Microbial, chemical and physical aspects of citrus waste composting.

Citrus waste supplemented with calcium hydroxide and with a C/N ratio of 24:1, pH of 6.3 and moisture content of 60% was composted by piling under shelter. With regular turning over of the pile and replenishment of moisture, the thermic phase lasted for 65-70 days and composting was completed after 3 months. Compost thus prepared had an air-filled porosity of 14%, water-holding capacity of 590 ml l(-1), bulk density of 1.05 g cm(-3) and conductivity of 480 mS m(-1). Phosphorus content (in mg l(-1)) was 15, potassium 1,170, calcium 362, magnesium 121, sodium 32, chloride 143, boron 0.31, and water-soluble nitrogen and organic matter 126 and 4788, respectively. Total carbon amounted to 8.85% and total nitrogen to 1.26% of the dry weight, giving a C/N ratio of 7. Mature compost showed some, but acceptable, levels of phytotoxicity. Raw citrus waste was predominantly colonised by mesophilic yeasts. Thermophilous microorganisms present during the thermic phase mainly comprised the bacterial species Bacillus licheniformis, B. macerans and B. stearothermophilus and, to a lesser extent, fungi such as Absidia corymbifera, Aspergillus fumigatus, Emericella nidulans, Penicillium diversum, Paecilomyces variotii, Rhizomucor pusillus, Talaromyces thermophilus and Thermomyces lanuginosus. Bacteria prevalent in the final product included B. licheniformis, B. macerans, Proteus vulgaris, Pseudomonas aeruginosa, P. fluorescens, P. luteola and Serratia marcescens, whereas fungi isolated most frequently comprised Aspergillus puniceus, A. ustus, E. nidulans. Paecilomyces lilacinus, T lanuginosus, yeasts and a basidiomycetous species, probably Coprinus lagopus.     

Air sampling methods for VOCs related to field-scale biosecure swine mortality composting

Monitoring specific volatile organic compounds (VOCs) as markers of biosecure carcass degradation is a promising method to test progress and completion of the composting process. The objective of this study was to test the feasibility of using existing aeration ducts in composting units as practical sampling locations. The secondary objective was to test the feasibility of using marker VOC concentrations in aeration ducts to elucidate information about airflow patterns inside composting units. Marker VOC concentrations were significantly higher in the upper aeration duct and this duct can typically be used to collect air samples instead of placing special air sampling probes inside the composting units. Occasionally, the airflow direction inside composting units can change. Marker VOC concentrations can be used to decide the airflow direction inside the composting units. In this study, higher VOC concentrations were measured from the upper aeration duct, and this duct was shown to be an outlet.     

Effect of initial physical characteristics on sludge compost performance

To develop an active microbial activity quickly developing stabilizing thermophilic temperatures during the composting of wastewater sludge, the bulking agent (BA) plays a major role in establishing the recipe structure, exposed particle surface area and porosity. To optimize the biodegradation of a sludge compost recipe, the objective of this paper was to study the effect and interaction of initial moisture content (MC) and BA particle size distribution. Three 300 L insulated laboratory composters were used to treat two series of ten (10) recipes with different combinations of MC and BA particle size distribution. Using a to wastewater sludge to BA dry mass ratio of 1/6, the ten (10) recipes were repeated using two BA, residues recycled from a commercial sludge composting plant and crushed wood pallets. Each four week trial monitored O₂ uptake, temperature, compost consolidation and airflow distribution. The Central Composite Factor Design method produced a model from the results estimating the impact of a wider range of MC and BA particles size distribution. The MC directly affected the total O₂ uptake and therefore, organic matter biodegradation. The BA particle size distribution influenced compost consolidation with a MC crossed effect. Both BA particle size distribution and MC influenced compost airflow dispersion. Composting was optimized using the BA consisting of recycled green waste residues with particle size of 20–30 mm and a 55% MC. The predictive models suggested the need for further optimization of sludge and wood residue composting recipe.     

