Land management impacts on dairy-derived dissolved organic carbon in ground water

Dairy operations have the potential to elevate dissolved organic carbon (DOC) levels in ground water, where it may interact with organic and inorganic contaminants, fuel denitrification, and may present problems for drinking water treatment. Total and percent bioavailable DOC and total and carbon-specific trihalomethane (THM) formation potential (TTHMFP and STHMFP, respectively) were determined for shallow ground water samples from beneath a dairy farm in the San Joaquin Valley, California. Sixteen wells influenced by specific land management areas were sampled over 3 yr. Measured DOC concentrations were significantly elevated over the background as measured at an upgradient monitoring well, ranging from 13 to 55 mg L(-1) in wells downgradient from wastewater ponds, 8 to 30 mg L(-1) in corral wells, 5 to 12 mg L(-1) in tile drains, and 4 to 15 mg L(-1) in wells associated with manured fields. These DOC concentrations were at the upper range or greatly exceeded concentrations in most surface water bodies used as drinking water sources in California. DOC concentrations in individual wells varied by up to a factor of two over the duration of this study, indicating a dynamic system of sources and degradation. DOC bioavailability over 21 d ranged from 3 to 10%, comparable to surface water systems and demonstrating the potential for dairy-derived DOC to influence dissolved oxygen concentrations (nearly all wells were hypoxic to anoxic) and denitrification. TTHMFP measurements across all management units ranged from 141 to 1731 microg L(-1), well in excess of the maximum contaminant level of 80 microg L(-1) established by the Environmental Protection Agency. STHMFP measurements demonstrated over twofold variation ( approximately 4 to approximately 8 mmol total THM/mol DOC) across the management areas, indicating the dependence of reactivity on DOC composition. The results indicate that land management strongly controls the quantity and quality of DOC to reach shallow ground water and hence should be considered when managing ground water resources and in any efforts to mitigate contamination of ground water with carbon-based contaminants, such as pesticides and pharmaceuticals.     

The need for integration of drought monitoring tools for proactive food security management in sub‐Saharan Africa

Reducing the impact of drought and famine remains a challenge in sub‐Saharan Africa despite ongoing drought relief assistance in recent decades. This is because drought and famine are primarily addressed through a crisis management approach when a disaster occurs, rather than stressing preparedness and risk management. Moreover, drought planning and food security efforts have been hampered by a lack of integrated drought monitoring tools, inadequate early warning systems (EWS), and insufficient information flow within and between levels of government in many sub‐Saharan countries. The integration of existing drought monitoring tools for sub‐Saharan Africa is essential for improving food security systems to reduce the impacts of drought and famine on society in this region. A proactive approach emphasizing integration requires the collective use of multiple tools, which can be used to detect trends in food availability and provide early indicators at local, national, and regional scales on the likely occurrence of food crises. In addition, improving the ability to monitor and disseminate critical drought‐related information using available modern technologies (e.g., satellites, computers, and modern communication techniques) may help trigger timely and appropriate preventive responses and, ultimately, contribute to food security and sustainable development in sub‐Saharan Africa.     

Grassland Plant Composition Alters Vehicular Disturbance Effects in Kansas,USA

Many “natural” areas are exposed to military or recreational off-road vehicles. The interactive effects of different types of vehicular disturbance on vegetation have rarely been examined, and it has been proposed that some vegetation types are less susceptible to vehicular disturbance than others. At Fort Riley, Kansas, we experimentally tested how different plant community types changed after disturbance from an M1A1 Abrams tank driven at different speeds and turning angles during different seasons. The greatest vegetation change was observed because of driving in the spring in wet soils and the interaction of turning while driving fast (vegetation change was measured with Bray-Curtis dissimilarity). We found that less vegetation change occurred in communities with high amounts of native prairie vegetation than in communities with high amounts of introduced C₃ grasses, which is the first experimental evidence we are aware of that suggests plant communities dominated by introduced C₃ grasses changed more because of vehicular disturbance than communities dominated by native prairie grasses. We also found that vegetation changed linearly with vehicular disturbance intensity, suggesting that at least initially there was no catastrophic shift in vegetation beyond a certain disturbance intensity threshold. Overall, the intensity of vehicular disturbance appeared to play the greatest role in vegetation change, but the plant community type also played a strong role and this should be considered in land use planning. The reasons for greater vegetation change in introduced C₃ grass dominated areas deserve further study.     

