Effect of organic matier application and water regimes on the transformation of fertilizer nitrogen in a Philippine soil

Greenhouse experiments using the tracer technique showed that about 20 per cent of the fertilizer nitrogen added as basal to the Maahas clay soil wa11 immobilized in submerged soils to which no organic material was added. The addition of organic matter to the soil increases the amount of nitrogen immobilized and the magnitude depends on the carbon to nitrogen ratio of the materials added. More fertilizer nitrogen waa immobilized in the soils under upland and alternate wet-and-dry conditions than under submerged soil conditions.

The uptake of fertilizer nitrogen by rice plants growing under submerged soil conditions ceased at the vegetative stage of growth because only a small amou11t of available nitrogen remains in the soil at this time, but the rice plant continued to absorb gradually untagged nitrogen from the soil throughout the reproductive etages of growth.

Losses of fertilizer nitrogen were great under the alternate wet-and-dry conditions (submerged-upland). The loss of nitrogen from the soli-plant system was reduced by the addition of dee straw, which also reduced the uptake of fertilizer nitrogen but not the total dry matter production under the experimental conditions. Fertilizer nitrogen immobilized during the first crop remained mostly in the soil throughout the full period of the second crop.

The total nitrogen uptake by rice plants was not affected by the soil moisture tension under the upland conaltlons used in the study but the movement of nitrogen from the leaves to the panicles during the reproductive etage seemed to decrease as the soil moisture tension increased.     

Proton consumption with phosphate adsorption on amorphous fe(iii) hydroxide

Proton consumption with phosphate adsorption on amorphous Fe (III) hydroxide (am-Fe(OH)₃) was compared between two different pH-controlled conditions in a 0.1 mol dm^-3 NaClO₄ solution at initial pH values of 5.50 and 4.50, at 298±0.005 K.

The number of protons caused by phosphate dissociation was subtracted from the total number of protons consumed, then the amount of surface OH groups released by the ligand exchange reaction were determined. When a sequential acid titration by a pH-stat maintained pH values of the systems at initial pH values, the percentage of OH groups released during the ligand exchange reaction was almost constant, 29–37%. When the pH values of the systems increased with phosphate adsorption, the percentage of OH groups released by the ligand exchange reaction varied from -4.3 to 33%. The difference in the proton migration between the two pH-controlled conditions not only depended on the phosphate dissociation, but on the difference in the adsorption mechanism, i.e. the ratio of ligand exchange with OH groups to total phosphate adsorption.     

Quantitative relationship between soil properties and adsorption of dissolved organic matter onto volcanic ash and non-volcanic ash soils

The formation of soil organo-mineral complexes is a key reaction in the carbon cycle in soil, since organic materials acquire a resistance to decomposition due to the formation of the complexes. Adsorption of dissolved organic matter (DOM) onto soil minerals provides a model of this important process. Adsorption of DOM onto samples from Andisols, Inceptisols, and Entisols in batch experiments was compared in terms of the quantitative relationship between the soil properties and the adsorption behavior of DOM. Adsorption behavior was effectively described by a linear initial mass (IM) isotherm, indicating that the adsorption efficiency did not appreciably decline in the range studied even though a large amount of DOM was applied to the soil samples. Samples from Andisols showed a particularly high efficiency of adsorption compared with those from other soils which contained a comparable amount of organic carbon. Explanatory variables useful to predict the efficiency parameter were investigated in 2 steps: firstly the degree of carbon accumulation in the soil samples was examined, and next an index for the amount of ligand exchange sites was examined in combination with the former indices. As a result, an index comprising the total carbon/clay (or total carbon/specific surface area) ratio and the amount of hydroxy ions in the soil extracts with NaF solution was eventually detected. The former represents the degree of carbon occupation on the soil surface, and the latter the amount of ligand exchange sites on labile aluminum. Although the mechanisms involved in the adsorption varied among soils, the selected index was significantly correlated with the adsorption efficiency.     

