农药在土壤中迁移的研究方法

农药对地下水的污染已日益为人们密切关注，本文详细介绍了用土壤柱和土壤薄层层析法研究农药在土壤迁移行为用于预测或评价农药对地下水污染程度的研究方法。     

Volatile organic compounds at swine facilities: A critical review

Volatile organic compounds (VOCs) are regulated aerial pollutants that have environmental and health concerns. Swine operations produce and emit a complex mixture of VOCs with a wide range of molecular weights and a variety of physicochemical properties. Significant progress has been made in this area since the first experiment on VOCs at a swine facility in the early 1960s. A total of 47 research institutions in 15 North American, European, and Asian countries contributed to an increasing number of scientific publications. Nearly half of the research papers were published by U.S. institutions.Investigated major VOC sources included air inside swine barns, in headspaces of manure storages and composts, in open atmosphere above swine wastewater, and surrounding swine farms. They also included liquid swine manure and wastewater, and dusts inside and outside swine barns. Most of the sample analyses have been focusing on identification of VOC compounds and their relationship with odors. More than 500 VOCs have been identified. About 60% and 10% of the studies contributed to the quantification of VOC concentrations and emissions, respectively. The largest numbers of VOC compounds with reported concentrations in a single experimental study were 82 in air, 36 in manure, and 34 in dust samples.The relatively abundant VOC compounds that were quantified in at least two independent studies included acetic acid, butanoic acid (butyric acid), dimethyl disulfide, dimethyl sulfide, iso-valeric, p-cresol, propionic acid, skatole, trimethyl amine, and valeric acid in air. They included acetic acid, p-cresol, iso-butyric acid, butyric acid, indole, phenol, propionic acid, iso-valeric acid, and skatole in manure. In dust samples, they were acetic acid, propionic acid, butyric acid, valeric acid, p-cresol, hexanal, and decanal. Swine facility VOCs were preferentially bound to smaller-size dusts.Identification and quantification of VOCs were restricted by using instruments based on gas Chromatography (GC) and liquid chromatography (LC) with different detectors most of which require time-consuming procedures to obtain results. Various methodologies and technologies in sampling, sample preparation, and sample analysis have been used. Only four publications reported using GC based analyzers and PTR-MS (proton-transfer-reaction mass spectrometry) that allowed continuous VOC measurement. Because of this, the majority of experimental studies were only performed on limited numbers of air, manure, or dust samples. Many aerial VOCs had concentrations that were too low to be identified by the GC peaks.Although VOCs emitted from swine facilities have environmental concerns, only a few studies investigated VOC emission rates, which ranged from 3.0 to 176.5 mg d⁻¹ kg⁻¹ pig at swine finishing barns and from 2.3 to 45.2 g d⁻¹ m⁻² at manure storages. Similar to the other pollutants, spatial and temporal variations of aerial VOC concentrations and emissions existed and were significantly affected by manure management systems, barn structural designs, and ventilation rates.Scientific research in this area has been mainly driven by odor nuisance, instead of environment or health concerns. Compared with other aerial pollutants in animal agriculture, the current scientific knowledge about VOCs at swine facilities is still very limited and far from sufficient to develop reliable emission factors.     

凹凸棒黏土覆盖对沉积物磷赋存形态的影响

通过实验室模拟实验,研究了800℃热处理凹凸棒黏土覆盖对沉积物中磷的赋存形态影响,采用连续化学提取法和31P核磁共振(31P NMR)分析了覆盖过程中磷的形态变化,并借助扫描电镜能谱仪(SEM-EDS)对磷的形态转化机理进行初步探讨.结果表明,热处理凹凸棒黏土覆盖使沉积物表层中的活性磷平均含量从308.6mg/kg降低到241.1mg/kg,钙磷的平均含量从204.9mg/kg 增加到257.3mg/kg. 31P NMR分析发现,黏土覆盖使有机磷中的DNA-P、焦磷酸盐和单脂磷的含量分别减少47.0%、36.8%和31.3%.扫描电镜能谱分析发现,沉积物表层附着的白色絮状物质主要为钙结合态磷.以上分析初步表明,磷形态转化机制是由于材料中具有较高的活性钙含量,竞争吸附沉积物中的活性磷,材料覆盖沉积物表层后改变了沉积物界面环境,促进了表层沉积物的活性磷向钙结合态磷(Ca-P)转化.     

