Mathematical models of dissolved oxygen concentration in fresh water

An adequate reserve of dissolved oxygen in a receiving stream is extremely important for protecting aquatic plants and animals, and for conserving our water resources. This paper briefly describes the environmental engineering significance of the stream self-purification, the current stream quality standards on dissolved oxygen concentration, and the solubility of dissolved oxygen in water. Special emphasis is placed on the modelling of the biological reactions and the dissolved oxygen saturation concentration in fresh water. The model can be used for calculating the dissolved oxygen saturation concentration, in turn, for determining the dissolved oxygen deficits, the critical dissolved oxygen concentration, and the allowable dissolved oxygen drop in a stream into which the waste water is discharged.     

Comparison of estimates of first-year dairy manure nitrogen availability or recovery using nitrogen-15 and other techniques

Measurements of dairy manure nutrient availability to crops typically show great variability. Approaches that are more accurate are needed to improve manure management and reduce nutrient loss to the environment. In this study, we compared direct (15N recovery) and indirect (difference method [Diff Meth] and fertilizer equivalence [FE] approach) methods of determining first-year dairy manure N availability or recovery during three cropping seasons. A field experiment was conducted on a Plano silt loam (fine-silty, mixed, superactive, mesic Typic Argiudolls) planted to corn (Zea mays L.). Plots received either manure, fertilizer N, or no N. Microplots receiving 15N-labeled manure were also established each study year. Manure was applied to a new plot each cropping season. Whole-plant N uptake was the best crop parameter to use for FE estimates. Estimates of N availability by relative effectiveness (Rel Eff), which are derived from the Diff Meth, and FE were similar (32 and 41%, respectively) and higher than unlabeled N or 15N recovery measurements because these indices factor in N use efficiency. Measures of the Rel Eff of manure N use were highly affected by control plot N uptake. The FE approach is less influenced by control plots, but it requires the inclusion of several more treatments and use of mathematical functions to describe crop response to N. These limitations are reflected in the wide ranges obtained for N availability estimates (-60 to 148%). Although apparent N recovery by the Diff Meth (14%) or direct measurements of 15N recovery (16%) were close on average, variability tended to be much lower for the 15N method. In addition, the Diff Meth was highly dependent on initial soil conditions. Use of 15N-labeled manure, although more costly and time-consuming, provided more consistent and reliable results.     

和谐社会更需要节约

不知从什么时候起，曾使我们这一代人引以为豪的“我国地大物二，自然资源取之尽、用之不竭”的认识成为了过去，菲薄的人均资源和普遍存在的浪费现象，已成为我国经济和社会发展进程中一个突出的问题。有数据表明，我国钢铁、有色金属、电力、化工等高耗能行业单位产品能耗比世界发达国家平均高40%以上，     

陕西省林火灾害及预防对策

应用陕西省5大林区9a火灾个例及相关资料，分析得出陕西省林火的时空分布规律，火源特点，林火造成的灾害，林火发生发展的影响因子，并提出了相应的森林防火对策。     

企业可持续发展与ISO14000环境管理体系标准初探

本文主要讨论了企业可持续发展与ISO14000环境管理体系标准的关系。该文分析了企业可持续发展的问题,介绍了ISO14000环境管理体系标准的内涵,指出了ISO14000环境管理体系标准是企业实现可持续发展的基础。     

沿海油田污染物入海通量及优化管理

胜利油田所在的黄河三角洲诸条河流按入海类型分为三种形式：设有防潮闸的感潮河；设有排涝站的入海河；直流入海的感潮河。按照各河流入海段面、流速、流量和水体污染物浓度，建立起各种感潮河污染物入海通量模式，计算结果说明沿海油田排放的石油类污染物入海通量为1456t／a，COD入海量为5720t／a。根据各条入海河流不同功能和污染物入海量，按照国家地表水质标准，制定出入海河流环境组合目标，用总量控制方法提出污染源削减要求，以保证黄河三角洲沿海滩涂环境质量。并以污染物入海通量、河流径流量、污染物自净系数和污染物削减量等因子建立各条河流优化管理模型，为保护环境提供对策。     

广西近年高温干旱气象灾害及对电力供求的影响

通过对广西2003~2005年高温、干旱天气气候事件及其对电力供求影响的分析发现:广西2003~2005年高温、干旱灾害强度偏强,频率增大;最高气温与最大电力负荷有明显的正相关关系,高温灾害天气造成电力负荷呈大幅度增加的趋势;季节性、持续性的干旱造成广西水电发电量呈负增长状态。由于电力负荷加大,水电发电量供应不足,使广西电力供求呈紧张的局面,2003~2005年出现了不同程度的拉闸限电现象。     

ANALYSIS OF LAS,ABS AND COMMERCIAL DETERGENTS BY TWO-PHASE TITRATION1

ABSTRACT: A two-phase titration method was developed and evaluated to determine the concentration of linear alkylate sulfonate (LAS), branched-chain alkyl benzene sulfonate (ABS), dishwashing detergents, and laundry detergents in water. This method is capable of quantitatively determining anionic surfactants in either fresh water or saline water and it is therefore superior to the widely used Methylene Blue Method. To simplify the titration method for adoptation to remote field utilization, a field test kit was developed. This test kit includes only a separatory funnel, a titration burette, a set of liquid measuring apparatus, and some chemicals. Emphasis was placed on compactness of the kit and simplicity in the test manipulation, so that its operation can be performed by relatively unskilled wastewater monitoring personnel.     

Reconstruction of 137Cs signal in Cuba using 7Be as tracer of vertical transport processes in the atmosphere

Levels of 137Cs and 7Be in aerosols have been measured in the region of Cienfuegos (Cuba) during the period 1994-1998. 137Cs showed the same seasonal trend as 7Be and the monthly regimes of precipitation seemed to be responsible for the observed pattern. The 137Cs/7Be ratio obtained in Cienfuegos and Miami (FL) in this period was used to calibrate the long-term database of 137Cs concentrations recorded in Miami (250 km from Cienfuegos). The database was then employed to reconstruct the 137Cs monthly concentrations in Cienfuegos since 1957.     

微波法复合絮凝剂PAFC-PAM的制备及脱色性能

研究了以三氯化铝,三氯化铁和阳离子聚丙烯酰胺为原料,在微波辐照下制备PAFC-PAM复合絮凝剂的工艺条件,探讨了pH值、复合絮凝剂投加量对活性染料模拟废水脱色率的影响,并考察了其对实际印染废水的处理效果。结果表明:在PAM/PAFC质量比为0.25、微波合成功率150W、微波时间3min制得的复合絮凝剂,浊度去除率为98.8%。在pH=8,投加量为42mg/L的最佳絮凝条件下,复合絮凝剂对模拟染料废水脱色率高达97%。与PAFC和PAM相比,PAFC-PAM具有较宽的pH适宜范围和较低的投加量且对实际印染废水的处理效果优于PAFC和PAM。