Effect of compost treatment of sewage sludge on nitrogen behavior in two soils

This work aims to evaluate the effects of compost treatment of digested sewage sludge on nitrogen behavior in two soils, a Spodosol and an Oxisol soil. Digested sewage sludge was composted with sawdust and woodchips, diluting the total nitrogen to one-fourth (dry mass basis) of its original value. Then, sludge and compost were added to the two soils on an equivalent dry weight basis to consider the risk of NO3- -N leaching. Compost treatment of sewage sludge has slowed down the release of mineral-N to half in the Spodosol and to one-third in Oxisol soil. As a result, NO3- -N concentrations in soils incubated with compost were less than half of the amounts found from soils incubated with digested sludge. Estimates were made of the maximum monthly nitrate to leach from the four combinations of soil and sludge treatment. Application of digested sludge, at a higher nitrogen application rate, resulted in a higher nitrate leaching potential than application of the compost product. Soil type also played an important role, with the Oxisol having slightly higher estimated leaching potential than the Spodosol. The higher nitrate release rate in the Oxisol is counterbalanced by its higher field capacity to lessen the expected difference between the two soils.     

Young females' attention toward road safety images: An ERP study of the revised reinforcement sensitivity theory

Objective: This study examined whether reward and punishment sensitivities, as conceptualized by Gray and McNaughton's revised reinforcement sensitivity theory (RST), influenced young female drivers' attention toward a series of positive and negative antispeeding advertisement images. Young females' increasing crash risk is associated with their engagement in risky behaviors, which, in turn, has been associated with a stronger behavioral approach system (BAS; sensitive to rewards). It was predicted that individuals with a stronger BAS would elicit larger N100 and N200 mean amplitudes (reflecting greater attention) toward the positive images. Similar associations were predicted in relation to the fight–flight–freeze system (FFFS; sensitive to punishments) for negative images.

Method: Twenty-four female drivers (17–25 years; final N = 16) completed Corr-Cooper's RST-Personality Questionnaire, prior to undergoing an event-related potential computerized visual task (i.e., oddball paradigm) that included positive, negative, and neutral images as targets against checkerboard image distractors.

Results: Contrary to expectations, individuals with a stronger BAS (Reward Reactivity and Impulsivity) demonstrated significantly larger N200 mean amplitudes at the Cz electrode site on presentation of the negative images than those with a weaker BAS. No other significant RST effects were found.

Conclusions: These findings provide some preliminary objective support for the use of negative emotion-based road safety advertisements for young females. Further, this study provides support for using psychophysiological measures to enhance understanding of traffic injury persuasion.     

Public preferences for timeliness and quality of mine site rehabilitation. The case of bauxite mining in Western Australia

Government departments that regulate environmental management for mining have a range of choices about the timing and quality of rehabilitation. Economic theory suggests that the cost incurred by firms should relate to the social cost of the environmental damage, however, there has been little work done on non-market values for mine rehabilitation. This study uses choice modelling to assess these issues for bauxite mining in state owned native forest in south-west Australia. The results show that the public place a relatively high value on the re-creation of vertebrate habitat and would prefer in situ mine rehabilitation over environmental offsets. Alcoa's current rehabilitation practices appear to be supported by the preferences revealed in this study.     

Evaluation of the SAPRC-07 mechanism against CSIRO smog chamber data

The updated SAPRC-07 mechanism was evaluated against data from experiments performed in the CSIRO smog chamber. The mechanism predictions have been compared to experimental results as well as predictions by SAPRC-99.Experiments were performed using either toluene or m-xylene in the presence of NO_x at sub-0.1 ppmv concentrations. For the majority of m-xylene experiments, the modelled Δ(O₃–NO) concentration was within 20% of observed values for both SAPRC mechanisms. However during the oxidation of toluene the production of radicals was poorly predicted, with final Δ(O₃–NO) concentration under-predicted by up to 60%. The predictions of major oxidants from isoprene oxidation were in good agreement with observed values. For the NO_x-limited conditions however, the ozone concentration predicted by both mechanisms were under-predicted by approximately 20% in the five experiments tested.The performance of the SAPRC-07 mechanism was also evaluated against twelve evaporated fuel experiments. Two types of evaporative mode experiments were performed: headspace evaporated fuel and wholly evaporated fuel. The major difference was a significantly higher concentration of aromatic hydrocarbons and larger alkane products in wholly evaporated fuels. For headspace evaporated fuel experiments both SAPRC mechanisms were in good agreement with experimental results. For wholly evaporated experiments the average Δ(O₃–NO) model error was ?25% with SAPRC-07 compared to less than ?5% for SAPRC-99. Updates to the photolysis data for dicarbonyls, the light source used and the experimental conditions under which these experiments were performed are possible causes for the discrepancy between SAPRC-99 and -07 predictions for wholly evaporated experiments.     

Chemical and Physical Controls on the Oxygen Regime of Ice‐Covered Arctic Lakes and Reservoirs1

Abstract: We examined the chemical, morphological, and anthropogenic controls on winter‐oxygen biogeochemistry in ice‐covered lakes and reservoirs on the North Slope of Alaska. We measured dissolved oxygen (DO), solute concentrations, water depth, and ice thickness at three natural thaw lakes and four reservoirs (flooded gravel mines) for two winters. In all seven study sites, DO concentration and pH decreased with depth, and temporally through the winter (November to April). DO concentration was four to six times greater in the deeper reservoirs (8‐13 mg/l) compared with shallow natural lakes (ca. 2 mg/l). Lakes and reservoirs with high dissolved organic carbon (DOC) concentration were susceptible to large decreases in oxygen over the winter. DO concentration differed markedly between years, but was not attributed to changes in water‐use or winter water‐chemistry. Alternatively, we suggest that dissolved oxygen concentration was lower during freeze‐up, possibly associated with higher lake‐productivity during the summer. Our results suggest that current water‐use practices on the North Slope of Alaska caused little to no change in DO concentration over the winter. In particular, considering the high pumping activity and shallow depth, lakes with low DOC concentration (≤6 mg/l) showed strong resilience to change in chemistry over the winter. We suggest that both lake and reservoir depth, and DOC concentration are key factors influencing oxygen consumption in ice‐covered arctic lakes and reservoirs.     

