Influence of atmospheric dispersion and new particle formation events on ambient particle number concentration in Rochester, United States, and Toronto, Canada

Continuous measurements of particle number concentrations were performed in Rochester, NY, and Toronto, Ontario, Canada during the 2003 calendar year. Strong seasonal dependency in particle number concentration was observed at two sites. The average number concentration of ambient particles was 9670 +/- 6960 cm(-3) in Rochester, whereas in Toronto the average number of particles was 28,010 +/- 13,350 cm(-3). The particle number concentrations were higher in winter months than in summer months by a factor of 1.5 in Rochester and 1.6 in Toronto. In general, there were also distinct diurnal variations of aerosol number concentration. The highest weekdays/weekends ratio of number concentration was typically observed during the rush-hour period in winter months with a ratio of 2.1 in Rochester and 2.0 in Toronto. The correlation in the total particle number concentrations between the two urban sites was stronger in winter because of the common urban traffic patterns, but weaker in summer because of local sulfur dioxide (SO2)-related particle formation events in Rochester in the summer. Strong morning particle formation events were frequently observed during colder winter months. Good correlations between particle number and carbon monoxide (CO) as well as temperature suggested that motorvehicle emissions lead to the formation of new particles as the exhaust mixes with the cold air. Regional nucleation and growth events frequently occurred in April. Local SO2-related particle formation events most frequently occurred in August. SO2 and UV-B were highly correlated with particle concentration, suggesting a high association of photochemical processes with these local events. A high directionality in a northerly direction was observed for particle number and SO2, indicating the influence of point sources located north of Rochester.     

How Run-of-River Operation Affects Hydropower Generation and Value

Regulated rivers in the United States are required to support human water uses while preserving aquatic ecosystems. However, the effectiveness of hydropower license requirements nationwide has not been demonstrated. One requirement that has become more common is “run-of-river” (ROR) operation, which restores a natural flow regime. It is widely believed that ROR requirements (1) are mandated to protect aquatic biota, (2) decrease hydropower generation per unit flow, and (3) decrease energy revenue. We tested these three assumptions by reviewing hydropower projects with license-mandated changes from peaking to ROR operation. We found that ROR operation was often prescribed in states with strong water-quality certification requirements and migratory fish species. Although benefits to aquatic resources were frequently cited, changes were often motivated by other considerations. After controlling for climate, the overall change in annual generation efficiency across projects because of the change in operation was not significant. However, significant decreases were detected at one quarter of individual hydropower projects. As expected, we observed a decrease in flow during peak demand at 7 of 10 projects. At the remaining projects, diurnal fluctuations actually increased because of operation of upstream storage projects. The economic implications of these results, including both producer costs and ecologic benefits, are discussed. We conclude that regional-scale studies of hydropower regulation, such as this one, are long overdue. Public dissemination of flow data, license provisions, and monitoring data by way of on-line access would facilitate regional policy analysis while increasing regulatory transparency and providing feedback to decision makers.     

Development of an Ecologic Marine Classification in the New Zealand Region

We describe here the development of an ecosystem classification designed to underpin the conservation management of marine environments in the New Zealand region. The classification was defined using multivariate classification using explicit environmental layers chosen for their role in driving spatial variation in biologic patterns: depth, mean annual solar radiation, winter sea surface temperature, annual amplitude of sea surface temperature, spatial gradient of sea surface temperature, summer sea surface temperature anomaly, mean wave-induced orbital velocity at the seabed, tidal current velocity, and seabed slope. All variables were derived as gridded data layers at a resolution of 1 km. Variables were selected by assessing their degree of correlation with biologic distributions using separate data sets for demersal fish, benthic invertebrates, and chlorophyll-a. We developed a tuning procedure based on the Mantel test to refine the classification's discrimination of variation in biologic character. This was achieved by increasing the weighting of variables that play a dominant role and/or by transforming variables where this increased their correlation with biologic differences. We assessed the classification's ability to discriminate biologic variation using analysis of similarity. This indicated that the discrimination of biologic differences generally increased with increasing classification detail and varied for different taxonomic groups. Advantages of using a numeric approach compared with geographic-based (regionalisation) approaches include better representation of spatial patterns of variation and the ability to apply the classification at widely varying levels of detail. We expect this classification to provide a useful framework for a range of management applications, including providing frameworks for environmental monitoring and reporting and identifying representative areas for conservation.     

