Evaluation of an explicit NOx chemistry method in AERMOD

An explicit NO_x chemistry method has been implemented in AERMOD version 15181, ADMSM. The scheme has been evaluated by comparison with the methodologies currently recommended by the U.S. EPA for Tier 3 NO₂ calculations, that is, OLM and PVMRM2. Four data sets have been used for NO₂ chemistry method evaluation. Overall, ADMSM-modeled NO₂ concentrations show the most consistency with the AERMOD calculations of NO_x and the highest Index of Agreement; they are also on average lower than those of both OLM and PVMRM2. OLM shows little consistency with modeled NO_x concentrations and markedly overpredicts NO₂. PVMRM2 shows performance closer to that of ADMSM than OLM; however, its behavior is inconsistent with modeled NO_x in some cases and it has less good statistics for NO₂. The trend in model performance can be explained by examining the features particular to each chemistry method: OLM can be considered as a screening model as it calculates the upper bound of conversion from NO to NO₂ possible with the background O₃ concentration; PVMRM2 includes a much-improved estimate of in-plume O₃ but is otherwise similar to OLM, assuming instantaneous reaction of NO with O₃; and ADMSM allows for the rate of this reaction and also the photolysis of NO₂. Evaluation with additional data sets is needed to further clarify the relative performance of ADMSM and PVMRM2.

Implications: Extensive evaluation of the current AERMOD Tier 3 chemistry methods OLM and PVMRM2, alongside a new scheme that explicitly calculates the oxidation of NO by O₃ and the reverse photolytic reaction, shows that OLM consistently overpredicts NO₂ concentrations. PVMRM2 performs well in general, but there are some cases where this method overpredicts NO₂. The new explicit NO_x chemistry scheme, ADMSM, predicts NO₂ concentrations that are more consistent with both the modeled NO_x concentrations and the observations.     

Persistent organochlorines in the serum of the non-occupationally exposed New Zealand population

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and organochlorine pesticides were measured in the serum of a sample of the New Zealand population aged 15 years and older. This was the first study to obtain representative measures of PCDDs, PCDFs and PCBs in the adult population of an entire country. Serum samples were obtained in 1996-1997. Potentially occupationally exposed individuals were excluded. Serum samples were pooled according to stratification criteria for area of residence, ethnicity, age, and sex. Of the 80 possible strata, sufficient serum for chemical analysis was available for 60, to which 1,834 individual samples contributed. For the PCDDs and PCDFs, most 2,3,7,8-chlorinated congeners were measured in all strata, with a mean toxic equivalents concentration across all strata of 12.8 ng TEQ kg(-1) lipid. Seven PCB congeners were frequently measured, including the coplanar congeners #126 and #169, quantified in all strata. Of the pesticides and their metabolites, only beta-HCH, dieldrin and pp'-DDE were consistently detected across strata. There was a general trend of increasing concentration with age. There were no consistent differences between the sexes, or between people of Maori (the indigenous people of New Zealand) and non-Maori ethnicity. Concentrations of PCDDs and PCDFs tended to increase in a North-South direction, possibly reflecting greater levels of industrialization and population concentration, and concentrations of the pesticide products were highest in the South, possibly reflecting historical use patterns. Results were consistent with a recent study of concentrations of these compounds in the milk of first-time mothers.     

OXYGEN DEMAND IN ICE COVERED LAKES AS IT PERTAINS TO WINTER AERATION1

ABSTRACT: Winterkill, the death of fish under ice due to oxygen deficiency, threatens hundreds of shallow lakes in the upper Midwest of the United States every winter. For decades, attempts have been made to prevent winterkill, usually through aeration, with mixed results. In large part, the failure of strategies to prevent winterkill can be linked to a lack of understanding of winter limnology and in particular, of oxygen dynamics under ice. Most winterkill lakes behave as closed systems with regard to oxygen. Consequently, the oxygen content of an ice and snow covered lake is essentially a function of the amount of initial storage and the rate of depletion. Should the stored oxygen be insufficient to prevent near anoxia before melting of the ice cover occurs, winterkill will result. Most oxygen consumption in ice covered lakes is due to bacterial respiration and chemical oxidation at the sediment/water interface, the remainder occurring in the water column. Oxygen consumption (and thus depletion) is a function of the velocity and oxygen concentration of the near sediment water. This is due to the fact that oxygen transport to the sediment is mediated by a diffusive boundary layer adjacent to the sediment surface. Winter oxygen depletion rates decrease when the oxygen concentration of the overlying water falls below about 3 mg/l. Aeration techniques which increase the oxygen concentration and velocity of the near-sediment water also increase the oxygen consumption (depletion) rate.     

