Assessment of in situ biodegradation of monochlorobenzene in contaminated groundwater treated in a constructed wetland

The degradation of monochlorobenzene (MCB) was assessed in a constructed wetland treating MCB contaminated groundwater using a detailed geochemical characterisation, stable isotope composition analysis and in situ microcosm experiments. A correlation between ferrous iron mobilisation, decreasing MCB concentration and enrichment in carbon isotope composition was visible at increasing distance from the inflow point, indicating biodegradation of MCB in the wetland. Additionally, in situ microcosm systems loaded with 13C-labelled MCB were deployed for the first time in sediments to investigate the biotransformation of MCB. Incorporation of 13C-labelled carbon derived from the MCB into bacterial fatty acids substantiated in situ degradation of MCB. The detection of 13C-labelled benzene indicated reductive dehalogenation of MCB. This integrated approach indicated the natural attenuation of the MCB in a wetland system. Further investigations are required to document and optimise the in situ biodegradation of MCB in constructed and natural wetland systems treating contaminated groundwater.     

Endocrine modulation and toxic effects of two commonly used UV screens on the aquatic invertebrates Potamopyrgus antipodarum and Lumbriculus variegatus

The two UV screens 3-benzylidene-camphor (3-BC) and 3-(4'-methylbenzylidene)-camphor (4-MBC) were tested regarding their toxicity and estrogenic activity. The Yeast Estrogen Screen (YES) and two sediment assays with the freshwater invertebrates Lumbriculus variegatus and Potamopyrgus antipodarum were performed. In the YES, both substances activated the human estrogen receptor alpha with EC50 values of 44.2 microM for 3-BC and 44.3 microM for 4-MBC, whereby 4-MBC attained only 8% of the maximal response of 17beta-estradiol. For P. antipodarum embryo production increased after exposure to both substances (EC50 of 4.60 microM 4-MBC=1.17 mg kg(-1)dw) while mortality increased at high concentrations. The reproduction of L. variegatus was decreased by 3-BC with an EC50 of 5.95 microM (=1.43 mg kg(-1)dw) and also by 4-MBC, where no EC50 could be calculated. While reproduction decreased, the worms' weight increased after exposure to 3-BC with an EC50 of 26.9 microM (=6.46 mg kg(-1) dw), hence the total biomass remained unaffected.     

An indicator for effects of organic toxicants on lotic invertebrate communities: Independence of confounding environmental factors over an extensive river continuum

Distinguishing between effects of natural and anthropogenic environmental factors on ecosystems is a fundamental problem in environmental science. In river systems the longitudinal gradient of environmental factors is one of the most relevant sources of dissimilarity between communities that could be confounded with anthropogenic disturbances. To test the hypothesis that in macroinvertebrate communities the distribution of species' sensitivity to organic toxicants is independent of natural longitudinal factors, but depends on contamination with organic toxicants, we analysed the relationship between community sensitivity SPEAR_organic (average community sensitivity to organic toxicants) and natural and anthropogenic environmental factors in a large-scale river system, from alpine streams to a lowland river. The results show that SPEAR_organic is largely independent of natural longitudinal factors, but strongly dependent on contamination with organic toxicants (petrochemicals and synthetic surfactants). Usage of SPEAR_organic as a stressor-specific longitude-independent measure will facilitate detection of community disturbance by organic toxicants.     

Detecting and correcting sensor drifts in long-term weather data

Quality control of long-term monitoring data of thousands and millions of individual records as present in meteorological data is cumbersome. In such data series, sensor drifts, stalled values, and scale shifts may occur and potentially result in flawed conclusions if not noticed and handled properly. However, there is no established standard procedure to perform quality control of high-frequency meteorological data. In this paper, we outline a procedure to remove sensor drift in high-frequency data series using the example of 15-year-long sets of hourly relative humidity (RH) data from 28 stations subdivided into 202 individual sensor operation periods. The procedure involves basic quality control, relative homogeneity testing, and drift removal. Significant sensor drifts were observed in 40.6 % of all sensor operation periods. The drifts varied between data series and depended in a complex, usually inconsistent way on absolute RH values; within single series for instance, a drift could be negative in the lower RH range and positive in the upper RH range. Detrending changed RH values by, on average, 1.96 %. For one fifth of the detrended data, adjustments were 2.75 % and more of the measured value, and in one tenth 4.75 % and more. Overall, drifts were strongest for RH values close to 100 %. The detrending procedure proved to effectively remove sensor drifts. The principles of the procedure also apply to other meteorological parameters and more generally to any time series of data for which comparable reference data are available.     

