根系分泌物典型组分对生物炭胶体稳定性和迁移能力的影响

根系分泌物是可溶性有机质的主要来源,能够在一定程度上影响胶体在多孔介质中的稳定性和迁移行为。随着生物炭的广泛应用,探究土壤中的根系分泌物对生物炭胶体在地下环境中稳定性和迁移能力的影响非常重要。通过室内聚集和迁移实验探究了根系分泌物的典型组分半乳糖（Gal）、赖氨酸（Lys）以及乙酸（AcOH）对小麦生物炭（WB）和松树木屑生物炭（PB）胶体的稳定性和迁移特性的影响。结果表明：典型根系分泌物组分浓度高低对生物炭颗粒ζ电势具有一定的影响。半乳糖和赖氨酸浓度较低时,其对生物炭胶体聚集和迁移影响较小,难以对生物炭的环境行为造成显著影响;但是乙酸可以明显降低生物炭胶体在NaCl溶液中的稳定性,抑制生物炭胶体在多孔介质中的迁移能力。这可能是因为乙酸中有机酸阴离子容易与生物炭表面含氧官能团形成氢键,增加了生物炭对乙酸的吸附,降低了生物炭胶体的稳定性。     

生物膜和土壤矿物对人工纳米颗粒在饱和多孔介质传输的影响

本文探究了人工纳米颗粒(NPs)在饱和多孔介质中的传输规律和影响机制，重点阐明生物膜和土壤矿物对纳米颗粒传输的影响及其机制。结果表明，在干净的石英砂介质中，不同种类和粒径NPs的传输效率具有明显差异，不同种类NPs传输效率表现为ZnO> CeO2>Fe2O3；对于报告粒径在20～100 nm之间的CeO2 NPs，粒径的增加有助于其在多孔介质的传输。溶液离子强度的增大会降低Zn O NPs的传输，而NPs浓度的增大不利于其在饱和多孔介质的传输，传统的DLVO理论能够很好地解释NPs在无涂层饱和多孔介质中的传输。生物膜和土壤矿物均能抑制纳米颗粒在饱和多孔介质的传输，其主要通过对纳米颗粒的吸附和异质聚集作用影响纳米颗粒的传输，非DLVO相互作用以及介质涂层的表面特性对增强纳米颗粒沉积有很大贡献。     

土壤胶体在不同饱和度土壤介质中的释放与淋溶行为研究

采用饱和与非饱和填充土柱纵向淋溶研究方法,结合对流弥散模型方程（CDE）对穿透曲线的拟合计算,全面考察了土壤介质水饱和度、土壤水pH/离子强度、土壤孔隙水流速和土壤胶体颗粒大小对天然土壤胶体在实际土壤介质中释放、沉积迁移行为的影响。分别获取胶体扩散系数和阻滞因子值,定量说明实验中水化学、水动力学等条件的作用影响力。结果显示,介质不饱和条件不利于胶体的释放和淋溶;高pH和低离子强度条件对土壤胶体释放与迁移有利;淋溶过程的间断干扰,可以促使土壤胶体的增量淋溶释放;淋溶强度及胶体颗粒粒径大小,能够影响胶体穿透时间和穿透浓度峰值大小。     

砂质多孔介质中土壤颗粒的迁移

通过室内模拟试验,研究了不同土壤悬液浓度和不同多孔介质组成条件下土壤颗粒在砂质多孔介质中的截留和迁出特征,以揭示土壤颗粒在砂质多孔介质中的迁移特征。结果表明,土壤颗粒在砂质多孔介质中迁移时会受到土壤颗粒粒级、浓度和介质组成的影响。截留作用在土壤颗粒通过砂质多孔介质时起主导作用,土壤颗粒截留比例随着土壤颗粒浓度的增大逐渐增加;而随着多孔介质中粗砂比例的增大,其逐渐降低。土壤总颗粒、50μm和1~50μm土壤颗粒迁出量分别与该粒级相应投入量呈幂函数增加趋势,而1μm土壤颗粒的迁出量与其投入量呈线性增加趋势。土壤总颗粒迁出量与介质中粗砂比例之间存在线性增加关系。因此,多孔介质组成、颗粒粒径和浓度在土壤颗粒迁移过程中起着重要作用,在多孔介质中土壤颗粒和污染物迁移研究方面需要充分考虑这些因素。     