Co-composting solid swine manure with pine sawdust as organic substrate

The main objectives of this work were to investigate the evolution of the principal physicochemical properties, i.e., bulk temperature, pH, electrical conductivity (EC), moisture content, total organic matter, total nitrogen and total phosphorus, in co-composting pine sawdust with increasing percentages of fresh solid swine manure, and thus to evaluate the most desirable manure proportion for producing organic substrates in consideration of the quality of the resulted compost. The composting was in four identical 100.5l lab vessels, using 5% each tea leaves and herb residues as conditioners. The swine manure was added in the trials at 20%, 30%, 40%, respectively, and was substituted in the control with 30% lake sludge corrected by 0.5% urea. The initial humidity of each treatment was 60+/-2%. While being aerated actively at approximately 0.3m(3)/min at intervals of 10 min/h, the mixture was composted for 29 days. The results indicated that N and P decomposition primarily occurred in the mesophilic phase, while organic carbon decomposed in the thermophilic phase and 30% swine manure with initial C/N ratio of about 40 was more desirable for composting organic substrates.     

Biofilter performance of pine nuggets and lava rock as media

Wood chips and bark mulch are commonly used biofilter media because they are generally locally available and inexpensive. Nevertheless, these organic materials degrade and require replacement every 2-5 years. In this study, airflow characteristics and gas reduction efficiencies of two alternative biofilter media (pine nuggets and lava rock) with high porosity and potentially longer service lives were evaluated at three empty bed contact times (1, 3, and 5 s) and two moisture levels (82% and 90% relative humidity). The lava rock had a lower pressure drop across the media and maintained higher media depth. Gas reduction efficiencies were highest for lava rock at 5 s empty bed contact time and 90% humidity. The reduction efficiencies at these conditions were 56%, 88%, 87%, 25%, and 0.7% for ammonia, hydrogen sulfide, total reduced sulfur, methane and nitrous oxide, respectively. Odor reduction up to 48% was observed but was not consistent.     

耕层调控与有机肥处理下麦田土壤和小麦冠层结构特性及其相互关系

本研究基于5年的耕作定位试验,设置深耕(DT)、深耕有机肥(DTF)、浅耕(ST)、浅耕有机肥(STF)、免耕(NT)和免耕有机肥(NTF)处理,以期通过改良耕层土壤结构,优化小麦冠层结构特性.结果表明: 同一耕作处理下,增施有机肥可降低土壤容重、提高土壤孔隙度,提高20～40 cm土层2～5和0.25～2 mm粒级土壤团聚体含量,降低>5 mm粒级团聚体含量、>0.25 mm粒级团聚体的平均质量直径(MWD)和几何平均直径(GMD).与其他处理相比,NTF处理改善了0～20 cm土层土壤容重、增加土壤孔隙度;DTF处理降低了40～60 cm土壤容重和>0.25 mm粒级机械团聚体的稳定性,增加了土壤透气性.花后各时期,有机肥处理的叶片角度指数降低,叶面积指数(LAI)和旗叶净光合速率(P_n)提高.STF处理的角度指数最低,DTF处理的P_n最高,显著大于其他处理.通径分析表明,自变量容重、孔隙度、>0.25 mm粒级团聚体的数量(R_0.25)和MWD对因变量角度指数、LAI和P_n的直接通径系数均达到极显著水平.0～20 cm土层,MWD值增大有利于P_n和LAI的提高;20～40 cm土层,土壤容重在一定范围内的增加可优化叶夹角,提高冠层透光率;40～60 cm土层,高的土壤容重和低的孔隙度限制了LAI和P_n的增加.综上,豫中补灌区增施有机肥下的深耕或浅耕处理有利于改良土壤结构、增加土壤通透性,优化冠层结构,提高冠层受光率、叶面积指数和光合速率.     

