Listen
3 Ergebnisse
Filter
Einstellungen
Suchergebnisse
Veröffentlichung Current approaches to cyanotoxin risk assessment and risk management around the globe(2014)Toxic cyanobacteria became more widely recognized as a potential health hazard in the 1990s, and in 1998 the World Health Organization (WHO) first published a provisional Guideline Value of 1 ìg L-1for microcystin-LR in drinking-water. In this publication we compare risk assessment and risk management of toxic cyanobacteria in 17 countries across all five continents. We focus on the three main (oral) exposure vehicles to cyanotoxins: drinking-water, water related recreational and freshwater seafood. Most countries have implemented the provisional WHO Guideline Value, some as legally binding standard, to ensure the distribution of safe drinking-water with respect to microcystins. Regulation, however, also needs to address the possible presence of a wide range of other cyanotoxins and bioactive compounds, for which no guideline values can be derived due to insufficient toxicological data. The presence of microcystins (commonly expressed as microcystin-LR equivalents) may be used as proxy for overall guidance on risk management, but this simplification may miss certain risks, for instance from dissolved fractions of cylindrospermopsin and cyanobacterial neurotoxins. An alternative approach, often taken for risk assessment and management in recreational waters, is to regulate cyanobacterial presence - as cell numbers or biomass - rather than individual toxins. Here, many countries have implemented a two or three tier alert level system with incremental severity. These systems define the levels where responses are switched from Surveillance to Alert and finally to Action Mode and they specify the short-term actions that follow. Surface bloom formation is commonly judged to be a significant risk because of the elevated concentration of microcystins in a scum. Countries have based their derivations of legally binding standards, guideline values, maximally allowed concentrations (or limits named otherwise) on very similar scientific methodology, but underlying assumptions such as bloom duration, average body size and the amount of water consumed while swimming vary according to local circumstances. Furthermore, for toxins with incomplete toxicological data elements of expert judgment become more relevant and this also leads to a larger degree of variation between countries thresholds triggering certain actions. Cyanobacterial blooms and their cyanotoxin content are a highly variable phenomenon, largely depending on local conditions, and likely concentrations can be assessed and managed best if the specific conditions of the locality are known and their impact on bloom occurrence are understood. Risk Management Frameworks, such as for example the Water Safety Plan concept of the WHO and the ´bathing water profile of the European Union are suggested to be effective approaches for preventing human exposure by managing toxic cyanobacteria from catchment to consumer for drinking water and at recreational sites.
© www.sciencedirect.comVeröffentlichung Stabilization of chromium (VI) in the presence of iron (II): method development and validation(2020) El-Athman, Fatima; Polenz, Chantal; Mahringer, DanielThe presence of Cr (VI) in drinking water is mainly caused by leaching of chromium-containing aquifer material into groundwater. In contrast to Cr (III), it has been classified as highly toxic. For this reason, the WHO recommends the implementation of separate guideline values, instead of the so far used limit value of total chromium. The separate evaluation of Cr (VI) in raw water and during removal processes requires the Cr (VI) concentration to remain stable after sampling. In the presence of Fe (II), a stabilization of the samples is necessary to inhibit further reduction of Cr (VI) by Fe (II). In this study, two methods of Cr (VI) stabilization in Fe-(II)-containing water samples are investigated: Fe (II) oxidation by oxygen at high pH values in the presence of buffers and Fe (II) complexation by chelating agents. When adding hydrogen carbonate buffer, Cr (VI) recovery reached 100% at pH values of 10 to 12 in the presence of up to 3 mg L-1 Fe (II). Using hydrogen phosphate buffer, Cr (VI) recovery reached 100% only at pH 12 but for a Fe (II) concentration up to 6 mg L-1. Ammonium buffer was found to be less suitable for Cr (VI) stabilization. The addition of EDTA and citrate resulted in low recovery of Cr (VI), whereas citrate was found to accelerate the Cr (VI) reduction. Quelle: https://www.mdpi.comVeröffentlichung Recovery of Fluorinated Refrigerants from Decommissioned RAC Equipment in Germany - Implications for National Emission Reporting under the UNFCCC(2024) Behringer, David; Gschrey, Barbara; Martens, KerstinGermany is obliged to report emissions of fluorinated greenhouse gases annually under the UNFCCC. This includes emissions of fluorinated refrigerants when decommissioning RAC equipment. To obtain this information, data on the recovery, recycling, and disposal of fluorinated greenhouse gases is necessary, but such data are scarce. The VDKF-LEC database contains information on the recovery of fluorinated refrigerants from decommissioned RAC equipment in Germany and an extracted dataset was used to obtain real-world information for the years 2017 to 2021. Recovery rates for different fluorinated refrigerants from decommissioned commercial and industrial refrigeration as well as stationary air-conditioning equipment were derived. Furthermore, average lifetimes of equipment for the different sectors were calculated. In the analysis, a dependency of charged refrigerant and age of the unit at decommissioning could be observed. Results from the analysis of the VDKF-LEC dataset were compared with reported data under the UNFCCC for Germany and other available data sources. © 2023 by the authors