A critical analysis of in situ chemical oxidation (ISCO) projects was performed to characterize situations in which ISCO is being implemented, how design and operating parameters are typically employed, and to determine the performance results being achieved. This research involved design of a database, acquisition and review of ISCO project information, population of the database, and analyses of the database using statistical methods. Based on 242 ISCO projects included in the database, ISCO has been used to treat a variety of contaminants; however, chlorinated solvents are by far the most common. ISCO has been implemented at sites with varied subsurface conditions with vertical injection wells and direct push probes being the most common delivery methods. ISCO has met and maintained concentrations below maximum contaminant levels (MCLs), although not at any sites where dense nonaqueous phase liquids (DNAPL) were presumed to be present. Alternative cleanup levels and mass reduction goals have also been attempted, and these less stringent goals are met with greater frequency than MCLs. The use of pilot testing is beneficial in heterogeneous geologic media, but not so in homogeneous media. ISCO projects cost $220,000 on average, and cost on average $94/yd3 of target treatment zone. ISCO costs vary widely based on the size of the treatment zone, the presence of DNAPL, and the oxidant delivery method. No case studies were encountered in which ISCO resulted in permanent reductions to microbial populations or sustained increases in metal concentrations in groundwater at the ISCO-treated site. 相似文献
Slovenia's main military training area at Poček is located in the mountainous Javorniki Watershed. This is a karstic district
without surface drainage or river valleys. The typical landscapes are conical hills and plateaus with many dolines. The lithology,
tectonic structure and speleological data indicate a typical karst aquifer with underground water moving rapidly through fissures
and conduits. Little attenuation occurs in such conditions and as a result there is a high risk of pollution. Tracer tests
have shown that a significant proportion of the water recharging the Malni and Vipava springs comes from the vicinity of the
military training area. As a result any polluting activities taking place within the military training area are likely to
affect the two springs. This is a very serious matter as the springs have been developed to provide the water supply for the
population of south-western Slovenia.
Received: 20 April 1998 · Accepted: 24 August 1998 相似文献
In Kunming area (6.8 mio population), two big interventions are in progress: construction of a new airport, the 23 km2 area of which will extend across karst terrain northeast of the city, and extensive uptake of water from karst aquifers for drinking and agricultural use. In the study, an interdisciplinary approach was utilized to demonstrate the need for holistic karstology studies prior to performing extensive interferences in the karst environment. This study included survey of surface karst features and microscopic analyses of rock samples in the area of the new airport location, accompanied by hydrogeological studies and microbiological analyses of two karst drinking water sources in its vicinity (Qinglongdong, Huanglongdong). Results showed the specific characteristics of the subsoil stone forest that indicated a high level of karstification. The direction and characteristics of groundwater flow from the sinking Qiaotou Stream at the margin of the new airport area toward the Huanglongdong Spring were defined with a single tracer test. Additional information about hydrogeological characteristics of the karst aquifer was obtained by individual measurements of physical and chemical parameters of the springs and sinking stream. Selected chemical and bacteriological parameters showed substantial pollution of both springs due to various types of human activities in the catchments. The results of the study pointed to the necessity of taking immediate measures for the springs’ protection and showed the importance of interdisciplinary research when planning anthropogenic activities in the karst. 相似文献
SPOT satellites have been imaging Earth's surface since SPOT 1 was launched in 1986. It is argued that absolute atmospheric correction is a prerequisite for quantitative remote sensing. Areas where land cover changes are occurring rapidly are also often areas most lacking in situ data which would allow full use of radiative transfer models for reflectance factor retrieval (RFR). Consequently, this study details the proposed historical empirical line method (HELM) for RFR from multi-temporal SPOT imagery. HELM is designed for use in landscape level studies in circumstances where no detailed overpass concurrent atmospheric or meteorological data are available, but where there is field access to the research site(s) and a goniometer or spectrometer is available. SPOT data are complicated by the ±27° off-nadir cross track viewing. Calibration to nadir only surface reflectance factor (ρs) is denoted as HELM-1, whilst calibration to ρs modelling imagery illumination and