Fine-Scale Detection of Estuarine Water Quality with Managed Freshwater Releases

Freshwater pulses to subtropical estuaries often occur on time scales less than 1 week. In particular, introduction of low-level pulses are potentially important during the dry season (November–April) when freshwater is scarce. Determining potential ecological benefits of pulses requires an innovative method of data acquisition at the appropriate spatial and temporal scales. The South Florida Water Management District conducted a pilot study to assess changes in water column attributes with pulse releases to the Caloosahatchee River Estuary (CRE) from January to April 2012. An average inflow of 450 cfs was targeted for a series of freshwater pulses. This study utilized an onboard, flow-through system to record surface water temperature, salinity (S), pH, dissolved oxygen, turbidity, and in situ chlorophyll a (in situ CHL) at 5 s intervals along the 42-km length of the estuary. On each of seven research cruises, the vessel stopped at multiple stations to conduct vertical water column profiles. Salinity increased throughout the CRE as inflow decreased during the study period. Simple correlation and partial least squares regression were used to determine that the downstream locations of the S?=?10 isohaline and the maximum CHL concentration (in situ CHL_max) were positively related to inflow. While the in situ CHL_max was located 12–20 km downstream on five of the cruises, it was only a few kilometer from the estuary head on the first (1/12) and last (4/11) dates. It is possible that two circumstances related to freshwater inflow accounted for this pattern. First, water column stratification before January could have stimulated remineralization and primary production. Second, inflow ceased as water temperature increased to 26.0 °C by April to promote algal growth. Further study of the relationships among inflow, water level, flushing time, and CHL is warranted. Future efforts will examine the range of wet season discharge by incorporating a sensor for colored dissolved organic matter to fully connect inflow, salinity, submarine light, and phytoplankton attributes in the CRE.     

Strontium isotopic evidence for prehistoric transport of gray‐ware ceramic materials in the eastern Grand Canyon region,USA

Through a novel application of strontium (Sr) isotopic analysis, we evaluate geological sources for prehistoric ceramics in the eastern Grand Canyon region of northern Arizona, focusing on two gray‐ware traditions in the Upper Basin of the Coconino Plateau. Building on a conceptual framework for the general potential of Sr isotopes in the analysis of geological materials, we suggest that the eastern Grand Canyon is specifically well suited archaeologically and geologically for: (1) exploring the utility of Sr isotopes for ceramic provenance research and (2) testing long‐standing hypotheses that gray‐ware ceramics were invariably made with local materials. Sr isotopic compositions indicate that the ceramic samples represent at least three different geological sources, and that different raw materials were used in the manufacture of the two gray‐ware traditions found in the Upper Basin. One of the gray‐ware traditions is not compositionally consistent with local geology, indicating that either the ceramics or the raw materials were transported at least 20 km to the Upper Basin. © 2011 Wiley Periodicals, Inc.     

A new shoreline displacement model for the last 7 ka from eastern James Bay, Canada

The shoreline displacement history of the eastern James Bay lowlands in the last 7 ka has been investigated by means of AMS radiocarbon dating of sediments cored from wetlands. We present twelve radiocarbon dates on macrofossils from six sites spread along a gradient of increasing land age and elevation. Palynomorph analysis (pollen, spores, and dinoflagellate cysts) was used to define the isolation stratigraphy. During the last 7 ka the shoreline elevation has regressed at a decreasing rate. The rate of shoreline emergence was initially rapid (6. 5 m/ 100 yr) between 6850 and  6400 cal yr BP then slowed down to 1.4– 2 m/ 100 yr during the late Holocene. Examination of previous relative sea level data based upon mollusc shells reveals high levels of uncertainty that mask potential temporal variability.     

Discussion: The Hawkesbury Sandstone: A critical review of proposed environmental models

A critical evaluation of conflicting hypotheses for the deposition of the Hawkes‐bury Sandstone suggests that the Barrier Island‐Tidal Delta Model of Conolly (1969) is preferable to the Low Sinuosity River (Brahmaputra) Model of Conaghan & Jones (1975).     

Coliform Bacteria in New Jersey Domestic Wells: Influence of Geology,Laboratory, and Method

Following passage of the New Jersey Private Well Testing Act, 50,800 domestic wells were tested between 2002 and 2007 for the presence of total coliform (TC) bacteria. Wells containing TC bacteria were further tested for either fecal coliform or Escherichia coli (FC/E. coli) bacteria. Analysis of the data, generated by 39 laboratories, revealed that the rate of coliform detections in groundwater (GW) was influenced by the laboratory and the method used, and also by geology. Based on one sample per well, TC and FC/E. coli were detected in wells located in bedrock 3 and 3.7 times more frequently, respectively, than in wells located in the unconsolidated strata of the Coastal Plain. In bedrock, detection rates were higher in sedimentary rock than in igneous or metamorphic rock. Ice‐age glaciers also influenced detection rates, most likely by removing material in some areas and depositing thick layers of unconsolidated material in other areas. In bedrock, coliform bacteria were detected more often in wells with a pH of 3 to 6 than in wells with a pH of 7 to 10 whereas the reverse was true in the Coastal Plain. TC and FC/E. coli bacteria were detected in 33 and 9.5%, respectively, of sedimentary rock wells with pH 3 to 6. Conversely, for Coastal Plain wells with pH 3 to 6, detection rates were 4.4% for TC and 0.6% for FC/E. coli.     

