Modeling inorganic aerosols and their response to changes in precursor concentration in Mexico City

Based on data from the 1997 Investigación sobre Materia Particulada y Deterioro Atmosférico-Aerosol and Visibility Evaluation Research (IMADA-EVER) campaign and the inorganic aerosol model ISORROPIA, the response of inorganic aerosols to changes in precursor concentrations was calculated. The aerosol behavior is dominated by the abundance of ammonia and thus, changes in ammonia concentration are expected to have a small effect on particle concentrations. Changes in sulfate and nitrate are expected to lead to proportional reductions in inorganic fine particulate matter (PM2.5). Comparing the predictions of ISORROPIA with the observations, the lowest bias and error are achieved when the aerosols are assumed to be in the efflorescence branch. Including crustal species reduces the bias and error for nitrate but does not improve overall model performance. The estimated response of inorganic PM2.5 to changes in precursor concentrations is affected by the inclusion of crustal species in some cases, although average responses are comparable with and without crustal species. Observed concentrations of particle chloride suggest that gas phase concentrations of hydrogen chloride may not be negligible, and future measurement campaigns should include observations to test this hypothesis. Our ability to model aerosol behavior in Mexico City and, thus, design control strategies, is constrained primarily by a lack of observations of gas phase precursors. Future campaigns should focus in particular on better understanding the temporal and spatial distribution of ammonia concentrations. In addition, gas phase observations of nitric acid are needed, and a measure of particle water content will allow stable versus metastable aerosol behavior to be distinguished.     

Not drowning, waving!: Safety management and occupational culture in an Australian commercial fishing port

An ethnographic study of safety management was conducted in a commercial lobster fishing industry, in a small fishing town in Southern Australia. The objectives were to test the utility of the ethnographic method for exploring the nature of the relationship between occupational culture, workplace social organization, and safety management.Available accident data suggests this particular fishery may not have the same high incidence of occupational trauma normally attributed to commercial fishing. Changes in licensing laws and improved management of fish stocks have significantly reduced risk exposure. Participants in this study had a good understanding of their physical workplace risks, but accepted some of these with too few defences. Wear rates of personal flotation devices (PFDs) were below 1% for the study period.The paper suggests that participants do not have a strong learning culture, and links this to occupation-wide cultural assumptions, other external issues and safety management issues. Assessment of the social and cultural context of safety management can offer policy makers a ‘road-map’ to guide their interventions. The utility of ethnographic methods for this type of analysis is significant, and will be enhanced by improving the transparency of the research method.     

Off-Target Herbicide Deposition Associated with Treating Individual Trees

There are a wide variety of different herbicide treatment methods used to remove single trees. Each method (cut-stump, basal, foliar) has a unique amount of off-target disturbance that should be considered in selecting a treatment for use in management. We quantified the amount of off-target deposition that resulted from four conventional herbicide application methods: 1) basal, 2) cut-stump, 3) high-volume, hydraulic foliar, and 4) low-volume, backpack foliar. Basal and cut-stump herbicide treatments deposited up to 200 and 4000 times more herbicide (a.i. per unit area) at groundline than the low-volume and high-volume foliar treatments, respectively. On a per tree basis, basal and cut-stump treatments deposited nearly six times more total herbicide than high-volume foliar, and 68 times more than low-volume foliar. All of the herbicide deposited off-target landed within 0.6 m of the basal and cut-stump treatments, 3.7 m with the low-volume foliar, and 7.3 m with high-volume foliar methods. Off-target herbicide deposition resulted in affected areas with killed or damaged vegetation ranging in size from 0.36 m² (cut stump) to 7.08 m² (high-volume foliar). Deposition amounts and affected areas were greater with larger trees, compared to smaller ones. We observed that 48% of the total amount of herbicide applied per plot was deposited off-target with cut-stump treatment, compared to only 4% to 11% for the other treatments. We suspect this difference is due to applicator error with the cut-stump treatment, likely related to the type of spray device used to apply the treatment.     

Broiler diet modification and litter storage: impacts on phosphorus in litters, soils, and runoff

Modifying broiler diets to mitigate water quality concerns linked to excess phosphorus (P) in regions of intensive broiler production has recently increased. Our goals were to evaluate the effects of dietary modification, using phytase and reduced non-phytate phosphorus (NPP) supplementation, on P speciation in broiler litters, changes in litter P forms during long-term storage, and subsequent impacts of diets on P in runoff from litter-amended soils. Four diets containing two levels of NPP with and without phytase were fed to broilers in a three-flock floor pen study. After removal of the third flock, litters were stored for 440 d at their initial moisture content (MC; 24%) and at a MC of 40%. Litter P fractions and orthophosphate and phytate P concentrations were determined before and after storage. After storage, litters were incorporated with a sandy and silt loam and simulated rainfall was applied. Phytase and reduced dietary NPP significantly reduced litter total P. Reducing dietary NPP decreased water-extractable inorganic phosphorus (IP) and the addition of dietary phytase reduced NaOH- and HCl-extractable organic P in litter, which correlated well with orthophosphate and phytic acid measured by 31P nuclear magnetic resonance (NMR), respectively. Although dry storage caused little change in P speciation, wet storage increased concentrations of water-soluble IP, which increased reactive P in runoff from litter-amended soils. Therefore, diet modification with phytase and reduced NPP could be effective in reducing P additions on a watershed scale. Moreover, efforts to minimize litter MC during storage may reduce the potential for dissolved P losses in runoff.     

