A microbial community analysis using 16S rRNA gene sequencing was performed on borehole water and a granite rock core from Henderson Mine, a >1,000-meter-deep molybdenum mine near Empire, CO. Chemical analysis of borehole water at two separate depths (1,044 m and 1,004 m below the mine entrance) suggests that a sharp chemical gradient exists, likely from the mixing of two distinct subsurface fluids, one metal rich and one relatively dilute; this has created unique niches for microorganisms. The microbial community analyzed from filtered, oxic borehole water indicated an abundance of sequences from iron-oxidizing bacteria (Gallionella spp.) and was compared to the community from the same borehole after 2 weeks of being plugged with an expandable packer. Statistical analyses with UniFrac revealed a significant shift in community structure following the addition of the packer. Phospholipid fatty acid (PLFA) analysis suggested that Nitrosomonadales dominated the oxic borehole, while PLFAs indicative of anaerobic bacteria were most abundant in the samples from the plugged borehole. Microbial sequences were represented primarily by Firmicutes, Proteobacteria, and a lineage of sequences which did not group with any identified bacterial division; phylogenetic analyses confirmed the presence of a novel candidate division. This “Henderson candidate division” dominated the clone libraries from the dilute anoxic fluids. Sequences obtained from the granitic rock core (1,740 m below the surface) were represented by the divisions Proteobacteria (primarily the family Ralstoniaceae) and Firmicutes. Sequences grouping within Ralstoniaceae were also found in the clone libraries from metal-rich fluids yet were absent in more dilute fluids. Lineage-specific comparisons, combined with phylogenetic statistical analyses, show that geochemical variance has an important effect on microbial community structure in deep, subsurface systems.
Zinc and Cu play important roles in the biogeochemistry of natural systems, and it is likely that these interactions result in mass-dependent fractionations of their stable isotopes. In this study, we examine the relative abundances of dissolved Zn and Cu isotopes in a variety of stream waters draining six historical mining districts located in the United States and Europe. Our goals were to (1) determine whether streams from different geologic settings have unique or similar Zn and Cu isotopic signatures and (2) to determine whether Zn and Cu isotopic signatures change in response to changes in dissolved metal concentrations over well-defined diel (24-h) cycles.
Average δ66Zn and δ65Cu values for streams varied from +0.02‰ to +0.46‰ and −0.7‰ to +1.4‰, respectively, demonstrating that Zn and Cu isotopes are heterogeneous among the measured streams. Zinc or Cu isotopic changes were not detected within the resolution of our measurements over diel cycles for most streams. However, diel changes in Zn isotopes were recorded in one stream where the fluctuations of dissolved Zn were the largest. We calculate an apparent separation factor of ∼0.3‰ (66/64Zn) between the dissolved and solid Zn reservoirs in this stream with the solid taking up the lighter Zn isotope. The preference of the lighter isotope in the solid reservoir may reflect metabolic uptake of Zn by microorganisms. Additional field investigations must evaluate the contributions of soils, rocks, minerals, and anthropogenic components to Cu and Zn isotopic fluxes in natural waters. Moreover, rigorous experimental work is necessary to quantify fractionation factors for the biogeochemical reactions that are likely to impact Cu and Zn isotopes in hydrologic systems. This initial investigation of Cu and Zn isotopes in stream waters suggests that these isotopes may be powerful tools for probing biogeochemical processes in surface waters on a variety of temporal and spatial scales.
","language":"English","publisher":"Elsevier","doi":"10.1016/j.gca.2007.11.014","issn":"00167037","usgsCitation":"Borrok, D.M., Nimick, D., Wanty, R.B., and Ridley, W.I., 2008, Isotopic variations of dissolved copper and zinc in stream waters affected by historical mining: Geochimica et Cosmochimica Acta, v. 72, no. 2, p. 329-344, https://doi.org/10.1016/j.gca.2007.11.014.","productDescription":"16 p.","startPage":"329","endPage":"344","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":241068,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":213442,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1016/j.gca.2007.11.014"}],"volume":"72","issue":"2","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a3fbfe4b0c8380cd647ae","contributors":{"authors":[{"text":"Borrok, David M.","contributorId":26056,"corporation":false,"usgs":true,"family":"Borrok","given":"David","email":"","middleInitial":"M.","affiliations":[],"preferred":false,"id":440512,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Nimick, David","contributorId":19643,"corporation":false,"usgs":true,"family":"Nimick","given":"David","affiliations":[],"preferred":false,"id":440514,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Wanty, Richard B. 0000-0002-2063-6423 rwanty@usgs.gov","orcid":"https://orcid.org/0000-0002-2063-6423","contributorId":443,"corporation":false,"usgs":true,"family":"Wanty","given":"Richard","email":"rwanty@usgs.gov","middleInitial":"B.","affiliations":[{"id":211,"text":"Crustal Geophysics and Geochemistry Science Center","active":true,"usgs":true}],"preferred":true,"id":440513,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Ridley, William I. 0000-0001-6787-558X iridley@usgs.gov","orcid":"https://orcid.org/0000-0001-6787-558X","contributorId":1160,"corporation":false,"usgs":true,"family":"Ridley","given":"William","email":"iridley@usgs.gov","middleInitial":"I.","affiliations":[{"id":171,"text":"Central Mineral and Environmental Resources Science Center","active":true,"usgs":true}],"preferred":true,"id":440515,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70033395,"text":"70033395 - 2008 - Reply to comment by J. Szilagyi on \"Comparison of 15 evaporation methods applied to a small mountain lake in the northeastern USA\" [J. Hydrol. 