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T.Z. Lerch M.-F. Dignac N. Nunan E. Barriuso A. Mariotti 《Environmental pollution (Barking, Essex : 1987)》2009,157(11):2985-2993
The biodegradation of nonextractable residues (NER) of pesticides in soil is still poorly understood. The aim of this study was to evaluate the influence of NER ageing and fresh soil addition on the microbial communities responsible for their mineralisation. Soil containing either 15 or 90-day-old NER of 13C-2,4-D (NER15 and NER90, respectively) was incubated for 90 days with or without fresh soil. The addition of fresh soil had no effect on the mineralisation of NER90 or of SOM, but increased the extent and rate of NER15 mineralisation. The analyses of 13C-enriched FAME (fatty acids methyl esters) profiles showed that the fresh soil amendment only influenced the amount and structure of microbial populations responsible for the biodegradation of NER15. By coupling biological and chemical analyses, we gained some insight into the nature and the biodegradability of pesticide NER. 相似文献
453.
The global gold market has recently attracted a lot of attention and the price of gold is relatively higher than its historical trend. For mining companies to mitigate risk and uncertainty in gold price fluctuations, make hedging, future investment and evaluation decisions, depend on forecasting future price trends. The first section of this paper reviews the world gold market and the historical trend of gold prices from January 1968 to December 2008. This is followed by an investigation into the relationship between gold price and other key influencing variables, such as oil price and global inflation over the last 40 years. The second section applies a modified econometric version of the long-term trend reverting jump and dip diffusion model for forecasting natural-resource commodity prices. This method addresses the deficiencies of previous models, such as jumps and dips as parameters and unit root test for long-term trends. The model proposes that historical data of mineral commodities have three terms to demonstrate fluctuation of prices: a long-term trend reversion component, a diffusion component and a jump or dip component. The model calculates each term individually to estimate future prices of mineral commodities. The study validates the model and estimates the gold price for the next 10 years, based on monthly historical data of nominal gold price. 相似文献
454.
Christian P. Andersen Wilma Ritter Rainer Matyssek 《Environmental pollution (Barking, Essex : 1987)》2010,158(8):2604-2609
Canopies of adult European beech (Fagus sylvatica) and Norway spruce (Picea abies) were labeled with CO2 depleted in 13C to evaluate carbon allocation belowground. One-half the trees were exposed to elevated O3 for 6 yrs prior to and during the experiment. Soil-gas sampling wells were placed at 8 and 15 cm and soil CO2 was sampled during labeling in mid-late August, 2006. In beech, δ13CO2 at both depths decreased approximately 50 h after labeling, reflecting rapid translocation of fixed C to roots and release through respiration. In spruce, label was detected in fine-root tissue, but there was no evidence of label in δ13CO2. The results show that C fixed in the canopy rapidly reaches respiratory pools in beech roots, and suggest that spruce may allocate very little of recently-fixed carbon into root respiration during late summer. A change in carbon allocation belowground due to long-term O3 exposure was not observed. 相似文献
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针对氨氮排放对环境造成的污染以及给人类带来的危害这一问题,将分子筛吸附与膜技术相结合,以13x分子筛为功能颗粒,以聚醚砜(PES)为膜的基质材料,以二甲基乙酰胺(DMAc)为溶剂,通过相转化法制备了不同13x分子筛填充量的13x/PEs膜吸附剂。研究发现,随着13x分子筛填充量的增加,膜的指状孔变得细密、短小,其吸附容量,断裂强度都在增加,但是水通量逐渐降低。料液温度与pH值对吸附性能的影响表明,该膜吸附剂在293K,pH=7时对氨氮有较好的吸附容量,可达21.69mg/g;吸附热力学研究表明,该类型膜吸附剂对氨氮的吸附等温线符合Langmuir方程。 相似文献
459.
选取白洋淀的沼泽区(烧车淀)与开阔水域区(采蒲台)为研究区域,分析了水体中新生沉降颗粒物组分组成、沉降通量及其来源.结果表明,两种典型水域中水体颗粒物组分差异显著,其中,烧车淀水域颗粒物成分以有机质(OM)为主,质量占比达到49.59%~74.14%;而采蒲台水域颗粒物以无机组分为主,占比为54.52%~79.27%.烧车淀沉降颗粒物中总碳(TC)、总氮(TN)含量分别为(221.16±39.73)g·kg-1和(21.10±1.67)g·kg-1;采蒲台沉降颗粒物中TC和TN的含量分别为(172.28±91.22)g·kg-1和(15.72±8.12)g·kg-1.由固相13C CP/MAS NMR光谱结果分析出白洋淀沉降颗粒物中碳组分以烷基碳、烷氧基碳为主,其中,烧车淀淀面水域颗粒物中以易分解碳烷氧基碳为主(65.65%),采蒲台淀面水域颗粒物中以较稳定烷基碳为主(50.76%).开阔水域区颗粒物沉降通量高于沼泽化区,均值分别为10.63 g·m-2·... 相似文献
460.
利用13X沸石分子筛净化含NH+4-N废水的实验研究 总被引:1,自引:0,他引:1
研究了13X沸石分子筛在静态和动态条件下对中低浓度含NH+4-N废水的吸附性能,包括影响吸附的主要因素、沸石对NH+4-N的吸附效果和沸石的再生等。静态实验结果表明,pH值为6.5~7.5,吸附时间35 min,吸附温度20~30℃的条件下,沸石对50 mL NH+4-N初始浓度(C0)为80 mg/L的废水吸附效果最佳,吸附过程符合Langmuir型吸附等温式,饱和吸附量为8.61 mg/g。动态条件下,随水力停留时间增加,沸石对NH+4-N的吸附量上升,最大饱和吸附量可达24.20 mg/g,吸附过程符合Thomas吸附模型。直接焙烧法对吸附后的沸石进行再生活化处理效果良好。实验证明,利用13X沸石净化中低浓度含NH+4-N废水具有良好的工业化应用前景。 相似文献