用氯离子选择电极测定土壤中的含氯量

土壤中含氯量的测定,长期以来采用硝酸汞或硝酸银的比色滴定法,由于土壤提取液比较浑浊或指示剂变色不灵敏,因而妨碍了滴定精度的提高,近年来氯离子选择电极的应用,得到了广泛的重视^[1,2],对于有色溶液与混浊液的测定,特别方便。     

用钙黄绿素作指示剂络合滴定土壤交换性钙

在测定盐基总量后的溶液中,用络合滴定法测定交换性钙,土壤常规分析方法^[1]采用钙指示剂作指示剂,由于该指示剂能被氢氧化镁沉淀所吸附,也易受铝及重金属离子之"封闭",因此最近资料^[2]又复用早期应用过的紫脲酸铵,后者不受"封闭",但滴定终点由红色边紫色较难辨认。     

离子选择性电极测定污染土壤或废水中的氰

用离子选择性电极测定工业废水^[1,2]或饲料^[3]等样品中的氰是快速而简便的方法,但用于污染土壤中氰的测定尚未见报导。     

用钾电极快速测定酸性及中性土壤中的速效性钾

自七十年代以来,离子选择性电极在工农业生产中日益得到广泛的应用^[1],在土壤研究中已用钾电极测定土壤溶液中的钾^[2];我们也曾用钾玻璃电极测定窑灰钾肥的含钾量和用1NHNO₃提取土壤的酸溶性钾,结果都比较满意^*。     

用硝酸根电极测定土壤中的硝态氮

土壤中硝态氮的测定,在常规分析中多应用比色法,但受限制较多,精度也较差。还原氨法准确度较高,但需经蒸馏与滴定等手续。近年来,国外用新发展的硝酸根离子选择性电极测定土壤硝态氮已有某些结果^[1,2]。     

微机电位自动滴定系统测定土壤全氮

一、方法原理氮素是植物生长三要素之首,土壤中的氮素含量与植物生长直接相关,是土壤肥力的重要指标之一。测定土壤全氮一般用硫酸和混合催化剂消化,使N转化成NH₄⁺,加碱蒸馏,用H₃BO₃吸收蒸出的NH₃,然后用标准酸溶液滴定^[1]。     

用钠离子选择性电极测定土壤提取液中的钠

用离子选择性电极测定土壤提取液中含钠量的方法已有报导^[1,2]。根据生产实践的需要,希望获得一种测量范围较宽,响应时间较短,准确度较好的电极。     

无结构土壤透气性的初步研究

土壤的透气性是指土壤让空气穿透本身的能力。透气性是土壤很重要的物理性质,因为它不仅决定了土壤与大气间空气交换的速度^[1],而且和土壤的持水性有关^[2],测定土壤的透气性还可以了解土壤其他一系列的物理性质如排水的能力^[3]、地表迳流的速度^[2]、耐蚀性、空气容量^[3]及其结构性的程度等等。土壤中微生物活动的方向与强度、种籽的发芽、根系的发育及其吸收能力、土壤中养分的状态^[4]和影响农作物生活的其他重要土壤因素都有赖于土壤的透气性。     

天津地区土壤中若干金属元素间的相关性

土壤中的元素主要来源于成土母质^[1],但在风化成土过程中,元素的迁移与富集能力各不相同。为了寻求土壤中元素间的内在联系,判断元素的含量和分布状况,元素间的相关分析法是良好的方法之一。例如,Ure等^[6]测定了苏格兰不同母质的土壤中多种微量元素含量,并讨论了各元素间的相互关系。Pilotte等^[5]用相关性分析法对河口地区沉积物中元素含量进行判断,浅见辉男等^[4]用元素相关性描述了沉积物中元素分布,梁伟^[5]用元素相关性对土壤背景值进行判断等。本文根据天津地区土壤表土中16个元素之间的相关系数,探讨元素的地球化学性质对元素间的相关性的影响。     