340 (3-4) (2007) 149-166]","interactions":[],"lastModifiedDate":"2012-03-12T17:21:37","indexId":"70033395","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2342,"text":"Journal of Hydrology","active":true,"publicationSubtype":{"id":10}},"title":"Reply to comment by J. Szilagyi on \"Comparison of 15 evaporation methods applied to a small mountain lake in the northeastern USA\" [J. Hydrol. 340 (3-4) (2007) 149-166]","docAbstract":"[No abstract available]","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Journal of Hydrology","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1016/j.jhydrol.2007.09.050","issn":"00221694","usgsCitation":"Rosenberry, D., Winter, T.C., Buso, D., and Likens, G., 2008, Reply to comment by J. Szilagyi on \"Comparison of 15 evaporation methods applied to a small mountain lake in the northeastern USA\" [J. Hydrol. 340 (3-4) (2007) 149-166]: Journal of Hydrology, v. 348, no. 3-4, p. 566-567, https://doi.org/10.1016/j.jhydrol.2007.09.050.","startPage":"566","endPage":"567","numberOfPages":"2","costCenters":[],"links":[{"id":213166,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1016/j.jhydrol.2007.09.050"},{"id":240764,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"348","issue":"3-4","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505aa767e4b0c8380cd853d1","contributors":{"authors":[{"text":"Rosenberry, D.O. 0000-0003-0681-5641","orcid":"https://orcid.org/0000-0003-0681-5641","contributorId":38500,"corporation":false,"usgs":true,"family":"Rosenberry","given":"D.O.","affiliations":[],"preferred":true,"id":440693,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Winter, T. C.","contributorId":23485,"corporation":false,"usgs":true,"family":"Winter","given":"T.","email":"","middleInitial":"C.","affiliations":[],"preferred":false,"id":440691,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Buso, D.C.","contributorId":31392,"corporation":false,"usgs":true,"family":"Buso","given":"D.C.","email":"","affiliations":[],"preferred":false,"id":440692,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Likens, G.E.","contributorId":68893,"corporation":false,"usgs":true,"family":"Likens","given":"G.E.","email":"","affiliations":[],"preferred":false,"id":440694,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70033461,"text":"70033461 - 2008 - NMR and mass spectrometry of phosphorus in wetlands","interactions":[],"lastModifiedDate":"2012-03-12T17:21:33","indexId":"70033461","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1594,"text":"European Journal of Soil Science","active":true,"publicationSubtype":{"id":10}},"title":"NMR and mass spectrometry of phosphorus in wetlands","docAbstract":"There is at present little information on the long-term stability of phosphorus sequestered in wetlands. Phosphorus sequestered during high loading periods may be relatively unstable and easily remobilized following changes in nutrient status or hydrological regime, but the chemical forms of sequestered phosphorus that do remobilize are largely unknown at this time. A lack of suitable analytical techniques has contributed to this dearth of knowledge regarding the stability of soil organic phosphorus. We analysed phosphorus in soils from the 'head' of Rescue Strand tree island and an adjacent marsh in the Florida Everglades by 31P nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry. Tree islands are important areas of biodiversity within the Everglades and offer a unique opportunity to study phosphorus sequestration because they are exposed to large phosphorus loads and appear to be natural nutrient sinks. The 31P NMR profiling of extracts from surface and sediment samples in the tree island indicates that phosphorus input to Rescue Strand tree island soils is mostly in the form of inorganic ortho-phosphate and is either refractory when deposited or rapidly recycled by the native vegetation into a stable phosphorus pool largely resistant to re-utilization by plants or microbes. Mass spectrometry revealed the presence of inositol hexakisphosphate, a common organic monophosphate ester not previously observed in Everglades' soils. ?? 2008 The Authors.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"European Journal of Soil Science","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1111/j.1365-2389.2007.01008.x","issn":"13510754","usgsCitation":"El-Rifai, H., Heerboth, M., Gedris, T., Newman, S., Orem, W., and Cooper, W., 2008, NMR and mass spectrometry of phosphorus in wetlands: European Journal of Soil Science, v. 59, no. 3, p. 517-525, https://doi.org/10.1111/j.1365-2389.2007.01008.x.","startPage":"517","endPage":"525","numberOfPages":"9","costCenters":[],"links":[{"id":214246,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1111/j.1365-2389.2007.01008.x"},{"id":241946,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"59","issue":"3","noUsgsAuthors":false,"publicationDate":"2008-02-04","publicationStatus":"PW","scienceBaseUri":"505a6147e4b0c8380cd718b9","contributors":{"authors":[{"text":"El-Rifai, H.","contributorId":34733,"corporation":false,"usgs":true,"family":"El-Rifai","given":"H.","email":"","affiliations":[],"preferred":false,"id":440963,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Heerboth, M.","contributorId":73024,"corporation":false,"usgs":true,"family":"Heerboth","given":"M.","email":"","affiliations":[],"preferred":false,"id":440965,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Gedris, T.E.","contributorId":77752,"corporation":false,"usgs":true,"family":"Gedris","given":"T.E.","email":"","affiliations":[],"preferred":false,"id":440966,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Newman, S.","contributorId":7678,"corporation":false,"usgs":true,"family":"Newman","given":"S.","affiliations":[],"preferred":false,"id":440962,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Orem, W. 0000-0003-4990-0539","orcid":"https://orcid.org/0000-0003-4990-0539","contributorId":87335,"corporation":false,"usgs":true,"family":"Orem","given":"W.","affiliations":[],"preferred":false,"id":440967,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Cooper, W.T.","contributorId":40437,"corporation":false,"usgs":true,"family":"Cooper","given":"W.T.","email":"","affiliations":[],"preferred":false,"id":440964,"contributorType":{"id":1,"text":"Authors"},"rank":6}]}} ,{"id":70033493,"text":"70033493 - 2008 - Transport and fate of nitrate at the ground-water/surface-water