Assessing potential bioavailability of metals in sediments: A proposed approach

Due to anthropogenic inputs, elevated concentrations of metals frequently occur in aquatic sediments. In order to make defensible estimates of the potential risk of metals in sediments and/or develop sediment quality criteria for metals, it is essential to identify that fraction of the total metal in the sediments that is bioavailable. Studies with a variety of benthic invertebrates indicate that interstitial (pore) water concentrations of metals correspond very well with the bioavailability of metals in test sediments. Many factors may influence pore water concentrations of metals; however, in anaerobic sediments a key phase controlling partitioning of several cationic metals (cadmium, nickel, lead, zinc, copper) into pore water is acid volatile sulfide (AVS). In this paper, we present an overview of the technical basis for predicting bioavailability of cationic metals to benthic organisms based on pore water metal concentrations and metal-AVS relationships. Included are discussions of the advantages and limitations of metal bioavailability predictions based on these parameters, relative both to site-specific assessments and the development of sediment quality criteria.     

Using ecological criteria to evaluate wilderness planning options in Idaho

Legally designated wilderness areas are acknowledged to be an important element in strategies to conserve biological diversity in United States. However, because of the restrictions on consumptive uses in wilderness, their establishment is normally contentious. Criteria for establishment have typically been associated with opportunity and aesthetic and experiential values. Biological data have not normally played a major role in guiding wilderness establishment. We present four wilderness allocation options for those public lands considered suitable for wilderness designation in Idaho. These options cover the span of choices presently available to wilderness planners in the state and range from not establishing any new wilderness areas to the inclusion of all suitable lands in wilderness. All options are evaluated using spatial biological data from the National Biological Survey's Gap Analysis Project. A conservation strategy that would protect a minimum of 10% of the area occupied by each of 113 native vegetation types and at a minimum 10% of the distribution of each of 368 vertebrate species was evaluated for each option. Only the inclusion of all suitable lands in wilderness, creating a system of 5.1 million ha came close to achieving these goals, protecting 65% of the vegetation types and 56% of the vertebrate species. We feel this approach, which allows planners to evaluate the ecological merits of proposed widerness units along with other values, can provide a means to resolve the impasse over additional wilderness designation in Idaho.     

Sources of funds for developing country petroleum development

The Third World debt crisis has drastically altered the options open to Third World countries to fund petroleum development. Restricted access to international capital markets means that developing countries are having to reconsider alternative financial options to achieve a satisfactory rate of petroleum development. Of these, only foreign direct investmentis capable of compensating for the loss of more traditional sources of funds. To this end, developing countries are revising and harmonizing prior restrictive direct investment rules and tax codes, with recent financial innovations further underwriting the process.     

A statistical approach to field measurements of the chemical evolution of cold (<0°C) snow cover

Two statistical methods for the analysis of data on the evolution of the chemical composition of cold snow (<0°C) in the field (Lac Laflamme, Quebec) were compared. The methods used on the data were regression analysis (One sample per sampling date over a long cold period) and ANOVA (replicate samples on a restricted number of sampling dates over shorter periods). The relative power of the tests to determine the detectable amplitude of chemical changes was derived from the theoretical power of the tests under comparable conditions of sampling (number of observations) and from the estimated error variances of the measured data.The results of the study on the evolution of sulfates (SO₄) concentrations in discretely identified snow strate clearly showed that for six of the eight strata, significant losses of SO₄ occurred in snow during cold periods. The relative amplitude of the significant losses varied between 1% per day and 4% per day depending on the initial concentrations in the snow and the prevailing meteorological conditions.The analysis of the data also demonstrated that for the same number of samples, the regression analysis is more efficient in detecting the chemical changes in snow than the alternative ANOVA method. The use of this information to plan sampling programs of cold snow under both field and laboratory conditions is discussed.     

