Studies of salt-solution aerosols—XIII effect of surface-active substances on the stability of aqueous salt solution aerosols

The stability of aqueous salt-solution aerosols was estimated by measuring the half-decay times of particle number, the particle coagulation rate constants, and the size spectra of particles sedimenting to the bottom of a test chamber.These parameters were studied in the presence of organic materials. Two techniques were employed for adding the organics; back blending the vapors with the air used to aerosolize the particles, and dissolving them in the salt solution prior to spraying. Organic substances used included ethyl alcohol, acetone, ethyl acetate, benzene, toluene, carbon tetrachloride, glycerine, and a nonionic surfactant.The experiments suggest that the cushion of sorbed organic vapor surrounding the particles impairs their collisions with one another, and the vapor-pressure characteristics of the organic substances support such a view.     

Observation of carbonaceous aerosols during 2006–2009 in Nyainqêntanglha Mountains and the implications for glaciers

Atmospheric carbonaceous aerosols were sampled discontinuously from July 2006 to December 2009 at Nam Co Comprehensive Observation and Research Station (NCOS) in the central Tibetan Plateau (TP). The mean daily concentration of carbonaceous aerosols increased from 268 to 330 ng?m^?3, and pollution episodes could significantly increase the mean level of carbonaceous aerosols in the total mass concentration. Organic carbon was the main component of carbonaceous aerosols at NCOS, and black carbon (BC) accounted for 5.8 %. Seven-day air masses backward trajectories calculated by the Hybrid Single-Particle Lagrangian Integrated Trajectory model and the aerosol optical depth distribution in the TP and South Asia both suggested that atmospheric pollutants emitted from Northern India and South Asia could penetrate into central TP by southwest winds. Due to the seasonal variations of emission sources and regional atmospheric conditions, calculated BC deposition flux in the nonmonsoon season was higher than that in the monsoon season. Increased BC concentration in snowpack in winter from 2007 to 2009 indicated that the atmospheric environment in central TP became more polluted and the influences from human activities have strengthened. Pollution episodes could significantly increase BC concentrations in the snowpack on a seasonal scale, which would furthermore affect the surface albedo.     

On the use of Teflon®bags for photochemical experiments

Experiments were carried out to characterize FEP (fluorinated ethylene-propylene copolymers) Teflon^®bags as reactors for studies of photochemical reactions in sunlight of pollutants at low concentrations. Measurements of toluene loss, carbon monoxide oxidation and ozone formation in zero air in sun irradiated bags demonstrated a significant reactivity caused by the Teflon^®film. The results indicate that such bags can be unsuitable for photochemical experiments at low (ppb) concentration levels.     

A comparison of numerical methods for solving the advection equation—II

Five algorithms and their variations for solving the advection equation were compared in terms of their accuracy, speed and storage requirements. The algorithms are a chapeau-function method including mass-lumping, Forester's method, a method called Filtering Remedy and Methodology, a Hermite-cubic orthogonal-collocation method and a quadratic function method. The test problem was the rotation of a cosine-shaped hill of concentration in a two-dimensional circular velocity field at three different time increments (or angular velocities). The forward-Euler time-integration scheme coupled with a balancing diffusion term was extensively used and was found to be superior to the Crank-Nicolson scheme in accuracy for the methods considered. Together with the results of Part I (Atmospheric Environment17, 11–24, 1983), Forester's method applied to the chapeau-function solution appears to be the best method for solving the advection equation in air-pollution modeling. The combined method retains the peak value well, has high accuracy with little or no negative concentration region, and requires short execution time and minimal memory storage.     

On the use of PAH molecular diagnostic ratios in sewage sludge for the understanding of the PAH sources. Is this use appropriate?

The concentrations ratios of specific pairs of polycyclic aromatic hydrocarbons (PAHs) are widely used for the qualitative determination of the PAHs sources. These ratios are called PAHs molecular diagnostic ratios and are commonly used for PAHs concentrations in air, soils and sediments. Some scientists have extended the use of these ratios also for sewage sludges, suggesting that calculation of these ratios by individual PAHs concentrations can be as effective as in soils or sediments. This paper describes the reason why the PAH molecular ratios calculated from sewage sludge concentrations should not be used for the understanding of the PAH sources.     

Modeling farmers’ intention for safe pesticide use: the role of risk perception and use of information sources

Environmental Science and Pollution Research - Intention for safe pesticide use plays a crucial role in the mode of pesticide spraying, but several factors are involved in the formation of...     

