Research Progress on Graphite Target Preparation for Accelerator Mass Spectrometry 14C Analysis
-
摘要: 加速器质谱(AMS)是进行14C同位素分析的主要技术手段,而高精度低本底加速器质谱14C分析主要受样品制备技术限制,因此探讨如何提高石墨制备的稳定性和控制碳污染降低本底将有助于产出高质量14C分析数据,突破14C测年上限(约5.0万年),进一步拓宽14C年代学和同位素示踪的应用范畴。本文详细阐述了催化还原法(H2/Fe法、Zn/Fe法和Zn-TiH2/Fe法)制备石墨样品的真空装置和主要工作原理,指出了微量样品石墨制备过程中同位素分馏、石墨产率、束流强度以及精密度与样品量之间存在严重的依赖关系及其抑制方法。着重探讨了石墨制备技术实验条件(还原剂、催化剂、温度等)的优化选择及其与石墨产率、同位素分馏、束流性能之间的内在联系,总结分析了碳污染来源并探寻合适的碳污染控制技术。目前的研究表明最佳实验条件为:H2/Fe法宜采用还原剂H2/CO2(体积比2~2.5),催化剂为源自氢还原单质铁粉(-325目球粒,Fe/C=2~5),温度500~550℃;Zn/Fe法宜采用还原剂Zn/C(质量比50~80),催化剂为源自氢还原单质铁粉(-325目球粒,Fe/C=2~5),Zn反应管温度400~450℃,Fe反应管温度500~550℃。碳污染来源于制备过程中的各个方面,除采用高温除碳的方式外还可采用适当的数学模型加以校正,但还需要更多详细的实验工作来加强现有认识,以期更好地消除碳污染对测试结果的影响。对测年目标组分不稳定的样品(如地下水中的溶解无机碳)应避免样品直接暴露于大气,以减少野外采样过程中现代大气CO2对测量结果的影响。要点
(1) 探讨了实验条件对石墨性能的影响,提出了石墨制备的最佳实验条件。
(2) 分析了碳污染来源,提出了低本底控制办法。
(3) 总结了微量样品制备技术的发展现状及其存在的问题。
HIGHLIGHTS(1) The effects of graphitization conditions on graphite performance were discussed and the optimum conditions were proposed.
(2) The carbon contamination source was analyzed, and the method of reducing background was advocated.
(3) The development of ultra-small sample preparation technology and its problems were reviewed.
Abstract:BACKGROUNDAccelerator mass spectrometry (AMS) is the most popular technique for radiocarbon analysis. However, yielding high precision and low background 14C data by AMS is hindered by sample preparation. Therefore, improving the stability of graphitization and reducing the carbon contamination in the background helps to produce high quality 14C data and break through the 14C dating upper limit (about 50000ya), further broadening the application range of 14C chronology and isotope tracer.OBJECTIVESTo provide basic reference for beginners or more experienced scientists who are going to set up a radiocarbon sample preparation vacuum line and methods.METHODSThe development of graphite preparation technology with respect to sample preparation vacuum line apparatus and the underlying principle of H2/Fe, Zn/Fe and Zn-TiH2/Fe methods were reviewed. The advantages and drawbacks of these methods were also discussed. Additionally, the optimization of experimental conditions from the perspective of reductant, catalyst and graphitization temperature, accompanied by the inner relationship with the graphite yield, isotope fractionation and beam performance were emphatically discussed. The sources of carbon contamination and suitable control technology were also argued.RESULTSThe optimized graphitization conditions by H2/Fe method was H2/CO2=2-2.5 (V/V), -325 meshes ion powder derived from hydrogen reduction with Fe/C=2-5 (m/m), and graphitization temperature of 500-550℃, while by Zn/Fe method it was Zn/C=50-80 (m/m), -325 meshes ion powder derived from hydrogen reduction with Fe/C=2-5 (m/m), and graphitization temperature of 400-450℃ for Zn reaction tube and 500-550℃ for Fe reaction tube. The carbon contamination originated from each step in the sample preparation procedure, which could be either reduced by high-temperature bake or calibrated by mathematical model, but it required more detailed study to