Degassing of H/He, CFCs and SF6 by denitrification: Measurements and two-phase transport simulations

The production of N₂ gas by denitrification may lead to the appearance of a gas phase below the water table prohibiting the conservative transport of tracer gases required for groundwater dating. We used a two-phase flow and transport model (STOMP) to study the reliability of ³H/³He, CFCs and SF₆ as groundwater age tracers under agricultural land where denitrification causes degassing. We were able to reproduce the amount of degassing (R² = 69%), as well as the ³H (R² = 79%) and ³He (R² = 76%) concentrations observed in a ³H/³He data set using simple 2D models. We found that the TDG correction of the ³H/³He age overestimated the control ³He/³He age by 2.1 years, due to the accumulation of ³He in the gas phase. The total uncertainty of degassed ³H/³He ages of 6 years (± 2 σ) is due to the correction of degassed ³He using the TDG method, but also due to the travel time in the unsaturated zone and the diffusion of bomb peak ³He. CFCs appear to be subject to significant degradation in anoxic groundwater and SF₆ is highly susceptible to degassing. We conclude that ³H/³He is the most reliable method to date degassed groundwater and that two-phase flow models such as STOMP are useful tools to assist in the interpretation of degassed groundwater age tracer data.     

Climate change impacts on the leaching of a heavy metal contamination in a small lowland catchment

The Keersop catchment (43km(2)) in the south of The Netherlands has been contaminated by the emissions of four zinc ore smelters. The objective of this study was to assess the effects of future projected climate change on the hydrology and the leaching of heavy metals (i.e. Cd and Zn) in the catchment. The numerical, quasi-2D, unsaturated zone Soil Water Atmosphere Plant model was used with 100-year simulated daily time series of precipitation and potential evapotranspiration. The time series are representative of stationary climates for the periods 1961-1990 ("baseline") and 2071-2100 ("future"). The time series of future climate were obtained by downscaling the results of eight regional climate model (RCM) experiments, driven by the SRES A2 emissions scenario, using change factors for a series of climate statistics and applying them to stochastic weather generator models. The time series are characterized by increased precipitation in winter, less precipitation in summer, and higher air temperatures (between 2°C and 5°C) throughout the year. Future climate scenarios project higher evapotranspiration rates, more irrigation, less drainage, lower discharge rates and lower groundwater levels, due to increased evapotranspiration and a slowing down of the groundwater system. As a result, lower concentrations of Cd and Zn in surface water are projected. The reduced leaching of heavy metals, due to drying of the catchment, showed a positive impact on a limited aspect of surface water quality.     

Generic foresight model in changing hygiene habits with the pandemic: use of wet wipes in next generations

Journal of Material Cycles and Waste Management - The vast use of wet wipes has now become a habitude, particularly following the altered perception of cleanliness during the pandemic and the...     

Determination of potential allergenic fungal flora and its clinical reflection in suburban elementary schools in Izmir

In this research, in order to determine mean fungus counts, indoor and outdoor air samples were taken in five elementary school buildings located in the city center of Seferihisar, Izmir (45 km from Izmir) within a 1-year period between March and April 2004, and between January and February 2005 representing similar climatic characteristics. Five samples, three from three classes where 5–8, 10–12, and 12–15 age group students attended, one from the corridors, and one from outside the buildings in all the schools, were taken for each period. Within the period of the study, in indoor and outdoor air samples, 7,122 microfungus colonies were counted. Sixty-four species were identified that belong to 17 genera as a result of the identification of isolates obtained. Skin prick tests were applied to 55 out of a total of 117 teachers by the clinicians. According to these test results, 24 teachers were sensitive to at least one agent. Results revealed that, in terms of mold counts, the difference between the schools and the difference between the times (periods) were statistically significant (p?< 0.05).     

Characterization and COD fractionation of domestic wastewaters

Results of a comprehensive study are reported for wastewater characterization in relation to modelling and design of biological nutrient removal systems for the Metropolitan Area of Istanbul. Domestic sewage quality was experimentally assessed in terms of major polluting parameters. Size distribution and calculation of significant ratios such as BOD5:COD and COD:N were used to evaluate the merit of candidate physical, chemical and biological treatment alternatives. COD fractionation was effected to assess biological treatability and to yield the necessary process components to the recent modelling approaches.     

Ethical Approach to Fluoridation in Drinking Water Systems of UK and Turkey

The practice of adding substances to make water safe to drink and its consequential effects on human health have been a contentious matter for a long time. In this study, the addition of fluoride in drinking water was evaluated after examining two different countries: Britain and Turkey. This study has used an independent and ethical approach taking into account the cautious but assertive dentists’ comments on the addition of fluoride for years. This research focuses on a comparative analysis of Britain, an advanced economy, and Turkey, a developing country, supported with tangential reference to worldwide practice in general. Drawing on ongoing studies, the research analyses empirical evidence and arguments to conduct an assessment of Turkey’s practices. The ethical argument about fluoridation focuses on the question of adequate evidence for its health benefits and the autonomy of the consumer. As the consumer is not fully consulted about this practice, it could be argued that the will of the consumer can be put to the test in the democratic process. Hence, the key to any policy has to be about both clarity of the national government intention and continued engagement with consumer groups at regional level.     

Determination of Cadmium and Copper in Fish Samples from Sir And Menzelet Dam Lake Kahramanmaraş, Turkey

The cadmium and copper levels were determined in the total of 126 fish samples which belongs to five fish species collected from Sır and Menzelet Dam Lakes in Kahramanmaraş Province by Atomic Absorption Spectrophotometer. The concentrations of heavy metals were expressed as ppm wet weight of tissue. The mean levels of cadmium and copper in muscle, liver and gill tissues of Cyprinus carpiofrom the Menzelet Dam were found as 0.27, 0.91, 1.49 and 0.94, 1.2, 1.05, respectively. The mean levels of Cd in the muscle tissues of Leuciscus cephalusfrom the Menzelet Dam were found 0.32 ppm, Cd wasn't found in tissues of liver and gill. The mean levels of Cu in the muscle, liver and gill tissues were found as 3.17 ppm, 1.19 ppm, 0.96 ppm, respectively. The mean levels of the Cd and Cu in muscle and gill tissues of Acanthobrama marmid from the Sır Dam were found as 1.28, 2.64 and 0.72, 0.08, respectively. The levels of the Cd and Cu in muscle tissues of Cyprinus carpiofrom the Sır Dam were found 0.87 and 0.02 ppm, respectively. The mean levels of the Cd and Cu in the muscle and gill tissues of Chondrostoma regium from the Sır Dam were found to be 0.80, 2.62 and 0.67, 1.34 ppm, respectively. The mean levels of the Cd in the muscle tissues of the Silurus glanis was found as 0.60 ppm. In the muscle of the Silurus glanis from the Sır Dam, Cu was not found. The Sır Dam is more polluted than the Menzelet Dam from the point of Cd but less polluted than the Menzelet Dam From the point of Cu. A relationship was determined between species and their habitating region in terms of the levels reflected metal residues. In this study it was emphasized that the amounts of Cd and Cu in the samples were low, however, seas, lakes, rivers, soil, air and consumed foods etc. has to be controlled routinely.