Search

Since 1995, a network of municipal wells in Iowa, representing all major aquifer types (alluvial, bedrock/karst region, glacial drift, bedrock/nonkarst region), has been repeatedly sampled for a broad suite of herbicide compounds yielding one of the most comprehensive statewide databases of such compounds currently available in the United States. This dataset is ideal for documenting the insight that herbicide degradates provide to the spatial and temporal distribution of herbicides in ground water. During 2001, 86 municipal wells in Iowa were sampled and analyzed for 21 herbicide parent compounds and 24 herbicide degradates. The frequency of detection increased from 17% when only herbicide parent compounds were considered to 53% when both herbicide parents and degradates were considered. Thus, the transport of herbicide compounds to ground water is substantially underestimated when herbicide degradates are not considered. A significant difference in the results among the major aquifer types was apparent only when both herbicide parent compounds and their degradates were considered. In addition, including herbicide degradates greatly improved the statistical relation to the age of the water being sampled. When herbicide parent compounds are considered, only 40% of the wells lacking a herbicide detection could be explained by the age of the water predating herbicide use. However, when herbicide degradates were also considered, 80% of the ground water samples lacking a detection could be explained by the age of the water predating herbicide use. Finally, a temporal pattern in alachlor concentrations in ground water could only be identified when alachlor degradates were considered., Introduction Complete mineralization of most herbicide parent compounds occurs slowly in the environment (Stamper et al. 1997; Larsen and Aamand 2001), with relatively stable and persistent degradates (also referred to [...]

Introduction An important internal 'boundary' within the carbonate bedrock of southwestern and northern Indiana can be defined as the transitional zone in the Devonian rocks where the total dissolved solids [...]

An enhanced three-dimensional unsteady hydrodynamic, multispecies transport fate model called BioChemFOAM was developed in OpenFOAM-free computational fluid dynamic platform for understanding and predicting nutrient dynamics, namely, transport and transformation, in aquatic ecosystems. The study motivation was to better quantify transport and distribution of nutrient species in the Upper Mississippi River Basin (UMRB), a major source of nutrient contributor from intense agriculture. The study is unique in examining the transport and reactivity rates under complex hydrologic conditions where main conveyance channels and backwaters co-exist. The model has two main components: a new coupling of turbulent flow processes with multiple species to modulate transport and reaction rates simulations at channel/backwater areas and a complex chemical and biological transformation module suited for species reaction rates in backwaters. The coupled model was first tested for an idealistic domain/case borrowed from the literature. The final model was calibrated, tested and verified in the UMRB. [ABSTRACT FROM AUTHOR]

Introduction Carbonate rocks of Silurian and Devonian age form the principal bedrock aquifer system for many parts of Indiana. Important water-bearing zones within the Silurian-Devonian aquifers include fossil-reef complexes of [...]

Long-term behavior of sediment bound nitrogen (N) in promoting eutrophication of freshwater lakes can be more efficiently evaluated on the basis of different N-forms rather than on the total nitrogen (TN) content alone, these different N-forms include N in ion-extractable form (IEF-N), carbonate form (CF-N), iron–manganese oxides form (IMOF-N), and N bound in organic matter-sulfide (OSF-N). To assess the N contamination in sediment and its risk to aquatic systems, content and vertical distributions of TN and extractable nitrogen (Ex-N) in sediments from three typical shallow urban lakes in China were studied. The study examines the geochemical relationships between N-forms and physicochemical characteristics in the sediments, in addition to N-forms and its content proportion in sediments and the concentrations of total dissolved nitrogen (TDN) in the lake water column. Results show that the TN content decreased with sediment depth (0–50 cm) in the three lakes. The Ex-N percentages of the TN varied in the ranges of 58.8–63.8, 52.0–95.0, and 41.6–55.7% in sediments sampled from Mochou Lake, Xuanwu Lake, and Daming Lake, respectively. Distributions of the N-forms in the sediments showed significant differences between the three lakes. OSF-N and/or IMOF-N were/was the dominant form(s), and IEF-N, CF-N, and the OSF-N in surface sediment were positively correlated to TDN in lake water (increasing concentrations), whereas the IMOF-N in the sediment represented a negative correlation with TDN in lake water (decreasing concentrations). This suggests that the IEF-N, CF-N and OSF-N forms of nitrogen in the surface sediments could be released into the overlying water column of the lake under certain chemical conditions posing a serious threat to the lake water quality. These results can be beneficial for understanding the behavior of nitrogen transferring process between sediment and overlying water of lakes, and provide critical data for lake restoration. [ABSTRACT FROM AUTHOR]

Research has recently documented the prevalence of a wide variety of pharmaceuticals and other emerging contaminants (ECs) in streams across the United States. Wastewater treatment plants (WWTPs) have been found to be an important source and collection point of ECs to streams as many ECs are incompletely removed during treatment. To investigate the complex in-stream processes (e.g., dilution, sorption, degradation, dispersion, etc.) that can affect ECs following their input from a WWTP and determining if such input is having an effect on the aquatic ecosystem requires the integration of multi-disciplinary efforts at a carefully selected field site. Preliminary work has identified an 8-km reach of Fourmile Creek in central Iowa as an ideal research site to investigate such important research questions pertaining to ECs. Unique aspects of Fourmile Creek included: (1) it single source effluent-dominated stream, (2) background data document the input of a wide variety of ECs from WWTP discharge, (3) small basin size, (4) relatively simple flow system, (5) background data suggest that undefined processes are taking place decreasing the level of select ECs during stream transport, (6) the WWTP uses a treatment technology (activated sludge) typical of many towns in Iowa and the United States (7) a hydrogeologic setting of a low-gradient, small stream (average discharge less than 1.41 m³/s) in glacial drift is typical of many areas in Iowa and across the Midwest, and (8) the existence of a low-head clam approximately 2 km upstream of the WWTP outfall allowing more accurate "above WWTP" and "below WWTP" comparisons in aquatic ecosystems. Furthermore, the WWTP is scheduled to close by 2011 providing a unique opportunity to determine how stream hydrology, water chemistry and aquatic biota react to the removal of the primary source of flow and ECs in this system. This will allow a novel "before" and "after" assessment not previously available in EC research. Research to date at the site has included installation of a streamflow gauging station, dye-tracing tests (to determine water travel times), Lagrangian water-quality sampling at two flow/water temperature regimes, and sampling for ECs in bed sediment. Selected fish have been collected for analysis and identification. In addition, basic fish community and fish health assessment for different seasons and spawning conditions are being analyzed. The research "framework" is unique at Fourmile Creek for investigating the important question of how ECs are transported through the environment and if the presence of such compounds is having a deleterious effect on aquatic ecosystems. [ABSTRACT FROM AUTHOR]