摘要
为农田土壤修复筛选合适的镉钝化剂,通过盆栽试验,设置10个钝化剂处理:T1(矿石、纳米生物炭等)、T2(生石灰)、T3(牡蛎壳等)、T4(CaO)、T5(硅钙肥)、T6(羊粪有机肥)、T7(枯草芽孢杆菌等)、T8(猪粪有机肥)、T9(牡蛎壳)及T10(微生物等),比较研究10种钝化剂对镉污染稻田的修复效果及水稻生长的影响。结果显示,钝化剂可以提高稻田土壤的pH,并改变土壤镉的赋存形态。各处理土壤可交换态镉含量较对照下降4.6%~44.8%,其中T8(44.8%)、T6(36%)、T1(31.15%)、T10(28.4%)下降幅度较大;碳酸盐结合态含量上升;铁锰氧化物结合态及有机物结合态的含量变化不明显;残渣态镉的比例呈现上升趋势,T6处理上升幅度最大,较CK增加53.85%。各钝化剂处理水稻籽粒生物量增加5.75%~25.30%。水稻籽粒、稻壳和秸秆的Cd含量呈现秸秆>籽粒>稻壳的规律,籽粒镉含量在0.068~0.254 mg/kg,T2(0.152 mg/kg)、T5(0.143 mg/kg)、T6(0.088 mg/kg)、T7(0.126 mg/kg)、T8(0.072 mg/kg)、T9(0.068 mg/kg)和T10(0.071 mg/kg)7个钝化剂处理低于国家限量标准(0.2 mg/kg),其中T6、T8、T9、T10籽粒镉含量较CK分别下降了61.90%、68.83%、70.56%、69.26%,降幅较大。综合土壤镉形态转化、水稻生物量和籽粒镉含量来看,钝化效果较好的是T2(生石灰)、T6(羊粪有机肥)和T8(猪粪有机肥)处理。
工矿企业的发展和农用化学品用量的递增使得大量重金属,尤其是镉(Cd)进入了农田。2014年国家环境保护部与国土资源部联合发布的《全国土壤污染状况调查公报》(https://www.gov.cn/foot/2014-04/17/content_2661768.htm)显示,我国土壤中镉污染物点位超标率为7.0%,约有34%的农田土壤存在不同程度的镉污染问题,导致每年粮食产量直接减少约100亿kg。水稻是我国主要的粮食作物之一,由于水稻对镉的生理耐受性和积累能力均较
目前镉污染土壤治理方法分为物理修复法、化学修复法、生物修复法
取自某矿区附近的镉污染稻田表层(0~20 cm)土壤,将杂质剔除、混匀,自然风干,过筛,测定土壤基本性质为:pH(m水∶m土=2.5∶1)6.82,有机质29.18 g/kg 、全氮1.83 g/kg、全磷0.57 g/kg、全钾19.16 g/kg、碱解氮161.55 mg/kg、速效钾140.00 mg/kg、有效磷8.20 mg/kg,总镉含量为4.70 mg/kg(有效态0.91 mg/kg),超过农用地土壤污染风险管制值(3.0 mg/kg)。
供试水稻品种为两优8106,是安徽荃银高新种业有限公司育成的籼型两系杂交水稻品种。
水稻种子消毒、漂洗,去离子水中冲洗、浸泡后,悬浮于尼龙纱网上发芽。幼苗萌发后,置于Kimura营养液培养30 d。光源为阳光,光照时间为(13.5±0.03) h,环境平均温度是24 ℃,平均湿度是60%。为补充水稻生长所需的水分和养分,每隔5 d更换1次营养液,共更换6次。其中前2周使用1/4浓度营养液,第3周使用1/2浓度营养液,之后使用全营养液。
采用10种钝化剂进行盆栽模拟试验,同时设置对照(CK),每个处理重复3次,共33盆,不同钝化剂材料组成见
处理 Treatment | 主要材料 Main materials | 处理 Treatment | 主要材料 Main materials |
---|---|---|---|
T1 | 矿石、纳米生物炭等 | T6 | 羊粪有机肥 |
T2 | 生石灰 | T7 | 枯草芽孢杆菌、胶冻样类芽孢杆菌 |
T3 | 牡蛎壳、石灰石、矿源腐殖酸甜叶菊渣 | T8 | 猪粪有机肥 |
T4 | CaO | T9 | 牡蛎壳 |
T5 | 硅钙肥 | T10 | 微生物、菌类、玉米淀粉、氯化钠、蛋白胨 |
土壤加入钝化剂和基肥后,按m水∶m土=2.5∶1加入去离子水,模拟水稻土田间水分状况,保持淹水状态培养1周,之后移入培育好的水稻幼苗。水稻生长过程中及时防治病虫害并除草。
分别于水稻生长的分蘖期(移栽后15~20 d)、孕穗期(移栽后30 d左右)、抽穗期(水稻穗随茎秆生长而伸出顶部叶)、成熟期采用三点法取0~20 cm表层土样,自然风干、研磨、过筛,测定土壤pH和镉形态。其中土壤pH用酸度计测定(m水∶m土=2.5∶1)。土壤总镉依据GB/T 17141-1997《土壤质量铅、镉的测定石墨烯原子吸收分光光度法》测定。土壤镉形态采用Tessier连续提取法进行提取测
水稻收获后,分成籽粒、稻壳、秸秆3部分并测定鲜质量,杀青后烘干至恒质量,测定并记录不同部位干质量及镉含量。水稻秸秆、稻壳、籽粒中的镉根据GB 5009.15-2014《食品安全国家标准食品中镉的测定》测定。
1)分蘖期。由