Untersuchungen zum ?kotoxikologischen Sch?digungspotenzial und Erosionsrisiko von kontaminierten Sedimenten in staugeregelten Flüssen

Schwebstoffgebundene Schadstoffe werden durch Sedimentation der Wasserphase und damit der Verfügbarkeit für viele aquatischen Organismen entzogen. W?hrend bei durchschnittlichen hydrologischen. Verh?ltnissen die Freisetzung von Schadstoffen aus stabil gelagerten Sedimenten meist weitgehend unterbunden wird, besteht bei Hochwassereignissen die Gefahr einer Remobilisierung von kontaminierten Ablagerungen. In diesem Beitrag wird ein kombiniertes ?kotoxikologisches und hydraulisches Untersuchungssystem zur Untersuchung der ?kotoxikologischen Belastung und des Erosionsrisikos von Sedimenten vorgestellt. Der integrierte Ansatz wurde am staugeregelten Neckar angewendet, um das Sch?digungspotenzial und die Gefahr einer Remobilisierung an Sedimentbohrkernen der Stauhaltung Lauffen sowie an Schwebstoffen zweier extremer Hochwasser zu überprüfen. Für die Bohrkernsegmente unterhalb einer Erosionsdiskordanz konnte eine sprunghafte Zunahme der ?kotoxikologischen Belastung ermittelt werden. Bei Hochwasserereignissen mit einer 5-j?hrlichen Wiederkehrwahrscheinlichkeit (=HQ₅) k?nnen prinzipiell alle Sedimente, auch die st?rker kontaminierten und erosionsresistenteren Altsedimente, remobilisiert werden. W?hrend der Hochwasserereignisse (HQ₁₅ bis HQ₂₀) kam es zu einer deutlichen Erh?hung des cytotoxischen und mutagenen Sch?digungspotenzials der Schwebstoffe im Vergleich zu einem mittleren Hochwasser im Jahre 1995/96 (HQ₁) Dies schien zumindest teilweise auf die Remobilisierung hochkontaminierter Altsedimente zurückzuführen zu sein.     

Temporal Segmentation of Human Short-Term Behavior in Everyday Activities and Interview Sessions

 Human behavior is structured by serial order and timing of functionally related groups of movements with a duration of a few seconds. These elementary action units have been described in ethological studies during unstaged everyday behavior, but not during interview sessions. Psychomotor alterations are relevant for differential diagnosis and treatment, and psychiatric patients are generally evaluated during interview sessions. Therefore the time structure of upper limb movements (n=764) of healthy subjects (n=22) were studied using videotaped interviews and frame-by-frame analysis and compared to movements (n=530) of unstaged human everyday behavior (n=154). The number of action units, but not their duration, was correlated inversely with self-reported impairment of mood and pleasure experience in healthy persons. The temporal distribution of movements in interview sessions did not differ from the time patterns of everyday behavior. This method could be a promising tool to investigate time patterns of movements and psychomotor alterations in psychiatric patients during interview sessions. Received: 29 October 1998 / Accepted in revised form: 29 December 1998     

激光诱导荧光技术测量大气OH自由基的研究进展

大气氢氧自由基（ＯＨ）是对流层大气中最重要的氧化剂，对酸雨，平流层臭氧的损耗等有重要影响，激光诱导荧光技术是目前测定大气ＯＨ自由基中使用最多的测量方法。文章总结了２０多年来国内外的研究成果，论述了激光诱导荧光技术用于测定大气ＯＨ自由基的基本原理和研究进展，讨论了测量中不确定因素及其对策，并着重介绍了目前最常用的基于气体扩张的低压荧光技术。     

Photocatalytic degradation of trinitrotoluene and other nitroaromatic compounds

The photocatalytic degradation of 2,4,6-trinitrotoluene and ten other nitroaromatic compounds in aerated TiO₂ suspensions has been studied. The following order of reactivity was observed: nitrotoluenes > nitrobenzene > dinitrotoluenes . dinitrobenzenes > 2,4,6-trinitrotoluene > 1,3,5-trinitrobenzene, which reflects the known influence of nitro groups towards the attack of electrophilic reagents on the aromatic molecule.