Evaluation of organic matter stabilization in sewage sludge

Abstract

The ratio between non‐humified and humified fractions in pyrophosphate extracts is shown to vary during maturation of sewage sludge. The ratio is higher than 1 in the raw materials but lowers at 1 or less than 1 with the aging of sludge and is assumed to reflect quantitatively the degree of stabilization of organic matter in the sludge. Analytical isoelectrofocusing (IEF) experiments showed that humified fractions in raw sludge focalize only in the pH gradient regions lower than 5.0, whilst in older sludge samples a progressive strengthening of bands occurs in the region between pH 6.5 and 5.0, approaching at least partially IEF patterns of soil organic matter. IEF patterns are suggested to reflect the stabilization of organic matter in sewage sludge from a qualitative point of view.     

Comparative study on effective and ineffective nodules of leguminous plants

It is well known that nitrogen fixation is mainly dependent upon the combination between rhizobial strain and host plant species, though it is also affected by the environmental condition. The site of association between the host and rhizobia is the root nodule. It is, therefore, quite natural that special attention has hitherto been focused on it. A typical symbiotic relationship is going on in effective nodule, while a parasitic relationship prevails in ineffective one. Between such types of nodules there must be some differences with respect to the inner structure as well as the metabolism in them. Experiments were made to compare the morphological change of rhizobia, the amount and distribution of starch, the kinds of free amino acids in effective nodule with those in ineffective one. To obtain materials, soybean, pea, red clover, and genge (Astragalus sinicus L.) Were used with their own effective and ineffective strains of rhizobia, respectively.     

Influence of afforestation on soil genesis,morphology and properties in glacial till deposits

A study of soil morphological, physical and chemical properties was performed in woodland of different ages, in which spruce (Picea abies), aspen (Populus tremula) and birch (Betula pendula) growing stocks have colonized former agricultural land. The aim of the study was to clarify changes in soil genesis, morphology and properties due to the afforestation of abandoned agricultural land in glacial till deposits. The research showed that soil in these deposits (loamy sand, loam, clay) retains the morphological properties of agricultural land for up to 100 years. Secondary podzolization features in the soil profiles were observed within 100 years of the start of afforestation, whereas the diagnostic properties of Albic and Spodic horizons had not developed in the soil profile after 200 years. This study demonstrated that the morphological and physico-chemical properties of forest litter horizons, including the accumulation of organic substances, are dependent on forest age; however, changes in the properties of mineral soil horizons are mainly related to woodland age. Following the afforestation of agricultural lands, changes in soil pH_KCl, organic matter content and extractable Al and Fe concentrations occur more rapidly than changes in soil diagnostic properties and profile formation.     

The impacts of oxytetracycline on humification during manure composting can be alleviated by adjusting initial moisture contents as illustrated by NMR

Oxytetracycline(OTC) residues have been found in soil and water, and they may pose potential risks to agricultural ecological environments. One of the most impactful ways for OTC to enter the soil and water environments is through excrement used as organic fertilizer. Therefore, it is important to remove OTC during manure composting and to understand the transformation of the organic materials during composting in the presence of OTC. In the present paper, chicken manure and wheat sawdust spiked with OTC were composted under different initial moisture contents(MC) to evaluate the degradation of OTC and changes of organic matter during the composting process. The MC has a significant effect on OTC degradation during composting. A higher MC of 65% was more conducive to OTC degradation(77.4%) and compost maturity compared to the lower MC. However, the higher MC of 65% could increase the ammonia volatilization by promoting nitrification compared to the lower MC. An increase in the initial MC could improve the composting temperature. NMR results illustrated that the presence of OTC could affect the internal transformation of aliphatics, and OTC inhibited compost humification. Thus, an initial MC of 55–65% can alleviate the impacts of OTC on humification during manure composting.     

Spectroscopic Characteristics and Biodegradability of Cold and Hot Water–Extractable Soil Organic Matter under Different Land Uses in Subarctic Alaska

Cold (22 ^oC) and hot water (80 ^oC) extractions have been used to estimate labile organic carbon (C) and nitrogen (N) in soils. Sequentially extracted cold and hot water organic matter (WEOM) from 14 Alaskan soils under different land uses were characterized by ultraviolet and fluorescence spectroscopies. Compared to cold WEOM, the ultraviolet (UV) absorptivity at 254 nm and fluorescence index were significantly (P < 0.05) decreased in hot WEOM of all soils. The biodegradability, assessed in a 21-d solution incubation, of hot WEOC and WEON was significantly (P < 0.05) greater than that of cold WEOC and WEON in all soils. The biodegradability of cold or hot WEOC was correlated with the protein-like component, indicating that a protein-like fluorophore is a labile fraction in both cold and hot WEOM pools. Information derived from this work contributed to better understanding of subarctic soil WEOM properties and their biodegradability.     

