Phenylheptatriyne: Occurrence, synthesis, biological properties, and environmental concerns

In addition to a complete bibliography on the occurrence, synthesis, photochemistry, biological activity, and mechanism of phototoxicity of phenylheptatriyne, new data on its phototoxicity in larvae of the mosquito , in and in fish ( ) are presented. The apparent lack of target specificity suggests that additional research will be necessary before considering using PHT in field applications.     

Semicontinuous PM2.5 sulfate and nitrate measurements at an urban and a rural location in New York: PMTACS-NY summer 2001 and 2002 campaigns

Several collocated semicontinuous instruments measuring particulate matter with particle sizes < or =2.5 microm (PM2.5) sulfate (SO4(2-)) and nitrate (NO3-) were intercompared during two intensive field campaigns as part of the PM2.5 Technology Assessment and Characterization Study. The summer 2001 urban campaign in Queens, NY, and the summer 2002 rural campaign in upstate New York (Whiteface Mountain) hosted an operation of an Aerosol Mass Spectrometer, Ambient Particulate Sulfate and Nitrate Monitors, a Continuous Ambient Sulfate Monitor, and a Particle-Into-Liquid Sampler with Ion Chromatographs (PILS-IC). These instruments provided near real-time particulate SO4(2-) and NO3- mass concentration data, allowing the study of particulate SO4(2-)/NO3- diurnal patterns and detection of short-term events. Typical particulate SO4(2-) concentrations were comparable at both sites (ranging from 0 to 20 microg/m3), while ambient urban particulate NO3- concentrations ranged from 0 to 11 microg/m3 and rural NO3- concentration was typically less than 1 microg/m3. Results of the intercomparisons of the semicontinuous measurements are presented, as are results of the comparisons between the semicontinuous and time-integrated filter-based measurements. The comparisons at both sites, in most cases, indicated similar performance characteristics. In addition, charge balance calculations, based on major soluble ionic components of atmospheric aerosol from the PILS-IC and the filter measurements, indicated slightly acidic aerosol at both locations.     

Effect of gasoline formulation on the formation of photosmog: a box model study

Based on exhaust gas analyses from the combustion of five different types of gasoline in a passenger car operated on a chassis dynamometer, box model simulations of the irradiation of exhaust/NOx/air mixtures using an established chemical mechanism for a standardized photosmog scenario were performed. The fuel matrix used covered wide fractional ranges for paraffinic, olefinic, and aromatic hydrocarbons. Two fuels also contained methyl tertiary butyl ether (MTBE). The different O3 profiles calculated for each run were compared and interpreted. The O3 levels obtained were strongly influenced by the exhaust gas concentrations of aromatic and olefinic hydrocarbons. The higher exhaust content of these compounds caused higher O3 production in the smog system investigated. The conclusion of the present study is that the composition of gasoline cannot be taken directly for the estimation of the emissions' O3 creation potential from its combustion. Variation of the dilution in the different calculations showed evidence for an additional influence of transport effects. Accordingly, further detailed exhaust gas analyses followed by more complex modeling studies are necessary for a proper characterization of the relationship between fuel blend and gasoline combustion products.     

Biological dehalogenation and halogenation reactions

A large number of halogenated compounds is produced by chemical synthesis. Some of these compounds are very toxic and cause enormous problems to human health and to the environment. Investigations on the degradation of halocompounds by microorganisms have led to the detection of various dehalogenating enzymes catalyzing the removal of halogen atoms under aerobic and anaerobic conditions involving different mechanisms. On the other hand, more than 3500 halocompounds are known to be produced biologically, some of them in great amounts. Until 1997, only haloperoxidases were thought to be responsible for incorporation of halogen atoms into organic compounds. However, recent investigations into the biosynthesis of halogenated metabolites by bacteria have shown that a novel type of halogenating enzymes, FADH(2)-dependent halogenases, are involved in biosyntheses of halogenated metabolites. In every gene cluster coding for the biosynthesis of a halogenated metabolite, isolated so far, one or several genes for FADH(2)-dependent halogenases have been identified.     