胶体颗粒对不同粒径饱和多孔介质渗透性的影响

探讨胶体颗粒在多孔介质中迁移所发生的物理、化学及生物作用过程,在许多学科中具有重要的科学意义。采用室内石英砂柱实验,开展了定水头条件下不同浓度和粒径的胶体颗粒在饱和多孔介质中的运移行为研究。共使用了3种胶体粒径、3种浓度的胶体溶液和3种粒径范围的石英砂。实验表明:多孔介质的相对渗透系数K/K0(K为各时刻计算所得的渗透系数,K0为初始渗透系数)减小程度与颗粒浓度成正比;胶体颗粒越大,越易在表层沉积,而小颗粒易向下部迁移,但总体来看粒径效应没有浓度效应明显;当胶体颗粒在不同粒径的饱和多孔介质中迁移时,粒径大的多孔介质各段K/K0均有明显降低,而粒径小的只在表层变化明显。不同条件下总体相对渗透系数与时间之间呈二次方相关关系,但当多孔介质粒径较小时,相关性不显著。介质渗流流速及砂柱不同位置胶体颗粒浓度变化与介质渗透性变化相对应。用扫描电镜(Scanning Electron Microscope,SEM)进行定性表征,进一步说明胶体颗粒会堵塞多孔介质孔隙影响其渗透性。实验中发现当输入浓度C0小于0.5 g·L–1且dp/Dp>0.018(dp为胶体颗粒粒径,Dp为石英砂算数平均粒径)时,会出现多孔介质局部K/K0增大的现象。     

孔隙空间对聚苯乙烯胶体滞留与释放的影响

为加深孔隙空间对胶体运移影响的认识,在不同pH与离子强度下,研究了胶体在经酸洗或水洗后的玻璃珠或石英砂中的迁移行为。结果表明:粒径相同的玻璃珠与石英砂(0.45~0.60mm)相比,形状一致的玻璃珠形成的孔隙空间(孔隙率0.38)小于石英砂(0.45)。酸洗与水洗后的玻璃珠表面成分变化不大(0~0.6%),经酸洗的介质后能提供更多有利吸附位点。在高pH(10)环境下,石英砂经酸洗或水洗后,胶体滞留量增大(72.1%和69.2%)。提高溶液pH到10后出现的胶体吸附增加,是颗粒接触点、非流动区或低流速区和涡流区滞留等孔隙空间滞留机制引起的,用DLVO理论无法解释。在离子强度为0.001mol/L或0.05mol/L环境下,酸洗石英砂中胶体滞留量比酸洗玻璃珠的分别高16.3%和28.0%,表明介质孔隙空间增大可加强颗粒接触点、非流动区或低流速区和涡流区滞留,然而优先流能够削弱孔隙空间滞留机制对胶体的滞留。此外,超纯水解吸时仅使少量胶体(3.9%)从玻璃珠与石英砂介质的孔隙涡流区中解吸出来,表明涡流区对胶体的保留不是胶体滞留在介质中的主要机制。     

畜禽粪便生物炭内源重金属在酸性土壤中的迁移转化

为探究生物炭内源重金属在酸性土壤中的迁移转化规律,科学指导畜禽粪便生物炭农田应用,该研究以猪粪生物炭为研究对象,开展土壤培养试验,利用扫描电镜、物理吸附、X射线衍射物相分析、X射线光电子能谱和电感耦合等离子体质谱等方法表征不同培养时间生物炭表面形貌、孔隙结构、元素分布的变化规律,以及土壤孔隙溶液中重金属、磷酸盐等组分的变化规律。结果显示生物炭内源重金属Cu、Zn主要存在形态为氧化提取态,Cu、Zn氧化提取态比例分别为79.37%和53.43%,生物炭矿物质元素主要以氧化物形式存在于生物炭颗粒表面,施入酸性土壤后,生物炭比表面积及孔容增加,颗粒表面Cu、P、K等元素含量降低,土壤孔隙溶液中pH值、EC、Cu与PO43-含量显著升高,PO43-的浓度范围为2.26～298.00 mg/L,Cu的浓度范围为1.81～2.86 μg/L,生物炭颗粒粒径越小,PO43-和Cu溶出率越高,生物炭施入土壤30 d时,土壤孔隙溶液中PO43-和Cu的浓度最高。研究表明酸性土壤可促进以碳酸盐、磷酸盐氧化物形式存在的Cu以及被碳酸根与磷酸根沉淀的Cu不断释放进入土壤,但生物炭内源Zn在酸性土壤环境不易释放,且生物炭可吸附土壤中的Zn,降低Zn的生物有效性。     

