Optimizing soil dissolved organic matter extraction by grey relational analysis

Dissolved organic matter(DOM) in soil plays an important role in the fate and transport of contaminants.It is typically composed of many compounds,but the effect of different extraction factors on the abundance of different DOM components is unknown.In this study,DOM was extracted from three soils(paddy field,vegetable field and forest soils) with various extraction time,liquid to solid ratios(LSRs),extractant types,and extractant concentrations.The LSR had a significant effect on DOM content,which increased by 0.5–4.0 times among the three soils when LSR increased from 2:1 to 10:1(P 0.05).Dissolved organic matter content increased by 4%–53% when extraction time increased from 10 to 300 min(P 0.05).Extractant concentration had different effects on DOM content depending on the extractant.Higher concentrations of KCl promoted DOM extraction,while higher concentrations of KH_2PO_4 inhibited DOM extraction.Therefore,grey relational analysis was used to further quantitatively evaluate the effect of extraction time,LSR,and extractant concentration on DOM,using KCl as an extractant.For the paddy field and forest soils,the impact of these three factors on DOM extraction efficiency was in the following order:KCl concentration LSR extraction time.However,the effect was different for the vegetable field soil:LSR extraction time KCl concentration.Taking all these factors into account,1.50 mol L~(-1) KCl and an LSR of 10:1 with a shaking time of 300 min was recommended as the most appropriate method for soil DOM extraction.     

三种无机萃取剂去除土壤中PbCd的条件研究

通过对重金属污染土壤的萃取实验,比较了HCl、Na2S2O3、CaCl2 3种常用无机萃取剂对重金属Ph和cd的萃取效果,并通过改变萃取条件（萃取剂浓度、时间、固液比、萃取次数和温度）,以期找到各种萃取剂达到最大萃取效率时所需的萃取条件。结果表明,萃取剂浓度对于萃取效率的影响最大,随着浓度的提高,3种萃取剂对Ph、Cd的去除作用增强;固液比和萃取次数对Ph、Cd的去除率也有较大的影响;时间对两金属的去除率也有一定的影响,但在本实验条件下,达到萃取平衡所需时间很短;温度对萃取效率的影响很小。本实验中,HCl去除Pb、Cd的能力远远大于其他两种萃取剂。对Cd进行萃取时,需增加萃取次数才能达到较好的萃取效果。     

黑土中有效态镍提取方法的选择

供试7种提取剂的最佳提取条件是:提取温度均为(25±1)℃;提取时间为DTPA 2 h,醋酸铵30 min,其余5种提取试剂60 min;提取时的土液比为蒸馏水和DTPA 1∶2,醋酸铵1∶10,其余4种提取试剂1∶5。DTPA作为提取剂时,盆栽作物的吸镍量与有效镍提取量之间的相关性达到极显著水平,并好于其它试剂。DTPA和EDTA作为提取剂时,有效镍提取量与植株干物重之间均达极显著的负相关,且相关系数高于其他试剂。考虑到用DTPA作提取剂时,可以同时测定铜、锌、铁、锰多种金属元素,因此黑土中有效态镍的最佳提取试剂是DTPA,最佳提取条件为:温度(25±1)℃、土液比1∶2、180次min-1往复振荡提取2 h。     

Comparison of stirring and vortex mixing for the extraction of available nutrients from soil using a laboratory robot

Abstract

We investigated the efficiency with which a laboratory robot is able to extract available nutrients from soil contained in tubes. We have shown that for vortex mixing, the volume of soil and extractant are of critical importance. In cases where the soil/extractant volumes are small (e.g. 2 mL soil: 10 mL extractant), extraction of all the nutrients investigated was good. However, keeping the ratio the same, but increasing the volumes to 6 mL soil:30 mL extractant leads to an overall decrease in extracting efficiency. Using a paddle stirrer to mix the soil and extractant together results in the same extraction efficiency across the range of soil/ extractant volumes.     

