【作者】 宁东峰；

【导师】 梁永超；

【作者基本信息】 中国农业科学院 ， 植物营养学， 2014， 博士

【摘要】 中国是世界钢铁生产第一大国，近几年钢铁年均生产量都在7亿吨左右。钢渣是炼钢过程中的副产品，占到钢铁生产量的15-20%，但我国钢渣综合利用率只在10%，远低于发达国家，造成环境污染和资源浪费。钢渣含有Si、Ca等养分元素，是优良的硅钙肥原料，钢渣作为硅钙肥农用是实现钢渣循环利用的有效途径。但由于钢渣中同时含有少量重金属元素，农田施用会存在一定的生态环境风险。本文以钢渣农业资源化利用为核心，以钢渣硅钙肥在稻田的安全高效施用为研究目标，主要从以下几方面开展研究：首先选用两种不同的成品钢渣硅钙肥，通过盆栽试验研究不同性质的硅钙肥施用对水稻生长、产量和病害防御的影响。其次，从全国主要钢铁厂搜集不同的钢渣，对其植物有效性硅含量以及重金属的毒理性进行了测定和评估，并通过培养模拟试验，研究了几种钢渣中硅的释放规律。（1）通过温室盆栽试验研究发现：当土壤中植物有效性硅(SiO2)含量低于临界值95-110mg/kg时，施入钢渣和水淬渣两种不同的钢渣硅钙肥，都可以显著的促进水稻的生长、病害的防御和产量的形成。空气缓慢冷却型钢渣中硅的植物有效性要高于快速冷却的水淬渣。两种钢渣硅钙肥的施用显著提高了水稻茎秆和叶片中硅的含量。进一步通过扫描电镜观察到施硅显著提高了叶片表皮中硅化细胞的数目和强度以及乳突的大小和强度，有利于防止病菌的侵染。通过叶片透射电镜观察到，施硅处理提高了水稻叶片表皮细胞细胞壁硅化层的厚度，对硅的入侵起到物理防御机制。施硅处理细胞内真菌数目和侵染程度显著降低，结合以往研究推测认为，叶片内水溶性硅诱导寄主细胞从生理上抑制病原菌（Bipolaris oryzae）的生长和扩散。因此，硅在防御水稻胡麻叶斑病中物理防御机制和化学防御机制兼在。（2）通过对全国主要钢铁厂中钢渣搜集分析发现：不同钢渣中植物有效性硅含量差异很大。钢渣冷却方式对有效性硅含量影响显著，水淬渣有效性硅含量显著高于空气自然冷却钢渣有效硅含量。S3、S4、S6、S7和S8中植物有效性SiO2含量大于15%，被认为是高品质的硅肥原料。S1、S11、S12和S13中植物有效性SiO2含量范围在10-15%，可以考虑作为硅肥原料利用。S2、S5、S10和S12中植物有效性SiO2含量低于10%，不宜作为硅肥原料。钢渣中有效性硅含量与全硅含量及电导率（EC）呈显著正相关系。（3）通过对3种不同的钢渣在不同介质中培养试验研究发现：钢渣在土壤溶液中培养，第一天的硅素释放量主要由钢渣冷却方式决定，而在以后的培养过程中主要受温度的影响，其次为钢渣粒径，冷却方式影响甚微。35℃培养97天后，S1、S2与S3钢渣硅的溶出率（累积硅释放量与有效硅的比例）分别为37.3%、30.3%与27.3%；在25℃培养下，S1、S2与S3钢渣硅的溶出率分别为14.3%、7.86%与10.2%。钢渣在纯蒸馏水的培养中，第一天钢渣硅释放主要受温度的影响，而在以后的培养过程中主要受钢渣粒径的影响，温度和钢渣冷却方式对其影响甚微。在35℃，S1、S2与S3钢渣硅的溶出率分别为0.22%、0.16%与0.16%。在25℃培养下，S1、S2与S3钢渣硅的溶出率分别为0.17%、0.13%与0.14%。（4）通过对十种有效硅含量高的钢渣中重金属特性分析发现：S12和S14钢渣中Cr总量超过国家粉煤灰农用的限定标准，S7、S12与S14钢渣TCLP浸提液中Cr浓度超过了美国环保局限定的最高浓度。钢渣的TCLP浸提液中测定的Cr浓度与钢渣中Cr全量浓度并不一致，Cr的环境风险性并不单由总量决定，更大程度上决定于化学存在形态。所有搜集钢渣都不存在Cd、Pb、Hg和As等重金属元素的污染的环境风险。更多还原