Priming effects on PAH degradation and ecotoxicity during a phytoremediation experiment

An experiment was conducted to distinguish priming effects from the effects of phytoremediation of a creosote-polluted soil. The concentration of 13 polycyclic aromatic hydrocarbons (PAHs), and their combined soil toxicity (using four bioassays), was determined on recently excavated, homogenized soil and on such soil subjected to a time-course phytoremediation experiment with lucerne. The results showed a high priming effect, with minor positive and synergistic effects of planting and fertilization on PAH degradation rates. At the end of the experiment, PAH degradation reached 86% of the initial 519 mg PAHs kg(-1). Two of the four toxicity tests (bioluminescence inhibition and ostracod growth inhibition) corroborated the chemical data for residual PAHs, and indicated a significant reduction in soil toxicity. We conclude that priming effects can easily surpass treatment effects, and that an unintentional pre-incubation that ignores these effects can jeopardize the full quantitative assessment of in situ bioremediation of contaminated soil.     

Emissions of organophosphate and brominated flame retardants from selected consumer products and building materials

The emissions of selected flame retardants were measured in 1- and 0.02-m³ emission test chambers and 0.001-m³ emission test cells. Four product groups were of interest: insulating materials, assembly foam, upholstery/mattresses, and electronics equipment. The experiments were performed under constant environmental conditions (23°C, 50% RH) using a fixed sample surface area and controlled air flow rates. Tris (2-chloro-isopropyl)phosphate (TCPP) was observed to be one of the most commonly emitted organophosphate flame retardants in polyurethane foam applications. Depending on the sample type, area-specific emission rates (SER_a) of TCPP varied between 20 ng m⁻² h⁻¹ and 140 μg m⁻² h⁻¹.The emissions from electronic devices were measured at 60°C to simulate operating conditions. Under these conditions, unit specific emission rates (SER_u) of organophosphates were determined to be 10–85 ng unit⁻¹ h⁻¹. Increasing the temperature increased the emission of several flame retardants by up to a factor of 500. The results presented in this paper indicate that emissions of several brominated and organophosphate flame retardants are measurable. Polybrominated diphenylethers exhibited an SER_a of between 0.2 and 6.6 ng m⁻² h⁻¹ and an SER_u of between 0.6 and 14.2 ng unit⁻¹ h⁻¹. Because of sink effects, i.e., sorption to chamber components, the emission test chambers and cells used in this study have limited utility for substances low vapour pressures, especially the highly brominated compounds; hexabromocyclododecane had an SER_a of between 0.1 and 29 ng m⁻² h⁻¹ and decabromodiphenylether was not detectable at all.     

N:P ratios,light limitation,and cyanobacterial dominance in a subtropical lake impacted by non-point source nutrient pollution

A long-term (28-year) data set was used to investigate historical changes in concentrations of phosphorus (P), nitrogen (N), N:P ratios, and Secchi disk transparency in a shallow subtropical lake (Lake Okeechobee, Florida, USA). The aim was to evaluate changes in the risk of N2-fixing cyanobacterial blooms, which have infrequently occurred in the lake's pelagic zone. Predictions regarding bloom risk were based on previously published N:P ratio models. Temporal trends in the biomass of cyanobacteria were evaluated using phytoplankton data collected in 1974, 1989-1992, and 1997-2000. Concentrations of pelagic total P increased from near 50 microg l-1 in the mid-1970s to over 100 microg l-1 in the late 1990s. Coincidentally, the total N:P (mass) ratio decreased from 30:1 to below 15:1, and soluble N:P ratio decreased from 15:1 to near 6:1, in the lake water. Published empirical models predict that current conditions favor cyanobacteria. The observations confirm this prediction: cyanobacteria presently account for 50-80% of total phytoplankton biovolume. The historical decrease in TN:TP ratio in the lake can be attributed to a decreased TN:TP ratio in the inflow water and to a decline in the lake's assimilation of P, relative to N. Coincident with these declines in total and soluble N:P ratios, Secchi disk transparency declined from 0.6 m to near 0.3 m, possibly due to increased mineral turbidity in the lake water. Empirical models predict that under the turbid, low irradiance conditions that prevail in this lake, non-heterocystous cyanobacteria should dominate the phytoplankton. Our observations confirmed this prediction: non-N2-fixing taxa (primarily Oscillatoria and Lyngbya spp.) typically dominated the cyanobacteria community during the last decade. The only exception was a year with very low water levels, when heterocystous N2-fixing Anabaena became dominant. In the near-shore regions of this shallow lake, low N:P ratios potentially favor blooms of N2-fixing cyanobacteria, but their occurrence in the pelagic zone is restricted by low irradiance and lack of stable stratification.     