Evaluation of regression methodology with low-frequency water quality sampling to estimate constituent loads for ephemeral watersheds in Texas

Water quality regulation and litigation have elevated the awareness and need for quantifying water quality and source contributions in watersheds across the USA. In the present study, the regression method, which is typically applied to large (perennial) rivers, was evaluated in its ability to estimate constituent loads (NO(3)-N, total N, PO(4)-P, total P, sediment) on three small (ephemeral) watersheds with different land uses in Texas. Specifically, regression methodology was applied with daily flow data collected with bubbler stage recorders in hydraulic structures and with water quality data collected with four low-frequency sampling strategies: random, rise and fall, peak, and single stage. Estimated loads were compared with measured loads determined in 2001-2004 with an autosampler and high-frequency sampling strategies. Although annual rainfall and runoff volumes were relatively consistent within watersheds during the study period, measured annual nutrient and sediment concentrations and loads varied considerably for the cultivated and mixed watersheds but not for the pasture watershed. Likewise, estimated loads were much better for the pasture watershed than the cultivated and mixed landuse watersheds because of more consistent land management and vegetation type in the pasture watershed, which produced stronger correlations between constituent loads and mean daily flow rates. Load estimates for PO(4)-P were better than for other constituents possibly because PO(4)-P concentrations were less variable within storm events. Correlations between constituent concentrations and mean daily flow rate were poor and not significant for all watersheds, which is different than typically observed in large rivers. The regression method was quite variable in its ability to accurately estimate annual nutrient loads from the study watersheds; however, constituent load estimates were much more accurate for the combined 3-yr period. Thus, it is suggested that for small watersheds, regression-based annual load estimates should be used with caution, whereas long-term estimates can be much more accurate when multiple years of concentration data are available. The predictive ability of the regression method was similar for all of the low-frequency sampling strategies studied; therefore, single-stage or random strategies are recommended for low-frequency storm sampling on small watersheds because of their simplicity.     

A comparison of sediment deposition in two adjacent floodplains of the River Adour in southwest France

Two floodplains within the catchment of the River Adour (SW France) have been examined in order to analyse spatio-temporal variations in discharge and suspended matter flux. Both floodplain zones were found to be excellent sites for the interception of suspended sediment. The narrow riparian vegetative strips (RVS) within each zone were found to retain 92-98% of the sediment trapped within the floodplain during each of three separate flood events. The precise level of sediment deposited within the floodplain was found to be dependent on micro-topographical features and the nature of the vegetation: the wooded areas within the RVS being particularly effective at trapping sediment. Mean masses of sediment collected in the flood plains ranged from 75kgm(-2) in the RVS to 0.02kgm(-2) in the areas of the floodplain inundated by back-up flows. Using data on discharge and sediment fluxes within the catchment gathered over a period of 25 years it is possible to discern how hydroclimatic fluctuations have affected the watershed with periods of sediment retention within the floodplain zones alternating with periods of sediment export. Anthropogenic activity, involving river management, including the cutting of meanders, the construction of dykes for flood prevention and the use of water for agricultural purposes, has also had a major impact during this period, particularly in the downstream areas of the catchment.     

FTABLE Generation Method Effects on Instream Fecal Bacteria Concentrations Simulated With HSPF1

Abstract: Computer simulation models are used extensively for the development of total maximum daily loads (TMDLs). Specifically, the Hydrological Simulation Program‐FORTRAN (HSPF) is used in Virginia for the development of TMDLs for bacteria impairments. HSPF estimates discharge from a reach using function tables (FTABLES). The FTABLE relates stream stage, surface area, and volume to discharge from a reach. In this study, five FTABLE estimation methods were assessed by comparing their effect on various simulation outputs. Four “field‐based” methods used detailed cross‐sectional data collected via site surveys. A fifth “digital‐based” method used digital elevation data in combination with the Natural Resources Conservation Service Regional Hydraulic Geometry Curves. Sets of FTABLEs created using each method were used in simulations of instream bacteria concentration for a Virginia watershed. Several statistics relating to instream bacteria including long‐term average concentration, die‐off, and the violation rate of Virginia’s bacteria criterion were compared. The pair‐wise Student’s t‐test was used for the comparison. The HSPF simulations that used FTABLES estimated from digitally based data consistently produced significantly higher long‐term average instream fecal bacteria concentrations, significantly lower instream fecal bacteria die‐off, which is related to differences in residence time in the streams, and significantly higher water quality criterion violation rates.     