Investigations on the Relationship between Extracting (DTPA) Solutions and Plant (Phaseolus vulgaris) in the Uptake of Cadmium and Lead from Latosols

Given the relationship between the contents of heavy metals extracted from contaminated soil samples and dilution of these samples in diethylenetriaminepentacetic acid (DTPA) solution, the goal of this work was to test three soil–extractant solution ratios, namely 1:5, 1:10, and 1:15. The extracted contents from each solution were compared to those extracted by bean plants (Phaseolus vulgaris) cultivated in a greenhouse in two different soils: dystrophic red latosol (RLd) and humic red-yellow latosol (RYLh). Contents of cadmium (Cd) and lead (Pb) were greater in RYLh (lower amount of clay) for all soil–extractant ratios; 1:5 and 1:10 ratios differed negligibly from the plant result for the Cd extraction, while for Pb, the 1:15 soil–extractant ratio was the one that better correlated with the extractive behavior of sensitive indicator plants.     

Extraction of nitrogen from soils

Summary A roller bed and rotary end-over-end shaker were compared for the extraction of mineral N from a variety of soil types; both were equally efficient with an optimum extraction time of 30 min. However, the roller bed permitted a greater operational capacity, a faster throughput of samples, and easier identification of sample bottles compared with the end-over-end shaker. More NH₄ ⁺-N and NO₃ ^–-N (P<0.001) was recovered from soil by 2 M KCl than by any other extractant, in a soil: extractant ratio of 1 to 5 (w:v), except water, which was equally efficient at removing NO₃ ^–-N from soils.     

Ultrasound Method for Extraction of Phosphorus in Soil

In the present work, an ultrasoundic procedure for the extraction of phosphorus (P) available in soil is described. The proposed method is based on extraction by 0.5 M sodium bicarbonate (NaHCO₃), following with sonication under different conditions. Phosphorus was determined by the Murphy and Riley method. Sonication time and soil–extractant relative quantities were optimized. A statistical analysis approach was used to find suitable conditions for the ultrasoundic extraction. The main advantages of the sonication method are the reduced times of extractions, which take 10 min in contrast to the 30 min required by a shaking method, and the possibility to reduce soil and extractant quantities from 5 g–100 mL to 2 g–40 mL. Performance of the method was evaluated, and the procedure was utilized to analyze soils from Santiago del Estero, Argentina.     

Nutrient accumulation and nitrate leaching under broiler litter amended corn fields

Abstract

Alabama's broiler chicken (Gallus gallus) industry produces large amounts of waste, which are disposed of by application to crop and pasture land. Land application of litter (manure and bedding) from broiler production can lead to contamination from losses of nutrients accumulated in soil. A study was conducted on 2 and 4% slopes from 1991 to 1993 at Belle Mina, Alabama, to determine the effects of broiler litter (BL) on soil elemental concentrations and nitrate leaching under a corn (Zea mays L.) ‐ winter rye (Secale cereale L.) cropping system amended with either: l) 9 mg#lbha^‐1 of BL, 2) 18 mg#lbha^‐1 of BL, or 3) commercial fertilizer (F) at a recommended rate. Soil was sampled to 100 cm prior to corn planting and subsequent to com harvest. Soil leachate samples were collected biweekly with wick lysimeters installed at a depth of 100 cm. Litter applications increased concentrations of soil organic carbon (C), extractable phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu) and zinc (Zn). Post harvest soil sampling indicated leaching of soil nitrate that was generally highest under BL18. Soil electrical conductivity measurements were highest under BL18, but values were not in the range considered detrimental to crops. Nitrate‐N (NO₃‐N) concentrations measured in soil percolate at 1‐m depth on the 2% slope were higher under F than litter treatments. Both the F and BL18 treatments produced some NO₃‐N concentrations above the primary drinking water standard, but averaged only 8.3 and 4.8 mg#lbL^‐1, respectively. The BL9 treatment consistently remained under 10 mg NO₃‐N#lbL^‐1 with a mean concentration of 1.3 mg#lbL^‐1. Overall, litter applied a 9 mg#lbha^‐1 produced agronomic results comparable to F and appeared to be the optimal rate of application under the conditions of this study.     

