分光光度法测定土壤有机质的含量

建立了以K2Cr2O7测定土壤中有机质的分光光度法。在硫酸溶液中,以Ag2SO4为催化剂,加入过量K2Cr2O7标准溶液氧化葡萄糖中的有机碳,铬(Ⅵ)可用有机碳还原至铬(Ⅲ),其最大吸收波长为585 nm。有机碳浓度在1.60～68.00 mg/L范围内与溶液吸光度呈良好线性关系,线性回归方程为A=0.409ρ-0.067 93(mg/L),相关系数r=0.999 5,检出限为0.190 mg/L,相对标准偏差(RSD)为0.7%,表观摩尔吸光系数ε=4.91×103L/(mol.cm)。测定国家标准土壤样品中有机质的含量,相对误差小于4.3%。     

赶酸仪外加热测定土壤中有机质含量

以Ag_2SO_4为催化剂,在硫酸、重铬酸钾溶液中,采用赶酸仪外加热消煮促进有机质氧化分解,并计算土壤有机质的含量。方法检出限为0.102g/kg,检出下限为0.410g/kg。对国家标准物质GBWO7459,GBW07460,GBW7461,GBWO7414a分析验证,测定分析结果与标准值吻合。操作简便快捷,准确性高,满足土壤样品中有机质的测定,适用于批量土壤样品测定。     

Influence of lime, fertilizer and manure applications on soil organic matter content and soil physical conditions: a review

The effects of lime, fertilizer and manure applications on soil organic matter status and soil physical properties are of importance to agricultural sustainability. Their effects are complex and many interactions can occur. In the short-term, liming can result in dispersion of clay colloids and formation of surface crusts. As pH is increased the surface negative charge on clay colloids increases and repulsive forces between particles dominate. However, at higher lime rates, Ca²⁺ concentrations and ionic strength in soil solution increase causing compression of the electrical double layer and renewed flocculation. When present in sufficient quantities, both lime and hydroxy-Al polymers formed by precipitation of exchangeable Al, can act as cementing agents bonding soil particles together and improving soil structure. Liming often causes a temporary flush of soil microbial activity but the effect of this on soil aggregation is unclear. It is suggested that, in the long-term, liming will increase crop yields, organic matter returns, soil organic matter content and thus soil aggregation. There is a need to study these relationships on existing long-term liming trials.Fertilizers are applied to soils in order to maintain or improve crop yields. In the long-term, increased crop yields and organic matter returns with regular fertilizer applications result in a higher soil organic matter content and biological activity being attained than where no fertilizers are applied. As a result, long-term fertilizer applications have been reported, in a number of cases, to cause increases in water stable aggregation, porosity, infiltration capacity and hydraulic conductivity and decreases in bulk density. Fertilizer additions can also have physico-chemical effects which influence soil aggregation. Phosphatic fertilizers and phosphoric acid can favour aggregation by the formation of Al or Ca phosphate binding agents whilst where fertilizer NH₄ ⁺ accumulates in the soil at high concentrations, dispersion of clay colloids can be favoured.Additions of organic manures result in increased soil organic matter content. Many reports have shown that this results in increased water holding capacity, porosity, infiltration capacity, hydraulic conductivity and water stable aggregation and decreased bulk density and surface crusting. Problems associated with large applications of manure include dispersion caused by accumulated K⁺, Na⁺ and NH₄ ⁺ in the soil and production of water-repellant substances by decomposer fungi.     

Preserving tropical soil organic matter at watershed level. A possible contribution of urban organic wastes

The goal of this paper is to put the issue of preserving Soil Organic Matter (SOM) into a regional, urban-rural, context. In doing so, we apply the method of material flux analysis to a watershed in Boyacá in Colombia. We estimate the order of magnitude of the dry organic matter and carbon fluxes between the rural and urban parts of the region, including estimates on biomass growth, tillage, organic waste, and sewage. These estimates are used to derive potentials for carbon cycling between rural and urban areas. It is shown that (i) for the municipality of Tunja, the treated organic wastes produced in the urban area could add about 30% to the current carbon input into arable soils; (ii) to preserve the organic carbon content in soils in Tunja over the long-term, either, erosion control measures have to be implemented and/or the total treated urban organic wastes have to be concentrated on about 1/5 of the agricultural area. However, such an attempt has to consider the possible trade off between allocation needs (poor farmers on the hillside) and allocation costs (transportation and distribution costs). This revised version was published online in June 2006 with corrections to the Cover Date.     

