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镉(Cd)、铅(Pb)、锌(Zn)、铜(Cu)等重金属元素进入土壤环境后,可对食品安全造成危害[1-2]。其中,Cd具有极强的迁移能力,在土壤中易被农作物吸收和富集,对人类食品安全产生较大危害[3-4]。
钝化修复技术是指向污染土壤中添加钝化材料,通过吸附、沉淀等反应,阻碍土壤中重金属的迁移,从而降低重金属生物利用度的土壤修复方法[5-7]。目前,用于土壤修复的钝化材料多采用黏土矿物,如坡缕石、膨润土、海泡石、沸石等。其中,坡缕石是一种富含镁铝型黏土矿物,该矿物在我国产量丰富、价格低廉且具较强的离子交换能力和良好的吸附性能[8-9]。但是,因坡缕石自身孔道紧密且含大量杂质成分,使其使用效率较低。为此,通常需对坡缕石原矿进行改性处理。坡缕石改性方法主要分为物理方法和化学方法。常见的物理改性方法主要有高温、超声波、微波改性等;而化学改性主要以酸碱改性与有机改性为主[10]。近年来,热改性处理倍受研究者关注,但大多仅局限于热改性坡缕石的制备及水体污染修复研究[11-12]。廖启林等[13]研究表明,坡缕石因比表面积大、吸附性能强,可将土壤中可溶性重金属元素吸附在其表明或固定于矿层间结构中。而章绍康等[11]发现,温度升高可脱出坡缕石晶体内各类型水,使坡缕石孔隙度、比表面积增大,从而提高其对重金属的吸附容量。
本研究采用高温煅烧法制得热改性坡缕石,并对其物化性质进行表征;同时,考察其对土壤中Cd的钝化效果,以期为Cd污染土壤修复及坡缕石品质提升提供参考。
热改性坡缕石对土壤镉污染的钝化效果及对土壤镉生态毒性的影响
Influence of heat-modified palygorskite on stabilization remediation and ecotoxicity on Cd contaminated soil
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摘要: Cd在土壤中易被农作物吸收和富集,使农作物产量、品质降低,进而造成食品安全威胁。通过钝化实验与盆栽实验,研究了热改性坡缕石对土壤中重金属Cd的钝化效果与植物富集的影响;并结合重金属生物有效态、修复效率和植物内重金属生物吸收因子对Cd钝化效果和Cd生态毒性进行了评价。结果表明,添加4%热改性坡缕石可显著改善土壤理化性质,使土壤中生物有效态Cd质量分数(DTPA与TCLP提取态)分别由1.34 mg·kg−1(DTPA)和1.29 mg·kg-1(TCLP)降至0.58 mg·kg−1和0.57 mg·kg−1,同时可促使Cd由酸溶态转化为稳定性较强的可氧化态与残渣态。4%热改性坡缕石处理组,可显著改善玉米幼苗生长状况,使幼苗根长和株高分别增加了37.84%和35.60%,根、茎鲜重分别增加了11.41%和86.12%;同时,亦使生物吸收因子降低了44.00%,提升了土壤修复效率。热改性坡缕石具有规模化应用于土壤重金属污染原位修复的潜力。Abstract: Cadmium is easily absorbed and enriched by crops in the soil, which reduces the yield and quality of crops, thereby threatening food security seriously. To investigate the effects of heat-modified palygorskite on cadmium-contaminated soils and the impedance control of Cd uptake by plants, the incubation and pot experiments were conducted to explored the influences of heat-modified palygorskite on stabilization efficiency and accumulation of Cd contaminated soil, and the stabilization efficiency and ecotoxicity were evaluated by available content, remediation ratio of heavy metal (RRm) and biological uptaking factor (BUF). The results suggested that the physicochemical properties are significantly improved by heat-modified palygorskite with the addition of 4%, while the DTPA and TCLP extractable content of Cd decreased from 1.34 mg·kg−1 (DTPA) and 1.29 mg·kg−1 (TCLP) to 0.58 mg·kg−1 and 0.57 mg·kg−1, respectively. More acid-soluble Cd transformed into more inactive oxidizable and residual speciation with addition of heat-modified palygorskite, and the remediation ratio increased. Meanwhile, the plant growth are significantly increased the height of shoot and root by 37.84% and 35.60%, the fresh weight of shoot and root increased by 11.41% and 86.12%, while the biological uptaking factor decreased by 44.00% with the addition of 4%. The heat-modified treatment can evidently improve the stabilization function of palygorskite and do well for the growth of corn plants, which may be owing to the enhanced adsorption performance caused by the changeable-structure of the heat-modified. Therefore, the heat-modified palygorskite has the potential for large scale in-situ remediation of soils polluted by heavy metals.