strengthen our knowledge and eliminate the effects on results.CONCLUSIONSBoth of the sample preparation methods used and the optimum of graphitization conditions are critical for good performance of the graphite target and the final precision and accuracy of the measurement, especially for ultra-small size samples. However, these effects could be reduced or even eliminated by optimizing the experimental procedures and the graphitization conditions or subtracting by mathematical models. -
硒是人体必需的微量元素之一,影响着人体各项生理系统[1],硒的丰缺与人体健康程度密切相关。硒含量过高将引起人出现脱发等不良反应[2],而缺硒则易引发克山病、大骨节病等10余种疾病[3]。研究发现我国三分之一的地区为严重缺硒区,导致当地居民食物中硒的摄入量偏低[4]。农产品是居民食物的主要来源,通过摄入富硒作物是解决人体缺硒最有效的途径之一[5]。添加外源硒是目前常用的人工富硒方式,郭文慧等[6]对紫甘薯的研究表明,施硒能增加作物产量,同时能提高作物中硒的含量。适当喷施亚硒酸钠可提高稻谷产量及其硒含量[7]。但不同作物对硒的富集能力具有差异性,且不同类型土壤对外源硒的储存、释放能力也不同,因而通过添加外源硒来生产富硒农产品有一定弊端。
土壤中硒的生物有效性是影响作物富硒的关键因素之一,富硒土壤中能被作物吸收利用的有效硒不到总硒的5%。曹容浩[3]发现土壤有效硒主要受总硒、pH、有机质等因素影响,且土壤酸碱度是影响硒生物有效性的主要因素。我国南方地区土壤多以红壤为主,土壤中的硒大多以亚硒酸盐的形态存在,极易被铁铝氧化物吸附,导致土壤中生物有效态硒含量偏低[8],严重影响了富硒土壤资源的开发利用。基于此,有不少学者通过施加改良剂来提高土壤中硒的有效性,如施加秸秆生物质炭、钙镁磷肥等[9],谢邦廷等[8]在土壤中添加生石灰和燃煤炉渣后,提高了pH和有效硒含量。但长时间添加生石灰易引起土壤板结,不利于作物生长,燃煤炉渣中可能含有放射性元素[10],会对人体健康带来威胁;磷肥等肥料施入土壤后易引起水体富营养化,也会在一定程度上提高土壤中镉元素的含量[11]。因此,寻找安全有效的改良剂对提高富硒土壤中硒的有效性至关重要。
生物质炭是一种运用广泛的新兴土壤改良剂,含大量碳酸盐等碱性物质,能明显改善土壤酸碱度[12]。钢渣中含有CaO、MgO、SiO2等多种氧化物同时存在少量植物生长必须的微量元素,钢渣对农田土壤具有良好的改良效果,是一种潜在的多金属复合污染土壤改良剂。施加钢渣可有效提高土壤pH值和有效硅含量,并增加农作物产量[13]。如邓腾灏博等[14]研究表明土壤中施加钢渣后pH可从3.5提升到7.0,显著提高了酸性土壤的碱性,同时降低了土壤有效态重金属的含量及稻米中重金属的浓度。
丰城市境内存在大面积富硒土壤,平均硒含量为0.49mg/kg[15],属富硒地带(0.400~3.00mg/kg)[16]。但该地区土壤主要以红壤为主,铁、铝氧化物含量较高,土质透气透水性能差、土质黏重,极大限制了土壤中硒的有效性。目前,诸旭东等[17]通过添加钙镁磷肥、叶面喷硒等调控措施提高了该地区大米中的硒含量,但添加外源硒成本较高,不易大面积使用。本文以江西丰城富硒区土壤为研究对象,通过施加生物质炭、钢渣调控土壤理化性质,研究不同改良剂对土壤中硒生物有效性的影响,并探究不同类型生物质炭对土壤有效硒的调控是否具有相同效果,以期为富硒农产品的开发利用提供参考依据。
1. 实验部分
1.1 研究区域与样品采集
董家镇位于丰城市西北边陲,处丰城、高安两市交界处,气候类型为亚热带湿润气候,雨量充沛、四季分明,气候温和,该地区生态环境保护良好,素有“绿水青山”的美称。全镇有49平方多公里的富硒土壤资源,是“中国生态硒谷”核心区。
在前期调查的基础上,2018年7月,于董家镇泉南村富硒园地内,按梅花布点法采集园地表层土壤(0~20cm)各1kg左右,混合均匀后用四分法取2~3kg土壤为供试样品带回实验室。剔除植物根系、石块等杂物,置于阴凉处,自然风干过程中用木棒将土壤敲碎后,过10、20、60目筛、混匀、备用。供试土壤pH 4.24,总硒量为0.72mg/kg,有机质含量为3.28%,阳离子交换量(CEC)为4.2cmol/kg。
1.2 供试改良剂
1.2.1 生物质炭
从市场购买约3kg生物质炭粉末(江苏华丰农业生物工程有限公司),去除大块杂质,过60目筛备用,pH=10.5。生物质炭的施加量会影响其对土壤理化性质的改良效果,当施加量为10g/kg时,其对土壤理化性质的影响不太明显,基于此,本次试验设置3个不同梯度,即2g/kg、10g/kg、30g/kg(记为处理1~3)。试验时每个塑料烧杯中加入100g过10目筛的供试土壤,并分别添加0.2g、1.0g、3.0g生物质炭于烧杯后,用玻璃棒搅拌均匀。
1.2.2 钢渣
钢渣采自南昌市钢铁厂,采回的钢渣经研磨后过60目筛,混匀,备用,测得pH为9.2,总硒含量为0.42mg/kg。同时测定了钢渣中部分重金属含量Cr(131.2mg/kg)、As(22.7mg/kg)、Cd(0.18mg/kg)、Hg(1.20 mg/kg)和Pb(33.2mg/kg)几种重金属含量值均在《肥料中砷、镉、铅、铬、汞生态指标》(GB/T 23349—2009)的限定值内(Cr:500mg/kg、As:50mg/kg、Cd:10mg/kg、Hg:5mg/kg和Pb:200mg/kg),因此,本实验所选钢渣可适用于土壤中。土壤改良时钢渣用量一般低于10g/kg[14]。实验设置3个不同梯度的钢渣添加量,即1、5、15 g/kg(记为处理6~8)。实验时每个塑料烧杯中加入100 g过10目筛的供试土壤,同时分别加入0.1、0.5、1.5g钢渣至烧杯后,用玻璃棒充分搅拌均匀。
本实验以0.1g钢渣+2g生物质炭记为处理4,设一组空白对照,记为处理BK/5,每个处理重复3次。
1.3 土培试验
称取100g供试土壤于塑料烧杯中,添加改良剂并搅拌均匀后,用量筒量取约34mL纯水缓慢加入烧杯中,边加边搅拌,使供试土壤被均匀润湿,盖上塑料薄膜保湿。实验过程中观察土壤湿度,若发现土壤有变干的趋势及时加入适量纯水,每隔三天用称量法补充蒸发损失的水分,保证土壤润湿度,同时每隔7d搅拌一次土壤,并及时去除长出的杂草。土培实验持续时间为60d,于15、45和60d各取样一次。取出的土壤置于干燥通风处自然风干后研磨过20目和60目,装袋备用。
1.4 盆栽实验
试验于2018年9月15号在南昌大学环境楼楼顶进行。共设置7个处理和一个空白,试验用盆为聚乙烯材质(直径18cm,高19.5cm),每盆装土1kg。将小白菜种子在35℃催芽处理,小白菜种子发芽后的第二天将其移至土壤中种植,每盆定植5株,定期浇纯水,直至成熟。为防止试验过程中蔬菜营养匮乏,实验开始时每盆施加定量的有机肥作为底肥,每天定期浇水,保持土壤湿度,蔬菜生长中期追加底肥,蔬菜整个生长成熟期为45d,成熟后采摘蔬菜可食用部分,同时将收获小白菜后的土壤风干磨碎过筛待测其中的有效态硒。