图1 分蘖期土壤Cd形态分布
Fig.1 Forms distribution of soil Cd during tillering stage
2)孕穗期。由

图2 孕穗期土壤Cd形态分布
Fig.2 Forms distribution of soil Cd during the booting period
3)抽穗期。

图3 抽穗期土壤Cd形态分布
Fig.3 Forms distribution of soil Cd during the heading stage
4)成熟期。由

图4 成熟期土壤Cd形态分布
Fig.4 Forms distribution of soil Cd during the maturity stage
由
处理 Treatment | 分蘖期 Tillering stage | 孕穗期 Booting period | 抽穗期 Heading stage | 成熟期 Maturity stage |
---|---|---|---|---|
CK | 6.81±0.02e | 6.86±0.04d | 7.02±0.05d | 6.84±0.05d |
T1 | 7.08±0.12cd | 7.10±0.06c | 7.15±0.29cd | 7.43±0.07bc |
T2 | 7.32±0.07ab | 7.43±0.09b | 7.35±0.08bc | 7.56±0.08b |
T3 | 6.98±0.05d | 7.19±0.12c | 7.40±0.16bc | 7.43±0.15bc |
T4 | 7.12±0.03cd | 7.23±0.05c | 7.52±0.03b | 7.51±0.06b |
T5 | 7.07±0.09cd | 7.19±0.06c | 7.60±0.02b | 7.32±0.04c |
T6 | 7.20±0.04bc | 7.20±0.06c | 7.62±0.25b | 7.56±0.04b |
T7 | 7.10±0.08cd | 7.09±0.11c | 7.56±0.09b | 7.41±0.12bc |
T8 | 7.45±0.06a | 7.99±0.04a | 8.24±0.13a | 8.14±0.06a |
T9 | 7.05±0.07cd | 7.14±0.02c | 7.56±0.25b | 7.44±0.18bc |
T10 | 7.07±0.08cd | 7.11±0.07c | 7.42±0.21bc | 7.46±0.07bc |
注: 同列不同小写字母代表不同处理间差异显著(P<0.05)。下同。 Note:Different lowercase letters after the same data in the same columns indicate significant differences(P<0.05).The same as below.
如