Social, economic and policy dimensions of soil organic matter management in sub-Sahara Africa: challenges and opportunities

In recent years and in some situations the status of soil organic matter (SOM) has deteriorated considerably due to long periods of continuous cultivation and limited external inputs in the form of mineral fertilizers. Deterioration of SOM varies by agro-ecological zones, by soil types and by cropping patterns. It is more intense in East Africa, followed by coastal West Africa and Southern Africa and least intensive in the Sahel and Central Africa. It is also more serious in areas under low-input agriculture irrespective of the prevailing cropping system. The major consequence of the decrease in SOM in the tropics is lower agricultural productivity with a direct negative effect on food security. While biophysical dynamics of SOM have been extensively covered in the literature, social considerations have not received similar attention. This paper examines the social, economic and policy factors associated with the management of tropical soil organic matter. Empirical data from a range of environments in Africa show that SOM improvement options yield a positive return to land as well as labour. However, there are a number of constraints. Social constraints are related to the large quantities of organic matter that are required (case of farmyard manure), the competitive uses for the material (case of crop residues), land and labour requirements, and gender-related issues. From a policy stand point, unsecured tenure rights together with price distortions and other market failures may be important constraints. Challenges for sustainable management of SOM are identified. These include management conflicts, land tenure arrangements, the divergence in goals between individuals and society, land and labour requirements, inadequate support systems for land users, profitability issues, the role of subsidies, and the absence of national action plans. A number of opportunities are identified that could enhance the improvement or maintenance of SOM. These include: exploring the need and potential role of community-based SOM management practices; development of an integrated plant nutrient management strategy involving both organic and inorganic inputs; and development of concrete national action plans. It is argued that because externalities of SOM improvement or maintenance extend beyond the farmer's fields, SOM investment may require cost sharing between individuals and the society. Policies on subsidies need to be reconsidered. Research priorities are identified that require closer collaboration between scientists from a variety of disciplines. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of organic matter on the physical and the physicochemical properties of an illitic soil

The main thrust of this study is to investigate the effects of organic matter on the physical and the physicochemical properties of illitic soils. For this purpose, organic matter (peat) was added to inorganic illitic clayey soil at eight levels (0%, 5%, 10%, 12.5%, 15%, 17.5%, 20%, and 30% by weight). The physicochemical properties of the resulting soils were determined using a Grain Size Analyzer (GSA) with specific surface area measurement, Scanning Electron Microscopy (SEM), and Infrared Spectroscopy (IR). The physical properties of the mixtures were determined by conducting a series of laboratory tests including Atterberg limits, compaction, unconfined compressive strength, and swell characteristics tests. The results showed that at low organic contents (in general less than 15%) the soil particles tend to aggregate, whereas at higher organic contents the soil particles tend to disperse. Also, the IR tests showed that direct chemical interactions took place between the organic and the inorganic fractions of the mixtures. The tests on the physical properties showed that at low organic content (up to 10%) the plasticity index slightly increased then after, the plasticity index decreased with increasing organic content. Organic matter has shown to decrease the maximum dry density and increase the optimum water content, nevertheless, although organic matter decreased the soil's compactability, the feasibility of compaction of slightly organic content soils still exists. Moreover, it was shown that organic matter decreased the peak strength values and increased the water contents at these peak strengths. The final free swell for illitic soils increased with increasing levels of added organic matter.     