Adsorption,activity, and kinetics of acid phosphatase as influenced by selected oxides and clay minerals

Abstrac

The effects of 3 oxides (Fe, Al, and Mn oxides) and 3 clay minerals (kaolin, montmorillonite, and allophane) on the adsorption and subsequent kinetic properties of acid phosphatase were compared. The amount of enzyme adsorbed by the oxides and clay minerals followed the order: montmorillonite ? kaolin > Mn oxide > Fe oxide > Al oxide ? allophane. The adsorption isotherms of the enzyme on the oxides and clay minerals, except for montmorillonite and allophane, fitted the Langmuir equation. The activity of the enzyme immobilized by the inorganic components studied was in the order of allophane > kaolin > Fe oxide > montmorillonite > Al oxide ≒ Mn oxide. Compared to the free enzyme, the V _max, K_m, and V _max / K _m values of the immobilized enzyme decreased, increased, and decreased, respectively. Among the oxides or clay minerals, the higher the ability of the inorganic components to adsorb the enzyme, the lower the value of the V _max / K _m ratio of the immobilized enzyme. These findings suggest that the catalytic efficiency of the enzyme complexes formed is determined by the adsorbability of the inorganic components for the enzyme.     

沸石对重金属废水中Cd（NH3）4^2＋的吸附性能研究

利用沸石吸附去除重金属废水中以络离子形态存在的镉,实验考察了沸石用量、振荡时间、pH和温度对吸附效果的影响,探讨了吸附作用机理。结果表明,沸石对Cd(NH3)42 有良好的吸附性能,废水pH、温度和吸附时间是影响吸附效果的主要因素。在Cd(NH3)42 浓度低于50mg·L-1,吸附规律基本符合Freundlich模式,高于50mg·L-1时,不能满足常规吸附规律。     

改性核桃壳生物炭对枯草芽孢杆菌SL-44的吸附

为提高生物炭与微生物吸附能力及其协同改良土壤的性能,使用草酸和氨水对核桃壳生物炭改性,以期制备出性能更加优良的炭基菌剂,并通过红外光谱、动力学、热力学等研究方法,解析生物炭对枯草芽孢杆菌SL-44的吸附机制,并探究其稳定性。结果表明,草酸和氨水改性增加了生物炭在常温下对SL-44的吸附能力,且随着改性剂浓度的增加而增加,最大吸附量为1.5396×10¹¹ CFU·g^-1。此外,通过改性能够在生物炭表面引入COOH、C=O和—NH₂官能团,改变电负性,并保持生物炭原有形貌结构。生物炭对菌体的吸附以物理吸附为主,并涉及化学吸附作用,其表面的—OH、C=O、COOH、—NH₂均参与了吸附反应过程。生物炭吸附SL-44为放热过程(ΔH<0),随着温度的升高炭材料的吸附能力降低,低温更有利于吸附。常温下生物炭的吸附性能为氨水改性>草酸改性>未改性。因此增加生物炭表面氧、氮官能团含量可增加其吸菌量,同时在常温下可制得吸菌量更大的炭基菌剂。测定所得菌剂的活菌数和稳定性发现,被吸附的菌体数越多,其存活菌数量越大,且保藏稳定性越强。与未改性生物炭相比,改性后活菌数最高提高26.01%,而保藏4个月后存活率提高14.1个百分点。     

改性蛇纹石对Pb2+的吸附机理及吸附条件优化

为提升蛇纹石对污染物Pb²⁺的去除效果,实现废水中Pb²⁺的高效去除,本研究将天然蛇纹石矿物高温改性,探究改性后蛇纹石对Pb²⁺的吸附机理、解吸情况及蛇纹石用量、溶液的初始pH、蛇纹石粒径大小和吸附时间对吸附量和Pb²⁺去除率的影响,并通过Box-Behnken响应面法优化改性蛇纹石吸附Pb²⁺的实验条件。结果表明：改性蛇纹石吸附性能明显提升,理论最大饱和吸附容量更高,二者吸附过程均更符合Freundlich等温吸附模型和准二级动力学模型,且吸附过程为自发吸热进行的。改性蛇纹石吸附Pb²⁺的机理主要为蛇纹石裂解产生的Mg²⁺与溶液中溶解的CO₂结合形成MgCO₃,MgCO₃与溶液中的Pb²⁺发生溶积置换生成PbCO₃沉淀;Pb²⁺与改性后蛇纹石表面形成的高能键结合,以Pb（NO₃）₂·Si-O、PbO·O-Si-O配合物的形式吸附在蛇纹石表面。改性蛇纹石在溶液中Pb²⁺的解吸量及解吸率均较低,改性蛇纹石对Pb²⁺的吸附情况较为稳定,Pb²⁺不易被解吸出来。改性蛇纹石对溶液中Pb²⁺最佳吸附条件为固液比为1∶200（m∶V）,pH=5.5,粒径为140目,吸附时间为36 h,此时吸附量及Pb²⁺去除率分别为15.26 mg·g^-1、79.89%。研究表明,改性蛇纹石对Pb²⁺吸附性能明显提升,具有较高吸附容量且吸附较为稳定不易解吸,对去除废水中Pb²⁺具有潜在应用价值。     

