Advances In Out Door Lysimeter Techniques

Different methods exist for measuring soil water and solute fluxes in and below the root zone and have been critically reviewed. Besides indirect methods (e.g. water balance, tensiometer, time domain reflectometry – TDR, frequency domain reflectometry – FDR, environmental tracer) direct methods (e.g. drainage-type lysimeter, water fluxmeter) have a long tradition and have been successfully used in seepage research. A large weighable out door lysimeter is the best method for obtaining reliable data about seepage water quantity and quality, but it involves significant investment and additional expenses for maintenance. To tackle this problem new methods for the vertical collection of large volume soil monoliths (up to 6 m³) as well as for the horizontal collection (up to 6 m³) have been developed. For the placement of the lysimeter a container lysimeter unit was constructed, which is cheaper than a conventional steel or concrete cellar. Furthermore, the technical design of the newly developed lysimeter types as a weighable gravitation lysimeter, a weighable groundwater lysimeter and a lateral flow lysimeter are presented.     

Untersuchung von Abfällen mit biologischen Testverfahren zur Bewertung der Wassergefährdung

Wastes from three different types of waste treatment facilities were examined with bioassays to determine their hazard potential to waters (→Part I). All examined wastes showed toxic effects and have to be classified as hazardous to waters according to section 19g of the German Federal Water Management Act. The toxicity is probably caused by heavy metals in the leachates, especially copper. An evaluation pattern to classify wastes in the German system of Water Hazard Classes is presented. According to this proposal, a classification of the examined wastes into Water Hazard Class 1 seems to be appropriate. This classification does not describe the hazards resulting from the regular disposal on a landfill or from the utilisation of the treated wastes.     

Using radon-222 as indicator for the evaluation of the efficiency of groundwater remediation by in situ air sparging

A common approach for remediation of groundwater contamination with volatile organic compounds (VOCs) is contaminant stripping by means of in situ air sparging (IAS). For VOC stripping, pressurized air is injected into the contaminated groundwater volume, followed by the extraction of the contaminant-loaded exhaust gas from the vadose soil zone and its immediate on-site treatment. Progress assessment of such remediation measure necessitates information (i) on the spatial range of the IAS influence and (ii) on temporal variations of the IAS efficiency. In the present study it was shown that the naturally occurring noble gas radon can be used as suitable environmental tracer for achieving the related spatial and temporal information. Due to the distinct water/air partitioning behaviour of radon and due to its straightforward on-site detectability, the radon distribution pattern in the groundwater can be used as appropriate measure for assessing the progression of an IAS measure as a function of space and time. The presented paper discusses both the theoretical background of the approach and the results of an IAS treatment accomplished at a VOC contaminated site lasting six months, during which radon was applied as efficiency indicator.     

Measurements of dissolved methylmercury in natural waters using diffusive gradients in thin film (DGT)

A diffusive gradient in thin films (DGT) technique for measuring methylmercury (MeHg) concentrations in natural waters was developed using 3-mercaptopropyl-functionalized silica gel to preconcentrate the methylmercury. The new resin was characterized and calibrated. Methylmercury is efficiently accumulated at a pH range of 3-9. Basic performance tests of the new DGT device confirmed the applicability of Fick's first law for such DGT measurements. The diffusion coefficient of methylmercury in polyacrylamide gel was 5 x 10(-6) cm(2) s(-1). Methylmercury concentrations determined by DGT deployed for different time periods in the field are statistically not different from results obtained through direct measurements. The DGT technique represents therefore an alternative in situ sampling method for methylmercury. The detection limit of the overall method is 1 pg of MeHg, which correspond to approximately 30 pg L(-1) of MeHg in a water sample, when deploying a typical DGT device for 24 hours. Lower MeHg concentrations are measurable using longer deployment times or thinner diffusive gel layers.     

Toxicity of leachate from bottom ash in a road construction

A test road constructed with municipal solid waste incineration (MSWI) bottom ash was monitored over a period of 36 months. Using chemical and toxicological characterisation, the environmental impact of leachates from bottom ash was evaluated and compared with leachates from gravel used as reference. Initial leaching of Cl, Cu, K, Na, NH4-N and TOC from bottom ash was of major concern. However, the quality of the bottom ash leachate approached that of the gravel leachate with time. Leachates from the two materials were compared regarding the concentration of pollutants using multivariate data analyses (MVDA). A standardized luminescent bacteria assay using Vibrio fischeri did not show any toxicity, most likely because saline contamination can mask the toxic response and stimulate luminescence in these marine bacteria. A mung bean assay using Phaseolus aureus revealed that the toxicity of bottom ash leachate collected at the very beginning of the experimental period (October 2001 and May 2002) might be attributed to the following components and their respective concentrations in mg l(-1): Al (34.2-39.2), Cl (2914-16,446), Cu (0.48-1.92), K (197-847), Na (766-4180), NH4-N (1.80-8.47), total-N (12.0-18.5), and TOC (34.0-99.0). The P. aureus assay was judged as a promising environmental tool in assessing the toxicity of bottom ash leachate.     

