Institute of Resource, Ecosystem and Environment of Agriculture, Nanjing Agricultural University, Nanjing 210095, China.
J Environ Sci (China). 2009;21(5):618-24. doi: 10.1016/s1001-0742(08)62316-5.
Effects of free iron oxyhydrates (Fe(d)) and soil organic matter (SOM) on copper (Cu2+) sorption-desorption behavior by size fractions of aggregates from two typical paddy soils (Ferric-Accumulic Stagnic Anthrosol (Soil H) and Gleyic Stagnic Anthrosol (Soil W)) were investigated with and without treatments of dithionite-citrate-bicarbonate and of H2O2. The size fractions of aggregates were obtained from the undisturbed bulk topsoil using a low energy ultrasonic dispersion procedure. Experiments of equilibrium sorption and subsequent desorption were conducted at soil water ratio of 1:20, 25 degrees C. For Soil H, Cu2+ sorption capacity of the DCB-treated size fractions was decreased by 5.9% for fine sand fraction, by 40.4% for coarse sand fraction, in comparison to 2.9% for the bulk sample. However, Cu2+ sorption capacities of the H2O2-treated fractions were decreased by over 80% for the coarse sand fraction and by 15% for the clay-sized fraction in comparison to 88% for bulk soil. For Soil W, Cu2+ sorption capacity of the DCB-treated size fraction was decreased by 30% for the coarse sand fraction and by over 75% for silt sand fraction in comparison to 44.5% for the bulk sample. Cu2+ sorption capacities of the H2O2-treated fractions were decreased by only 2.0% for the coarse sand fraction and by 15% for the fine sand fraction in comparison to by 3.4% for bulk soil. However, Cu2+ desorption rates were increased much in H2O2-treated samples by over 80% except the clay-sized fraction (only 9.5%) for Soil H. While removal of SOM with H2O2 tendend to increase the desorption rate, DCB- and H2O2-treatments caused decrease in Cu2+ retention capacity of size fractions. Particularly, there hardly remained Cu2+ retention capacity by size fractions from Soil H after H2O2 treatment except for clay-sized fraction. These findings supported again the dominance of the coarse sand fraction in sorption of metals and the preference of absorbed metals bound to SOM in differently stabilized status among the size fractions. Thus, enrichment and turnover of SOM in paddy soils may have great effects on metal retention and chemical mobility in paddy soils.
采用低能超声分散法从原状表层土壤中分离得到大小不同的团聚体颗粒级分，研究了高铁-累积性潜育水稻土（土壤 H）和潜育性水稻土（土壤 W）团聚体中不同大小颗粒级分中铁氧氢化物（Fe(d)）和土壤有机质（SOM）对铜（Cu2+）吸附-解吸行为的影响，以及在连二亚硫酸钠-柠檬酸-碳酸氢钠和过氧化氢处理前后铜的吸附和解吸平衡实验。实验在水土比为 1:20、25°C 条件下进行。对于土壤 H，与原状土样相比，连二亚硫酸钠处理的细砂级分中 Cu2+的吸附量减少了 5.9%，粗砂级分减少了 40.4%，而粗砂级分减少了 2.9%。然而，过氧化氢处理的粗砂级分的 Cu2+吸附量减少了 80%以上，而粘粒级分减少了 15%，而原状土样减少了 88%。对于土壤 W，与原状土样相比，连二亚硫酸钠处理的粗砂级分中 Cu2+的吸附量减少了 30%，而粗砂级分减少了 75%以上，而原状土样减少了 44.5%。过氧化氢处理的粗砂级分的 Cu2+吸附量仅减少了 2.0%，细砂级分减少了 15%，而原状土样减少了 3.4%。然而，除粘粒级分外（仅 9.5%），过氧化氢处理的样品的 Cu2+解吸速率增加了 80%以上。而用 H2O2 去除 SOM 则倾向于增加解吸速率，而 DCB 和 H2O2 处理则降低了颗粒级分对 Cu2+的保持能力。特别是，用 H2O2 处理后，除粘粒级分外，土壤 H 的各颗粒级分对 Cu2+的保持能力几乎丧失。这些发现再次支持了粗砂级分在金属吸附中的主导地位，以及不同稳定状态下与 SOM 结合的吸附金属的偏好。因此，稻田土壤中 SOM 的富集和转化可能对稻田土壤中金属的保持和化学迁移有很大影响。
