生物炭对土壤镉赋存形态和水稻镉积累的影响

发布时间：2018-01-23 11:09

本文关键词： 生物炭水稻镉有效性赋存形态根际根箱　出处：《沈阳农业大学》2017年博士论文　论文类型：学位论文

【摘要】：镉是一种对人体毒性极强的重金属。我国近年官方土壤污染状况调查公报显示,全国耕地土壤近两成存在污染物超标的问题,其中绝大多数为无机污染,而无机污染物中以镉污染超标点位所占比例最高,且远高于其他元素。水稻是受土壤镉污染危害非常严重的大宗作物,近年来关于稻米镉超标的食品安全问题已成为社会关注的热点。生物炭具备改良土壤、作物增产、增汇减排等多种环境功能效应,因其较高的孔隙度、比表面积和酸碱度等理化特性,在消除和固定各类土壤污染物的环境解毒领域广受关注。本研究以如何降低土壤镉生物有效性、减少水稻镉吸收积累两个现实问题为出发点,以明确生物炭对"土壤-水稻"体系内镉行为的影响为目的,向土壤添加生物炭作为土壤重金属污染改良剂,采取原位化学钝化修复的方式,利用多类型土壤培养试验、多年大田试验和近根际模拟试验三种研究方法,着重研究了生物炭对土壤中镉的生物有效性和赋存形态、水稻各器官镉含量与镉积累量的影响,最终探讨生物炭应用于镉污染土壤修复的潜力、机制和方式。培养试验中,以6种不同类型土壤试材模拟镉污染土壤,在不同生物炭添加比例(0、1%、5%)处理条件下、不同培养条件下(不同培养时间、是否培植稻苗)研究了生物炭对各类型土壤的生物有效性镉含量、苗期水稻镉含量的影响,试验中分别用5种提取方法(HC1法、Mehlich3法、DTPA法、CaC12法和TCLP法)测定了土壤有效性镉含量的变化情况,进而评价了提取方法的适用性。大田试验中,选择沈阳市郊一块由于污灌而形成镉污染的稻田为试验点,以不同生物炭添加量为处理(0、7.5、15.0、30.0t/hm2,3.0t/hm2/年),连续三年关注生物炭对污染水稻土壤镉赋存形态及主要理化性质、水稻各器官镉含量和积累量的变化情况。根际模拟试验中,采取三室多土层根箱法培植水稻,取得模拟水稻近根际1-5mm范围内各个层次的土壤样品,研究了添加生物炭对水稻近根际土壤有效性镉含量和水稻镉吸收积累的影响。取得的结果显示:培养条件下,1%和5%的生物炭添加能够显著降低多类型土壤条件下有效性镉含量及苗期水稻地上部分镉含量;不同有效性镉提取法提取率不同,TCLP法最低,CaC12次低,Mehlich3法与DTPA法提取效率相对较高,HC1法总体最高;DTPA法、CaCl2法和TCLP法提取结果与稻苗镉积累量相关性较好,推荐DTPA法应用于分析添加生物炭条件下土壤有效性镉含量变化。大田条件下,不同生物炭用量处理在三年中均未对水稻各器官干物质积累量产生显著影响;较高用量生物炭处理显著降低了水稻糙米、茎鞘、根系的镉含量,而对水稻叶片和稻壳镉含量影响微弱;生物炭在试验第二年显著降低了水稻多个器官的镉积累量;生物炭处理对水稻体内镉转移和积累的比例无显著影响,但能够显著降低水稻整体自土壤富集镉的比例;中高量生物炭处理能够显著降低土壤可交换态镉含量、提高铁锰氧化物结合态镉含量,对碳酸盐结合态和残渣态镉含量未有显著影响,有机结合态镉含量在试验最后一年有所提高;三年中,生物炭处理均能有效提高土壤pH和SOC。根际模拟实验中,生物炭对水稻各器官干物质积累量无显著影响,对水稻茎、鞘、糙米镉含量有显著降低作用;生物炭显著降低了水稻地上部分总镉含量、积累量,增加了水稻干物质积累量。生物炭能够降低水稻近根际土壤有效性镉含量,表现为添加生物炭缩小了水稻根系在土壤中吸收镉的有效范围。
[Abstract]:Cadmium is a heavy metal with strong toxicity to the human body. In recent years in China's official survey of Soil Pollution Bulletin shows that the cultivated soil nearly 20% existing pollutants exceed the standard problem, and most of them are inorganic pollution, and inorganic pollutants to cadmium pollution exceed the standard point accounted for the highest proportion, and far higher than other elements in rice. Is the harm of cadmium in soil bulk crops are very serious, in recent years, food safety problems on rice cadmium exceed the standard has become the focus of the society. With biochar soil, crop yield, increasing sequestration and other environmental functional effects, because of its high porosity, specific surface area and pH of physicochemical properties. Wide attention in the elimination and fixed all kinds of pollutants in the soil. The detoxification research in order to reduce the availability of soil cadmium bio, reduce rice cadmium accumulation of two practical problems as a starting Point to clear the biological carbon effect on the soil rice system of cadmium behavior for the purpose of adding biochar to soil as a soil heavy metal pollution improver, taken in situ chemical immobilization, culture test by different types of soil, years of field experiments and near rhizosphere simulation test of three kinds of research methods, focusing on the biochar on soil cadmium bioavailability and speciation of cadmium, cadmium content and accumulation in the organs of rice, finally discusses biochar application in remediation of soil contaminated with cadmium. The potential mechanism and culture test, with 6 different types of soil samples in Cd contaminated soil in different organisms, carbon proportion (0,1%, 5%) under different culture conditions (different culture time, whether to cultivate seedlings) of biochar on