Coupled radon, methane and nitrate sensors for large-scale assessment of groundwater discharge and non-point source pollution to coastal waters

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Environmental Radioactivity 101 (2010): 553-563, doi:10.1016/j.jenvrad.2009.12.004.We constructed a survey system of radon/methane/nitrate/salinity to find sites of submarine groundwater discharge (SGD) and groundwater nitrate input. We deployed the system in Waquoit Bay and Boston Harbor, MA where we derived SGD rates using a mass balance of radon with methane serving as a fine resolution qualitative indicator of groundwater. In Waquoit Bay we identified several locations of enhanced groundwater discharge, out of which two (Childs and Quashnet Rivers) were studied in more detail. The Childs River was characterized by high nitrate input via groundwater discharge, while the Quashnet River SGD was notable but not a significant source of nitrate. Our radon survey of Boston Harbor revealed several sites with significant SGD, out of these Inner Harbor and parts of Dorchester Bay and Quincy Bay had groundwater fluxes accompanied by significant water column nitrogen concentrations. The survey system has proven effective in revealing areas of SGD and non-point source pollution.R. Camilli acknowledges the National Ocean Partnership Program (NOPP) for supporting the development of the TETHYS mass spectrometer through research grant #OCE-0537173. H. Dulaiova, M. A. Charette and R. Camilli acknowledge funding support from the WHOI Coastal Institute and MIT Sea Grant College Program under NOAA grant number NA06OAR4170019, project number 5710002173. H. Dulaiova was funded by the WHOI Academic Program’s postdoctoral scholarship

Evaluation of the flushing rates of Apalachicola Bay, Florida via natural geochemical tracers

Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 109 (2008): 395-408, doi:10.1016/j.marchem.2007.09.001.We used naturally occurring radium isotopes as tracers of water exchange in Apalachicola Bay, a shallow coastal-plain estuary in northwestern Florida. The bay receives fresh water and radium from the Apalachicola River, and mixes with Gulf of Mexico waters through four inlets. We deployed moored buoys with attached Mn-fibers at several stations throughout the estuary during two summer and two winter periods. After deployment for at least one tidal cycle we measured the ratio of the two short-lived radium isotopes 223Ra (half-life = 11 d) and 224Ra (3.6 d) to estimate “radium ages” of the water in the bay. During our four seasonal deployments the river discharge ranged from 338 to 1016 m3 s- 1. According to our calculations the water turnover time in the bay during these samplings ranged from 6 to 12 days. Age contours in the bay showed that winds and tides as well as river discharge influence the water movement and the residence time of freshwater in the bay. We also calculated the mean age of river water in the bay which was between 5 to 9 days during the studied periods. We suggest that this approach can be used to quantify transport processes of dissolved substances in the bay. For example, soluble nutrient or pollutant transport rates from a point source could be examined. We conclude that the radium age technique is well suited for flushing rate calculations in river dominated shallow estuaries.Henrieta Dulaiova acknowledges support from the NOAA National Estuarine Research Reserve System’s Graduate Research Fellowship (Award # NA03NOS4200055). Scientific support for this research was also provided by grants from NOAA's Cooperative Institute for Coastal and Estuarine Environmental Technology, CICEET (02-606) and the National Science Foundation (OCE03-50514 and OCE05-20723)

