A field study of triclosan loss rates in river water (Cibolo Creek, TX)

Triclosan (TCS) is an anti-microbial agent used in down-the-drain consumer products. Following sewage treatment some of the triclosan will enter receiving waters. This study was designed to determine the die-away rate of triclosan released into a river as part of the sewage treatment plant effluent matrix. The study was conducted in Cibolo Creek, a moderate sized stream (discharge approximately 0.1 m(3)s(-1)) located in South Central Texas. Triclosan was analyzed from samples collected upstream of the sewage treatment plant, the sewage treatment plant effluent, and the river downstream from the effluent discharge. The first-order loss rate of parent triclosan from the water column was calculated from measured data (0.06 h(-1)) and this rate corresponded to a 76% reduction in triclosan over an 8 km river reach below the discharge. Mathematical modeling indicated that sorption and settling accounted for approximately 19% of total triclosan loss over 8 km. When removing sorption and settling, the remaining amount of triclosan had an estimated first-order loss rate of 0.25 h(-1). This loss rate was presumably due to other processes such as biodegradation and photolysis. These data show that loss of parent triclosan from the water column is rapid. Additional data are needed to fully document loss mechanisms.     

Using GIS for siting artificial reefs—Data issues, problems and solutions: ‘Real World’ to ‘Real World’

As GIS becomes an increasingly more ‘user-friendly’ tool, and more people recognize the benefits of the technology in their work environment, inevitably greater use will be made of it for a wide range of applications. The ease with which a GIS can now be used often overshadows the complexity underlying this technology and the potential difficulties that can (and do) arise when this is not fully understood. In practice, there are two routes open to the application of GIS technology for environmental studies. The first is to commission new data for the research. The second is to make use of existing data sets. Data are at the heart of any GIS application. A detailed knowledge about the data sources, the method of collection, capture, scale and sampling strategy, especially if the data are to be used in any analysis, modelling or simulation studies, is fundamental to any application. Unfortunately, information about data (metadata) is seldom available, especially for archival or legacy data sets. Furthermore, although it is now relatively easy to acquire digital data, to input, store, manipulate and display this data, and to output the results of any GIS analysis in the practical sense, little consideration is given to the problems associated with data quality and how this will ultimately affect present and future analyses and use of the output for planning and decision-making. The need to raise awareness about data quality for applications is set in the context of the development of an environmental database for the Moray Firth. Northeast Scotland, and more specifically the use of selected data sets from the database to aid in the proposed siting of an artificial reef. Using this example, this contribution explores the problems associated with the use of both existing analog and digital data sets as the basis for environmental applications, the problems of data acquisition, data quality, data standards, error and how these can affect the operational use of the data in GIS analyses. The solution to such problems appears to lie with improved error assessment and reporting. The outcome of this contribution is an attempt to offer guidance and solutions to researchers and applications specialists undertaking similar studies, by suggesting to what extent studies, such as the artificial reef siting, can safely make use of existing data sets without risking the problems associated with judgements based on inadequate information, and generated or inherent error.     

Incorporating uncertainty in a chemical leaching assessment

Pesticide leaching models are being used to assist in the regulation and management of pesticides by indicating their potential for leaching to groundwater. Uncertainty in model input data is not, regrettably, included in most pesticide leaching assessments. In the work described here, we use logarithmic transformations of the attenuation factor (AF), a simple process-based index model, to represent uncertainty in a pesticide leaching assessment. Characterization of a wide range of pesticides as `leachers' or `non-leachers' for a specific Hawaii hydrogeological setting is facilitated by comparing the log-transformed AF, designated AFR, for each chemical with two reference chemicals for which leaching behavior in Hawaii is known. Defining a mean and uncertainty interval for the AFR index of each chemical being ranked provides a practical method of incorporating data uncertainty into a regulatory protocol.     