The role of soil microorganisms in soil organic matter conservation in the tropics

Soil is a large sink for organic carbon within the terrestrial biosphere. Practices which cause a decline in soil organic matter cause CO₂ release, in addition to damaging soil resilience and, often, agricultural productivity. The soil micro-organisms (collectively the soil microbial biomass) are the agents of transformation of soil organic matter, nutrients and of most key soil processes. Their activities are much influenced by soil physico-chemical and ecological interactions. This paper addresses two key issues. Firstly, ways of managing, and the extent to which it is possible to manage, soil biological functions. Secondly, the methodologies currently available for studying soil micro-organisms, and the functions they mediate, are discussed. It is concluded that, as the world population develops in this new millennium, there will be an increased dependence upon biological processes in soil to provide adequate crop nutrition for the majority of the world's farmers. Although a major increase in the use of artificial fertilisers will be necessary on a global scale, this will not be an option for large numbers of farmers due to their poverty. Instead they will rely on recycling of nutrients from animal and vegetable composts and urban wastes, and biological cycling from nitrogen fixation and mycorrhizae. The challenge is to select the most appropriate topics for further research. Not all aspects are likely to lead to significantly improved agricultural productivity, or sustainability within the foreseeable future. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of leather meal fertilizer on soil organic matter: A laboratory study

Leather meal fertilizer was mixed with a soil (Typic Xerorthent) and incubated in the laboratory for one year at room temperature. Soil samples were collected periodically and analyzed in order to follow the transformation of the organic matter as well as the availability of Cr and certain plant nutrients.The results obtained showed intense mineralization during the first 60–120 days of the incubation period. The amount of humic acids (HAs) separated from the alkaline extracts showed that the humification level increased markedly after the first 60 days of incubation and, as shown by IEF analysis, organic compounds similar to the soil humic substances were formed.Variations in the amount of available nutrients were observed; only the extractable Cr increased during the first period of mineralization.     

Simulation of nitrogen in soil and winter wheat crops: Modelling nitrogen turnover through organic matter

A computer model is described that simulates leaching, organic matter turnover and nitrogen uptake by a winter wheat crop. The model is assessed against a data set from the Netherlands where winter wheat was grown in two seasons (1982–3 and 1983–4) on three different soils in two different parts of the country. The model satisfactorily simulated the growth, N uptake and production of grain. It also simulated the dynamics of indigenous soil N well but it did not always account for the fate of applied fertilizer N. Some possible reasons for this and ways of improving the model are discussed.     

Farmer's view on soil organic matter depletion and its management in Bangladesh

Bangladesh is an agricultural country. About 80% of the total population live in rural areas. The contribution of agriculture to the gross domestic product is 30%. Rice is the major food crop while jute, sugarcane and tea are the main cash crops. Other important crops are wheat, tobacco, pulses, vegetables and fruits. Overall productivity in Bangladesh is stagnating or declining. The implication of yield stagnation or declining productivity is severe, since these trends have occurred despite rapid growth in the use of chemical fertilisers. Depletion of soil organic matter is the main cause of low productivity, which is considered one of the most serious threats to the sustainability of agriculture in Bangladesh. In Bangladesh, most soils have less than 17 g/kg and some soils have less than 10 g/kg organic matter. Farmers realise that there is a problem with soil fertility related to organic matter depletion. Farmers say that organic matter increases yield, reduces the production cost, improves crop growth and the economy, increases water-holding capacity and improves the soil structure. They recognise soil with higher organic matter content by darker brownish to black in colour. Some farmers are using fast-growing trees such as Flemingia macrophyla, Ipilipil (Leucaen leucophala), Glyricidia sepium, Boga Medula (Tephrosia candida), Dhol Kolmi (Ipomoea fistulosa), etc., as living fences, which can be used as fuel, fertiliser and fodder. To increase the soil organic matter, farmers use green manure crops, compost, quick compost, cow dung, azolla, etc. However, fuel for cooking purposes is limited and cow dung and crop residues are largely used as fuel. Crop residues are also used as fodder for livestock. Farmers expressed the wish to learn more about organic fertilizer management. However, sufficient food should be produced to keep pace with population growth. To alleviate the hunger and poverty is to increase the intensity of agricultural production and maintain favorable ecological conditions. Therefore, more organic matter should be used in the farmers' fields to sustain the soil fertility in an intensive farming system. This revised version was published online in June 2006 with corrections to the Cover Date.     

