Estimation of Degradation Rates by Satisfying Mass Balance at the Inlet

Using a steady-state mass conservative solute transport analytical solution that is based on the third-type (or flux-type or Cauchy) source condition, a method is developed to estimate the degradation parameters of solutes in groundwater. Then, the inadequacy of the methods based on the first-type source-based analytical solute transport solution is presented both theoretically and through an example. It is shown that the third-type source analytical solution exactly satisfies the mass balance constraint at the inlet location. It is also shown that the first-type source (or constant source concentration or Dirichlet) solution fails to satisfy the mass balance constraint at the inlet location and the degree of the failure depends on the value of the degradation as well as the flow and solute transport parameters. The error in the first-type source solution is determined with dimensionless parameters by comparing its results with the third-type source solution. Methods for estimating the degradation parameter values that are based on the first-type steady-state solute transport solution may significantly overestimate the degradation parameter values depending on the values of flow and solute transport parameters. It is recommended that the third-type source solution be used in estimating degradation parameters using measured concentrations instead of the first-type source solution.     

Pathogens in Water: Value and Limits of Correlation with Microbial Indicators

This article discusses the value and limitations of using microbial indicators to predict occurrence of enteric pathogens in water. Raw or treated sewage is a primary source of fecal contamination of the receiving surface water or groundwater; hence, understanding the relationship between pathogens and indicators in sewage is an important step in understanding the correlation in receiving waters. This article presents three different datasets representing different concentrations of pathogens and microbial indicators: sewage containing high concentrations of pathogens and indicators, surface water with variable concentrations, and groundwater with low concentrations. In sewage, even with very high levels of microorganisms, no mathematical correlation can predict the type or concentration of any pathogen. After discharge in the environment, direct correlation becomes biologically improbable as dilution, transport, and different inactivation rates occur in various environments. In surface waters, advanced statistical methods such as logistic regression have provided some level of predictability of the occurrence of pathogens but not specific counts. In groundwater, the continuous absence of indicators indicates an improbable occurrence of pathogen. In contrast, when these indicators are detected, pathogen occurrence probability increases significantly. In groundwater, given the nature and dissemination pattern of pathogenic microorganisms, a direct correlation with fecal microbial indicators is not observed and should not be expected. However, the indicators are still useful as a measure of risk. In summary, many pathogens of public health importance do not behave like fecal microbial indicators, and there is still no absolute indicator of their presence, only a probability of their co‐occurrence.     

Microbial Degradation of Tar Oil Compounds under Different Redox Conditions

The microbial transformation of typical tar oil compounds such as acridine, benzo(b)thiophene, dibenzofuran, indane, and indene under different redox conditions was investigated in microcosm studies. Under aerobic conditions the inherent contamination in polluted soil as well as the added N‐, S‐, O‐ heterocyclic and homocyclic compounds were transformed predominantly apart from thiophene. 1‐Indanone was detected by RP‐HPLC‐DAD and GC‐MS as an intermediate metabolite from indane and indene. Under nitrate and sulfate reducing conditions indane, benzo(b)thiophene, and dibenzofuran were transformed in assays with the polluted soil samples from well B 65 and B 66 within 426 days, whereas they were persistent in assays with the highly polluted soil B 67. All heterocyclic and homocyclic compounds added to the non‐contaminated soil from well B 85 were not degraded under nitrate and sulfate reducing conditions, too. The results indicate that for the decision, wether natural attenuation can be implemented in the remediation of contaminated site, in addition to BTEX and PAHs especially the fate of further tar oil compounds in anoxic aquifers has to be considered.     