玛纳斯河流域扇缘带不同植被类型下土壤物理性质

对生长在玛纳斯河流域扇缘带上的柽柳、盐穗木、白刺、猪毛菜4种植被类型下的土壤物理性质进行了研究.结果表明:在水平方向上,1m剖面内柽柳土壤pH值、全盐含量、土壤容重最小,分别为8.75、0.97g/kg和1.42g/cm3;土壤有机质、含水率、总孔隙度、毛管孔隙度均最大,分别为9.04 g/kg、16.67％、45.57％和36.18％,表明柽柳能够显著降低土壤盐分,改善土壤结构.沿垂直剖面,4种植被类型在表层0-20 cm土壤盐分均达到最高,出现盐分“表聚”现象而形成“盐霜”;随着土层深度增加,含水率和土壤容重均呈显著性升高,土壤有机质、田间持水量、总孔隙度、毛管孔隙度和非毛管孔隙度均呈显著性降低(P＜0.05).相关性分析显示,土壤有机质是引起其他土壤物理性质变化的主要原因.相比空裸地,4种植被覆盖类型1 m剖面内土壤有机质、总孔隙度和毛管孔隙度均呈显著性提高,土壤容重显著性降低,有机质分别提高了162.94％、82.94％、85.59％和27.94％,总孔隙度分别提高了44.90％、20.83％、36.06％和15.80％,毛管孔隙度分别提高了58.27％、30.71％、43.48％和25.72％,土壤容重分别降低了18.86％、10.86％、17.14％和7.43％,表明干旱荒漠区盐碱土上生长的不同盐生植物能够显著改善土壤质量.     

Spatial distribution of acoustic and elastic properties of human femoral cortical bone

The purpose of this study is to quantify the spatial distribution of acoustic velocities and elastic properties (elastic constants) on Human femoral cortical bone. Four cross sections (average thickness of 2.09+/-0.27 mm) have been cut transversally between 40% and 70% of the total length and between them parallelepiped samples in each quadrant have been cut. Ultrasonic technique in transmission with immersion focused transducers at 5 MHz and contact transducers 2.25 MHz were used on the cross sections and parallelepiped samples, respectively. The first technique allows relative spatial distribution of velocities to be obtained, meanwhile the second technique allows the direct assessment of elastic constants. For both techniques, bulk velocities were found to be lower at the posterior side with an increase along the length (from 40% to 70% total length) (p < 0.05). Densities and elastic constants show equivalent pattern of variation. These variations are mainly due the cortical porosity related to vascularisation environment. The spatial distribution of velocities exhibits significant radial variation from the endosteal to the periosteal region. This is in agreement with variation of the porosity at that location. Same range of velocities was obtained with both techniques. The range of longitudinal velocities values varies from 3548 to 3967 m/s and between 18.5 and 33.1 GPa for the bulk velocities and axial elastic constants, respectively. Our results are within the range with those found in the literature. However, it must be noted that the range of acoustic and elastic properties variation is concerning the same bone. So, our new results show the ability of the technique to quantify accurately local variation of acoustic and elastic properties (within the section and along the length) of human cortical bone. Furthermore, our immersion technique could be used to assess the spatial distribution of the elastic constants with the knowledge of spatial distribution of densities.     

Bulk density determination as a simple and complementary tool in composting process control

Ten composting facilities (CF) treating source-sorted organic fraction of municipal solid waste (OF) were sampled to study the relationship between the bulk density and the composting process (CP) development. Hundred and fourteen samples from different stages of the CP were considered (organic fraction, initial mixture, final decomposition, final maturation and compost), including the reject materials coming from the densimetric table at postprocessing. Total organic matter (TOM), moisture content (MC), wet bulk density and dry basis (BDd) were determined. Significant differences were detected for MC, TOM and BDd between some stages of the CP. The BDd increased along the CP while TOM decreased. Correlation studies showed a significant negative relationship between TOM and bulk density, especially BDd, during the CP, as a result of the biological activity. Moreover, a clear relationship was also found between TOM and BDd in samples related to reject materials. The results indicate that bulk density could be a simple and useful tool to evaluate the CP, in addition to the others parameters commonly used. At the same time, BDd could be an easy way to infer TOM lost within rejects.     

湿度对堆肥理化性质的影响

水分是堆肥微生物生命活动的基础 ,也是堆肥中重要的工艺控制参数。弄清湿度对堆肥微生物及理化性质的影响 ,对于优化堆肥工艺参数、提高堆肥效率、降低投资和运行成本具有重要意义。综述了堆肥湿度研究的动态 ,指出了当前研究中存在的问题 ,并提出了未来的研究方向。大量的研究表明 ,湿度低于 4 5 %或高于 6 5 %都不利于堆肥处理。湿度太高会导致堆料的压实度增加、FAS减少、透气性能降低 ,从而导致堆体内氧气供应不足、堆肥升温困难、有机物降解速率降低、堆肥周期延长。湿度过低 ,水分会限制堆肥微生物的新陈代谢 ,导致微生物活性下降、堆肥腐熟困难。由于鼓风、散热、水蒸发等会使堆体内存在湿度的空间变异 ,也会降低堆肥效率和堆肥产品的质量。另外 ,堆肥湿度还影响堆肥的保肥能力。由各文献得出结论 ,堆肥的最佳湿度范围一般为 5 0 %～ 6 0 %左右     