Catalytic degradation of PP with an Fe/activated carbon catalyst

We investigated the function of Fe and activated carbon (AC) as a catalyst by comparing Fe/AC with Fe/SiO₂ or AC, and also the effect of H₂ as a reaction gas on the product distribution in the catalytic degradation of polypropylene. Supported Fe promotes H₂ consumption to decompose solid residues, and AC support degrades heavy oil to produce light oil. As a result, using Fe/AC as a catalyst gives the maximum yield of the liquid product. For the reaction conditions, with a high reaction temperature or a long reaction time, the product distribution is more influenced by the thermal degradation than by the catalytic degradation. For the amount of Fe to load, 5wt% is the optimum condition in our reaction system. We demonstrated the mechanism of the degradation of polyolefins with hydrogen-capping catalysts.     

Nitrogen reduction using bioreactive thin-layer capping (BTC) with biozeolite: A field experiment in a eutrophic river

Bioreactive thin-layer capping (BTC) with biozeolite provides a potential remediation design that can sustainably treat N contamination from sediment and overlying water in eutrophic water bodies. Nitrogen (N) reduction using BTC with biozeolite was examined in a field incubation experiment in a eutrophic river in Yangzhou, Jiangsu Province, China. The biozeolite was zeolite with attached bacteria, including two isolated heterotrophic nitrifiers (Bacillus spp.) and two isolated aerobic denitrifiers (Acinetobacter spp.). The results showed that the total nitrogen (TN) reduction efficiency of the overlying water by BTC with biozeolite (with thickness of about 2 mm) reached a maximum (56.69%) at day 34, and simultaneous heterotrophic nitrification and aerobic denitrification occurred in the BTC system until day 34. There was a significant difference in the TN concentrations of the overlying water between biozeolite capping and control (t-test; p < 0.05). The biozeolite had very strong in situ bioregeneration ability. Carbon was the main source of nitrifier growth. However, both dissolved oxygen (DO) and carbon concentrations affected denitrifier growth. In particular, DO concentrations greater than 3 mg/L inhibited denitrifier growth. Therefore, BTC with biozeolite was found to be a feasible technique to reduce N in a eutrophic river. However, it is necessary to further strengthen the adaptability of aerobic denitrifiers through changing domestication methods or conditions.     

覆盖条件下底泥微环境对内源磷释放的影响

底泥微环境对内源磷释放有重要的影响.本研究对比了2种不同的原位覆盖材料对底泥微环境的影响以及内源磷释放的控制效果,沉积物微环境以间隙水中NH₄⁺-N、Fe²⁺浓度和微生物活性来表示.结果表明,CaO₂改性材料（ACPM）覆盖条件下较锁磷剂（Phoslock^®）组NH₄⁺-N和Fe²⁺浓度均处于较低状态,微生物活性值FDA增加了42.57%,说明其微生物活性较高,也显示了ACPM覆盖下其氧化还原电位高于Phoslock^®,且底泥微环境处于好氧状态.与Phoslock^®组相比,ACPM组上覆水和间隙水中DIP浓度均较高,表明Phoslock^®对磷酸盐的吸附能力优于ACPM,也暗示了底泥微环境并不是磷吸附的唯一衡量标准.在内源磷固定过程中,2种覆盖材料均有利于内源磷的固定,Ca-P均显著增加.然而,具有氧化性的ACPM导致NH₄Cl-P增加,Fe/Al-P大量减少,促进了活性磷的释放,使得底泥中的磷向覆盖层迁移,有利于清洁底泥.     

锆改性高岭土覆盖对底泥与上覆水之间磷迁移转化的影响

以无覆盖和高岭土覆盖作为对照,通过底泥磷释放控制模拟实验考察了厌氧条件下锆改性高岭土覆盖对重污染河道底泥与上覆水之间磷迁移转化的影响.结果表明,厌氧条件下,重污染河道底泥会释放出大量的磷进入上覆水中,且所释放出来的磷主要以溶解性磷酸盐为主.高岭土覆盖可以略微降低底泥磷向上覆水迁移的通量,而锆改性高岭土覆盖则可以极大降低底泥磷向上覆水迁移的通量.被高岭土覆盖层所吸附的磷中29%以氧化还原敏感态磷(BD-P)形式存在和63%以残渣态磷(Res-P)形式存在.被锆改性高岭土覆盖层所吸附的磷中绝大部分(90%)以金属氧化物结合态磷(NaOH-P)和Res-P形式存在,厌氧状态下很难被重新释放出来进入上覆水体.与无覆盖相比,厌氧条件下锆改性高岭土覆盖不仅不会促进底泥BD-P的释放,而且还会促进底泥NaOH-P的形成.X射线光电子能谱(XPS)和固相31P核磁共振(NMR)技术分析证实了锆改性高岭土覆盖层吸附水中磷酸盐的主要机制为配位体交换和形成内配合物.上述结果说明锆改性高岭土适合作为一种活性覆盖材料控制重污染河道底泥磷的释放.