应用差示脉冲溶出伏安法测定土壤溶液中的可溶态锌

近十几年来,对土壤中Zn行为的研究日益增多,结果表明,Zn的生物有效性与土壤中Zn的形态密切相关。测定Zn的方法因其形态而异。通常,测定全Zn量、有效态Zn量和DTPA溶液提取Zn量可用比色法、原子吸收光谱法或普通极谱法^[1,2]。当天然水和土壤溶液中可溶态Zn含量低至只有几十个ppb或更少时,则需要用灵敏度更高的阳极溶出伏安法(ASV)或差示脉冲阳极溶出伏安法(DPASV)进行测定^[3,4]。     

应用微分电位滴定仪测定盐渍土中氯离子的初步研究

在盐渍化土壤中,阴离子氯具有高度的迁移性,土壤水盐运动的状况常借氯离子动态变化来指示,此外,氯离子对植物的危害,也比其他阴离子显著.因此,氯离子的测定,不论在理论研究上或在生产实践中都有一定的意义.盐渍土中含氯量的测定,一般用容量滴定法(莫尔法),但因其终点显示是用目测指示剂的颜色变化来决定,待测标本如果混浊或有色,就会给测定带来一定困难.     

温度滴定法测定复合肥中钾离子浓度的研究

复合肥中钾元素的检测可有效控制复合肥产品的质量。本研究选取合适的前处理方法,并应用温度滴定法对复合肥中的钾离子进行了定量研究。该法测定复合肥中的钾离子以四苯硼钠与钾离子生成沉淀反应为基础,由于反应是放热反应,当滴定到等当点时,反应室的温度变化率最大,指示终点的到达。该方法具有操作简便、快速、灵敏度高等优点,非常适合对复合肥中钾离子含量的监控。研究结果表明,使用温度滴定法和离子色谱法及四苯硼酸钾重量法测得的复合肥中钾离子含量一致,该方法准确度高,重现性好,回收率可达97%以上。     

普钙、磷矿中磷的螯溶-差示光度法测定的研究

本文介绍了螯溶-差示光度分析技术用于分析高含量磷的普钙、磷矿样品.提出螯溶反应的机理及其示意式,由测定条件试验得到了螯溶剂在螯溶条件下的极限浓度及其pH值.控制溶解液中柠檬酸溶液浓度,即可防止柠檬酸对钼黄显色的抑制影响,氟离子对钼黄显色的干扰由铝离子络合以消除.用酸溶螯溶-钼酸喹啉重量法作对比试验以及磷的回收试验,验证了螯溶-差示光度法的精密度和准确度.所获结果表明,与酸溶-钼酸喹啉重量法结果比较,含磷高的磷矿,本法的相对误差小于±1%;含磷较低的普钙,其相对误差约为±1.5%.磷的回收率均在99.0-100.4%之间.本法干扰少、无污染,节省设备、试剂,溶样手续简便快速,分析结果准确可靠.     

甘薯不同氯离子测定方法的比较研究

采用加标回收率的方法,分析并比较了硝酸银滴定法、紫外分光光度法和自动电位滴定法测定甘薯(Ipomoea batatas L.)幼苗Cl-含量的结果,并初步探明不同甘薯品种地上部和根系C1-吸收和分布规律.结果表明:(1)硝酸银滴定法重复性差且难以判断滴定终点;紫外分光光度法测定Cl-回收率低(52.9％～81.4％),且受样品浸提液颜色影响;自动电位滴定法Cl-回收率为93.9％～105.5％,相对标准偏差(RSD)为0.6％～ 6.0％,该方法操作简单、重复性好且精确度高,因此是测定甘薯氯含量的最佳方法;(2)利用自动电位滴定法测定不同甘薯品种Cl-积累和分布,结果显示:甘薯幼苗地上部Cl-含量为0.067～0.096 mmol g-1DW,根系Cl-含量为0.038～0.087 mmol g-1 DW,品种间甘薯幼苗地上部和根系Cl-含量皆存在显著差异.不同品种向地上部转运Cl-选择性比率均大于1.0,表明Cl-向地上部聚集,以菜用型福薯7-6比率最高,紫心型徐紫20-1和浙紫1号次之,淀粉型泉薯9号最低.     

