Refined tunable methodology for characterization of contaminant-particle relationships in surface water

To understand contaminant transport in aquatic systems, it is essential to define the physical characteristics of the primary particulate carriers. The distribution of organic pollutants with particle-size class and particle morphology in a freshwater embayment (Hamilton Harbor, western Lake Ontario) was studied using a sequence of novel sample preparation and characterization techniques. Water samples (24 L) were fractionated according to particle-size distribution using differential cascade sedimentation and centrifugation methods. These size fractions were subsequently subjected to a physicochemical characterization using scanning transmission electron microscopy and energy-dispersive spectroscopy to identify flocs and individual colloidal particles in the size range of 1 nm to 1 mm in diameter. Analytical chemical analyses were performed to identify organic contaminants in extracts prepared from particle-size classes, including polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). The contaminant distribution trends were very similar for all compound classes studied; contaminants were primarily associated with fractions containing particles less than 2 mum in diameter. Morphological characterization of these fractions showed the majority of the particulates to be humic fractals. The results of this study show that contaminants in aquatic systems can be preferentially associated with specific types of particle carriers, the characteristics of which can be clearly defined in terms of size and morphology.     

The Influence of Urban Density and Drainage Infrastructure on the Concentrations and Loads of Pollutants in Small Streams

Effective water quality management of streams in urbanized basins requires identification of the elements of urbanization that contribute most to pollutant concentrations and loads. Drainage connection (the proportion of impervious area directly connected to streams by pipes or lined drains) is proposed as a variable explaining variance in the generally weak relationships between pollutant concentrations and imperviousness. Fifteen small streams draining independent subbasins east of Melbourne, Australia, were sampled for a suite of water quality variables. Geometric mean concentrations of all variables were calculated separately for baseflow and storm events, and these, together with estimates of runoff derived from a rainfall-runoff model, were used to estimate mean annual loads. Patterns of concentrations among the streams were assessed against patterns of imperviousness, drainage connection, unsealed (unpaved) road density, elevation, longitude (all of which were intercorrelated), septic tank density, and basin area. Baseflow and storm event concentrations of dissolved organic carbon (DOC), filterable reactive phosphorus (FRP), total phosphorus (TP) and ammonium, along with electrical conductivity (EC), all increased with imperviousness and its correlates. Hierarchical partitioning showed that DOC, EC, FRP, and storm event TP were independently correlated with drainage connection more strongly than could be explained by chance. Neither pH nor total suspended solids concentrations were strongly correlated with any basin variable. Oxidized and total nitrogen concentrations were most strongly explained by septic tank density. Loads of all variables were strongly correlated with imperviousness and connection. Priority should be given to low-impact urban design, which primarily involves reducing drainage connection, to minimize urbanization-related pollutant impacts on streams.     

Competition for territories in red-winged blackbirds: Is resource-holding potential realized?

Summary In resource-defence mating systems we intutively expect that the most competitive males should win the best resources so that, in territorial species, male quality and territory quality will be highly correlated. In the polygyny threshold model (PTM) of mate choice this expectation has become an assumption. We performed a removal experiment using red-winged blackbirds to test the validity of this assumption. On the basis of two morphological and two behavioral indices of competitive ability we found only weak correlation between male competitive ability and territory quality. Factors potentially contributing to this result include habitat quality perception, site dominance, and site fidelity. However, both our experimental design and measurement of male competitive ability may have caused us to underestimate the real correlation between male quality and territory quality. Nevertheless, our results suggest that male quality is not perfectly correlated with territory quality as is assumed in the PTM. Therefore, male quality and territory quality should be treated independently when modelling mate choice in this and other territorial species.     

Mass balance modelling of contaminants in river basins: a flexible matrix approach

A novel and flexible approach is described for simulating the behaviour of chemicals in river basins. A number (n) of river reaches are defined and their connectivity is described by entries in an n x n matrix. Changes in segmentation can be readily accommodated by altering the matrix entries, without the need for model revision. Two models are described. The simpler QMX-R model only considers advection and an overall loss due to the combined processes of volatilization, net transfer to sediment and degradation. The rate constant for the overall loss is derived from fugacity calculations for a single segment system. The more rigorous QMX-F model performs fugacity calculations for each segment and explicitly includes the processes of advection, evaporation, water-sediment exchange and degradation in both water and sediment. In this way chemical exposure in all compartments (including equilibrium concentrations in biota) can be estimated. Both models are designed to serve as intermediate-complexity exposure assessment tools for river basins with relatively low data requirements. By considering the spatially explicit nature of emission sources and the changes in concentration which occur with transport in the channel system, the approach offers significant advantages over simple one-segment simulations while being more readily applicable than more sophisticated, highly segmented, GIS-based models.     

Evaluation of Ground‐Water and Surface‐Water Exchanges Using Streamflow Difference Analyses1

Abstract: In the karstic lower Flint River Basin, limestone fracturing, jointing, and subsequent dissolution have resulted in the development of extensive secondary permeability and created a system of major conduits that facilitate the exchange of water between the Upper Floridan aquifer and Flint River. Historical streamflow data from U.S. Geological Survey gaging stations located in Albany and Newton, Georgia, were used to quantify ground‐water and surface‐water exchanges within a 55.3 km section of the Flint River. Using data from 2001, we compared estimates of ground‐water flux using a time adjustment method to a water balance equation and found that these independent approaches yielded similar results. The associated error was relatively large during high streamflow when unsteady conditions prevail, but much lower during droughts. Flow reversals were identified by negative streamflow differences and verified with in situ data from temperature sensors placed inside large spring conduits. Long‐term (13 years) analysis showed negative streamflow differentials (i.e., a losing stream condition) coincided with high river stages and indicated that streamflow intrusion into the aquifer could potentially exceed 150 m³/s. Although frequent negative flow differentials were evident, the Flint River was typically a gaining stream and showed a large net increase in flow between the two gages when examined over the period 1989‐2003. Ground‐water contributions to this stream section averaged 2‐42 m³/s with a mean of 13 m³/s. The highest rate of ground‐water discharge to the Flint River occurred during the spring when regional ground‐water levels peaked following heavy winter and spring rains and corresponding rates of evapotranspiration were low. During periods of extreme drought, ground‐water contributions to the Flint River declined.     

