Ratios In Groundwater Research Articles

Mixing of arsenic-rich groundwater and surface water in drinking water distribution systems: Implications for contaminants, disinfection byproducts and organic components

The utilization of groundwaters containing high levels of arsenic (As) for drinking water purposes presents major health and economic challenges for water utilities. One low-cost approach is to mix arsenic-rich groundwater (GW) with arsenic-free surface waters (SW) to achieve acceptable As levels. In this study we investigated the effect of different mixing ratios on water quality in an eastern Croatian water distribution system (WDS). To investigate the effects of mixing on drinking water quality, we measured the organic matter (OM) composition, disinfection byproduct (DBP) and metal concentrations in differently mixed ratios of GW and SW within the WDS. Fluorescence analysis revealed that the GW and SW had similar OM composition, with an almost equal ratio of humic- and protein-like OM throughout the WDS despite fluorescence indices revealing slightly different OM sources between the two water types. The tyrosine-like OM component was more variable, increasing during warmer months and towards the end of the WDS, most likely due to enhanced biofilm formation. Arsenic concentrations decreased to below 10 μg/L in the second half of the sampling campaign. Acceptable water quality was achieved after a period of destabilization and solubilization of loose deposits within the WDS resulting in their mobilization caused by water quality changes. Principal component and classification analysis, regression models and Spearman correlation coefficients revealed an association between As, OM and DBP concentrations with these correlations suggestive of their role in As mobilization in the WDS. Changing source waters, with different OM content and characteristics, corresponded to variable As release within the WDS.

Natural and technogenic elements in soils and water of the lower Yenisey flood plain and terraces: Regional and local landscape geochemical distribution patterns controlled by natural processes

Spatial distributions of Cs-137, Cu, Ni, Zn, Fe, Mn, K, Na, Ca in sediments, soils and water of conjugated landscapes within floodplain and coastal areas of the lower Yenisey were determined in a South-North direction from set. Ust'-Port to Cape Shaitansky. The study showed that these elements could be used to reveal the impact of natural and technogenic sources on local landscapes. The marine influence was traced by increasing salinity Cl- content and a decrease in (Ca+Mg)/(Na+K) ratios in ground water in a seaward direction. Accumulative landscapes of the island in the frontal zone of the delta area appeared to be most enriched in terrestrial elements and ions (Ca, Mg, carbonates) and Cs-137. Data suggest that this area acts as the estuary's first filter zone for river load transport. Permafrost leads to relatively enhanced concentrations of Cu, Zn and Cs-137 in soil profiles at the bottom of the active layer and to enhanced mobility and accumulation of Fe and Mn in oxidized zones. The applied methodology seems to be helpful for the rapid geo-ecological survey of large areas subject to graduated impact.

Strontium isotopic identification of water-rock interaction and ground water mixing.

87Sr/86Sr ratios of ground waters in the Bighorn and Laramie basins' carbonate and carbonate-cemented aquifer systems, Wyoming, United States, reflect the distinctive strontium isotope signatures of the minerals in their respective aquifers. Well water samples from the Madison Aquifer (Bighorn Basin) have strontium isotopic ratios that match their carbonate host rocks. Casper Aquifer ground waters (Laramie Basin) have strontium isotopic ratios that differ from the bulk host rock; however, stepwise leaching of Casper Sandstone indicates that most of the strontium in Casper Aquifer ground waters is acquired from preferential dissolution of carbonate cement. Strontium isotope data from both Bighorn and Laramie basins, along with dye tracing experiments in the Bighorn Basin and tritium data from the Laramie Basin, suggest that waters in carbonate or carbonate-cemented aquifers acquire their strontium isotope composition very quickly--on the order of decades. Strontium isotopes were also used successfully to verify previously identified mixed Redbeds-Casper ground waters in the Laramie Basin. The strontium isotopic compositions of ground waters near Precambrian outcrops also suggest previously unrecognized mixing between Casper and Precambrian aquifers. These results demonstrate the utility of strontium isotopic ratio data in identifying ground water sources and aquifer interactions.

Chlorine‐36 in Ground Water Containing Low Chloride Concentrations

AbstractAnalyses of ground water from wells and springs in the United States indicate a broad regional trend in preanthropogenic (36Cl/total Cl) ×1015 ratios in potable water. Coastal areas influenced by marine chloride have ratios less than 100. These ratios increase inland and reach a maximum of about 1400 in the central and northern Rocky Mountains. However, the magnitude of these regional variations is greatly exceeded at a local level if water samples are considered regardless of age or origin. Most local departures from regional trends can be attributed to mixing of ground water recharge with either 36Cl from nuclear fusion tests to produce higher ratios or mixing with sources of old chloride such as from evaporite minerals to produce lower ratios. A useful interpretation of 36Cl data is difficult unless the origin of the chloride is understood. The interpretation is an unusually difficult problem for water having low chloride concentrations. The assumption that low concentrations originate primarily from wet and dry atmospheric deposition can be questioned even for some dilute waters with less than 2.0 mg/L chloride. Chloride/bromide ratios in ground water can help decipher the origin of the chloride. The presence of nonatmospheric chloride can be identified in part by its association with chloride/bromide mass ratios greater than about 200 in coastal areas and 100 in inland areas. Accurate chloride and bromide analyses are recommended for virtually all studies of 36Cl in natural waters, and particularly those with low concentrations of chloride.

Comment on “Caution Against Interpreting Gasoline Release Dates Based on BTEX Ratios in Ground Water,” by Pedro J.J. Alvarez, Richard C. Heathcote, and Susan E. Powers, Fall 1998 Ground Water Monitoring & Remediation, v. 18, no. 4: 69‐76.