制炭条件对生物炭碱性基团含量及酸性土壤改良效果的影响

采用不同粒径(0.5,0.25~0.5,0.25mm)的4种原材料(椰糠、木薯秸秆、桉树枝、猪粪),通过不同热解温度(300,400,500,600℃)炭化不同时间(1,2,3,5h)制备生物炭,探讨制炭条件对生物炭碱性基团含量的影响,并探索生物炭改良酸性土壤pH的影响因素。结果表明,不同制炭条件所制备的生物炭均呈碱性,碱性基团含量范围为0.40~1.05mmol/g。不同原材料生物炭碱性基团含量呈现猪粪木薯秸秆椰糠桉树枝的规律。随着热解温度的升高、热解时间的延长及原材料粉碎粒度的减小,生物炭碱性基团含量呈增加趋势。研究还表明,添加生物炭能显著提高酸性土壤pH,其改良酸性土壤的能力随碱性基团含量的增加而增强。原材料粉碎粒度减小、热解温度升高和热解时间延长及用量增加,均能有效提升生物炭改良酸性土壤pH的效果。     

饱和多孔介质中高岭石胶体和SiO2胶体运移行为比较

胶体在多孔介质中的运移行为不仅取决于胶体本身的性质,同时还受到溶液离子强度、孔隙水流速等物理、化学因素的影响。本文通过室内饱和石英砂柱出流实验,探讨了高岭石胶体(Kaolinite胶体)和SiO2胶体在不同离子强度(0.001 5,0.01和0.03 mol L-1)和平均孔隙流速(约20和5 cm h-1)作用下的迁移行为。结果表明,随溶液离子强度增加,Kaolinite胶体和SiO2胶体的沉淀量增加;平均孔隙水流速的增加则会促进Kaolinite胶体和SiO2胶体的运移。同时还表明,离子强度和流速变化对粒径较大的Kaolinite胶体运移的影响要显著大于SiO2胶体。研究结果有助于加深胶体对污染物运移的促进机制的理解,同时对全面、客观评价地下环境的污染风险具有一定的指导意义。     

几种物理因素对四氧化三铁纳米颗粒在有机质存在条件下的饱和多孔介质中迁移持留行为的影响

近些年来,环境研究者对纳米颗粒的迁移性进行了部分研究,但是对环境稳定性低、反应活性高的金属氧化物工程纳米颗粒在多孔介质中的运移沉积行为的系统探讨还很不足,尤其是对其在有机质（NOM）存在条件下迁移行为的了解非常有限。本研究选用四氧化三铁磁纳米颗粒（MENPs）作为研究对象,采用填充柱淋溶实验法,对其在饱和多孔介质中的迁移持留行为展开探讨,其目的是考察几种主要介质环境物理因素对其在天然有机质存在条件下的纵向淋溶过程及其在介质中持留量的影响作用。结果显示,不利吸附条件下的MENPs集聚体在多孔介质中的吸附持留及迁移性能取决于多种合力的作用效果。其中,孔隙水流速增大时,MENPs在多孔介质中的迁移性增强,持留性减弱,持留MENPs在介质中的逐层分布随孔隙水流速改变而变化;而且,MENPs在多孔介质中的迁移持留性与介质颗粒的表面物理性质也有关,天然有机质的存在一定程度上可以改善石英砂表面的异质性。另外,介质颗粒粒径大小也是影响MENP-介质间持留机制的重要因子。当多孔介质颗粒粒径大小改变时,MENPs穿透曲线及持留分布曲线随之变化明显,MENPs的吸附沉积机制也相应有所不同。     

