Modeling Evidence of Incloud Transformation Of Sulfur Dioxide to Sulfate

Methylene chloride (CH₂Cl₂) is presently under study by the U.S. EPA and other agencies to determine if the compound presents an unreasonable risk to human health and to determine if regulatory action is needed to reduce the risk. This paper describes one portion of the study which required the development and validation of a method of sampling and analysis for source emission measurements.

Prior to source sampling, laboratory experiments were conducted to determine the best sample container in which to collect an integrated sample. It was found that CH₂Cl₂ remained stable in Tedlar bags for at least four weeks. The analytical method selected was gas chromatography with flame ionization detection (GC/FID). During the field portion of the study, both manufacturer and user emission sources of CH₂Cl₂ were tested. Multiple sets of simultaneous quadruplicate bag samples were collected to determine the precision of both sampling and analysis in the field. All samples were analyzed at the test site after collection and then returned to Research Triangle Park. Samples were subsequently reanalyzed in the laboratories of Radian and the U.S. EPA using three GC/FID instruments and two types of GC columns. The range of concentrations from the sources was 100 ppm to 27,000 ppm CH₂Cl₂. A statistical analysis of samples collected simultaneously showed no difference in the samples, proving good precision In both sampling and analysis. Some of the sample bags returned from the test sites developed leaks indicating that immediate on-site analysis is best. A comparison of results obtained in the field and the two laboratories showed that interand intra-laboratory precision was within 10 percent.     

Scientists’ warning to humanity on the freshwater biodiversity crisis

Freshwater ecosystems provide irreplaceable services for both nature and society. The quality and quantity of freshwater affect biogeochemical processes and ecological dynamics that determine biodiversity, ecosystem productivity, and human health and welfare at local, regional and global scales. Freshwater ecosystems and their associated riparian habitats are amongst the most biologically diverse on Earth, and have inestimable economic, health, cultural, scientific and educational values. Yet human impacts to lakes, rivers, streams, wetlands and groundwater are dramatically reducing biodiversity and robbing critical natural resources and services from current and future generations. Freshwater biodiversity is declining rapidly on every continent and in every major river basin on Earth, and this degradation is occurring more rapidly than in terrestrial ecosystems. Currently, about one third of all global freshwater discharges pass through human agricultural, industrial or urban infrastructure. About one fifth of the Earth’s arable land is now already equipped for irrigation, including all the most productive lands, and this proportion is projected to surpass one third by midcentury to feed the rapidly expanding populations of humans and commensal species, especially poultry and ruminant livestock. Less than one fifth of the world’s preindustrial freshwater wetlands remain, and this proportion is projected to decline to under one tenth by midcentury, with imminent threats from water transfer megaprojects in Brazil and India, and coastal wetland drainage megaprojects in China. The Living Planet Index for freshwater vertebrate populations has declined to just one third that of 1970, and is projected to sink below one fifth by midcentury. A linear model of global economic expansion yields the chilling prediction that human utilization of critical freshwater resources will approach one half of the Earth’s total capacity by midcentury. Although the magnitude and growth of the human freshwater footprint are greater than is generally understood by policy makers, the news media, or the general public, slowing and reversing dramatic losses of freshwater species and ecosystems is still possible. We recommend a set of urgent policy actions that promote clean water, conserve watershed services, and restore freshwater ecosystems and their vital services. Effective management of freshwater resources and ecosystems must be ranked amongst humanity’s highest priorities.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01318-8) contains supplementary material, which is available to authorized users.     

Dissolution and solubility of trace metals from natural and anthropogenic aerosol particulate matter

An open flow reactor is used to simulate the dissolution process of mineral aerosol particles in atmospheric water droplets. Data on dissolution kinetic and solubility are provided for the major trace metals from two kinds of matrix: alumino-silicated and carbonaceous sample. The results emphasise that the metals contained in the carbonaceous aerosols are easier dissolved than in the alumino-silicated particles. The released concentrations are not related to the total metal composition or the origin of particles, but are directly associated with the type of liaisons whereby the metals are bound in the solid matrix. Thus, the metals coming from carbonaceous particles are adsorbed impurities or salts and hence are very soluble and with a dissolution hardly dependent on pH, whereas the metals dissolved from alumino-silicated particles are less soluble, notably the ones constitutive of the matrix network (Fe, Mn), and with a dissolution highly influenced by pH. Consequently, in the regions with an anthropogenic influence, the dissolved concentrations of metals found in the atmospheric waters are mainly governed by the elemental carbon content. Moreover, it appears that the dissolution kinetic of metals is not constant as a function of time. The dissolution rates are very rapid in the first 20 min of leaching and then they are stabilised to lower values in comparison to initial rates. By consequence, the total dissolved metal content is provided after the first 20 min of the droplet lifetime. For this reason, the effects of trace metals on the atmospheric aqueous chemistry and as atmospheric wet input to the marine biota are maximal for "aged" droplets.     

Absorption cross-sections of atmospheric constituents: NO2, O2, and H2O

Absorption spectroscopy, which is widely used for concentration measurements of tropospheric and stratospheric compounds, requires precise values of the absorption cross-sections of the measured species. NO₂, O₂ and its collision-induced absorption spectrum, and H₂O absorption cross-sections have been measured at temperature and pressure conditions prevailing in the Earth’s atmosphere. Corrections to the generally accepted analysis procedures used to resolve the convolution problem are also proposed.     