view geometries is termed HELM-2. Comparisons of field measured ρs with those derived from HELM corrected SPOT imagery, covering Helsinki, Finland, and Taita Hills, Kenya, indicated HELM-1 RFR absolute accuracy was ±0.02ρs in the visible and near infrared (VIS/NIR) bands and ±0.03ρs in the shortwave infrared (SWIR), whilst HELM-2 performance was ±0.03ρs in the VIS/NIR and ±0.04ρs in the SWIR. This represented band specific relative errors of 10–15%. HELM-1 and HELM-2 RFR were significantly better than at-satellite reflectance (ρSAT), indicating HELM was effective in reducing atmospheric effects. However, neither HELM approach reduced variability in mean ρs between multi-temporal images, compared to ρSAT. HELM-1 calibration error is dependent on surface characteristics and scene illumination and view geometry. Based on multiangular ρs measurements of vegetation-free ground targets, calibration error was negligible in the forward scattering direction, even at maximum off-nadir view. However, error exceeds 0.02ρs where off-nadir viewing was ≥20° in the backscattering direction within ±55° azimuth of the principal plane. Overall, HELM-1 results were commensurate with an identified VIS/NIR 0.02ρs accuracy benchmark. HELM thus increases applicability of SPOT data to quantitative remote sensing studies. 相似文献
Bromine was historically termed a cyclic salt in terrestrial freshwater environments due to its perceived conservative cycling between the oceans and the continents. This basic assumption has been challenged recently, with evidence that bromine is involved in dynamic chemical cycles in soils and freshwaters. We present here a study on dissolved bromine species (bromide, organically bound bromine, DOBr) concentrations and fluxes as well as sediment trap bromine levels and fluxes in Lake Constance, a large lake in southern Germany. Water samples were obtained from all major and some minor inflows and outflows over one year, where-after dissolved bromine species were measured by a combination of ICP-MS and ion chromatography coupled to an ICP-MS (IC-ICP-MS). Sediment traps were deployed at two locations for two years with Br, Ti and Zr levels being measured by μ-XRF.190 t yr−1 of total dissolved bromine (TDBr) was delivered to the lake via 14 rivers and precipitation, with the rivers Alpenrhein (84 t TDBr yr−1) and the Schussen (50 t TDBr yr−1) providing the largest sources. The estimated particulate bromine flux contributed an extra 24-26 t Br yr−1. In comparison, only 40 t TDBr yr−1 was deposited to the lake’s catchment by precipitation, and thus ∼80% of the riverine TDBr flux came from soils and rocks. Bromide was the dominant species accounting for, on average, 78% of TDBr concentrations and 93% of TDBr flux to the lake. Despite some high concentrations in the smaller lowland rivers, DOBr was only a minor component of the total riverine bromine flux (∼12 t yr−1, 7%), most of which came from the rivers Schussen, Bregenzer Ach and Argen. In contrast, most of the bromine in the sediment traps was bound to organic matter, and showed a clear seasonal pattern in concentrations, with a maximum in winter and minimum in summer. The summer minimum is thought to be due to dilution of a high Br autochthonous component by low bromine mineral and organic material from the catchment, which is supported by Ti, Zr and Br/Corg data. In the lake bromine was irreversibly lost to the sediments, with best flux estimates based on mass-balance and sediment trap data of +50-90 μg Br m−2 d−1. Overall, it appears that bromine is not simply a cyclic salt in the case of Lake Constance, with a clear geological component and dynamic lacustrine biogeochemistry. 相似文献
We determined the associations between Eurasian perch Perca fluviatilis, invertebrates, and common goldeneye Bucephala clangula in boreal lakes. Our aim was to test the hypothesis that perch play a controlling role in small, oligotrophic, acidic, and
poorly vegetated boreal lakes, affecting both invertebrate numbers and community structure. In addition, we predicted that
perch impact lake usage by goldeneye. In the observational part of our study, we first explored the association between perch,
invertebrates and goldeneye (pairs and broods per shore km) in 18 boreal, poorly vegetated lakes. Perch densities were associated
negatively with invertebrate abundance and lake usage by goldeneye broods. In the experimental part in three fish-free lakes,
we found that upon successful perch introductions, the number and biomass of invertebrates, the proportion of large dytiscids,
and lake usage by goldeneye broods significantly decreased. We conclude that perch apparently plays a key role as a predator
of invertebrates in boreal lakes with few aquatic macrophytes. It is evident that perch can strongly affect their prey populations
and communities, and this predation may have an indirect effect on species, e.g. goldeneye, that consume the same prey. 相似文献
Ultramafic rocks occur within polydeformed high grade metasedimentary rocks throughout the Vammala Nickel Belt (Fennoscandian Shield) and have been subdivided into cumulate-textured intrusive bodies and high-Mg (picritic) eruptive units.