interface","interactions":[],"lastModifiedDate":"2018-10-22T07:59:39","indexId":"70033493","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2262,"text":"Journal of Environmental Quality","active":true,"publicationSubtype":{"id":10}},"title":"Transport and fate of nitrate at the ground-water/surface-water interface","docAbstract":"Although numerous studies of hyporheic exchange and denitrification have been conducted in pristine, high-gradient streams, few studies of this type have been conducted in nutrient-rich, low-gradient streams. This is a particularly important subject given the interest in nitrogen (N) inputs to the Gulf of Mexico and other eutrophic aquatic systems. A combination of hydrologic, mineralogical, chemical, dissolved gas, and isotopic data were used to determine the processes controlling transport and fate of NO3 − in streambeds at five sites across the USA. Water samples were collected from streambeds at depths ranging from 0.3 to 3 m at three to five points across the stream and in two to five separate transects. Residence times of water ranging from 0.28 to 34.7 d m−1 in the streambeds of N-rich watersheds played an important role in allowing denitrification to decrease NO3 − concentrations. Where potential electron donors were limited and residence times were short, denitrification was limited. Consequently, in spite of reducing conditions at some sites, NO3 − was transported into the stream. At two of the five study sites, NO3 − in surface water infiltrated the streambeds and concentrations decreased, supporting current models that NO3 − would be retained in N-rich streams. At the other three study sites, hydrogeologic controls limited or prevented infiltration of surface water into the streambed, and ground-water discharge contributed to NO3 − loads. Our results also show that in these low hydrologic-gradient systems, storm and other high-flow events can be important factors for increasing surface-water movement into streambeds.
","language":"English","publisher":"ACSESS","doi":"10.2134/jeq2006.0550","issn":"00472425","usgsCitation":"Puckett, L., Zamora, C., Essaid, H., Wilson, J., Johnson, H., Brayton, M., and Vogel, J.R., 2008, Transport and fate of nitrate at the ground-water/surface-water interface: Journal of Environmental Quality, v. 37, no. 3, p. 1034-1050, https://doi.org/10.2134/jeq2006.0550.","productDescription":"17 p.","startPage":"1034","endPage":"1050","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":241919,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":214220,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.2134/jeq2006.0550"}],"volume":"37","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505bb741e4b08c986b327154","contributors":{"authors":[{"text":"Puckett, L.J.","contributorId":27503,"corporation":false,"usgs":true,"family":"Puckett","given":"L.J.","email":"","affiliations":[],"preferred":false,"id":441127,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Zamora, C.","contributorId":47180,"corporation":false,"usgs":true,"family":"Zamora","given":"C.","email":"","affiliations":[],"preferred":false,"id":441128,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Essaid, H.","contributorId":47181,"corporation":false,"usgs":true,"family":"Essaid","given":"H.","email":"","affiliations":[],"preferred":false,"id":441129,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Wilson, J.T.","contributorId":97489,"corporation":false,"usgs":true,"family":"Wilson","given":"J.T.","affiliations":[],"preferred":false,"id":441131,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Johnson, H.M. 0000-0002-7571-4994","orcid":"https://orcid.org/0000-0002-7571-4994","contributorId":75339,"corporation":false,"usgs":true,"family":"Johnson","given":"H.M.","affiliations":[],"preferred":false,"id":441130,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Brayton, M.J.","contributorId":26730,"corporation":false,"usgs":true,"family":"Brayton","given":"M.J.","affiliations":[],"preferred":false,"id":441126,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Vogel, J. R.","contributorId":21639,"corporation":false,"usgs":true,"family":"Vogel","given":"J.","email":"","middleInitial":"R.","affiliations":[],"preferred":false,"id":441125,"contributorType":{"id":1,"text":"Authors"},"rank":7}]}} ,{"id":70033507,"text":"70033507 - 2008 - Understanding the relationship between audiomagnetotelluric data and models, and borehole data in a hydrological environment","interactions":[],"lastModifiedDate":"2012-03-12T17:21:32","indexId":"70033507","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":24,"text":"Conference Paper"},"publicationSubtype":{"id":19,"text":"Conference Paper"},"title":"Understanding the relationship between audiomagnetotelluric data and models, and borehole data in a hydrological environment","docAbstract":"Audiomagnetotelluric (AMT) data and resulting models are analyzed with respect to geophysical and geological borehole logs in order to clarify the relationship between the two methodologies of investigation of a hydrological environment. Several profiles of AMT data collected in basins in southwestern United States are being used for groundwater exploration and hydrogeological framework studies. In a systematic manner, the AMT data and models are compared to borehole data by computing the equivalent one-dimensional AMT model and comparing with the two-dimensional (2-D) inverse AMT model. The spatial length is used to determine if the well is near enough to the AMT profile to quantify the relationship between the two datasets, and determine the required resolution of the AMT data and models. The significance of the quality of the borehole data when compared to the AMT data is also examined.","largerWorkTitle":"SEG Technical Program Expanded Abstracts","language":"English","doi":"10.1190/1.3063902","issn":"10523","usgsCitation":"McPhee, D., and Pellerin, L., 2008, Understanding the relationship between audiomagnetotelluric data and models, and borehole data in a hydrological environment, in SEG Technical Program Expanded Abstracts, v. 27, no. 1, p. 