X-ray diffraction investigation of atmospheric aerosols in the 0.3–1.0 μm aerodynamic size range

X-ray powder diffraction analysis was used to characterize submicrometer aerosol samples collected using a modified Lundgren cascade impactor. The Debye-Scherrer method was found to be particularly convenient, for the particles could be easily transferred to an X-ray capillary which could then be sealed to limit chemical changes. Several sets of aerosols were investigated in order to demonstrate the sensitivity and range of applicability of the combined impactor-Debye-Scherrer approach. The findings are varied and are reported here. Numerous compounds were identified. Of particular interest was the observation of nitrates in the form of ammonium nitrate-ammonium sulfate double salts. Earlier infrared characterizations of ambient aerosols in the MAP3S program had demonstrated periodic variations in sulfate acidity with time. The X-ray diffraction examination of archived samples from that study identified the chemical compound responsible for the acidity to be (NH₄)₃H(SO₄)₂ primarily, in amounts which varied with time. Good agreement was observed between the infrared and X-ray methods for acidity evaluation.     

Is the size distribution of urban aerosols determined by thermodynamic equilibrium?: An application to Southern California

A size-resolved equilibrium model, SELIQUID, is presented and used to simulate the size–composition distribution of semi-volatile inorganic aerosol in an urban environment. The model uses the efflorescence branch of aerosol behavior to predict the equilibrium partitioning of the aerosol components between the gas phase and a size-resolved aerosol population over the entire RH domain. Predictions of SELIQUID are compared against size-resolved composition measurements at different locations during the Southern California Air Quality Study. Based on the modeling results, the size distribution of sub-micrometer nitrate and ammonium can be determined by thermodynamic equilibrium when the RH>60%. In cases where the RH<60%, the assumption that all aerosol particles are metastable liquid solutions may introduce unacceptable errors. On the other hand, the equilibrium assumption, in some cases at least, introduces errors in the calculation of the coarse (particles with diameter >1 μm or so) nitrate and ammonium that increase with particle size. Finally, the inclusion of crustal species is important in modeling the size distribution of coarse inorganic aerosols when the concentration of these species is high. The effect of these crustal species can be complex and counterintuitive.     

Mathematical model of Boltzmann’s sigmoidal equation applicable to the spreading of the coronavirus (Covid-19) waves

Environmental Science and Pollution Research - Currently, investigations are intensively conducted on modeling, forecasting, and studying the dynamic spread of coronavirus (Covid-19) new pandemic....     

Assessment of human health risk related to metals by the use of biomonitors in the province of Córdoba, Argentina

The evaluation of metal contents in the environment is of vital importance for the assessment of human exposure. Thus the species Usnea amblyoclada, Ramalina celastri and Tillandsia capillaris were tested as bioaccumulators of transition metals in the urban area of Córdoba city, Argentina. The level of metals on biomonitors was compared to that of total deposition samples. All three species discriminated zones within the urban area of Córdoba city with different pollution levels; they revealed high levels of Zn in the downtown area and confirmed high levels of some transition metals in an industrial area. The correlation analysis revealed that the lichen R. celastri had the highest correlation rates with total deposition samples, suggesting it is a valuable biomonitor of atmospheric pollution. A significant relationship was also observed between respiratory diseases in children and the contents of metal accumulated in R. celastri and T. capillaris, indicating their usefulness when assessing human exposure to metals.     

COVID-19: unbalanced management of occupational risks—case of the analysis of the chemical risk related to the use of disinfectants in the dairy industry in Morocco

Environmental Science and Pollution Research - Moroccan employers have a strong responsibility for the safety and health of their employees in the workplace and for protecting them from the risk of...     

Plant–bacteria partnerships for the remediation of hydrocarbon contaminated soils

Plant–bacteria partnerships have been extensively studied and applied to improve crop yield. In addition to their application in agriculture, a promising field to exploit plant–bacteria partnerships is the remediation of soil and water polluted with hydrocarbons. Application of effective plant–bacteria partnerships for the remediation of hydrocarbons depend mainly on the presence and metabolic activities of plant associated rhizo- and endophytic bacteria possessing specific genes required for the degradation of hydrocarbon pollutants. Plants and their associated bacteria interact with each other whereby plant supplies the bacteria with a special carbon source that stimulates the bacteria to degrade organic contaminants in the soil. In return, plant associated-bacteria can support their host plant to overcome contaminated-induced stress responses, and improve plant growth and development. In addition, plants further get benefits from their associated-bacteria possessing hydrocarbon-degradation potential, leading to enhanced hydrocarbon mineralization and lowering of both phytotoxicity and evapotranspiration of volatile hydrocarbons. A better understanding of plant–bacteria partnerships could be exploited to enhance the remediation of hydrocarbon contaminated soils in conjunction with sustainable production of non-food crops for biomass and biofuel production.     