1.5 土壤各项指标测试方法
土壤pH的测定参照标准NY/T 1377—2007《土壤的测定》:称取过20目筛的土壤样品10.0g于离心管中,按土液比1 : 2.5浸提,剧烈振荡5min后静置1~3h,测定土壤上清液pH,测定精度为0.01。
土壤有机质的测定参照标准HJ 615—2011《土壤有机碳的测定重铬酸钾氧化-分光光度法》:称取一定试样于100mL具塞消解管中,分别加入0.1g硫酸汞和5.0mL重铬酸钾溶液,再加入7.5mL硫酸,摇匀后置于135℃恒温加热器中开塞加热半小时,冷却定容。
阳离子交换量(CEC)的测定由江西索立德环保服务有限公司完成,分析方法参照LY/T 1243—1999《森林土壤阳离子交换量的测定》。
有效态硒的提取和测定:称取过20目筛土壤3.000g,用0.7mol/L磷酸二氢钾溶液浸提土壤有效态硒[18],提取的上清液经消化处理后用AFS-8230双通道原子荧光光度计测定硒含量[18-19]。
1.6 分析质量控制
样品分析时, 插入土壤标准物质(GBW07408)进行质控分析。经检查,样品重复率为100%,合格率为100%,分析精密度、报出率、检出限及相关参数均达到了《多目标区域地球化学调查规范(1 : 250000)》(DZ/T 0258—2014)的要求。分析结果满足本次研究所需。
2. 两种改良剂对硒有效性的影响及作用机理
2.1 不同处理对土壤硒有效性的影响
土壤中硒的生物有效性与其不同的赋存形态有关。由硒在土壤中不同形态的分布结果(表 1)可知,土壤中的硒主要以有机结合态和残渣态形式存在,水溶态和可交换态硒含量较少。添加改良剂后供试土壤中硒的形态分布比例有所不同,其中以水溶态和有机结合态硒的变化最显著。土壤中施加生物质炭后,水溶态硒的含量随时间推移逐渐减少,有机结合态硒含量则有所上升;添加钢渣后,水溶态和可交换态硒含量有所增加,有机结合态硒含量呈下降的趋势。铁锰氧化物结合态和残渣态在此次实验中基本没什么变化。由本实验结果可发现,当土壤环境变化时,有机结合态硒易转化为其他形态硒。
表 1 土壤中各形态硒含量Table 1. Content of different Se species in soil处理编号 水溶态硒(μg/kg) 可交换态硒(μg/kg) 铁锰氧化物结合态硒(μg/kg) 有机结合态硒(μg/kg) 残渣态硒(μg/kg) 15d 45d 60d 15d 45d 60d 15d 45d 60d 15d 45d 60d 15d 45d 60d 1 10.52 9.78 8.61 10.76 10.07 9.33 64.88 65.52 66.01 302.64 305.16 309.78 331.20 329.47 326.47 2 10.46 9.64 8.46 10.98 9.69 9.01 64.62 65.72 65.72 303.62 307.20 310.98 330.32 327.75 326.03 3 9.70 8.80 8.02 9.40 9.16 8.62 64.30 65.26 66.98 305.84 311.98 314.64 330.76 324.80 321.94 4 10.42 8.43 7.11 10.49 7.74 8.16 65.27 64.89 64.26 311.06 319.85 315.84 322.76 319.10 324.64 5 10.05 10.09 10.54 10.21 9.54 9.12 64.02 65.17 66.73 312.58 308.76 306.22 323.15 326.43 327.69 6 10.72 11.52 12.01 9.81 10.58 10.03 68.96 67.82 67.02 308.50 304.22 302.32 322.01 325.86 325.67 7 12.06 15.46 17.78 10.63 11.39 12.55 75.40 74.72 74.16 309.20 305.74 301.76 322.70 322.67 326.75 8 15.16 19.04 23.64 12.82 15.40 17.34 75.48 74.56 74.68 307.00 302.30 295.08 327.53 328.68 329.26 土壤中有效硒含量的高低可以反映植物对硒的吸收富集水平,是决定植物中硒含量的主要因素。本实验中,不同处理下土壤有效硒含量呈现不同的变化趋势(图 1)。土壤中施加生物质炭后,有效硒含量随培养时间的推移呈逐渐下降的趋势,且当生物质炭添加量增大时,有效硒含量的下降幅度也越大。土培实验结束后,处理1~4中土壤有效硒含量降幅分别为8.4%、10.8%、15.1%和23.6%(图 1a)。而谢珊妮等[9]用秸秆生物质炭改良强酸性高硒茶园土壤有效硒时发现,土壤中施加秸秆生物质炭,60d后土壤有效硒提升的幅度大于土培至30d土壤有效硒含量提高的幅度,与本文得出的结论不一致。这可能与秸秆生物质炭的原料、制备条件、添加量及土壤本身的性质有关。制备生物质炭的原料和条件不同时,其孔隙结构、比表面积、pH等理化性质也将表现出显著的差异[20]。赵世翔等[21]研究发现制备生物质炭的温度从300℃升高至600℃时,其比表面积可由2.35m2/g增大到107.76m2/g,当制备温度由500℃增至600℃时,生物质炭的比表面积增幅可达到942.17%。生物质炭表面碱性官能团的含量随制备温度的升高而增大[22]。本试验所用生物质炭pH为10.5,制备温度为550℃,而谢珊妮等[9]所用秸秆生物质炭pH为7.87。本研究土培实验结束后,空白组与添加3g/kg生物质炭实验组中土壤富里酸含量分别为4.43g/kg和7.08g/kg,胡敏酸含量分别为6.21g/kg和11.32g/kg。富里酸能提高土壤中硒的有效性,而胡敏酸则会降低土壤有效硒含量[23]。因此,本实验使用的生物质炭对硒主要表现为固定吸附性。
土壤中添加钢渣后,有效硒含量有不同程度的提升,且有效硒含量随土培时间的推移有逐渐上升的趋势。土培实验结束时,处理7和8中有效硒含量分别为27.41μg/kg、38.98μg/kg,与对照组(19.36μg/kg)相比(图 1b),有效硒含量是对照组的1.4倍和2.0倍。
实验发现,处理4中有效硒含量降得最多。由土壤中各形态含量结果表明,添加钢渣后可在一定程度上提高土壤中水溶态硒的含量,但因生物质炭具有较强的吸附固定作用,导致处理4土壤中的有效硒含量下降较快。
2.2 不同处理影响土壤中硒有效性的机理
2.2.1 改良剂对土壤pH的影响
本实验的供试土壤为酸性土,经生物质炭调控处理后,pH值均有所上升,且随生物质炭添加量的增加而增大(图 2a)。土培实验进行至60d时,添加生物质炭使土壤pH提升了0.1~0.61个单位不等。生物质炭是目前运用最广的一种土壤改良剂,其表面含有大量羟基、酚羟基等含氧官能团,这些官能团与H+发生络合反应,达到中和土壤酸度的目的[24],另一方面生物质炭中丰富的钾、钠盐基离子通过吸持作用降低了土壤中交换性H+、Al3+的水平[25]。
