Emissions Control and Ambient Air Quality at a Secondary Steel Production Facility

Steel production from electric arc furnaces has been continuously rising over the past few years. The trend is expected to continue due to both the anticipated increase in demand for steel, and to the replacement of obsolete open hearth furnaces. In 1972 steel produced in electric arc furnaces, which makes up 25 to 30% of the annual United States steel production, was produced primarily from recycled scrap steel in approximately 300 electric arc furnaces operated by 99 companies at 121 locations.¹ Over half of these furnaces are smaller than 50 tons, and many are located in small bar mills producing a variety of merchant steel products.     

Similarity-based testing for community pattern: the two-way layout with no replication

The large, sparse arrays of species counts arising in both field and experimental community studies do not lend themselves to standard statistical tests based on multivariate normality. Instead, a valid and more revealing approach uses informal display methods, such as clustering or multi-dimensional scaling ordination (MDS), based on a biologically-motivated definition of pairwise similarity of samples in terms of species composition. Formal testing methods are still required, however, to establish that real assemblage differences exist between sites, times, experimental treatments, pollution states, etc. Earlier work has described a range of Manteltype permutation or randomisation procedures, making no distributional assumptions, which are termed ANOSIM tests because of their dependence only on (rank) similarities and the analogy to one and two-way ANOVA. This paper extends these tests to cover an important practical case, previously unconsidered, that of a two-way layoutwithout replication. Such cases arise for single samples (or pseudo-replicates) taken in a baseline monitoring survey of several sites over time, or a mesocosm experiment in which treatments are replicated only once within each experimental block. Significance tests are given for the overall presence of a treatment (or time) effect, based on a measure of concordance between rank similarities of samples within each block (or site); the role of the two factors can be reversed to obtain a test for block effects. As in the analogous univariate ANOVA test, the method relies on absence or relative weakness of treatment x block interactions. Its scope is illustrated with data from two experimental and two field studies, involving meiofaunal communities from soft-sediment and macro-algal habitats. It is seen also to accommodate a modest derree of missing data. Whilst the failure to replicate adequately is not encouraged—a richer inference is available with genuine replication—the paper does provide a limited way forward for hypothesis testing in the absence of replicates.     

Carbonate induced dissolution of uranium containing precipitates under cement leachate conditions

The effects of carbonate on uranium (VI) solubility under aerobic and cementitious conditions have been investigated. The information is of relevance to low level nuclear waste disposal. Aqueous NaOH, KOH, Ca(OH)2 and a cement leachate solution were added to uranyl nitrate solution. Afterwards, increasing amounts of ammonium carbonate were added to re-dissolve the precipitates. The precipitates were characterised by means of X-ray powder diffraction (XRPD) measurements and modelling studies. The model calculations were performed using the MINTEQA2 speciation code, with an expanded database incorporating uranium stability constants taken from the HATCHES database. The measured and predicted amounts of CO3(2-) needed to dissolve the precipitates were compared. The knowledge gained from the 'pure' systems was used to rationalise the precipitation and re-dissolution behaviour observed in the leachate system. The lack of uranium solubility at low carbonate levels brought into question literature formation constants for UO2(OH)3- and UO2(OH)4(2-). An approximate log K value of 26.8 for K2U2O7 formation was estimated from the KOH results at pH 12. Generally, uranium solubilities are expected to be insignificant at low level nuclear waste sites because anaerobic conditions should persist. However, this study has demonstrated that solubility in leachate could rise at high pH and high carbonate levels, if aerobic conditions were to develop. Soluble U(VI) species would be formed. The novel part of the study has been to reproduce the effects and to correlate enhanced solubilities with model predictions. Consequently, the study has re-emphasised the need for appropriate environmental monitoring of such sites.     

Assigning Degrees of Ease or Difficulty for Pet Animal Maintenance: The EMODE System Concept

Pet animal management is subject to varied husbandry practices and the resulting consequences often impact negatively on animal welfare. The perceptions held by someone who proposes to keep an animal regarding the ease or difficulty with which its biological needs can be provided for in captivity are key factors in whether that animal is acquired and how well or poorly it does. We propose a system to ‘score’ animals and assign them to categories indicating the ease or difficulty with which they can be kept as pets in accordance with welfare and public health and safety considerations. The ‘EMODE’ (‘Easy’, ‘Moderate’, ‘Difficult’, ‘Extreme’) system has two fundamental components: animal welfare—which considers the ‘five freedoms’ principles; and public health and safety—which considers management associated with risks from disease or injury to the keeper and to others. EMODE incorporates two tiers of assessment and guidance, and may offer a reasonable guide for the majority of relevant animals. EMODE Tier 1 provides a primary and general assessment of animals by class or group, and EMODE Tier 2 provides a secondary refined assessment of animals by species or breed. EMODE offers a user-friendly and versatile foundation concept for the future development of guidance for the layperson who may be considering acquiring a pet or for certain personnel when considering assigning species to restrictive lists of suitable animals, for example, ‘positive lists’ as used by governments to control animals in trade and keeping.     