Compost liquor bioremediation using waste materials as biofiltration media

Compost liquor results from the percolation of precipitation through composting waste; the release of liquids from high moisture content feedstocks; and as a result of runoff from hard surfaces and machinery. This research aimed to establish the potential for waste materials to act as media for low-cost compost liquor biofilters. Six types of potential biofilter media were packed into experimental biofilters (1 m long x 0.11 m diameter) and irrigated with compost liquor (organic loading rate of 0.6 kg/m3/d) for three months. The pH, BOD5, NH3/NH4+, and phytotoxicity of the effluent was monitored regularly. Natural, organic materials (oversize, compost and wood mulch) performed best, when compared to synthetic materials such as polystyrene packaging or inert materials such as broken brick. On average, the best media achieved 78% removal of both BOD5 and ammoniacal nitrogen during the study period. Although significant improvements in liquor quality were achieved, the effluent remained heavily polluted.     

干旱荒漠区煤矸石山覆土区土壤水分物理性质的空间异质性

基于网格取样(20m×20m),采用经典统计学和地统计学相结合的方法,研究了干旱荒漠区煤矸石山表层(0～5 cm)土壤水分物理性质的空间异质性和分布格局.结果表明:研究区土壤容重、毛管孔隙度、毛管最大持水量、总孔隙度、饱和含水量表现为弱变异,土壤含水率表现为中等变异.除土壤容重的最佳拟合模型为高斯模型外,其余指标的最佳...     

Effects of air-filled soil porosity and aeration on the initiation and growth of secondary roots of maize (Zea mays)

We studied the possibility whether the initiation of secondary roots is regulated by the air-filled porosity in soil, i.e. the availability of oxygen in the soil. Maize plants were grown in long PVC tubes (1 m long and 12 cm diameter) and were unwatered for different numbers of days so that variations of soil water content with depth were achieved on the same date with plants at the same age. The plants were harvested when their root systems were established in the whole soil column and watering had been withheld for 0, 15, 20, 25 days. A decrease of soil water content was significantly correlated with an increase of air-filled porosity in soil. The number of secondary lateral roots from segments of primary adventitious roots increased dramatically when soil water content decreased from field capacity to about 0.05 g water g^-1 dried soil. The total dried mass of roots at different soil depths was also positively correlated with soil air-filled porosity. It was observed that the elongation of the initiated secondary roots responded differently to the variations of soil air-filled porosity. The length of secondary roots increased initially when the soil was dried from field capacity to 0.18 g g^-1 dried soil (water potential at about−0.2 MPa, air-filled porosity 0.26 cm³ cm^-3), but was drastically reduced when the soil was dried further. Obviously elongation of secondary roots was inhibited when soil water potential began to deviate substantially from an optimum value. The present results suggested that the initiation of secondary roots was greatly promoted by the increase of air-filled soil porosity, i.e. availability of oxygen. This conclusion was further verified in a separate experiment where solution-cultured maize seedlings were subjected to different aeration treatments. An obvious increase in secondary root initiation was found in plants which were aerated with normal air (21% O₂) than in plants which were either not aerated or aerated with 5% O₂ air. ei]Section editor: B E Clothier     

Composting of high moisture content swine manure with corncob in a pilot-scale aerated static bin system

Pilot composting experiments of swine manure with corncob were conducted to evaluate the performance of the aerated static bin composting system. Effects of temperature control (60 and 70 degrees C) and moisture content (70% and 80%) were monitored on the composting by measuring physical and chemical indexes. The results showed that (1) the composting system could destroy pathogens, converted nitrogen from unstable ammonia to stable organic forms, and reduced the volume of waste; (2) significant difference of NH(4)(+)-N (P(12) = 0.074), and (NO(3)(-) + NO(2)(-))-N (P(12) = 0.085) was found between the temperature control treatments; (3) anaerobic reaction in the treatment with 80% moisture content resulted in significant difference of pH (P(23) = 0.006), total organic matter (P(23) = 0.003), and germination index (P(23) = 0.040) between 70% and 80%. Therefore, the optimum initial moisture content was less than 80% with the composting of swine manure and corncob by using the composting system.     

