聚丙烯酸钠(SP)保水剂对不同基质氮、磷、钾、钠淋溶的影响

保水剂正逐步运用于干旱半干旱地区的水土保持和节水农业中,而聚丙烯酸钠(SP)是其中一种重要的保水剂.为了弄清保水剂对元素淋溶的影响,进行了水解污泥、湖泊底泥、山地黄壤3种基质,4种SP添加比例(0、1.0%、2.5%、4.0%)的淋溶试验,并分析测定了淋溶液中的氮、磷、钾、钠.结果表明,添加SP使水解污泥、湖泊底泥和山地黄壤的氮总淋溶量分别增加了67.8%、37.0%和95.7%,磷总淋溶量分别增加了151%、436%和219%.3种基质氮淋溶量的分配相同,而磷淋溶量的分配不同,说明不同基质中淋溶氮的类型相同,淋溶磷的类型不同.添加SP使水解污泥钾的总淋溶量增加了大约19%,而对湖泊底泥钾的总淋溶量无显著影响,却使山地黄壤钾的淋溶量降低了约67%,SP对钾淋溶的影响效果受基质类型和SP本身所含钠的影响.不同基质钠淋溶量都随SP添加比例的增加而显著增加,但它们淋溶量的分配模式各不相同,说明不同基质钠的来源不同.水解污泥淋溶的钠主要来自基质本身钠的活化,湖泊底泥淋溶的钠主要来自基质的活化和SP中的钠,而山地黄壤淋溶的钠主要来自SP中的钠.总之,SP保水剂处理下的元素淋溶量及其分配受SP比例、基质类型和元素类型影响,使用SP保水剂既能活化基质的氮、磷等养分,有利于植物生长,也具有增加钠离子从而导致土壤碱化的风险.

The effects of sodium polyacrylate (SP) on the leaking of N, P, K and Na in different substrates

Super absorbent polymer (SAP) has been increasingly used for agriculture-related soil, water conservation and water-saving in arid and semiarid areas. Sodium polyacrylate (SP) is an important SAP. A leaking experiment with three substrates of hydrolytic sludge, lake sediment and mountain yellow earth and with the SP addition rates of 0, 1.0%, 2.5% and 4.0% was conducted, and the N, P, K and Na in the leaked liquid were measured to understand the effects of SAP on elements leaking. The results showed that SP addition increased 67.8%, 37.0% and 95.7% of total N leaking and 151%, 436% and 219% of total P leaking in hydrolytic sludge, lake sediment and mountain yellow earth, respectively. Results implied that the type of leaked N was similar but the type of leaked P was different in different substrates. SP addition increased about 19% of K leaking in hydrolytic sludge, did not significantly affect the K leaking in lake sediment, and decreased about 67% of K leaking in mountain yellow earth. The effects of SP on K leaking may be related to the type of substrate and Na content in SP. Na leaking in hydrolytic sludge, lake sediment and mountain yellow earth increased significantly with the increasing addition rate of SP, but their allocation patterns suggested different sources of leaked Na in different substrates. The leaked Na in hydrolytic sludge was mainly from the activation of Na itself. In lake sediment, it was originated from the substrate and SP, while in mountain yellow earth, it was mainly from SP. In conclusion, the effects of SP addition on element leaking were controlled by the rates of SP addition and the types of substrates and elements. The SP application could benefit plant growth by activating N and P, but might cause the risk of Na⁺ increasing that would lead to soil alkalinization.