Proactive monitoring and adaptive management of social carrying capacity in Arches National Park: an application of computer simulation modeling

Public visits to parks and protected areas continue to increase and may threaten the integrity of natural and cultural resources and the quality of the visitor experience. Scientists and managers have adopted the concept of carrying capacity to address the impacts of visitor use. In the context of outdoor recreation, the social component of carrying capacity refers to the level of visitor use that can be accommodated in parks and protected areas without diminishing the quality of the visitor experience to an unacceptable degree. This study expands and illustrates the use of computer simulation modeling as a tool for proactive monitoring and adaptive management of social carrying capacity at Arches National Park. A travel simulation model of daily visitor use throughout the Park's road and trail network and at selected attraction sites was developed, and simulations were conducted to estimate a daily social carrying capacity for Delicate Arch, an attraction site in Arches National Park, and for the Park as a whole. Further, a series of simulations were conducted to estimate the effect of a mandatory shuttle bus system on daily social carrying capacity of Delicate Arch to illustrate how computer simulation modeling can be used as a tool to facilitate adaptive management of social carrying capacity.     

Seaborne petrochemical spill analysis within the United States, 1992-1999

Through discussion of causative factors and examination of historical data, petrochemical spill prevention in US waters is reviewed. Unintentional petrochemical outflow is analyzed in a comprehensive manner and presented as a hierarchical sequence of antecedent events to reveal the trends of causative factors leading to release. Specifically, a seaborne petrochemical spill is examined in terms of four basic, antecedent events: (1) an underway source, (2) a failure incident, (3) a marine accident capable of breaching the hull and cargo block, and (4) the onset of outflow. These events are further subdivided into underlying, contributing events to form a causative framework for spill prevention. While a hierarchical review is not necessary to uncover the elements of causation, it does provide a comprehensive and logical structure that clearly defines these elements in terms of occurrence frequency and contribution to resulting outflow. It is found that relatively small, frequent spills less than 40,000 liters (10,567 gallons), attributable to human operator failures, leading to grounding, and cargo transfer system failure accidents, dominate US seaborne petrochemical outflow from 1992 to 1999. Given the frequency of groundings, structural reinforcement regulations such as those contained in the Oil Pollution Act of 1990 (requiring double hulls) appear well justified. However, passive restraint systems are secondary to the need for vigilant training and licensing of tank vessel operators.     

Beyond the environmental Kuznets curve: Do combined impacts of air transport and rail transport matter for environmental sustainability amidst energy use in E7 economies?

Environment, Development and Sustainability - This study is motivated by the United Nations Sustainable Development Goals (UN-SDG-7,8,11,12 and 13) on the need for clean and responsible energy...     

Similar policing rates of eggs laid by virgin and mated honey-bee queens

Worker-policing is a well-documented mechanism that maintains functional worker sterility in queenright honey-bee colonies. Unknown, however, is the source of the egg-marking signal that is thought to be produced by the queen and used by policing workers to discriminate between queen- and worker-laid eggs. Here we investigate whether mating is necessary for the queen to produce the egg-marking signal. We compare the removal rate of eggs laid by virgin queens and compare this rate with that of eggs laid by mated queens. Our results show that mating does not affect the acceptability of eggs, suggesting that physiological changes linked to the act of mating do not play a role in the production of the queens egg-marking signal.     

Effects of cross-feeding anarchistic and wild type honey bees: anarchistic workers are not queen-like

Unlike normal (wild type) honey bee ( Apis mellifera) colonies, 'anarchistic' colonies are characterised by workers that activate their ovaries in the presence of the queen and brood and by the ability of their workers to lay eggs that evade worker policing. In the Cape honey bee ( A. m. capensis), female larvae can manipulate non- capensis nurse workers such that they receive more larval food and develop into worker-queen intermediates or intercastes. We speculated that, in anarchistic colonies, larvae might produce signals that result in excessive feeding of female larvae. Excessively fed female larvae may then develop into reproductively active workers. In this study we cross-fostered anarchistic and wild type brood and investigated the effect of cross-fostering on the amount of food fed to larvae and on the morphology of the resulting workers. We show that anarchistic larvae do not manipulate wild type nurse workers into feeding them more, nor do anarchistic workers develop into worker-queen intermediates. On the contrary, anarchistic larvae are fed less than wild type larvae and anarchistic workers seem to be poor nurses in that they feed larvae less, irrespective of brood genotype.