Tree species for recovering nitrogen from dairy-farm effluent in New Zealand

Land treatment of dairy-farm effluent is being widely adopted as an alternative to disposal into surface waters in New Zealand. This study investigated water balances and associated N leaching from short-rotation forest (SRF) species irrigated with dairy-farm effluent. Single trees were grown in lysimeters filled with Manawatu fine sandy loam (mixed mesic Dystric Eutrochrept). Dairy-farm effluent was applied during two irrigation periods at 21.5 mm wk(-1) with a total loading equivalent to 870 kg N ha(-1) occurring over 17 mo. Following tree harvest in April 1997, measurements continued until August 1997 to monitor tree reestablishment. Cumulative N leached did not differ between lysimeters in which evergreen Sydney blue gum (Eucalyptus saligna Sm.) and shining gum [Eucalyptus nitens (H. Deane & Maiden) Maiden] and deciduous kinu-yanagi (Salix kinuyanagi Kimura) were grown. Leachate N concentrations of all treatments were on average higher than the New Zealand drinking water standard of 11.3 mg N L(-1). The E. nitens and S. kinuyanagi treatments leached 33 and 35 kg N ha(-1) yr(-1) in 1996 following application of 236 kg N ha(-1) during the first irrigation season. Leaf area was strongly correlated to evapotranspiration, drainage volume, and nitrogen leached. The majority of leaching in the tree treatments occurred after harvest. Reducing the leaching in the regrowth phase may be achieved through timing harvest in the spring when growth rates are higher and leaching potential is lower. Based on N uptake rates observed in this study and average pond discharge, a plantation of 5.4 ha would be required for N recovery on a typical dairy farm in New Zealand.     

A comparison of taxon co-occurrence patterns for macro- and microorganisms

We examine co-occurrence patterns of microorganisms to evaluate community assembly "rules". We use methods previously applied to macroorganisms, both to evaluate their applicability to microorganisms and to allow comparison of co-occurrence patterns observed in microorganisms to those found in macroorganisms. We use a null model analysis of 124 incidence matrices from microbial communities, including bacteria, archaea, fungi, and algae, and we compare these results to previously published findings from a meta-analysis of almost 100 macroorganism data sets. We show that assemblages of microorganisms demonstrate nonrandom patterns of co-occurrence that are broadly similar to those found in assemblages of macroorganisms. These results suggest that some taxon co-occurrence patterns may be general characteristics of communities of organisms from all domains of life. We also find that co-occurrence in microbial communities does not vary among taxonomic groups or habitat types. However, we find that the degree of co-occurrence does vary among studies that use different methods to survey microbial communities. Finally, we discuss the potential effects of the undersampling of microbial communities on our results, as well as processes that may contribute to nonrandom patterns of co-occurrence in both macrobial and microbial communities such as competition, habitat filtering, historical effects, and neutral processes.     

Transport of brine shrimps via the digestive system of migratory waders: dispersal probabilities depend on diet and season

Waterbirds are known to disperse invertebrate propagules that survive gut passage, but there is very little information about how the probability of dispersal changes at different times of the annual cycle when birds move in different directions, or how it is affected by changes in diet. We studied internal transport of brine shrimp Artemia cysts by migratory waders in the Odiel saltworks in south-west Spain. Viable cysts of parthenogenetic Artemia were abundant in the faeces and regurgitated pellets of redshank Tringa totanus, pellets of spotted redshank T. erythropus, and faeces of black-tailed godwit Limosa limosa during spring and/or autumn migrations in 2001–2002, but were not recorded during winter. Godwits did not produce pellets, and spotted redshank faeces were not sampled. Significant correlations between the number of cysts in a pellet or faecal sample and the proportion of that sample constituted by Artemia adults suggested that most cysts were ingested while in the ovisacs of gravid females. The proportion of cysts destroyed during digestion increased when accompanied by harder food items or grit, and when fewer cysts were ingested. The median number of intact cysts was higher in redshank faeces than in their pellets, but cysts extracted from pellets were more likely to hatch. A higher proportion of redshank pellets contained Artemia cysts in spring than in autumn, but more redshank migrated through the area in autumn. Significantly fewer cysts were recorded in redshank pellets in winter than in spring or autumn. Our results confirm that there is potential for long-distance dispersal of Artemia cysts via waders during both northwards (spring) and southwards (autumn) migrations.     

