Seasonal baseline of nutrients and stable isotopes in a saline lake of Argentina: biogeochemical processes and river runoff effects

The seasonal variability of inorganic and organic nutrients and stable isotopes and their relations with plankton and environmental conditions were monitored in Lake Chasicó. Principal component analysis evidenced the strong influence of the river runoff on several biogeochemical variables. Silicate concentrations were controlled by diatom biomass and river discharge. Higher values of nitrate and soluble reactive phosphorus (SRP) indicated agricultural uses in the river basin. Elevated pH values (～9) inhibiting nitrification in the lake explained partially the dominance of ammonium: ～83 % of dissolved inorganic nitrogen (DIN). The low DIN/SRP ratio inferred nitrogen limitation, although the hypotheses of iron and CO₂ limitation are relevant in alkaline lakes. Particulate organic matter (POM) and dissolved organic matter (DOM) were mainly of autochthonous origin. The main allochthonous input was imported by the river as POM owning to the arid conditions. Dissolved organic carbon was likely top-down regulated by the bacterioplankton grazer Brachionus plicatilis. The δ¹³C signature was a good indicator of primary production and its values were influenced probably by CO₂ limitation. The δ¹⁵N did not evidence nitrogen fixation and suggested the effects of anthropogenic activities. The preservation of a good water quality in the lake is crucial for resource management.     

Beyond ‘trees are good’: Disservices,management costs,and tradeoffs in urban forestry

The provision of ecosystem services is a prominent rationale for urban greening, and there is a prevailing mantra that ‘trees are good’. However, understanding how urban trees contribute to sustainability must also consider disservices. In this perspective article, we discuss recent research on ecosystem disservices of urban trees, including infrastructure conflicts, health and safety impacts, aesthetic issues, and environmentally detrimental consequences, as well as management costs related to ecological disturbances and risk management. We also discuss tradeoffs regarding species selection and local conservation concerns, as well as the central role of human perception in the interpretation of ecosystem services and disservices, particularly the uncritical assertion that ‘everybody loves trees’. Urban forestry decision-making that fails to account for disservices can have unintended negative consequences for communities. Further research is needed regarding life cycle assessments, stakeholder decision-making, return-on-investment, and framings of services and disservices in urban forestry.     

Environmental and biological monitoring of benzene in traffic policemen, police drivers and rural outdoor male workers

To evaluate exposure to benzene in urban and rural areas, an investigation into personal exposure to benzene in traffic policemen, police drivers and rural (roadmen) male outdoor workers was carried out. Personal samples and data acquired using fixed monitoring stations located in different areas of the city were used to measure personal exposure to benzene in 62 non-smoker traffic policemen, 22 police drivers and 57 roadmen. Blood benzene, urinary trans-trans muconic acid (t,t-MA) and S-phenyl-mercapturic acid (S-PMA) were measured at the end of work shift in 62 non-smoker traffic policemen, 22 police drivers and 57 roadmen and 34 smoker traffic policemen, 21 police drivers and 53 roadmen. Exposure to benzene was similar among non-smoker traffic policemen and police drivers and higher among non-smoker urban workers compared to rural workers. Blood benzene, t,t-MA and S-PMA were similar among non-smoker traffic policemen and police drivers; blood benzene and t,t-MA were significantly higher in non-smoker urban workers compared to rural workers. Significant increases in t,t-MA were found in smokers vs. non-smokers. In non-smoker urban workers airborne benzene and blood benzene, and t,t-MA and S-PMA were significantly correlated. This study gives an evaluation of the exposure to benzene in an urban area, comparing people working in the street or in cars, to people working in a rural area. Benzene is a certain carcinogen for humans. The results we showed should lead to more in-depth studies about the effects on health of these categories of workers.     

Conceptual and Numerical Modeling of Radionuclide Transport and Retention in Near-Surface Systems

Scenarios of barrier failure and radionuclide release to the near-surface environment are important to consider within performance and safety assessments of repositories for nuclear waste. A geological repository for spent nuclear fuel is planned at Forsmark, Sweden. Conceptual and numerical reactive transport models were developed in order to assess the retention capacity of the Quaternary till and clay deposits for selected radionuclides, in the event of an activity release from the repository. The elements considered were carbon (C), chlorine (Cl), cesium (Cs), iodine (I), molybdenum (Mo), niobium (Nb), nickel (Ni), radium (Ra), selenium (Se), strontium (Sr), technetium (Tc), thorium (Th), and uranium (U). According to the numerical predictions, the repository-derived nuclides that would be most significantly retained are Th, Ni, and Cs, mainly through sorption onto clays, followed by U, C, Sr, and Ra, trapped by sorption and/or incorporation into mineral phases.     

Ecosystem Viable Yields

The World Summit on Sustainable Development (Johannesburg, 2002) encouraged the application of the ecosystem approach by 2010. However, at the same summit, the signatory States undertook to restore and exploit their stocks at maximum sustainable yield (MSY), a concept and practice without ecosystemic dimension, since MSY is computed species by species, on the basis of a monospecific model. Acknowledging this gap, we propose a definition of “ecosystem viable yields” (EVY) as yields compatible (a) with biological safety levels (over which biomasses can be maintained for all times) and (b) with an ecosystem dynamics. The difference from MSY is that this notion is not based on equilibrium but on viability theory, which offers advantages for robustness. For a generic class of multispecies models with harvesting, we provide explicit expressions for the EVY. We apply our approach to the anchovy–hake couple in the Peruvian upwelling ecosystem.     

Effects of gas flow rate, inlet concentration and temperature on the biofiltration of toluene vapors

In this work the variation in the elimination capacity of a biofilter as a function of the gas flow and toluene concentration was studied. A bioreactor 0.75 m high x 14.5 cm diameter was used, divided into three equal stages, using compost to support the microorganisms, and sea shells to control the pH. The biofiltration of toluene was evaluated for flows between 0.12 and 0.73 m(3)h(-1) in a concentration range of 1-3.2 gm(-3). It was observed that on increasing the toluene inlet load by 90% (from 37 to 70 gm(3)h(-1)), the conversion by the biofilter varied by only 5% (from 98% to 93%). The biofiltration system used achieved elimination capacities of up to 82 gm(-3)h(-1) for a toluene load of 100 gm(-3)h(-1).     

Phytoavailability and extractability of potassium,magnesium and manganese in calcareous soil amended with olive oil wastewater

Abstract

Land disposal of olive oil wastewater using it as a soil amendment requires a knowledge of the effects that its application may produce on the status of the mineral nutrients in the plant‐soil system. A pot experiment using calcareous soil was performed in a growth chamber to examine the effects of olive oil wastewater on the availability and postharvest soil extractability of K, Mg and Mn. The experiment included 6 treatments: two rates of olive oil wastewater, two mineral fertilizer treatments containing K (which supplied K in amounts equivalent to the K supplied by the olive oil wastewater treatments), a K‐free mineral fertilizer treatment, and a control. The pots were sown with ryegrass as the test plant, harvesting 3 times at intervals of one month. Olive oil wastewater has demonstrated a considerable capacity for supplying K that can be assimilated by the plant, tending in fact to surpass the mineral potassium fertilizer tested. The application of olive oil wastewater tends to reduce the concentration of Mg in the plant, similarly to the effect of adding mineral potassium fertilizer. An enhancement of Mn availability takes place in the soil amended with olive oil wastewater, which on occasion has produced Mn concentrations in plant that could be considered phytotoxic or at least excessive. After harvesting, we observed an increase in the amount of exchangeable K in soil with added industrial wastewater. However, these increases are lower than those in soil treated with mineral potassium fertilizer. The levels of exchangeable, carbonate‐bound, organic‐bound and residual Mg in soil were higher in treatments incorporating olive oil wastewater than in those with added mineral K, with the opposite tendency occurring in the amount of Fe‐Mn oxides‐bound Mg in soil. Treatments based on olive oil wastewater, especially in high doses, increased the amount of exchangeable and carbonate‐bound Mn in soil, in comparison with treatments adding mineral fertilizers with or without K. In contrast, the addition of industrial wastewater caused a drop in the amount of Fe‐Mn oxides‐bound and organic‐bound Mn in soil.     

Loading effect correction for real-time aethalometer measurements of fresh diesel soot

In this study, a correction was developed for the aethalometer to measure real-time black carbon (BC) concentrations in an environment dominated by fresh diesel soot. The relationship between the actual mass-specific absorption coefficient for BC and the BC-dependent attenuation coefficients was determined from experiments conducted in a diesel exposure chamber that provided constant concentrations of fine particulate matter (PM; PM(2.5); PM < 2.5 microm in aerodynamic diameter) from diesel exhaust. The aethalometer reported BC concentrations decreasing with time from 48.1 to 31.5 microg m(-3) when exposed to constant PM(2.5) concentrations of 55 +/- 1 microg m(-3) and b(scat) = 95 +/- 3 Mm(-1) from diesel exhaust. This apparent decrease in reported light-absorbing PM concentration was used to derive a correction K(ATN) for loading of strong light-absorbing particles onto or into the aethalometer filter tape, which was a function of attenuation of light at 880 nm by the embedded particles.