The hydrolysis of Zectran in buffered and natural waters.

The analyses and rates of hydrolysis of Zectran, 4-dimethylamino-3,5-xylyl methylcarbamate are reported in aqueous media. These rates were measured in phosphate buffered, distilled water and in natural waters where tempteratures of 10 degrees, 20 degrees, and 28 degrees C. and pH values of 5.94, 7.00, and 8.42 were used. Intial concentrations of Zectran exceeded 60 mg/l (0.27 mMol 1(-1), whereas in the natural waters initial concentrations were 30 mg/l (0.135 mMol 1(-1). This study shows that the persistance of Zechtran in natural waters is, in large part, dependent upon the pH value and the temperature.     

Multivariate analysis of Almendares River waters.

The Almendares River is the most important surface water body of the Cuban capital, Havana. In the present work, the environmental quality of waters was studied as a function of the following 14 variables: content of calcium, cadmium, iron, potassium, magnesium, manganese, sodium, nickel, zinc, chlorine, bicarbonate, and sulfate; pH; and electric conductivity parameters, which were reduced to three new variables by means of principal component analysis (PCA). The content of metal increased in waters sampled at stations located near garbage dumps and decreased inside the Ejercito Rebelde dam. The variation of the river water environmental quality with rainy and dry seasons and the differentiation of samples in three groups along the river course were obtained by PCA and corroborated by discriminant analysis. Applied statistical techniques showed their ability for environmental interpretation of limited experimental data.     

The photocatalytic disinfection of urban waste waters

In this paper we present the results of the photocatalytic disinfection of urban waste water. Two microbial groups, total coliforms and Streptococcus faecalis, have been used as indexes to test disinfection efficiencies. Different experimental parameters have been checked, such as the effect of TiO2, solar or UV-lamp light and pH. Disinfection of water samples has been achieved employing both UV-lamp and solar light in agreement with data shown by other authors. The higher disinfection rates obtained employing an UV-lamp may be explained by the stronger incident light intensity. Nevertheless no consistent differences have been found between TiO2-photocatalysis and direct solar or UV-lamp light irradiation at natural sample pH (7.8). At pH 5 the presence of TiO2 increases the relative inactivation rate compared with the absence of the catalyst. After the photocatalytic bacterial inactivation, the later bacterial reappearance was checked for total coliforms at natural pH and pH 5, with and without TiO2. Two h after the photocatalytic treatment, CFU increment was almost nill. But 24 and 48 h later an important bacterial CFU increment was observed. This CFU increment is slower after irradiation with TiO2 at pH 5 in non-air-purged samples.     

The negative impacts of human activities in the eastern African region: an international waters perspective

The complex interactions between human activities and the environment at the interface of land and water is analyzed with a focus on the Somali Current (East Africa), and Indian Ocean Island States, subregions of the Global International Waters Assessment (GIWA). These 2 subregions contain some of the world's richest ecosystems, including the high biodiversity forests of Madagascar and the diverse coastal habitats of the eastern African coast. These ecosystems support local communities and national and regional economies. Current and future degradation of these systems, from water basins to continental shelves, affects the livelihoods and sustainability of the countries in the region, and long-term efforts to reduce poverty. The assessments determined that pollution and climate change are the primary environmental and social concerns in the Islands of the Indian Ocean, while freshwater shortage and unsustainable exploitation of fisheries and other living resources are the primary environmental and social concerns in East Africa. The GIWA approach, through assessing root causes of environmental concerns, enables the development of policy approaches for mitigating environmental degradation. This paper explores policy frameworks for mitigating the impacts, and reducing the drivers, of 3 environmental concerns--freshwater shortage; solid waste pollution; and climate change--addressing social and institutional causes and effects, and linking the subregions to broad international frameworks. The common theme in all 3 case studies is the need to develop integrated ecosystem and international waters policies, and mechanisms to manage conflicting interests and to limit threats to natural processes.     

The formation of singlet oxygen in surface waters

The photochemical formation of singlet oxygen in some Dutch surface waters has been investigated using the method developed by Zepp (1). However, when monitoring the consumption of oxygen beside that of 2,5-dimethylfuran (DMF), the compound added to chemically snare singlet oxygen, it was found that appreciable, but varying parts of DMF were used up by secondary reactions leading largely to the same products, viz. cis- and trans-diacetylethylene. When taking the oxygen consumption as a measure for the singlet oxygen production on the basis of the stoichiometry of the primary reaction, a fair correlation between the singlet oxygen production and the total organic carbon (TOC) content was found for this selection of Dutch surface water samples. The steady-state concentrations of singlet oxygen determined in this way were about one order of magnitude lower than those found by Zepp (1) and by Zafiriou (2).     

