Nonionic surfactant enhanced biodegradation of m-xylene by mixed bacteria and its application in biotrickling filter

In this study, m-xylene biodegradation was examined in bacteria-water mixed solution and biotrickling filter (BTF) systems amended with the nonionic surfactant Tween 80. The mixed bacteria were obtained from the activated sludge of a coking plant through a multisubstrate acclimatization process. High-throughput sequencing analysis revealed that Rhodanobacter sp. was the dominant species among the mixed bacteria. In the bacteria-water mixed solution, the bacterial density increased with increasing Tween 80 concentration. Hence, Tween 80 could be utilized as substrate by the mixed bacteria. Tween 80, with concentrations of 50–100 mg L^?1, could enhance the bioavailability of m-xylene and consequently improve the degradation efficiency of m-xylene. However, further increasing the initial concentration of Tween 80 would decrease the degradation efficiency of m-xylene. At concentrations exceeding 100 mg L^?1, Tween 80 was preferentially degraded by the mixed bacteria over m-xylene. In BTF systems, when the m-xylene inlet concentration was 1200 mg m^?3 and the empty bed residence time was 20 sec, the removal efficiency and elimination capacity of BTF1 with Tween 80 addition were at most 20% and 24% higher than those of BTF2 without Tween 80 addition. Overall, the integrated application of the mixed bacteria and surfactant was demonstrated to be a highly effective strategy for m-xylene waste gas treatment.

Implications: The integrated application of mixed bacteria and surfactant was demonstrated to be a promising approach for the highly efficient removal of m-xylene. Surfactant can activate mixed bacteria to degrade m-xylene by increasing its bioavailability. Besides, surfactant can be utilized as carbon source by the mixed bacteria so that the growth of mixed bacteria can be promoted. It is expected that the integrated application of both technologies will become more common in future chemical industry.     

Soil conservation practices and production efficiency of smallholder farms in Central China

The aim of this paper is to evaluate and analyze the impact of adoption of soil conservation practices (SCPs) on the technical efficiency of smallholder rice producers in Central China. We address self-selection bias and unobserved heterogeneity problems by estimating a switching regression model for the adoption decision function and separate stochastic production frontiers for SCP and Conventional farms while allowing for production inefficiency. SCP farms exhibit statistically higher average technical efficiency than Conventional farms. Education, extension services, membership in cooperatives, access to credit, and alternative income sources are positively and significantly associated with technical efficiency for both groups. Conventional farms display higher partial output elasticity for land, while only SCP farms show significant elasticity for capital.     

环保监测应急系统的发展及应用分析

随着我国社会的不断发展,人们生活水平的不断提高,人们对于资源的索取以及对环境的污染、生态的破坏都愈发的严重,雾霾、酸雨等极端、恶劣的天气频发,对人们的日常生活带来了严重的影响。近些年我国也逐渐开始意识到环境污染的严重后果,开始采取相应的环保监测以及环保措施来保护我们赖以生存的环境,而环保监测应急系统的运用就是其中之一。本文就针对环保监测应急系统在我国的发展以及应用进行了分析,并就其存在的问题以及注意事项进行了阐述,旨在为我国创造良好的生态环境提供一点帮助。     

太湖入湖河流中精神活性物质污染特征与生态风险

精神活性物质是一类摄入人体后对中枢神经系统具有强烈兴奋或抑制作用的新型污染物,其在水环境中的存在可能对水生生物、水生态系统甚至人体健康产生潜在的危害。为评价太湖中精神活性物质的污染水平和生态风险,利用超高效液相色谱-质谱联用法检测了太湖19条入湖河流中13种典型精神活性物质的质量浓度和空间分布规律。结果表明,在太湖19条入湖河流中除苯甲酰牙子碱(BE)和去甲氯胺酮(NK)外,其余11种目标物均有检出,质量浓度范围为n.d.～43.2 ng·L~(-1)。其中麻黄碱(EPH)的检出率和中间浓度最高,分别为100%和11.0 ng·L~(-1);其次为甲基苯丙胺(METH),检出频率为58%,浓度中值为1.0 ng·L~(-1);苯丙胺(AMP)在东部湖区均未检出。大部分精神活性物质浓度水平较高的河流分布在竺山湾和西太湖,而海洛因(HR)的高值区主要在南太湖。运用风险熵方法对其进行风险评估,结果显示,太湖流域地表水中检出的13种精神活性物质的风险熵值均<0.1,生态风险较低,但其对水生生态系统的长期和综合风险值得关注。     