添加钢渣后,土壤pH也呈上升趋势(图 2b),pH上升程度与钢渣的添加量成正比。土培实验结束时,与对照组相比,土壤pH提升幅度为0.38~3.79个单位。相比于生物质炭,钢渣对土壤pH的改良效果更显著。钢渣中Ca、Mg、Si等多种氧化物经水解后释放出的OH-中和了土壤中的H+,同时含硅物质会抑制Al3+的活性[26]。由图 2b中可以看出,当钢渣施用量超过0.5%时,将大幅度改善土壤pH。
pH是影响土壤理化性质最重要的参数之一。pH通过改变土壤表面电荷进而影响土壤对硒的吸附能力[9],pH升高时,土壤表面的OH-也有所增加,释放出的OH-会竞争土壤表面的吸附位点,降低铁铝氧化物对硒的吸附能力[27],从而提高有效硒含量。实验结果表明,两种改良剂均能提高土壤pH。由添加生物质炭和钢渣后土壤pH随时间的动态变化(图 2)可以看出,土壤pH随土培时间呈下降的趋势。培养结束时,以空白对照组为例,pH由初始4.24降为4.07,下降了0.17个单位。这主要是因为表层耕地土壤中有一定量的铵态氮残留,土培过程中因铵态氮逐渐发生硝化反应释放出的质子导致pH下降[28]。图 3结果显示,土培实验结束后空白组与添加改良剂的土壤中铵态氮含量低于硝态氮,土培过程中土壤的硝化反应导致了pH下降。
2.2.2 改良剂对土壤有机质和CEC的影响
土壤有效硒受土壤总硒、pH和Eh、化学矿物组成、有机质、阳离子交换量、土壤黏粒、土壤中离子竞争等因素的影响。本研究中,改良剂施入土壤后有机质含量变化(表 2)显示,添加少量生物质炭对土壤有机质的影响并不明显,当添加量较大时,土壤有机质含量有所上升,且有机质含量随生物质炭施加量的增加明显增大。而钢渣对土壤有机质的影响并不显著。在改善土壤有机质方面,生物质炭中含有较高的碳,其自身缓慢的分解有利于土壤腐植质的形成[29],从而可显著提高土壤有机质含量。因钢渣自身存在的特性,钢渣施加进土壤后,对土壤有机质基本无显著影响。
表 2 不同处理对土壤性质的影响Table 2. Effects of different treatments on soil properties处理方法 有机质含量(%) CEC(mol/kg) 15d 45d 60d 15d 45d 60d 生物质炭0.2% 3.21 3.11 2.63 4.0 3.9 3.7 生物质炭1.0% 3.38 3.22 2.77 4.2 4.2 4.3 生物质炭3.0% 5.52 4.81 4.54 4.8 4.5 4.3 生物质炭2%+钢渣0.1% 3.30 3.12 2.66 4.4 4.2 4.3 空白对照组(BK) 3.28 2.80 2.66 4.2 4.1 4.0 钢渣0.1% 3.23 3.00 2.80 4.0 4.2 3.9 钢渣0.5% 3.09 2.82 2.79 6.7 6.8 6.2 钢渣1.5% 2.90 2.86 2.79 9.8 9.0 8.8 有机质对土壤中硒的吸附作用由有机质的组分和量所决定,并对硒的影响表现出双重性:一方面与有机质结合的硒经矿化作用可转变为亚硒酸等可溶性硒释放到土壤中[30],提升土壤中可溶性硒的含量,另一方面有机质具有较强的固定性,会降低土壤有效硒含量[2]。研究表明有机质对硒的影响主要表现为固定作用[31]。
土壤CEC是土壤主要理化性质之一,不同土壤中CEC含量也不同,其主要受pH、土壤质地和有机质含量的影响[3]。本实验中添加少量生物质炭、钢渣对土壤CEC的影响都较小,但随两种改良剂添加量的增大,土壤CEC也随之增大,且钢渣的影响效果明显高于生物质炭(表 2)。王文艳等[32]发现pH对CEC的贡献最为显著,且土壤pH与CEC具有显著的正相关关系。因此,钢渣在提高土壤pH时,也将明显增加CEC的含量。CEC含量越高时,土壤表面所含的负电荷量也越多,对硒的吸附量则会降低,有利于提高土壤有效硒的含量。
为明确土壤理化性质与有效硒之间的关系,本文对两者进行了相关性分析。结果表明,有效硒含量与pH、CEC呈显著正相关,相关系数分别为0.787和0.780(p < 0.01),与有机质呈负相关,相关系数为0.382(p < 0.05)。
3. 两种改良剂提高土壤有效硒的效果评价
不同处理下,土壤有效硒含量在土培试验过程中表现出一定的差异性(图 4)。土培结束后,8个处理中,除处理7、8外,其他处理对土壤有效硒的影响较为相近,均呈下降的趋势。添加生物质炭可在一定程度上提高土壤pH,但本实验所用生物质炭的孔隙度和比表面积较大,且生物质炭施入土壤后会提高土壤中富里酸的含量。因此,随生物质炭添加量的增加,土壤中有效硒含量降得也越快。钢渣能有效改善土壤酸碱度,有助于硒元素的活化,并提高土壤中硒的有效性。实验结果显示,当钢渣添加量为0.5%和1.5%时,土壤pH值分别为5.82和7.88,而大部分植物生长的最适pH在5.0~7.0之间。本实验的两种调控材料,生物质炭主要表现为固定性,不适合用来改善研究区土壤中硒的有效性,钢渣作为调控材料,能显著提高研究区土壤有效硒含量,但应根据植物生长条件来确定钢渣的添加量。本文建议钢渣使用量不应超过1.5%。
4. 盆栽小白菜富硒试验
蔬菜是人类生存所必需的食物,不同蔬菜品种对硒的吸收性能也不同。十字花科植物对硒有较强的富集能力,而小白菜是常见的十字花科蔬菜,是人体补硒的理想硒源,且其生长周期短、适于四季栽种,有利于大规模生产。本文盆栽实验以小白菜为试验蔬菜,研究两种改良剂不同添加量对小白菜富硒的影响效果。
土壤有效态硒的含量是影响植物中硒含量的主要因素,且土壤中化学有效态硒含量的增加可直接影响硒的生物有效性[9]。盆栽试验结果(图 5)显示,与对照组相比,处理7和8中小白菜硒含量增幅分别为30.0%和58.8%,处理1、处理2和处理6中虽均未提高小白菜硒含量,但种植出的小白菜基本仍属于富硒蔬菜(富硒蔬菜的硒含量≥0.01mg/kg),而处理3和处理4中的小白菜硒含量都低于0.01mg/kg。本实验中,碱性改良剂钢渣通过提高土壤硒的有效性,进而提高了小白菜中硒的含量,可使当地的硒资源得到充分利用,为进一步开发富硒蔬菜提供了依据。
5. 结论
利用改良剂调控富硒土壤中硒生物有效性的土培模拟实验结果表明,施加生物质炭和钢渣均能提高酸性土壤pH和CEC含量,并能在一定程度上提升硒的有效性,但施加生物质炭后土壤中有机质含量显著增加,且有机质对硒表现为固定作用,导致土壤有效硒含量总体偏低,而钢渣对pH和CEC的影响效果更明显,并能显著活化硒的有效性。因此,钢渣较生物质炭更适合作为该地区土壤硒有效性的调控材料。根据蔬菜生长的pH环境,本研究建议钢渣的使用量不要超过1.5%。
土壤自身具有吸附-解吸作用,并含有多种还原性微生物,能将土壤中有效硒含量维持在一定的水平。土壤中添加钢渣后可将有效硒含量提升至一定程度,同时促进作物对硒的吸收利用,有利于富硒农产品的生产。但改良剂对土壤有效硒活化的机理及其变化规律十分复杂,今后还需进一步研究。
-
图 2 各制样方法真空系统图
(a)14C石墨制靶CO2纯化真空系统;(b)H2/Fe法石墨化单元;(c)在线Zn/Fe法石墨化单元;(d)Zn+TiH2/Fe或Zn/Fe火焰封管法石墨化单元;(e)Zn/Fe隔膜封管法石墨化单元。PT为压力传感器。
