Importance of natural sedimentation in the fate of microcystins

Sedimentation processes of microcystins (MCs), cyanobacterial toxins, were studied in three reservoirs located in Central Spain in which the cyanobacterial community was dominated by the genus Microcystis. MCs were detected in the sediment traps deployed in all reservoirs. In Santillana reservoir, MCs were identified in sediment traps even though they could not be found in the pelagial samples. In the other reservoirs studied, sedimentation rates for MC-containing particles during the bloom period ranged from 0.43 to 2.53 mg m⁻² d⁻¹. Interestingly, this very high sedimentation of toxic biomass is not exclusively related to decaying blooms or autumnal sedimentation due to a drop in water temperature. Instead, it seems that MC-containing colonies may be settling constantly during the bloom period and we were able to estimate that during such a Microcystis dominated bloom, around 4.5% of pelagial MCs may be involved in sedimentation. Further, these settling colonies seem to maintain good cell integrity and MCs seem not to be excreted massively. A certain loss of toxin content along the vertical settling may be attributed to minor losses due to cell lysis or to variations in MC cell quota explained by reduced production or internal consumption. Our results for the first time establish specific settling rates for MC-containing particles in freshwaters and definitely identify sedimentation as a major destination for these toxins. These data may contribute to improve managing strategies concerning risks associated with MCs.     

Use of a column leaching test to study the mobility of chlorinated HOCs from a contaminated soil and the distribution of compounds between soluble and colloid phases

An equilibrium and recirculation column test for hydrophobic organic chemicals (ER-H test) was used to study the leaching behaviour of chlorophenols (CPs), polychlorinated diphenyl ethers (PCDEs), polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) from contaminated soil. A 50% increase in the pore water velocity was shown to have little or no effect on the mobility of CPs, PCDEs, PCDFs and PCDDs. The standard deviations of truly dissolved compounds, CPs, were between 19% and 65% between the tests. However, the repeatability of the ER-H test decreased with increases in the hydrophobicity of the studied compounds; the standard deviations for PCDEs, PCDFs and PCDDs ranged from 53% to 110%, 57% to 77% and 110% to 130%, respectively. The influence of colloids on the release of these compounds was also examined. Up to 30% of the CPs in the soil were leached, of which 1-3% were associated with colloids. The PCDEs, PCDFs and PCDDs were found to be preferably associated with the particulate fraction of the leachate, and less than 0.2% of these compounds were mobilised.     

Design and off-design analyses of a pre-combustion CO2 capture process in a natural gas combined cycle power plant

In this study, a cycle designed for capturing the greenhouse gas CO₂ in a natural gas combined cycle power plant has been analyzed. The process is a pre-combustion CO₂ capture cycle utilizing reforming of natural gas and removal of the carbon in the fuel prior to combustion in the gas turbine. The power cycle consists of a H₂-fired gas turbine and a triple pressure steam cycle. Nitrogen is used as fuel diluent and steam is injected into the flame for additional NO_x control. The heat recovery steam generator includes pre-heating for the various process streams. The pre-combustion cycle consists of an air-blown auto-thermal reformer, water–gas shift reactors, an amine absorption system to separate out the CO₂, as well as a CO₂ compression block. Included in the thermodynamic analysis are design calculations, as well as steady-state off-design calculations. Even though the aim is to operate a plant, as the one in this study, at full load there is also a need to be able to operate at part load, meaning off-design analysis is important. A reference case which excludes the pre-combustion cycle and only consists of the power cycle without CO₂ capture was analyzed at both design and off-design conditions for comparison. A high degree of process integration is present in the cycle studied. This can be advantageous from an efficiency stand-point but the complexity of the plant increases. The part load calculations is one way of investigating how flexible the plant is to off-design conditions. In the analysis performed, part load behavior is rather good with efficiency reductions from base load operation comparable to the reference combined cycle plant.     

Bepflanzung einer Tankstelle mit Weiden

In Axelved, Denmark, an abandoned gas filling station serves as a test field for phytoremediation. Laboratory studies accompany the project. The toxicity of fresh and weathered gasoline and diesel to willow and poplar trees was studied by use of a tree transpiration toxicity test. The correlation between diesel content in soil and decrease in willow tree transpiration (Salix viminalis x schwerinii) was highly significant (r ²=0.81, n=19). the EC₅₀ (50% inhibition of transpiration) for the sum of hydrocarbons (HC) was determined to be 3910 mg/kg (95% confidence interval from 2900 to 5270 mg/kg). The EC₁₀ was 810 mg/kg (95% confidence interval 396 to 1660 mg/kg). The results were verified with artificially mixed diesel and gasolinecontaminated soils and two willow and one poplar species (S. viminalis, S. alba andPopulus nigra). The degradation of radiolabeledm-xylene was studied with and without willows. The compound was readily degraded. Willow trees accelerated the elimination, but mainly due to the volatilization ofm-xylene. Model studies provided the result that biodegradation in soil is the fastest elimination process at the site, but it is limited by the availability of electron acceptors. The pollutants are almost persistent in the groundwater, but in aerated soil, 10000 mg/kg hydrocarbons at 1 m depth are degraded within 13 years. The main effect of willows on the pollutants’ persistence is that willows transpire water, lower the groundwater level and aerate the soil, hereby speeding up biodegradation.     

