气源及活性剂对曝气滴灌带水气单双向传输均匀性的影响

曝气滴灌过程中水、氧、气传输均匀性是评价曝气灌溉质量的重要指标。活性剂的添加和传输方式的优选对曝气滴灌传输过程中微气泡的存在和溶解氧的保持有重要意义。为提高水气耦合物在滴灌过程中传输的距离和均匀性,该文采用Mazzei 1078文丘里空气射流器进行曝气增氧,以空气和氧气为供试气源,研究活性剂BS1000浓度(0、1、2和4 mg/L)和传输方式(单向和双向)对曝气滴灌下水、氧、气传输特性的影响。结果表明:曝气导致单向传输下流量均匀性略有下降,但可显著提高灌溉水中溶解氧和掺气比例;随着活性剂浓度的增加,掺气比例显著增加(P0.05);活性剂的添加促进了氧气曝气下溶解氧的增加;溶氧均匀性和流量均匀性随着活性剂浓度的增加无显著性变化,但单向传输下4 mg/L BS1000的出气均匀性较未添加活性剂显著降低;双向传输的流量均匀性、溶氧均匀性和出气均匀性分别在95%、96%和67%以上,较单向传输分别平均提高14.00%、4.05%和30.64%(P0.05),是曝气滴灌长程管道传输推荐的布置方式。研究结果为曝气滴灌过程中灌溉技术参数优化和管道的科学布置提供理论依据。

Impacts of gas source and surfactant on gas-water coupling transmission along a long-distance drip tape in one or two line layout under aerated drip irrigation

Abstract: Aerated drip irrigation (ADI) is a technique to aerate the rhizosphere by aerated water through the drip irrigation system. The dissolved oxygen (DO) in water, water flow rate and gas flow uniformity are the essential indexes for the evaluation of irrigation quality in ADI. The use of biodegradable surfactant BS1000 and the optimization of transmission modes are of great significance in the existence of microbubble and the retention of DO in water during ADI. To increase the uniformity of gas, oxygen and water and the delivery distance under ADI, transmission characteristics, i.e., gas-oxygen-water mixture produced by aerated irrigation system using Mazzei 1078 venturi air injector, were studied. The impacts of gas source and surfactant on gas-water coupling transmission along a long-distance drip tape in one or two line layout were investigated. Totally 16 combinations were tested, including 2 types of gas (air and oxygen), 2 transmission modes (one and two line transmission), and 4 levels of BS1000 concentrations (0, 1, 2 and 4 mg/L), respectively. During the experiment, parameters and uniformities of water flow rate, DO, gas void fraction (GVF), and water flow rate were observed. The DO and GVF of irrigation water along a drip tape were monitored by a dissolved oxygen meter and a vacuum device of gas void fraction measurement. Main results were given as below. Aeration treatment resulted in the slight reduce in the uniformity of water flow rate during one line transmission under ADI along a drip tape, but the DO concentration and GVF in irrigation water were significantly increased at the level of 0.05. The DO concentration in air and oxygen aerated water were increased by 160.80% and 617.05% compared with non-aerated treatment during one line transmission. However, DO levels in air and oxygen aerated water were increased by 185.26% and 643.23% compared with non-aerated treatments during two line transmission. Use of biodegradable surfactant BS1000 concentration brought an increase in GVF. Under the condition of air aerated treatment during one line transmission, the GVF at 1, 2 and 4 mg/L of BS1000 were significantly increased by 17.42%, 60.41% and 80.32% than the non-use of surfactant treatment, respectively. Similarly, under the condition of oxygen aerated treatment during one line treatment, GVF at 1, 2 and 4 mg/L of BS1000 were significantly increased by 25.00%, 55.05% and 69.27% in contrast to non-use of surfactant treatment. The use of BS1000 had a positive effect on the DO under ADI. With the increasing of BS1000 concentration, there was no significant difference neither in uniformity of DO nor water flow rate. However, compared to non-use of BS1000, the uniformity of gas flow at 4 mg/L of BS1000 was significantly decreased during one line transmission. The uniformity of water flow rate, DO and gas flow during two line transmission under ADI were higher than 95%, 96% and 67%. Compared to one line transmission, the uniformity of water flow rate, DO and gas flow during two line transmission were increased by 14.00%, 4.05% and 30.64%, respectively. Two line transmission was an optimal connection mode under ADI at the long distance of water delivery under ADI. This research will provide valuable information for optimization of aerated technique parameters and drip tape layout under ADI.