An evaluation of flow-stratified sampling for estimating suspended sediment loads

Flow-stratified sampling is a new method for sampling water quality constituents such as suspended sediment to estimate loads. As with selection-at-list-time (SALT) and time-stratified sampling, flow-stratified sampling is a statistical method requiring random sampling, and yielding unbiased estimates of load and variance. It can be used to estimate event yields or to estimate mean concentrations in flow classes for detecting change over time or differences from water quality standards. Flow-stratified sampling is described and its variance compared with those of SALT and time-stratified sampling. Time-stratified sampling generally gives the smallest variance of the three methods for estimating storm yields. Flow-stratified sampling of individual storms may fail to produce estimates in some short-lived strata because they may have sample sizes of zero. SALT will tend to give small samples and relatively high variances for small stroms. For longer and more complex hydrographs, having numerous peaks, flow-stratified sampling gives the lowest variance, and the SALT variance is lower than that of time-stratified sampling unless the sample size is very large. A desirable feature of flow-stratified sampling is that the variance can be reduced after sampling by splitting strata, particularly high flow strata that have been visited just once, and recalculating the total and variance. SALT has the potential to produce the lowest variance, but cannot be expected to do so with an auxiliary variable based on stage.     

A microprobe study of metalliferous sediment components

Smectite aggregates, Fe-Mn micronodules, and fish debris from the coarse fraction of a metalliferous sediment sample from the Bauer Basin have been analyzed by microprobe. Both X-ray diffraction and bulk chemical analyses reveal that the smectite, an iron-rich and aluminum-poor nontronite, is the dominant phase. A linear programming solution to a series of mass balance equations indicates that the bulk sample is 70% smectite, 4% todorokite, 13% microlaminated material, and 1% fish debris. Two episodes of micronodule development are indicated by the presence of overgrowths of microlaminated iron-rich material over a homogeneous dense todorokite core. The two micronodule compositions can be explained by reaction of hydrothermally produced amorphous Fe-Mn oxyhydroxides with biogenous opal to form the calculated phase composition. The rare earth elements in the bulk sample can be explained by a similar diagenetic process which distributes rare earth elements of a seawater origin between cerium-enriched micronodules and cerium-depleted fish debris.     

Metal accumulation rates in the Southeast Pacific and the origin of metalliferous sediments

Metal accumulation rates over the East Pacific Rise and Bauer Deep rule out normal authigenic precipitation of iron and manganese as the major mechanism of enrichment to the metalliferous sediments. A hydrothermal source located along the East Pacific Rise is compatible with the transition metal and aluminum accumulation rates. For the Bauer Deep the accumulation rate data suggest either that metal-bearing phases are being transported from the rise to the protected basins of the deep or that a second hydrothermal source exists within the Bauer Deep. A major portion of the minor elements being deposited in the Bauer Deep could result from authigenic precipitation, thus accounting for their distinctive chemical composition.     

Public health impacts of climate change in Washington State: projected mortality risks due to heat events and air pollution

Illness and mortality related to heat and worsening air quality are core public health concerns associated with climate change projections. We examined the historical relationship between age- and cause-specific mortality rates from 1980 through 2006 and heat events at the 99th percentile of humidex values in the historic period from January 1, 1970 to December 31, 2006 in the greater Seattle area (King, Pierce and Snohomish counties), Spokane County, the Tri-Cities (Benton and Franklin counties) and Yakima County; the relative risks of mortality during heat events were applied to population and climate projections for Washington State to calculate number of deaths above the baseline (1980–2006) expected during projected heat events in 2025, 2045 and 2085. Three different warming scenarios were used in the analysis. Relative risks for the greater Seattle area showed a significant dose-response relationship between heat event duration and daily mortality rates for non-traumatic deaths for persons ages 45 and above, typically peaking at four days of exposure to humidex values above the 99th percentile. The largest number of projected excess deaths in all years and scenarios for the Seattle region was found for age 65 and above. Under the middle warming scenario, this age group is expected to have 96, 148 and 266 excess deaths from all non-traumatic causes in 2025, 2045 and 2085, respectively. We also examined projected excess deaths due to ground-level ozone concentrations at mid century (2045–2054) in King and Spokane counties. Current (1997–2006) ozone measurements and mid-twenty-first century ozone projections were coupled with dose-response data from the scientific literature to produce estimates overall and cardiopulmonary mortality. Daily maximum 8-h ozone concentrations are forecasted to be 16–28% higher in the mid twenty-first century compared to the recent decade of 1997–2006. By mid-century in King County the non-traumatic mortality rate related to ozone was projected to increase from baseline (0.026 per 100,000; 95% confidence interval 0.013–0.038) to 0.033 (95% CI 0.017–0.049). For the same health outcome in Spokane County, the baseline period rate of 0.058 (95% CI 0.030–0.085) was estimated increase to 0.068 (95% CI 0.035–0.100) by mid-century. The cardiopulmonary death rate per 100,000 due to ozone was estimated to increase from 0.011 (95% CI 0.005–0.017) to 0.015 (0.007–0.022) in King County, and from 0.027 (95% CI 0.013–0.042) to 0.032 (95% CI 0.015–0.049) in Spokane County. Public health interventions aimed at protecting Washington’s population from excessive heat and increased ozone concentrations will become increasingly important for preventing deaths, especially among older adults. Furthermore, heat and air quality related illnesses that do not result in death, but are serious nevertheless, may be reduced by the same measures.     

Runup uncertainty on planar beaches

Parameterization of wave runup is of paramount importance for an assessment of coastal hazards. Parametric models employ wave (e.g., H_s and L_p) and beach (i.e., β) parameters to estimate extreme runup (e.g., R_2%). Thus, recent studies have been devoted to improving such parameterizations by including additional information regarding wave forcing or beach morphology features. However, the effects of intra-wave dynamics, related to the random nature of the wave transformation process, on runup statistics have not been incorporated. This work employs a phase- and depth- resolving model, based on the Reynolds-averaged Navier-Stokes equations, to investigate different sources of variability associated with runup on planar beaches. The numerical model is validated with laboratory runup data. Subsequently, the role of both aleatory uncertainty and other known sources of runup variability (i.e., frequency spreading and bed roughness) is investigated. Model results show that aleatory uncertainty can be more important than the contributions from other sources of variability such as the bed roughness and frequency spreading. Ensemble results are employed to develop a new parametric model which uses the Hunt (J Waterw Port Coastal Ocean Eng 85:123–152, 1959) scaling parameter \(\beta \left (H_{s}L_{p}\right )^{1/2}\).

     

ESR dating of tooth enamel in Mousterian layer 20, El Castillo,Spain

Nine faunal teeth from layer 20 of El Castillo cave in Cantabrian Spain were dated using electron spin resonance (ESR). Two teeth were rejected due to inconsistent subsample ages, while the remaining teeth yielded a mean age that is consistent with the stratigraphic expectations: 42.7±3.5. Uncertainty in the external γ dose rate results in a potential systematic uncertainty of±6.4ka that should affect all samples equally. The results provide independent confirmation of previously reported ¹⁴C ages for layer 20. © 2010 Wiley Periodicals, Inc.