Best management practices for nutrient and sediment retention in urban stormwater runoff

Stormwater management infrastructure is utilized in urban areas to alleviate flooding caused by decreased landscape permeability from increased impervious surface cover (ISC) construction. In this study, we examined two types of stormwater detention basins, SDB-BMPs (stormwater detention basin-best management practice), and SDB-FCs (stormwater detention basin-flood control). Both are constructed to retain peak stormwater flows for flood mitigation. However, the SDB-BMPs are also designed using basin topography and wetland vegetation to provide water quality improvement (nutrient and sediment removal and retention). The objective of this study was to compare SDB (both SDB-BMP and SDB-FC) surface soil P concentrations, P saturation, and Fe chemistry with natural riparian wetlands (RWs), using sites in Fairfax County, Virginia as a model system. The SDB-BMPs had significantly greater surface soil total P (P(t)) concentrations than the RWs and SDB-FCs (831.9 +/- 32.5 kg ha(-1), 643.3 +/- 19.1 kg ha(-1), and 652.1 +/- 18.8 kg ha(-1), respectively). The soil P sorption capacities of SDB-BMPs were similar to the RWs, and were greater than those of SDB-FCs, appearing to result in greater soil P removal and retention in SDB-BMPs compared with SDB-FCs. Increased Fe concentrations and relatively greater amounts of more crystalline forms of Fe in SDB-BMP soils suggested increased sediment deposition compared with RW and SDB-FC soils. Data suggest that SDB nutrient and sediment retention is facilitated in SDB-BMPs. When stormwater management is necessary, use of SDB-BMPs instead of SDB-FCs could foster more responsible urban development and be an appropriate mitigation action for receiving aquatic ecosystems.     

Soil microbial community response to hexavalent chromium in planted and unplanted soil

Theories suggest that rapid microbial growth rates lead to quicker development of metal resistance. We tested these theories by adding hexavalent chromium [Cr(VI)] to soil, sowing Indian mustard (Brassica juncea), and comparing rhizosphere and bulk soil microbial community responses. Four weeks after the initial Cr(VI) application we measured Cr concentration, microbial biomass by fumigation extraction and soil extract ATP, tolerance to Cr and growth rates with tritiated thymidine incorporation, and performed community substrate use analysis with BIOLOG GN plates. Exchangeable Cr(VI) levels were very low, and therefore we assumed the Cr(VI) impact was transient. Microbial biomass was reduced by Cr(VI) addition. Microbial tolerance to Cr(VI) tended to be higher in the Cr-treated rhizosphere soil relative to the non-treated systems, while microorganisms in the Cr-treated bulk soil were less sensitive to Cr(VI) than microorganisms in the non-treated bulk soil. Microbial diversity as measured by population evenness increased with Cr(VI) addition based on a Gini coefficient derived from BIOLOG substrate use patterns. Principal component analysis revealed separation between Cr(VI) treatments, and between rhizosphere and bulk soil treatments. We hypothesize that because of Cr(VI) addition there was indirect selection for fast-growing organisms, alleviation of competition among microbial communities, and increase in Cr tolerance in the rhizosphere due to the faster turnover rates in that environment.     

The thief process for mercury removal from flue gas

The Thief Process is a cost-effective variation to activated carbon injection (ACI) for removal of mercury from flue gas. In this scheme, partially combusted coal from the furnace of a pulverized coal power generation plant is extracted by a lance and then re-injected into the ductwork downstream of the air preheater. Recent results on a 500-lb/h pilot-scale combustion facility show similar removals of mercury for both the Thief Process and ACI. The tests conducted to date at laboratory, bench, and pilot-scales demonstrate that the Thief sorbents exhibit capacities for mercury from flue gas streams that are comparable to those exhibited by commercially available activated carbons. A patent for the process was issued in February 2003. The Thief sorbents are cheaper than commercially-available activated carbons; exhibit excellent capacities for mercury; and the overall process holds great potential for reducing the cost of mercury removal from flue gas. The Thief Process was licensed to Mobotec USA, Inc. in May of 2005.     

