Search

Landfills have been identified as a significant concern to the surrounding surface and groundwater ecosystem because of the discharge of leachate. To tackle the uncertain localization of the contamination plume due to low sampling densities, a combination of hydrochemical analysis and induced polarization survey (IP) is employed to characterize the leachate in a municipal landfill. The polarization effect in the contaminated area is significantly higher than expected for landfill sites, but relatively low chargeability zones (100 mV/V) indicating the distribution of leachate are observed inside high conductivity (600 mS/m) areas. With reliable geophysical results confirmed by similar formation factors from both field and laboratory data, the abnormal high polarization effect is influenced by installed steel sheet piles next to the survey cable. In addition, we successfully identify linear relationship between the geophysical responses and dominant inorganic conservative compounds (Cl

Previous experimental studies have identified specific foods or nutrients are capable of mitigating adverse effects induced by air pollution. However, whether the dietary pattern can modify the associations between long-term particulate matter (PM) and increasing blood pressure (BP) among adults has not yet been assessed. We assessed whether the dietary pattern and various foods modify the associations between long-term exposure to PM (PM 1 , PM 2.5 , and PM 10 ), hypertensive BP (BP≥140/90 mm Hg, HBP), and BP in Chinese adults. This study included 61 081 participants from China Multi-Ethnic Cohort. PM was assessed through satellite-based random forest approaches. Outcomes were analyzed with logistic regression models and linear regression models. The dietary approaches to stop hypertension (DASH) diet was calculated for each participant. This study founds long-term exposure to PM was associated with HBP, systolic BP, and pulse pressure. The DASH diet modified the associations between PM, HBP, and some BP components. For each 10 μg/m 3 increase in PM 1 , PM 2.5 , and PM 10 , the participants with the lowest quintile of DASH score had HBP risks with odds ratios (95% CI) of 1.196 (1.084–1.319), 1.145 (1.09–1.202), and 1.080 (1.045–1.117), whereas those with the highest quintile of DASH score had lower HBP risks with odds ratios (95% CI) of 1.063 (0.953–1.185), 1.074 (1.017–1.133), and 1.038 (1.000–1.077). Consuming more fresh fruits, vegetables, dairy, and whole grains would reduce the risk of raised BP caused by PM. In conclusion, the DASH diet rich in antioxidant compounds may be a wide-reaching intervention to reduce the deleterious impact of PM.

Light non-aqueous phase liquids (LNAPLs) are commonly used in industrial processes, and they are well known for their potential to contaminate groundwater and their toxic effects on ecosystems. The adequate delineation of contaminant plume distribution is critical for the effective remediation of contaminated sites and aquifers. Electrical resistivity tomography (ERT) surveys on LNAPL contaminated soils have shown great potential in this regard. In this study in China, six ERT profiles were conducted at a former perfumery plant with a benzene and ethylbenzene spill history to evaluate whether ERT could be used to delineate the distribution of the LNAPL plume beneath the plant. Based on the survey results, the electrical resistivity was consistent with borehole sampling results, where high resistivity corresponded to increased LNAPL concentration. A linear relationship was built between resistivity and contaminant concentration, with a threshold value of 18 Ω·m used to identify contaminated areas. It was possible to construct a detailed three-dimensional characterization of the LNAPL distribution. In addition, four local sites were excavated to verify the results of the ERT profiles. The contamination sources were further categorized into four types that were considered useful for the selection of remediation strategies. In conclusion, ERT was an effective non-invasive technique for delineating LNAPL plume distribution at a high resolution.

Background China has the largest elderly population in the world; little attention has been paid to the mental health of elderly in areas of extreme poverty. This is the first study to investigate the mental health of the rural elderly in poverty state counties in Chongqing and was part of the Chongqing 2018 health literacy promotion project. Methods In 2019, a cross-sectional study was conducted to investigate the mental health status of the rural elderly in fourteen poverty state counties of Chongqing, in which a total of 1400 elderly aged ≥ 65 years were interviewed, where mental health status was measured by the ten-item Kessler10 (K10) scale. Ordered multivariate logistic regression was performed to evaluate the influencing factors related to mental health of the elderly in these areas. Results The average score of K10 in 14 poverty state counties was 17.40 ± 6.31, 47.6% was labeled as good, 30.2% was moderate, 17.0% was poor, and lastly 5.1% was bad, and the mental health status of the elderly in the northeastern wing of Chongqing was better than the one in the southeastern wing of Chongqing. A worse self-rated health was the risk factor for mental health both in the northeastern and southeastern wings of Chongqing (all P < 0.001). Lower education level (OR (95% CI) = 1.45 (1.12–1.87), P = 0.004) was a risk factor in the northeastern wing, whereas older age (OR (95% CI) = 1.33 (1.13–1.56), P = 0.001) was a risk factors in the southeastern wing. Conclusions The results showed that mental health of the elderly in poverty state counties was poor, especially in the southeastern wing of Chongqing. Particular attention needs to be paid to the males who were less educated, older, and single; female with lower annual per capital income; and especially the elderly with poor self-rated health.

An aerobic Gram-stain-negative, curved rod-shaped and non-spore-forming bacterial strain (NBU2194T) was isolated from seawater collected in an intertidal zone in Ningbo, Zhejiang Province, PR China. It was motile though a single polar flagellum and grew at 20–42 °C (optimum, 30 °C), in 0–2.0 % NaCl (0 %, w/v) and at pH 5.0–9.0 (pH 6.0–7.0). The sole respiratory quinone was ubiquinone-8. The major cellular fatty acids were C16 : 0, C16 : 1 ω7c and/or C16 : 1 ω6c. The polar lipids contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, one unidentified phospholipid and two unidentified aminophosphoglycolipids. A phylogenetic analysis based on 16S rRNA gene sequences and 65 genomic core genes showed that strain NBU2194T formed a distinct lineage in the family Alteromonadaceae . The genome of strain NBU2194T was 4 913 533 bp with a DNA G+C content of 43.9 mol% and coded 3895 genes, 12 rRNA genes and 47 tRNA genes. The average nucleotide identity, amino acid identity and digital DNA–DNA hybridization values between strain NBU2194T and related species of Alteromonadaceae were below the threshold limit for prokaryotic species delineation. NBU2194T could be distinguished from other genera in the family Alteromonadaceae based on phenotypic, chemotaxonomic and genomic characteristics. On the basis of the polyphasic taxonomic evidence collected in this study, strain NBU2194T is considered to represent a novel genus and species in the family Alteromonadaceae , for which the name Paraneptunicella aestuarii is proposed. The type strain is NBU2194T (=KCTC 82442T=GDMCC 1.2217T).

(1) Introduction and objective: Surgical resection plays an important role in the multidisciplinary treatment of lung cancer patients with brain metastases (BMs). Precisely distinguishing the tumor border intraoperatively to improve and maximize the extent of resection (EOR) without causing permanent neurological defects is crucial but still challenging. Therefore, we introduced our experience of utilizing sodium fluorescein (SF) in microneurosurgery of BMs from lung cancer. This study aims to evaluate whether the use of SF-guided surgery has a positive impact on postoperative outcomes. (2) Materials and methods: A retrospective study was performed to collect data on a consecutive case series of patients with BMs from lung cancer who underwent surgical resection from January 2020 to December 2021 at the Department of Neuro-Oncology, Chongqing University Cancer Hospital. A total of 52 patients were enrolled, of which 23 received SF-guided surgery and 29 did not. EOR was assessed pre- and postoperatively on T1 contrast-enhanced MRI. