黏土矿物对农田重金属Cd污染土壤修复效果研究

发布时间：2018-06-19 12:55

本文选题：黏土矿物 + 污染土壤　；参考：《沈阳农业大学》2017年硕士论文

【摘要】：目前,我国农田土壤重金属污染形势日趋严峻,其中镉(Cd)污染最为普遍,尤其在城市与工矿区周边。由于重金属Cd具有迁移性强,易被植物吸收等特点,土壤Cd污染问题受到人们的广泛关注。黏土矿物钝化修复措施是治理农田Cd污染土壤常用方法,正在得到越来越多的示范应用,但黏土矿物修复Cd污染土壤的长期效果及多方面影响,是亟需关注和研究的问题。本研究分别以海泡石和凹凸棒石作为修复材料,通过外源添加Cd元素,对农田重金属Cd污染土壤进行钝化修复盆栽试验,研究两种黏土矿物在不同比例施加量下,对玉米地上各部位Cd含量、土壤pH及有效态Cd含量等变化的影响,用以表征修复效果。同时设计土柱淋滤试验,模拟不同频率降雨量及降雨强度降水条件下,对施加不同比例海泡石处理土柱中土壤重金属Cd随径流作用的迁移特征,分析淋滤液和土壤中pH、Cd全量及有效态Cd含量的变化规律,以研究其迁移特征。(1)在两种土壤Cd污染水平下,从适宜作物生长和对作物毒害程度来看,施加海泡石比凹凸棒石对降低作物茎叶及籽粒中Cd含量的作用更有效,且成本较低。在两种黏土矿物不同施加量条件下,均为土壤5mg kg~(-1)Cd浓度对玉米株高影响比2 mg kg~(-1)明显,不同时期趋势一致,而玉米生长各时期内,两种黏土矿物对株高的影响,与施Cd水平有关。与未添加黏土矿物的对照组相比,按不同比例施加两种黏土矿物均有不同程度提高作物的生物量,但未达到显著水平。玉米植株地上各部位Cd含量均随着土壤中Cd含量的增大而增加,其分布大小为玉米籽粒玉米茎玉米叶。(2)土壤pH变化是黏土矿物钝化修复Cd污染土壤的一个重要因素。盆栽土壤0～10 cm 土层pH均高于10～20 cm 土层,且随着两种黏土矿物施加量的增加而升高;按不同比例施加两种黏土矿物均能有效降低土壤中有效态Cd含量,且具有显著性差异(P0.05)。土壤pH升高,能改变土壤中Cd的存在形态,进而降低了 Cd的迁移性和生物有效性,缓解了 Cd对玉米和土壤的损伤和危害。(3)土柱淋滤试验中,不同比例施加海泡石的土柱经淋滤处理,8个淋滤柱持水量大小顺序为 C1H1C1H2C2H3C1HCK1C2H1C2H2CK2;淋滤液 pH 值均在6.5～8.0之间。淋滤强度会影响入渗速率的大小,淋滤强度越大,入渗速率越大;同时淋滤液中Cd含量也会随之减少。在两种Cd污染土壤水平下,施加海泡石的土柱中Cd含量均低于对照组,施加量分别为1%和1.5%时,对淋滤液中Cd淋失量影响最大。(4)两种Cd污染土壤下,与对照组相比,施加不同比例海泡石对Cd污染土壤不同深度Cd含量影响显著(P0.05);且重金属Cd有不同程度的纵向向下迁移现象。对照组Cd污染土壤在20～30 cm 土层(此层原始土壤中Cd含量为0.46 mg kg~(-1))Cd含量分别为0.90mg kg~(-1) 和 1.82mg kg~(-1),增加了0.4mg kg~(-1) 和 1.36mgkg~(-1);施加海泡石进行处理能有效地抑制重金属Cd向下层迁移,其中在两种土壤Cd污染水平下,分别施加1%和1.5%的海泡石对土壤中Cd向下迁移变化最大,分别减少到0.50 mg kg~(-1)和0.44 mg kg~(-1)。(5)对盆栽土壤进行浸出试实验分析得出:除C1A2处理外,10～20 cm 土层浸出Cd含量均高于0～10 cm 土层,这表明重金属Cd污染土壤经过耕种和黏土矿物钝化处理后仍有向下迁移的现象。其中5 mg kg~(-1)Cd污染土壤较2 mg kg~(-1)Cd污染土壤中Cd浸出量降低效果显著,且凹凸棒石施加量为1.5%时,对0～10 cm土层Cd浸出量影响最大,减少了 0.132 ug L~(-1)(33.8%);海泡石施加量为1.5%时,对10～20 cm 土层Cd浸出量影响最大,减少了 0.213 ugL~(-1)(46.0%)。
[Abstract]:At present, the situation of heavy metal pollution in farmland soil is becoming more and more severe in China, among which cadmium (Cd) pollution is the most common, especially in the vicinity of city and industrial and mining area. Because the heavy metal Cd has the characteristics of strong mobility, easy to be absorbed by plants and so on, the problem of soil Cd pollution is widely concerned. The remediation measures of clay mineral passivation are the control of farmland Cd polluted soil. More and more demonstration applications are being used, but the long-term effect and multifaceted effect of clay minerals in the remediation of Cd contaminated soil is a problem which needs attention and research. This study uses sepiolite and attapulgite as repair material, and by adding exogenous Cd elements, the soil of heavy metal Cd polluted by heavy metals in farmland is passivated to repair potted plants The experiment was conducted to study the effects of two clay minerals on the changes of Cd content, soil pH and the content of effective Cd in different parts of the corn on different proportions. The soil column leaching test was designed to simulate the different proportions of sepiolite treatment soil column under different frequency of rainfall and rainfall intensity. The change of the soil heavy metal Cd with the migration of runoff, the variation of pH, Cd and Cd content in the leachate and soil was analyzed in order to study the migration characteristics. (1) under the Cd pollution level of two soils, the imposition of sepiolite to the plant growth and the degree of crop toxicity was applied to the decrease of C in the stems and leaves and grains in the crops. The effect of D content is more effective and lower in cost. Under the conditions of different application of two clay minerals, the effect of soil 5mg kg~ (-1) Cd concentration on maize plant height is more obvious than that of 2 mg kg~ (-1), and the trend in different periods is consistent, but the effect of two clay minerals on plant height in each period of maize growth is related to the level of Cd. Compared with the control group, two kinds of clay minerals were applied in different proportions to increase the biomass of the crop, but it did not reach the significant level. The content of Cd in all parts of the maize plant increased with the increase of Cd content in the soil, and the distribution was the maize grain corn stalk jade rice leaf. (2) the soil pH change was the clay mineral passivation repair. Cd contaminated soil was an important factor. The 0~10 cm soil layer pH in potted soil was higher than the 10~20 cm soil layer, and increased with the increase of the amount of two clay minerals. Applying two clay minerals in different proportions could effectively reduce the content of effective Cd in the soil, and had significant difference (P0.05). The soil pH increased and could change the Cd in the soil. The existence form, thus reducing the mobility and bioavailability of Cd, alleviates the damage and harm of Cd to maize and soil. (3) in soil column leaching test, the soil column of sepiolite is leached with different proportion of sepiolite, and the order of water holding capacity of the 8 leaching columns is C1H1C1H2C2H3C1HCK1C2H1C2H2CK2, and the pH value of the filtrate is between 6.5 and 8. The leaching strength will affect the size of infiltration rate, the greater the leaching strength, the greater the infiltration rate, and the decrease of Cd content in the filtrate. Under the level of two kinds of Cd contaminated soil, the content of Cd in the soil column of sepiolite is lower than that of the control group. When the application amount is 1% and 1.5%, the Cd leaching loss in the filtrate is the most. (4) two kinds of Cd pollution. Compared with the control group, the effect of different proportion of sepiolite on the Cd content in different depth of Cd contaminated soil was significant (P0.05), and the heavy metal Cd had different degrees of vertical downward migration. The Cd contaminated soil in the control group was 0.46 mg kg~ (-1) in the 20~30 cm soil layer. And 1.82mg kg~ (-1), increased 0.4mg kg~ (-1) and 1.36mgkg~ (-1), and imposing sepiolite treatment could effectively inhibit the heavy metal Cd downward migration. Under the two soil Cd pollution levels, 1% and 1.5% sepiolite were applied to the Cd downward migration in the soil, which were reduced to 0.50 mg and 0.44 respectively. (5) The leaching experiment of potted soil shows that, except for C1A2 treatment, the content of Cd in 10~20 cm soil layer is higher than that of 0~10 cm soil layer, which indicates that the heavy metal Cd contaminated soil still has the downward migration after the cultivation and the clay mineral passivation treatment. The 5 mg kg~ (-1) Cd contaminated soil is more than 2 mg kg~ (-1) contaminated soil. The effect is significant, and when the amount of palygorskite is 1.5%, the Cd leaching amount of the 0~10 cm soil layer is most affected, and 0.132 UG L~ (-1) (33.8%) is reduced. When the imposition of sepiolite is 1.5%, the leaching amount of Cd in the 10~20 cm soil layer is most affected, and 0.213 ugL~ (-1) (46%) is reduced.
【学位授予单位】：沈阳农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53

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