Demography of Two Mexican Spotted Owl Populations

Abstract: The Mexican Spotted Owl ( Strix occidentalis lucida ) is a threatened subspecies of the southwestern United States and northern Mexico. Although threatened, little is known about its population status. We studied the demography of the Mexican Spotted Owl in one study area in Arizona and one in New Mexico from 1991 to 1997. We estimated annual survival rates (φ), fecundity rates (   b ), and abundance (   N ) to test the hypothesis that population trends were stationary. Although annual fecundity rates (   b ^ = 0.494 for Arizona and 0.380 for New Mexico) and annual juvenile survival rates ( φ^ = 0.179 for Arizona and 0.109 for New Mexico) differed in magnitude between the study areas, they exhibited similar temporal patterns. Annual survival for territorial owls varied randomly in Arizona but declined linearly in New Mexico. Mean annual survival for territorial owls was 0.814 in Arizona and 0.832 for owls ≥3 years old and 0.644 for owls 1–2 years old in New Mexico. Based on survival and fecundity estimates, the annual rates of change (λ^) indicated that both populations were declining at ≥10% a year. These estimates were corroborated by observed declines in abundance. Some regional factor may have been affecting fecundity, whereas a combination of factors may have been affecting survival. Two possible reasons for the population declines are declines in habitat quality and regional trends in climate.     

EQUILIBRIUM EVAPORATION AND POSITWE EVAPORATION-SURFACE TEMPERATURE RELATIONSHIPS ACROSS A GRASSLAND1

Sensible (H) and latent (LE) heat fluxes, soil moisture (SM) and surface temperatures (T_s) were analyzed from seven sites at FIFE to evaluate relationships among the spatial variability of evaporative fraction, EF, SM, and the diurnal surface temperature range (T_dr). Intersite correlations between EF and T_dr were significantly negative for regional average soil moisture SM_r < 20 percent, insignificant for 20 < SM_r < 27 percent, and slightly positive for SM_r > 27 percent. Statistical analysis of the pooled correlation coefficient between EF and T_dr for SM_r < 20 percent indicates that it is less than zero at a very high level of significance, while the pooled correlation coefficient for regional SM_r > 27 percent is greater than zero at the 10 percent level. The positive EF:T_dr correlations are attributed to increased surface vapor pressure at warmer sites under nearly potential conditions. These results suggest that to characterize the spatial variability of the energy budget partitioning, a variable representing the thermal response of the site should be included. An important application of these findings relates to modeling the subgrid variability of a region by subdividing the region into a few classes within which surface variables and parameters are assumed invariant. The thermal response of the surface should be included as a variable in defining these classes.     

Resuspension of contaminated field and formulated reference sediments Part I: Evaluation of metal release under controlled laboratory conditions

In aquatic systems where metal contaminated sediments are present, the potential exists for metals to be released to the water column when sediment resuspension occurs. The release and partitioning behavior of sediment-bound heavy metals is not well understood during resuspension events. In this study, the release of Cd, Cu, Hg, Ni, Pb and Zn from sediments during resuspension was evaluated using reference sediments with known physical and chemical properties. Sediment treatments with varying quantities of acid volatile sulfide (AVS), total organic carbon (TOC), and different grain size distributions were resuspended under controlled conditions to evaluate their respective effects on dissolved metal concentrations. AVS had the greatest effect on limiting release of dissolved metals, followed by grain size and TOC. Predictions of dissolved concentrations of Cd, Ni, Pb and Zn were developed based on the formulated sediment Σ_metal/AVS ratios with Σ_metal being the total sediment metal concentration. Predicted values were compared to measured dissolved metal concentrations in contaminated field sediments resuspended under identical operating conditions. Metal concentrations released from the field sediments were low overall, in most cases lower than predicted values, reflecting the importance of other binding phases. Overall, results indicate that for sulfidic sediments, low levels of the study metals are released to the dissolved phase during short-term resuspension.