Characterization of anion exchange membranes with natural organic matter (NOM) during electrodialysis

Natural organic matter (NOM) is thought to be a major source of fouling during membrane filtration of natural waters. The organic matter present in surface waters was characterized in terms of its molecular weight distribution, acidity and electrokinetic properties. The fouling potentials of anion exchange membranes were predicted by the characterization. Changes in the physicochemical properties of anion exchange membranes were also examined during electrodialysis (ED) process of solutions containing NOM. The ED performances were evaluated for the three anion exchange membranes (AMX, AM-1 and ACM) in the presence of NOM. Fouling phenomena in terms of current efficiency and NaCl flux were in good agreement with the fouling potentials predicted by the characterization results. Observations of the molecular weight distribution and the constituents of NOM revealed that the hydrophobic NOM fraction with high molecular weights deposited mainly on the membrane surface, providing fouling effects on the anion exchange membrane.     

Problems with and local solutions for organic matter management in Vietnam

Soil organic matter plays a major role in sustainable agricultural development in Vietnam. A general soil evaluation shows that the content of organic matter in most soil units in Vietnam ranges between 0.5 to 3.0% soil organic matter (in the A and B horizon only) with lower levels especially on sloping land. Most upland soils (70% that contain ≤ 2% soil organic matter) are in danger due to imminent soil erosion. Soil organic matter is lost very quickly due to erosion, lack of organic manure and poor farming techniques in these areas. Using green hedgerows along contour lines and intercropping with legume species to cover the soil are technological options to control soil erosion and improve soil organic matter content on sloping land. Green hedgerows significantly reduce soil and organic matter loss by 50–70%, compared to sloping land without hedgerows. Intercropping with legume species reduces soil loss by 40–50%, and can provide the soil with 2.5–12 tons of green manure/ha/year. However, more studies are needed to identify the best technologies for managing soil organic matter in upland areas. This revised version was published online in June 2006 with corrections to the Cover Date.     

Assessing nitrogen mineralization from soil organic matter using anion exchange membranes

A simple method to assess differences in potential contribution of organic nitrogen mineralization to plant available N among soils may be useful in fertility research as well as routine soil testing. We deployed a method to assess mineralizable soil organic N using anion exchange membrane (AEM) burial. The method is based on a simple closed incubation system in which strips of AEM are buried directly in soil to adsorb NO ₃ ^- released from organic matter. An index of mineralization was obtained using the amount of NO ₃ ^- adsorbed on an AEM strip removed at the end of each incubation. The same incubation system but using 0.001M CaCl₂ solution to extract NO_3-N was used as the reference method. The mineralization indices obtained from both methods were compared with each other and with plant uptake. A total of 74 soils from across Saskatchewan were used in the study to provide a range of soil properties. Correlations between test values and N uptake by plants in two separate experiments showed the 2 week AEM incubation to be more closely correlated with plant N uptake (r² = 0.86^**** and 0.57^****, respectively) than the reference method (r² = 0.60^**** and 0.48^****, respectively).With this method, we were able to determine the influence of different tillage systems and landscape positions on mineralizable N. The results showed that the NO ₃ ^- released from soil organic matter and accumulated on the AEM reflected the expected effect of three different tillage systems and two landscape positions on mineralizable N. Cropping systems with continuous alfalfa (Medicago sativa) showed higher N release from soil organic matter than a canola (Brassica napus)-lentil (Lens culinaris)-barley (Hordeum vulgare) rotation did. Higher N mineralization was found in the lower slope positions of the landscape where organic matter contents are highest. Direct burial of AEM appears to be a simple and effective method of including a measure of N mineralization in a soil test.     

Review: materials and modelling for organic photovoltaic devices

This review gives a simple and pedagogical introduction to the field of materials and their modelling for the active layer in organic photovoltaic devices. It gives a perspective on past work and a summary of the current state of the art. Given the extremely fast changes on-going in this field, it is hoped that this contribution will serve as both a timely snapshot and a pedagogical entry point to this fascinating subject. Furthermore, an example is given of how modelling can enhance the understanding of the structures and qualities of materials using a leading low-bandgap polymer donor and non-fullerene acceptor pair (PM6 and Y6). © 2021 Society of Industrial Chemistry.     

The analysis of organic matter in coke oven emissions

A detailed analysis of coke oven emissions is reported. Measurements were made on samples collected at various workplace locations on the oven top. A new type of sampling system was used and is described. Results range from volatile monoaromatic compounds including benzene to polycyclic aromatic hydrocarbons (PAH) of six fused rings. Estimates of errors which may arise when sampling for PAH by filtration are given.     