Drivers influencing adaptive management: a retrospective evaluation of water quality decisions in South East Queensland (Australia)

This article analyzes interviews with natural resource managers in South East Queensland (SEQ), Australia. The objectives of the research are (i) to apply and test deductive/inductive text analysis methods for constructing a conceptual model of water quality decision-making in SEQ, (ii) to understand the role of information in the decision-making process, and (iii) to understand how to improve adaptive management in SEQ. Our methodology provided the means to quickly and objectively explore interview data and also reduce potential subjective bias normally associated with deductive text analysis methods. At a more practical level, our methodology indicates potential intervention points if one is to influence the decision-making process in the region. Results indicate that relevant information is often ignored in SEQ, with significant consequences for adaptive management. Contextual factors (political, social, and environmental) together with effective communication or lobbying strategies often prevent evidence-based decisions. We propose that in addition to generating information to support decisions, adaptive management also requires an appraisal of the true character of the decision-making process, which includes how stakeholders interact, what information is relevant and salient to management, and how the available information should be communicated to stakeholders and decision-making bodies.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-014-0537-4) contains supplementary material, which is available to authorized users.     

Technical Manual onSingle Retort Underfeed Stokers

Most of the recent work on the effects of cement-kiln dust has been confined to Germany and results differ considerably. There appears to be little doubt that naturally deposited dust from certain cement plants is responsible for leaf injury to deciduous and coniferous species and occasionally for death of the latter. Injury results from the combination of a relatively thick crust deposit and the toxicity of alkaline solutions formed when dusts are deposited in the presence of free moisture. The results of several hand-dusted field experiments, however, are not so conclusive; dusts are reported as either harmful, harmless, or even indirectly beneficial. In the present laboratory investigation, the comparison of CO₂ exchange in the leaf between dusted and nondusted leaves, as well as occurrence of obvious tissue damage, were used as the criteria of dust effects in short term experiments. The results demonstrated that the finer particles of certain cement-kiln dusts collected from electrostatic precipitators do interfere with CO₂ exchange and in some cases cause considerable leaf injury. The results further suggest that calcium content alone may not be the only indicator of whether a dust might be injurious, and that much more needs to be known about the effects of the interaction of chemical composition, particle size, and deposition rate.     

An ecosystem approach to population management of ungulates

Harvest objectives for wild ungulates have traditionally been based on population models that do not consider ecosystem effects of ungulate herbivory, nor interactions between native and domestic ungulate species. There is a need for ecosystem models to allow wildlife managers to evaluate potential ecosystem effects of management scenarios. The utility of the SAVANNA simulation model for estimating elk population objectives within an ecosystem context was demonstrated for North Park, Colorado, USA. Effects of different elk population levels were evaluated for range condition, elk and cattle forage, elk and cattle condition, forage and condition of mule deer and moose, plant production, and plant community composition. Analyses were based on 30-year simulation runs using variable, historical weather. Another set of analyses utilized stochastic weather patterns. For management scenarios using the historical climate pattern, increasing elk populations caused biomass reductions of palatable plant species, particularly on areas of high winter density, where mean leaf biomass of palatable shrubs declined from 26.97 g/m2 at 0 elk to 20.82 g/m2 at 4000 elk (3.73 elk/km2), a 23% decline. At population levels of 5000 elk (4.68 elk/km2) or greater, elk body condition declined sharply following a severe winter. The availability of palatable browse on critical winter range was likely the limiting factor. However, when random climate patterns were simulated for the same scenarios, the threshold level for density-dependent effects varied with climate, ranging from 2000 to 10,000 elk. We suggest that elk population levels from 4000 to 5000 animals represent a conservative population objective for the North Park elk herd. Also, increasing elk population levels appears to intensify intraspecific competition among elk, far more than interspecific competition with cattle. Resolution of elk-cattle conflicts is likely to be facilitated by managing elk distribution, rather than overall elk population levels.     

A method to compare groundwater cleanup technologies

DuPont has developed a method to compare, on a consistent economic basis, in situ remediation technologies. The methodology employs a template site with a perchloroethylene plume 1000 ft long by 400 ft wide, and incorporates various aquifer thicknesses and depths. Variables considered in the methodology include duration of the remediation; estimated engineering and flow/transport modeling costs; equipment costs; and operation, maintenance, and monitoring costs. In this article, substrate-enhanced anaerobic bioremediation, intrinsic bioremediation, in situ permeable reactive barriers, and pump-and-treat systems are evalutated. Cost metrics include present cost, cost per pound of contaminant removed, and cost per 1000 gals treated, using a discounted cash-flow analysis. Costs of the remedial alternatives increase starting from intrinsic bioremediation, to substrate-enhanced anaerobic bioremediation, to a biological substrate-enhanced anaerobic barrier, to in situ permeable reactive barriers, to pump-and-treat systems with air stripping and carbon adsorption.     

Environmental evaluation of subdivision site developments

An environmental evaluation was performed at 16 subdivision sites within four communities in east-central Michigan. The primary objective was to evaluate the fit between environmental ordinances and the physical/environmental conditions to which they were applied. An environmental response index was developed with indicators to assess water, soil, slope, development density, roads, vegetation, and ecology. Water-related indicators achieved the highest scores, while soil-related indicators scored the poorest, with generally poor performance across all indicators. The poor performance indicates there are problems in the ability of environmental ordinances developed at broader jurisdictional scales (e.g., the state) to address the existing environmental conditions at smaller geographic scales (subdivisions within communities). Two key problems include the lack of scientific specificity in the broader state-level ordinances and the lack of local expertise and/or resources to monitor the environment.