Monitoring Long-term Trends in Sulfate and Ammonium in US Precipitation: Results from the National Atmospheric Deposition Program/National Trends Network

Data from the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) indicate significant changes have occurred in precipitation chemistry and the chemical climate in the United States (US). A Seasonal Kendall Trend (SKT) analysis shows statistically significant increases in precipitation ammonium concentrations at 64% of 159 continental US NADP/NTN sites evaluated from Winter 1985 to Fall 2004 (Dec. 1984 – Nov. 2004). Sulfate decreases were widespread, with an SKT analysis indicating statistically significant decreases at 89% of sites evaluated. Ratios of chemical equivalent concentrations of ammonium to sulfate in precipitation have risen to the extent that ammonium now exceeds sulfate over more than half of the continental U.S. on a precipitation-weighted-mean annual basis. These trends in the concentrations of ammonium, sulfate, and other species have been accompanied by significant decreases in the frequency of acidic precipitation (pH < 5.0) in the last decade.     

Off-Target Herbicide Deposition Associated with Treating Individual Trees

There are a wide variety of different herbicide treatment methods used to remove single trees. Each method (cut-stump, basal, foliar) has a unique amount of off-target disturbance that should be considered in selecting a treatment for use in management. We quantified the amount of off-target deposition that resulted from four conventional herbicide application methods: 1) basal, 2) cut-stump, 3) high-volume, hydraulic foliar, and 4) low-volume, backpack foliar. Basal and cut-stump herbicide treatments deposited up to 200 and 4000 times more herbicide (a.i. per unit area) at groundline than the low-volume and high-volume foliar treatments, respectively. On a per tree basis, basal and cut-stump treatments deposited nearly six times more total herbicide than high-volume foliar, and 68 times more than low-volume foliar. All of the herbicide deposited off-target landed within 0.6 m of the basal and cut-stump treatments, 3.7 m with the low-volume foliar, and 7.3 m with high-volume foliar methods. Off-target herbicide deposition resulted in affected areas with killed or damaged vegetation ranging in size from 0.36 m² (cut stump) to 7.08 m² (high-volume foliar). Deposition amounts and affected areas were greater with larger trees, compared to smaller ones. We observed that 48% of the total amount of herbicide applied per plot was deposited off-target with cut-stump treatment, compared to only 4% to 11% for the other treatments. We suspect this difference is due to applicator error with the cut-stump treatment, likely related to the type of spray device used to apply the treatment.     

Determinants of a Quality Wild Turkey Hunting Season

According to the National Wild Turkey Federation, there has been a 450% increase in the number of licensed wild turkey hunters since 1973. Unfortunately, there is a paucity of research articles focusing specifically on turkey hunting. Most human dimensions of wildlife research have focused on either deer or waterfowl hunting. In this study, dimensions of hunting quality, days afield, and harvest were examined among a sample of 739 Virginia fall turkey hunters. Quality of a hunting season, rather than a specific hunt, was examined. Principal components analysis (PCA) revealed five domains of attributes of a high-quality turkey-hunting season: wildlife interaction, education, being away, social interaction, and hunting skills. The domains of hunting quality revealed by the PCA are similar to domains found previously for spring turkey hunters as well as other types of hunters. Also examined were hunter perceptions of overall hunting quality, the number of days spent hunting turkeys during the fall season, and harvest success. For comparative purposes and agency needs, hunters were segmented into three categories based on days spent hunting: low frequency (1 to 2 days), medium frequency (3 to 4 days), and high frequency (≥5 days). The influence of these variables to respondents’ perceptions of overall quality was examined using a series of regression models. Variables found to be significant predictors of quality were wildlife interaction and harvest success. Hunters who killed a turkey reported a significantly higher quality season than those who did not kill a turkey.     

Surface runoff and transport of sulfonamide antibiotics and tracers on manured grassland

Despite their common use in animal production the environmental fate of the veterinary sulfonamide antibiotics after excretion is only poorly understood. We performed irrigation experiments to investigate the transport of these substances with surface runoff on grassland. Liquid manure from pigs treated with sulfadimidine was spiked with sulfadiazine, sulfathiazole, the herbicide atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine), and the conservative tracer bromide and spread onto eight plots. Four plots received the same amounts of the spiked substances in aqueous solution (controls). Apart from the application matrix we varied the time between application and irrigation. Manure increased the runoff volume up to six times compared with the controls. It seemed that manure enhanced the runoff by sealing the soil surface. On manured plots the relative antibiotic concentrations in runoff were higher than on the controls, reaching an average of 0.3% (sulfadiazine), 0.8% (sulfathiazole), and 1.4% (sulfadimidine) of the input concentrations after a 1-d contact time. The corresponding values on the controls were 0.16% for sulfadiazine and 0.08% for sulfathiazole. After 3 d, the maximum values on the manured plots were even higher, whereas they had fallen below the limit of quantification on the controls. As a consequence, the sulfonamide losses were 10 to 40 times larger on the manured plots. The relative mobility of the sulfonamides on the control plots followed the trend expected from their chromatographic separation but the opposite was found on the manured plots. Hence it is important to consider explicitly the physical and chemical effects of manure when assessing the environmental fate of sulfonamides.