Examination into the Accuracy of Exchangeable Cation Measurement in Saline Soils

Abstract

Despite the increasing prevalence of salinity worldwide, the measurement of exchangeable cation concentrations in saline soils remains problematic. Two soil types (Mollisol and Vertisol) were equilibrated with a range of sodium adsorption ratio (SAR) solutions at various ionic strengths. The concentrations of exchangeable cations were then determined using several different types of methods, and the measured exchangeable cation concentrations were compared to reference values. At low ionic strength (low salinity), the concentration of exchangeable cations can be accurately estimated from the total soil extractable cations. In saline soils, however, the presence of soluble salts in the soil solution precludes the use of this method. Leaching of the soil with a prewash solution (such as alcohol) was found to effectively remove the soluble salts from the soil, thus allowing the accurate measurement of the effective cation exchange capacity (ECEC). However, the dilution associated with this prewashing increased the exchangeable calcium (Ca) concentrations while simultaneously decreasing exchangeable sodium (Na). In contrast, when calculated as the difference between the total extractable cations and the soil solution cations, good correlations were found between the calculated exchangeable cation concentrations and the reference values for both Na (Mollisol: y=0.873x and Vertisol: y=0.960x) and Ca (Mollisol: y=0.901x and Vertisol: y=1.05x). Therefore, for soils with a soil solution ionic strength greater than 50 mM (electrical conductivity of 4 dS/m) (in which exchangeable cation concentrations are overestimated by the assumption they can be estimated as the total extractable cations), concentrations can be calculated as the difference between total extractable cations and soluble cations.     

Sodium Hydroxide Direct Distillation: A Method for Estimating Total Nitrogen in Soil

Soil total nitrogen (N) concentration is commonly measured by Kjeldahl and combustion methods. In this study, a method based on determination of ammonium (NH₄)‐N produced by steam distillation of the soil sample with sodium hydroxide solution (NaOH‐DD) is developed and evaluated for estimating soil total N concentration. The method was evaluated using two sample sets: (A) 44 samples collected from contrasting land uses in central Iran and (B) 344 samples collected from contrasting arable soils across Canada and Maine, USA. Based on this experiment, 10‐min distillation of 5.0 g soil with 20 mL 12.5 M NaOH were selected as the optimum conditions. The NH₄‐N released by the NaOH‐DD method was highly correlated with total N concentration in the sample sets A and B (r = 0.79 and 0.94, respectively). The NaOH‐DD method provides a simple, rapid means of analysis with reduced measurement cost and better health and safety precautions than the traditional Kjeldahl method. Current address for Mehdi Sharifi: Nova Scotia Agricultural College, Department of Plant and Animal Science, Truro, Canada.      

高温复合菌系WSC-6预处理稻秆对沼气生产的影响

为提高稻秆在沼气生产中的水解酸化效率,寻求复合菌系WSC-6生长的廉价氮源,降低稻秆酸化水解的运行成本,该试验利用高温复合菌系WSC-6,以未经处理的稻秆为碳源,分别以新鲜猪粪和干猪粪为氮源,对稻秆进行生物预处理。研究结果表明,高温复合菌系WSC-6对新鲜猪粪中的氮源利用更充分,总氮利用率达到81.5%,对稻秆的降解率也高于干猪粪,稻秆的总质量损失率达到48.3%,纤维素、半纤维素和木质素的降解率分别达到67.3%、79.3%和27.9%。在稻秆的生物预处理中,无论采用哪种氮源方式,反应系统的pH值都在6.5～8.2之间变化,不会产生酸化现象。以新鲜猪粪代替蛋白胨作为稻秆生物预处理的氮源,既降低了稻秆生物预处理的运行成本,又消除了猪粪造成的环境污染,这对沼气的工业化生产具有重要的应用价值。     

沼液联合冻融预处理对水稻秸秆理化特性的影响

农业秸秆厌氧发酵生产沼气、氢气潜力巨大,然而受其自身结构影响,秸秆直接厌氧发酵生物质能转化率较低,需要经过前期预处理以打破秸秆木质素的复杂结构,提高秸秆纤维素、半纤维素的利用率。冻融预处理秸秆技术操作简单、预处理效果好,但目前冻融预处理过程常用的酸碱浸泡液易造成潜在环境污染风险。该研究针对中国北方冬季气温低的特点,以水稻秸秆为原料,选取富含氨氮的厌氧发酵副产物：沼液作为浸泡液,模拟北方冬季自然平均最低气温（-20 ℃）,基于单因素、正交试验,系统研究沼液浸泡联合冻融预处理水稻秸秆的理化特性及规律。结果表明：沼液联合冻融预处理后,水稻秸秆的木质素结构及分子间氢键发生显著破坏,O-H、C-H、C＝C、C＝N、N＝N、N＝O等基团的吸收峰均呈现减弱趋势,水稻秸秆晶型结构未改变,但结晶度显著降低,最低降至29.82%,比较原秸秆结晶度减少21.38%;沼液浸泡过程可将水稻秸秆C/N显著降至30以下,而冻融过程对沼液浸泡后秸秆C/N的影响不显著,最低降至28.19;浸泡时间与冻融循环次数对木质素去除率交互影响显著,而浸泡温度与浸泡时间、液固质量比对挥发性脂肪酸（VFAs）浓度均具有显著交互影响,沼液联合冻融预处理水稻秸秆过程木质素去除率和VFAs浓度最高达到40.06%和4 140 mg/L。研究结果为北方冬季秸秆冻融预处理的低成本广泛应用及冻融预处理的无害化奠定理论基础。     

不同预处理对超磁分离污泥水解产酸效果的影响研究

超磁分离污泥是以磁絮凝反应和磁种回收为核心技术,通过超磁分离机浓缩排出的污泥.污泥具有有机质浓度高、结构紧密等特点.该研究以超磁污泥为研究对象,通过批式试验考察了NaOH,H2O2和Fe预处理后污泥水解酸化的效果以及溶解性有机物特征.结果 表明,NaOH预处理加速了污泥的水解酸化,提高了可溶性物质的含量.NaOH处理组...     