Modelling episodic acidification of surface waters: the state of science

Field studies of chemical changes in surface waters associated with rainfall and snowmelt events have provided evidence of episodic acidification of lakes and streams in Europe and North America. Modelling these chemical changes is particularly challenging because of the variability associated with hydrological transport and chemical transformation processes in catchments. This paper provides a review of mathematical models that have been applied to the problem of episodic acidification. Several empirical approaches, including regression models, mixing models and time series models, support a strong hydrological interpretation of episodic acidification. Regional application of several models has suggested that acidic episodes (in which the acid neutralizing capacity becomes negative) are relatively common in surface waters in several regions of the US that receive acid deposition. Results from physically based models have suggested a lack of understanding of hydrological flowpaths, hydraulic residence times and biogeochemical reactions, particularly those involving aluminum. The ability to better predict episodic chemical responses of surface waters is thus dependent upon elucidation of these and other physical and chemical processes.     

The mechanism of delayed neuropathy caused by some organophosphorus esters: Using the understanding to improve safety

Abstract

The mechanism of delayed neurotoxicity of some OP (organophosphorus) esters such as DFP (di‐isopropyl phosphorofluoridate) and TOCP (tri‐o‐cresyl phosphate) involves an initial two‐step process affecting an esterase called NTE (neurotoxic esterase). This understanding permits the assessment of delayed neuropathic potential in terms of a quantitative measurement of inhibition of NTE in tissue taken from dosed hens. Structure/activity relationships have been rationalized and the neurotoxic potential of those OP esters which are direct inhibitors of esterases may now be assessed in vitro. The response of human NTE can usefully be compared with that of hen NTE. Nil delayed neurotoxic potential is associated with carbamate or phosphinate anticholinesterases which may be designed as insecticides.     

Removal of pesticides from surface waters by combined physicochemical processes. Part I: Dodine

The simultaneous action of powdered activated carbon and several coagulant agents on the removal of the fungicide dodine from spiked distilled water, was studied. As coagulants, ferric chloride (FeCl₃) and basic polyaluminium chlorosulfate ([Al(OH)_xCl_y(SO₄)_z]_n) were examined, using polyacrylamide, in certain cases, as coagulant aid (polyelectrolyte). The efficiency of dodine removal was investigated with respect to the added amount of powdered activated carbon (PAC), the pH value, as well as the type and dose of coagulant and polyelectrolyte. The experiments were performed applying the standard jar-test procedure. The initial concentration of dodine was 250 μg/L. At this concentration and pH range 5–8 it was found that a dose of 100 mg/L PAC was necessary to achieve more than 98% removal of dodine, whereas lower removal (91–93%) was obtained applying half the dose of PAC under the same conditions. However, when 10–100 mg/L FeCl₃ were simultaneously added with PAC, the removal efficiency increased to >98%, even with the half PAC dose.     

The effect of emission of industrial dusts on bacteria in the waters of the Niepolomice Forest

The presented results were obtained in a further microbiological investigation carried out in the Niepołomice Forest against the background of a general ecological study. Bacteria occurring in the aquatic environment were resistant to the toxic action of industrial dusts which, among other components, contained heavy metals. The in vivo adsorption of metals by bacteria was also found.     

Coagulation of colloidal material in surface waters: the role of natural organic matter

Organic matter has a great influence over the fate of inorganic colloids in surface waters. The chemical nature and structure of natural organic matter (NOM) will be an important factor in determining whether colloids will be stabilised or destabilised by NOM. Under environmentally relevant conditions, the ubiquitous fulvic acids are likely to be responsible for coating and imparting a negative charge to colloids. If the adsorbed polyelectrolyte coating produces an increase in absolute surface potential, it will act to stabilise colloids in the water column. On the other hand, colloidal organic carbon, especially chain-like structures, has been shown to be involved in the aggregation of inorganic colloids through the formation of bridges. It is highly probable that both adsorption and bridging flocculation are occurring simultaneously in the natural aquatic environment. The importance of each process depends directly on the nature and concentration of organic matter in the system and indirectly on the productivity of the lake, its hydrological pathways, temporal variations, temperature, etc. The present paper reports such results and emphasises the need to discriminate the different kinds of NOM.     

Tetracycline photolysis in natural waters: loss of antibacterial activity

Previous work has shown that tetracycline undergoes direct photolysis in the presence of sunlight, with the decomposition rate highly dependent on conditions such as water hardness and pH. The purpose of this study was to examine the potential long-term significance of photoproducts formed when tetracycline undergoes photodegradation under a range of environmentally relevant conditions. Tetracycline was photolyzed in nine different natural and artificial water samples using simulated sunlight. The pH values of the samples ranged from 5 to 9. Total hardness values (combined Ca²⁺ and Mg²⁺ concentrations) varied from 30 to 450 ppm. Assays based on growth inhibition of two bacterial strains, Escherichia coli DH5α and Vibrio fischeri, were used to determine the antibacterial activity of tetracycline’s photoproducts in these water samples. In all tested conditions, it was determined that the photoproducts retain no significant antibacterial activity; all observed growth inhibition was attributable to residual tetracycline. This suggests that tetracycline photoproducts formed under a wide range of pH and water hardness conditions will not contribute to the selection of antibiotic-resistant bacteria in environmental systems.     

The supersaturation of carbonyl sulfide (OCS) in rain waters

Rain samples were collected during 9 months in 1985 at Gif-sur-Yvette, France, and their carbonyl sulfide content was measured. The majority of the 45 samples revealed the presence of significant OCS supersaturation. The average supersaturation index is 8.0 ± 5.8 and the excess of dissolved OCS is correlated positively with the acid content of the rain water. The cause of the OCS enhancement is still unknown. Several hypotheses are discussed to explain the origin of the supersaturation.     