Quality of the Solimões River water for domestic use by the riverine community situated in Manacapuru-Amazonas-Brazil

The Amazon has the largest watershed in the world, with abundant fresh water reserves. Such abundance contrasts with the quality of the water consumed in the riverine communities. This work highlights the importance of assessing the quality of water of the Solimões River in the stretch situated opposite the Community Nossa Senhora das Graças-Costa do Pesqueiro, in front of the town of Manacapuru-Amazonas-Brazil. The research aimed to evaluate environmental indicators for the quality of the river water as well as in households in this community, according to the regional seasonality. The monitored parameters such as conductivity, dissolved oxygen, turbidity, color, pH, nitrate, nitrite, and sulfate were compared with the water quality standards in force in Brazil. Values well above the maximum level allowed (MLA) for color and turbidity parameters were found in some households, indicating that the water collected from the river is not getting appropriate treatment. The analysis of the correlation matrix of the parameters in the flood period of the river evidenced high correlation among dissolved oxygen (D.O), NO₃ ^?, Cl^?, SO₄ ^2?, and color. In this study, by principal component analysis (PCA), it was observed that the characteristics of the water, obtained from the river to be consumed in the households, in the flood period showed similarities with the river water samples, indicating absence of efficient treatment for human consumption.     

Development and application of LC–APCI–MS method for biomonitoring of animal and human exposure to imidacloprid

Imidacloprid (IMI) is a relatively new neuro-active neonicotinoid insecticide and nowadays one of the largest selling insecticides worldwide. In the present study a LC–APCI–MS based method was developed and validated for the quantification of imidacloprid and its main metabolite 6-chloronicotinic acid (6-CINA) in urine and hair specimens. The method was tested in biomonitoring of intentionally exposed animals and subsequently applied for biomonitoring of Cretan urban and rural population.     

Use of the MicroResp™ method to assess pollution-induced community tolerance to metals for lotic biofilms

Understanding the ecological status of aquatic ecosystems and the impact of anthropogenic contamination requires correlating exposure to toxicants with impact on biological communities. Several tools exist for assessing the ecotoxicity of substances, but there is still a need for new tools that are ecologically relevant and easy to use. We have developed a protocol based on the substrate-induced respiration of a river biofilm community, using the MicroResp™ technique, in a pollution-induced community tolerance approach. The results show that MicroResp™ can be used in bioassays to assess the toxicity toward biofilm communities of a wide range of metals (Cu, Zn, Cd, Ag, Ni, Fe, Co, Al and As). Moreover, a community-level physiological profile based on the mineralization of different carbon substrates was established. Finally, the utility of MicroResp™ was confirmed in an in-situ study showing gradient of tolerance to copper correlated to a contamination gradient of this metal in a small river.     

Influence of the presence of ruthenium on the activity and stability of Co–Mg–Al-based catalysts in CO2 reforming of methane for syngas production

Environmental Science and Pollution Research - Hydrogen production by methane dry reforming is an important yet challenging process. A performing catalyst will favor the thermodynamic equilibrium...     

Deposition of acidic components and heavy metals in the Federal Republic of Germany for the period 1979–1981

The paper discusses the results of the measurement of wet and dry deposition of sulfate, nitrate, chloride and heavy metal aerosols which were obtained from a network established in the Federal Republic of Germany during 1979 to 1981. The results characterize the deposition-pattern with respect to time and space.     

Emission inventory for greenhouse gases in the City of Barcelona, 1987–1996

Emissions of greenhouse gases for the City of Barcelona are estimated for the period 1987–1994. The sources considered are: public and private transportation; industrial, commercial and domestic activities; and municipal solid waste disposal. The results show that the main source of CO₂ emissions in Barcelona is private vehicle transportation, which accounts, as an average for the period studied, for 35% of total emissions. The second most important source is the municipal solid waste landfill facility of the city (24% of total emissions). The percentages for the remaining sources under consideration were: 14% electricity, 12% natural gas, 5% incineration, and 3% liquefied petroleum gases. However, the values for CO₂ emissions per inhabitant over the period studied are lower than those for any other industrialized city available for comparison. This is closely related to the high percentage of electricity generation from nuclear power stations and hydro power facilities, and also to the extensive use of natural gas for domestic uses.