Filtration increases the correlation between water extractable organic carbon and soil microbial activity

A study was carried out in order to establish the relationship between the water extractable organic carbon (WEOC) content of soils and soil microbial activity, and to determine how variations in the extraction procedure might influence the quantity of WEOC recovered. Concentrations of WEOC were determined in soils taken from 12 different sites in the south east of Scotland, using a procedure in which samples were shaken with distilled water, centrifuged at 5000g and then filtered through 0.45 μm Millipore filters. Filtration resulted in between 30 and 400 μg C g⁻¹ being extracted using this procedure and the concentration of WEOC in the resultant extracts correlated with soil microbial production of CO₂ and dehydrogenase activity (P<0.001). Without filtration, although more WEOC was extracted (between 31 and 716 μg C g⁻¹), there was no significant correlation with biological activity. There was also no correlation between WEOC and nitrous oxide release during the incubations. Centrifugation at 20,000g for at least 10 min prior to filtration was required to remove particulate organic materials. Storage of samples at 4 °C or for up to 1 week or freezing for up to 3 months was not found to have a large influence on the concentration of WEOC in extracts, although amounts increased with soil:extractant ratio and increasing extraction time (from 15 to 60 min).     

固体稀释倍数和超声波对豆渣厌氧发酵酸化过程的影响

为了优化超声波对固体废弃物酸化过程的调节作用,缓解酸化产物抑制,该文研究超声波处理时不同稀释倍数对基质性质的影响及对处理后基质发酵性能的影响,根据基质的挥发性有机酸去除率和发酵性能选取较佳的超声波处理参数。试验结果表明,超声波对不同浓度酸化基质的处理可去除有机酸中80%以上的非电离有机酸,减小对微生物的毒害,同时可减小基质的颗粒尺寸。处理后的基质经10 d发酵以评价不同浓度条件下的酸化性能,当基质挥发性有机酸质量浓度在18.8 g/L左右时,将基质稀释至固体质量浓度为46 g/L后再进行超声波处理,基质的挥发性有机酸增长率和挥发性固体降解率可分别从仅经过超声波辐射处理的51.8%、14.7%提高到197.4%、26.8%,表现出较佳的处理性能。可为超声波调节固体废弃物酸化过程提供参考。     

预糊化条件对萌芽糙米蒸煮质构特性及品质的影响

为了解决萌芽糙米不易蒸煮且蒸煮后米饭口感较硬、黏弹性不足、粗糙感明显等问题,该文应用预糊化技术对萌芽糙米进行品质改良,评价了预糊化条件(米粒含水率43.21%±2.15%、34.64%±1.49%、29.83%±1.67%,蒸汽处理时间2、5、10、15、20、25 min)对萌芽糙米蒸煮特性、米饭质构特性及感官品质的影响。研究结果表明,随着米粒含水率的降低,预糊化萌芽糙米的蒸煮时间、蒸煮吸水率、体积膨胀率显著增大(P0.05),固形物损失率显著降低(P0.05);预糊化萌芽糙米的米饭硬度、黏附性、黏聚性、胶黏性、弹性、咀嚼性随米粒含水率降低的变化较为复杂。随着蒸汽处理时间的延长,预糊化萌芽糙米的蒸煮时间显著缩短(P0.05),蒸煮吸水率、体积膨胀率、固形物损失率变化较小且无明显规律;预糊化萌芽糙米的米饭硬度先减小后增大,黏附性、黏聚性先增大后减小,胶黏性、弹性、咀嚼性变化较为复杂。感官评定结果表明,预糊化萌芽糙米的米饭感官评分随米粒含水率降低的变化较为复杂,随蒸汽处理时间的延长先增大后降低。总体而言,米粒含水率29.83%±1.67%、蒸汽处理15 min的预糊化条件可以显著改善萌芽糙米的蒸煮特性、质构特性及感官品质,使其接近白米的品质指标。研究结果可为预糊化萌芽糙米的产业化开发提供依据。     

