水稻秸秆还田对福州平原稻田土壤水稳性团聚体分布及稳定性影响

为阐明早稻与晚稻生长期土壤水稳性团聚体分布及其稳定性对秸秆还田的响应,以福州平原红壤水稻田为研究对象,对秸秆还田后早稻田和晚稻田土壤水稳性团聚体分布特征及其稳定性,包括粒径0.25 mm团聚体的百分含量R0.25、平均质量直径(MWD)、平均几何直径(GMD)和分型维数(D)进行测定与分析.研究结果表明,秸秆还田和对照样地,0~40 cm土层中早稻与晚稻生长期土壤均表现为水稳性团聚体组成以微团聚体(0.25 mm粒级团聚体)为主,团聚体粒级越大,含量越少;秸秆还田对0~40 cm土层中早稻田土壤水稳性大团聚体和微团聚体总含量的影响均不显著,但秸秆还田显著增加了晚稻田土壤水稳性大团聚体(粒径0.25 mm)含量(p0.05),并显著减少了土壤水稳性微团聚体含量(p0.05);秸秆还田对早稻田土壤水稳性团聚体MWD、GMD和D值影响均不显著,但显著增加了晚稻田土壤水稳性团聚体MWD和GMD值,显著降低了土壤水稳性团聚体D值(p0.05);秸秆还田对早稻田土壤水稳性团聚体稳定性影响不显著,但显著增加了晚稻田土壤水稳性团聚体稳定性(p0.05).     

废弃物施加对福州平原稻田土壤团聚体分布及其稳定性的影响

为了阐明废弃物施加对稻田土壤团聚体分布及其稳定性的影响,以福州平原稻田为研究对象,对对照、石膏、贝壳、生物炭和炉渣5种处理样地0~10 cm、10~20 cm、20~30 cm土层土壤团聚体分布及其稳定性,包括0.25 mm团聚体含量(DR0.25)、平均质量直径(MWD)、几何平均直径(GMD)、分形维数(D)进行了测定和分析.结果表明,与对照样地相比,石膏、贝壳、生物炭和炉渣施加后均增加了土壤团聚体DR0.25、MWD和GMD值,其中,石膏施加后土壤团聚体DR0.25、MWD和GMD值分别增加了12.76%、12.13%和12.17%,贝壳施加后分别增加了32.65%、31.83%和33.86%,生物炭施加后分别增加了12.07%、9.32%和11.70%,炉渣施加后分别增加了19.70%、13.59%和18.10%,但与对照样地相比,石膏、贝壳、生物炭和炉渣施加后土壤团聚体分形维数均表现为减小的趋势,分别减小了4.02%、11.65%、4.37%、9.29%.从土壤团聚体DR0.25、MWD、GMD值和分形维数的变化特征来看,石膏、贝壳、生物炭和炉渣施加均提高了土壤团聚体的稳定性.     

Effect of cement content and recycled rubber particle size on the performance of rubber-modified concrete

According to the Rubber Manufacturer’s Association, the United States generated 3664 thousand metric tons of scrap tires in 2015. While most waste tires are repurposed, approximately 409.5 thousand metric tons were disposed in landfills. This study investigates an alternative use of the waste tires as a replacement of natural aggregates in concrete mixtures. This study investigated fresh concrete properties and compressive strength. Different coarse and fine aggregate rubber particle sizes were evaluated: 19-mm tire chips (TCs) and 30-mesh crumb rubber (CR). TCs were used to replace coarse aggregates, while CR was used to replace fine aggregate in the concrete mixtures in increments of 10% by volume. Concrete strength loss was reduced with a fine aggregate replacement with CR as opposed to greater losses of strength exhibited by a coarse aggregate replacement with TCs. Adequate strengths were achieved at replacement levels as high as 40% by volume with CR, whereas satisfactory strengths were achieved with only a 10% replacement of coarse aggregates with TCs. Acceptable strengths were obtained from mixtures utilizing a combination of the two rubber sizes. Cement content was observed to have greater influence on rubberized concrete compressive strength at lower rubber contents than higher levels.     