Figure 2. Schematic diagrams of vacuum line for different graphite preparation methods: (a) The CO2 purification vacuum system; (b) Graphitization unit by H2/Fe method; (c) Graphitization unit by online Zn/Fe method; (d) Graphitization unit by Zn+TiH2/Fe or Zn/Fe flame-sealed method; (e) Graphitization unit by Zn/Fe septa-sealed method. PT denotes pressure transducer
表 1 石墨化条件及流程本底
Table 1 Summary of different graphitization conditions applied in prior studies and their corresponding procedure background
还原剂 催化剂 反应温度 反应时间(h) 样品量(mg) 本底14C年龄(ka) 参考文献 Zn:9.8~11.4mg
TiH2:3.3~4.9mg铁粉4~5mg 马弗炉
500~550℃7 0.1 41.1~48.1 [11] Zn:2.5mg 375目铁粉,
0.4mg/mg或1mg/mg C720℃ 10 1~2 41.1~44.4 [12] Zn:100mg 铁粉5mg 500℃ 5 0.5~1.0 44.4 [13] Zn:2.5mg/25μgC 铁粉2.5mg 电热板450℃ 12 0.025~0.25 27.9±0.26 [14] Zn:15mg 铁粉,2.5mg/mg C 550℃ 10 1 51.2~49.9 [15] H2/C=2 铁粉,2mg/mg C 550℃ 2~3 1 45.7 [16] Zn:9.8~11.4mg -400目铁粉4~5mg 450℃ 7 0.015 34.8 [17] H2/C=2.2 325目铁粉,2mg/mg C 600℃ 4~5 1 40.0~47.5 [18] H2/C=2.5 10μm铁粉,3mg/mg C 600℃ 3~4 0.3 45.2~55.5 [19] Zn:35~40mg
TiH2:7~10mg铁粉2mg 马弗炉
550~560℃8 0.5~1.0 53.0±4.6 [20] Zn:30~35mg
TiH2:10~15mg350目铁粉,
3~5mg/mg C马弗炉
500~550℃7 1 50 [8] H2/C=2.2 160目铁粉,2~3mg/mg C 600℃ 2~3 1 52 [21] Zn:200mg 铁粉,2mg/mg C Zn:420℃
Fe:620~630℃18~20 0.03~1 46.1~51.2 [7] H2/C=2.2~5 325目铁粉 670℃ 2~4 0.015~1 50~60 [22] H2/C=2.5~3 325目铁粉,1mg/mg C 600℃ 4 0.2 46.7±1.5 [23] H2/C=2.4 200目铁粉,2mg/mg C 500℃ 5~6 / 47.3±0.7 [24] 注:部分文献中并没有直接给出14C年龄,而是给出了现代碳污染量和死碳污染量的数据。为了统一和便于读者比较,此表中的部分14C年龄是经过文献中的公式进行换算而来的。14C年龄=-8033×ln(Fm),Fm=Mdc/(Ms+Mmc+Mdc)×Rmc,Ms代表典型样品量,Mmc代表现代碳污染量,Mdc代表死碳污染量,Rmc代表现代碳14C浓度。 表 2 不同石墨合成方法中可能发生的化学反应
Table 2 Potential chemical reactions during the graphitization process by H2/Fe and Zn/Fe or Zn-TiH2/Fe method
序号 化学反应方程 1 CO2(g)+H2(g)→CO(g)+H2O(g) 2 CO2(g)+Zn(s)→CO(g)+ZnO(s) 3 2CO(g)→Cgraphite(s)+CO2(g) 4 CO(g)+H2(g)→Cgraphite(s)+H2O(g) 5 CO2(g)+2H2(g)→Cgraphite(s)+2H2O(g) 6 2CO(g)+2H2(g)→CH4(g)+CO2(g) 7 CO(g)+3H2(g)→CH4(g)+H2O(g) 8 Cgraphite(s)+2H2(g)→CH4(g) 9 CO(g)+H2O(g)→CO2(g)+H2(g) 10 Zn(s)+H2O(g)→ZnO(s)+H2(g) 表 3 碳污染来源
Table 3 Sources of carbon contamination
碳污染来源 污染量 参考文献 样品预处理阶段 7.05±4.02μg现代碳 [45] 样品预处理阶段 0.7±0.3μg现代碳 [43] 燃烧阶段 3.01±2.0μg现代碳 [45] 燃烧阶段 1.5±0.1μg现代碳 [43] 燃烧阶段 0.36±0.07μg现代碳(玻璃管路吸附) [47] 燃烧阶段 每500mg CuO引入0.44±0.13μg现代碳 [47] 燃烧阶段 每支玻璃管引入0.02~0.15μg现代碳 [26] 燃烧阶段 每100mg CuO引入0.1±0.01μg现代碳 [26] 石墨化阶段 0.36±0.19μg现代碳 [43] 石墨化阶段 每10mg铁粉引入1.8±0.7μg现代碳 [26] 储存阶段 < 0.2μg现代碳 [43] 转移压靶阶段 < 0.1μg现代碳 [43] 仪器本底 ≤0.5μg现代碳 [45] -
Libby W F, Anderson E C, Arnold J R.Age determination by radiocarbon content:World-wide assay of natural radiocarbon[J]. Science, 1949, 109(2827):227-228. doi: 10.1126/science.109.2827.227
Hellborg R, Skog G.Accelerator mass spectrometry[J]. Mass Spectrometry Reviews, 2008, 27(5):398-427. doi: 10.1002/mas.20172
管永精, 王慧娟, 鞠志萍, 等.加速器质谱技术及其在地球科学中的应用[J].岩矿测试, 2005, 24(4):41-47. http://www.ykcs.ac.cn/article/id/ykcs_20050492 Guan Y J, Wang H J, Ju Z P, et al.Acclerator mass spectrometry and its applications in geosciences[J]. Rock and Mineral Analysis, 2005, 24(4):41-47. http://www.ykcs.ac.cn/article/id/ykcs_20050492
Kutschera W.Applications of accelerator mass spec-trometry[J]. International Journal of Mass Spectrometry, 2013, 349-350(1):203-218.