不同类型生物炭理化特性及其对土壤持水性的影响

[目的]对比分析不同原料制备的生物炭的理化性质及其对土壤持水性的影响,为选择合适的生物炭改良和修复土壤提供理论依据。[方法]以鸡粪、浒苔及稻草为原料,分高、中、低3种不同温度制备生物炭,运用元素分析、盆栽培养等试验研究其特性。[结果]稻草中C,H及灰分的含量较高,鸡粪中N含量较高,浒苔中C含量低,O含量较高;而在制备的生物炭中,鸡粪基生物炭C和N含量较高,浒苔基生物C含量却比较低。另外,3种类型生物炭的H/C摩尔比值随着热解温度的升高而逐渐降低,C/N比随着热解温度的升高而增大。不同原料制备的生物炭pH值随着热解温度的升高而增大,pH值从6.82~8.35升高至9.33~10.29;3种类型的生物炭pH值随着灰分含量的增大而增大,但增长速率不同,稻草基生物炭浒苔基生物炭鸡粪基生物炭。并且,随着热解温度的升高,鸡粪、浒苔及稻草基生物炭引起土壤持水性逐渐增强。[结论]在土壤提供营养成分方面,鸡粪基生物炭显然更具优势,而且在促进土壤持水性方面,鸡粪生物炭也相对更强一些。     

培养条件下生物炭对土壤锌的吸附作用

将稻壳分别在350℃和550℃热解温度下制备成生物质炭,按土壤质量的1%、3%和5%的添加量施入土壤中,保持一定的土壤含水率,探究施入生物炭的土壤对重金属锌吸附的影响。结果表明,土壤中施入生物炭之后,会提高土壤对重金属的吸附固定能力,生物炭的添加量越高,土壤对锌的最大吸附量越大。在试验开始阶段,随着生物炭的老化,土壤对锌的吸附性能会增强,同时土壤对锌的解吸率降低,随着时间的延长,生物炭与土壤发生的共腐殖化过程,导致土壤对锌的吸附性能逐渐降低,同时土壤对锌的解吸率提高。     

施加不同种类生物质炭及冻融交替后土壤吸附Cu(Ⅱ)的变化

以棉花和花生秸秆为原料于500℃下限氧慢速热解制备得到两种生物质炭,通过批处理恒温振荡法,探讨了土壤施加不同种类生物质炭及冻融交替后吸附Cu(Ⅱ)的变化。结果表明,Freundlich和Langmuir等温模型均能较好地拟合各处理土壤对Cu(Ⅱ)的吸附,土壤施加棉花和花生秸秆炭后对Cu(Ⅱ)的吸附能力显著提高,吸附能力分别提高了3.8和17.9倍;冻融交替后施加棉花和花生秸秆炭的土壤对Cu(Ⅱ)的吸附能力均降低,吸附能力分别下降了1.6和1.1倍;花生秸秆炭比棉花秸秆炭更适宜作为土壤改良剂修复重金属污染土壤。     

Effects of biochars derived from different feedstocks and pyrolysis temperatures on soil physical and hydraulic properties

Purpose

Biochar addition to soils potentially affects various soil properties, and these effects are dependent on biochars derived from different feedstock materials and pyrolysis processes. The objective of this study was to investigate the effects of amendment of different biochars on soil physical and hydraulic properties.

Materials and methods

Biochars were produced with dairy manure and woodchip at temperatures of 300, 500, and 700 °C, respectively. Each biochar was mixed at 5 % (w/w) with a forest soil, and the mixture was incubated for 180 days, during which soil physical and hydraulic properties were measured.

Results and discussion

Results showed that the biochar addition significantly enhanced the formation of soil macroaggregates at the early incubation time. The biochar application significantly reduced soil bulk density, increased the amount of soil organic matter, and stimulated microbial activity at the early incubation stage. Saturated hydraulic conductivities of the soil with biochars, especially produced at high pyrolysis temperature, were higher than those without biochars on the sampling days. The treatments with woodchip biochars resulted in higher saturated hydraulic conductivities than the dairy manure biochar treatments. Biochar applications improved water retention capacity, with stronger effects by biochars produced at higher pyrolysis temperatures. At the same suction, the soil with woodchip biochars possessed higher water content than that with the dairy manure biochars.

