Fluxes of NO3-, NH4+, NO,NO2, and N2O in an Old Danish Beech Forest

The fluxes of the major nitrogen compounds havebeen investigated in many ecosystem studies over the world.However, only in few studies has attention been drawn to theimportance of the fluxes of minor gaseous nitrogen compoundsto complete the nitrogen cycle. In Denmark a detailed study onthe nitrogen cycle in an old beech forest has been implementedin 1997 at Gyrstinge near Sorø, Zealand. The study includesthe fluxes of the gases NO, N₂O and water mediatedtransport of NO₃ ^- and NH₄ ⁺. Measurementsof the fluxes of the gaseous compounds are performed withmicro-meteorological methods (eddy-correlation and gradient)and with chambers. Water mediated fluxes encompass rain,throughfall, stem-flow and leaching from the root zone. Thehydrological model is verified by TDR measurements. The findings show that the total water mediated N input tothe forest floor with throughfall and stemflow was 25.6 kg Nha^-1 yr ^-1, and open field wet deposition withprecipitation was 19.0 kg N ha^-1 yr ^-1. The internalcycling of N in the ecosystem measured as turnover oflitterfall and plant uptake was 100 kg N ha^-1 yr ^-1and 14 kg N ha^-1 yr ^-1, respectively. The fluxes ofthe gaseous N compounds NO and N₂O were of minorimportance for the total N turnover in the forest, NO_xemission being <1 kg N ha^-1 yr ^-1 and N₂Oemission from the soil being 0.5 kg N ha^-1 yr ^-1 withno significant difference between wet and dry soils.Concentrations of NO₃ ^- and NH₄ ⁺ in thesoil solution beneath the rooting zone are very small andconsequently the N leaching is almost negligible. It isconcluded that the nitrogen mass balance of this old beechforest ecosystem mainly is controlled by the input by dry andwet deposition and a large internal N cycle with a fast litterturnover. The nitrogen input tothe forest ecosystem which currently exceeds the critical loadby 5 kg N ha^-1 yr ^-1is mainly accumulated in the soil and no significant nitrateleaching is occurring.     

Incorporation of Seasonal Nitrogen Dynamics within a Long-Term Acidification Model

This paper describes an application of the long termdynamic model, MAGIC, on a monthly timestep, enablingincorporation of the seasonal dynamics associated with abroad understanding of the ecosystem N cycle. The modelhas been applied to the Dargall Lane catchment in theGalloway region of Scotland where marked seasonal Ndynamics are apparent. Mean monthly proportions ofrainfall, runoff, deposition fluxes and net retention ofN are utilised to drive the model on a monthly timestep.Calibration of the model has successfully reproduced thepresent day observed seasonal variation in streamNO₃ and ANC. Prediction of recovery at the siteunder the second sulphur protocol indicates that,although mean annual ANC increases, mean monthly ANC doesnot rise above zero for all months of the year until2010.     

高效复合微生物菌群在垃圾堆肥中的应用

利用高效复合微生物菌群对生活垃圾和污泥混合堆肥,通过测定堆肥过程中总菌数、温度、有机物、C/N比等,较系统地研究了高效复合微生物菌群在生活垃圾、污泥混合堆肥系统中的作用.试验证明:在生活垃圾和污泥共堆肥系统中,调节堆料比为厨房垃圾:污泥:粉煤灰土:成熟堆肥污泥:干草=41.6:27.8:13.8:11.1:5.5,有机物约为60%,总氮14%,全磷0.69%,全钾1.25%;初始含水率为58.5%,初始C/N比=30i供气量控制在0.8L/min·kg挥发性有机物,处理1、处理2、处理3堆料中分别接种2%、3%、5%(质量分数)的高效复合微生物菌群,与加入3%灭活菌的对照组进行对比实验.对照组、处理1、处理2和处理3堆肥系统垃圾腐熟时间分别为30d、24d、18d和12d;说明高效复合微生物菌群可以加速生活垃圾和污泥的降解,保证堆肥过程的顺利进行.处理3与对照组相比,堆腐时间缩短了18d,同时成品堆肥中含有大量具有生物活性的微生物,是一种良好的生物活性有机肥料.     

氮缺乏引起的非丝状菌活性污泥膨胀

采用SBR法处理啤酒废水,研究了进水中不同有机物与总氮的比值(以BOD/N计)条件对活性污泥膨胀的影响.结果表明,在进水BOD/N为100/4的条件下,污泥的沉降性能良好;在进水BOD/N分别为100/3和100/2时,均发生由高含水率的粘性菌胶团过量生长引起的非丝状菌膨胀.在进水BOD/N为100/0.94的条件下,发生的非丝状菌膨胀最为严重.试验中还研究了氮缺乏条件下污泥微生物对氮源和磷源的利用率以及COD去除率的变化.     

中国氮氧化物排放清单及分布特征

根据能源消费历史状况和氮氧化物(NO_X)排放因子,估算了近20年来中国NO_X的排放变化,并讨论了1995～1998年分省区、分行业、分燃料的NO_X排放清单及特征.中国NOX排放总量已由1980年的4.76Mt快速增加到1996年的12.0Mt,之后,NOX排放持续增加的趋势得到遏制,1998年NO_X排放总量与1996年峰值相比下降了约0.82Mt.NO_X排放在燃料、行业及地域分布上均不平衡的特征没有根本改变:燃煤排放NO_X一直占总量的70%以上;绝大部分NO_X来自工业、电力和交通部门,约占90%左右,且交通部门NO_X排放比例逐年上升,已由1995年的10.4%快速增长到1998年的约13.0%;中东部的河北、辽宁、江苏、山东、河南、广东等省区NO_X排放量较大,均超过0.5Mt而宁夏、青海和海南等边远省区NO_X排放量很低,小于0.1Mt.     