农林废弃物对厨余垃圾堆肥腐殖化的影响与微生物驱动机制

高碳源农林辅料复配是实现厨余垃圾好氧堆肥促腐提质的关键技术,但不同辅料对厨余垃圾堆肥过程腐殖化的影响及其相应的微生物驱动机制仍不清楚,从而限制了对辅料的有效筛选与利用。为此,该研究选用园林废弃物、玉米秸秆和西瓜秧3种典型高碳源农林废弃物为辅料,探究其对厨余垃圾堆肥过程有机质腐殖化的调控效果与机制。研究结果表明：相较于园林废弃物和西瓜秧,添加15%玉米秸秆（湿质量）作为辅料,能够有效调节堆体物料结构,富集功能微生物,促进厨余垃圾堆肥产物腐熟度提升,种子发芽指数可达139%。具体而言,西瓜秧蛋白质含量较高,作为辅料能够在堆肥初期促进堆体快速升温,但不利于高温期延续,且产物腐殖化程度较低。相比之下,园林废弃物和玉米秸秆添加可以在高温期和降温腐熟期富集更多Ureibacillus、Bacillus Oceanobacillus和Flavobacterium等具有木聚糖降解和纤维素降解功能的细菌,促进有机质转化为多酚、氨基酸等腐殖质前驱物,进而推动稳定的腐殖酸生成。特别是玉米秸秆作为辅料时有效增加了具有木质纤维素降解功能的细菌,从而能够加速有机质的降解,促进腐殖化提升75%,研究结果为选取适宜的辅料强化厨余垃圾堆肥产品品质提供参考。     

横跨中国崇明岛河岸湿地缓冲区土壤中溶解性有机碳的空间分布及其荧光特征

The migration of soil dissolved organic carbon(DOC) from terrestrial to aquatic environments has important impacts on the adjacent water quality and the transport of organic and inorganic contaminants.However,few studies have investigated the sources and properties of DOC in riparian zones.A total of 34 soil samples were collected across four riparian buffer zones(Zones A-D) on Chongming Island,China.The vertical distributions of soil organic carbon(SOC) and DOC,fluorescence excitation-emission matrix(EEM) spectra of DOC and the optical indices,including fluorescence index(FI),index of recent autochthonous contribution(BIX),and humification index(HIX),were measured across the riparian environment to investigate the sources and fluorescence properties of DOC.The results showed that SOC stored in the surface soil(0-30 cm) accounted for 40%of the total soil profile SOC.The DOC accumulated in Zones A-C,which accounted for 5%of the SOC.The fluorescence EEM spectra of DOC showed that DOC contained humic-like and protein-like substances,which were mainly derived from recent plant debris by microbes.A large amount of humic-like substances were sorbed to minerals in the surface soil(0-30 cm).In addition,the riparian topography and soil physico-chemical properties(pH,EC and moisture) dictated the transformation and transport of DOC.The results suggested that EEMs could reveal the source of DOC in riparian soil systems,and that optical indices were complementary tools that revealed the characteristics of soil DOC and provided supplemental evidence about DOC sources.     

添加沼渣对餐厨垃圾堆肥腐殖化过程的影响

为探讨添加沼渣对餐厨垃圾堆肥腐殖化过程的影响,设计餐厨垃圾∶沼渣的干基比例分别为4∶0 （T1）、3∶1 （T2）和1∶3 （T3）3个处理,以水稻秸秆作为辅料进行条垛式堆肥。通过测定堆体温度、干物质含量、种子发芽指数以及总氮、总有机碳、胡敏酸和富里酸含量,分析堆体的物料降解、腐殖化程度、碳氮损失和堆肥品质等。结果表明：随着沼渣比例的增加,堆肥的有效积温比、腐殖质聚合度、腐殖化指数均上升; 50 d完成堆肥时,T2处理具有最高的干物质降解率（37.16%）、氮含量（23.89 g·kg^-1）和种子发芽指数（90.59%）,并具有较高的有效积温比（63.73%）、腐殖质聚合度（0.84）和腐殖化指数（7.78%）。研究发现,添加沼渣提高了餐厨垃圾堆肥高温期发酵效率,强化了堆肥腐殖化作用,同时也增加了碳、氮损失。     

Humification indices of water‐soluble fulvic acids derived from synchronous fluorescence spectra — effects of spectrometer type and concentration

The high variability of dissolved organic matter (DOM) in natural systems (concentration, composition) means rapid methods are required for its characterization so that a high number of samples can be analyzed. The objective of the present study was to quantify the effects of spectrometer type and dissolved organic carbon (DOC) concentration on the humification indices of water‐soluble fulvic acids (FAs) derived from synchronous fluorescence spectra, and thus enable the broader application of this method for DOM characterization. We used three standard FAs from the International Humic Substances Society, 24 water‐soluble FAs isolated from topsoil, groundwater and surface water in a fen area, and two different spectrometers. The wavelengths at which bands occurred were similar for all the FAs. Therefore, the differences between the spectra of the FAs studied could be described by humification indices (band ratios). The humification indices calculated correlated very well between spectrometers despite small differences in the wavelengths of bands and shoulders. The absolute values of these indices deduced from two spectrometers can only be directly compared if the spectra are corrected using a standard substance. Increasing DOC concentration resulted in a linear increase in humification indices with a sample specific slope. Therefore, we recommend using an uniformly low DOC concentration of about 10 mg C l^—1 for recording the spectra of samples with typically low DOC concentrations (aquatic samples, soil solutions). This value is a compromise between relatively low absorption to minimize inner filter effects and a sufficient signal‐to‐noise ratio.