Climate change effects on hydroecology of arctic freshwater ecosystems

In general, the arctic freshwater-terrestrial system will warm more rapidly than the global average, particularly during the autumn and winter season. The decline or loss of many cryospheric components and a shift from a nival to an increasingly pluvial system will produce numerous physical effects on freshwater ecosystems. Of particular note will be reductions in the dominance of the spring freshet and changes in the intensity of river-ice breakup. Increased evaporation/evapotranspiration due to longer ice-free seasons, higher air/water temperatures and greater transpiring vegetation along with increase infiltration because of permafrost thaw will decrease surface water levels and coverage. Loss of ice and permafrost, increased water temperatures and vegetation shifts will alter water chemistry, the general result being an increase in lotic and lentic productivity. Changes in ice and water flow/levels will lead to regime-specific increases and decreases in habitat availability/quality across the circumpolar Arctic.     

Modeling the risk of phosphorus runoff following single and split phosphorus fertilizer applications in two contrasting catchments

The potential loss of P in runoff is a function of the combined effects of fertilizer-soil interactions and climatic characteristics. In this study, we applied a Bayesian approach to experimental data to model the annualized long-term risk of P runoff following single and split P fertilizer applications using two example catchments with contrasting rainfall/runoff patterns. Split P fertilizer strategies are commonly used in intensive pasture production in Australia and our results showed that three applications of 13.3 kg P ha(-1) resulted in a greater risk of P runoff compared with a single application of 40 kg P ha(-1) when long-term surface runoff data were incorporated into a Bayesian P risk model. Splitting P fertilizer applications increased the likelihood of a coincidence of fertilizer application and runoff occurring. We found that the overall risk of P runoff is also increased in catchments where the rainfall/runoff pattern is less predictable, compared with catchments where rainfall/runoff is winter dominant. The findings of our study also question the effectiveness of current recommendations to avoid applying fertilizer if runoff is likely to occur in the next few days, as we found that total P concentrations at the half-life were still very high (18.2 and 8.2 mg P L(-1)) following single and split P treatments, respectively. Data from the current study also highlight that omitting P fertilizer on soils that already have adequate soil test P concentrations is an effective method of reducing P loss in surface runoff. If P fertilizer must be applied, we recommend less frequent applications and only during periods of the year when the risk of surface P runoff is low.     

Benthic macrofaunal compositional variations in the northern Bering Sea

Point sampling of soft-sediment macrofauna provided a regional-scale analysis of species composition, diversity, and demographic distributions in the northern Bering Sea (61°0??C65°30??N Lat) in spring 2006. Taxonomic differences distinguished subregions north and south of St. Lawrence Island (P?<?0.1%). High compositional variability occurred within and between sites, with higher variability among northern sites. One to two species dominated most assemblages, with moderately common or rare species. Ampeliscid amphipods characterized the north, and bivalves the south. Bivalves (Macoma calcarea Gmelin, Nuculana radiata Krause, Ennucula tenuis Montagu) were commonly widespread, in varied abundances and sizes. Overall, the extensive soft-sediment habitat supports a varied fauna composition with location, in species dominance, abundance, and size-class. This spatially heterogeneous regional structure is important in assessing ecosystem performance related to secondary production, biogeochemistry, bioturbation, top predator feeding strategy, recruitment, and in measuring change.     

INTERPLAY BETWEEN PARAMETER UNCERTAINTY AND MODEL AGGREGATION ERROR1

ABSTRACTS: Modeling error can be divided into two basic components: use of an incorrect model and input parameter uncertainty. Incorrect model usage can be further subdivided into inappropriate model selection and inherent modeling error due to process aggregation. Total modeling error is a culmination of these various modeling error components, with overall optimization requiring reductions in all. A technique, utilizing Monte Carlo analysis, is employed to investigate the relative importance of input parameter uncertainty versus process aggregation error. An expanded form of the Streeter-Phelps dissolved oxygen equation is used to demonstrate the application of this technique. A variety of scenarios are analyzed to illustrate the relative obfuscation of each modeling error component. Under certain circumstances an aggregated model performs better than a more complex model, which perfectly simulates the real system. Alternately, process aggregation error dominates total modeling error for other situations. The ability to differentiate modeling error impact is a function of the desired or imposed model performance level (accuracy tolerance).     

Effects of physical disturbance on nematode communities in sand and mud: a microcosm experiment

A microcosm experiment was carried out to evaluate the effects of continuous and spasmodic physical disturbance of differing frequency on the structure of nematode communities of intertidal sand and mud. There was a marked, characteristic change in abundance and diversity for both sediment types. In the sand microcosms, the majority of univariate measures of community structure, including species diversity, were lowest in the sediments subjected to a high frequency of disturbance. For the mud microcosms, most univariate measures reached their highest values in the treatments with an intermediate frequency of disturbance and were lower in treatments subjected to both higher and lower frequencies. Multivariate ordinations for both nematode assemblages showed a clear separation of undisturbed controls and disturbed treatments, but only for the muddy sediment was there a graded change in community composition with increasing frequency of disturbance. These results confirmed our a priori expectation that nematode assemblages from mobile sandy sediments would be more resilient to physical disturbance than those from sheltered muds, and these observations are considered in the context of Connell's intermediate disturbance hypothesis. Received: 7 May 1997 / Accepted: 10 October 1997