“Our experience shows that BTEX ratios, when used cautiously, often provide valuable information on the age of gasoline fuel release.”

Caution Against Interpreting Gasoline Release Dates Based on BTEX Ratios in Ground Water

“Traces of MTBE in ground water (>10 ppb) do not necessarily indicate recent gasoline contamination.”

Ground‐Water Contaminant Plume Differentiation and Source Determination Using BTEX Concentration Ratios

AbstractConcentration ratios of benzene, toluene, ethylbenzene, and xylenes (BTEX) in ground water can be used for ground‐water contaminant plume differentiation and source determination. Computer modeling utilizing BTEX soil‐water partitioning coefficients and biodegradation rates shows that hydraulic dispersion, retardation, and biodegradation do not significantly modify the BTEX concentration ratios in ground water, particularly those of ethylbenzene and xylenes. Therefore, the BTEX concentration ratios are similar in the contaminant plumes that are derived from a common source or sources of similar BTEX compositions. In the vadose zone, the BTEX concentration ratios in downward‐migrating contaminant free‐product remain essentially unchanged because of the dynamic nature of soil adsorption and restricted natural soil ventilation. The only significant change in the BTEX concentration ratios occurs in the partitioning between ground water and contaminant free‐product as the result of differential BTEX solubilities in water. In the partitioning, benzene/toluene and toluene/ethylbenzene concentration ratios of ground water are 3.6 and 3.3 times greater respectively than the ratios at the source, while the ratios of ethylbenzene and xylenes remain unchanged.The geochemical methods were successfully applied and tested at two sites where multiple ground‐water contaminant plumes from different sources were superimposed. The conclusions of geochemical analysis are consistent with the site‐specific hydraulic characteristics and facility operation histories.

Simultaneous Determination of Argon and Nitrogen

AbstractDenitrification can be confirmed by the presence of excess N2 as indicated by measurement of argon and nitrogen. Previously reported Ar/N2 ratios in ground water have been measured by static gas mass spectrometry, quadrupole mass spectrometry, and gas chromatography. The detector geometry and flared flight tube of the VG Optima isotope ratio mass spectrometer (IRMS) were determined to be fortuitously engineered for the simultaneous and highly precise measurement of Ar (mass 40) and N2+ (mass 28). Certified gas mixtures containing known Ar/N2 ratios were analyzed to assess instrument accuracy. A preparation system for the extraction and purification of Ar and N2 from water samples was developed and tested. δ(Ar/N2) values for prepared air‐saturated water (ASW) samples (24°C) averaged + 1149 ± 8‰ and did not significantly differ from the predicted value relative to atmospheric Ar/N2 of + 1144‰) (p < 0.001). The δ(Ar/N2) from in situ microcosms averaged +1280 ± 22‰ versus atmospheric Ar/N2 and approximated the expected level for ASW of + 1218 at 12°C. Much lower δ5(Ar/N2) values were measured in 18 ground‐water samples collected from a site where denitrification had previously been documented. Samples collected from a site where conditions indicate little or no denitrification have δ(Ar/N2) values close to those for ASW.

Latitudinal variation in oxygen-18 of atmospheric CO2

This report provides information on a potentially important new atmospheric tracer of large-scale behaviour at the Earth's surface, the oxygen isotope composition of CO2. We use measurements on flask air collected from Alaska, Hawaii, Samoa, Tasmania, coastal Antarctica and the South Pole. Recently, we examined 1982–84 measurements of δ18O in CO2 extracted in situ from marine air at Cape Grim, Tasmania1. Here we report on a comparison of Cape Grim flask and in situ data that gives a measure of precision and serves to demonstrate a marked improvement over previous infrequent measurements. While previous data2,3 suggests a north-south gradient, our flask data establish a strong, asymmetric meridional gradient. We argue that this reflects the oxygen isotope ratio in ground water, via mechanisms involving gross catalysed CO2 exchange with leaf (and possibly soil) water. Very large CO2 fluxes are involved, of the order of 200 Gt carbon (C) yr−1.

Bromide ion concentration and Br/Cl ratio of ground water in the southwest region of Gifu Prefecture

Bromide ion concentration and Br/Cl ratio of ground water in the southwest region of Gifu Prefecture

The measurement of 226Ra/ 223Ra activity ratios in ground water as a uranium exploration technique

Measurements were made of the 226Ra/ 223Ra activity ratio in ground waters obtained from drill holes in the vicinity of uranium mineralization in northern Saskatchewan where certain hydrologic parameters, specifically ground-water velocity and direction, had been determined. The results show that it is possible to approximate the distance from a ground-water sampling point to the area of mineralization owing to differences in the half lives of the two radium nuclides. The theoretical basis for the determination of the distances is explained.

Variations in stable‐isotope ratios of ground waters in seismically active regions of California

Measurements of D and 18O concentrations of ground waters in seismically active regions are potentially useful in earthquake prediction and in elucidating mechanisms operative during earthquakes. Principles of this method are discussed and some preliminary data regarding a magnitude 5.7 earthquake at the Oroville Dam in 1975 and a series of events near San Juan Bautista in 1980 are presented to support the utility of such measurements. After earthquakes, the D content of nearby ground waters increased by several permil while the 18O content remained constant. This increase implies that H2O may have either decomposed or reacted to form molecular H2 at depth. It is emphasized that many areas must be investigated for these effects in order to find a sufficient number of "sensitive" water wells and springs to permit a truly effective program of earthquake research.