Management of soil organic matter in semiarid Africa for annual cropping systems

Ensuring sustainable agriculture in semiarid Africa requires the implementation of methods to balance nutrients and to conserve soil organic matter (SOM). There is an urgent need to improve the management of all types of SOM input. In this paper; the authors review a wide range of agricultural practices and discuss their advantages, limitations and feasibility. They distinguish ‘traditional systems’ such as traditional fallow, parkland and manuring from ‘improved systems’ such as ‘improved fallow’, forest fallow, alley cropping, cover crops and application of composted manure. Biomass production (BMP) for ‘improved systems’ is mainly linked: (i) for agroforestry, to the tree species used in forest fallow, to the synchronization of nutrient supply by the soil with the cereal demand in alley cropping, and generally to the efficiency of the root system and its development with the depth; (ii) for cover crops, BMP is mainly linked to the initial soil fertility and to the ecological zone: establishment and management of cover crops are not yet fully mastered under some conditions such as an annual rainfall below 800 mm and/or on very clayey soils; (iii) for manure, BMP is mainly linked to the improvement of fallow in order to ensure sufficient forage resources. Because semiarid Africa is mainly a livestock zone, the authors emphasise manure: constraints, quality indicators and tools used to encourage its production, are analysed. Thus it was concluded that the intensification of manure production and its rational use in semiarid African regions, threatened by drought and malnutrition, is very important: this cannot be separated from the production of plant biomass, whose possibilities have been examined above. This revised version was published online in June 2006 with corrections to the Cover Date.     

Comparison of ceramic and polymeric membranes for natural organic matter (NOM) removal

Ceramic membranes were compared with polymeric membranes with respect to natural organic matter (NOM) removal using two removal mechanisms (i.e., size exclusion and charge repulsion). NOM properties including molecular weight and molecular structure, at different charge densities, were examined, along with membrane characteristics, including molecular weight cut-off (MWCO) and surface charge. Integrated analyses of both NOM and membrane characteristics provided information for membrane evaluation of different membrane materials and configurations (i.e., tubular vs. flat sheet type). A ceramic tight-ultrafiltration (UF) membrane showed the same potential as a similar nanofiltration (NF) polymeric membrane, in terms of the minimization of haloacetic acid (HAA) formation. Moreover, a ceramic OF membrane with a MWCO of 8000 Daltons showed almost the same behavior as an equitable polymeric UF membrane with a MW CO of 8000 Daltons in terms of NOM removal.     

Evaluation of fly‐ash additive for removal of dissolved organic matter during soil aquifer treatment of wastewater treatment plant Peffluent

BACKGROUND: Fly‐ash (FA) additive was evaluated for enhanced removal of organic matter during soil aquifer treatment (SAT) of a wastewater treatment plant (WWTP) effluent in five 0.50 m length columns (diameter 0.1 m) in parallel. RESULTS: The characteristic behavior of dissolved organic matter (DOM) was examined for the stratum matrix configurations of both natural soil and a mixture of soil and FA. Incubation and fractionation experiments indicated that FA additive within the SAT columns would enhance the bulk adsorption of hydrophobic fractions, but decrease the biodegradation of the hydrophilic fraction simultaneously. The configuration design of an upper 0.25 m soil layer and a mixture of FA and soil underneath could make use of the functions of both FA adsorption and biodegradation within soil, which could lead to a further fractional removal of dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP). Moreover, FA additive in the SAT columns could result in a significant decrease of tryptophan‐like aromatic proteins and fulvic‐like components (C?C and C?O related), while the setting of the top 25 cm soil layer would lead to a further reduction of oxygen‐containing functional groups. CONCLUSIONS: Based on the results, FA might serve as a supplementary material for enhancing the reduction of DOM during SAT operation. Copyright © 2010 Society of Chemical Industry     

ASI法测定土壤有机质与国标法的相关性研究

对ASI法与GB9834—88测定土壤有机质的结果进行了相关性比较。结果表明,全部样本的ASI法与GB9834-88分析方法的有机质之间存在极显著正相关,相关方程为Y=0．9348x＋0．018（R^2=0．9737＊＊）,两种方法最大相对偏差仅为1.4％。由于ASI方法具有简便、快速和准确的特点,同时减少了铬的污染,是一种较好的土壤有机质测定方法,