GEOTRACES radium isotopes interlaboratory comparison experiment

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2012. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography: Methods 10 (2012): 451-463, doi:10.4319/lom.2012.10.451.In anticipation of the international GEOTRACES program, which will study the global marine biogeochemistry of trace elements and isotopes, we conducted a multi-lab intercomparison for radium isotopes. The intercomparison was in two parts involving the distribution of: (1) samples collected from four marine environments (open ocean, continental slope, shelf, and estuary) and (2) a suite of four reference materials prepared with isotopic standards (circulated to participants as 'unknowns'). Most labs performed well with 228Ra and 224Ra determination, however, there were a number of participants that reported 226Ra, 223Ra, and 228Th (supported 224Ra) well outside the 95% confidence interval. Many outliers were suspected to be a result of poorly calibrated detectors, though other method specific factors likely played a role (e.g., detector leakage, insufficient equilibration). Most methods for radium analysis in seawater involve a MnO2 fiber column preconcentration step; as such, we evaluated the extraction efficiency of this procedure and found that it ranged from an average of 87% to 94% for the four stations. Hence, nonquantitative radium recovery from seawater samples may also have played a role in lab-to-lab variability.This work was funded by grants from the National Science Foundation (OCE- 0751461to M.A.C and H.D. and OCE- 0751867 to W.S.M.)

A new method for the determination of low-level actinium-227 4 in geological samples

10 Abstract We developed a new method for the determi-11 nation of 227 Ac in geological samples. The method 12 uses extraction chromatographic techniques and alpha-13 spectrometry and is applicable for a range of natural matri-14 ces. Here we report on the procedure and results of the 15 analysis of water (fresh and seawater) and rock samples. 16 Water samples were acidified and rock samples underwent 17 total dissolution via acid leaching. A DGA (N,N,N 0 ,N 0 -tetra-18 n-octyldiglycolamide) extraction chromatographic column 19 was used for the separation of actinium. The actinium frac-20 tion was prepared for alpha spectrometric measurement via 21 cerium fluoride micro-precipitation. Recoveries of actinium 22 in water samples were 80 ± 8 % (number of analyses 23 n = 14) and in rock samples 70 ± 12 % (n = 30). The 24 minimum detectable activities (MDA) were 0.017-25 0

Erratum : GEOTRACES radium isotopes interlaboratory comparison experiment

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2012. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography: Methods 10 (2012): 617, doi:10.4319/lom.2012.10.617.In our original paper, Charette, M. A., H. Dulaiova, M. E. Gonneea, P. B. Henderson, W. S. Moore, J. C. Scholten, and M. K. Pham. 2012. GEOTRACES radium isotopes interlaboratory comparison experiment. Limonol. Oceanogr.: Methods 10:451, the incorrect headers were used for Table 9

Lahaina groundwater tracer study -- Lahaina, Maui, Hawaii

The studies presented in this report provide the positive establishment of hydrologic connections between the municipal wastewater injection from the LWRF and the nearshore region of the Kaanapali coast on the Island of Maui, Hawaii, and provide the results from the study’s principal objectives, which have been to: (1) implement a tracer dye study from the LWRF (Section 3), (2) conduct continuous monitoring for the emergence of the injected tracer dyes at the most probable points of emergence at nearshore sites within the coastal reaches of the LWRF (Section 2), (3) conduct an airborne infrared sea surface temperature mapping survey of coastal zone fronting the LWRF in an effort to detect cool and/or warm temperature anomalies that may be indicative of cool submarine groundwater discharge and warm wastewater effluent (Section 4), (4) complete radon and radium radiochemical surveys to detect the emergence points and flow rates of the naturally occurring submarine groundwater along the coastal zone (Section 5), (5) complete geochemical and stable isotopic analyses of LWRF effluent, upland well waters, terrestrial surface waters, marine waters, and submarine groundwater discharge in an effort to help partition the relative contribution of effluent waters to the ocean (Section 6), and (6) combine complete dye emergence breakthrough curves with which to develop groundwater models to determine the LWRFs effluent flow paths and rates of emergence to the coastal zone (Section 7).U.S. Environmental Protection AgencyDepartment of Health, State of HawaiiU.S. Army Engineer Research and Development Cente

A new method for the determination of low-level actinium-227 in geological samples

Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Journal of Radioanalytical and Nuclear Chemistry 296 (2013): 279-283, doi:10.1007/s10967-012-2140-0.We developed a new method for the determination of 227Ac in geological samples. The method uses extraction chromatographic techniques and alpha-spectrometry and is applicable for a range of natural matrices. Here we report on the procedure and results of the analysis of water (fresh and seawater) and rock samples. Water samples were acidified and rock samples underwent total dissolution via acid leaching. A DGA (N,N,N’,N’-tetra-n-octyldiglycolamide) extraction chromatographic column was used for the separation of actinium. The actinium fraction was prepared for alpha spectrometric measurement via cerium fluoride micro-precipitation. Recoveries of actinium in water samples were 80±8 % (number of analyses n=14) and in rock samples 70±12 % (n=30). The minimum detectable activities (MDA) were 0.017-0.5 Bq kg-1 for both matrices. Rock sample 227Ac activities ranged from 0.17 to 8.3 Bq kg-1 and water sample activities ranged from below MDA values to 14 Bq kg-1of 227Ac. From the analysis of several standard rock and water samples with the method we found very good agreement between our results and certified values

Preparation of Mn-fiber standards for the efficiency calibration of the delayed coincidence counting system (RaDeCC)

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 121 (2010): 206-214, doi:10.1016/j.marchem.2010.04.009.Precise measurements of the short lived radium isotopes 223Ra and 224Ra by means of the delayed coincidence counting system (RaDeCC) rely on an efficiency calibration of this system using Mn-fiber standards for which radium activities are exactly known. We prepared seventeen different standards by placing Mn-fibers in seawater spiked with various amounts of 227Ac (with 223Ra in radioactive equilibrium), 228Th (in radioactive equilibrium with 232Th and 224Ra) and 226Ra. We tested for quantitative adsorption of 227Ac and 228Th on the Mn-fibers by: (1) measuring 227Ac and 232Th in the residual solutions after preparing the Mn-fiber standards and (2) monitoring their 223Ra and 224Ra activities over a period of ~100 days. In the residual solutions, the activities of 227Ac and 232Th were < 1.0 % and < 5.3 %, respectively, of the activities initially added to the Mn-fibers. Our results indicate that Milli-Q water washing of the Mn-fibers is the major source of our observed losses of thorium. Measurements of 227Ac standards over 1½ years indicate a significant decrease of measurable 223Ra with time prohibiting the long-term use of 227Ac Mn-fiber standards. We found the 224Ra efficiency to be independent of the range of 227Ac, 228Th and 226Ra activities on the Mn-fibers standards used. The efficiency determination for 223Ra, however, may be biased in the case of relatively high 224Ra activities due to insufficient correction of chance of coincidence. Thus we suggest using a single 227Ac Mn-fiber standard for the efficiency determination for 223Ra.M. Charette and H. Dulaiova were supported by a grant from the National Science Foundation (OCE- 0751461)

Integration of Aerial Thermal Infrared and Radon Surveys to Investigate Groundwater Discharge to Pearl Harbor, Oahu, Hawaii

The largest freshwater spring complex in the Hawaiian Islands discharges groundwater into Pearl Harbor via subaerial springs, submarine springs, and non-point source (diffuse) seepage. We used airborne thermal infrared remote sensing to map the spatial distribution and mixing of cold groundwater discharge throughout the harbor. We then conducted in situ surveys of the harbor\u27s surface, intermediate, and bottom waters for radon-222, a tracer of groundwater discharge. We used these data to calculate groundwater discharge fluxes from radon and salinity mass-balance models. Our fresh groundwater flux estimates were comparable to estimates from published water budget models. Next, we multiplied the groundwater fluxes by representative nutrient concentrations in groundwater end-members from around the harbor. Compared to inputs from other Hawaiian coastlines, Pearl Harbor receives similar dissolved silica, nitrate, and orthophosphate loads on a shore-normalized basis from submarine groundwater discharge. By combining the thermal infrared and radon techniques, we produced linearly and highly correlated relationships between discharge plume areas and groundwater fluxes. Such relationships provide a way to up-scale local groundwater discharge and nutrient fluxes to regional scope