Identification of road salt contamination using multiple regression and GIS

A multiple regression model of atmospheric deposition of salt, combined with geographic information systems (GIS) data on four classes of roads, is used to predict sodium concentrations in 162 randomly chosen streams in Massachusetts. All four classes of roads, as well as atmospheric deposition, were found to be highly significant in a model that explains 68% of the observed variation in sodium concentration. The highest salt loading rates are associated with interstate and major state roads with an estimated 22,500 and 17,700 kg of salt per kilometer, respectively. Our mass balance calculations indicate road salt is the major source of salt to the streams in Massachusetts. We examined some of the common statistical problems associated with the use of multiple regression for this type of analysis. Our confidence in the accuracy of the loading rates estimated above are limited by the collinear nature of environmental data and uncertainties related to model specification. Our results suggest multiple regression techniques can lead to overconfidence in the accuracy of the estimated loading rates and thus should not be used as the basis for policy unless the model is validated.     

Bioconcentration of polycyclic aromatic hydrocarbons by the freshwater oligochaete Lumbriculus variegatus

Tissue residues of the PAHs, anthracene, fluorene, fluoranthene and pyrene were determined in Lumbriculus variegatus at four time intervals during both a 96-h exposure period to monitor uptake, and a 96-h clean water period to assess depuration. Mean BCFs were 2390, 1210, 452 and 1920 for fluoranthene, anthracene, fluorene and pyrene, respectively. BCFs were positively correlated with the octanol/water partition coefficient values of the four PAHs. Depuration occurred most rapidly for fluorene, followed by anthracene and fluoranthene. No apparent depuration of pyrene was observed during the 96-h depuration period. Because of rapid depuration of some PAHs, it appears that the 24 h clean water gut clearance period recommended in conjunction with sediment bioaccumulation tests with L. variegatus has potential to result in an under-estimation of bioaccumulation of some chemicals.     

Effects of pulp mill chlorate on Baltic Sea algae

The long-term effects of pulp mill chlorate on different algal species of the Baltic Sea were studied in land-based model ecosystems simulating the littoral zone. Brown algae (Phaeophyta) exhibited an extraordinarily high sensitivity to chlorate and pulp mill effluents containing chlorate. All brown algal species ceased growth or showed major signs of toxicity at all concentrations tested, down to microgram per litre levels. EC50 levels for growth of Fucus vesiculosus were about 80-100 microg ClO3- litre(-1). Blue-green algae (Cyanophyta) were not deleteriously affected nor were green algae (Chlorophyta). The perennial and annual species of red algae (Rhodophyta) were also unaffected by the effluents. Diatoms did not show any sensitivity and phytoplankton (fresh- and brackish water) were particularly insensitive. A phanerogam, Zostera marina was also unaffected by the treatments.     

REGIONAL CHEMISTRY OF LAKES IN MASSACHUSETTS 1

ABSTRACT: We surveyed over 2000 lakes in the State of Massachusetts (1983–1984) to examine the spatial variations in their acid-base chemistry. Our survey differed from previous surveys by including small lakes and nonpristine urban lakes. For samples collected in October 1983 and 1984, the median acid neutralizing capacity (ANC) was 184 μeq L^?1 and 5.9 percent were acidic (ANC≤O). Small lakes (<4 ha) were more likely to be acidic than large lakes. Generally, sulfate was the dominant acidifying agent, although organic anions were dominant in some of the lakes in the Cape Cod Region. The ionic composition of the lakes showed strong regional patterns which appear to be related to geology and human population density. An analysis of variance of ANC shows the six regional categories in the state explain 51 percent of the variance, while a combined general linear model of lake drainage type, color, elevation, size, silica, and hydrogen ion deposition could explain only 4.9 percent of the variation in ANC. Calcium rich, high ionic strength lakes were present in the marble bedrock in the west, and relatively dilute lakes dominated by sodium and chloride were found near the coast. Chloride concentrations were also related to population density, suggesting road salt as a likely contributing source.     

Electrokinetic ion transport through unsaturated soil: 2. Application to a heterogeneous field site

Results of a field demonstration of electrokinetic transport of acetate through an unsaturated heterogeneous soil are compared to numerical modeling predictions. The numerical model was based on the groundwater flow and transport codes MODFLOW and MT3D modified to account for electrically induced ion transport. The 6-month field demonstration was conducted in an unsaturated layered soil profile where the soil moisture content ranged from 4% to 28% (m3 m(-3)). Specially designed ceramic-cased electrodes maintained a steady-state moisture content and electric potential field between the electrodes during the field demonstration. Acetate, a byproduct of acetic acid neutralization of the cathode electrolysis reaction, was transported from the cathode to the anode by electromigration. Field demonstration results indicated preferential transport of acetate through soil layers exhibiting higher moisture content/electrical conductivity. These field transport results agree with theoretical predictions that electromigration velocity is proportional to a power function of the effective moisture content. A numerical model using a homogeneous moisture content/electrical conductivity domain did not adequately predict the acetate field results. Numerical model predictions using a three-layer electrical conductivity/moisture content profile agreed qualitatively with the observed acetate distribution. These results suggest that field heterogeneities must be incorporated into electrokinetic models to predict ion transport at the field-scale.     

Integrating Human Impacts and Ecological Integrity into a Risk-Based Protocol for Conservation Planning

Conservation planning aims to protect biodiversity by sustainng the natural physical, chemical, and biological processes within representative ecosystems. Often data to measure these components are inadequate or unavailable. The impact of human activities on ecosystem processes complicates integrity assessments and might alter ecosystem organization at multiple spatial scales. Freshwater conservation targets, such as populations and communities, are influenced by both intrinsic aquatic properties and the surrounding landscape, and locally collected data might not accurately reflect potential impacts. We suggest that changes in five major biotic drivers—energy sources, physical habitat, flow regime, water quality, and biotic interactions—might be used as surrogates to inform conservation planners of the ecological integrity of freshwater ecosystems. Threats to freshwater systems might be evaluated based on their impact to these drivers to provide an overview of potential risk to conservation targets. We developed a risk-based protocol, the Ecological Risk Index (ERI), to identify watersheds with least/most risk to conservation targets. Our protocol combines risk-based components, specifically the frequency and severity of human-induced stressors, with biotic drivers and mappable land- and water-use data to provide a summary of relative risk to watersheds. We illustrate application of our protocol with a case study of the upper Tennessee River basin, USA. Differences in risk patterns among the major drainages in the basin reflect dominant land uses, such as mining and agriculture. A principal components analysis showed that localized, moderately severe threats accounted for most of the threat composition differences among our watersheds. We also found that the relative importance of threats is sensitive to the spatial grain of the analysis. Our case study demonstrates that the ERI is useful for evaluating the frequency and severity of ecosystemwide risk, which can inform local and regional conservation planning.