Halogenated compounds and climate change: future emission levels and reduction costs

OBJECTIVES: This work assesses the contribution to climate change resulting from emissions of the group of halogenated greenhouse gases. METHODS: A bottom-up emission model covering 22 technological sectors in four major regions is described. Emission estimates for 1996 and projection for 2010 and 2020 are presented. The costs for deep cuts into projected emission levels are calculated. RESULTS: The substances covered by this study have contributed emissions of 1100 +/- 800 MT CO2 equivalents per year in 1996. In terms of their relative contribution to emissions of CO2 equivalents, this corresponds to 3 +/- 2% of global emissions of all anthropogenic greenhouse gases. The wide range of uncertainty is due to the poorly quantified net global warming potential of the ozone depleting substances, which have an indirect cooling effect on climate through the destruction of stratospheric ozone. For annual emissions of HFCs, PFCs and SF6 (which are regulated under the Kyoto Protocol and for which global warming potentials are well defined), the relative contribution is projected to increase to 2% (600 MT CO2 eq.) of global greenhouse gas emissions by 2010. This trend is expected to continue, emissions are projected to grow to a contribution of roughly 3% (870 MT CO2 eq.) in 2020 compared to 0.9% (300 MT CO2 eq.) in 1996. For HFCs, PFCs and SF6, this study identifies global emission reduction potentials of 260 MT CO2 eq. per year in 2010 and 640 MT CO2 eq. per year in 2020 at below US$ 50 per ton. These values correspond to roughly 40% and 75% of projected emissions in 2010 and 2020, respectively.     

Artificial indoor streams as a method to investigate the impact of chemicals on lotic communities

The potential hazard of chemicals on aquatic communities are generally evaluated by standardised single-species bioassays. Safety assessment is based on results gained from organisms adapted to lentic systems and biological interactions in ecosystems are neglected. While lotic communities are often at first in contact with chemicals, it is astonishing that microcosms with lentic communities are mainly used as a bridge between laboratory bioassays and outdoor aquatic systems. Hence, we established five artificial indoor streams to simulate abiotic factors of small rivers. The closed-circuit system was filled with nutrients added to tap water. Washed pebbles were used as sediment. The dynamics of a simple biocoenoses consisting of aufwuchs, Lumbriculus variegatus Asellus aquaticus and Gammarus fossarum was investigated. The dynamic of aufwuchs and periphyton was determined as dry weight and chlorophyll-a, respectively and qualitatively by pigment pattern. The abundance of different developmental stages of L. variegatus was determined at the end of the experiment as well as the population dynamics of G. fossarum and A. aquaticus. Survival rates of gammarids and juveniles per female were investigated and data were used for modelling the population dynamics. The experiment was carried out to investigate the performance of the established artificial streams and the developed approaches to investigate effects of chemicals on a basic lotic community. The prime reason to establish this approach was to close a gap between complex artificial stream systems and laboratory single species tests to assess the impact of chemicals on the aquatic environment.     

?konomische ans?tze zur ?kosystembewertung Am Beispiel des Bodens

Zusammenfassung  Da es in einer Industriegesellschaft unm?glich ist, die Belastungen von ?kosystemen auf ein Ma? zu reduzieren, das jegliche Sch?digung ausschlie?t, besteht die Notwendigkeit der Bewertung. Eine der zur Verfügung stehenden Bewertungstechniken ist der ?konomische Ansatz. In der Artikelserie wird dieser Ansatz am Beispiel des Bodens vorgestellt. Im vorliegenden dritten Teil wird die Berücksichtigung des Faktors Zeit durch die sogenannte Diskontierung erl?utert. Auf den ersten Blick führt die Diskontierung dazu, da? Sch?den durch Umweltbelastungen, die m?glicherweise erst von zukünftigen Generationen getragen werden müssen, für die gegenw?rtige Generation (die diese Sch?den verursacht) in ihrer Bedeutung reduziert werden. Vor diesem Hintergrund werden verschiedene Begründungen für die Diskontierung diskutiert und es wird gezeigt, warum die Diskontierung auch bei einer intergenerativen Abw?gung von Kosten und Nutzen unverzichtbar ist. Die Pr?ambel zu diesem Beitrag ist ver?ffentlicht in UWSF 2/99, S. 119, 1999.