化学品固有生物降解性试验OECD标准方法的适用性检验与改进

在经济合作与发展组织(Organization for Economic Co-operation and Development,OECD)颁布的3项固有生物降解标准测试方法中,改进的MITI(Ⅱ)(OECD 302C)方法因适用于难溶、易吸附和弱挥发等物质的固有生物降解性评估,成为目前适用范围较为广的方法。但OECD 302C对接种物规定特殊,需周期性采集不少于10个位点、不同类型的接种物进行驯养,采集、驯养和维持成本及操作复杂程度相对高,而OECD 302C方法获取的化学品生物降解率并未优于其他2项固有生物降解方法。因此,对10位点采集并驯养不同时间的接种物及污水处理厂曝气池采集的活性污泥进行微生物学特征比较,采用Biolog微生物鉴定系统及磷脂脂肪酸分析系统研究2种不同接种物的代谢活性及群落多样性,同时比较2种接种物对6种化学品的固有生物降解能力。结果表明,驯养接种物在驯养14 d后,活性与多样性开始下降,与真实环境来源接种物(10位点采集且未驯养接种物,即驯养0 d的接种物)的微生物群落差别较大。驯养1个月后的接种物在碳源利用活性、降解能力上与污水处理厂曝气池新鲜采集的活性污泥无明显差异。故笔者认为,在试验条件下,OECD 302C标准方法中的驯养接种物未达到预期目的,未经驯养的活性污泥更能反映真实环境,未来可以活性污泥作为该方法的接种物进行后续降解方法改进的研究。     

Quantification of pesticide residues on plastic mulching films in typical farmlands of the North China

• Pesticide residuals on mulching film of Shandong, Tianjin and Hebei. • Detected 29 pesticides in soil and 30 in mulching film. • Pesticides on plastic films: 86.4‒22213.2 ng/g and in soil: 9.3‒535.3 ng/g. • Pesticides on plastic films 20 times higher than in soil. Plastic debris as new pollutants attracts much attention in the recent years. The plastic mulching films is one of the most important plastic debirs source in the environment. The aim of this work was to investigate the current status of pesticide residues on the plastic mulching films. Based on the QuEChERS method, multi-residue methods for detection of pesticide residues with gas chromatography tandem mass spectrum (GC-MS) and high performance liquid chromatography tandem mass spectrum (HPLC-MS) were developed for the analysis of the pesticides residues in plastic film and soil samples from Tianjin, Hebei and Shandong. The total concentrations of pesticide residues were in the range of 86.4‒22213.2 ng/g in plastic film debris, which was about 20 times higher than that in soil (9.3‒535.3 ng/g). Residual level of pesticides varied greatly in different samples. The historical usage and recent application of pesticides were the main sources for pesticide residues on plastic films and soil. In short, plastic mulching films could act as a sink for pesticides in farmland and the ubiquitous pesticide residues on plastic films should draw more attention.     

京津冀生态文明与城市化协调发展的时序与空间演变

构建反映生态文明与城市化发展内涵的两系统评价指标体系,以均方差决策法、耦合协调度模型、探索性空间数据分析(ESDA),借助Arc GIS软件从时间和空间两个维度定量分析京津冀13市2007—2016年生态文明与城市化的耦合协调关系及变化趋势。结果表明:①生态文明与城市化系统耦合协调度逐年提升,从2007年13市均处于拮抗发展阶段,到2016年实现较低水平协调,多数城市生态文明建设滞后于城市化进程。②生态文明与城市化耦合协调发展水平存在显著的全局正向空间自相关性,局部空间自相关性存在显著的空间集聚特征,处于高-高集聚区与低-低集聚区的城市最多,北京、廊坊和保定三地的局部空间自相关性最为显著,此三地对周围临近城市的辐射能力更强。基于分析结论,提出实现京津冀13市生态文明与城市化高质量耦合协调发展的策略:①将生态文明建设融入城市化进程,强力推进京津冀"弱势区域"生态文明建设与城市化"同频共振",推动京津两地优势资源向河北溢出和辐射。②强化三地的区域协作,促进共同发展,充分利用高水平集聚区的示范效应,带动和提升低水平集聚区协调发展,加强三地环境治理的联防联控,构建共建共治发展平台。③根据耦合协调度"中间高、南北低"的空间分布差异,三地政府还需根据自身特色,因地制宜研判和明确发展策略。     

MIEX树脂在饮用水预处理中的应用研究

本文采用一种新型的MIEX磁性离子交换树脂对某水厂原水进行预处理,考察了MIEX树脂用量与后续混凝工艺对原水的浊度、有机物、无机阴离子的去除效果。结果表明,MIEX技术可有效地去除原水中的有机物,对UV254和CODMn的去除率分别稳定在90%和59%。MIEX树脂对无机阴离子也有很好的去除效果,对SO24-的去除率一般为80%以上,NO3-为50%以上。但MIEX树脂对低浊水的去浊效果一般,同时MIEX预处理可以有效强化混凝沉淀对有机物的去除。     

基于人工神经网络的街道峡谷NO_x浓度的数值模型研究

通过对反向传播人工神经网络的算法和网络结构的研究,发现拟牛顿算法训练速度较快,能够较好地接近误差目标值,同时建立了包括输入层、隐含层、输出层的人工神经网络三层拓扑结构。通过对街道峡谷人工神经网络的训练,模拟计算了街道峡谷NOx浓度分布值。结果显示,训练误差和测试误差比为1.11,训练样本的模拟值与实测值的相关系数为0.93,测试样本的模拟值与实测值的相关系数为0.87,模拟值与实测值的相关系数均高于显著水平为α=0.05与α=0.01所对应检验性表的相关系数临界值。该模型能够用于街道峡谷污染物浓度的模拟计算,具有较好的泛化能力。