环境监测用高锰酸盐指数和氨氮标准溶液量值比对研究

针对高锰酸盐指数(COD_Mn)和氨氮(NH₃-N)标准溶液(以下简称液标)制造商、浓度水平和使用情况进行调研,根据调研结果选择常用的7个品牌COD_Mn液标和9个常用NH₃-N液标品牌开展量值比对和质量评价研究,匿名采购129支液标经盲样编码后采用《地表水环境质量标准》(GB 3838—2002)推荐标准进行分析测定,计算和评定测定结果的不确定度,以En法进行量值比对评价。研究表明,NH₃-N液标量值均满意,COD_Mn测试中的加盖操作会使测定结果偏高,按照证书要求操作时COD_Mn液标量值合格,未按照液标证书中要求进行液标样品前处理测定会造成测定结果的偏离,影响评价结果。建议监测人员合理选用和规范使用环境用液标,加强环境用液标的选购和管理,确保检测过程得到有效控制。     

NUTRIENT CONCENTRATIONS AND YIELDS IN UNDEVELOPED STREAM BASINS OF THE UNITED STATES1

ABSTRACT: Data from 85 sites across the United States were used to estimate concentrations and yields of selected nutrients in streams draining relatively undeveloped basins. Flow‐weighted concentrations during 1990–1995 were generally low with median basin concentrations of 0.020, 0.087, 0.26, 0.010, and 0.022 milligrams per liter (mg/L) for ammonia as N, nitrate as N, total nitrogen, orthophosphate as P, and total phosphorus, respectively. The flow‐weighted concentration of nitrate exceeded 0.6 mg/L in only three basins. Total nitrogen exceeded 1 mg/L in only four basins, and total phosphorus exceeded 0.1 mg/L in only four basins. The median annual basin yield of ammonia as N, nitrate as N, total nitrogen, orthophosphate as P, and total phosphorus was 8.1, 26, 86, 2.8, and 8.5 kilograms per square kilometer, respectively. Concentrations and yields of nitrate tended to be highest in northeastern and mid‐Atlantic coastal states and correlated well with areas of high atmospheric nitrogen deposition. Concentrations and yields of total nitrogen were highest in the southeastern part of the nation and in parts of the upper Midwest. In the northeast, nitrate was generally the predominant form of nitrogen, and in the southeast and parts of the upper Midwest, organic nitrogen was the dominant form. Concentrations of total phosphorus were generally highest in the Rocky Mountain and Central Plain states.     

AFTER THE 1993 FLOOD: A WATER AND SURFICIAL BED SEDIMENT QUALITY SCENARIO ON THE ILLINOIS AND UPPER MISSISSIPPI RWERS1

ABSTRACT: Effects of the 1993 flood on river water and sediment quality were investigated using historical data and data collected from the Illinois River and Upper Mississippi River in a post‐flood period. Overall the post‐flood results showed systematic reductions and individual changes in the water and sediment constituents. The reductions in sediment metals and nutrients were most obvious at the Keokuk and Lock and Dam 26 stations. By analyzing and comparing the physical changes to the changes in water and sediment constituents at each station, it was found that physical processes such as sediment entrainment and, more importantly, the removal of fine sediment to be the main causes for the reduced concentrations in sediment constituents. On the other hand, sediment redistribution and associated secondary contamination could have caused the emergence of several water and sediment constituents that were undetected before the flood.     

晚期渗滤液脱氮过程中的抑制现象及其消除

对于垃圾填埋过程中高氨氮浓度、低C/N的晚期渗滤液,反硝化碳源不足会造成A/O脱氮系统的亚硝酸积累,导致对氨氧化和亚硝酸氧化过程的抑制作用.A,²/O流程中的厌氧处理对难降解有机物的水解酸化作用可为后续反硝化提供易降解有机碳源,可消除亚硝酸盐的积累及其对硝化过程的抑制.试验表明,厌氧处理可使氨氧化速率和反硝化速率提高约1倍和1.3倍,分别达0.123mgN/(mgMLSSd)和0.0675mgN/(mgMLSSd),TN去除率由8%提高到15%.使浓度高达1000mg/L的氨氮,在0.138mgN/(mgMLSSd)的进水负荷下较为彻底地氧化为安全的硝酸盐.     

介质阻挡放电等离子体直接分解NOx的影响因素

在以 γ- Al₂O₃小球作为填充物的介质阻挡放电条件下 ,研究放电电压 ( 9～ 16k V)、交流电源频率 ( 50～ 1600 Hz)、NO入口浓度 ( 50～1800 ml/m³)、气体空速 (1000～ 6500 h^-1)、反应温度 ( 20～250℃ )、介质小球比表面积及加入 O₂等因素对 NO分解率的影响 .发现提高放电电压、放电频率及介质小球比表面积能显著增加 NO分解率 ,O₂ 的加入对 NO的等离子体分解有强抑制作用 .