Influence of drought and municipal sewage effluents on the baseflow water chemistry of an upper piedmont river

The Reedy River in South Carolina is affected by the urban area of Greenville, the third most populous city in the state, and by the effluents from two large-scale municipal wastewater treatment plants (WWTPs) located on the river. Riverine water chemistry was characterized using grab samples collected annually under spring season baseflow conditions. During the 4-year time period associated with this study, climatic variations included two severe drought spring seasons (2001 and 2002), one above-normal precipitation spring season (2003), and one below-normal precipitation spring season (2004). The influence of drought and human activities on the baseflow chemistry of the river was evaluated by comparing concentrations of dissolved anions, total metals, and other important water chemistry parameters for these different years. Concentrations of copper and zinc, common non-point source contaminants related to urban activities, were not substantially elevated in the river within the urban area under baseflow conditions when compared with headwater and tributary samples. In contrast, nitrate concentrations increased from 1.2–1.6 mg/l up to 2.6–2.9 mg/l through the urban stream reach. Concentrations of other major anions (e.g., sulfate, nitrate) also increased along the reach, suggesting that the river receives continuous inputs of these species from within the urban area. The highest concentrations of major cations and anions typically were observed immediately downstream from the two WWTP effluent discharge locations. Attenuation of nitrate downstream from the WWTPs did not always track chloride changes, suggesting that nitrate concentrations were being controlled by biochemical processes in addition to physical processes. The relative trends in decreasing nitrate concentrations with downstream distance appeared to depend on drought versus non-drought conditions, with biological processes presumably serving as a more important control during non-drought spring seasons.     

The Genetic Diversity of Native, Stocked, and Hybrid Populations of Brook Trout in the Southern Appalachians

Using mitochondrial DNA (mtDNA) restriction analysis and starch-gel electrophoresis of the CK-A2 locus product, we examined genetic variation in 311 brook trout (Salvelinus fontinalis) from 11 native, 5 hatchery-derived, and 8 hybrid populations in the southern Appalachian Mountains. Native southern Appalachian fish were genetically distinct from hatchery-derived fish. Southern and hatchery-derived fish were reliably distinguished based on three mtDNA restriction sites. Native southern haplotypes differed from hatchery-derived haplotypes by an average of 0.84%. Northern hatchery-derived haplotypes varied little in mtDNA compared to native southern haplotypes. Introgression of mtDNA haplotypes and the CK-A2 locus varied among populations, and introgression of allozyme and mtDNA markers was positively correlated. Continued introductions of nonnative strains of brook trout in the southern Appalachians could simplify the genetic structure of native brook trout populations and eliminate unique genotypes.     

Comparison of capillary pressure relationships of organic liquid-water systems containing an organic acid or base

The presence of surface-active solutes such as organic acids and bases may have a profound influence on the transport of organic liquid contaminants through their impact on the constitutive relationship of capillary pressure vs. saturation. This relationship is a function of the interfacial tension and wettability of the system, which, in turn, depend on the pH and the concentration of organic acids and bases that are present. This study examines the impact of pH and the concentration on the interfacial tension, contact angle, and capillary pressure of systems consisting of tetrachloroethylene, water, and quartz containing either octanoic acid or dodecylamine. In general, the ionic form of the solute tended to remain in the aqueous phase and reduced the capillary pressure through its impact on the interfacial tension and contact angle; on the other hand, the neutral form of the solute partitioned into the organic liquid phase and had a lesser impact on the capillary pressure for the same total mass of solute. A comparison of these data with data generated in previous research in similar systems where o-xylene was the organic liquid showed that the trends are analogous. Thus, the behavior of these two solvent systems seems to be driven primarily by the aqueous phase speciation of the solute, and the differences between the capillary pressure relationships for the two systems could be attributed to the pure system interfacial tension.     

Role of plants, mycorrhizae and phytochelators in heavy metal contaminated land remediation

Phytoremediation is a site remediation strategy, which employs plants to remove non-volatile and immisible soil contents. This sustainable and inexpensive process is emerging as a viable alternative to traditional contaminated land remediation methods. To enhance phytoremediation as a viable strategy, fast growing plants with high metal uptake ability and rapid biomass gain are needed. This paper provides a brief review of studies in the area of phytoaccumulation, most of which have been carried out in Europe and the USA. Particular attention is given to the role of phytochelators in making the heavy metals bio-available to the plant and their symbionts in enhancing the uptake of bio-available heavy metals.     

Assessing model structure uncertainty through an analysis of system feedback and Bayesian networks.

Ecological predictions and management strategies are sensitive to variability in model parameters as well as uncertainty in model structure. Systematic analysis of the effect of alternative model structures, however, is often beyond the resources typically available to ecologists, ecological risk practitioners, and natural resource managers. Many of these practitioners are also using Bayesian belief networks based on expert opinion to fill gaps in empirical information. The practical application of this approach can be limited by the need to populate large conditional probability tables and the complexity associated with ecological feedback cycles. In this paper, we describe a modeling approach that helps solve these problems by embedding a qualitative analysis of sign directed graphs into the probabilistic framework of a Bayesian belief network. Our approach incorporates the effects of feedback on the model's response to a sustained change in one or more of its parameters, provides an efficient means to explore the effect of alternative model structures, mitigates the cognitive bias in expert opinion, and is amenable to stakeholder input. We demonstrate our approach by examining two published case studies: a host-parasitoid community centered on a nonnative, agricultural pest of citrus cultivars and the response of an experimental lake mesocosm to nutrient input. Observations drawn from these case studies are used to diagnose alternative model structures and to predict the system's response following management intervention.     