A rapid and precise method for routine determination of organic carbon in soil

Abstract

A simple method for routine determination of organic carbon in soil by a modified Mebius procedure is described. It involves (a) digestion of the soil sample with an acidified dichromate (K₂Cr₂O₇‐H₂SO₄) solution for 30 minutes in a Pyrex digestion tube in a 40‐tube block digester preheated to 170°C and (b) estimation of the unreacted dichromate by titration of the cooled digest with an acidified solution of ferrous ammonium sulfate with use ofN‐phenylanthranilic acid as an indicator. The method is more rapid and precise than the Mebius procedure commonly used for routine analysis of soils for organic carbon, and the only equipment required for its use is equipment now commonly used for routine Kjeldahl analysis of soils for total nitrogen.     

赤峰杨幼林枝条水势及生长对水分胁迫的响应

通过对赤峰杨幼林地进行控水试验,测定了不同程度干旱胁迫下赤峰杨枝条水势、幼林平均株高、地径生长量及生长状况等指标。结果表明,当土壤含水量高于15.6%时,赤峰杨枝条水势没有明显变化,低于11.03%时,枝条水势迅速下降;当土壤含水量大于(17.72±2.75)%时,赤峰杨幼树生长正常,生长量增加趋势快速明显,而当土壤含水量低于(7.12±2.75)%时,赤峰杨出现严重衰退特征,生长基本停滞,个体开始出现死亡。综合分析枝条水势、株高生长、地径生长等指标,表明有利于赤峰杨幼林快速生长,并维持林分稳定的适宜土壤水分含量为大于(17.72±2.75)%。     

运用四苯硼钠法准确测定土壤有效钾素变化的初步探讨

通过室内实验探讨了四苯硼钠法用来测定土壤有效K素变化的效果及其提取条件。结果表明,四苯硼钠法提取的土壤K量因四苯硼钠浓度、提取时间以及提取温度而有显著的变化。选择较高的四苯硼钠浓度、较长的提取时间或较高的提取温度均会显著促进四苯硼钠对土壤中非交换性K的提取。研究初步提出的一种土壤有效K素变化的测定方法,从12种土壤中提取的K量分别为各土壤常规缓效K值的2.3～7.4倍。当土壤添加100～2500mg/kg的外源K后,12种土壤中用该法测定的K素变化的回收率绝大多数在90%～110%之间,平均为101.9%±8.2%,说明改进后的四苯硼钠法将可以用来测定土壤中的有效K素变化。     

Microwave irradiation of soil for routine measurement of microbial biomass carbon

 Microwave irradiation was evaluated as a non-toxic alternate to chloroform fumigation for routine measurement of soil microbial biomass C. Microwave energy was applied to moist soil to disrupt microbial cells. The flush of C released was then measured after extraction or incubation. Microwave irradiation at 800 J g^–1 soil was optimal because this level resulted in an almost instantaneous rise in soil temperature (≥80  °C), an abrupt reduction in microbial activity, maximal release of biomass C, and minimal solubilization of humic substances. Both incubation-CO₂ titration and extraction-colorimetry methods were used on separate 20-g subsamples to compare the labile C in the microwave-treated and untreated soil samples. The incubation-titration method was also used to measure C in chloroform-fumigated soil samples. Averaged across soils, the chloroform fumigation yielded 123.3±5.1 mg CO₂-C kg^–1. Microwave irradiation yielded 93.6±3.9 mg CO₂-C kg^–1 soil determined by incubation and 52.4±2.4 mg C kg^–1 soil determined by extraction, accounting for 76% and 42% of the net flush of C measured by the chloroform fumigation. Microwave-stimulated net flushes of C were correlated closely (r ²=0.974 for incubation or 0.908 for extraction) with microbial biomass C measured by the chloroform fumigation. Little correlation was found with the total soil organic C (r ²=0.241 for incubation or for 0.166 extraction). Mean efficiency factors for incubation (K _MI) or extraction (K _ME) were used to calculate microbial biomass C from net flushes of C between microwaved and unmicrowaved soils. Values of K _MI and K _ME were not affected by soil pH, bulk density or clay contents. Extraction of microwaved soil by 0.5M K₂SO₄ proved to be a simple, fast, precise, reliable, and safe method to measure soil microbial biomass C. Received: 12 September 1997     