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Key words:
- palygorskite /
- heat-modified /
- contaminated soil /
- stabilization /
- ecotoxicity /
- cadmium
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表 1 热改性坡缕石处理后Cd污染土壤的理化性质
Table 1. Physicochemical properties of Cd-polluted soil with heat-modified palygorskite
处理 pH 电导率/
(μS·cm−1)阳离子交换量/
(cmol·kg−1)CK 7.29±0.05d 249±23.06f 14.9±0.05e 1% 7.62±0.10c 497±8.60e 16.6±0.15d 2% 7.92±0.06b 536±21.45d 17.8±0.01c 3% 7.93±0.05b 620±1.00c 17.9±0.17c 4% 8.08±0.09a 745±8.16a 18.9±0.16a 5% 8.07±0.08a 687±2.16b 18.5±0.31b 注:同列不同字母表示各处理间存在显著差异(P<0.05)。 表 2 热改性坡缕石钝化土壤中Cd的化学形态质量分数及修复效率
Table 2. Speciation and remediation ratio of Cd in the soil stabilized by heat-modified palygorskite
处理组 酸溶态/(mg·kg−1) 可还原态/(mg·kg−1) 可氧化态/(mg·kg−1) 残渣态/(mg·kg−1) RRm/% CK 0.75±0.02a 0.59±0.01a 0.24±0.02c 0.70±0.02c 30.70±0.06d 1% 0.67±0.01b 0.57±0.01a 0.25±0.01bc 0.87±0.01b 36.86±0.02c 2% 0.57±0.03c 0.53±0.01b 0.25±0.01bc 0.89±0.02ab 37.39±0.03c 3% 0.54±0.01d 0.52±0.03bc 0.26±0.02b 0.90±0.01a 40.54±0.02b 4% 0.44±0.01e 0.50±0.01c 0.29±0.01a 0.92±0.01a 42.79±0.01a 5% 0.52±0.01d 0.51±0.01bc 0.27±0.01ab 0.90±0.02a 40.90±0.04b 注:同列不同字母表示各处理间存在显著差异(P<0.05)。 表 3 热改性坡缕石处理后玉米植株中生物富集系数(BCF)、转运系数(TF)与生物吸收因子(BUF)
Table 3. Biological concentration factor (BCF), transloocation factor (TF) and biological uptaking factor (BUF) of corn plants with heat-modified palygorskite
指标 CK 1% 2% 3% 4% 5% F值 BCF/% 3.65±0.57a 2.86±0.57b 2.43±0.88c 2.27±1.00c 1.32±1.00a 1.69±1.00d 103.00*** TF/% 58.47±0.03a 52.43±0.59c 47.92±1.00b 46.74±0.10d 31.65±0.06e 39.51±0.92d 94.50*** BUF/(mg·kg−1) 0.25±0.003a 0.21±0.009b 0.18±0.01c 0.17±0.002c 0.14±0.006d 0.15±0.015d 32.41** 注:同列不同字母表示各处理间存在显著差异;*、**和***分别表示P<0.05、P<0.01和P<0.001下的显著水平。 表 4 钝化土壤理化性质、有效态Cd质量分数、Cd化学形态与玉米生长、Cd质量分数的相关性
Table 4. Correlation coefficients among physicochemical properties of soil, bioavailable and chemical speciation of Cd, growth and enrichment of corn
检测指标 pH EC CEC Cd-DTPA Cd-TCLP 酸溶态 可还原态 可氧化态 残渣态 地上Cd质量分数 −0.92** −0.97** −0.96** 0.95** 0.98** 0.86** 0.87** −0.78** −0.83** 地下Cd质量分数 −0.93** −0.98** −0.97** 0.95** 0.98** 0.90** 0.92** −0.81** −0.86** 鲜重 0.55* 0.58* 0.54* −0.57* −0.56* −0.17 −0.24 0.34 0.51* 根长 0.70* 0.72* 0.72* −0.71* −0.69* −0.42 −0.54 0.36 0.69* 株高 0.66* 0.66* 0.66* −0.63* −0.56* −0.39 −0.45 0.29 0.78** 注:同列不同字母表示存在显著差异;*、**和***分别表示P<0.05、P<0.01和P<0.001下的显著水平。 -
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