Effects of taxonomy,sediment, and water column on C:N:P stoichiometry of submerged macrophytes in Yangtze floodplain shallow lakes,China

Carbon (C), nitrogen (N) and phosphorus (P) are the three most important essential elements limiting growth of primary producers. Submerged macrophytes generally absorb nutrients from sediments by root uptake. However, the C:N:P stoichiometric signatures of plant tissue are affected by many additional factors such as taxonomy, nutrient availability, and light availability. We first revealed the relative importance of taxonomy, sediment, and water column on plant C:N:P stoichiometry using variance partitioning based on partial redundancy analyses. Results showed that taxonomy was the most important factor in determining C:N:P stoichiometry, then the water column and finally the sediment. In this study, a significant positive relationship was found between community C concentration and macrophyte community biomass, indicating that the local low C availability in macrophytes probably was the main reason why submerged macrophytes declined in Yangtze floodplain shallow lakes. Based on our study, it is suggested that submerged macrophytes in Yangtze floodplain shallow lakes are primarily limited by low light levels rather than nutrient availability.

     

用于污水再生利用的生物活性炭床的有机物降解特性

以微生物增殖动力学的基本方程-莫诺方程为出发点,通过氮同位素分析比较了具有同源性微生物的生物陶粒滤床和生物活性炭床的有机物生物降解规律,建立了生物活性炭床的有机物生物降解动力学方程,提出在污水再生利用过程中生物活性炭床符合高基质有机物降解动力学模型,即有机物降解呈一级反应动力学方程。以此方程为基础,分析计算了生物活性炭床沿炭床深度的吸附性能,结果表明,在生物活性炭床中,随生物功能的减弱,生物活性炭床对有机物的吸附能力逐渐加强。     

Characterization of the extracellular biodemulsifiers secreted by Bacillus cereus LH-6 and the enhancement of demulsifying efficiency by optimizing the cultivation conditions

A highly efficient demulsifying strain, LH-6, was isolated from petroleum-contaminated soil and identified as Bacillus cereus by 16S rDNA gene analysis. It achieved 95.61 and 95.40 % demulsifying ratios within 12 h for water-in-oil (W/O) and oil-in-water (O/W) model emulsions, respectively. Fourier transform infrared spectroscopy (FT-IR) and thin-layer chromatography (TLC) detections indicated that the LH-6’s extracellular biodemulsifiers were different types of lipopeptides for the W/O and O/W emulsions. Optimization of the culture medium composition was conducted to improve the biosynthesis and demulsifying efficiency of the biodemulsifier. The optimal carbon source was liquid paraffin, while waste frying oil could also be an alternative carbon source. The optimal nitrogen sources were ammonium sulfate and yeast extract. To further enhance the biodemulsifier efficiency, the optimal cultivation conditions were determined using response surface methodology (RSM) based on central composite rotation design (CCRD). Using the optimized cultivation conditions, the demulsifying ratios increased to 98.23 and 97.65 % for the W/O and O/W model emulsions, respectively.     

化学溶胀法分离废弃线路板中金属与基板

废弃线路板的粉碎和所含金属组分的高效解离是后续分选回收的前提条件。本研究分别使用乙二胺等10种溶剂浸泡废弃线路板，比较对线路板中铜箔与基板间剥离强度的影响，从而筛选出4种有代表性的溶剂，即溶剂D、溶剂F、丙酮和水, 比较废弃线路板经化学溶胀后的单体解离度和获得一定粒径分布的颗粒所需的破碎时间。研究结果表明，化学溶胀后破碎能大幅提高金属的单体解离度，浸泡效果的优良排序为：溶剂D>溶剂F>丙酮>水；浸泡时间越长，浸泡温度越高，对剥离强度的降低越有利；使用溶剂D在150℃、3 h或140℃、5 h的工艺下浸泡废弃线路板，可以使铜箔与基板自动脱落。研究结果为后续的分选提供了便利的条件。     

季节性城市生活垃圾成分分析及厌氧消化特性研究

城市生活垃圾的成分及特性随着季节和人类在不同季节的生活习惯而变化，针对我国北方城市研究了一年中不同季节的城市生活垃圾成分特点，对影响厌氧发酵过程的相关成分如总有机碳（TOC）、总氮（TN）、蛋白质、脂肪和还原糖等进行了测定分析。通过厌氧消化实验，测得不同季节城市生活垃圾pH值、日产气量、沼气甲烷含量、甲烷累积量、挥发性脂肪酸（VFAs）和氧化还原电位（ORP）等参数的变化规律，分析相应变化的影响因素。结果表明，二、三季度的含水率分别为64．81％和67．50％，高于一、四季度，一季度发酵原料中蛋白质和脂肪含量分别为12．56％和8．86％，明显高于其他3个季度。一季度甲烷累积量最高，达到17616mL，单位发酵原料的产气量为204．8mL／g，也是4个季度中最高的，说明蛋白质、脂肪等有机成分含量对厌氧发酵过程及结果影响比较明显。为进一步的城市生活垃圾厌氧消化制取生物燃气的工艺条件提供依据。     

1，4-二氯苯降解菌的分离及其降解特性研究

从某污水处理曝气池的活性污泥中分离出一株能够以1，4-二氯苯为唯一碳源和能源生长的菌株DEB-1，通过形态特征和生理生化试验初步鉴定为黄杆菌属（Flavobacterium sp.）。实验结果表明，该菌株最适降解温度为32℃、最适降解pH为7.8，24 h对100 mg/L的1，4-二氯苯的降解率达94.5%。菌株DEB-1的降解谱较广，对5种氯苯类物质具有较高的降解率。并进一步研究了DEB-1的1，4-二氯苯降解酶粗酶液的性质，其最适反应温度和pH分别为30℃和8.5。对处理含氯代芳香化合物的有机废水具有一定的意义。     

MicroRNA: a novel implication for damage and protection against ionizing radiation

Environmental Science and Pollution Research - Ionizing radiation (IR) is a form of high energy. It poses a serious threat to organisms, but radiotherapy is a key therapeutic strategy for various...     

Experimental study on static and dynamic mechanical properties of phosphogypsum

Environmental Science and Pollution Research - Phosphogypsum (PG) is a solid waste product of the wet-process phosphoric acid industry that accumulates in large amounts on the ground, forming PG...     

Iodine enrichment and the underlying mechanism in deep groundwater in the Cangzhou Region,North China

Environmental Science and Pollution Research - The lack of information on the origin and behavior of iodine in deep groundwater restricts the development and use of groundwater resources. To...     

How air pollution lowers the domestic value-added ratio in exports: an empirical study of China

Environmental Science and Pollution Research - This paper analyzes the theoretical mechanism and transmission channel for the impact of air pollution on firms’ domestic value-added ratio...