Geometric probability and GIS: some applications for the statistics of intersections

This paper identifies analytical and empirical methods for determining the probability that lines and areas intersect tiles in a regular tessellation. Such intersections are common in geographical information systems (GIS) applications. Knowledge of intersection probabilities is valuable in many instances, including estimating complexity and time required to process a distance or viewshed operation, developing optimal tiling schemes for national georeferencing systems, precalculating the number of map sheets a spatial feature may occupy, and identifying appropriate cell resolutions for vector-to-raster conversions. Buffon's Needle-type solutions from the field of geometric probability provide the framework for deriving probabilities for lines. Probabilities for simple areas like rectangles and circles are derived using geometric techniques and illustrated using hypothetical examples. Employing such probabilities in spatial analysis may yield more rigorous and theoretically informed results from GIS analysis, leading to better decisions and greater insight into spatial phenomena.     

Implications of the 2011 M9.0 Tohoku Japan earthquake for the treatment of site effects in large earthquakes

Site response in Japan is characterized using thousands of surface and borehole recordings from events of moment magnitude $(\mathbf{M}) > 5.5$ collected by the KiK-net network, including the 2011 M9.0 Tohoku earthquake. Site amplification is defined by the ratio of motions at the surface to those at depth (within the borehole), corrected for the depth effect due to destructive interference using a technique based on cross-spectral ratios between surface and down-hole motions. Site effects were particularly strong at high frequencies, despite the expectation that high-frequency response may be damped by nonlinear effects. In part, the large amplitudes at high frequencies are due to the prevalence of shallow soil conditions in Japan. We searched for typical symptoms for soil nonlinearity, such as a decrease in the predominant frequency and/or amplification, using spectral ratios of weak to strong ground motions. Localized nonlinearity occurred at some recording sites, but was not pervasive. We developed a general empirical model to express site amplification for the KiK-net sites as a function of common site variables, such as the average shear-wave velocity in the uppermost 30 m ( $\text{ V}_\mathrm{S30})$ and the horizontal-to-vertical (H/V) spectral ratio. We use the model to estimate site-corrected ground-motions for the Tohoku mainshock for a reference site condition; these motions are in reasonable agreement with the predictions of some of the published ground motion prediction equations for subduction zones.     

Non‐iterative equivalent linearization of inelastic SDOF systems for earthquakes in Japan and California

The seismic performance of existing structures can be assessed based on nonlinear static procedures, such as the Capacity Spectrum Method. This method essentially approximates peak responses of an inelastic single‐degree‐of‐freedom (SDOF) system using peak responses of an equivalent linear SDOF model. In this study, the equivalent linear models of inelastic SDOF systems are developed based on the constant strength approach, which does not require iteration for assessing the seismic performance of existing structures. To investigate the effects of earthquake type and seismic region on the equivalent linear models, four ground‐motion data sets—Japanese crustal/interface/inslab records and California crustal records—are compiled and used for nonlinear dynamic analysis. The analysis results indicate that: (1) the optimal equivalent linear model parameters (i.e. equivalent vibration period ratio and damping ratio) decrease with the natural vibration period, whereas they increase with the strength reduction factor; (2) the impacts of earthquake type and seismic region on the equivalent linear model parameters are not significant except for short vibration periods; and (3) the degradation and pinching effects affect the equivalent linear model parameters. We develop prediction equations for the optimal equivalent linear model parameters based on nonlinear least‐squares fitting, which improve and extend the current nonlinear static procedure for existing structures with degradation and pinching behavior. Copyright © 2010 John Wiley & Sons, Ltd.     

Serpentine geology links to water quality and heavy metals in sediments of a stream system in central Queensland,Australia

Serpentinite soils, common throughout the world, are characterized by low calcium-to-magnesium ratios, low nutrient levels and elevated levels of heavy metals. Yet the water quality and heavy metal concentrations in sediments of streams draining serpentine geology have been little studied. The aim of this work was to collect baseline data on the water quality (for both wet and dry seasons) and metals in sediments at 11 sites on the Marlborough Creek system, which drains serpentine soils in coastal central Queensland, Australia. Water quality of the system was characterized by extremely hard waters (555–698 mg/L as CaCO₃), high dissolved salts (684–1285 mg/L), pH (8.3–9.1) and dissolved oxygen (often >110% saturation). Cationic dominance was Mg > Na > Ca > K and for anions HCO₃ > Cl > SO₄. Al, Cu and Zn in stream waters were naturally high and exceeded Australian and New Zealand Environment and Conservation Council guidelines. Conductivity displayed the highest seasonal variability, decreasing significantly after wet season flows. There was little seasonal variation in pH, which often exceeded regional guidelines. Stream sediments were enriched with concentrations of Ni, Cr, Co and Zn up to 35, 21, 10 and 2 times the world average for shallow sediments, respectively. Concentrations for Ni and Cr were up to 60 and 16 times those of the relevant Interim Sediment Quality Guidelines Low Trigger Values, respectively. The distinctive nature of the water and sediment data suggests that it would be appropriate to establish more localized water quality and sediment guidelines for the creek system for the water quality parameters conductivity, Cu and Zn (and possibly Cr and Cd also), and for sediment concentrations of Cd, Cr and Ni.