【Abstract】 China is the largest producer of steel in the world with its annual crude steel output of near700Mt inrecent years. Slags are the byproducts of steel and iron industries, which account for15%-20%of globalsteel and iron production. However, the utilization of slag was only10%in China, which is far belowthat in developed countries. Disposing of these untreated slags not only requires plenty of land, but alsocauses many environmental problems. Slag contains large amounts of SiO2and CaO with smallamounts of micronutrients, it has been well documented that application of slag-based silicon (Si)fertilizer can not only improve the fertility of soils, but also enhance the growth and yield of crops andthe resistance to plant diseases. So, slag applied as Si fertilizer on paddy soil has benefits not only forrice health and growth, but also for economic and environmental issues. However, most slags containtrace amounts of heavy metals; this raises questions about the potential risks of heavy metals in slagleaching into environment. The objective of this paper was to realize steel or iron slag recycling bymeans of field application as Si-fertilizer with high efficiency and good safety. The research workmainly includes these aspects:(1) Choosing two different Si fertilizers through pot experiments toassess the effects of steel slag and iron slag applied at the same level of plant-available Si on rice growthand brown spot disease resistance and also to investigate the relationship between Si-mediatedultrastructural changes and brown spot disease infection in rice.(2) Collecting different types of slagsamples from ten steel and iron corporations in China examine phyto-available Si concentrations andthe total main chemical components, including total heavy metal concentrations of different slagmaterials. Furthermore, we aimed through BCR-and TCLP-extraction procedures to estimate thepotential mobility and leaching of metals.(3) Choosing three different steel slags to study Si-releasingcharacters from slags and their influencing factors through incubation experiments at both35oC and25oC.(1) In the pot experiment, we chose both steel and iron slags to investigate their effects on ricegrowth and disease resistance under greenhouse conditions. Scanning electron microscopy (SEM) andtransmission electron microscopy (TEM) were used to examine the effects of slags on ultrastructuralchanges in leaves of rice naturally infected with brown spot. Both Si fertilizers tested significantlyincreased rice growth and yield, and decreased brown spot incidence, with steel slag fertilizer showing astronger effect than iron slag fertilizer. Under the current experimental conditions, Si application at arate of400mg SiO2kg-1soil (available SiO2extracted by0.5M HCl) met the Si requirements of rice.SEM analysis showed that silicon application led to more pronounced cell silicification in rice leaves,more silica cells, and more pronounced and larger papilla as well. TEM analysis results showed thatmesophyll cells of silicon-untreated rice leaf were disorganized, with colonization of the fungus(Bipolaris oryzae), including chloroplast degradation and cell wall alterations. Silicon applicationpreserved mesophyll cells relatively intact and significantly increased the thickness of silicon layer. Itcan be concluded that applying Si fertilizer to Si-deficient paddy soil is necessary for both high riceyield and brown spot disease control. The immobile silicon deposited in host cell walls and papillae sites is the first physical barrier for fungal penetration and soluble Si in the cytoplasm enhancesphysiological or induced resistance to fungal colonization.(2) Steel and iron slags were collected from ten steel and iron corporations in China. The siliconphyto-availability and the main chemical components were tested. The results show that thephyto-available Si concentrations (extracted by0.5M HCl) of different slags varied widely, due todifferences in the total Si content and cooling process during slag formation. Water-cooling slagscontained more available Si than air-cooling steel slags. Slags could be divided into three classes. Thefirst class, with an available SiO2concentration greater than15%, including S3, S4, S6, S7, S8and S9represents high-grade materials for Si fertilizer. The second class, with an available SiO2concentrationbetween10%and15%, including S1, S11, S12, and S13could be considered as materials for Sifertilizer. The third class, with an available SiO2concentration is below10%(including S2, S5, S10andS12) has a low value for Si fertilizer.(3) We chose three different steel slags, including S1(in powder form, water-cooling), S2(ingranular form, water-cooling), S3(in granular form, air-cooling) with identically available Si content, tobe incubated in both soil suspension and distilled water media at35℃and25℃. Leaching solutionswere collected through centrifugation at regular intervals in order to study Si-releasing characters and itsimpacting factors. The results demonstrated that in soil suspension-incubation experiment, the rate of Sireleased from slags on the first day was mainly influenced by slag cooling process, but was impactedprincipally by temperature and grain size of slags as the experiment continued. The Si-releasingpercentage (the ratio of accumulation of Si releasing to available Si content) of S1, S2and S3were37.3%,30.3%and27.3%, respectively, after97-d-soil-incubation at35℃, compared to14.3%,7.86%and10.2%under25℃. However, in distilled water-incubation experiment, the amount of Si releasedfrom slags on the first day was mainly influenced by temperature, while afterwards it was affectedprincipally by grain size of slags and temperature but not by slag cooling process. The Si-releasingpercentage of S1, S2and S3was0.22%,0.16%and0.16%, respectively, after97-d-water-incubation at35℃, compared to0.17%,0.13%and0.14%at25℃.(4) Total chromium (Cr) concentrations in some slags far exceeded the Chinese Standard and theToxicity Characteristic Leaching Procedure (TCLP)-extractable concentrations of Cr in leachingsolutions of some slags exceeded the US EPA limit. The principal component analysis (PCA)demonstrated that the TCLP-extractable concentrations of Cr were not consistent with the total Crconcentrations in slags, but depended strongly on the European Community Bureau of Reference(BCR)-extractable chemical forms. No slags posed a significant risk of cadmium (Cd), lead (Pb),mercury (Hg) or arsenic (As) to agricultural ecosystems in which the slags are applied.更多还原