Correspondence of biological condition models of California streams at statewide and regional scales

We used boosted regression trees (BRT) to model stream biological condition as measured by benthic macroinvertebrate taxonomic completeness, the ratio of observed to expected (O/E) taxa. Models were developed with and without exclusion of rare taxa at a site. BRT models are robust, requiring few assumptions compared with traditional modeling techniques such as multiple linear regression. The BRT models were constructed to provide baseline support to stressor delineation by identifying natural physiographic and human land use gradients affecting stream biological condition statewide and for eight ecological regions within the state, as part of the development of numerical biological objectives for California’s wadeable streams. Regions were defined on the basis of ecological, hydrologic, and jurisdictional factors and roughly corresponded with ecoregions. Physiographic and land use variables were derived from geographic information system coverages. The model for the entire state (n?=?1,386) identified a composite measure of anthropogenic disturbance (the sum of urban, agricultural, and unmanaged roadside vegetation land cover) within the local watershed as the most important variable, explaining 56 % of the variance in O/E values. Models for individual regions explained between 51 and 84 % of the variance in O/E values. Measures of human disturbance were important in the three coastal regions. In the South Coast and Coastal Chaparral, local watershed measures of urbanization were the most important variables related to biological condition, while in the North Coast the composite measure of human disturbance at the watershed scale was most important. In the two mountain regions, natural gradients were most important, including slope, precipitation, and temperature. The remaining three regions had relatively small sample sizes (n?≤?75 sites) and had models that gave mixed results. Understanding the spatial scale at which land use and land cover affect taxonomic completeness is imperative for sound management. Our results suggest that invertebrate taxonomic completeness is affected by human disturbance at the statewide and regional levels, with some differences among regions in the importance of natural gradients and types of human disturbance. The construction and application of models similar to the ones presented here could be useful in the planning and prioritization of actions for protection and conservation of biodiversity in California streams.     

Emission projections for the U.S. Environmental Protection Agency Section 812 second prospective Clean Air Act cost/benefit analysis

Section 812 of the Clean Air Act Amendments (CAAA) of 1990 requires the U.S. Environmental Protection Agency (EPA) to perform periodic, comprehensive analyses of the total costs and total benefits of programs implemented pursuant to the CAAA. The first prospective analysis was completed in 1999. The second prospective analysis was initiated during 2005. The first step in the second prospective analysis was the development of base and projection year emission estimates that will be used to generate benefit estimates of CAAA programs. This paper describes the analysis, methods, and results of the recently completed emission projections. There are several unique features of this analysis. One is the use of consistent economic assumptions from the Department of Energy's Annual Energy Outlook 2005 (AEO 2005) projections as the basis for estimating 2010 and 2020 emissions for all sectors. Another is the analysis of the different emissions paths for both with and without CAAA scenarios. Other features of this analysis include being the first EPA analysis that uses the 2002 National Emission Inventory files as the basis for making 48-state emission projections, incorporating control factor files from the Regional Planning Organizations (RPOs) that had completed emission projections at the time the analysis was performed, and modeling the emission benefits of the expected adoption of measures to meet the 8-hr ozone National Ambient Air Quality Standards (NAAQS), the Clean Air Visibility Rule, and the PM2.5 NAAQS. This analysis shows that the 1990 CAAA have produced significant reductions in criteria pollutant emissions since 1990 and that these emission reductions are expected to continue through 2020. CAAA provisions have reduced volatile organic compound (VOC) emissions by approximately 7 million t/yr by 2000, and are estimated to produce associated VOC emission reductions of 16.7 million t by 2020. Total oxides of nitrogen (NO(x)) emission reductions attributable to the CAAA are 5, 12, and 17 million t in 2000, 2010, and 2020, respectively. Sulfur dioxide (SO2) emission benefits during the study period are dominated by electricity-generating unit (EGU) SO2 emission reductions. These EGU emission benefits go from 7.5 million t reduced in 2000 to 15 million t reduced in 2020.     

Traffic and meteorological impacts on near-road air quality: summary of methods and trends from the Raleigh Near-Road Study

A growing number of epidemiological studies conducted worldwide suggest an increase in the occurrence of adverse health effects in populations living, working, or going to school near major roadways. A study was designed to assess traffic emissions impacts on air quality and particle toxicity near a heavily traveled highway. In an attempt to describe the complex mixture of pollutants and atmospheric transport mechanisms affecting pollutant dispersion in this near-highway environment, several real-time and time-integrated sampling devices measured air quality concentrations at multiple distances and heights from the road. Pollutants analyzed included U.S. Environmental Protection Agency (EPA)-regulated gases, particulate matter (coarse, fine, and ultrafine), and air toxics. Pollutant measurements were synchronized with real-time traffic and meteorological monitoring devices to provide continuous and integrated assessments of the variation of near-road air pollutant concentrations and particle toxicity with changing traffic and environmental conditions, as well as distance from the road. Measurement results demonstrated the temporal and spatial impact of traffic emissions on near-road air quality. The distribution of mobile source emitted gas and particulate pollutants under all wind and traffic conditions indicated a higher proportion of elevated concentrations near the road, suggesting elevated exposures for populations spending significant amounts of time in this microenvironment. Diurnal variations in pollutant concentrations also demonstrated the impact of traffic activity and meteorology on near-road air quality. Time-resolved measurements of multiple pollutants demonstrated that traffic emissions produced a complex mixture of criteria and air toxic pollutants in this microenvironment. These results provide a foundation for future assessments of these data to identify the relationship of traffic activity and meteorology on air quality concentrations and population exposures.     