A Borehole Test for Chlorinated Solvent Diffusion and Degradation Rates in Sedimentary Rock

We present a new field measurement and numerical interpretation method (combined termed “test”) to parameterize the diffusion of trichloroethene (TCE) and its biodegradation products (DPs) from the matrix of sedimentary rock. The method uses a dual-packer system to interrogate a low-permeability section of the rock matrix adjacent to a previously contaminated borehole and uses the borehole monitoring history to establish the pretest condition. TCE and its DPs are removed from the groundwater between the packers at the onset of the testing. The parameters estimated by fitting a radial diffusion model to the concentration history and borehole concentration data, also termed back diffusion, are the tortuosity factor and sorption coefficients of TCE and DPs in the rock matrix and the TCE and DP biodegradation rate coefficients in the borehole. We demonstrate the equipment design and the interpretive method using a borehole accessing the gray mudstone at a TCE contaminated site in the Newark Basin. In this test, both nonreactive (bromide) and reactive (trichlorofluoroethene) tracers are used to constrain the estimated parameters; however, the bromide tracer was not needed to estimate the parameters in this test. The parameters estimated from the field test are consistent with values measured independently in laboratory experiments using field samples of similar lithology. From the interpretation, we compute the TCE and DP concentration distributions in the rock matrix prior to the test to illustrate how the results can be used to enhance understanding of contaminant distribution in the rock matrix.     

Hydrogeology,Chemical and Microbial Activity Measurement Through Deep Permafrost

Little is known about hydrogeochemical conditions beneath thick permafrost, particularly in fractured crystalline rock, due to difficulty in accessing this environment. The purpose of this investigation was to develop methods to obtain physical, chemical, and microbial information about the subpermafrost environment from a surface‐drilled borehole. Using a U‐tube, gas and water samples were collected, along with temperature, pressure, and hydraulic conductivity measurements, 420 m below ground surface, within a 535 m long, angled borehole at High Lake, Nunavut, Canada, in an area with 460‐m‐thick permafrost. Piezometric head was well above the base of the permafrost, near land surface. Initial water samples were contaminated with drill fluid, with later samples <40% drill fluid. The salinity of the non‐drill fluid component was <20,000 mg/L, had a Ca/Na ratio above 1, with δ¹⁸O values ～5‰ lower than the local surface water. The fluid isotopic composition was affected by the permafrost‐formation process. Nonbacteriogenic CH₄ was present and the sample location was within methane hydrate stability field. Sampling lines froze before uncontaminated samples from the subpermafrost environment could be obtained, yet the available time to obtain water samples was extended compared to previous studies. Temperature measurements collected from a distributed temperature sensor indicated that this issue can be overcome easily in the future. The lack of methanogenic CH₄ is consistent with the high sulfate concentrations observed in cores. The combined surface‐drilled borehole/U‐tube approach can provide a large amount of physical, chemical, and microbial data from the subpermafrost environment with few, controllable, sources of contamination.     

Push‐Pull Tests for Estimating RDX and TNT Degradation Rates in Groundwater

In situ bioremediation is being considered to optimize an existing pump‐and‐treat remedy for treatment of explosives‐contaminated groundwater at the Umatilla Chemical Depot. Push‐pull tests were conducted using a phased approach to measure in situ hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) and 2,4,6‐trinitrotoluene (TNT) degradation rates associated with various carbon substrates. Phase I included short‐duration transport tests conducted in each well to determine dilution rates and retardation factors for RDX and TNT. Phase II included aquifer “feedings” conducted by injecting 150 gallons of treated site groundwater amended with ethanol, corn syrup, lactose or emulsified oil (concentrations 10, 25 and 27 mM, respectively; 12% by volume for emulsified oil). Wells received up to 6 substrate “feedings” over the course of 3 months followed by monitoring dissolved oxygen, nitrate, Fe(II), and sulfate to gauge in situ redox conditions as indicators of anaerobic microbial activity. Phase III included push‐pull tests conducted by injecting 150 gallons of site groundwater amended with approximately 1000 µg/L RDX, 350 µg/L TNT, carbon substrate and a conservative tracer, followed by sampling over 8 d. Corn syrup resulted in the best RDX removal (82% on average) and the largest RDX degradation rate coefficient (1.4 ± 1.1 d^?1). Emulsified oil resulted in the best TNT removal (99%) and largest TNT degradation rate coefficient (5.7 × 10^?2 d^?1). These results will be used to simulate full‐scale in situ bioremediation scenarios at Umatilla and will support a go/no‐go decision to initiate full‐scale bioremediation remedy optimization.     