Estimating the Effect of Being Indoors on Total Personal Exposure to Outdoor Air Pollution

A personal air quality model (PAQM) has been developed to estimate the effect of being indoors on total personal exposure to outdoor-generated air pollution. Designed to improve air toxics risk assessment, PAQM accounts for individual hourly activity patterns, indoor-outdoor differences, physical exercise level, and geographic location for up to 56 different population groups. Unique hourly activity profiles are specified for each population group; group members are assigned each hour to one of up to 10 different indoor and outdoor microenvironments. To illustrate PAQM use, we apply it to two example cases: a long-term example representative of situations where pollutant health impact is related to integrated exposure (as in the case of potentially carcinogenic air toxics) and a short-term example representative of situations where health impact is related to acute exposure to peak concentrations (as with ozone).

Case study results illustrate that personal exposure, and thus health risk, attributable to outdoor-generated air pollution is sensitive to indoor-outdoor differences and population mobility. Where health impact is related to long-term integrated exposure (e.g., air toxics), exposure and subsequent risk are likely to be lower than that estimated by previous modeling techniques which do not account for such effects.     

Sperm precedence, mating interval, and a novel mechanism of paternity bias in a beetle (Tenebrio molitor L.)

When females mate with more than one male, the ensuing sperm competition leads to the evolution of male mechanisms that skew paternity. Males of the yellow mealworm beetle (Tenebrio molitor) transfer a spermatophore to females during copulation, but sperm release and storage occur later. We investigated how the interval between two matings with different males affects sperm precedence by varying the interval between the copulations so that the second mating was either: (1) before sperm release from the first spermatophore (<5 min); (2) after sperm release but before spermatophore ejection (15–20 min); (3) after spermatophore ejection but before sperm storage (4 h), or (4) after complete sperm storage (24 h). We collected offspring over a period of 2 weeks and determined paternity by protein electrophoresis. There was second-male sperm precedence in all treatments, but when the interval was <5 min, the second male usually (86% of cases) had complete sperm precedence (i.e., P ₂=1). Investigations into the mechanism of second-male sperm precedence during <5-min mating intervals indicate that sperm release from the first spermatophore is inhibited, a phenomenon which has not been previously documented. Received: 31 January 2000 / Revised: 9 June 2000 / Accepted: 26 August 2000     

PCBs in air, soil and milk in industrialized and urban areas of KwaZulu-Natal, South Africa

Information regarding polychlorinated biphenyls (PCBs) in environmental media in Africa is limited. This paper presents results of a monitoring program conducted in KwaZulu-Natal Province, South Africa designed to characterize levels, trends and sources of airborne PCBs. Particulate and vapor samples were sampled over the 2004-2005 period at three sites. The total PCB concentration averaged 128 ± 47 pg m⁻³, and levels were highest in winter. Tri- through hexa-congeners predominated, and the vapor fraction was predominant. Several tetra- through hexa-chlorinated congeners had levels comparable to those at urban sites in the northern hemisphere, but hepta- through deca-congeners resembled levels at background sites. PCB source areas, deduced using spatial and temporal patterns, compositional information and trajectory analyses, likely included local, regional and global sources. Soils at three rural sites showed high PCB concentrations, and milk from a local dairy showed PCB concentrations comparable to USA levels in year 2000.     

A longitudinal study of the links between Local Air Quality Management and Local Transport Planning policy processes in England

The second round of the Local Transport Plan (LTP2) process in England presents unique challenges and opportunities for integrating Local Air Quality Management (LAQM) within current transport planning policy. Using content analysis of LTP2 documents from nine English authorities, and results from a questionnaire survey of local government officers undertaken in late 2007, this paper charts the changes in the integration of air quality management within the transport planning process since 1997. While substantial improvements in policy integration were observed within the selected case studies, the paper demonstrates that such improvements are often constrained by institutional complexities that create implementation gaps between national objectives and local decision-making outcomes.     

Predicting community sensitivity to ozone, using Ellenberg Indicator values

This paper develops a regression-based model for predicting changes in biomass of individual species exposed to ozone (RS(p)), based on their Ellenberg Indicator values. The equation (RS(p)=1.805-0.118Light-0.135 square root Salinity) underpredicts observed sensitivity but has the advantage of widespread applicability to almost 3000 European species. The model was applied to grassland communities to develop two further predictive tools. The first tool, percentage change in biomass (ORI%) was tested on data from a field-based ozone exposure experiment and predicted a 27% decrease in biomass over 5 years compared with an observed decrease of 23%. The second tool, an index of community sensitivity to ozone (CORI), was applied to 48 grassland communities and suggests that community sensitivity to ozone is primarily species-driven. A repeat-sampling routine showed that nine species were the minimum requirement to estimate CORI within 5%.