Groundwater Inflows to the Columbia River Along the Hanford Reach and Associated Nitrate Concentrations

Healthy river ecosystems require the interaction of many physical and biological processes to maintain their status. One physical process supporting biogeochemical cycling is hydrologic exchange (i.e., hydrologic exchange flows, HEFs) between relatively fast-flowing channel waters and slower-flowing surface and subsurface waters (lateral and vertical). Land uses adjacent to rivers have the potential to alter the water quality of off-channel surface and subsurface waters, and HEFs therefore have the potential to deliver solutes associated with river-adjacent land uses to rivers. HEFs can be nonpoint, diffuse sources of pollution, making the ultimate pollution source difficult to identify, especially in large rivers. Here, we seek to identify HEFs in the Columbia River near Richland, WA by looking for anomalies in temperature and electrical conductivity (EC) along the bed of the river in February, June, July, August, and November 2018. These are ultimately the “ends” of HEFs as they are locations of subsurface inflow to the river. We found these anomalies to be a combination of warmer or colder and higher (but not lower) EC than river water. We identified a majority of warm anomalies in February and July 2018, and majority cold anomalies in June, August, and November 2018. High-EC anomalies were found mostly in February, August, and November. Combined, we observe a shift from warm, high EC anomalies dominating in February to equivalent EC, warm anomalies in June, to equivalent EC, cool anomalies dominating July. In August, we also measured dissolved nitrate (NO3-) in-situ to determine whether anomalies were associated with increased NO3- loading to the river, especially along the eastern shoreline, which is dominated by agricultural land use. Inflows along the eastern shoreline have greater concentrations of nitrate than river water (up to 10 mg N–NO3-/L). This research demonstrates that HEFs are temporally and spatially dynamic transferring heat and solutes to rivers.

Hydrological connectivity: an introduction to the concept

The concept of connectivity, especially hydrological connectivity, is used in Earth and environmental sciences as a term and as a conceptual framework for addressing spatial and temporal variability in runoff and sediment transport. Hydrological connectivity can be defined as the transfer of water and sediment through a fluvial system or a dynamic linkage between surface and subsurface waters flowing through a landscape. Five forms of hydrological connectivity may be distinguished: stream-hillslope connectivity, river-floodplain connectivity, stream-lake connectivity, longitudinal or upstream-downstream connectivity, and stream-groundwater connectivity. All of them are interconnected. Hydrological connections are not only unidirectional but cover multiple dimensions and operate across different temporal scales. As a framework, connectivity is useful for understanding spatial variations in runoff. // Pojem povezljivosti, zlasti hidrološke povezljivosti, se v vedah o Zemlji in okolju uporablja kot strokovni izraz in kot konceptualni okvir za obravnavo prostorske ter časovne spremenljivosti v pretoku vode in prenosu gradiva. Hidrološko povezljivost lahko opredelimo kot prenašanje vode in sedimentov skozi rečni sistem ali kot dinamično povezavo med nadzemnimi in podzemnimi vodami, ki tečejo skozi pokrajino. Razlikujemo lahko pet oblik hidrološke povezljivosti: povezljivost med vodotokom in pobočjem, povezljivost med vodotokom in njegovim poplavnim območjem, povezljivost med vodotokom in jezerom, vzdolžno povezljivost med vodotokovim povirnim in izlivnim delom ter povezljivost med vodotokom in podzemno vodo. Vse so med sabo povezane. Vodne povezave niso samo enosmerne, ampak imajo več razsežnosti glede na prostor in čas. Kot okvir je povezljivost koristna za razumevanje prostorskih razlik pri odtoku.

Investigation of the activity of Rn-222 along a small stream in the Representative Basin of Juatuba - MG

ABSTRACT For thousands of years, water has been the focus of experimentation toward solving the challenges associated with human water supply, navigation, irrigation, and sanitation. The use of tracers to study water resources is an efficient approach that can facilitate the modeling of many hydrological scenarios. The goal of this paper is to show results of research that tracked the presence of Rn-222, a natural tracer, in the surface waters of a small watercourse in southeastern part of Brazil. RAD 7, which is an electronic and portable radon detector, was the main instrument used in this survey. We analyzed 117 water samples and converted the radon activity results to effective radiation doses with respect to the hypothetical human consumption of these waters. We also analyzed the sediments of the watercourse. The obtained data showed that the radon activity in the studied waters varies between 0.52-76.96 Bq/m3. We determined the effective dose of all samples to be less than 1 mSv y−1, and its consumption to present no risk to human health. The existence of connections between surface and subsurface waters in the stream is possible, and radon peaks may indicate the existence of discharge zones into the surface water body.

Analysis of Potential for Human Exposure to Aerial Dispersant Application

ABSTRACT The response to the Macondo oil well blow-out in the Gulf of Mexico in 2010, utilized significant quantities of dispersants. The way dispersants make oil available to natural biodegradation, their environmental effects, and overall benefits in oil spill reponse were well understood by the oil and spill response industries. These materials have been studied and improved for over 40 years. In spill response scenarios like Macondo, the large quantities of dispersant utilized raised concerns regarding human exposures. This paper provides the following:An analysis of dispersant spray drift from aerial application of oil dispersant.A review of the exclusion zones established by the Region IV and VI Regional Response Teams (RRT’s).Evidence that the controls to protect cleanup workers were effective. The volume of chemical dispersant utilized in the Macondo response is often presented as an indicator suggesting human exposure. While the volume is interesting, the application, its dilution in the water column, and its environmental persistence are far better measures of the potential for human exposure. Furthermore, the controls that were required by the Federal–On-Scene-Coordinator to ensure responder and public safety are critical considerations. These controls were designed and implemented by Regulators and supported by appropriate health professionals to avoid the possibility of human exposure. These controls were established and published well before the Macondo spill. Studies were undertaken during the 2010 spill response to examine surface and subsurface waters to determine the presence of dispersant constituents. Spill response worker exposure was evaluated in both offshore and on-shore clean-up areas during dispersant application. The studies found no evidence that response workers were exposed to levels of constituents that approached occupational exposure limits.