Microbial Dynamics During and After In Situ Chemical Oxidation of Chlorinated Solvents

In situ chemical oxidation (ISCO) followed by a bioremediation step is increasingly being considered as an effective biphasic technology. Information on the impact of chemical oxidants on organohalide respiring bacteria (OHRB), however, is largely lacking. Therefore, we used quantitative PCR (qPCR) to monitor the abundance of OHRB (Dehalococcoides mccartyi, Dehalobacter, Geobacter, and Desulfitobacterium) and reductive dehalogenase genes (rdh; tceA, vcrA, and bvcA) at a field location contaminated with chlorinated solvents prior to and following treatment with sodium persulfate. Natural attenuation of the contaminants tetrachloroethene (PCE) and trichloroethene (TCE) observed prior to ISCO was confirmed by the distribution of OHRB and rdh genes. In wells impacted by persulfate treatment, a 1 to 3 order of magnitude reduction in the abundances of OHRB and complete absence of rdh genes was observed 21 days after ISCO. Groundwater acidification (pH<3) and increase in the oxidation reduction potential (>500 mV) due to persulfate treatment were significant and contributed to disruption of the microbial community. In wells only mildly impacted by persulfate, a slight stimulation of the microbial community was observed, with more than 1 order of magnitude increase in the abundance of Geobacter and Desulfitobacterium 36 days after ISCO. After six months, regeneration of the OHRB community occurred, however, neither D. mccartyi nor any rdh genes were observed, indicating extended disruption of biological natural attenuation (NA) capacity following persulfate treatment. For full restoration of biological NA activity, additional time may prove sufficient; otherwise addition electron donor amendment or bioaugmentation may be required.     

Quantitation of Nonextractable Anthropogenic Quantitation of Nonextractable Anthropogenic Sediments after Chemical Degradation

Four highly contaminated sediment samples obtained from three sampling locations of the Teltow Canal, Berlin, were investigated by quantitation of extractable and nonextractable organic contaminants. The selection of the anthropogenic contaminants (including chlorinated and brominated naphthalenes, 2, 4, 6‐tribromoaniline, phthalates, tri‐n‐butylphosphate, 2, 2, 4‐trimethyl‐1, 3‐pentanediol diisobutyrate, bisphenol A, butylated nitrophenols, 4‐nitrobenzoic acid, galaxolide, and tonalide) based on the results of extended GC‐MS screening analyses applied to the extracts of the sediment samples as well as to the extracts derived from selective chemical degradation procedures. In detail, alkaline hydrolyses, BBr₃‐treatment and RuO₄‐oxidation were applied to the pre‐extracted sediment samples in both a separate and a sequential mode.     

小震作用下钢筋混凝土框架结构失效相关性分析

本文通过大量的Ｍｏｎｔｅ Ｃａｒｌｏ随机模拟分析,指出在小震下ＲＣ框架结构截面约束的失效统计相关性服从于“失效独立性假设”,并通过算例分析和相关系数比较验证了这一结论。     

Correlation of cyclic preloading with the liquefaction resistance

The compactivity of sand due to cyclic loading with a high number (N>10³) of small cycles (ε^ampl≤10⁻³) cannot be described by void ratio and stress alone. It depends strongly on the soil fabric usually described as ‘cyclic preloading’. The cyclic preloading cannot be measured directly in situ but correlates well with the liquefaction resistance. This paper demonstrates this correlation on the basis of laboratory tests. Practical applications can be derived from this work.     