Vogel J S, Southon J R, Nelson D E, et al.Performance of catalytically condensed carbon for use in accelerator mass spectrometry[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 1984, 5(2):289-293. doi: 10.1016/0168-583X(84)90529-9
Slota P, Jull A T, Linick T, et al.Preparation of small samples for 14C accelerator targets by catalytic reduction of CO[J]. Radiocarbon, 1987, 29(2):303-306. doi: 10.1017/S0033822200056988
Ertunc T, Xu S, Bryant C L, et al.Progress in AMS target production of sub-milligram samples at the NERC radiocarbon laboratory[J]. Radiocarbon, 2005, 47(3):453-464. doi: 10.1017/S0033822200035232
Xu X, Trumbore S E, Zheng S, et al.Modifying a sealed tube zinc reduction method for preparation of AMS graphite targets:Reducing background and attaining high precision[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2007, 259(1):320-329. doi: 10.1016/j.nimb.2007.01.175
Polach H A.Radiocarbon targets for AMS:A review of perceptions, aims and achievements[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 1984, 5(2):259-264. doi: 10.1016/0168-583X(84)90523-8
Vogel J S, Nowikow I G, Southon J R, et al.Survey of simple carbon compounds for use in a negative ion sputter source[J]. Radiocarbon, 1983, 25(2):775-784. doi: 10.1017/S0033822200006135
Ding P, Shen C D, Yi W X, et al.Small-mass graphite preparation for AMS 14C measurements performed at GIGCAS, China[J]. Radiocarbon, 2017, 59(3):705-711. doi: 10.1017/RDC.2017.38
庞义俊, 何明, 杨旭冉, 等.基于小型单极加速器质谱测量14C的样品制备技术研究[J].原子能科学技术, 2017, 51(10):1866-1873. doi: 10.7538/yzk.2017.youxian.0012 Pang Y J, He M, Yang X R, et al.14C sample preparation for compact single stage AMS[J]. Atomic Energy Science and Technology, 2017, 51(10):1866-1873. doi: 10.7538/yzk.2017.youxian.0012
Zoppi U, Crye J, Song Q, et al.Performance evaluation of the New AMS system at Accium BioSciences[J]. Radiocarbon, 2016, 49(1):171-180. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=RDC49_01-JATSRDCRDC49_01S0033822200041990h.xml
Rinyu L, Orsovszki G, Futó I, et al.Application of zinc sealed tube graphitization on sub-milligram samples using EnvironMICADAS[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2015, 361(1):406-413. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=26e4df013f0f2542a4b3ea703f423acf
Orsovszki G, Rinyu L.Flame-sealed tube graphitization using zinc as the sole reduction agent:Precision improvement of EnvironMICADAS 14C measurements on graphite targets[J]. Radiocarbon, 2015, 57(5):979-990. doi: 10.2458/azu_rc.57.18193
杨雪, 郑勇刚, 尹金辉, 等.加速器14C制靶系统的研制及性能检验[J].地震地质, 2013, 35(4):930-934. doi: 10.3969/j.issn.0253-4967.2013.04.021 Yang X, Zheng Y G, Yin J H, et al.Developments and performance tests of the new AMS graphite target line[J]. Seismology and Geology, 2013, 35(4):930-934. doi: 10.3969/j.issn.0253-4967.2013.04.021
Xu X, Gao P, Salamanca E G.Ultra small-mass graphi-tization by sealed tube zinc reduction method for AMS 14C measurements[J]. Radiocarbon, 2013, 55(2-3):608-616. http://journals.cambridge.org/article_S0033822200057751
Piotrowska N.Status report of AMS sample preparation laboratory at GADAM Centre, Gliwice, Poland[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2013, 294:176-181. doi: 10.1016/j.nimb.2012.05.017
Delqué-Količ E, Comby-Zerbino C, Ferkane S, et al.Preparing and measuring ultra-small radiocarbon samples with the ARTEMIS AMS facility in Saclay, France[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2013, 294(1):189-193. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=050c90b1efb20dac57b3afd0f9d2d3a7
Marzaioli F, Borriello G, Passariello I, et al.Zinc redu-ction as an alternative method for AMS radiocarbon dating:Process optimization at CIRCE[J]. Radiocarbon, 2008, 50(1):139-149. doi: 10.1017/S0033822200043423
Zhou W, Lu X, Wu Z, et al.New results on Xi'an-AMS and sample preparation systems at Xi'an-AMS center[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2007, 262(1):135-142. doi: 10.1016/j.nimb.2007.04.221
Uchida M, Shibata Y, Yoneda M, et al.Technical pro-gress in AMS microscale radiocarbon analysis[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2004, 223-224(1):313-317. http://onlinelibrary.wiley.com/resolve/reference/ADS?id=2004NIMPB.223..313U
Hua Q, Zoppi U, Williams A A, et al.Small-mass AMS radiocarbon analysis at ANTARES[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2004, 223-224(1):284-292. http://d.old.wanfangdata.com.cn/NSTLQK/NSTL_QKJJ0212720154/
D'elia M, Calcagnile L, Quarta G, et al.Sample pre-paration and blank values at the AMS radiocarbon facility of the University of Lecce[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2004, 223-224(1):278-283. http://www.sciencedirect.com/science/article/pii/S0168583X04005816
Kitagawa H, Masazawa T, Nakamura T, et al.A batch pre-paration method for graphite targets with low background for AMS 14C measurements[J]. Radiocarbon, 1993, 35(2):295-300. doi: 10.1017/S0033822200064973
Verkouteren R M.Iron-manganese system for prepara-tion of radiocarbon AMS targets:Characterization of procedural chemical-isotopic blanks and fractionation[J]. Radiocarbon, 1997, 39(3):269-283. doi: 10.1017/S003382220005325X
Vogel J S.Rapid production of graphite without conta-mination for biomedical AMS[J]. Radiocarbon, 1992, 34(3):344-350. doi: 10.1017/S0033822200063529
Kim S H, Kelly P B, Clifford A J.Biological/biomedical accelerator mass spectrometry targets.1.Optimizing the CO2 reduction step using zinc dust[J]. Analytical Chemistry, 2008, 80(20):7651-7660. doi: 10.1021/ac801226g
刘圣华, 杨育振, 徐胜, 等.加速器质谱14C制样真空系统及石墨制备方法研究[J].岩矿测试, 2019, 38(3):270-279. doi: 10.15898/j.cnki.11-2131/td.201807120084 Liu S H, Yang Y Z, Xu S, et al.14C sample preparation vacuum line and graphite preparation method for 14C-AMS measurement[J]. Rock and Mineral Analysis, 2019, 38(3):270-279. doi: 10.15898/j.cnki.11-2131/td.201807120084
McNichol A P, Gagnon A R, Jones G A, et al.Illumina-tion of a black box:Analysis of gas composition during graphite target preparation[J]. Radiocarbon, 1992, 34(3):321-329. doi: 10.1017/S0033822200063499
Rinyu L, Futó I, Kiss A Z, et al.Performance test of a new graphite target production facility in ATOMKI[J]. Radiocarbon, 2007, 49(2):217-224. doi: 10.1017/S0033822200042144
Hong W, Park J H, Kim K J, et al.Establishment of chemical preparation methods and development of an automated reduction system for AMS sample preparation at KIGAM[J]. Radiocarbon, 2010, 52(3):1277-1287. doi: 10.1017/S0033822200046361
Macario K D, Alves E Q, Oliveira F M, et al.Graphiti-zation reaction via zinc reduction:How low can you go?[J]. International Journal of Mass Spectrometry, 2016, 410(1):47-51.