Evaluation of treatment techniques for increasing the uptake of metal ions from solution by nonliving seaweed algal biomass

The effects of several different treatments on subsequent uptake of several metal ions from solution by six strains of seaweed algae and a sea plant were investigated. Samples of Gracilaria conferta, Eisenia bicyclis, Ulva lactuca, Sargassum fluitans, Cladophora prolitera, Padina pavonica, and Zostera marina were treated with one or more of the following: 1 M HCl, 1 M HNO₃, 0.1 M NaOH, 1 M NaOH, acetone, and 60°C water at times from 15 to 60 min and temperatures of 25 and 60°C. Results obtained demonstrate that a treatment time of 15 or 30 min is usually sufficient to produce maximum subsequent metal uptake. Temperature of treatment had little effect.The percentages of Pb, Cu, Zn, Cd, Cr, Mn, Ni, Co, TI, Hg, Au, and Ag subsequently removed from standard metal solutions at a pH of 2–6 by each treated biomass were compared with the percent removal by untreated biomass under the same conditions. All treatments increased the ability of the biomass types studied to bind metals relative to untreated biomass. In addition, pH binding dependence was altered to some extent with a greater degree of binding observed at low pHs by biomass treated with acid. For certain strains of seaweed algae, 0.1 M NaOH treatment produced subsequent uptake of Pb, Cu, Zn, and Cd at levels reaching 100% of initial metal available. Both acidic and basic treatment increased the uptake of Au, Ag, and Hg by four strains of seaweed to nearly 100%.     

Scaling the quality of teammates' mental models: equifinality and normative comparisons

We tested the impact of teammates' team and task mental model sharedness on team processes and performance using 70 undergraduate teams that completed a series of missions on a PC‐based flight simulator. Moreover, we considered how the quality of mental models might moderate such relationships. Team processes were found to partially mediate the relationship between task mental model sharedness and team performance. Although team mental model sharedness failed to exhibit a significant linear relationship with team processes or performance, it did evidence a multiplicative relationship as moderated by the quality of those models. Team processes and performance were better among teams sharing higher‐quality team mental models than among teams evidencing less sharedness or who had lower‐quality models. Again, team processes partially mediated these relationships. Results are discussed in terms of the equifinality of mental model quality and applications to various team environments. Copyright © 2005 John Wiley & Sons, Ltd.     

EFFECTS OF PRESCRIPTIVE RIPARIAN BUFFERS ON LANDSCAPE CHARACTERISTICS IN NORTHERN MINNESOTA,USA1

ABSTRACT: Forest buffers adjacent to water bodies are widely prescribed in forest management to protect ecological functions of riparian systems. To date, buffers have been applied on the landscape uniformly without quantifying their effectiveness or the effects they have on landscape characteristics. Our objective was to quantify landscape characteristics (amount of edge and interior forest) when buffers were applied to water bodies in a 100 by 100 km area of northern Minnesota. We used a Landsat classified image in a geographic information system platform to apply two buffer widths ?28.5 m and 57 m — to water bodies, including nonforested wetlands, intermittent or perennial streams, and lakes. A total of 107,141 ha (18.3 percent) of the forest area was adjacent to and within 28.5 m of these water bodies, while 201,457 ha of forest was within 57 m, representing 34.4 percent of the total forest area. Imposing a 28.5 m buffer on water bodies increased the amount of edge and interior forest in the study area. When water bodies were buffered with a 57 m forest strip, we found a slight increase in forest edge from the current condition, and this buffer width resulted in the largest amount of interior forest. Interior forest increased with the 57 m buffer due to the density of water bodies in this region; adjacent water bodies coalesced when buffers were applied and formed isolated forest islands that contained forest interior habitat. Instead of wholesale application of set width riparian buffers, we suggest that ecological conditions of riparian areas be evaluated on a site level and that areas that currently provide important riparian conditions be maintained on the landscape with appropriate management practices.     

The Impact of Computers Upon Air Pollution Research

The electronic computer has had a profound effect upon air pollution research activities. This paper discusses some of the ways in which Public Health Service scientists routinely make use of the computer. It is used as a data processor to handle the large volumes of data resulting from continuous air monitoring devices. More importantly, it is used to perform the very complex computations involved in various statistical analyses and mathematical model building. In future years computers may be used on a real-time basis to control the sources which emit pollutants to the atmosphere.     

Reproducibility of the HI-VOL Sampling Method Under Field Conditions

Pairs of standard NASN Hi-Vol suspended particulate samplers were operated biweekly at 25 stations (22 urban, 3 nonurban) from August to December 1969 to determine the comparability of paired samples collected under field conditions. The average of each pair of concentration values is taken as the best estimate of the true value; half the difference between each pair of sample values represents the deviation of the pair from that true value. A cumulative distribution of the individual percent deviations from the corresponding true values shows that half the measurements differ from their true value by less than ±4.5%. 90% of the measurements differ from the true value by less than ± 14%.