2684-2688, https://doi.org/10.1190/1.3063902.","startPage":"2684","endPage":"2688","numberOfPages":"5","costCenters":[],"links":[{"id":214391,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1190/1.3063902"},{"id":242114,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"27","issue":"1","noUsgsAuthors":false,"publicationDate":"2008-12-15","publicationStatus":"PW","scienceBaseUri":"505bbc5fe4b08c986b328bbc","contributors":{"authors":[{"text":"McPhee, D.K.","contributorId":96775,"corporation":false,"usgs":true,"family":"McPhee","given":"D.K.","email":"","affiliations":[],"preferred":false,"id":441197,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Pellerin, L.","contributorId":94073,"corporation":false,"usgs":true,"family":"Pellerin","given":"L.","email":"","affiliations":[],"preferred":false,"id":441196,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70033573,"text":"70033573 - 2008 - Passive microwave (SSM/I) satellite predictions of valley glacier hydrology, Matanuska Glacier, Alaska","interactions":[],"lastModifiedDate":"2012-03-12T17:21:29","indexId":"70033573","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1807,"text":"Geophysical Research Letters","active":true,"publicationSubtype":{"id":10}},"title":"Passive microwave (SSM/I) satellite predictions of valley glacier hydrology, Matanuska Glacier, Alaska","docAbstract":"We advance an approach to use satellite passive microwave observations to track valley glacier snowmelt and predict timing of spring snowmelt-induced floods at the terminus. Using 37 V GHz brightness temperatures (Tb) from the Special Sensor Microwave hnager (SSM/I), we monitor snowmelt onset when both Tb and the difference between the ascending and descending overpasses exceed fixed thresholds established for Matanuska Glacier. Melt is confirmed by ground-measured air temperature and snow-wetness, while glacier hydrologic responses are monitored by a stream gauge, suspended-sediment sensors and terminus ice velocity measurements. Accumulation area snowmelt timing is correlated (R2 = 0.61) to timing of the annual snowmelt flood peak and can be predicted within ??5 days. Copyright 2008 by the American Geophysical Union.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Geophysical Research Letters","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1029/2008GL034615","issn":"00948","usgsCitation":"Kopczynski, S., Ramage, J., Lawson, D., Goetz, S., Evenson, E., Denner, J., and Larson, G., 2008, Passive microwave (SSM/I) satellite predictions of valley glacier hydrology, Matanuska Glacier, Alaska: Geophysical Research Letters, v. 35, no. 16, https://doi.org/10.1029/2008GL034615.","costCenters":[],"links":[{"id":214280,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1029/2008GL034615"},{"id":241985,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"35","issue":"16","noUsgsAuthors":false,"publicationDate":"2008-08-29","publicationStatus":"PW","scienceBaseUri":"505a757ce4b0c8380cd77b93","contributors":{"authors":[{"text":"Kopczynski, S.E.","contributorId":81318,"corporation":false,"usgs":true,"family":"Kopczynski","given":"S.E.","email":"","affiliations":[],"preferred":false,"id":441491,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Ramage, J.","contributorId":73833,"corporation":false,"usgs":true,"family":"Ramage","given":"J.","affiliations":[],"preferred":false,"id":441490,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Lawson, D.","contributorId":98129,"corporation":false,"usgs":true,"family":"Lawson","given":"D.","affiliations":[],"preferred":false,"id":441492,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Goetz, S.","contributorId":101097,"corporation":false,"usgs":true,"family":"Goetz","given":"S.","email":"","affiliations":[],"preferred":false,"id":441493,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Evenson, E.","contributorId":53180,"corporation":false,"usgs":true,"family":"Evenson","given":"E.","email":"","affiliations":[],"preferred":false,"id":441489,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Denner, J.","contributorId":31215,"corporation":false,"usgs":true,"family":"Denner","given":"J.","email":"","affiliations":[],"preferred":false,"id":441487,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Larson, G.","contributorId":41585,"corporation":false,"usgs":true,"family":"Larson","given":"G.","email":"","affiliations":[],"preferred":false,"id":441488,"contributorType":{"id":1,"text":"Authors"},"rank":7}]}} ,{"id":70033575,"text":"70033575 - 2008 - Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 1. Revised conceptualization of groundwater flow","interactions":[],"lastModifiedDate":"2018-10-22T08:41:54","indexId":"70033575","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":3722,"text":"Water Resources Research","onlineIssn":"1944-7973","printIssn":"0043-1397","active":true,"publicationSubtype":{"id":10}},"title":"Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 1. Revised conceptualization of groundwater flow","docAbstract":"The Biscayne aquifer is a highly transmissive karst limestone that serves as the sole source of drinking water to over two million residents in south Florida. The aquifer is characterized by eogenetic karst, where the most transmissive void space can be an interconnected, touching‐vug, biogenically influenced porosity of biogenic origin. Public supply wells in the aquifer are in close proximity to lakes established by surface mining. The mining of the limestone has occurred to the same depths as the production wells, which has raised concerns about pathogen and chemical transport from these surface water bodies. Hydraulic and forced gradient tracer tests were conducted to augment geologic and geophysical studies and to develop a hydrogeologic conceptual model of groundwater flow and chemical transport in the Biscayne aquifer. Geologic and geophysical data indicate multiple, areally extensive subhorizontal preferential flow zones of vuggy limestone separated by rock with a matrix pore system. The hydraulic response from an aquifer test suggests that the Biscayne aquifer behaves as a dual‐porosity medium; however, the results of the tracer test showed rapid transport similar to other types of karst. The tracer test and concurrent temperature logging revealed that only one of the touching‐vug flow zones dominates transport near the production wells. On the basis of the rising limb of the breakthrough curve, the dispersivity is estimated to be less than 3% of the tracer travel distance, which suggests that the fastest flow paths in the formation are likely to yield limited dilution of chemical constituents.