various types of soil bioavailable contents of cadmium, cadmium content in rice seedling. Ring, 5 extraction methods were used in the test (HC1 method, Mehlich3 method, DTPA method, CaC12 method and TCLP method) changes the effectiveness of soil cadmium content was determined, and then evaluate the applicability of the extraction method. The field test, choose a Shenyang suburb because of sewage irrigation and the formation of cadmium pollution in paddy field as the test point, to add a different amount of biochar treatment (0,7.5,15.0,30.0t/hm2,3.0t/hm2/), and the physicochemical properties of chemical speciation of cadmium contaminated paddy soil for three consecutive years to focus on biological carbon, cadmium content and accumulation in the organs of rice rhizosphere changes. In the simulation test, take three more root box method of rice cultivation. To simulate the soil samples at different levels in rice rhizosphere in the range of 1-5mm, the addition of biochar accumulation effect on rice near rhizosphere effective cadmium content in soil and rice. The results showed that cadmium culture conditions, 1% Biochar and 5% additive can significantly reduce soil conditions under multiple types of effective cadmium content in rice seedling and aboveground cadmium content; different cadmium availability extraction rate, TCLP was the lowest, CaC12 low, Mehlich3 method and DTPA extraction efficiency is relatively high, the highest total body HC1 method; DTPA method the extraction results of CaCl2 method and TCLP method and rice Cd accumulation correlated well, recommended DTPA method is applied to analyzing the effectiveness of adding cadmium content in soil biochar conditions. Under field conditions, different amount of biochar treatment in three years were not on the dry matter accumulation was significantly influenced by various organs of rice; the higher amount of biochar treatment significantly reduced the rice, stem and sheath, the CD content in root and leaves of rice husk, and cadmium content influence the weak; in the second year of biochar significantly reduced rice multiple organ cadmium accumulation; biological activated carbon treatment No significant effect on the transfer and accumulation of cadmium in rice ratio, but can significantly reduce the overall proportion of rice from soil Cd enrichment; high biomass carbon treatment can significantly reduce the soil exchangeable cadmium content, improve the bound cadmium content of iron and manganese oxides, bound and residual cadmium content had no significant influence on carbonate. The organic combination of cadmium content increased in the test last year; three years, biochar treatments could effectively improve soil pH and SOC. in rhizosphere experiment, biochar had no significant effect on the organs of rice dry matter accumulation of rice, stem, sheath, Cd content in brown rice decreased significantly; biological activated carbon significantly reduced the rice on the part of the total cadmium content, accumulation, increased dry matter accumulation of rice. The biological carbon can reduce rice near rhizosphere soil effective cadmium content, performance of biochar reduced rice roots The effective range of cadmium absorption in the soil.

【学位授予单位】：沈阳农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X53;S511

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