On the Correlation of Earthquakes with Geomagnetic Storms

Izvestiya, Physics of the Solid Earth - Abstract—In response to the kind invitation of the Editorial Board of the journal “Izvestiya, Physics of the Solid Earth” to take part in...     

A Type-Curve Method for the Analysis of Pumping Tests with Piecewise-Linear Pumping Rates

Aquifer hydraulic parameters are commonly inferred from constant-rate pumping tests, while variable pumping rates are frequently encountered in actual field conditions. In this study, we propose a generally applicable dimensionless form of the analytical solution for variable-rate pumping tests in confined aquifers. In particular, we adopt a piecewise-linear fitting of variable pumping rates and propose a new type-curve method for estimating the hydraulic conductivity (K ) and specific storage (S_s ) of the investigated confined aquifer. For each test, a series of type curves, which depend on the variable pumping rates, the location of observation wells and the introduced first dimensionless inflection time, need to be provided for matching the observed drawdown data on a log-log graph. We first demonstrate the applicability and robustness of this method through a synthetic pumping test. Subsequently, we apply this method to analyze drawdown data from four pumping tests conducted within a multilayered aquifer/aquitard system in Wuxi city, Jiangsu Province, China. The parameter estimates are then compared with those reported by PEST. The K and S_s values estimated by the new type-curve method are found to be quite close to PEST-based estimates. Parameter estimation results demonstrate the difference in K and S_s values between observation wells. The difference could be attributed to the spatial heterogeneity in K and S_s . A future research topic may focus on the characterization of K and S_s heterogeneity with the currently available drawdown data from variable-rate pumping tests.     

Biodegradability of the Anti-tumour Agents 5-Fluorouracil,Cytarabine, and Gemcitabine: Impact of the Chemical Structure and Synergistic Toxicity with Hospital Effluent

Most anti-tumour agents are known to be carcinogenic, mutagenic, teratogenic, embryotoxic or fetotoxic. Only little is known about the environmental impact of pharmaceuticals. Unmetabolized active substances are excreted and will show up in municipal wastewater. Therefore, we examined the biodegradability of the widely used anti-tumour agent 5-fluorouracil (5-FU), also as an example for assessing the impact of hospital effluent on the biodegradation of a test compound. The biodegradability of the structurally similar anti-tumour agents cytarabine and gemcitabine was also examined. Test systems used were the closed bottle test (OECD 301 D) and the modified Zahn-Wellens test (OECD 302 B). 5-FU was not biodegradable in the closed bottle test (CBT) nor in the Zahn-Wellens test (ZWT). At the highest concentration of 5-FU, with hospital effluent an inhibition of the degradation of substances present in hospital effluent was observed, probably as a result of a synergistic effect by 5-FU with antibiotics present in hospital sewage. Gemcitabine was biodegraded 42% in the CBT. The prolongation of the test period to 40 days only improved the result to 45%. In the ZWT, the biodegradation of gemcitabine was 50%. Cytarabine was partially biodegraded in the CBT (50%), but only after an adaptation period of 20 days. After a test prolongation to 40 days, the degree of biodegradation was 80%. In the ZWT, the biodegradability was > 95% after only a few days.     

Rates of erosion of till in the nearshore zone

Measurements of vertical erosion of till in water depths ranging from 1.1 m to 5 m have been obtained using a modified micro-erosion meter. Measurements in this environment are hindered by poor underwater visibility and losses due to high erosion rates and ice action. There is considerable spatial and temporal variability in the erosion rates measured but average values show a general increase from 11 mm y^?1 in 6 m of water to about 35 mm y^?1 in 2.3 m of water and even higher rates closer to shore. The measured values in shallow water are in good agreement with long-term rates extrapolated from shoreline recession. It is suggested that erosion occurs through abrasion and fluid stressing, and that these mechanisms are aided by softening of the upper surface of the till, possibly through cyclic ‘fatigue failure’.