","language":"English","publisher":"American Geophysical Union","doi":"10.1029/2007WR006058","usgsCitation":"Renken, R.A., Cunningham, K.J., Shapiro, A.M., Harvey, R.W., Zygnerski, M.R., Metge, D.W., and Wacker, M.A., 2008, Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 1. Revised conceptualization of groundwater flow: Water Resources Research, v. 44, no. 8, W08429; 16 p., https://doi.org/10.1029/2007WR006058.","productDescription":"W08429; 16 p.","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":476744,"rank":1,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.1029/2007wr006058","text":"Publisher Index Page"},{"id":242021,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"44","issue":"8","noUsgsAuthors":false,"publicationDate":"2008-08-23","publicationStatus":"PW","scienceBaseUri":"505a7595e4b0c8380cd77c14","contributors":{"authors":[{"text":"Renken, Robert A. rarenken@usgs.gov","contributorId":269,"corporation":false,"usgs":true,"family":"Renken","given":"Robert","email":"rarenken@usgs.gov","middleInitial":"A.","affiliations":[],"preferred":true,"id":441504,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Cunningham, Kevin J. 0000-0002-2179-8686 kcunning@usgs.gov","orcid":"https://orcid.org/0000-0002-2179-8686","contributorId":1689,"corporation":false,"usgs":true,"family":"Cunningham","given":"Kevin","email":"kcunning@usgs.gov","middleInitial":"J.","affiliations":[{"id":269,"text":"FLWSC-Ft. Lauderdale","active":true,"usgs":true}],"preferred":true,"id":441499,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Shapiro, Allen M. 0000-0002-6425-9607 ashapiro@usgs.gov","orcid":"https://orcid.org/0000-0002-6425-9607","contributorId":2164,"corporation":false,"usgs":true,"family":"Shapiro","given":"Allen","email":"ashapiro@usgs.gov","middleInitial":"M.","affiliations":[{"id":37277,"text":"WMA - Earth System Processes Division","active":true,"usgs":true},{"id":436,"text":"National Research Program - Eastern Branch","active":true,"usgs":true}],"preferred":true,"id":441502,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Harvey, Ronald W. 0000-0002-2791-8503 rwharvey@usgs.gov","orcid":"https://orcid.org/0000-0002-2791-8503","contributorId":564,"corporation":false,"usgs":true,"family":"Harvey","given":"Ronald","email":"rwharvey@usgs.gov","middleInitial":"W.","affiliations":[{"id":5044,"text":"National Research Program - Central Branch","active":true,"usgs":true}],"preferred":true,"id":441498,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Zygnerski, Michael R.","contributorId":25469,"corporation":false,"usgs":true,"family":"Zygnerski","given":"Michael","email":"","middleInitial":"R.","affiliations":[],"preferred":false,"id":441500,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Metge, David W. dwmetge@usgs.gov","contributorId":663,"corporation":false,"usgs":true,"family":"Metge","given":"David","email":"dwmetge@usgs.gov","middleInitial":"W.","affiliations":[{"id":5044,"text":"National Research Program - Central Branch","active":true,"usgs":true}],"preferred":true,"id":441501,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Wacker, Michael A. mwacker@usgs.gov","contributorId":2162,"corporation":false,"usgs":true,"family":"Wacker","given":"Michael","email":"mwacker@usgs.gov","middleInitial":"A.","affiliations":[{"id":269,"text":"FLWSC-Ft. Lauderdale","active":true,"usgs":true}],"preferred":true,"id":441503,"contributorType":{"id":1,"text":"Authors"},"rank":7}]}} ,{"id":70033600,"text":"70033600 - 2008 - Effects of ionic strength, temperature, and pH on degradation of selected antibiotics","interactions":[],"lastModifiedDate":"2018-10-22T07:35:02","indexId":"70033600","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2262,"text":"Journal of Environmental Quality","active":true,"publicationSubtype":{"id":10}},"title":"Effects of ionic strength, temperature, and pH on degradation of selected antibiotics","docAbstract":"Aqueous degradation rates, which include hydrolysis and epimerization, for chlortetracycline (CTC), oxytetracycline (OTC), tetracycline (TET), lincomycin (LNC), sulfachlorpyridazine (SCP), sulfadimethoxine (SDM), sulfathiazole (STZ), trimethoprim (TRM), and tylosin A (TYL) were studied as a function of ionic strength (0.0015, 0.050, or 0.084 mg/L as Na2HPO4), temperature (7, 22, and 35°C), and pH (2, 5, 7, 9, and 11). Multiple linear regression revealed that ionic strength did not significantly affect (α = 0.05) degradation rates for all compounds, but temperature and pH affected rates for CTC, OTC, and TET significantly (α = 0.05). Degradation also was observed for TYL at pH 2 and 11. No significant degradation was observed for LNC, SCP, SDM, STZ, TRM, and TYL (pH 5, 7, and 9) under study conditions. Pseudo first-order rate constants, half-lives, and Arrhenius coefficients were calculated where appropriate. In general, hydrolysis rates for CTC, OTC, and TET increased as pH and temperature increased following Arrhenius relationships. Known degradation products were used to confirm that degradation had occurred, but these products were not quantified. Half-lives ranged from less than 6 h up to 9.7 wk for the tetracyclines and for TYL (pH 2 and 11), but no degradation of LIN, the sulfonamides, or TRM was observed during the study period. These results indicate that tetracyclines and TYL at pH 2 and 11 are prone to pH-mediated transformation and hydrolysis in some cases, but not the sulfonamides, LIN nor TRM are inclined to degrade under study conditions. This indicates that with the exception of CTC, OTC, and TET, pH-mediated reactions such as hydrolysis and epimerization are not likely removal mechanisms in surface water, anaerobic swine lagoons, wastewater, and ground water.