Toxaphene chemistry: separation and characterisation of selected enantiomers of the Polychloropinene mixtures

The primary goal for the study presented here was the preparation and characterisation of enantiomeric pure chlorobornane standards (Toxaphene). In this context, we partially modeled the procedure for Polychloropinene production in the former USSR. The initial reaction was ionic addition of hydrogen chloride to (1S)-alpha-pinene resulting predominantly in (1S)-2-endo-chlorobornane. Further photochlorination gave mixtures of chlorinated terpenes with different average content of Cl per molecule. The resulting mixtures were separated on a silica-gel column and a number of known hepta to decachlorobornanes were identified in fractions with the help of NMR and GC (using electron capture and mass spectrometric detection)--but in very unusual ratios as compared to the technical Toxaphene mixture formerly produced by Hercules (USA). Also several previously unknown congeners were isolated or detected. Three of the isolated congeners were obtained in crystalline state and X-ray crystallography showed their enantiomeric purity.     

Mobility of chloroaromatic compounds in soil: case studies of Swedish chlorophenol-contaminated sawmill sites

This paper summarizes recent studies on the environmental fate of chloroaromatic compounds in chlorophenol (CP)-contaminated soil and groundwater at Swedish sawmill sites. Relative proportions of CPs, polychlorinated phenoxy phenols (PCPPs), polychlorinated diphenyl ethers (PCDEs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) were determined in preservatives, particulate organic matter (POM), dissolved organic matter (DOM), groundwater, and particles filtered from groundwater. All compound classes were found in the different compartments. The fraction of PCPPs, PCDEs, PCDDs, and PCDFs had increased in the soil samples relative to the proportions in the preservatives. This increase showed correlation with the hydrophobicity, that is, PCDDs had the largest increase. Similar correlation was found between hydrophobicity and the importance of partitioning to POM over DOM. The more water soluble compound group, CP, was found equally distributed between POM and DOM. For PCPPs, PCDEs, PCDDs, and PCDFs, the relative partitioning to POM increased with increased hydrophobicity. Despite the relative partitioning towards POM, compared with DOM, cotransport with DOM and suspended colloidal fractions was found to substantially increase the transport of these compounds in the groundwater samples.     

Sources, fate, and toxic hazards of oxygenated polycyclic aromatic hydrocarbons (PAHs) at PAH-contaminated sites

In this paper we show that oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) are important cocontaminants that should be taken into account during risk assessment and remediation of sites with high levels of PAHs. The presented data, which have been collected both from our own research and the published literature, demonstrate that oxy-PAHs are abundant but neglected contaminants at these sites. The oxy-PAHs show relatively high persistency and because they are formed through transformation of PAHs, their concentrations in the environment may even increase as the sites are remediated by methods that promote PAH degradation. Furthermore, we show that oxy-PAHs are toxic to both humans and the environment, although the toxicity seems to be manifested through other effects than those known to be important for polycyclic aromatic compounds in general, that is, mutagenicity and carcinogenicity. Finally, we present data that support the hypothesis that oxy-PAHs are more mobile in the environment than PAHs, due to their polarity, and thus have a higher tendency to spread from contaminated sites via surface water and groundwater. We believe that oxy-PAHs should be included in monitoring programs at PAH-contaminated sites, even if a number of other toxicologically relevant compounds that may also be present, such as nitro-PAHs and azaarenes, are not monitored. This is because oxy-PAH levels are difficult to predict from the PAH levels, because their environmental behavior differs substantially from that of PAHs, and oxy-PAHs may be formed as PAHs are degraded.     

Weight and height at 4 and 7 years of age in children born to mothers with a high intake of fish contaminated with persistent organochlorine pollutants

In Sweden the main exposure route for persistent organochlorine pollutants (POP) is through consumption of fatty fish from the Baltic Sea (off the eastern coast). The present study aimed to investigate whether intrauterine exposure for POP may have negative impact on children's weight and height at 4 and 7 years of age, respectively. The study included 174 fishermen's wives from the Swedish east coast who had given birth to an infant with either low (n=55) or normal (n=119) birth weight, and 88 and 206 corresponding women from the Swedish west coast (where the fish is less polluted). Comparisons between the east and west coast cohorts were performed. In addition, blood samples were collected among the east coast women and the concentrations of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) in plasma was analyzed and estimated for the year of childbirth. There were no significant differences between the east and west coast cohorts regarding weight and height at 4 and 7 years of age. There were, however, significant negative associations between the estimated plasma concentrations of CB-153 during year of childbirth and weight at 4 and 7 years of age, respectively, among the normal birth weight children. The study gives only very weak support for the hypothesized association.     

The war on deciduous forest: Large-scale herbicide treatment in the Swedish boreal forest 1948 to 1984

At the mid-twentieth century the pace of the transformation of the Swedish forest increased. New methods; large-scale clearcutting, mechanization of logging and planting of seedlings were developed. Chemicals were used to control insects and unwanted tree species. The aims of this study were to elucidate the timing, chain of events and the spatial extent of the large-scale spraying of phenoxy acids in Swedish forests and the drivers for this practice. More than 700 000 hectares of productive forest land was sprayed and the main driving force was a strong will to transform the forest into high-yield coniferous forest plantations. We conclude that; (1) the use of herbicides in forestry in Sweden was done on a very large scale in the period 1948–1984, (2) the ecosystem legacy of herbicide spraying must be investigated and (3) a homogenous cadre of like-minded professionals working across commercial companies, state agencies and universities is dangerous.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01660-5.     

The Responsibility of Farmers,Public Authorities and Consumers for Safeguarding Bees Against Harmful Pesticides

Journal of Agricultural and Environmental Ethics - This study examines the influence of environmental values on consumer intentions to participate in agritourism through the theory of planned...