The crystallisation sequence olivine(+cotectic chromite)-orthopyroxene-clinopyroxene-amphibole, the decreased stability field of olivine and fractionation of relatively Al-rich pyroxenes and chromite all suggest that the cumulate-textured intrusions crystallised from a relatively hydrous parental magma at moderate crustal pressures. The parental magma was enriched in Th, LILE and LREE, being similar to modern tholeiitic arc basalts. Trace element ratios suggest that Svecofennian turbidites were the ultimate source of this enriched component. Although the mechanism of contamination is inconsistent with simultaneous assimilation and fractional crystallisation in situ, this can be explained by a model in which magma flowed through subvertical conduits and assimilated adjacent crust.
Characteristics of metamorphism, deformation and subsolidus equilibration and age determinations all suggest that emplacement of cumulate-textured bodies coincided with the peak of ongoing regional metamorphism and deformation. The cumulate-textured intrusions are interpreted as representing middle crustal expressions of early Proterozoic Svecofennian arc magmatism. This model also predicts that the same magmatism resulted in the emplacement of more evolved arc plutonic complexes at higher crustal levels (that have since been eroded), and the formation of large ultramafic cumulate complexes in the lower crust and at the crust-mantle boundary region, and may thus assist in interpreting deep seismic and gravimetric anomalies within Svecofennian domain.
In contrast, the metapicritic supracrustal rocks have trace element signatures similar to transitional MORB, and cannot represent magmas complementary to the cumulate-textured intrusions. The metapicrites represent supracrustal formations which are clearly older than the synorogenic cumulate-textured intrusions, and their spatial association is coincidental only. 相似文献
In Finland, community water supply has increasingly relied on natural groundwater and artificially recharged groundwater as the raw water source. Several managed aquifer recharge (MAR) projects have been co-created with involved parties and have proceeded well, while some cases have raised considerable resistance among the stakeholders. It seems that success or failure in MAR cooperation is related to management cultures and the ways in which various interests are taken into account, from the very beginning and throughout the process. Empirically, this paper builds on comparison between two conflictual case studies in Finland: one in the Tampere region and the other in the Turku region. The study analyses the major constraints of these projects through the lens of collaborative rationality, also drawing upon discourse analysis and negotiation theory. The material is gathered through thematic interviews of stakeholders, newspaper articles and a stakeholder workshop. The results indicate that conventional management approaches, drawing from expert-based instrumental rationality, were insufficient in both cases. The collaborative rationality framework suggests that legitimacy for the groundwater projects should be gained through joint knowledge production and inclusive multiparty interaction for creating options for collaboration. Both cases lacked the tools and know-how for authentic dialogue and collaboration. The emerging paradigm emphasizes more collaborative approaches for natural resources management and urban planning. While MAR projects operate inside these areas and are highly complex in nature, it is essential to embrace the emerging paradigm in order to promote MAR systems along with their huge potential.