Recycling of air pollution control residues from municipal solid waste incineration into lightweight aggregates

This work focuses on the assessment of technological properties and on the leaching behavior of lightweight aggregates (LWA) produced by incorporating different quantities of air pollution control (APC) residues from municipal solid waste (MSW) incineration. Currently this hazardous waste has been mostly landfilled after stabilization/solidification. The LWA were produced by pelletizing natural clay, APC residues as-received from incineration plant, or after a washing treatment, a small amount of oil and water. The pellets were fired in a laboratory chamber furnace over calcium carbonate. The main technological properties of the LWA were evaluated, mainly concerning morphology, bulk and particle densities, compressive strength, bloating index, water adsorption and porosity. Given that APC residues do not own expansive (bloating) properties, the incorporation into LWA is only possible in moderate quantities, such as 3% as received or 5% after pre-washing treatment.The leaching behavior of heavy metals from sintered LWA using water or acid solutions was investigated, and despite the low acid neutralization capacity of the synthetic aggregates, the released quantities were low over a wide pH range.In conclusion, after a washing pre-treatment and if the percentage of incorporation is low, these residues may be incorporated into LWA. However, the recycling of APC residues from MSW incineration into LWA does not revealed any technical advantage.     

煤与生物质燃烧生成碳黑团聚物的形态分析

为分析碳黑团聚物对大气环境监测、气候预测等领域的影响,对其形态进行分析。用分形参数来表征碳黑团聚物的形态变化,将煤与生物质燃料燃烧生成的烟气取样后洗涤、离心、干燥并制成膜片,通过透射电镜(JEM-2100)获得膜片镜下图片,利用IMAGEJ测量电镜图片中团聚物的几何参数,通过几何参数推断出团聚物的分形参数,得出分形维数D_f在0.68~3.42变化,前向因子K_g在0.09~3.71变化,分形参数值越大,碳黑团聚物形态越趋于球形。     

Use of system dynamics for proper conservation and recycling of aggregates for sustainable road construction

A significant amount of mineral aggregates are used in constructing, rehabilitating and maintaining roads. As local (nearby) quarries get exhausted, aggregates need to be hauled from sources that are at ever-greater distances. Hence, over time the cost of trucking as well as the amount of emissions generated by trucking increases with a decrease of local natural aggregate stocks. The objectives of this study are to construct and utilize a system dynamics model of the depletion of a stock of natural aggregates due to pavement construction and maintenance, and determine the effect of using local and nonlocal aggregates, recycling and project cancellation (slowing growth) on the paving of roads. Long-term simulations are carried out with available aggregate stock, trucking distance and cost data. The quality of roads and a sustainability score, based on engineering, economic and environmental factors (emissions) are evaluated for different scenarios. An optimal combination of the use of local and nonlocal recycled aggregates, recycling and project cancellation is recommended. The proposed system dynamics model could be utilized by agencies to plan for the proper utilization of aggregate resources for road development and maintenance/rehabilitation projects.     

沙土不同粒径微团聚体对磷的富集特征

流失的水土是污染物的重要载体,为估算沙土吸附态磷流失量,采用平衡吸附法研究了沙土不同粒径微团聚体对磷的富集特征.结果表明,不同粒径微团聚体对磷的富集系数为:黏粒(3.79)＞粉粒(2.98),沙土中微团聚体对磷的富集作用比较强,其原因有三:细粒级微团聚体中腐殖质含量显著高于粗粒级;细粒级微团聚体中有机质是通过可溶有机质与黏土矿物相互结合形成复合体而富集,在复合体结构中存在孔隙填充方式磷吸附;粘粒和粉粒中的铁铝键有机矿质复合体所占比例显著高于其它粒级,在对磷吸附中发挥重要作用,其吸附机制除孔隙填充方式外,还存在铁铝氧化物及水化氧化物对磷的配位吸附.不同粒径团聚体对磷的吸附分配系数和富集系数均与腐殖质总量呈显著正相关(p＜ 0.01,r分别为0.854和0.954);西辽河流域沙土在暴雨径流中黏粒级和粉粒级冲泻质泥沙所携载的吸附态磷质量分数可分别按1269.15 mg·kg-1和997.53 mg·kg-1估算,黏粒和粉粒级微团聚体对磷的富集系数(Er)可分别按3.79和2.98计算.     