北京市松山不同海拔油松林枯落物及土壤水文效应

以北京市松山4个海拔梯度(751,890,1 012和1 211m)的油松(Pinus tabuliformis Carr)天然林为对象,对其枯落物层及土壤层水文效应进行研究。结果表明:(1)枯落物总蓄积量、枯落物最大持水量和最大持水率均随海拔的升高先增大后减小;(2)枯落物的总储量为9.03~27.75t/hm2,最大持水量为26.66~90.54t/hm2,与浸泡时间呈明显的对数关系(R0.93);最大持水率为287.62%~296.73%,与浸泡时间呈明显的幂函数关系(R0.99);(3)土壤容重随海拔升高而减小,其变化范围为1.38~1.66g/cm3,总孔隙度随海拔升高先减小后增大;(4)土壤初渗速率相差较大,稳渗速率为1.95~7.06mm/min,入渗速率与入渗时间呈幂函数关系(R0.70)。综合分析得出,低海拔油松天然林水源涵养功能较强。     

测定盐土中氯化物的捷法

在盐土中测定氯化物,通常将土壤和水混合,用1:2.5或1:5的比例摇动后过滤,在澄清的滤液中加一定量的硝酸,再用标准硝酸银(0.1N AgNo_3)来滴定氯化物,这个方法在一般的土壤分析书中都可以见到。由于土壤溶液制备的不易,特别是黏重的土壤,过滤很需要时间,并且不易得到澄清的溶液,所以分析的人,往往在制备溶液的一点上,化费了很多时间。     

Extractant ph and the release of phenolic compounds from soils,plant roots and leaf litter

The influence of pH was examined, over the range from 6 to 14, on the amounts of p-hydroxybenzoic, vanillic, p-coumaric, ferulic and syringic acids, p-hydroxybenzaldehyde and vanillin, extracted from four soils and associated roots or leaf litter. Adjustment of pH was obtained by the addition of graded amounts of Ca(OH)₂ to water or by 2 m NaOH. The roots associated with three of the soils were from permanent pasture, perennial ryegrass and red clover, while the leaf litter associated with the fourth soil was from beech.The amounts of each phenolic compound extracted increased continuously with increasing pH, from a “threshold” value which varied between pH 7.5 and 10.5. The amounts extracted by water alone from the soil under permanent pasture, at pH 5.8, were equivalent to concentrations in the soil solution ranging from 1.4 μm for p-hydroxybenzoic acid to < 10 nm for ferulie acid. Amounts of up to 2000 times greater than these were extracted by 2 m NaOH. Similar effects of extractant pH were found with the other soils.Comparisons of the amounts of the phenolic compounds extracted from the soils, with the amounts extracted from the associated roots or leaf litter, suggested that substantial proportions of the soil phenolic compounds were either derived from organic residues more than 4 yr old or were the result of microbial synthesis.     

