Quantitative phosphorus measurement: A field test procedure for archaeological site analysis at Piedras Negras,Guatemala

Currently there is a wide interest in the use of chemical analyses for the evaluation of anthropogenically altered soils and other archaeological deposits. Because soil phosphorus levels increase in areas of human habitation, and leave a permanent signature that can only be removed by erosion of the soil itself, phosphorus mapping has become a popular field procedure to indicate areas of habitation where overt evidence of ancient occupance is absent. We have developed a methodology to obtain accurate acid‐extractable phosphorus concentrations (mg/kg) in calcareous soils under the primitive field conditions of Piedras Negras, Guatemala. Predicated on Mehlich‐II acid extractant and colorimetric methods, this procedure processed 36 samples per hour at very low cost per sample. Based on eight replicate measurements of a group of samples, the coefficient of variation of the procedure was 8.3%. Subsequent analysis of 35 soil samples in a controlled laboratory revealed a moderate correlation of 0.44 between the Mehlich‐extractable phosphorus and total phosphorus. The correlation was 0.91 between the Mehlich procedure and Olsen bicarbonate extractable phosphorus, indicating that Mehlich‐based results are similar to those obtainable using a traditional extractable phosphorus method on soils of neutral to alkaline pH. There was a moderate correlation between Mehlich P and ring‐test rating (r = 0.42). The wider dynamic range of the Mehlich extraction, coupled with the use of a battery‐operated colorimeter, facilitated the finding of a refuse midden within an area of phosphate enriched soils. Further tests indicated that phosphorus concentrations measured in the field deviated by only 7% from those made under controlled laboratory conditions. © 2000 John Wiley & Sons, Inc.     

One to four weekly currents on the west coast South island New Zealand continental slope

Current meter measurements from the west coast South Island New Zealand continental slope exhibit flows with dominant time scales of between 1 and 4 weeks as well as the expected diurnal and semidiurnal tides. The alongshore Doodson filtered daily mean flow components are marginally correlated with the alongshore wind. The onshore flow components are marginally correlated with the envelope of the square of the semidiurnal and diurnal tidal flow, which is taken as a measure of energy loss from the tide.Observations from the southern flank of the Challenger Plateau, 200 km north of the continental slope observations and further offshore, also exhibit similar long-period variations. However, here the alongshore flow is more strongly correlated with alongshore wind than at the southern site.     

Chrysophycean cysts in Sierra Nevada (California) lake sediments: paleoecological potential

Thirty-three lakes in the Sierra Nevada range of California were investigated as part of a paleoecological study of the potential effects of acid deposition on sensitive lake/watershed ecosystems. Chrysophyte cysts from surface sediment samples were analyzed and compared with data on pH and alkalinity. This paper identifies the twenty-five dominant chrysophyte cyst taxa and provides information on their morphology, abundance, distribution and ecology.Chrysophycean cysts were generally abundant and well-preserved in lake sediments of our study sites. Twelve taxa occurred in more than twenty of the thirty-three lakes; these taxa were often quite abundant. In contrast, only nine taxa occurred in ten or fewer lakes. Abundance Weighted Mean (AWM) pH varied from 6.45 to 8.34 and AWM alkalinity varied from 46 to 588 eq/L. We delineated pH preference categories, based on AWM pH values and frequency diagrams of cyst abundance vs. lake-water pH. We classified five taxa as acidophilous, nine as circumneutrals, six as alkaliphilous and five as indifferent. Given that the cyst types differ greatly in their abundance relative to pH and alkalinity, it is clear that they have potential for paleolimnological studies of Sierra lakes biogeochemistry.     

The rate of growth of density perturbations in simple big-bang model universes

In this paper we present exact solutions to the density perturbation equation derived by Bonnor for the cases where = _c ,k=1 and = – _c ,k=–1. The solutions when =0,k=1 and =0,k=–1 have been previously published. Using these solutions a quantitative analysis has been carried out that has enabled us to estimate the size of the fluctuations that must be postulated at decoupling in order to explain the formation of the galaxies in these model universes.     

Small-scale electrical resistivity tomography of wet fractured rocks

This paper describes a series of experiments that tested the ability of the electrical resistivity tomography (ERT) method to locate correctly wet and dry fractures in a meso-scale model. The goal was to develop a method of monitoring the flow of water through a fractured rock matrix. The model was a four by six array of limestone blocks equipped with 28 stainless steel electrodes. Dry fractures were created by placing pieces of vinyl between one or more blocks. Wet fractures were created by injecting tap water into a joint between blocks. In electrical terms, the dry fractures are resistive and the wet fractures are conductive. The quantities measured by the ERT system are current and voltage around the outside edge of the model. The raw ERT data were translated to resistivity values inside the model using a three-dimensional Occam's inversion routine. This routine was one of the key components of ERT being tested. The model presented several challenges. First, the resistivity of both the blocks and the joints was highly variable. Second, the resistive targets introduced extreme changes the software could not precisely quantify. Third, the abrupt changes inherent in a fracture system were contrary to the smoothly varying changes expected by the Occam's inversion routine. Fourth, the response of the conductive fractures was small compared to the background variability. In general, ERT was able to locate correctly resistive fractures. Problems occurred, however, when the resistive fracture was near the edges of the model or when multiple fractures were close together. In particular, ERT tended to position the fracture closer to the model center than its true location. Conductive fractures yielded much smaller responses than the resistive case. A difference-inversion method was able to correctly locate these targets.     

Community volunteer assessment of recreational water quality in the Hutt River,Wellington

ABSTRACT

Water is an important component of many recreational opportunities and New Zealand invests significant resources in recreational water quality (RWQ) monitoring to assess risks to public health. However, monitoring primarily focuses on microbiological hazards and RWQ is considerably broader than this. The goal of this study was to take a comprehensive approach to evaluating RWQ while exploring the potential for greater public involvement in monitoring. A popular river swimming site was co-monitored weekly by volunteers and a council field officer. The attributes monitored–water temperature, visual clarity, benthic cyanobacteria and filamentous periphyton cover, E. coli and rubbish–were identified from a volunteer workshop. There was good concordance between volunteer and council data suggesting that volunteer measurements can be considered reliable. This highlights the potential for volunteers, with professional support, including training and quality assurance, to extend council RWQ surveillance to additional monitoring sites while improving public engagement on water management.