First Results of Measurements with a Newly-Designed Phased-Array Sodar with RASS

Summary At a special measuring site for boundary-layer studies as well as land-surface processes the Meteorological Observatory Lindenberg of the German Weather Service (DWD) has recently put into operation a newly-desi gned phased-array SODAR/RASS, which has been developed by METEK on behalf of the DWD. This system provides the vertical profiles of the three-di mensional wind vector in the boundary layer on an operational basis and is furthermore suitable for getting information on the profile of virtual temperature up to about 400 m in height based on the addition of RASS components. The following paper describes both the technique of this SODAR/RASS and the various modes of operation as well as the different options in managing the system. First evaluations on the data availability concerning the maximum height coverage will give an impression on the system’s capabilities. Finally, the accuracy of the derived profiles of winds and temperature will be investigated by means of comparisons of the SODAR/RASS data with measurements of a six-sonde tethered-balloon system as well as meteorological data of a 99 m tower in the vicinity of the system. Received November 27, 1998 Revised April 9, 1999     

Ranking of Placer Gold Prospects in Chile Through Analytic Hierarchy Process

Chile has a rich, but poorly known history of placer gold mining. At present, this sector is almost nonexistent and there are some restrictions for its revival: disperse and partial information on existing resources and limited technical expertise to assess the potential of placer gold mine sites. This paper presents the background, methodology and results of the prioritization process of known prospects of this kind in Chile. This research was part of a publicly funded project aimed to incentivize the development of this industry. The ranking was carried out using the analytic hierarchy process, which allowed to include different quantitative and qualitative variables related to the economic potential, technical aspects, contextual viability and socioeconomic factors in the analysis. The results show that, despite the increasing relevance of environmental and community issues in mining development, the business potential and the economic/technical aspects are the main factors in the early selection of a site to advance in exploration and development activities. Both variables represented around 40% and 37% of weights in the final selection, respectively. In contrast, contextual viability and local socioeconomic impacts only accounted for the remaining 23%. This study also shows that the inclusion of experts with different backgrounds in the process enriches the analysis and does not significantly distort the final outcome of the prioritization. Finally, the relevance of using MCDM tools when assessing the attractiveness of mine sites for their development is highlighted, particularly when public funds for subsequent exploration activities are committed.

     

The dynamics of phytoplankton, bacteria and heterotrophic flagellates at two Banks near Magdeburg in the River Elbe (Germany)

The main objectives of this study were to describe the seasonal standing stock dynamics of phytoplankton, bacterioplankton and heterotrophic flagellates in the highly eutrophic River Elbe (Germany), and to compare the seasonal patterns observed with other streams. Emphasis was placed on examining and assessing abiotic and biotic controlling factors influencing the structure and dynamics of the riverine plankton. All the physico-chemical and biological parameters determined were within the range or somewhat higher (in the case of phytoplankton abundance and biomass) than reported for other large streams. The underwater light conditions resulting from atypically short phytoplankton growth periods of about 6 months per year and the low phytoplankton carbon to chl a ratio of 23 were identified as a major limiting factor for phytoplankton development in the River Elbe. The seasonal distribution pattern of bacterioplankton indicated probable tight trophodynamical coupling both with phytoplankton and with heterotrophic flagellates, whereas heterotrophic flagellates showed a more trophic link with bacterial densities. Although approximately constant DOC and DON levels throughout the year sustained bacterial growth rates, during the phytoplankton growing season an increase of bacterial standing stocks was observed. Although the left-bank sampling site of the Elbe is strongly influenced by the tributaries Mulde and Saale containing higher concentrations of chloride, nitrogen nutrients, heavy metals and organic pollutants, no clear differences were observed between the two sides of the river concerning the biological parameters measured. Possible reasons and the slightly higher phytoplankton abundance and diversity at the right bank are discussed.     

Fine‐scale diet of the Australian sea lion (Neophoca cinerea) using DNA‐based analysis of faeces

