Trends of PCDD/F and PCB concentrations and depositions in ambient air in Northwestern Germany

Time series of polychlorinated dioxins and furans (PCDD/F) and polychlorinated biphenyls (PCB) in ambient air of a large conurbation in North-Western Germany are presented and analyzed. The trend of PCDD/F concentrations, starting from as early as 1988, shows a pronounced decrease by at least one order of magnitude, demonstrating that the emission reductions were effective. The PCDD/F depositions also have decreased by a factor of 5 since 1992. However, both trends have leveled out since 2005. Time series of PCB concentrations and depositions starting in 1994 show only slight decreases for the concentrations and almost no decrease for the depositions. From the decay rates following first order kinetics, half-lives in the order of 5-15 years for the PCDD/F and 15-31 years for the sum of the six indicator PCB could be calculated, which are much longer than the half-lives estimated from their reactivity towards the OH radical. Apparently, small fresh emissions (PCDD/F), considerable secondary emissions and evaporation from contaminated soils slow down their decay in the atmosphere of big conurbations. Analyzing the decay rates of individual PCB congeners shows that the lower chlorinated and more volatile ones are removed faster than the higher chlorinated congeners, probably via gas phase reactions with the OH radical. It can be concluded from the present study that the input of PCDD/F and PCB into the food chain via the air path will continue for another one or two decades in big conurbations.     

Fog as a Fresh-Water Resource: Overview and Perspectives

The collection of fog water is a simple and sustainable technology to obtain fresh water for afforestation, gardening, and as a drinking water source for human and animal consumption. In regions where fresh water is sparse and fog frequently occurs, it is feasible to set up a passive mesh system for fog water collection. The mesh is directly exposed to the atmosphere, and the foggy air is pushed through the mesh by the wind. Fog droplets are deposited on the mesh, combine to form larger droplets, and run down passing into a storage tank. Fog water collection rates vary dramatically from site to site but yearly averages from 3 to 10 l m⁻² of mesh per day are typical of operational projects. The scope of this article is to review fog collection projects worldwide, to analyze factors of success, and to evaluate the prospects of this technology.     

The Probability of a Horizontal Gene Transfer from Roundup Ready® Soybean to Root Symbiotic Bacteria: A Risk Assessment Study on the GSF Lysimeter Station

The gene transfer from glyphosate tolerant soybean to Bradyrhizobium japonicum was evaluated in a free-air lysimeter experiment under natural conditions and increasing selection pressure, to monitor for the probability of horizontal gene transfer (HGT). A large volume lysimeter study that offers conditions comparable to normal farming was conducted in 2004 and 2005 with Roundup Ready® (RR) soybean and Roundup® application according to agricultural practice. Analysis of nodules showed, as expected, the presence of the transgenic 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). However, in bacteroids that were isolated from nodules and then cultivated for several rounds in the presence of high levels of glyphosate, the EPSPS gene could no longer be detected. This indicates no stable HGT transfer of the whole EPSPS gene under field conditions.     

Elimination of Pentachlorobiphenyls by Nereis virens (Polychaeta) in the Laboratory and the Marine Environment

Fifty sandworms, Nereis virens, were maintained in a closed aquarium system with continuous charcoal filtration at 12°C and 27.6‰ S. They were dosed orally for 10 consecutive days with a mixture of three pentachlorobiphenyls: 35 ng 2,4,6,2',4'-pentachloro[U-¹⁴C]biphenyl, 106 ng 2,4,5,2',5'-pentachlorobiphenyl, and 106 ng 2,3,4,2',5'-pentachlorobiphenyl per g of Nereis virens per day. At the end of the dosing period the accumulated compounds were measured in 5 worms, the remaining 45 specimens were divided into three groups for determining the PCB elimination under different conditions for 14 to 26 weeks: in the laboratory with feeding, in the laboratory without feeding, and in a cage moored in the Weser estuary.

The accumulation percentages for these PCB compounds were 41, 26 and 4% respectively. Times for the initial 50% decrease t_e50 were 4.4, 2.8 and 1.9 weeks respectively, and appeared the same in all three experimental groups. However, in the laboratory experiments the metabolites of the ¹⁴C-labelled compound amounted to ∼60%, compared to the field experiment with ∼30%. This extended the t_e50 for ¹⁴C activity (metabolites included) to ∼9 weeks in the laboratory experiments.     

A dynamic two-dimensional system for measuring volatile organic compound volatilization and movement in soils

There is an important need to develop instrumentation that allows better understanding of atmospheric emission of toxic volatile compounds associated with soil management. For this purpose, chemical movement and distribution in the soil profile should be simultaneously monitored with its volatilization. A two-dimensional rectangular soil column was constructed and a dynamic sequential volatilization flux chamber was attached to the top of the column. The flux chamber was connected through a manifold valve to a gas chromatograph (GC) for real-time concentration measurement. Gas distribution in the soil profile was sampled with gas-tight syringes at selected times and analyzed with a GC. A pressure transducer was connected to a scanivalve to automatically measure the pressure distribution in the gas phase of the soil profile. The system application was demonstrated by packing the column with a sandy loam in a symmetrical bed-furrow system. A 5-h furrow irrigation was started 24 h after the injection of a soil fumigant, propargyl bromide (3-bromo-1-propyne; 3BP). The experience showed the importance of measuring lateral volatilization variability, pressure distribution in the gas phase, chemical distribution between the different phases (liquid, gas, and sorbed), and the effect of irrigation on the volatilization. Gas movement, volatilization, water infiltration, and distribution of degradation product (Br-) were symmetric around the bed within 10%. The system saves labor cost and time. This versatile system can be modified and used to compare management practices, estimate concentration-time indexes for pest control, study chemical movement, degradation, and emissions, and test mathematical models.     