Conclusions

Biochar addition significantly affected the soil physical and hydraulic properties. The effects were different with biochars derived from different feedstock materials and pyrolysis temperatures.     

钢渣与生物质炭配合施用对红壤酸度的改良效果

采用厌氧热解方法制备污泥生物质炭和花生秸秆炭,研究了钢渣和生物质炭单独施用及配合施用对红壤酸度的改良效果,结果表明,钢渣、花生秸秆炭和污泥生物质炭均含有一定量的碱性物质,向红壤中添加钢渣和生物质炭可以中和土壤酸度,提高土壤pH,增加土壤交换性盐基阳离子含量,降低土壤交换性铝含量.90天培养实验结束时,这3种改良剂分别使土壤pH相对对照提高1.10、0.72和0.48.钢渣与花生秸秆炭配合施用对土壤酸度的改良效果最好,使土壤pH相对对照提高2.14,单施污泥生物质炭的改良效果最小.钢渣和生物质炭含一定量的养分元素,添加钢渣和生物质炭可以同时改善土壤肥力.钢渣含丰富的钙,添加钢渣使土壤交换性钙含量增幅最大,相对对照增加4.5倍;添加花生秸秆炭使土壤交换钾增加最显著,相对对照约增加7倍;污泥生物质炭含丰富的磷,添加污泥生物质炭使土壤有效磷增加最显著,相对对照增加5.4倍.添加钢渣和2种生物质炭均显著提高了土壤交换性镁含量,将钢渣与生物质炭配合施用,土壤交换性镁含量的增幅更大.由于钢渣和2种生物质炭的碱含量和养分含量各有特点,因此可以根据土壤酸度状况和养分含量选择将钢渣与不同生物质炭配合施用,以达到既能最大限度中和土壤酸度又能补充土壤所必需养分的目的.     

Designing relevant biochars as soil amendments using lignocellulosic-based and manure-based feedstocks

Purpose

Biochars are a by-product of the biofuel processing of lignocellulosic and manure feedstocks. Because biochars contain an assemblage of organic and inorganic compounds, they can be used as an amendment for C sequestration and soil quality improvement. However, not all biochars are viable soil amendments; this is because their physical and chemical properties vary due to feedstock elemental composition, biofuel processing, and particle size differences. Biochar could deliver a more effective service as a soil amendment if its chemistry was designed ex ante with characteristics that target specific soil quality issues. In this study, we demonstrate how biochars can be designed with relevant properties as successful soil amendments through feedstock selection, pyrolysis conditions, and particle size choices.

Materials and methods

Biochars were produced by pyrolysis of parent lignocellulosic feedstock sources—peanut hull (PH; Archis hypogaea), pecan shell (PS; Carya illinoensis), switchgrass (SG; Panicum virgatum), pine chips (PC; Pinus taeda), hardwood wastes (wood), and poultry litter manure (PL; Gallus domesticus), as well as blends of these feedstocks at temperatures ranging from 250 to 700 °C. Additionally, blended feedstocks were made into pellets (>2 mm) prior to pyrolysis at 350 °C. Dust-sized (<0.42 mm) biochar was obtained through grinding of pelletized biochars. After chemical characterization, the biochars were evaluated as fertility amendments in a Norfolk soil (fine-loamy, kaolinitic, thermic, Typic Kandiudult) during two different pot incubation experiments.

Results and discussion

PL biochars were alkaline and enriched in N and P, whereas biochar from lignocellulosic feedstocks exhibited mixed pH and nutrient contents. Blending PL with PC resulted in lower biochar pH values and nutrient contents. In pot experiment 1, most biochars significantly (P?<?0.05) raised soil pH, soil organic carbon, cation exchange capacity, and Mehlich 1 extractable P and K. PL biochar added at 20 g?kg^?1 resulted in excessive soil P concentrations (393 to 714 mg?kg^?1) and leachate enriched with dissolved phosphorus (DP, 22 to 70 mg?L^?1). In pot experiment 2, blended and pelletized PL with PC feedstock reduced soil pH and extractable soil P and K concentrations compared to pot experiment 1. Water leachate DP concentrations were significantly (P?<?0.05) reduced by pelletized biochar blends.