不同水分条件下葡萄临界氮稀释曲线模型的建立及氮素营养诊断

以1a生葡萄植株“红提”为试材,在Venlo型试验温室内进行土壤水分和施氮量双因素区组试验。试验设置4个灌水水平,分别为正常灌溉量W1（田间最大持水量的70%～80%）、轻度水分胁迫W2（60%～70%）、中度水分胁迫W3（50%～60%）和重度水分胁迫W4（30%～40%）;设置4个施氮水平,分别为1.5倍推荐施氮量（N1,25.5g plant-1）、正常推荐施氮量（N2,17g plant-1）、0.5倍推荐施氮量（N3,8.5g plant-1）和不施用氮肥（N4,0g plant-1）。每10d观测一次植株体内氮浓度和植株地上部生物量,利用不同水分条件下葡萄植株在一定生长时期内所获最大生物量时对应的最小氮浓度值即临界氮浓度（Nc）构建葡萄临界氮浓度稀释曲线模型,并在此基础上建立氮素吸收模型（Nupt）和氮素营养指数模型（NNI）,对不同水分条件下葡萄氮营养状况进行定量诊断。结果表明：设施葡萄植株临界氮浓度与地上部生物量存在幂函数关系,随着灌水量的增加,葡萄植株临界氮浓度值增大,氮素吸收量及地上部生物量也呈增加趋势;在W1、W2水分条件下,葡萄植株生物量随施氮量增加而增加,而W3和W4处理葡萄生物量随施氮量增加呈先增后降的趋势;在相同水分条件下,氮浓度随施氮量增加而增加,随葡萄生长进程而降低;利用Nupt和NNI模型可对植株体内氮营养元素亏缺与否进行有效诊断。     

Influence of litter chemistry and stoichiometry on glucan depolymerization during decomposition of beech (Fagus sylvatica L.) litter

Glucans like cellulose and starch are a major source of carbon for decomposer food webs, especially during early- and intermediate-stages of decomposition. Litter quality has previously been suggested to notably influence decomposition processes as it determines the decomposability of organic material and the nutrient availability to the decomposer community. To study the impact of chemical and elemental composition of resources on glucan decomposition, a laboratory experiment was carried out using beech (Fagus sylvatica, L.) litter from four different locations in Austria, differing in composition (concentration of starch, cellulose and acid unhydrolyzable residue or AUR fraction) and elemental stoichiometry (C:N:P ratio). Leaf litter was incubated in mesocosms for six months in the laboratory under controlled conditions. To investigate the process of glucan decomposition and its controls, we developed an isotope pool dilution (IPD) assay using (13)C-glucose to label the pool of free glucose in the litter, and subsequently measured the dilution of label over time. This enabled us to calculate gross rates of glucose production through glucan depolymerization, and glucose consumption by the microbial community. In addition, potential activities of extracellular cellulases and ligninases (peroxidases and phenoloxidases) were measured to identify effects of resource chemistry and stoichiometry on microbial enzyme production. Gross rates of glucan depolymerization and glucose consumption were highly correlated, indicating that both processes are co-regulated and intrinsically linked by the microbial demand for C and energy and thereby to resource allocation to enzymes that depolymerize glucans. At early stages of decomposition, glucan depolymerization rates were correlated with starch content, indicating that starch was the primary source for glucose. With progressing litter decomposition, the correlation with starch diminished and glucan depolymerization rates were highly correlated to cellulase activities, suggesting that cellulose was the primary substrate for glucan depolymerization at this stage of decomposition. Litter stoichiometry did not affect glucan depolymerization or glucose consumption rates early in decomposition. At later stages, however, we found significant negative relationships between glucan depolymerization and litter C:N and AUR:N ratio and a positive relationship between glucan depolymerization and litter N concentration. Litter C:N and C:P ratios were negatively related to cellulase, peroxidase and phenoloxidase activities three and six months after incubation, further corroborating the importance of resource stoichiometry for glucan depolymerization after the initial pulse of starch degradation.     

基于三维荧光光谱的土壤溶解性有机质的提取

Soil dissolved organic matter(DOM) consists of many organic compounds and plays an important role in contaminant transport in the ecosystem. However, the effects of different extraction conditions on contents of different DOM components are poorly understood.We extracted DOM from three soils using different extraction times, solid to liquid ratios(SLR), and extraction solution(KCl)concentrations, and evaluated the extractions using three-dimensional excitation-emission matrix(EEM) fluorescence spectroscopy.The sum of the contents of the main DOM components(protein-, fulvic-, and humic-like compounds) increased by 0.6–3.5, 2.5–3.9,and 0.11–0.37 times(P 0.05) when SLR decreased from 1:2 to 1:10, the extraction solution concentration increased from 0.01 to 1.5 mol L~(-1), and extraction time increased from 10 to 300 min, respectively. The three-dimensional EEM fluorescence spectroscopy is a useful tool to characterize the components of DOM and evaluate DOM extraction in soils.     

