed when the seeds were buried more than 3 cm, but the AH population showed higher sensitivity to burial depth than the others. The results generated from this study will contribute to the development of integrated M. aquaticum management strategies for winter wheat fields in China, and deep plowing and late sowing of autumn-sown wheat are suggested for managing M. aquaticum, as it showed lower germination at a low temperature and under relatively deep burial.