Cadmium uptake and translocation in tumbleweed (Salsola kali), a potential Cd-hyperaccumulator desert plant species: ICP/OES and XAS studies

Cadmium is a heavy metal, which, even at low concentrations, can be highly toxic to the growth and development of both plants and animals. Plant species vary extensively in their tolerance to excess cadmium in a growth medium and very few cadmium-tolerant species have been identified. In this study, tumbleweed plants (Salsola kali) grown in an agar-based medium with 20 mgl(-1) of Cd(II) did not show phytotoxicity, and their roots had the most biomass (4.5 mg) (P < 0.05) compared to the control plants (2.7 mg) as well as other treated plants. These plants accumulated 2696, 2075, and 2016 mg Cd kg(-1) of dry roots, stems, and leaves, respectively. The results suggest that there is no restricted cadmium movement in tumbleweed plants. In addition, the amount of Cd found in the dry leaf tissue suggests that tumbleweed could be considered as potential cadmium hyperaccumulating species. X-ray absorption spectroscopy studies demonstrated that in roots, cadmium was bound to oxygen while in stems and leaves, the metal was attached to oxygen and sulfur groups. This might imply that some small organic acids are responsible for Cd transport from roots to stems and leaves. In addition, it might be possible that the plant synthesizes phytochelatins in the stems, later coordinating the absorbed cadmium for transport and storage in cell structures. Thus, it is possible that in the leaves, Cd either exists as a Cd-phytochelatin complex or bound to cell wall structures. Current studies are being performed in order to elucidate the proposed hypothesis.     

The partitioning of alkylphenolic surfactants and polybrominated diphenyl ether flame retardants in activated sludge batch tests

Polybrominated diphenyl ethers and nonylphenol polyethoxylates have been reported to be estrogenic and may enter the aquatic environment through the discharge of treated sewage effluent. Therefore, their fate during wastewater treatment processes is an important factor in determining their environmental impact. Batch tests with activated sludge from a Husmann apparatus were used to determine the effects of physico-chemical properties and sludge characteristics on the partitioning of polybrominated diphenyl ether flame retardants and nonylphenol polyethoxylate surfactants during biological wastewater treatment. Hydrophobic compounds, those with high logK(ow) values, were sorbed more rapidly and to a greater extent to the solid phase than more soluble compounds. For these hydrophobic compounds sorption may become an increasingly important removal mechanism as sludge age and therefore solids content increase. The initial rate of partitioning was greatest for the most hydrophobic compounds but all rates diminished with time as a result of progressive saturation of sorbent binding sites, a reduction of sorbate availability and as a consequence of the system reaching equilibrium. The sorption of polybrominated diphenyl ethers fit Freundlich adsorption isotherms demonstrating generally increasing adsorption capacity and efficiency with increasing hydrophobic nature. A correlation between increasing logK(ow) and increasing organic matter content was also observed for both polybrominated diphenyl ethers and nonylphenol polyethoxylates indicating the organic content of mixed liquor will also be influential in removing compounds during wastewater treatment.     

Soil metal concentrations and productivity of Betula populifolia (gray birch) as measured by field spectrometry and incremental annual growth in an abandoned urban Brownfield in New Jersey

A forested brownfield within Liberty State Park, Jersey City, New Jersey, USA, has soils with arsenic, chromium, lead, zinc and vanadium at concentrations above those considered ambient for the area. Using both satellite imagery and field spectral measurements, this study examines plant productivity at the assemblage and individual specimen level. Longer term growth trends (basal area increase in tree cores) were also studied. Leaf chlorophyll content within the hardwood assemblage showed a threshold model for metal tolerance, decreasing significantly beyond a soil total metal load (TML) of 3.0. Biomass production (calculated with RG - Red/Green Ratio Index) in Betula populifolia (gray birch), the co-dominant tree species, had an inverse relationship with the Zn concentration in leaf tissue during the growing season. Growth of B. populifolia exhibited a significant relationship with TML. Assemblage level NDVI and individual tree NDVI also had significant decreases with increasing TML. Ecosystem function measured as plant production is impaired at a critical soil metal load.     

Lethal critical body residues as measures of Cd, Pb, and Zn bioavailability and toxicity in the earthwormEisenia fetida

Background  

Earthworm heavy metal concentrations (critical body residues, CBRs) may be the most relevant measures of heavy metal bioavailability in soils and may be linkable to toxic effects in order to better assess soil ecotoxicity. However, as earthworms possess physiological mechanisms to secrete and/or sequester absorbed metals as toxicologically inactive forms, total earthworm metal concentrations may not relate well with toxicity.     

Organochlorine contaminants in seven species of Arctic seabirds from northern Baffin Bay

Organochlorine contaminants (OCs) were determined in liver and fat of seven species of seabirds (Alle alle, Uria lomvia, Cepphus grylle, Rissa tridactyla, Pagophila eburnea, Larus hyperboreus, and Fulmaris glacialis) collected in May/June 1998 from the Northwater Polynya in northern Baffin Bay. OC concentrations ranged over an order of magnitude between seabird species and OC groups, with PCBs having the highest concentrations followed by DDT, chlordane, HCH and ClBz. Positive relationships between delta15N (estimator of trophic level) and OC concentrations (lipid basis) were found for all OC groups, showing that trophic position and biomagnification significantly influence OC concentrations in Arctic seabirds. Concentrations of a number of OCs in particular species (e.g., HCH in P. eburnean) were lower than expected based on delta15N and was attributed to biotransformation. P. eburnea and F. glacialis, which scavenge, and R. tridactyla, which migrate from the south, were consistently above the delta15N-OC regression providing evidence that these variables can elevate OC concentrations. Stable isotope measurements in muscle may not be suitable for identifying past scavenging events by seabirds. OC relative proportions were related to trophic position and phylogeny, showing that OC biotransformation varies between seabird groups. Trophic level, migration, scavenging and biotransformation all play important roles in the OCs found in Arctic seabirds.