Macario K D, Oliveira F M, Moreira V N, et al.Optimi-zation of the amount of zinc in the graphitization reaction for radiocarbon AMS measurements at LAC-UFF[J]. Radiocarbon, 2016, 59(3):1-7.
Rinyu L, Molnár M, Major I, et al.Optimization of sealed tube graphitization method for environmental C-14 studies using MICADAS[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2013, 294(1):270-275. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=fcad5316421d17da51660cce423bf050
Khosh M S, Xu X, Trumbore S E.Small-mass graphite preparation by sealed tube zinc reduction method for AMS 14C measurements[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2010, 268(7-8):927-930. doi: 10.1016/j.nimb.2009.10.066
Wild E, Golser R, Hille P, et al.First 14C results from archaeological and forensic studies at the Vienna Environmental Research Accelerator[J]. Radiocarbon, 1998, 40(1):273-282. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=RDC40_01-JATSRDCRDC40_01S0033822200018142h.xml
Vogel J S, Southon J R, Nelson D E.Catalyst and binder effects in the use of filamentous graphite for AMS[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 1987, 29(1):50-56. http://www.sciencedirect.com/science/article/pii/0168583X87902023
Dee M, Bronk Ramsey C.Refinement of graphite target production at ORAU[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2000, 172(1-4):449-453. doi: 10.1016/S0168-583X(00)00337-2
Kim S H, Kelly P B, Clifford A J.Biological/biomedical accelerator mass spectrometry targets.2.Physical, morphological, and structural characteristics[J]. Analytical Chemistry, 2008, 80(20):7661-7669. doi: 10.1021/ac801228t
Kim S H, Kelly P B, Ortalan V, et al.Quality of graphite target for biological/biomedical/environmental applications of 14C-accelerator mass spectrometry[J]. Analytical Chemistry, 2010, 82(6):2243-2252. doi: 10.1021/ac9020769
Santos G M, Southon J R, Griffin S, et al.Ultra small-mass AMS 14C sample preparation and analyses at KCCAMS/UCI Facility[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2007, 259(1):293-302. doi: 10.1016/j.nimb.2007.01.172
Vogel J S, Nelson D, Southon J R.14C background levels in an accelerator mass spectrometry system[J]. Radiocarbon, 1987, 29(3):323-333. doi: 10.1017/S0033822200043733
Aerts-Bijma A T, Meijer H A J, Plicht J V D.AMS sample handling in Groningen[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 1997, 123(1-4):221-225. doi: 10.1016/S0168-583X(96)00672-6
Gillespie R, Hedges R E M.Laboratory contamination in radiocarbon accelerator mass spectrometry[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 1984, 5(2):294-296. doi: 10.1016/0168-583X(84)90530-5
Steinhof A, Altenburg M, Machts H.Sample preparation at the Jena 14C Laboratory[J]. Radiocarbon, 2017, 59(3):815-830. doi: 10.1017/RDC.2017.50
Verkouteren R M, Klouda G A, Currie L A, et al.Pre-paration of microgram samples on iron wool for radiocarbon analysis via accelerator mass spectrometry:A closed-system approach[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 1987, 29(1-2):41-44. doi: 10.1016/0168-583X(87)90200-X
Ertunc T, Xu S, Bryant C L, et al.Investigation into background levels of small organic samples at the NERC Radiocarbon Laboratory[J]. Radiocarbon, 2007, 49(2):271-280. doi: 10.1017/S0033822200042193
Yokoyama Y, Miyairi Y, Matsuzaki H, et al.Relation be-tween acid dissolution time in the vacuum test tube and time required for graphitization for AMS target preparation[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2007, 259(1):330-334. doi: 10.1016/j.nimb.2007.01.176
Paul D, Been H A, Aerts-Bijma A T, et al.Conta-mination on AMS sample targets by modern carbon is inevitable[J]. Radiocarbon, 2016, 58(2):407-418. doi: 10.1017/RDC.2016.9
De Rooij M, Van Der Plicht J, Meijer H A J.Porous iron pellets for AMS 14C analysis of small samples down to ultra-microscale size (10-25μg C)[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2010, 268(7-8):947-951. doi: 10.1016/j.nimb.2009.10.071
Yokoyama Y, Koizumi M, Matsuzaki H, et al.Developing ultra small-scale radiocarbon sample measurement at the University of Tokyo[J]. Radiocarbon, 2010, 52(3):310-318. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=RDC52_02-JATSRDCRDC52_02S0033822200045355h.xml
Walter S, Sunita R, Gagnon A R, et al.Ultra-small graphitization reactors for ultra-microscale 14C analysis at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility[J]. Radiocarbon, 2015, 57(1):109-122. doi: 10.2458/azu_rc.57.18118
Guaciara M, Santos X X.Bag of Tricks:A set of tech-niques and other resources to help 14C laboratory setup, sample processing, and beyond[J]. Radiocarbon, 2016, 59(3):785-801.