Clean Air Corridors: A Geographic and

Meteorological factors, pollutant emissions, and geographic regions related to transport of low optical extinction coefficient air to Grand Canyon National Park were examined. Back trajectories were generated by two models, the Atmospheric Transport and Dispersion Model (ATAD) and an approach using the Nested Grid Model output for a Lagrangian particle transport model (NGM/ CAPITA). Meteorological information along the trajectories was analyzed for its relationship to visibility at the Grand Canyon. Case studies considered days with anomalously clean air from the southwest and dirty air from the northwest. Clean air was most frequently from the north and northwest, rarely from the south. Low emissions, high ventilation and washout by precipitation was associated with clean air. All clean days with transport from the Los Angeles area had upper-level low pressure over the region with high ventilation and usually abundant precipitation. The dirtiest days with transport from the northwest were affected by forest fires.     

Use of Tracer Gas for Direct Calibration of Emission-Factor Measurements in a Traffic Tunnel

ABSTRACT

Pollutant measurements in traffic tunnels have been used to estimate motor-vehicle emissions for several decades. The objective in this type of study is to use the traffic tunnel as a tool for characterizing motor vehicles rather than seeking a tunnel design with acceptably low pollutant concentrations. In the past, very simple aerodynamic models have been used to relate measured concentrations to vehicle emissions. Typically, it is assumed that velocities and concentrations are uniform across the tunnel cross section. In the present work, a vehicle emitting a known amount of sulfur hexafluoride (SF₆) was driven repeatedly through a 730-m-long traffic tunnel in Vancouver, Canada. Comparing the measured SF₆ concentrations to the known emission rates, it is possible to directly assess the accuracy of the simple tunnel aerodynamic models typically used to interpret tunnel data. Correction factors derived from this procedure were then applied to measurements of carbon monoxide and other pollutants to obtain gram-per-kilometer emission factors for vehicles. Although the specific correction factors measured here are valid only for the tunnel tested, the magnitude of the factors (up to two or more) suggests that the phenomena observed here should be considered when interpreting data from other tunnels.     

A Comparative Study of Environmental Tobacco Smoke Particulate Mass Measurements in an Environmental Chamber

Particulate mass concentration measurements have been made on environmental tobacco smoke (ETS) for the purpose of assessing the relative accuracy of several measurement procedures. ETS over a range of concentrations was generated in an environmental chamber by three methods. Mass concentration was measured by a gravimetric/spectrophotometric collection procedure, piezoelectric particle mass monitors, two nephelometry-based mass monitors, and a particle counting and sizing system. Two-hour average mass concentrations were determined by each method for concentrations ranging from very low levels up to those achieved by smoking one entire cigarette in the chamber. Statistical comparisons were made among procedures employing the gravimetric filter measurement as the basis for comparison. One nephelometry-based procedure gave significantly higher and the other significantly lower values than the filter determination. In one case, a correction for the difference between the particle mass density of the calibrating aerosol and that of ETS brought the nephelometry-based procedure into reasonable agreement with the filter measurement, while for the other, the correction did not resolve the discrepancy between methods. Statistically significant differences between the responses of two supposedly identical piezoelectric mass monitors were found, as was some slight dependence of the nephelometry- based procedures on method of ETS generation. In summary, the results indicate that significant errors can be expected if the instruments studied are used “off the shelf,” even for ETS generated under controlled laboratory conditions. Caution should be employed in field measurements where numerous sources and types of particulate matter can be encountered.