","language":"English","publisher":"ACSESS","doi":"10.2134/jeq2007.0230","issn":"00472425","usgsCitation":"Loftin, K., Adams, C., Meyer, M.T., and Surampalli, R., 2008, Effects of ionic strength, temperature, and pH on degradation of selected antibiotics: Journal of Environmental Quality, v. 37, no. 2, p. 378-386, https://doi.org/10.2134/jeq2007.0230.","productDescription":"9 p.","startPage":"378","endPage":"386","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":241924,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":214225,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.2134/jeq2007.0230"}],"volume":"37","issue":"2","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a072ce4b0c8380cd515c3","contributors":{"authors":[{"text":"Loftin, K.A.","contributorId":25775,"corporation":false,"usgs":true,"family":"Loftin","given":"K.A.","email":"","affiliations":[],"preferred":false,"id":441617,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Adams, C.D.","contributorId":35135,"corporation":false,"usgs":true,"family":"Adams","given":"C.D.","email":"","affiliations":[],"preferred":false,"id":441618,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Meyer, M. T.","contributorId":92279,"corporation":false,"usgs":true,"family":"Meyer","given":"M.","email":"","middleInitial":"T.","affiliations":[],"preferred":false,"id":441620,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Surampalli, R.","contributorId":52001,"corporation":false,"usgs":true,"family":"Surampalli","given":"R.","email":"","affiliations":[],"preferred":false,"id":441619,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70033616,"text":"70033616 - 2008 - Mid-infrared diffuse reflectance spectroscopic examination of charred pine wood, bark, cellulose, and lignin: Implications for the quantitative determination of charcoal in soils","interactions":[],"lastModifiedDate":"2018-10-17T10:21:23","indexId":"70033616","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":847,"text":"Applied Spectroscopy","active":true,"publicationSubtype":{"id":10}},"title":"Mid-infrared diffuse reflectance spectroscopic examination of charred pine wood, bark, cellulose, and lignin: Implications for the quantitative determination of charcoal in soils","docAbstract":"Fires in terrestrial ecosystems produce large amounts of charcoal that persist in the environment and represent a substantial pool of sequestered carbon in soil. The objective of this research was to investigate the effect of charring on mid-infrared spectra of materials likely to be present in forest fires in order to determine the feasibility of determining charred organic matter in soils. Four materials (cellulose, lignin, pine bark, and pine wood) and char from these materials, created by charring for various durations (1 to 168 h) and at various temperatures (200 to 450 °C), were studied. Mid-infrared spectra and measures of acidity (total acids, carboxylic acids, lactones, and phenols as determined by titration) were determined for 56 different samples (not all samples were charred at all temperatures/durations). Results showed spectral changes that varied with the material, temperature, and duration of charring. Despite the wide range of spectral changes seen with the differing materials and length/temperature of charring, partial least squares calibrations for total acids, carboxylic acids, lactones, and phenols were successfully created (coefficient of determination and root mean squared deviation of 0.970 and 0.380; 0.933 and 0.227; 0.976 and 0.120; and 0.982 and 0.101 meq/g, respectively), indicating that there is a sufficient commonality in the changes to develop calibrations without the need for unique calibrations for each specific material or condition of char formation.