Dunbar E, Cook G T, Naysmith P, et al.AMS 14C dating at the Scottish Universities Environmental Research Centre (SUERC) Radiocarbon Dating Laboratory[J]. Radiocarbon, 2016, 58(1):9-23. doi: 10.1017/RDC.2015.2
Brown T A, Southon J R.Corrections for contamination background in AMS 14C measurements[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 1997, 123(1):208-213. http://www.sciencedirect.com/science/article/pii/S0168583X96006763
Donahue D J, Linick T W, Jull A J T.Isotope-ratio and background corrections for accelerator mass spectrometry radiocarbon measurements[J]. Radiocarbon, 1990, 32(2):135-142. doi: 10.1017/S0033822200040121
Aggarwal P K, Araguas-Araguas L, Choudhry M, et al.Lower groundwater 14C age by atmospheric CO2 uptake during sampling and analysis[J]. Groundwater, 2014, 52(1):20-24. doi: 10.1111/gwat.12110
Yang B, Smith A M, Hua Q.A cold finger cooling system for the efficient graphitisation of microgram-sized carbon samples[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2013, 294(1):262-265. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=68ee53bd7e547b58c75aa37e0fba8198
Liebl J, Steier P, Golser R, et al.Carbon background and ionization yield of an AMS system during 14C measurements of microgram-size graphite samples[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2013, 294(1):335-339. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=92638b69d4f9f411fe72d8e43c9b2fb3
Hajdas I, Bonani G, Thut J, et al.A report on sample preparation at the ETH/PSI AMS facility in Zurich[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2004, 223-224(1):267-271. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=4b14e45da646de3adf44180e7de7bddc
Sakamoto M, Wakasa S, Matsuzaki H, et al.Design and performance tests of an efficient sample preparation system for AMS-14C dating[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2010, 268(7-8):935-939. doi: 10.1016/j.nimb.2009.10.068
Wacker L, Němec M, Bourquin J.A revolutionary graphi-tisation system:Fully automated, compact and simple[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2010, 268(7):931-934. http://www.sciencedirect.com/science/article/pii/S0168583X09011161
Nagasawa S, Kitagawa H, Nakanishi T, et al.An app-roach toward automatic graphitization of CO2 samples for AMS 14C measurements[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2013, 294(1):266-269. http://www.sciencedirect.com/science/article/pii/S0168583X12005769
Solís C, Chávez E, Ortiz M E, et al.AMS-C14 analysis of graphite obtained with an Automated Graphitization Equipment (AGE Ⅲ) from aerosol collected on quartz filters[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2015, 361:419-422. doi: 10.1016/j.nimb.2015.05.027
Yang B, Smith A M, Long S.Second generation laser-heated microfurnace for the preparation of microgram-sized graphite samples[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2015, 361(1):363-371. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=d312e5fc58e8312b88219ca94e8838ac
Mojmír N L W, Gäggeler H.Optimization of the graphiti-zation process at Age-1[J]. Radiocarbon, 2010, 52(2-3):1380-1393. http://journals.cambridge.org/abstract_S0033822200046464
Wacker L, Fülöp R H, Hajdas I, et al.A novel approach to process carbonate samples for radiocarbon measurements with helium carrier gas[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2013, 294:214-217. doi: 10.1016/j.nimb.2012.08.030
Mcintyre C P, Roberts M L, Burton J R, et al.Rapid radiocarbon (14C) analysis of coral and carbonate samples using a continuous-flow accelerator mass spectrometry (CFAMS) system[J]. Paleoceanography, 2011, 26(4):PA4212. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=418fb4baa10e8cca6d861cf187e80e7c
Longworth B E, Robinson L F, Roberts M L, et al.Car-bonate as sputter target material for rapid 14C AMS[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2013, 294(1):328-334. http://www.sciencedirect.com/science/article/pii/S0168583X12002819
Kitagawa H.CO2-laser decomposition method of car-bonate for AMS 14C measurements[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2013, 294(1):218-220. http://www.sciencedirect.com/science/article/pii/S0168583X12005782
Wacker L, Münsterer C, Hattendorf B, et al.Direct coup-ling of a laser ablation cell to an AMS[J]. Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, 2013, 294(1):287-290. http://www.sciencedirect.com/science/article/pii/S0168583X12001061
Münsterer C, Wacker L, Hattendorf B, et al.Rapid reve-lation of radiocarbon records with laser ablation accelerator mass spectrometry[J]. Chimia, 2014, 68(4):215-216. doi: 10.2533/chimia.2014.215
Welte C, Wacker L, Hattendorf B, et al.Optimizing the analyte introduction for 14C laser ablation-AMS[J]. Journal of Analytical Atomic Spectrometry, 2017, 32(9):1813-1819. doi: 10.1039/C7JA00118E
Welte C, Wacker L, Hattendorf B, et al.Laser ablation-accelerator mass spectrometry:An approach for rapid radiocarbon analyses of carbonate archives at high spatial resolution[J]. Analytical Chemistry, 2016, 88(17):8570-8576. doi: 10.1021/acs.analchem.6b01659
Welte C, Wacker L, Hattendorf B, et al.Novel laser ablation sampling device for the rapid radiocarbon analysis of carbonate samples by accelerator mass spectrometry[J]. Radiocarbon, 2016, 58(2):419-435. doi: 10.1017/RDC.2016.6
Kim S H, Kelly P B, Clifford A J.Accelerator mass spectrometry targets of submilligram carbonaceous samples using the high-throughput Zn reduction method[J]. Analytical Chemistry, 2009, 81(14):5949-5954. doi: 10.1021/ac900406r
-
期刊类型引用(12)
1. 来素涵,孙阳阳,李帅,王晓波. 土壤硒与有机质的作用机制及其对生物有效性的研究进展. 中国无机分析化学. 2025(02): 218-230 . 百度学术
2. 李媛媛,焦洪鹏,冯先翠,曹鹏,江海燕,雷满奇. 施用硒内源调控剂对水稻吸收硒、镉和砷的影响. 中国稻米. 2024(02): 18-25 . 百度学术
3. 王安,吴美玲,李忠元,周玉强,黄占斌. 钢渣应用于土壤修复的研究进展. 环境工程技术学报. 2023(04): 1535-1543 . 百度学术
4. 甄常亮,程翠花,张巧荣,赵凯. “两步法”重构钢渣物相变化特征及黏度调控机制. 钢铁. 2023(07): 144-153 . 百度学术
5. 杨谨铭,胡岗,范成五,罗沐欣键,秦松. 提高土壤硒生物有效性的技术措施研究进展. 安徽农业科学. 2022(01): 12-14 . 百度学术
6. 吴超,孙彬彬,陈海杰,成晓梦,贺灵,曾道明. 应用梯度扩散薄膜技术评价天然富硒土壤中硒的生物有效性. 岩矿测试. 2022(01): 66-79 . 本站查看
7. 董先锋,卢洪斌,卢少勇,王涛,弥启欣,李嘉欣,李响. 钢渣用于多级人工湿地导致出水pH值升高潜能及调控措施. 环境科学与技术. 2022(S1): 89-96 . 百度学术
8. 斯鑫鑫,唐尙柱,赵晓海,王顺永,李玉成. 蓝藻有机富硒肥的研制及其在普通白菜种植中的应用. 江苏农业学报. 2021(02): 340-347 . 百度学术
9. 王吉凤,付恒毅,闫晓彤,王乐,王鹏程. 钢渣综合利用研究现状. 中国有色冶金. 2021(06): 77-82 . 百度学术
10. 李海强. 天然富硒土壤上不同作物对硒的吸收与转化差异. 农村科学实验. 2020(03): 42-44 . 百度学术
11. 周殷竹,王彪,刘义,王思源,周金龙. 青海囊谦县城周边农耕区土壤质量地球化学评价及富硒土地利用分区. 干旱区资源与环境. 2020(10): 93-101 . 百度学术
12. 周殷竹,刘义,王彪,周金龙,王思源. 青海省囊谦县农耕区土壤硒的富集因素. 地质通报. 2020(12): 1952-1959 . 百度学术
其他类型引用(7)