Base cation concentrations in subsurface flow from a forested hillslope - the role of flushing frequency.

A 20-m-wide trench was excavated to bedrock on a hillslope at the Panola Mountain Research Watershed in the Piedmont region of Georgia to determine the effect of upslope drainage area from the soil and bedrock surfaces on the geochemical evolution of base cation concentrations in subsurface flow. Samples were collected from ten 2-m sections and five natural soil pipes during three winter rainstorms in 1996. Base cation concentrations in hillslope subsurface flow were generally highest early and late in the storm response when flow rates were low, but during peak flow, concentrations varied little. Base cation concentrations in matrix flow from the 10 trench sections were unrelated to the soil surface drainage area and weakly inversely related to the bedrock surface drainage area. Base cation concentrations in pipe flow were lower than those in matrix flow and were also consistent with the inverse relation to bedrock surface drainage area found in matrix flow. The left side of the trench, which has the highest bedrock surface drainage area, had consistently lower mean base cation concentrations than the right side of the trench, which has the lowest bedrock surface drainage area. During moderate size rain events of about 20–40 mm, subsurface flow occurred only on the left side of the trench. The greater volume of water that has flowed through the left side of the trench appears to have resulted in greater leaching of base cations from soils and therefore lower base cation concentrations in subsurface flow than in flow from the right side of the trench. Alternatively, a greater proportion of flow that bypasses the soil matrix may have occurred through the hillslope on the left side of the trench than on the right side. Flushing frequency links spatial hillslope water flux with the evolution of groundwater and soil chemistry

Riparian control of stream-water chemistry:Implications for hydrochemical basin models

End-member mixing analysis has been used to determine the hydrological structure for basin hydrochemical models at several catchments. Implicit in this use is the assumption that controlling end members have been identified, and that these end members represent distinct landscape locations. At the Panola Mountain Research Watershed, the choice of controlling end members was supported when a large change in the calcium and sulphate concentration of one of the end members was reflected in the stream water. More extensive sampling of groundwater and soil water indicated, however, that the geographic extent of the contributing end members was limited to the riparian zone. Hillslope solutions were chemically distinct from the riparian solutions and did not appear to make a large contribution to streamflow. The dominant control of the riparian zone on stream-water chemistry suggests that hydrological flow paths cannot be inferred from stream-water chemical dynamics

Quantifying contributions to storm runoff through end-member mixing analysis and hydrologic measurements at the Panola Mountain Research Watershed (Georgia, USA).

The geographic sources and hydrologic flow paths of stormflow in small catchments are not well understood because of limitations in sampling methods and insufficient resolution of potential end members. To address these limitations, an extensive hydrologic dataset was collected at a 10 ha catchment at Panola Mountain Research Watershed near Atlanta, GA, to quantify the contribution of three geographic sources of stormflow. Samples of stream water, runoff from an outcrop, and hillslope subsurface stormflow were collected during two rainstorms in the winter of 1996, and an end-member mixing analysis model that included five solutes was developed. Runoff from the outcrop, which occupies about one-third of the catchment area, contributed 50-55% of the peak streamflow during the 2 February rainstorm, and 80-85% of the peak streamflow during the 6-7 March rainstorm; it also contributed about 50% to total streamflow during the dry winter conditions that preceded the 6-7 March storm. Riparian groundwater runoff was the largest component of stream runoff (80-100%) early during rising streamflow and throughout stream recession, and contributed about 50% to total stream runoff during the 2 February storm, which was preceded by wet winter conditions. Hillslope runoff contributed 25-30% to peak stream runoff and 15-18% to total stream runoff during both storms. The temporal response of the three runoff components showed general agreement with hydrologic measurements from the catchment during each storm. Estimates of recharge from the outcrop to the riparian aquifer that were independent of model calculations indicated that storage in the riparian aquifer could account for the volume of rain that fell on the outcrop but did not contribute to stream runoff. The results of this study generally indicate that improvements in the ability of mixing models to describe the hydrologic response accurately in forested catchments may depend on better identification, and detailed spatial and temporal characterization of the mobile waters from the principal hydrologic source areas that contribute to stream runoff

Phylogeography and Population History of Leopardus guigna, the Smallest American Felid

The guigna (Leopardus guigna) is the smallest and most-restricted New World cat species, inhabiting only around 160,000 km2 of temperate rain forests in southern South America and is currently threatened by habitat loss, fragmentation and human persecution. We investigated phylogeographic patterns of genetic diversity, demographic history and barriers to gene flow with 116 individuals sampled across the species geographic range by analyzing 1,798 base pairs of the mtDNA (496 bp HVSI region, 720 bp NADH-5 gene, 364 bp from 16S gene and 218 bp from ATP-8 gene) and 15 microsatellite loci. Mitochondrial DNA data revealed a clear phylogeographic pattern with moderate separation between northern and southern Chilean populations supporting recognized subspecific partitions based on morphology. A recent demographic expansion was inferred for the southern-most group (San Rafael Lake), presumably due to the complete coverage of this area during the last glacial period, 28000–16000 years BP. Geographical barriers such as the Andes Mountains and the Chacao Channel have partially restricted historic and more-recent gene flow and the Chiloé Island population has diverged genetically since being separated from the mainland 7000 years BP. This is the first study of the genetic structure of this threatened species throughout its whole geographic range