Mercury and organic carbon concentrations vary dynamically in streamwater at the Sleepers River Research Watershed in Vermont, USA. Total mercury (THg) concentrations ranged from 0.53 to 93.8 ng/L during a 3-year period of study. The highest mercury (Hg) concentrations occurred slightly before peak flows and were associated with the highest organic carbon (OC) concentrations. Dissolved Hg (DHg) was the dominant form in the upland catchments; particulate Hg (PHg) dominated in the lowland catchments. The concentration of hydrophobic acid (HPOA), the major component of dissolved organic carbon (DOC), explained 41–98% of the variability of DHg concentration while DOC flux explained 68–85% of the variability in DHg flux, indicating both quality and quantity of the DOC substantially influenced the transport and fate of DHg. Particulate organic carbon (POC) concentrations explained 50% of the PHg variability, indicating that POC is an important transport mechanism for PHg. Despite available sources of DHg and wetlands in the upland catchments, dissolved methylmercury (DmeHg) concentrations in streamwaters were below detection limit (0.04 ng/L). PHg and particulate methylmercury (PmeHg) had a strong positive correlation (r 2 = 0.84, p < 0.0001), suggesting a common source; likely in-stream or near-stream POC eroded or re-suspended during spring snowmelt and summer storms. Ratios of PmeHg to THg were low and fairly constant despite an apparent higher methylmercury (meHg) production potential in the summer. Methylmercury production in soils and stream sediments was below detection during snowmelt in April and highest in stream sediments (compared to forest and wetland soils) sampled in July. Using the watershed approach, the correlation of the percent of wetland cover to TmeHg concentrations in streamwater indicates that poorly drained wetland soils are a source of meHg and the relatively high concentrations found in stream surface sediments in July indicate these zones are a meHg sink.
Black spruce forests are a dominant covertype in the boreal forest region, and they inhabit landscapes that span a wide range of hydrologic and thermal conditions. These forests often have large stores of soil organic carbon. Recent increases in temperature at northern latitudes may be stimulating decomposition rates of this soil carbon. It is unclear, however, how changes in environmental conditions influence decomposition in these systems, and if substrate controls of decomposition vary with hydrologic and thermal regime. We addressed these issues by investigating the effects of temperature, moisture, and organic matter chemical characteristics on decomposition of fibric soil horizons from three black spruce forest sites. The sites varied in drainage and permafrost, and included a “Well Drained” site where permafrost was absent, and “Moderately well Drained” and “Poorly Drained” sites where permafrost was present at about 0.5 m depth. Samples collected from each site were incubated at five different moisture contents (2, 25, 50, 75, and 100% saturation) and two different temperatures (10°C and 20°C) in a full factorial design for two months. Organic matter chemistry was analyzed using pyrolysis gas chromatography-mass spectrometry prior to incubation, and after incubation on soils held at 20°C, 50% saturation. Mean cumulative mineralization, normalized to initial carbon content, ranged from 0.2% to 4.7%, and was dependent on temperature, moisture, and site. The effect of temperature on mineralization was significantly influenced by moisture content, as mineralization was greatest at 20°C and 50–75% saturation. While the relative effects of temperature and moisture were similar for all soils, mineralization rates were significantly greater for samples from the “Well Drained” site compared to the other sites. Variations in the relative abundances of polysaccharide-derivatives and compounds of undetermined source (such as toluene, phenol, 4-methyl phenol, and several unidentifiable compounds) could account for approximately 44% of the variation in mineralization across all sites under ideal temperature and moisture conditions. Based on our results, changes in temperature and moisture likely have similar, additive effects on in situ soil organic matter (SOM) decomposition across a wide range of black spruce forest systems, while variations in SOM chemistry can lead to significant differences in decomposition rates within and among forest sites.
Largemouth bass (Micropterus salmoides) and common carp (Cyprinus carpio) were collected from 13 sites located in the Mobile (MRB), Apalachicola–Flint–Chattahoochee (ARB), Savannah (SRB), and Pee Dee (PRB) River Basins to document spatial trends in accumulative chemical contaminants, health indicators, and reproductive biomarkers. Organochlorine residues, 2,3,7,8-tetrachlorodibenzo-p-dioxin-like activity (TCDD-EQ), and elemental contaminants were measured in composite samples of whole fish, grouped by species and gender, from each site. Mercury (Hg) and polychlorinated biphenyls (PCBs) were the primary contaminants of concern. Concentrations of Hg in bass samples from all basins exceeded toxicity thresholds for piscivorous mammals (> 0.1 μg/g ww), juvenile and adult fish (> 0.2 μg/g ww), and piscivorous birds (> 0.3 μg/g ww). Total PCB concentrations in samples from the MRB, ARB, and PRB were > 480 ng/g ww and may be a risk to piscivorous wildlife. Selenium concentrations also exceeded toxicity thresholds (> 0.75 μg/g ww) in MRB and ARB fish. Concentrations of other formerly used (total chlordanes, dieldrin, endrin, aldrin, mirex, and hexachlorobenzene) and currently used (pentachlorobenzene, pentachloroanisole, dacthal, endosulfan, γ-hexachlorocyclohexane, and methoxychlor) organochlorine residues were generally low or did not exceed toxicity thresholds for fish and piscivorous wildlife. TCDD-EQs exceeded wildlife dietary guidelines (> 5 pg/g ww) in MRB and PRB fish. Hepatic ethoxyresorufin O-deethylase (EROD) activity was generally greatest in MRB bass and carp. Altered fish health indicators and reproductive biomarker were noted in individual fish, but mean responses were similar among basins. The field necropsy and histopathological examination determined that MRB fish were generally in poorer health than those from the other basins, primarily due to parasitic infestations. Tumors were found in few fish (n = 5; 0.01%); ovarian tumors of smooth muscle origin were found in two ARB carp from the same site. Intersex gonads were identified in 47 male bass (42%) representing 12 sites and may indicate exposure to potential endocrine disrupting compounds. Comparatively high vitellogenin concentrations (> 0.35 mg/mL) in male fish from the MRB, SRB, and PRB indicate exposure to estrogenic or anti-androgenic chemicals.
