烟气脱硫石膏对围垦滩涂土壤的脱盐作用

Effects of Flue Gas Desulfurization (FGD) Gypsum on Desalination of Reclaimed Tidal Flat Soil

  • 摘要: 依靠自然降水淋洗和植物演替,围垦滩涂土壤脱盐需要数十年。烟气脱硫石膏可以通过钙(Ca2+)钠(Na+)交换将这一自然脱盐过程缩短到数年内。自2011年起,在长江三角洲崇明岛围垦滩涂进行了现场试验,烟气脱硫石膏的施用量为0,15,30,45和60 t/hm2。结果表明,在年平均降雨量为1 050 mm的条件下,施用烟气脱硫石膏的第2年,滩涂盐碱地表层土壤(0~30 cm)脱盐效果明显,用土壤交换性钠百分率表达的土壤碱化度(ESP)下降了53%。滩涂草本植物的物种数量和覆盖度随烟气脱硫石膏施用比例增加而提高(P<0.05),在现场1 m×1 m样方中发现有盐生草本碱蓬、蒲公英、野艾蒿,甚至苜蓿和喜旱莲子草等非盐生植物取代了原优势盐生植物芦苇。较高烟气脱硫石膏处理过的围垦滩涂木本植物的成活率也明显高于未处理的控制地块(P<0.05)。安全使用烟气脱硫石膏可望大规模地有效改善围垦滩涂盐碱土壤质量和生态环境。

     

    Abstract: Soil desalination of reclaimed tidal land by natural processes of rain washing and plant community succession needs several decades. Using flue gas desulfurization (FGD) gypsum as soil amendments can accelerate this natural process of desalination to within a couple of years by replacing exchangeable sodium (Na+) with calcium ions (Ca2+). Field experiments in a reclaimed tidal land located at Chongming Island of Yangtze River Delta had been conducted with FGD gypsum at rates equivalent to 0, 15, 30, 45, 60 t/hm2 since 2011. The results showed that under the condition of 1 050 mm annual precipitation and two years after FGD gypsum treatment, the desalination effect of top soil (0-30 cm) was significant, and degree of soil alkalization measured as exchangeable sodium percentage (ESP) decreased by 53%. Species number and coverage of herbaceous plants increased with increasing rates of FGD gypsum (P<0.05). Instead of dominated species reed, some halophytic herbs like Suaeda glauca, Herba taraxaci, Artemisia lavandulaefolia, and even non-halophytic Medicago sativa and Alternanthera philoxeroides were found in the 1 m×1 m quadrats. Survival rates of woody plants on higher FGD gypsum treatments were also significantly higher than that of controls (P<0.05). It is expected that safe levels of FGD gypsum can be applied effectively to remediate saline soil of reclaimed tidal lands on a large scale.

     

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