We applied DNA‐based faecal analysis to determine the diet of female Australian sea lions (n = 12) from two breeding colonies in South Australia. DNA dietary components of fish and cephalopods were amplified using the polymerase chain reaction and mitochondrial DNA primers targeting the short (~100 base pair) section of the 16S gene region. Prey diversity was determined by sequencing ~50 amplicons generated from clone libraries developed for each individual. Faecal DNA was also combined and cloned from multiple individuals at each colony and fish diversity determined. Diets varied between individuals and sites. Overall, DNA analysis identified a broad diversity of prey comprising 23 fish and five cephalopod taxa, including many species not previously described as prey of the Australian sea lion. Labridae (wrasse), Monacanthidae (leatherjackets) and Mullidae (goat fish) were important fish prey taxa. Commonly identified cephalopods were Octopodidae (octopus), Loliginidae (calamary squid) and Sepiidae (cuttlefish). Comparisons of fish prey diversity determined by pooling faecal DNA from several samples provided a reasonable but incomplete resemblance (55–71%) to the total fish diversity identified across individual diets at each site. Interpretation of diet based on the recovery of prey hard‐parts identified one cephalopod beak (Octopus sp.) and one fish otolith (Parapriacanthus elongatus). The present study highlights the value of DNA‐based analyses and their capabilities to enhance information of trophic interactions.     

A simulation model of how life history strategies mediate pollution effects on fish populations

Pollution effects on fish populations were estimated with a simulation model, using Leslie matrices. Results from changing only first-year survival rate (S_o) have already been published (Schaaf et al. 1987). This paper explores the effects of perturbing both S_o and the adult survival rate (S_i) for 12 spatial-temporal stocks. Most stocks examined are more sensitive to permanent change in S_i than to changes in S_o. The relative importance of these two rates in determining the population growth rate (λ) depends upon the age distribution of the expected lifetime egg production of age i females (V_i). In turn, the vector V_i, as measured by its mean and standard deviation, is shown to vary among geographic or temporal stocks of a single species. Hence, we quantify the impact on population size of destroying a fixed percentage of habitat, relative to where and when it occurs (i.e., relative impact on S_i and S_o). For example, destroying 1% of the Atlantic menhaden habitat would reduce λ by 0.8% and the population by 8.0% in 10 yr, if the impact affected only adults (e.g., offshore in winter). If the 1% habitat destruction all occurred in the estuaries, affecting juveniles as well, λ would be reduced by almost 5%, and in 10 yr drive the population down to 58% of its former equilibrium. We show that knowledge of the mean and variance of the age distribution of V_i permits prediction of relative sensitivity among species to pollution. Within species, this knowledge of V_i permits comparison of the effects of impacting different life stages and at different times and places.     

Performance of the electrochemical ozone sonde OSR

Summary The accuracy of the electrochemical ozone sonde, type OSR, has been estimated by analysing tandem ozone soundings of the balloon-borne electrochemical ozone sonde OSR at the Lindenberg Observatory from May to November 1982. A negative bias, though not significant, has been observed above about 28 km for soundings having high single correction factors. Random errors are at their minimum just above the level of the maximum of ozone partial pressure, and reach their maximum in the troposphere. Except at heights above about 28 km the random error of ozone sondes is a factor 2 to 3 times less than the error of the short Umkehr method. Provided that soundings with too high correction factors are neglected, the ozone sonde OSR has an accuracy comparable to that of other Brewer type sondes.The maximum amount of information on the vertical ozone distribution can be drawn from sonde measurements in the lower stratosphere. A study is underway to improve the sensitivity of the sonde OSR and thus to further enhance its reliability.     

Creating a global warming implementation regime

This paper proposes a global warming implementation regime which addresses the issues of equity, flexibility, cost minimization, and population growth. Previously proposed international policy instruments, such as country by country targets, carbon taxes, and tradable permits, face major difficulties as stand alone proposals. The key element of the regime proposed here is to combine annual tradable permits which are allocated based on population in a fixed year with a small carbon tax ($5–10/tonne) on emissions in excess of permits. Both permits and carbon taxes are applied to national level governments, which in turn would use whatever mix of policies desired to reduce national emissions. It is suggested that the initial number of permits correspond to total global emissions in the base year; over time, the number of permits could be reduced and the tax rate increased if improved scientific knowledge so dictates. By allocating permits based on population the equity concerns of developing countries are addressed, while taxing emissions in excess of permit holdings removes the rigidity of a quota system and limits resource transfers by effectively capping the permit trading price, which is a major concern of industrialized countries. To accommodate the difficulties of countries which have not yet achieved the demographic transition, the permit allocation scheme could be subject to a one-time adjustment after 10–15 years based on some weighting of the initial and then-current populations. The proposed scheme is based on the premise that there is a large potential for reducing emissions in developed countries or limiting emission increases in developing countries, and the intention is to create competition between national level governments in implementing cost-effective emission reduction.     

Rijkswaterstaat's interest in HF radar

In this paper an explanation is given of Rijkswaterstaat's need for hydrological and meteorological information. The present means to gather this information are described together with their limitations. Future developments in the field of HF narrow-beam groundwave radar systems are indicated and some recommendations are given for the design of an operational HF radar system for Rijkswaterstaat (RWS).     