Compost convective airflow under passive aeration

For composting, passive aeration can save energy costs while being just as efficient as forced or active aeration. Passive aeration requires the proper design of aeration ducts, and thus, the proper prediction of the convective airflow rates created by the temperature differential between the compost and the ambient air. To establish such relationship, the temperature and convective air flow regimes of composts were investigated using three bulking agents (wood shavings, hay and straw), each at three moisture contents (MC-60%, 65% and 70%) spanning the normal values. All bulking agent and aeration treatments were aerated in duplicate under passive and active regimes. Laboratory vessels of 105 L were used for all treatments. Passive aeration treatments produced temperatures above 57 degrees C, as did the treatments actively aerated at 4 mg of air s(-1) kg(-1) of initial dry compost material. Compost MC had an effect only on the peak compost temperature, occurring between day 2 and 6. After 6 days of composting, MC no longer had any effect on temperature regime because of the loss of moisture by each mixture. A relationship was established between the Grasholf number (Gr-ratio of buoyancy to viscous forces) and the convective airflow rates, to size the aeration ducts for passive aeration. In general, convective airflow rates ranged from 1.5 to 0.7 mg of dry air s(-1) kg(-1) of initial compost dry matter, from day 0 to day 20, respectively, and for all compost treatments. This airflow rate sizes the aeration ducts installed under compost piles for passive aeration. As compared to straw where airflow rate dropped over a given level of Gr, wood shavings and hay were found to be more effective as bulking agents, as their airflow rate increased constantly with Gr.     

Factors affecting microbial formation of nitrate-nitrogen in soil and their effects on fertilizer nitrogen use efficiency

Mineralization of soil organic matter is governed by predictable factors with nitrate-N as the end product. Crop production interrupts the natural balance, accelerates mineralization of N, and elevates levels of nitrate-N in soil. Six factors determine nitrate-N levels in soils: soil clay content, bulk density, organic matter content, pH, temperature, and rainfall. Maximal rates of N mineralization require an optimal level of air-filled pore space. Optimal air-filled pore space depends on soil clay content, soil organic matter content, soil bulk density, and rainfall. Pore space is partitioned into water- and air-filled space. A maximal rate of nitrate formation occurs at a pH of 6.7 and rather modest mineralization rates occur at pH 5.0 and 8.0. Predictions of the soil nitrate-N concentrations with a relative precision of 1 to 4 microg N g(-1) of soil were obtained with a computerized N fertilizer decision aid. Grain yields obtained using the N fertilizer decision aid were not measurably different from those using adjacent farmer practices, but N fertilizer use was reduced by >10%. Predicting mineralization in this manner allows optimal N applications to be determined for site-specific soil and weather conditions.     

A novel approach to investigate biofilm accumulation and bacterial transport in porous matrices

Knowledge of bacterial transport through, and biofilm growth in, porous media is vitally important in numerous natural and engineered environments. Despite this, porous media systems are generally oversimplified and the local complexity of cell transport, biofilm formation and the effect of biofilm accumulation on flow patterns is lost. In this study, cells of the sulphate-reducing bacterium, Desulfovibrio sp. EX265, accumulated primarily on the leading faces of obstructions and developed into biofilm, which grew to narrow and block pore throats (at a rate of 12 micro m h(-1) in one instance). This pore blocking corresponded to a decrease in permeability from 9.9 to 4.9 Darcy. Biofilm processes were observed in detail and quantitative data were used to describe the rate of biofilm accumulation temporally and spatially. Accumulation in the inlet zone of the micromodel was 10% higher than in the outlet zone and a mean biofilm height of 28.4 micro m was measured in a micromodel with an average pore height of 34.9 microm. Backflow (flow reversal) of fluid was implemented on micromodels blocked with biofilm growth. Although biofilm surface area cover did immediately decrease (approximately 5%), the biofilm quickly re-established and permeability was not significantly affected (9.4 Darcy). These results demonstrate that the glass micromodel used here is an effective tool for in situ analysis and quantification of bacteria in porous media.     