History of mercury use and environmental contamination at the Oak Ridge Y-12 Plant

Between 1950 and 1963 approximately 11 million kilograms of mercury (Hg) were used at the Oak Ridge Y-12 National Security Complex (Y-12 NSC) for lithium isotope separation processes. About 3% of the Hg was lost to the air, soil and rock under facilities, and East Fork Poplar Creek (EFPC) which originates in the plant site. Smaller amounts of Hg were used at other Oak Ridge facilities with similar results. Although the primary Hg discharges from Y-12 NSC stopped in 1963, small amounts of Hg continue to be released into the creek from point sources and diffuse contaminated soil and groundwater sources within Y-12 NSC. Mercury concentration in EFPC has decreased 85% from ∼2000 ng/L in the 1980s. In general, methylmercury concentrations in water and in fish have not declined in response to improvements in water quality and exhibit trends of increasing concentration in some cases.     

Bacterial periphytic communities related to mercury methylation within aquatic plant roots from a temperate freshwater lake (South-Western France)

Environmental Science and Pollution Research - Macrophyte floating roots are considered as hotspots for methylmercury (MeHg) production in aquatic ecosystems through microbial activity....     

Activity-dependent labeling of oxygenase enzymes in a trichloroethene-contaminated groundwater site

A variety of naturally occurring bacteria produce enzymes that cometabolically degrade trichloroethene (TCE), including organisms with aerobic oxygenases. Groundwater contaminated with TCE was collected from the aerobic region of the Test Area North site of the Idaho National Laboratory. Samples were evaluated with enzyme activity probes, and resulted in measurable detection of toluene oxygenase activity (6-79% of the total microbial cells). Wells from both inside and outside contaminated plume showed activity. Toluene oxygenase-specific PCR primers determined that toluene-degrading genes were present in all groundwater samples evaluated. In addition, bacterial isolates were obtained and possessed toluene oxygenase enzymes, demonstrated activity, and were dominated by the phylotype Pseudomonas. This study demonstrated, through the use of enzymatic probes and oxygenase gene identification, that indigenous microorganisms at a contaminated site were cometabolically active. Documentation such as this can be used to substantiate observations of natural attenuation of TCE-contaminated groundwater plumes.     

Toxic effects of Pb2+ on growth of cowpea (Vigna unguiculata)

A concentration as low as 1 microM lead (Pb) is highly toxic to plants, but previous studies have typically related plant growth to the total amount of Pb added to a solution. In the present experiment, the relative fresh mass of cowpea (Vigna unguiculata) was reduced by 10% at a Pb2+ activity of 0.2 microM for the shoots and at a Pb2+ activity of 0.06 microM for the roots. The primary site of Pb2+ toxicity was the root, causing severe reductions in root growth, loss of apical dominance (shown by an increase in branching per unit root length), the formation of localized swellings behind the root tips (due to the initiation of lateral roots), and the bending of some root tips. In the root, Pb was found to accumulate primarily within the cell walls and intercellular spaces.     

Multi-generation cadmium acclimation and tolerance in Daphnia magna Straus

The cladoceran Daphnia magna was acclimated for seven generations to cadmium concentrations ranging from 0 (control) to 250 microg/l Cd (corresponding to a free ion activity of 4.60 nM Cd2+). Acute and chronic cadmium tolerance as well as cadmium accumulation were monitored as a function of acclimation time. After two to three generations of acclimation to concentrations ranging from 0.23 to 1.11 nM Cd2+ increases in acute tolerance were maximal (factor 7.2) and significant. Acclimation for seven generations to the same acclimation concentrations did result in an increased chronic cadmium tolerance (21 days EC50 values increased). Organisms acclimated to 1.93 nM Cd2+ were equally or more sensitive than non-acclimated daphnids in acute and chronic toxicity tests. Cadmium contents in D. magna increased significantly as a function of the acclimation concentration. Maximum body burdens of 236+/-30 microg Cd/g dry weight were measured in organisms exposed to 4.60 nM Cd2+, but detoxification mechanisms were only successful up to 82+/-20 microg Cd/g dry weight as this concentration did not cause major decreases in survival and reproduction in chronic toxicity tests. As the potential positive effect of acclimation on cadmium tolerance disappeared with successive acclimation generations and increasing acclimation concentrations, it is concluded that multi-generation acclimation studies are important for the evaluation of the long-term effects of environmental toxicants.     

‘Management Standards’ and work-related stress in Great Britain: Progress on their implementation

The aim of this paper is to identify what constituted barriers to progress in the implementation of the Management Standards for preventing and reducing work-related stress nationally, an approach advocated by the Health and Safety Executive in Great Britain. Data were collected from more than 100 public sector organisations through inspector visits and research interviews. Findings show that under supportive contexts, organisations were able to follow the process of a stepwise method for assessing psychosocial risks and implementing interventions using HSE assessment tools and guidance. Main enabling factors included the active and visible support from senior management, human resource departments, and line managers; regular communications on progress, sufficient organisational capability in terms of resources and expertise; departmental/team level assessment as opposed to an overall corporate wide assessment, and involvement of key stakeholders (e.g. Trade Union, employees). Some of the critical barriers across many public sector organisations included in this study were: major or on-going organisational changes; lack of organisational capability; and the resource intensive aspect of the method requiring focus groups in addition to stress survey data. Implications of the findings for policy development are discussed.