Measuring the flux at the interface of coal-tar impacted sediment and river water near a former MGP site

Determining water movement through contaminated sediment is critical for characterizing transport of chemicals from the sediment to the overlying water. Field studies to characterize the water flow across the sediment-water interface within a river adjacent to a former manufactured gas plant site were conducted. For this purpose, a new design of an interfacial flow meter was developed and tested. The in situ components of the system consisted of: a cylinder with an interfacial area of 2342 cm2; a dome attached to the cylinder; and a flow tube that allows water to flow from inside the dome to the river at the rate equal to the specific discharge across the sediment-water boundary. A 'heat-pulse' method was used to measure flow by heating the center of the flow tube for a brief time period and measuring the temperature profile within the tube over time. The system was calibrated to measure volumetric flux in the range 1.5-4.0 cm d(-1), however using a flow-addition method, the measurement of lower velocities also was accomplished, and calibration at higher fluxes is possible. From the groundwater flow at the interface of the coal-tar impacted sediment and information on the sediment pore water concentrations of several PAHs (poly-cyclic aromatic hydrocarbons), the mass flux of these PAHs to the river were estimated. Information on PAH mass flux at the sediment-water interface is useful for site assessment, including the evaluation of remediation alternatives and longer term site characterization.     

Toxicity and hazard of a mixture of SSRIs to zooplankton communities evaluated in aquatic microcosms

The toxicity and hazard of a mixture of selective serotonin reuptake inhibitors (SSRIs), including fluoxetine, fluvoxamine, and sertraline, to zooplankton communities were evaluated using 120,00l outdoor microcosms. Acute (day 4) and chronic (day 35) zooplankton abundance and species richness were assessed for Rotifera, Cladocera, and Copepoda. For acute SSRI exposures, rotifers were the most sensitive zooplankton taxa to changes in abundance (predicted no effect concentration (PNEC)=19 nM); however, no effects in zooplankton species richness were observed for this treatment period. A decrease in Copepoda abundance and species richness was observed following chronic exposures of SSRIs (PNEC=9.1 nM). A 99th-centile predicted environmental concentration (PEC=0.51 nM) yielded HQs at least two orders of magnitude below 1. Therefore, mixtures of SSRIs do not appear to present a hazard to zooplankton communities at environmentally relevant concentrations.     

Fuel consumption, emissions estimation, and emissions cost estimates using global positioning data

The methodology laid out in this paper shows that typical operational data from vehicle fleets monitored by a global positioning system (GPS) can be used to estimate heavy-duty diesel vehicle (HDDV) emissions, thereby enabling waste managers and governing bodies to internalize the responsibility for socioenvironmental costs traditionally absorbed by external parties. Although municipal solid waste (MSW) collection vehicles are the subjects of this particular study, the methodology presented here can be applied to any fleet of vehicles monitored by GPS. This study indicates that MSW collection trucks may be considerably less fuel efficient in the field than published values for HDDV fuel efficiency suggest. The average fuel efficiency of one MSW collection truck was estimated as 0.90 +/- 0.44 km/L (2.12 +/- 1.03 mi/gal). This same truck would generate approximately 42 metric tons of CO2 equivalents/yr, which is comparable to the greenhouse gas emissions of a large sport utility vehicle driving six times the distance, in town, for a year. In terms of the impacts such emissions have, projections for the monetary cost of emissions are available but highly variable. They suggest that the external monetary costs of emissions range between 6 and 39% of the annual fuel costs for the studied MSW collection truck. The results of this study indicate a need for further research into valuation of the hidden, external costs of emissions, borne by local and global socioecological communities. The possible implications of this result include poorly advised fleet procurement decisions and underestimation of MSW collection fleet emissions.