餐厨垃圾制备的外源有机碳对土壤团聚体的影响

为了阐明外源有机碳对土壤碳库的作用机制,以餐厨垃圾为原料,制备了4种不同分子量级的外源有机碳,通过室内试验,研究了外源有机碳对土壤有机碳组分及土壤团聚体的影响.结果表明:①以分子量≤1 ku为主的小分子有机碳处理组土壤中w（DOC）（DOC为水溶性有机碳）比CK组增加了0.383 g/kg,CO₂累积释放量达到（6.595±0.259）mg/kg（以C计）;微生物活性增强,>5 mm水稳大团聚体质量分数相对于CK组提升了25.06%,表明小分子有机碳增强了土壤微生物活性,微生物通过菌根网络缠绕作用促进大团聚体形成,增强土壤团聚体稳定性.②以分子量≥5 ku的大分子有机碳为主的大分子有机碳处理组w（POC）（POC为颗粒态有机碳）为CK组的5.65倍,0.5~1 mm水稳大团聚体质量分数增加了10.84%,有机碳贡献率提升了14.79%,表明大分子有机碳通过增加土壤中w（POC）,促进0.5~1 mm水稳大团聚体形成,提高团聚体有机碳贡献率.研究显示,不同分子量级外源有机碳通过不同的方式改善土壤团聚体结构进而促进土壤有机碳固定,餐厨垃圾生物强化有机肥中各量级有机碳比例合理,能够明显提升土壤有机碳水平,增加土壤团聚体稳定性.      

不同种植模式对土壤团聚体及有机碳组分的影响

结合在有机农场近10年的定位研究,通过同步采样分析,比较了有机种植和常规种植两种不同模式下土壤团聚体组成、分配及团聚体内有机碳组分的差异.结果表明,常规种植模式下随着团聚体粒级的减小,团聚体4个粒级(1 mm、1~0.5 mm、0.5~0.25 mm和0.25 mm)的含量均值分别为23.75%、15.15%、19.98%和38.09%,而有机种植模式下各粒级团聚体(1 mm、1~0.5 mm、0.5~0.25 mm和0.25 mm)的含量分别为9.73%、18.41%、24.46%和43.90%,0.25 mm微团聚体含量显著高于常规种植.有机种植模式提高了土壤有机碳和全氮含量,平均值分别为17.95 g·kg-1和1.51 g·kg-1.有机种植模式下相同粒级间,团聚体中重组有机碳平均含量显著高于常规种植,且重组有机碳在0.25 mm这部分稳定性有机碳主要储存场所的微团聚体中富集.有机种植模式下易氧化态碳在1 mm大团聚体中的含量显著高于常规种植,其它粒级间没有显著差异,易氧化态碳在1 mm大团聚体中富集.有机种植模式增加了土壤有机碳及其组分含量,缓解了耕作对团聚体的破坏,并增强了有机碳的稳定性.有机种植有利于土壤固碳,这为进一步加快我国有机农业的发展提供了理论依据.     

Comparison of batch leaching tests and influence of pH on the release of metals from construction and demolition wastes

Construction and demolition wastes are suitable for use in road construction. However, leaching characterization of recycled materials is required to determine their pollutant potential and the consequence of their application in different scenarios. The motivation of this paper is derived from the increasing use of different leaching test methods. In Europe, the confusion resulting from the wide variety of tests used to evaluate environmental properties of construction materials implies that an evaluation of the current practices and the attempt to consolidate the approaches are required.Two equilibrium-based leaching tests (the Dutch test and the European standard) were conducted to assess the environmental impact of four recycled aggregates. Three natural limestone aggregates were used as controls. Both tests measure the potential release of hazardous elements under extreme conditions using different leaching parameters (L/S ratio, pH value and contact time). The results proved that pH is the most relevant factor on the assessment of the differences between leaching methods due to its strong control on the pollutant release.To classify the materials according to their environmental effects, the concentration limit values of the metals imposed by Council Decision 2003/33/EC were used as a reference. The comparison allowed the classification of the recycled aggregates as inert wastes, with the exception of the MR-2 aggregate, which was classified as non-hazardous material.