Organic matter produced by algae and cyanobacteria: Quantitative and qualitative characterization

This work aims at characterizing organic matter produced by an alga Euglena gracilis and a cyanobacteria Microcystis aeruginosa and assessing the evolution of its characteristics during growth. A culture medium was optimized. The species growth phases were monitored using both visible spectrophotometry and flow cytometry cell counting. Organic matter fractionation according to hydrophobicity and specific UV absorbance (SUVA) index were used to specifically characterize the produced algal organic matter (AOM). The AOM characteristics were both growth phase and species dependent. However, a similar evolution was observed. The hydrophilic fraction (HPI) was the major fraction whatever the growth phases and was almost the only one produced during lag and exponential phases. It represented around 75% of AOM during exponential phase and then decreased when the stationary phase appeared. It represented 46% and 60% of the AOM during late decline phase for the cyanobacteria and the alga respectively. The hydrophobic (HPO) and transphilic (TPH) fractions started to appear from the beginning of the stationary phase with more hydrophobic compounds coming from intracellular organic material of dying cells. HPO and TPH percentages still increased during the decline phase probably because of two additional processes: photo-dissolution and leaching of particulate organic matter from cells fragments. A comparison of AOM during late decline phase and natural organic matter (NOM) from Glane River (France) underlined that AOM was more hydrophilic and presented a lower SUVA for each fractions than NOM. However, the difference between NOM and AOM hydrophobicity narrowed during decline phase.     

实验室老化设备

介绍人工老化试验设备中最常用的几种光源的产生、发展、结构和特点，并从与自然光源相似程度的角度，分析了几种光源的优缺点。     

Biodegradability of the antioxidant diaryl-p-phenylene diamine using a modified inherent biodegradation method at an environmentally relevant concentration

The chemical product diaryl-p-phenylene diamine (DAPD), produced by The Goodyear Tire & Rubber Company as POLYSTAY 100® (CAS 68953-84-4), is employed as an antidegradant in polymers used in tires and industrial rubber products. Previous evaluations pertaining to the ecological fate of DAPD indicated a lack of biodegradative activity in aquatic media. In order to further pursue the biodegradation potential of DAPD, it was deemed necessary to enhance the sensitivity of the aquatic biodegradation assay through (a) employment of a radiotracer of the test substance, and (b) optimisation of conditions for achieving maximal solubilisation of test material in the aquatic media of the incubation vessels. Test vessels were prepared according to the OECD ready biodegradability test guidelines, with DAPD added on silica gel at concentrations of 10 or 100 μg L⁻¹, together with a surfactant to aid solubilisation. After 63 d incubation up to 37% mineralisation was measured and up to 29% of the applied radioactivity was incorporated into cell biomass. Also, after 28 d no DAPD could be measured in solution by radio-TLC and HPLC–MS. These three results demonstrate that the antioxidant DAPD undergoes microbiologically mediated biodegradation and is highly unlikely to persist in the environment.     

Application of Prevention through Design for hearing loss in the mining industry

INTRODUCTION: Overexposure to noise remains a widespread and serious health hazard in the U.S. service providing and goods producing industries. Excessive noise can lead to poor verbal communication and reduce the ability to recognize warning signals. These dangerous work conditions can also cause stress and fatigue. Occupational hearing loss is a permanent illness, with no recovery currently possible. METHOD: National Institute for Occupational Safety and Health (NIOSH) has recognized Noise Induced Hearing Loss (NIHL) as one of the ten leading work-related diseases and injuries in the United States, and has emphasized its importance as one of the critical areas expressed in the National Occupational Research Agenda. RESULTS: One of the most serious noise problems in the goods producing industries is the operation of continuous mining machines during underground coal mining. In order to minimize occupational hearing loss, noise hazards are "designed out" early in the design process. NIOSH is leading a national initiative called Prevention through Design (PTD) to promote this concept. This paper describes the quiet-by-design approach of a noise control that reduced noise exposures of continuous mining machine operators by 3dB(A) using the four functional areas of PTD, namely Practice, Policy, Research, and Education.     

Diffusion-controlled toluene reference material for VOC emissions testing: International interlaboratory study

The measurement of volatile organic compound (VOC) emissions from building products and materials by manufacturers and testing laboratories, and the use of the test results for labeling programs, continue to expand. One issue that hinders wide acceptance for chamber product testing is the lack of a reference material to validate test chamber performance. To meet this need, the National Institute of Standards and Technology (NIST) and Virginia Tech (VT) have developed a prototype reference material that emits a single VOC similar to the emissions of a diffusion-controlled building product source with a dynamic emissions profile. The prototype material has undergone extensive testing at NIST and a pilot interlaboratory study (ILS) with four laboratories. The next development step is an evaluation of the prototype source in multiple-sized chambers of 14 laboratories in seven countries. Each laboratory was provided duplicate specimens and a test protocol. Study results identified significant issues related to the need to store the source at a subzero Celsius temperature until tested and possible inconsistencies in large chambers. For laboratories using a small chamber and meeting all the test method criteria, the results were very encouraging with relative standard deviations ranging from 5% to 10% across the laboratories.

Implications: Currently, the chamber performance of laboratories conducting product VOC emissions testing is assessed through interlaboratory studies (ILS) using a source with an unknown emission rate. As a result, laboratory proficiency can only be based on the mean and standard deviation of emission rates measured by the participating ILS laboratories. A reference material with a known emission rate has the potential to provide an independent assessment of laboratory performance as well as improve the quality of interlaboratory studies. Several international laboratories with different chamber testing systems demonstrated the ability to measure the emission rate of such a reference material within an acceptable measurement uncertainty.     

Spatial variation in atmospheric nitrogen deposition on low canopy vegetation

Current knowledge about the spatial variation of atmospheric nitrogen deposition on a local scale is limited, especially for vegetation with a low canopy. We measured nitrogen deposition on artificial vegetation at variable distances of local nitrogen emitting sources in three nature reserves in the Netherlands, differing in the intensity of agricultural practices in the surroundings. In the nature reserve located in the most intensive agricultural region nitrogen deposition decreased with increasing distance to the local farms, until at a distance of 1500 m from the local nitrogen emitting sources the background level of 15 kg N ha(-1) yr(-1) was reached. No such trend was observed in the other two reserves. Interception was considerably lower than in woodlands and hence affected areas were larger. The results are discussed in relation to the prospects for the conservation or restoration of endangered vegetation types of nutrient-poor soil conditions.     

Secondary mobilisation of heavy metals in overbank sediments

Heavy metal mobility was studied in overbank sediments of the Grote Beek river in Central Belgium. The geochemical signature of heavy metals in fine-scale sampled overbank sediments was compared with data on heavy metal emission into the river. The influence of acidification, organic and inorganic complexation on heavy metal mobility in overbank sediments was studied by single and sequential extractions and leaching tests. As confirmed by these tests, the elevated CaCl(2) content of the river water significantly enhanced the mobilisation of especially Cd, while Zn was mobilised to a lesser extent. The mobilisation of As on the other hand decreased in the presence of elevated CaCl(2) concentrations. Based on the results of single extractions, two highly contaminated zones with a different Cd mobility were observed in one of the overbank profiles. A detailed investigation of Cd leaching behaviour in the zone of Fe-accumulation during pH(stat) leaching tests, suggested that it was related to the association of Cd with Fe-oxides, while adsorption was the dominant binding form of Cd in the clay-rich part of the overbank sediment profile.