图5 成熟期不同钝化剂处理下水稻籽粒(A)、稻壳(B)和秸秆(C)干质量
Fig.5 Dry mass of seeds(A ),husk(B) and straw(C) of rice at maturity stage under different passivators
柱子上不同小写字母代表不同处理间差异显著(P<0.05)。下同。 Note:Different lowercase letters in the same column indicate significant differences(P<0.05).The same as beolw.
1)施用钝化剂对水稻籽粒、稻壳、秸秆镉含量的影响。由
处理 Treatment | 秸秆 Straw | 稻壳 Rice husk | 籽粒 Seeds |
---|---|---|---|
CK | 2.42±0.087d | 0.175±0.085abc | 0.231±0.079abc |
T1 | 2.85±0.008cd | 0.194±0.052ab | 0.219±0.052ab |
T2 | 3.66±0.56a | 0.120±0.046bcd | 0.152±0.05bcd |
T3 | 3.52±0.273ab | 0.224±0.126a | 0.254±0.127a |
T4 | 3.03±0.667bc | 0.170±0.026abc | 0.240±0.026ab |
T5 | 0.97±0.1f | 0.125±0.026bcd | 0.143±0.026bcd |
T6 | 0.84±0.136f | 0.053±0.042d | 0.088±0.046d |
T7 | 1.17±0.187f | 0.082±0.034cd | 0.126±0.033cd |
T8 | 3.79±0.176a | 0.058±0.009d | 0.072±0.009d |
T9 | 1.88±0.062e | 0.039±0.013d | 0.068±0.012d |
T10 | 1.91±0.37e | 0.041±0.035d | 0.071±0.025d |
2)施用钝化剂对水稻籽粒、稻壳、秸秆镉积累量的影响。由

图6 不同钝化剂处理下水稻不同部位镉积累量
Fig.6 Cadmium accumulation of rice under different passivators treatments
据Tessier
大量研究表明,pH和土壤镉的迁移转化、赋存形态及生物有效性等因素密切相关,pH变化是镉污染修复效果的关键因
本研究中,各钝化剂均不同程度增加了水稻的产量和生物量,钝化剂处理的籽粒生物量较对照增加5.75%~25.30%,稻壳生物量提高了10.58%~42.91%。综合水稻生长指标,钝化剂效果最为显著的是T1、T2和T8。钝化剂成分大部分为有机质、硅钙肥和微生物制剂等,不同程度改善了水稻的土壤环境质量,增加了土壤的养分供应,促进了水稻的生长和发
水稻籽粒、稻壳和秸秆的Cd含量呈现秸秆>籽粒>稻壳的规律,籽粒镉含量在0.068~0.254 mg/kg,其中T2(0.152 mg/kg)、T5(0.143 mg/kg)、T6(0.088 mg/kg)、T7(0.126 mg/kg)、T8(0.072 mg/kg)、T9(0.068 mg/kg)和T10(0.071 mg/kg)7个处理的镉含量均低于GB 2762-2022镉含量的限定标准(0.2 mg/kg),且T6、T8、T9及T10处理籽粒镉含量分别较CK下降了61.90%、68.83%、70.56%、69.26%。水稻秸秆的镉积累量以T5、T6及T7处理为最低,与CK相比分别下降了56.4%、66.0%、53.7%。蔡秋玲
综上,镉污染土壤中添加钝化剂可以有效增加土壤的pH,改变土壤镉的赋存形态,促进活性较强的可交换态镉转变为其他相对比较稳定的形态尤其是残渣态,降低土壤中镉的有效性,减少镉向水稻地上部分的迁移和积累从而降低籽粒中镉的富集。施用钝化剂可增加水稻产量,降低水稻的镉含量。综合土壤中镉赋存形态的改变、水稻农艺性状及水稻镉含量,10种钝化剂中,镉污染土壤修复效果最好的是T2(生石灰)、T6(羊粪有机肥)和T8(猪粪有机肥)。
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