一株代尔福特菌的分离及其对Cd吸附机制研究

微生物修复Cd污染技术的关键是获得对Cd具有较高耐性和较强固持能力的菌株,而微生物的修复效果与其对Cd的固持机制密切相关。本研究从重金属污染土壤中分离筛选出一株对Cd吸附率较高的菌株M6,采用批量吸附试验及扫描电镜（SEM）、傅里叶变换-红外光谱（FTIR）、X射线光电子能谱分析（XPS）等技术探究菌株对Cd的固持效果及机理。16S rRNA序列分析结果表明M6与代尔福特菌（Delftia sp.12,登录号KJ191561.1）的同源性达到100%,初步鉴定为代尔福特菌。在pH=7、温度为35℃、培养时间为48 h、初始Cd浓度为10 mg·L^-1时,M6对Cd吸附率最高,达71.8%。Cd浓度在10~100 mg·L^-1时,随着Cd浓度升高,M6对Cd吸附量逐渐增大,最大吸附量为36.73 mg·L^-1。通过测定M6胞内和胞外Cd含量发现,M6对Cd的固持作用包括胞内积累和胞外吸附。SEM扫描发现,吸附Cd后菌体表面出现沉淀物; FTIR结果发现菌体表面多种官能团参与Cd吸附过程。XPS结果表明Cd在菌体表面可能以Cd（OH）₂和CdCO₃形式存在。综上,菌株M6对Cd具有较强的耐性和较佳的固持能力,其固持机制包括胞内积累、胞外吸附和胞外沉淀。     

表面活性剂对北京土壤中甲苯和萘吸附的影响

通过静态吸附实验,研究了北京土壤对阴离子表面活性剂LAS、阳离子表面活性剂CTAB和非离子表面活性剂TX-100以及甲苯和萘的吸附行为,探讨了表面活性剂的性质对甲苯和萘吸附的影响。结果表明,6种土样对甲苯和萘的吸附等温线均很好的符合Freundlich吸附模式,而对LAS、CTAB和TX-100的吸附等温线均较好地符合Langmuir吸附模式,其吸附能力的大小顺序为:轻壤土>轻粘土>中壤土>砂壤土>重壤土>紧砂土。3种表面活性剂在土壤中吸附量的大小顺序为:CTAB>TX-100>LAS。同一土壤中,萘的吸附量大于甲苯的吸附量。CTAB对甲苯和萘的解吸率最高可达27.5%和12.1%,TX-100对甲苯和萘的解吸率最高可达64.3%和48.8%,LAS对甲苯和萘的解吸率最高可达75.4%和56.8%,说明CTAB、TX-100和LAS均利于甲苯和萘在土壤表面的解吸,其解吸效果的大小顺序为:LAS>TX-100>CTAB。     

三唑酮在湘南第四纪红壤上的吸附行为

采用振荡平衡法对三唑酮在湖南第四纪红壤中的吸附行为进行研究,并探讨了吸附时间、浓度、温度、pH等因素对吸附的影响。结果表明,三唑酮在红壤上的吸附分为快速吸附和慢速吸附2个过程。快速吸附基本在8h内完成,当吸附时间延长至24h时,吸附量提高了20%。三唑酮初始浓度越大、吸附时间越长,在红壤上的最大吸附容量也越大;随着温度升高或pH值增大,三唑酮的吸附量降低。