Quantifying biogeochemical cycles of nitrogen (N) and the associated fluxes to surface waters remains challenging, given the need to deal with spatial and temporal variability and to characterize complex and heterogeneous landscapes. We focused our study on catchments S14 and S15 located in the Adirondack Mountains of New York, USA, which have similar topographic and hydrologic characteristics but contrasting stream nitrate ($\\hbox{NO}_{3}^{-}$) concentrations. We characterized the mechanisms by which $\\hbox{NO}_{3}^{-}$ reaches the streams during hydrological events in these catchments, aiming to reconcile our field data with our conceptual model of factors that regulate nutrient exports from forested catchments. Combined hydrometric, chemical and isotopic (δ$\\hbox{NO}_{3}^{-}$) data showed that the relative contributions of both soil and ground water sources were similar between the two catchments. Temporal patterns of stream chemistry were markedly different between S14 and S15, however, because the water sources in the two catchments have different solute concentrations. During late summer/fall, the largest source of $\\hbox{NO}_{3}^{-}$ in S14 was till groundwater, whereas shallow soil was the largest $\\hbox{NO}_{3}^{-}$ source in S15. $\\hbox{NO}_{3}^{-}$ concentrations in surface water decreased in S14, whereas they increased in S15 because an increasing proportion of stream flow was derived from shallow soil sources. During snowmelt, the largest sources of $\\hbox{NO}_{3}^{-}$were in the near‐surface soil in both catchments. Concentrations of $\\hbox{NO}_{3}^{-}$ increased as stream discharge increased and usually peaked before peak discharge, when shallow soil water sources made the largest contribution to stream discharge. The timing of peaks in stream $\\hbox{NO}_{3}^{-}$concentrations was affected by antecedent moisture conditions. By elucidating the factors that affect sources and transport of N, including differences in the soil nutrient cycling and hydrological characteristics of S14 and S15, this study contributes to the overall conceptualization of $\\hbox{NO}_{3}^{-}$ release from temperate forested catchments.
The synthetic organic compound 4-nonylphenol (NP) has been detected in many human-impacted surface waters in North America. In this study, we examined the ability of NP to alter reproductive competence in male fathead minnows after a 28 day flow-through exposure in a range of environmentally relevant concentrations bracketing the U.S. Environmental Protection Agency toxicity-based NP chronic exposure criterion of 6.1 μg NP/L. Exposure to NP at and above the EPA chronic exposure criterion resulted in an induction of plasma vitellogenin (VTG) within 14 days. However, 7 days after the cessation of exposure, VTG concentrations had dropped more than 50% and few males expressed VTG above the detection threshold. All of the morphological endpoints, including gonadosomatic index, hepatosomatic index, secondary sexual characters, and histopathology, were unaltered by all NP treatments. However, when NP-exposed male fish were allowed to compete with control males for access to nest sites and females, most treatments altered the reproductive competence of exposed males. At lower NP concentrations, exposed males out-competed control males, possibly by being primed through the estrogenic NP exposure in a fashion similar to priming by pheromones released from female fathead minnows. At higher NP exposure concentrations, this priming effect was negated by the adverse effects of the exposure and control males out-competed treated males. Results of this study indicate the complexity of endocrine disrupting effects and the need for multiple analysis levels to assess the effects of these compounds on aquatic organisms.
Temperature is a primary physical and biogeochemical variable in aquatic systems. Field‐based measurement of temperature at discrete sampling points has revealed temperature variability in fluvial systems, but traditional techniques do not readily allow for synoptic sampling schemes that can address temperature‐related questions with broad, yet detailed, coverage. We present results of thermal infrared imaging at different stream discharge (base flow and peak flood) conditions using a handheld IR camera. Remotely sensed temperatures compare well with those measured with a digital thermometer. The thermal images show that periphyton, wood, and sandbars induce significant thermal heterogeneity during low stages. Moreover, the images indicate temperature variability within the periphyton community and within the partially submerged bars. The thermal heterogeneity was diminished during flood inundation, when the areas of more slowly moving water to the side of the stream differed in their temperature. The results have consequences for thermally sensitive hydroecological processes and implications for models of those processes, especially those that assume an effective stream temperature. Copyright © 2008 John Wiley & Sons, Ltd.
The inter-relationship of growth and chemotactic response exhibited by two common soil-inhabiting bacteria was investigated to determine its impact on bacterial migration. Filter-chambers were used to simulate aquifer sediments characterized by vertical gradients of organic contaminants in both artificial groundwater flow systems in the laboratory and within the screened intervals of observation wells in a sandy aquifer. A labile model contaminant (acetate) was added to the top compartments of the three-part chambers, whereas bacteria with a demonstrated propensity to grow on and chemotactically respond to acetate were introduced to the lower compartments. The motility and chemotactic response of Pseudomonas putida F1 resulted in 40 to 110% greater abundances in the upper compartments and concomitant 22 to 70% depletions in the lower compartments relative to the nonchemotactic controls over 2 days. Bacteria were in greatest abundance within the sand plug that separated the upper and lower compartments where sharp acetate gradients induced a strong chemotactic response. This observation was consistent with predictions from a mathematical model. In agreement with the laboratory results, the down-well filter-chamber incubations with Pseudomonas stutzeri in the aquifer indicated that 91% fewer bacteria resided in the lower compartment than the control experiment without acetate at 15 h. The combination of chemotaxis and growth greatly accelerated the migration of bacteria toward and subsequent abundance at the higher acetate concentration.