Occurrence of glucocorticogenic activity in various surface waters in The Netherlands

Considering the important role that surface waters serve for drinking water production, it is important to know if these resources are under the impact of contaminants. Apart from environmental pollutants such as pesticides, compounds such as (xeno)estrogens have received al lot of research attention and several large monitoring campaigns have been carried out to assess estrogenic contamination in the aquatic environment. The introduction of novel in vitro bioassays enables researchers to study if – and to what extent – water bodies are under the impact of less-studied (synthetic) hormone active compounds. The aim of the present study was to carry out an assessment on the presence and extent of glucocorticogenic activity in Dutch surface waters that serve as sources for drinking water production. The results show glucocorticogenic activity in the range of <LOD – 2.4 ng dexamethasone equivalents L⁻¹ (dex EQs) in four out of eight surface waters. An exploratory time-series study to obtain a more complete picture of the yearly average of fluctuating glucocorticogenic activities at two sample locations demonstrated glucocorticogenic activities ranging between <LOD – 2.7 ng dex EQs L⁻¹. Although immediate human health effects are unlikely, the environmental presence of glucocorticogenic compounds in the ng L⁻¹ range compels further environmental research and assessment.     

The occurrence of antihistamines in sewage waters and in recipient rivers

Background, aim and scope  Each year, large quantities of pharmaceuticals are consumed worldwide for the treatment and prevention of human and animal diseases. Although the drugs and the metabolites observed in the wastewaters and in the environment are present at concentrations several orders of magnitude lower than the concentrations required to exert their effects in humans or animals, their long-term impact on the environment is commonly not known. In this study, the occurrence of six antihistamines, which are used for the relief of allergic reactions such as hay fever, was determined in sewage treatment plants wastewaters and in recipient river waters. Materials and methods  The occurrence of the antihistamines cetirizine, acrivastine, fexofenadine, loratadine, desloratadine and ebastine in sewage treatment plants wastewaters and in recipient river waters was studied. The analytical procedure consisted of solid-phase extraction of the water samples followed by liquid chromatography separation and detection by a triple-quadrupole mass spectrometer in the multiple reaction mode. Results  Cetirizine, acrivastine and fexofenadine were detected in both influent and effluent wastewater samples at concentration levels ranging from about 80 to 220 ng/L, while loratadine, desloratadine and ebastine could not be detected in any samples. During sewage treatment, the concentration of the antihistamines dropped by an average of 16–36%. Furthermore, elevated concentrations of antihistamines were observed in samples collected during the season of most intensive plant pollen production, i.e. in May. In the river water samples, the relative pattern of occurrence of cetirizine, acrivastine and fexofenadine was similar to that in the wastewater samples; although the concentration of the compounds was substantially lower (4–11 ng/L). The highest concentrations of the studied drugs were observed near the discharging point of the sewage treatment plant. Discussion  The highest concentrations of antihistamines in STP wastewaters correlate with the outbreak of allergic reaction caused by high amounts of plant pollens in the air. The analysis results of the river water samples show that the antihistamines are carried far away from the effluent discharge points. They may account for a part of the mix of pharmaceuticals and of pharmaceutical metabolites that occur downstream of STPs. Conclusions  Antihistamines are poorly degraded/eliminated under the biological treatment processes applied in the wastewater treatment plants and, consequently, they are continuously being discharged along with other drugs to the aquatic environment. Recommendations and perspectives  As a huge quantity and variety of drugs and their metabolites are continuously discharged to rivers and the sea, the compounds should be considered as contaminants that may possess risks to the aquatic ecosystem. Further studies are urgently needed on the environmental fate of the antihistamines and other pharmaceuticals in the aquatic environment. These studies should be concerned with the stability of the compounds, their transformation reactions and the identity of the transformation products, the distribution of drugs and their uptake and effects in organisms. On the basis of these studies, the possible environmental hazards of pharmaceuticals may be assessed.     

The effect of polluted and leached snow melt waters on the soil bacterial community-quantitative response

The effect of polluted snow melt waters on the number of soil bacteria was determined using soil cores extracted from an upland catchment in the Cairngorm Mountains, Scotland. Total numbers of viable heterotrophic bacteria and bacterial denitrifiers were determined using plate and MPN counts. Separate soil cores were treated with simulated melt waters representative of either the composition of the first melt fraction from polluted or leached snowpacks. The number of bacteria in the Ah soil horizon (Hodgson, 1974) treated with polluted snow melt (PSM) water decreased significantly by 28-fold, but increased by 11-fold in the BC horizon. Denitrifier numbers decreased by 8-fold in the Ah horizon, but increased by over 2-fold lower down the profile. Overall the bacterial community exposed to simulated leached snow melt (LSM) waters showed little change in the Ah horizon. In the BC horizon (Hodgson, 1974), total viable bacterial numbers decreased by 20-fold, but denitrifiers numbers were unaffected.