An apparatus for measuring the gas permeability of films

The gas permeability of plastic films is important in packaging, containment, and agricultural fumigation. Recently, an approach for estimating the mass transfer coefficient of vapors across a film was presented by Papiernik et al. (2001). The mass transfer coefficient is an intrinsic property of a film-chemical combination, independent of the concentration gradient maintained across the film. Here we describe an apparatus useful for obtaining permeability data; the model of Papiernik et al. (2001) may be fitted to the data to determine mass transfer coefficients. The assembled equipment provides a sealed permeability cell, where a sample of the film to be tested is sandwiched between two static half-cells. Vapor is spiked to one side of the film and the concentrations in the spiked and receiving chamber are monitored until equilibrium. A sealed system is required for this approach; the permeability cells described here were gas-tight for >40 d. This approach produces reproducible measures of mass transfer coefficients that are not dependent on the size of the experimental apparatus. Model parameters were similar when fitted simultaneously as when determined independently from the same data set.     

Simulation der aeroben und anaeroben Abwasserreinigung mit einfachen Mitteln

Before waste-water-relevant organic materials are to be found in large quantities, their specific behavior in sewage treatment plants must be known. With the aid of the OECD simulation test #303 A, an estimation of their elimination in biological clarification stages can be made. In this work, an economical and continuous testing system is presented, which consists of a polyester flies bound to an activated biosludge with a high inoculum density, allowing one to measure no only the elimination of individual substances, but also the specific degree of mineralization. The toxicity of the activated biosludge and the nitrifying substances can also be examined. With the described testing procedure, it is possible to determine the rate of degradation within only a few hours. Finally, it can also be seen that it is possible to reliably and continuously determine the rate of anaerobic, biological degradability through the use of such a modified testing procedure.     

Strategien zur Sedimentbewertung – ein Überblick

Background Being an important determinant in aquatic ecosystems, sediments have gotten more and more into focus of scientific and public discussions. While water quality has been significantly improving during recent years, highly contaminated sediments in many European rivers will still have ongoing impact for several centuries from now. Hence, monitoring and assessment of sediment quality are crucial for national legislation as well as the implementation of the European Water Framework Directive (WFD). Aim On the occasion of the retirement of Prof. Dr. Dr. h.?c. Volker Storch, this article reviews the various concepts of sediment assessment and introduces case studies in sediment toxicology which have been carried out in Heidelberg and surrounding areas. Results and Discussion Initially, the article portrays benefits and drawbacks of chemical analytics and biotest systems. The individual approach has only limited informative value, but combining both perspectives allows for a comprehensive characterization of the state of sediments. As examples of toxicity evaluation based on this strategy, weight-of-evidence studies for tiered investigations and integrated sediment assessment are presented. In addition, a combination of chemical fractionation, bioanalytic investigations and chemical analysis – known as ‘effect-directed analysis’ (EDA) – is discussed. This integrated concept eventually aims at the identification of hazardous substance classes or even of single compounds. Finally, the article raises the issue of sediment mobility as an important parameter for risk analyses of highly contaminated legacy sediments within further WFD implementation. Outlook Using various case studies, the article outlines the potentials of integrated approaches for cause-effect analysis of complex environmental samples within aquatic ecosystems as well as for action programs of management plans dealing with chemically polluted rivers. Effect-directed analysis in particular, but also the combined application of acute and mechanism-specific bioassays together with in-situ investigations, complemented by investigations on sediment mobility, appear promising with regard to comprehensive sediment assessment weight-of-evidence studies.     

Elevation change and the vulnerability of Rhode Island (USA) salt marshes to sea-level rise

Salt marshes persist within the intertidal zone when marsh elevation gains are commensurate with rates of sea-level rise (SLR). Monitoring changes in marsh elevation in concert with tidal water levels is therefore an effective way to determine if salt marshes are keeping pace with SLR over time. Surface elevation tables (SETs) are a common method for collecting precise data on marsh elevation change. Southern New England is a hot spot for SLR, but few SET elevation change datasets are available for the region. Our study synthesizes elevation change data collected from 1999 to 2015 from a network of SET stations throughout Rhode Island (RI). These data are compared to accretion and water level data from the same time period to estimate shallow subsidence and determine whether marshes are tracking SLR. Salt marsh elevation increased at a mean overall rate of 1.40 mm year^?1 and ranged from ?0.33 to 3.36 mm year^?1 at individual stations. Shallow subsidence dampened elevation gain in mid-Narragansett Bay marshes, but in other areas of coastal RI, subsurface processes may augment surface accretion. In all cases, marsh elevation gain was exceeded by the 5.26 mm year^?1 rate of increase in sea levels during the study period. Our study provides the first SET elevation change data from RI and shows that most RI marshes are not keeping pace with short- or long-term rates of SLR. It also lends support to previous research that implicates SLR as a primary driver of recent changes to southern New England salt marshes.