改性纳米TiO2对污染土壤砷形态及土壤性质的影响

基于纳米TiO₂对土壤砷的稳定效果,以自制的改性纳米TiO₂(活性炭负载纳米二氧化钛TiO₂/AC和铁改性活性炭负载纳米二氧化钛 Fe-TiO₂/AC)为试验材料,通过室内模拟试验,研究改性纳米TiO₂对土壤砷形态、土壤pH、土壤养分及土壤酶活性的影响。结果表明:在2种改性纳米TiO₂的作用下,土壤中砷活性较强的非专性和专性吸附态均降低,惰性的砷无定形和弱结晶水合铁铝氧化物结合态和残渣态均升高。土壤pH随改性纳米TiO₂施用量的增加而升高,速效钾含量均增加,而土壤有效氮减少。在TiO₂/AC和Fe-TiO₂/AC作用下,土壤pH分别为7.07~7.21、7.28~7.43。施加TiO₂/AC和Fe-TiO₂/AC,速效钾的增幅分别为17.2%~32.2%和28.7%~29.5%,有效氮含量降幅分别为25.1%~37.8%和23.5%~44.6%。2种改性纳米TiO₂对土壤中性、碱性磷酸酶的活性均有激活作用;TiO₂/AC对土壤过氧化氢酶和脲酶活性具有一定的抑制作用,但铁改性后的Fe-TiO₂/AC抑制作用减弱,且在施加量为0.3%土壤过氧化氢酶活性比对照提高了19.5%;施加TiO₂/AC后土壤脲酶活性下降范围为63.0%~76.6%,但在0.4%Fe-TiO₂/AC作用下,土壤脲酶活性较对照上升了5.8%。可见,改性纳米TiO₂可以使土壤中砷由活性态向惰性态转化,对土壤性质的影响可通过铁改性来进行控制。

EFFECT OF MODIFIED NANO-TIO2 ON ARSENIC SPECIES AND ENZYME ACTIVITY IN ARSENIC CONTAMINATED SOIL

Based on the stabilizing effect of nano-TiO₂ dioxide on soil arsenic, using self-made modified nano-TiO₂ (TiO₂/AC and Fe-TiO₂/AC) as the test material, the effects of modified nano-TiO₂ on the speciation of As, soil pH, nutrients and enzymatic activities were studied through indoor simulation experiments. The results showed that: with the action of TiO₂/AC and Fe-TiO₂/AC, the non-specific adsorption state and obligate adsorption state of arsenic with strong activity in soil decreased by 1.1%~6.3%, 1.8%~9.5% and 2.1%~6.9%, 10.1%~18%, respectively. While the bound and residual states of inert arsenic amorphous and weakly crystalline hydrated iron-aluminum oxides increased by 1.0%~14.8%, 2.2%~10.5% and 3.7%~16.9%, 6.5%~16.7%, respectively. With the action of TiO₂/AC and Fe-TiO₂/AC, the soil pH increased by 0.05~0.13 and 0.20~0.35, respectively. The increase rates of available potassium were 17.2%~32.2% and 28.7%~29.5%, and the decrease rates of available nitrogen content were 25.1%~37.8% and 23.5%~44.6%, respectively. Two kinds of modified nano-TiO₂ all had activating effect on soil neutral and alkaline phosphatase activity. TiO₂/AC had an inhibiting effect on activity of urease and catalase, and after iron modification, its inhibiting effect tended to be weaker. The soil catalase activity increased by 19.5% compared with the control when the application amount was 0.3%; the soil urease activity decreased by 63.0%~76.6% after applying TiO₂/AC, but under the action of 0.4% Fe-TiO₂/AC, the soil urease activity decreased by 63.0%~76.6%. Urease activity increased by 5.8% compared with the control. In short, the modified nano-TiO₂ transformed arsenic in soil from active states to inert states, and the influence on the soil properties could be controlled by iron modification.