Release Characteristics of Nutrients from Polymer-coated Compound Controlled Release Fertilizers

Reliable information regarding release characteristics of nutrients from a polymer-coated controlled release fertilizer (CRF) is essential for beneficial agronomic and environmental results. Significant knowledge regarding nitrogen release from polymer-coated urea was gained while the information regarding the release of the different nutrients contained in polymer-coated compound N–P–K CRF remains limited. An experiment in which major factors affecting the differential release of nutrients from two coated compound CRF was performed in free water, water saturated sand and sand at field capacity. In general, nitrate release was the fastest, followed by ammonium and potassium whereas phosphate was significantly slower, with a rate of linear release in free water 45–70% slower than that of nitrate. Little differences were obtained for the lag periods of nitrate, ammonium and potassium release (2–10 days) under the experimental conditions, whereas for P they were one order of magnitude larger. The main factor slowing the release was assumed to be the lower solubility of ions with P being the least soluble. Release into free water was, expectedly, somewhat faster than that into saturated sand and significantly faster as compared to sand at field capacity and particularly so for P. Raising the temperature from 20 °C to 40 °C increased the rate of linear release of the different nutrients. The energy of activation, EA_rel, estimated for the linear release, of the different nutrients, was narrow ranging between 37 to 46 (KJ mol⁻¹) whereas the mean values obtained for the two CRF, differing by 50% in coating thickness, was non-significant. However, EA_rel was significantly different in different media. The complex effect of temperature on the lag period and nutrient interactions during release deserve further investigation.     

Effects of selected metal oxides on the dechlorination and destruction of PCDD and PCDF

OCDD and OCDF spiked silica/graphite based model fly ash containing various copper compounds and metal oxides were thermally treated under oxygen deficient conditions. All copper compounds tested showed a considerable dechlorination/hydrogenation reaction at 260 °C. After 30 min at 340 °C, less than 1% of the spiked OCDD and OCDF was recovered as T₄CDD/F to OCDD/F. Other compounds tested demonstrated a lower rate of dechlorination compared to the copper compounds. However, all other metal oxides showed a small dechlorination effect at 260 °C, which was considerably increased at 340 °C.

The model fly ash containing the different copper compounds or metal oxides showed comparable PCDD and PCDF isomer patterns after thermal treatment. However, small differences were observed among the different tested compounds. The PCDD and PCDF isomer patterns on the model fly ashes were similar to patterns found during dechlorination experiments on fly ashes from waste incineration processes.

Model fly ash containing Ca(OH)₂ exhibited the highest destruction potential, but a low dechlorination potential. In contrast, model fly ash containing any of the remaining compounds tested, was found to predominantly dechlorinate the spiked OCDD and OCDF.     

污染源自动监测异常数据识别规则及处理方法探索

基于大量污染源自动监测数据的特征分析与异常原因解析,探索建立针对自动监测异常数据的识别规则与标志处理方法,并通过模型训练实现了异常数据的自动标志.经实例验证,该方法可识别异常偏高、异常偏低、异常为0、迟滞不变、逻辑错误等5种类型的异常数据,按照数据有效性及异常原因进行标志处理,可以为后续数据分析及各类模型训练提供数据基...     

张家口市洋河、桑干河流域水环境健康风险评价

张家口市洋河、桑干河流域近几年来水质持续改善,为逐步恢复流域水质和下游官厅水库饮用水备用水源功能提供了条件.文章利用水环境健康风险评价模型,选取了2006年该流域水质监测数据,对流域内10个监测断面由饮水途径引起的水环境健康风险进行了评价.结果表明,该流域水体对人体健康危害最大的是化学致癌物Cr(VI),在各个监测断面中Cr(VI)的个人年风险均超过ICRP推荐的标准.同时,化学致癌物对人体健康危害的个人年风险超过非致癌物的个人年风险;因此对该流域水体的含化学致癌物Cr(VI)和As废水进行控制和治理是降低水环境健康风险的有效途径.     

煤矿安全目标管理成果评价的模型与方法

在简要介绍煤矿安全目标管理方法和目标体系的基础上,提出了确定安全目标管理综合目标值的ＧＭ（１,Ｎ）－ ＳＭＣＯ模型,用于对目标成果进行评价,并给出了某煤矿安全目标管理成果评价的应用实例     

任意变截面棒材无模拉伸数学模型的研究

无模拉伸是近年来新开发的一种金属成形工艺。此文在对无模拉伸的发展动态、国内外研究概况等进行综合分析的基础上,分析了任意变截面棒材无模拉伸的变形机制及成形可行性,提出了任意变截面棒材无模拉伸速度或冷热源移动速度的理论计算方法。并提出了几种抛物面棒材无模拉伸的速度模型。经过实验研究证明,此文提出的速度模型较好地表达了任意变截面棒材无模拉伸速度变化规律。     

土地利用与流域水环境管理研究

从土地利用活动与环境的关系着手，分析得出物质流动是联系两者纽带的结论；提出了污染物及沉积物输移的计算模型；最后，探讨了通过土地利用来改善水环境的措施和方法。     

多元线性回归与灰色联合模型在湖泊水质预测中的应用

根据对湖泊水体中所含高锰酸盐指数、氨氮、总磷等主要化学指标及其相关因素人口、工业产值和污水排放量的数据,采用了多元线性回归方法建立了湖泊水质预测的数学模型。并用多元线性回归和灰色模型联合的方法进行实际预测,多元线性回归模型通过F检验认为回归方程的效果比较显著,灰色模型精度检验达到二级,收到了良好效果。     

宁镇山脉岩基岩浆的化学演化

本文根据四个杂岩体中主要矿物的化学成分和全岩主要元素资料,利用T·L·Wright(1984)提供的质量平衡计算程序来模拟它们的成因,然后再用微量元素来检验和完善上述模式。定量模拟结果表明,分离结晶作用是造成这些杂岩体在岩石学和地球化学上分异的主要原因,并可用斜长石,角闪石、黑云母、磷灰石和榍石的分步分离来解释各杂岩体的成分变化,但对每一个杂岩体来说矿物分离比例可大不相同。微量元素的检验结果和主要元素的模拟趋势基本一致,但分离矿物的绝对值可不完全相同。     

炉膛干粉喷射脱SO_2的研究

在夹带流反应器（ＥＦＲ）中进行的石灰石／ＳＯ_２高温硫酸化反应的实验研究。硫酸化反应是一个两阶段反应，初始阶段是一个非常快的（约０．３秒）零级表面反应，活化能为２１．０ｋＪ／ｍｏｌ；接着是活化能为８０．１ｋＪ／ｍｏｌ的产物层扩散控制反应。此硫酸化反应过程能用缩芯模型来模拟。喷射Ｆ－石灰石，９０％以上的脱硫率能达到。