Removal of hexafluoroarsenate from waters

Arsenic predominantly occurs in natural ground and surface waters as arsenate and arsenite. Other arsenic species can also be present in anthropogenically influenced waters. By means of a newly-developed speciation technique an arsenic compound was identified as hexafluoroarsenate at high concentration (about 0.8mgl(-1) as As) in a lake polluted by waste water from a former crystal glass factory. This compound shows a completely different behavior than common arsenite and arsenate in waters. However, respective literature data were little found regarding its environmental behavior as well as the applicable remediation technologies. Conventional arsenic treatment mechanisms, such as the well-known sorption to iron hydroxides, can not be used to remediate water with this compound. Hence, an effective method to remove hexafluoroarsenate from water was developed using its strong affinity to anion exchangers (strong basic exchangers with quaternary ammonium groups). The sorption can be described by a Langmuir isotherm and first-order kinetics with a half-life of about 10min. Interferences by sulphate and fluoride, present at much higher concentrations in the polluted lake water, might be expected due to the anion exchange mechanism, but were shown to be of minor importance.     

Declines in migrant shorebird populations from a winter‐quarter perspective

Many long‐distance migrating shorebird (i.e., sandpipers, plovers, flamingos, oystercatchers) populations are declining. Although regular shorebird monitoring programs exist worldwide, most estimates of shorebird population trends and sizes are poor or nonexistent. We built a state‐space model to estimate shorebird population trends. Compared with more commonly used methods of trend estimation, state‐space models are more mechanistic, allow for the separation of observation and state process, and can easily accommodate multivariate time series and nonlinear trends. We fitted the model to count data collected from 1990 to 2013 on 18 common shorebirds at the 2 largest coastal wetlands in southern Africa, Sandwich Harbour (a relatively pristine bay) and Walvis Bay (an international harbor), Namibia. Four of the 12 long‐distance migrant species declined since 1990: Ruddy Turnstone (Arenaria interpres), Little Stint (Calidris minuta), Common Ringed Plover (Charadrius hiaticula), and Red Knot (Calidris canutus). Populations of resident species and short‐distance migrants increased or were stable. Similar patterns at a key South African wetland suggest that shorebird populations migrating to southern Africa are declining in line with the global decline, but local conditions in southern Africa's largest wetlands are not contributing to these declines. State‐space models provide estimates of population levels and trends and could be used widely to improve the current state of water bird estimates.     

Comparison of data-based methods for monitoring of air leakages into oxyfuel power plants

Air leakages compromise the CO₂ capture rate and auxiliary power consumption of oxyfuel power plants. Constructive measures can significantly improve the leakage rate in newly built plants. However, the mitigation of increasing leakage rates during the plant lifetime is crucial for high plant efficiency. In this paper, we apply three statistical methods on experimental process data gathered in an air leakage test in Vattenfall's Oxyfuel Pilot Plant in Schwarze Pumpe, Germany. The performance of the methods in identifying increasing leakage rates and localizing the leakage source is investigated. It was found that all three methods can identify and localize even small increases of the leakage rate. A combination of all three methods allows taking advantage of the individual features of each method. Additional installation of CO₂, O₂, H₂O, and SO₂ measurements in the oxidizer can considerably enhance localization performance. Finally, it is shown that the results can be transferred to commercial-scale oxyfuel pilot plants by generating training data with thermodynamic plant models.     

Constraints to implementation of sustainability indicator systems in five Asian cities

Contemporary studies on sustainability indicator systems (SISs) typically focus on the technical advancement of indicator construction, on qualitative impacts of indicator programmes and on impacts on governance, decision-making and sustainability as a social construct. Yet, their implementation so far has rarely been addressed, even though monitoring and the use of indicator results fall far behind the number of SISs developed. This study aims at the identification of requirements for the development of and constraints to the implementation of SISs in five Asian cities of developing countries. Interviews with local key actors are held, and a qualitative content analysis is carried out. Findings include evidence on the degree of indicator implementation in the case study cities, a hexagonal model for the classification of requirements and constraints, as well as general conclusions for barriers to the use of SISs.