不同浸提条件对包膜控/缓释肥水中溶出率的影响

以几种不同包膜材料控／缓释肥为供试肥料,研究不同肥(养分)水比、浸提方式(连续浸提和更换浸提液)、温度和pH条件对控／缓释肥水中溶出率的影响。结果表明,浸提液中肥料浓度是影响养分释放的重要因素,加大肥水比、更换浸提液可以显著减小这种影响。升高温度,有机和无机材料包膜控／缓释肥水中溶出率均显著加快。肥料类型、肥水比对浸提液的pH都有显著影响,但在连续浸提和更换浸提液方式下,7d内浸提液的pH有着不同的变化趋势。控／缓释肥在pH.5的磷酸盐缓冲液中的溶出率显著高于在pH.7的磷酸盐缓冲液中的溶出率。因此,对于不同包膜材料控／缓释肥以一定pH值的微酸性缓冲溶液作为浸提剂,定期更换浸提液或采用动态流法,相同的氮(或磷、钾)水比,30℃左右的浸提条件是较为合理的。     

Extraction with 0.01 m CaCl2 underestimates the concentration of phosphorus in the soil solution

The aim of this paper was to compare the concentration of P in soil extracts prepared with water and a ‘soil solution proxy’ (‘SSP’, that is, a salt solution similar in ionic composition and strength to the actual soil solution) with that in 0.01 m CaCl₂ extracts, which is usually taken as a measure of soil P intensity. Seventy widely ranging agricultural soils from the Mediterranean part of Spain were used. Soil/solution ratio was 1:10 and extraction time 3 days. For 0.01 m CaCl₂, a short extraction time of 30 min was also used as the reference method. CaCl₂‐P(3 days) and CaCl₂‐P(30 min) were not significantly different for the 40 noncalcareous soils group, but CaCl₂‐P(3 days) was significantly larger than CaCl₂‐P(30 min) for the 30 calcareous soils group. The Water‐P/CaCl₂‐P(30 min) ratio was not significantly related to any soil property, its mean being 6.3 for the noncalcareous and 5.8 for the calcareous soils group. The mean SSP‐P/CaCl₂‐P(30 min) ratio was 2.6 for the noncalcareous and 3.1 for the calcareous soils group, and decreased slightly with increasing ionic strength of the soil solution in the noncalcareous soils group. These results are consistent with the promoting influence of the Ca ion and ionic strength on P adsorption by permanent‐charge soils. The fact that extraction with 0.01 m CaCl₂ generally results in underestimation of the actual concentration of P in the soil solution should be considered when CaCl₂‐P is used as a soil P test.     

A modified method based on p-nitrophenol assay to quantify hydrolysis activities of lipases in litters

Lipases are glycerol ester hydrolases (EC 3.1.1.3) produced by a wide range of microorganisms. They catalyse the hydrolysis of different esters depending on the water content of the reaction medium. Here, we developed a simple methodology to quantify lipase hydrolysis activities using two different litters: a litter of Quercus pubescens (QP) and a litter of both Q. pubescens and Q. ilex. Different p-nitrophenyl esters were used to test hydrolysis in a reaction medium with an organic solvent (heptane). We showed that these activities depended on the amount of litter, the incubation time and the substrate concentration and that they increased with temperature. Furthermore, the lipases from the studied litters were still active after 2 h at 70 °C. These activities showed common properties of lipases: the highest activities were obtained with a medium-acyl chain substrate, p-nitrophenyl laurate. Moreover abiotic hydrolysis with short-chain acyl substrates was observable. The following parameters are recommended to quantify hydrolysis activities of lipases in litters: 10 mM of p-nitrophenyl laurate in 2 ml of heptane, 1 g of litter, 2 ml of water incubated at 30 °C for 2 h.