微氧预处理对有机废水厌氧消化产甲烷的影响

为了考察微氧预处理对有机废物厌氧消化产甲烷过程的影响,论文以合成废水为试验材料进行了试验研究。结果表明,在厌氧消化反应前进行一定时间的微氧预处理,可以强化水解产酸菌的作用,促进有机底物的水解酸化,从而有效促进甲烷的产生。微氧预处理4 h可以提高甲烷产量28%,提高最大产甲烷速率57.5%。10 h的预处理则对产甲烷菌具有毒害作用,甲烷产量显著降低,预处理时间过短,促进效果不明显。最佳的预处理时间为4～6 h。微氧预处理在控制好处理时间时可促进有机物水解酸化,因此可应用于复杂有机物如厨余垃圾等的厌氧发酵。     

H2O2预处理对不同水稻品种Cd耐性的影响

 以耐性不同的两个水稻品种N07 63和N07 6为材料,采用水培法研究了镉（Cd）胁迫下过氧化氢（H2O2）预处理对水稻Cd耐性和吸收转运的影响及品种间差异。比较了两个品种不同处理下丙二醛（MDA）、还原型谷胱甘肽（GSH）、非蛋白巯基（NPT）、植物络合素（PCs）含量以及谷胱甘肽硫转移酶（GST）活性的变化。结果表明,50 μmol/L Cd处理显著抑制水稻生长,提高GSH、NPT、PCs、MDA含量和GST活性,且品种间差异显著。从Cd在水稻植株中的分布上看,N07 6向地上部转运的Cd比N07 63多。H2O2预处理后,两个品种Cd毒害效应减轻,GSH、NPT、PCs含量和根部GST活性得到进一步提高,且N07 63的增幅高于N07 6,其耐性也提高更多。H2O2预处理降低了两个品种的Cd向地上部转运,但对根部Cd含量存在不同的影响。从上述结果可以推测,两个品种在Cd解毒机制和对H2O2的响应上存在明显差异。     

“美婷”原料药在鱼肌肉组织中残留检测前处理方法

对高效液相色谱法测定草鱼和鲫肌肉组织中“美婷”原料药残留的前处理方法进行探讨。结果表明：以甲醇作抽提剂、二氯甲烷作净化剂,振荡离心,正己烷去脂, 30℃旋转浓缩蒸发的前处理方法,快速、准确、经济、实用性强。该方法“美婷”原料药的最低检测限可达1.0 μg/kg;在加标水平为1.0～100 μg/kg时,回收率为67.72％～95.52％;相对标准偏差为7.76％～37.81％。该前处理方法适合检测“美婷”原料药在鱼体内的残留。     

蒸汽爆破/氧化钙联合预处理对水稻秸秆厌氧干发酵影响研究

为了提高水稻秸秆在厌氧干发酵中的利用效率,采用蒸汽爆破、氧化钙以及蒸汽爆破/氧化钙联合预处理(以下简称"联合处理")水稻秸秆,考察不同处理方式对水稻秸秆的理化性质和厌氧干发酵的影响。结果表明:从扫描电子显微镜照片观察到,联合处理组与其他处理方式相比对水稻秸秆结构破坏最彻底。木质素含量测试结果显示,经过联合处理水稻秸秆中木质素含量从17.2%下降到12.2%,去除率可达29.1%。纤维素酶水解实验中,联合处理组的葡萄糖产量与木糖产量分别为877.56 mg·L~(-1)和400.85 mg·L~(-1),比CK组提高了85.43%和1 283.39%。在厌氧干发酵实验中,联合处理组产甲烷延滞期最短(5 d),比CK组缩短了约6 d,第30 d累积产甲烷量占总产甲烷量(60 d)的86.4%,而CK组仅占55.7%,原料产甲烷率提升最明显(0.24 L·g-1VS),比CK组提高了20.0%。动力学模型拟合结果表明,与蒸汽爆破处理、氧化钙处理相比,联合处理组对厌氧干发酵的促进作用最显著。     

辣椒花药培养的初步研究

以20个不同辣椒品种为材料,采取固液双层培养体系及低温预处理方式,探索基因型、基本培养基及激素组合、活性炭和低温预处理时间对花药培养的影响,以期为建立高效辣椒花药培养体系奠定基础.结果表明,获得了多种不同形态的胚状体及愈伤组织,以及4个易出胚甜椒基因型材料,分别为红英达、欧卡、巴顿和环球201.MS+0.05 mg/L KT--0.005 mg/L 2,4-D以及NLN-H+ 0.5 mg/L ZT+0.5 mg/L IAA培养基适合多个辣椒基因型成功出胚,出胚率最高达4.2％.4℃低温预处理24 h以及添加0.5 g/L活性炭均可以提高辣椒胚状体诱导率.