Data from: Phylogeography and population history of Leopardus guigna, the smallest American felid

The guigna (Leopardus guigna) is the smallest and most-restricted New World cat species, inhabiting only around 160,000 km2 of temperate rain forests in southern South America and is currently threatened by habitat loss, fragmentation and human persecution. We investigated phylogeographic patterns of genetic diversity, demographic history and barriers to gene flow with 116 individuals sampled across the species geographic range by analyzing 1,798 base pairs of the mtDNA (496 bp HVSI region, 720 bp NADH-5 gene, 364 bp from 16S gene and 218 bp from ATP-8 gene) and 15 microsatellite loci. Mitochondrial DNA data revealed a clear phylogeographic pattern with moderate separation between northern and southern Chilean populations supporting recognized subspecific partitions based on morphology. A recent demographic expansion was inferred for the southern-most group (San Rafael Lake), presumably due to the complete coverage of this area during the last glacial period, 28000–16000 years BP. Geographical barriers such as the Andes Mountains and the Chacao Channel have partially restricted historic and more-recent gene flow and the Chiloé Island population has diverged genetically since being separated from the mainland 7000 years BP. This is the first study of the genetic structure of this threatened species throughout its whole geographic range

The geochemical evolution of riparian groundwater in a forested piedmont catchment.

The principal weathering reactions and their rates in riparian ground water were determined at the Panola Mountain Research Watershed (PMRW) near Atlanta, Georgia. Concentrations of major solutes were measured in ground water samples from 19 shallow wells completed in the riparian (saprolite) aquifer and in one borehole completed in granite, and the apparent age of each sample was calculated from chloroflourocarbons and tritium/helium-3 data. Concentrations of SiO2, Na+, and Ca2+ generally increased downvalley and were highest in the borehole near the watershed outlet. Strong positive correlations were found between the concentrations of these solutes and the apparent age of ground water that was modern (zero to one year) in the headwaters, six to seven years midway down the valley, and 26 to 27 years in the borehole, located ∼500 m downstream from the headwaters. Mass-balance modeling of chemical evolution showed that the downstream changes in ground water chemistry could be largely explained by weathering of plagioclase to kaolinite, with possible contributions from weathering of K-feldspar, biotite, hornblende, and calcite. The in situ rates of weathering reactions were estimated by combining the ground water age dates with geochemical mass-balance modeling results. The weathering rate was highest for plagioclase (∼6.4 μmol/L/year), but could not be easily compared with most other published results for feldspar weathering at PMRW and elsewhere because the mineral-surface area to which ground water was exposed during geochemical evolution could not be estimated. However, a preliminary estimate of the mineral-surface area that would have contacted the ground water to provide the observed solute concentrations suggests that the plagioclase weathering rate calculated in this study is similar to the rate calculated in a previous study at PMRW, and three to four orders of magnitude slower than those published in previous laboratory studies of feldspar weathering. An accurate model of the geochemical evolution of riparian ground water is necessary to accurately model the geochemical evolution of stream water at PMRW

Leopardus guigna_Control Region HVS-I

Leopardus guigna_Control Region HVS-

Leopardus guigna_16S

Leopardus guigna_16

Long-term follow-up of post-cardiac surgery Mycobacterium chimaera infections: A 5-center case series

OBJECTIVES: In multiple countries, endovascular/disseminated Mycobacterium chimaera infections have occurred in post-cardiac surgery patients in association with contaminated, widely-distributed cardiac bypass heater-cooler devices. To contribute to long-term characterization of this recently recognized infection, we describe the clinical course of 28 patients with 3-7 years of follow-up for survivors. METHODS: Identified at five hospitals in the United States 2010-2016, post-cardiac surgery patients in the cohort had growth of Mycobacterium avium complex (MAC)/M. chimaera from a sterile site or surgical wound, or a clinically compatible febrile illness with granulomatous inflammation on biopsy. Case follow-up was conducted in May 2019. RESULTS: Of 28 patients, infection appeared to be localized to the sternum in four patients. Among 18 with endovascular/disseminated infection who received combination anti-mycobacterial treatment and had sufficient follow-up, 39% appeared to have controlled infection (>12 months), 56% died, and one patient is alive with relapsed bacteremia. While the number of patients is small and interpretation is limited, four (67%) of six patients who had cardiac prosthesis removal/replacement appeared to have controlled infection compared to three (25%) of 12 with retained cardiac prosthesis (p >0.14; Fisher's exact test). CONCLUSIONS: Given poor response to treatment and potential for delayed relapses, post-cardiac surgery M. chimaera infection warrants aggressive treatment and long-term monitoring

Leopardus guigna_NADH-5

Leopardus guigna_NADH-