Evaluation of High-Frequency Mean Streamwater Transit-Time Estimates Using Groundwater Age and Dissolved Silica Concentrations in a Small Forested Watershed

Many previous investigations of mean streamwater transit times (MTT) have been limited by an inability to quantify the MTT dynamics. Here, we draw on (1) a linear relation (r ² = 0.97) between groundwater ³H/³He ages and dissolved silica (Si) concentrations, combined with (2) predicted streamwater Si concentrations from a multiple-regression relation (R ² = 0.87) to estimate MTT at 5-min intervals for a 23-year time series of streamflow [water year (WY) 1986 through 2008] at the Panola Mountain Research Watershed, Georgia. The time-based average MTT derived from the 5-min data was ~8.4 ± 2.9 years and the volume-weighted (VW) MTT was ~4.7 years for the study period, reflecting the importance of younger runoff water during high flow. The 5-min MTTs are normally distributed and ranged from 0 to 15 years. Monthly VW MTTs averaged 7.0 ± 3.3 years and ranged from 4 to 6 years during winter and 8–10 years during summer. The annual VW MTTs averaged 5.6 ± 2.0 years and ranged from ~5 years during wet years (2003 and 2005) to >10 years during dry years (2002 and 2008). Stormflows are composed of much younger water than baseflows, and although stormflow only occurs ~17 % of the time, this runoff fraction contributed 39 % of the runoff during the 23-year study period. Combining the 23-year VW MTT (including stormflow) with the annual average baseflow for the period (~212 mm) indicates that active groundwater storage is ~1,000 mm. However, the groundwater storage ranged from 1,040 to 1,950 mm using WY baseflow and WY VW MTT. The approach described herein may be applicable to other watersheds underlain by granitoid bedrock, where weathering is the dominant control on Si concentrations in soils, groundwater, and streamwater.     

Sulfur cycling at the Mid-Atlantic Ridge: A multiple sulfur isotope approach

The role of sulfur in two hydrothermal vent systems, the Logatchev hydrothermal field at 14°45′N/44°58′W and several different vent sites along the southern Mid-Atlantic Ridge (SMAR) between 4°48′S and 9°33′S and between 12°22′W and 13°12′W, is examined by utilizing multiple sulfur isotope and sulfur concentration data. Isotope compositions for sulfide minerals and vent H₂S from different SMAR sites range from + 1.5 to + 8.9‰ in δ³⁴S and from + 0.001 to + 0.051‰ in Δ³³S. These data indicate mixing of mantle sulfur with sulfur from seawater sulfate. Combined δ³⁴S and Δ³³S systematics reveal that vent sulfide from SMAR is characterized by a sulfur contribution from seawater sulfate between 25 and 33%. This higher contribution, compared with EPR sulfide, indicates increased seawater sulfate reduction at MAR, because of a deeper seated magma chamber and longer fluid upflow path length, and points to fundamental differences with respect to subsurface structures and fluid evolution at slow and fast spreading mid-ocean ridges.Additionally, isotope data uncover non-equilibrium isotopic exchange between dissolved sulfide and sulfate in an anhydrite bearing zone below the vent systems at fluid temperatures between 335 and 400 °C. δ³⁴S values between + 0.2 to + 8.8‰ for dissolved and precipitated sulfide from Logatchev point to the same mixing process between mantle sulfur and sulfur from seawater sulfate as at SMAR. δ³⁴S values between ? 24.5 and + 6.5‰ and Δ³³S values between + 0.001 and + 0.125‰ for sulfide-bearing sediments and mafic/ultramafic host rocks from drill cores taken in the region of Logatchev indicate a clear contribution of biogenic sulfides formed via bacterial sulfate reduction. Basalts and basaltic glass from SMAR sites with Δ³³S = ? 0.008‰ reveal lower Δ³³S lower values than suggested on the basis of previously published isotopic measurements of terrestrial materials.We conclude that the combined use of both δ³⁴S and Δ³³S provides a more detailed picture of the sulfur cycling in hydrothermal systems at the Mid-Atlantic Ridge and uncovers systematic differences to hydrothermal sites at different mid-ocean ridge sites. Multiple sulfur isotope measurements allow identification of incomplete isotope exchange in addition to isotope mixing as a second important factor influencing the isotopic composition of dissolved sulfide during fluid upflow. Furthermore, based on Δ³³S we are able to clearly distinguish biogenic from hydrothermal sulfides in sediments even when δ³⁴S were identical.