Conclusions

Short-term laboratory pot experiments revealed that biochars can have different impacts at modifying soil quality characteristics. Keying on these results allowed for creating designer biochars to address specific soil quality limitations. In the process of manufacturing designer biochars, first, it is important to know what soil quality characteristics are in need of change. Second, choices between feedstocks, blends of these feedstocks, and their accompanying particle sizes can be made prior to pyrolysis to create biochars tailored for addressing specific soil quality improvements. Utilization of these principles should allow for effective service of the designed biochar as a soil amendment while minimizing unwanted ex facto soil quality changes and environmental effects.     

Biochar-induced changes in soil properties affected immobilization/mobilization of metals/metalloids in contaminated soils

Purpose

Remediation of metal contaminated soil with biochar is attracting extensive interest in recent years. Understanding the significance of variable biochar properties and soil types helps elucidating the meticulous roles of biochar in immobilizing/mobilizing metals/metalloids in contaminated soils.

Materials and methods

Six biochars were produced from widely available agricultural wastes (i.e., soybean stover, peanut shells and pine needles) at two pyrolysis temperatures of 300 and 700 °C, respectively. The Pb-, Cu-, and Sb-contaminated shooting range soils and Pb-, Zn-, and As-contaminated agricultural soils were amended with the produced biochars. The mobility of metals/metalloids was assessed by the standard batch leaching test, principal component analysis and speciation modeling.

Results and discussion

The changes in soil properties were correlated to feedstock types and pyrolysis temperatures of biochars based on the principal component analysis. Biochars produced at 300 °C were more efficient in decreasing Pb and Cu mobility (>93 %) in alkaline shooting range soil via surface complexation with carboxyl groups and Fe-/Al-minerals of biochars as well as metal-phosphates precipitation. By contrast, biochars produced at 700 °C outperformed their counterparts in decreasing Pb and Zn mobility (100 %) in acidic agricultural soil by metal-hydroxides precipitation due to biochar-induced pH increase. However, Sb and As mobility in both soils was unfavorably increased by biochar amendment, possibly due to the enhanced electrostatic repulsion and competition with phosphate.

Conclusions

It is noteworthy that the application of biochars is not equally effective in immobilizing metals or mobilizing metalloids in different soils. We should apply biochar to multi-metal contaminated soil with great caution and tailor biochar production for achieving desired outcome and avoiding adverse impact on soil ecosystem.

     

不同地区油菜秸秆制备的生物质炭对酸性红壤的改良效果

从江西鹰潭、安徽宣城、江苏南京和淮阴等4个地区收集油菜秸秆,在500℃下厌氧热解制备生物质炭,比较生物质炭的pH、盐基离子和碳酸盐含量的差异,并在20 g/kg加入量下考察其对安徽宣城pH 4.1的酸性红壤改良效果。结果表明,江西鹰潭油菜秸秆炭pH、盐基离子和碳酸盐含量最低,安徽宣城油菜秸秆炭次之,江苏淮阴和南京油菜秸秆炭的相应参数值最高。当用这4种油菜秸秆炭改良土壤酸度时,改良效果表现为江苏淮阴>江苏南京>安徽宣城>江西鹰潭,与生物质炭pH、盐基离子和碳酸盐含量一致。因此,利用秸秆生物质炭改良土壤酸度时,不仅需要考虑炭化条件和秸秆类型,作物的产地差异也需要进行考量。     