Implications of differing input data sources and approaches upon forest carbon stock estimation

Site index is an important forest inventory attribute that relates productivity and growth expectation of forests over time. In forest inventory programs, site index is used in conjunction with other forest inventory attributes (i.e., height, age) for the estimation of stand volume. In turn, stand volumes are used to estimate biomass (and biomass components) and enable conversion to carbon. In this research, we explore the implications and consequences of different estimates of site index on carbon stock characterization for a 2,500-ha Douglas-fir-dominated landscape located on Eastern Vancouver Island, British Columbia, Canada. We compared site index estimates from an existing forest inventory to estimates generated from a combination of forest inventory and light detection and ranging (LIDAR)-derived attributes and then examined the resultant differences in biomass estimates generated from a carbon budget model (Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3)). Significant differences were found between the original and LIDAR-derived site indices for all species types and for the resulting 5-m site classes (p?<?0.001). The LIDAR-derived site class was greater than the original site class for 42% of stands; however, 77% of stands were within ±1 site class of the original class. Differences in biomass estimates between the model scenarios were significant for both total stand biomass and biomass per hectare (p?<?0.001); differences for Douglas-fir-dominated stands (representing 85% of all stands) were not significant (p?=?0.288). Overall, the relationship between the two biomass estimates was strong (R ²?=?0.92, p?<?0.001), suggesting that in certain circumstances, LIDAR may have a role to play in site index estimation and biomass mapping.     

Global Grids from Recursive Diamond Subdivisions of the Surface of an Octahedron or Icosahedron

In recent years a number of methods have been developed for subdividing the surface of the earth to meet the needs of applications in dynamic modeling, survey sampling, and information storage and display. One set of methods uses the surfaces of Platonic solids, or regular polyhedra, as approximations to the surface of the earth. Diamond partitions are similar to recursive subdivisions of the triangular faces of either the octahedron or icosahedron. This method views the surface as either four (octahedron) or ten (icosahedron) tessellated diamonds, where each diamond is composed of two adjacent triangular faces of the figure. The method allows for a recursive partition on each diamond, creating nested sub-dimaonds, that is implementable as a quadtree, including the provision for a Peano or Morton type coding system for addressing the hierarchical pattern of diamonds and their neighborhoods, and for linearizing storage. Furthermore, diamond partitions, in an aperture-4 hierarchy, provide direct access through the addressing system to the aperture-4 hierarchy of hexagons developed on the figure. Diamond partitions provide a nested hierarchy of grid cells for applications that require nesting and diamond cells have radial symmetry for those that require this property. Finally, diamond partitions can be cross-referenced with hierarchical triangle partitions used in other methods.     

Precipitator Design

The various design philosophies and methods used in the engineering design of precipitators for fly ash are reviewed and assessed in light of current stringent environmental standards. The basic precipitator size and electrical parameters are individually analyzed and related to particle and flue gas properties. Actual precipitator design practice is illustrated by data for a wide cross section of power plant installations.     

A Wind Tunnel Study to Design Large,Open-top Chambers for Whole-tree Pollutant Exposure Experiments

A wind tunnel study was conducted to determine the optimal design features of a large, open-top chamber, as needed for pollution exposure studies on mature trees. An optimally-designed, open-top chamber must minimize the incursion of ambient air through its opening and maintain a uniform treatment concentration throughout the chamber. The design features of interest are the diameter and height of the chamber and the deflection angle and opening size of any frustum that may be mounted on top of a model chamber.

Design specifications depend on the turbulence regime about the chamber, which is influenced by the nature of the surrounding vegetation. Consequently, our investigation was performed on scale-model, open-top chambers in a wind tunnel populated with a model coniferous forest. Turbulence measurements demonstrated the similarity between the turbulence regime of the model and a natural forest. A hydrocarbon tracer was injected into the wind tunnel flow to characterize chamber performance.

The main design features of open-top chambers are the velocity of air exiting through the top and the relationship between the length scale of the turbulence and the diameter of the chamber opening. As exit velocities increase, the proportion of eddies with sufficient force to penetrate into the chamber decrease. Therefore, for equal volumetric air flows, smaller opening sizes increase the exit velocities and reduce the number and extent of ambient air incursions. Almost total exclusion of ambient air is achieved as the exit velocity of the air exceeds the magnitude of one standard deviation of the vertical wind velocity measured at the chamber top. The incursion of ambient air is also reduced when the diameter of the chamber opening is smaller than the characteristic length scale of the turbulence, a measure of mean eddy size.

Frusta deflect air flow over the chamber. Three prototypes, with 30?, 45? and 60-degree angles were tested. A 30-degree frustum slightly improves the performance of the chamber and is more effective in preventing ambient air from entraining into the chamber opening than frusta with either a 45? or 60-degree angle. A flatter frustum allows for a smoother transition in the wind velocity streamline and is less apt to cause wake turbulence, as is the case with steeper frusta.

Knowledge of the turbulence characteristics of plant canopies are readily available in the literature and can aid scientists and engineers in designing the optimal chamber and frusta dimensions for their particular application. Therefore, the empirical approach to chamber design can be avoided, and substantial savings can be realized.