油蒿演替群落密度对土壤湿度和有机质空间异质性的响应

如何用环境属性空间异质性解释植被动态是生态学中的一个重要问题。在该项研究中,选择油蒿(Artemisia ordosica)演替群落为研究对象,在小区面积相同、样方数目和面积相同的条件下,将统计学方法和地统计学方法结合起来,讨论分析了土壤湿度和有机质与油蒿和冷蒿(A. frigida)密度空间异质性变化趋势的相关性,结果表明:在块尺度上(80 m × 80 m),油蒿和冷蒿密度的空间异质性都与土壤湿度的空间异质性有关,其中与冷蒿密度呈现为单调递增,与油蒿密度不呈单调变化,说明土壤湿度与油蒿密度空间异质性的相关性已逐渐减弱,但与耐旱的冷蒿依然较强;土壤有机质的空间异质性也与两种植物密度的空间异质性有关,其中与油蒿密度呈现为单调递增,与冷蒿密度不呈单调变化,说明油蒿的长期定居增加了土壤有机质含量,并促进了冷蒿的侵入;进一步分析表明,该群落中油蒿种群和冷蒿种群均呈集群分布,这种集群分布使得油蒿或冷蒿的密度与土壤湿度或有机质空间异质性之间的关系增强,这从一定程度上说明了冷蒿和油蒿之间的竞争替代关系。因而,土壤空间异质性的变化是半荒漠带油蒿群落演替的基础。     

Airflow dynamics of coughing in healthy human volunteers by shadowgraph imaging: an aid to aerosol infection control

Cough airflow dynamics have been previously studied using a variety of experimental methods. In this study, real-time, non-invasive shadowgraph imaging was applied to obtain additional analyses of cough airflows produced by healthy volunteers. Twenty healthy volunteers (10 women, mean age 32.2±12.9 years; 10 men, mean age 25.3±2.5 years) were asked to cough freely, then into their sleeves (as per current US CDC recommendations) in this study to analyze cough airflow dynamics. For the 10 females (cases 1-10), their maximum detectable cough propagation distances ranged from 0.16-0.55 m, with maximum derived velocities of 2.2-5.0 m/s, and their maximum detectable 2-D projected areas ranged from 0.010-0.11 m(2), with maximum derived expansion rates of 0.15-0.55 m(2)/s. For the 10 males (cases 11-20), their maximum detectable cough propagation distances ranged from 0.31-0.64 m, with maximum derived velocities of 3.2-14 m/s, and their maximum detectable 2-D projected areas ranged from 0.04-0.14 m(2), with maximum derived expansion rates of 0.25-1.4 m(2)/s. These peak velocities were measured when the visibility of the exhaled airflows was optimal and compare favorably with those reported previously using other methods, and may be seen as a validation of these previous approaches in a more natural setting. However, the propagation distances can only represent a lower limit due to the inability of the shadowgraph method to visualize these cough airflows once their temperature cools to that of the ambient air, which is an important limitation of this methodology. The qualitative high-speed video footage of these volunteers coughing into their sleeves demonstrates that although this method rarely completely blocks the cough airflow, it decelerates, splits and redirects the airflow, eventually reducing its propagation. The effectiveness of this intervention depends on optimum positioning of the arm over the nose and mouth during coughing, though unsightly stains on sleeves may make it unacceptable to some.     

黑土肥沃耕层构建效应

东北黑土区粘重的耕地土壤,经多年不合理耕作后产生了较厚的“犁底层”,成为该地区农业生产的主要限制因子.本研究利用田间试验,分析了构建肥沃耕层对作物产量、土壤物理性质、土壤含水量和微生物数量的影响.结果表明：肥沃耕层构建后,土壤形成了一个深厚的耕层,作物产量增加.与常规耕作法相比,向20～35 cm土层施用秸秆和有机肥使土壤容重分别降低了9.88%和6.20%,总孔隙度分别增加了9.58%和6.02%,饱和导水率分别增加了167.99%和73.78%,表明肥沃耕层的构建能够有效地改善土壤的通气透水性,提高大气降水的入渗能力;向“犁底层”施用秸秆和有机肥处理0～100 cm土层土壤含水量和水分利用效率均显著高于常规耕作法,该处理玉米出苗率与0～35 cm土层土壤含水量之间呈显著正相关关系.肥沃耕层的构建由于增加了土壤中的有机碳源和透气性,从而增加了土壤中的微生物数量.