生物炭主要类型、理化性质及其研究展望

【目的】 生物炭作为工农业生产副产品低碳利用的有效手段,其改善土壤及提高作物品质的有益功效已被逐步认识,但对其研究报道分散且差异较大。对已有研究进行梳理总结,可为生物炭生产施用以及形成有效的产业链提供科学依据。 主要进展 1）生物炭全碳含量在 30%～90% 之间,平均 64%。生物炭碳含量由大到小来源依次是木质、秸秆、壳类、粪污和污泥。秸秆类生物炭碳含量大多为 40%～80%,木质类生物炭在 60%～85%。生物炭灰分含量在 0～40% 之间变动,平均 15.52%。灰分含量由大到小依次是污泥、粪污、秸秆、壳类和木质。秸秆生物炭灰分含量主要在 20%～35% 之间,较少为 15%;木质炭灰分主要在 0～10% 范围内。生物炭碳含量和灰分含量相关系数为–0.77。裂解温度与生物炭碳灰组分呈正相关,相关系数分别为 0.17 和 0.28。施入生物炭可以改善土壤状况,生物炭灰分通常对养分贫瘠土壤及沙质土壤的一些养分补充作用较明显。2）生物炭比表面积绝大多数在 0～520 m2/g 之间,平均 124.83 m2/g,壳类、秸秆、木质、粪污和污泥生物炭比表面积逐渐降低。秸秆炭比表面积集中在 0～200 m2/g 以内,木质炭比表面积集中在 0～100 m2/g 以内。制备温度与比表面积的相关系数为 0.48。生物炭的孔隙结构能降低土壤容重、降低土壤密度,能较好地去除溶液和钝化土壤中的重金属。3）生物炭 pH 值范围在 5～12,平均为 9.15。秸秆、污泥、粪污、木质、壳类生物炭 pH 值中值逐渐降低。秸秆生物炭 pH 值多集中在 8～11 范围内,木质生物炭 pH 相对一致。生物炭的 CEC 从 0 到 500 cmol /kg 都有分布,平均为 71.91 cmol/kg。秸秆类生物炭 CEC 值大多集中在 0～100 cmol/kg 范围内,木质生物炭则在 5～10 与 15～25 cmol/kg 范围内均有一定数量的分布。裂解温度与 pH 值和 CEC 的相关系数为 0.58 和 0.30。生物炭施入土壤后可消耗土壤质子,提高酸性土壤 pH 值,提高酸性土壤一些养分的有效性;其巨大的表面积还可提高对阳离子的吸附,提高土壤保肥能力。4）生物炭的裂解温度大都集中在 200～800℃ 之间,偶有达到 1000℃ 的裂解温度。 建议和展望 目前,全世界范围内对生物炭的生产和使用还处于就近和来源方便的初级阶段,影响着生物炭功能和效益的最大化。应从以下几个方面加强研究和应用试验:首先,系统研究生物炭制造参数对理化性状的影响,研究不同原料生物炭的作用机理差异及其针对性,建立生物炭理化性质参数数据库;其次,加强应用研究,根据土壤理化性状和改良目标选择适宜的生物炭类型,根据对作物经济性状的要求,研究选择适宜的生物炭类型,实现生物炭功效的最大利用。加强不同原料的选配和组合研究,改良生物炭产品的目标性状,形成系列化产品。      

Phosphorus availability and grass growth in biochar-modified acid soil: A study excluding the effects of soil pH

The low efficiency of phosphorus fertilization in weathered soils can limit plant development. The application of biochars in these areas has been seen as an important way to increase the efficiency of phosphorus fertilization and to promote better plant growth. However, biochars are alkaline materials that can increase soil pH and thus change the nutrient dynamics, which has been often ignored in studies of this nature. Here, all treatments had their pH standardized at 6.1 to eliminate the influence of pH on biochar application responses. The main goal of this study was to evaluate the real potential of coffee straw and eucalyptus bark biochars, produced under different pyrolysis temperatures, in the optimization of phosphorus fertilization and the development of Brachiaria brizantha. A greenhouse experiment was set up in a 2 × 2 × 5 factorial scheme, conducted for 120 days. The biochars, prepared from coffee straw and eucalyptus bark at 350 and 600°C, were applied at five rates in a Red-Yellow Oxisol. The application of biochars may reduce the demand for nutrients and correctives, optimize phosphorus fertilization and improve the development of Brachiaria brizantha, but this ability depends on the raw material and the pyrolysis temperature used in its production. All analysed biochars can contribute to higher tillering and dry matter production, but only coffee straw biochars and eucalyptus bark biochar produced at 350°C were efficient in the optimization of phosphorus fertilization until 120 days of cultivation of Brachiaria brizantha.