Quantifying microbial biomass phosphorus in acid soils

 This study aimed to validate the fumigation-extraction method for measuring microbial biomass P in acid soils. Extractions with the Olsen (0.5 M NaHCO₃, pH 8.5) and Bray-1 (0.03 M NH₄F–0.025 M HCl) extractants at two soil:solution ratios (1 : 20 and 1 : 4, w/v) were compared using eight acid soils (pH 3.6–5.9). The data indicated that the flushes (increases following CHCl₃-fumigation) of total P (P_t) and inorganic P (P_i) determined by Olsen extraction provided little useful information for estimating the amount of microbial biomass P in the soils. Using the Bray-1 extractant at a soil:solution ratio of 1 : 4, and analysing P_i instead of P_t, improves the reproducibility (statistical significance and CV) of the P flush in these soils. In all the approaches studied, the P_i flush determined using the Bray-1 extractant at 1 : 4 provided the best estimate of soil microbial biomass P. Furthermore, the recovery of cultured bacterial and fungal biomass P added to the soils and extracted using the Bray-1 extractant at 1 : 4 was relatively constant (24.1–36.7% and 15.7–25.7%, respectively) with only one exception, and showed no relationship with soil pH, indicating that it behaved differently from added P_i (recovery decreased from 86% at pH 4.6 to 13% at pH 3.6). Thus, correcting for the incomplete recovery of biomass P using added P_i is inappropriate for acid soils. Although microbial biomass P in soil is generally estimated using the P_i flush and a conversion factor (k _P) of 0.4, more reliable estimates require that k _P values are best determined independently for each soil. Received: 3 February 2000     

Glufosinate and ammonium sulfate inhibit atrazine degradation in adapted soils

The co-application of glufosinate with nitrogen fertilizers may alter atrazine cometabolism, thereby extending the herbicide’s residual weed control in adapted soils. The objective of this study was to assess the effects of glufosinate, ammonium sulfate, and the combination of glufosinate and ammonium sulfate on atrazine mineralization in a Dundee silt loam exhibiting enhanced atrazine degradation. Application of glufosinate at rates of 10 to 40 mg kg⁻¹ soil extended the lag phase 1 to 2 days and reduced the maximum degradation rate by 15% to 30%. However, cumulative atrazine mineralization averaged 85% 21 days after treatment and was independent of treatment. Maximum daily rates of atrazine mineralization were reduced from 41% to 55% by application of 1 to 8 g kg⁻¹ of ammonium sulfate. Similarly, cumulative atrazine mineralization was inversely correlated with ammonium sulfate rates ranging from 1.0 to 8 g kg⁻¹ soil. Under the conditions of this laboratory study, atrazine degradation was relatively insensitive to exogenous mineral nitrogen, in that 8 g (NH₄)₂SO₄ per kilogram soil repressed but did not completely inhibit atrazine mineralization. Moreover, an additive effect on reducing atrazine mineralization was observed when glufosinate was co-applied with ammonium sulfate. In addition, ammonium fertilization alters the partitioning of ¹⁴C-atrazine metabolite accumulation and nonextractable residues, indicating that ammonium represses cleavage of the triazine ring. Consequently, results indicate that the co-application of glufosinate with N may increase atrazine persistence under field conditions thereby extending atrazine residual weed control in adapted soils.