Flux-based assessment at a manufacturing site contaminated with trichloroethylene

Groundwater and contaminant fluxes were measured, using the passive flux meter (PFM) technique, in wells along a longitudinal transect passing approximately through the centerline of a trichloroethylene (TCE) plume at a former manufacturing plant located in the Midwestern US. Two distinct zones of hydraulic conductivity were identified from the measured groundwater fluxes; a 6-m-thick upper zone ( approximately 7 m to 13 m below the ground surface or bgs) with a geometric mean Darcy flux (q(0)) of 2 cm/day, and a lower zone ( approximately 13 m to 16.5m bgs) with a q(0) approximately 15 cm/day; this important hydrogeologic feature significantly impacts any remediation technology used at the site. The flux-averaged TCE concentrations estimated from the PFM results compared well with existing groundwater monitoring data. It was estimated that at least 800 kg of TCE was present in the source zone. The TCE mass discharge across the source control plane (85 m x 38 m) was used to estimate the "source strength" ( approximately 365 g/day), while mass discharges across multiple down-gradient control planes were used to estimate the plume-averaged, TCE degradation rate constant (0.52 year(-1)). This is close to the rate estimated using the conventional centerline approach (0.78 year(-1)). The mass discharge approach provides a more robust and representative estimate than the centerline approach since the latter uses only data from wells along the plume centerline while the former uses all wells in the plume.     

Comparison of drinking water mutagenicity with leaching of polycyclic aromatic hydrocarbons from water distribution pipes

The primary objectives of this study were to examine the changes in concentration of six polycyclic aromatic hydrocarbons (PAH) and the possibility of changes in mutagenic potential of treated waters as a result of their passage through commonly used distribution pipes. With the exception of the finished water taken at one treatment plant in which the total concentration of the six PAH was 138.5 parts per trillion (ppt), the total initial concentration in all other treated water ranged from 0 to 13.4 ppt. The corresponding total PAH concentration in water after passage through the distribution pipes varied from 0 to 61.6 ppt. This demonstrated that PAH concentration in water can increase as a result of their passage through coated distribution pipes. Mutagenic activity was also detected in many of the treated water samples, however, the levels of this activity did not correlate with either the transit of water through the distribution system or the levels of PAH in the water. There was some evidence to indicate that the water treatment process itself may have contributed to the mutagenicity observed in the finished water.     

Ecological Monitoring for Assessing the State of the Nearshore and Open Waters of the Great Lakes

The Great Lakes Water Quality Agreement stipulates that the Governments of Canada and the United States are responsible for restoring and maintaining the chemical, physical and biological integrity of the waters of the Great Lakes Basin Ecosystem. Due to varying mandates and areas of expertise, monitoring to assess progress towards this objective is conducted by a multitude of Canadian and U.S. federal and provincial/state agencies, in cooperation with academia and regional authorities. This paper highlights selected long-term monitoring programs and discusses a number of documented ecological changes that indicate the present state of the open and nearshore waters of the Great Lakes.     

Comparison of dynamic subgrid-scale models for simulations of neutrally buoyant shear-driven atmospheric boundary layer flows

Several non-dynamic, scale-invariant, and scale-dependent dynamic subgrid-scale (SGS) models are utilized in large-eddy simulations of shear-driven neutral atmospheric boundary layer (ABL) flows. The popular Smagorinsky closure and an alternative closure based on Kolmogorov’s scaling hypothesis are used as SGS base models. Our results show that, in the context of neutral ABL regime, the dynamic modeling approach is extremely useful, and reproduces several establised results (e.g., the surface layer similarity theory) with fidelity. The scale-dependence framework, in general, improves the near-surface statistics from the Smagorinsky model-based simulations. We also note that the local averaging-based dynamic SGS models perform significantly better than their planar averaging-based counterparts. Lastly, we find more or less consistent superiority of the Smagorinsky-based SGS models (over the corresponding Kolmogorov’s scaling hypothesis-based SGS models) for predicting the inertial range scaling of spectra.     

Development of similarity relationships for energy dissipation rate and temperature structure parameter in stably stratified flows: a direct numerical simulation approach

In this study, a newly developed direct numerical simulation (DNS) solver is utilized for the simulations of numerous stably stratified open-channel flows with bulk Reynolds number (Re _b ) spanning 3400–16,900. Overall, the simulated bulk Richardson number (\(Ri_b\)) ranges from 0.08 (weakly stable) to 0.49 (very stable). Thus, both continuously turbulent and (globally) intermittently turbulent cases are represented in the DNS database. Using this comprehensive database, various flux-based and gradient-based similarity relationships for energy dissipation rate (ε) and temperature structure parameter (\(C_T^2\)) are developed. Interestingly, these relationships exhibit only minor dependency on Re _b . In order to further probe into this Re _b -effect, similarity relationships are also estimated from a large-eddy simulation (LES) run of an idealized atmospheric boundary layer (very high Re _b ) case study. Despite the fundamental differences in the estimation of ε and \(C_T^2\) from the DNS- and the LES-generated data, the resulting similarity relationships, especially the gradient-based ones, from these numerical approaches are found to be remarkably similar. More importantly, these simulated relationships are also comparable, at least qualitatively, to the traditional observational data-based ones. Since these simulated similarity relationships do not require Taylor’s hypothesis and do not suffer from mesoscale disturbances and/or measurement noise, they have the potential to complement the existing similarity relationships.     

Air quality analysis and indexing of Kolkata city with respect to vertical floor heights and seasonal variation

Air pollution is one of the most important global environmental issues. Urban air quality is generally becoming vulnerable especially in the developing countries due to various developmental activities. Several national and international studies prove that air pollution is harmful to human health and its long term exposure contributes to even mortality. Current study has been designed to determine the vertical floor wise air quality status of the city of Kolkata and the seasonal variation of the pollutants during two consecutive years. Particulate matter (PM₁₀ and suspended particulate matter), oxides of nitrogen, sulfur dioxide and carbon monoxide were analyzed for a total number of 135 air quality samples throughout the study area and period. Pollutants were found positively correlated with each other and with the floor heights. According to the air quality indexing, all the places were found affected from moderate to severe air pollution irrespective of the vertical floor heights, seasons and places. Although, no such seasonal trend has been emerged from the study but the number of samples beyond standard is found highest during the winter season followed by pre-monsoon.     

Species-level study on arsenic availability from dietary components

Arsenic (As) contaminated water and foodstuffs are of major concern. Samples of drinking–cooking water (n = 50), raw rice (n = 50), common vegetables (eight types), and common pulses (three types) were collected from households in the endemic region. The study found up to 70% As reduction by using safe water for cooking of rice and vegetables. Speciation study reflected more arsenate than arsenite and other organic arsenicals in all the types of samples. Male intake of 293 μg As through drinking water contained 38 μg arsenite and 246 μg arsenate, and female intake of 199 μg As contained 167 μg arsenate and 25 μg arsenite. In cooked rice, 108 μg As contained 69 μg arsenate and 17 μg arsenite with 9 μg dimethylarsonic acid (DMA). Total As consumption from cooked vegetables was 45 μg with 34 and 4 μg of arsenite and arsenate, respectively, and 5 μg of DMA. Data indicate that cooking with As-free water removes arsenic in already contaminated foodstuffs but without interconversion of the As species, from toxic inorganic to less toxic organic forms.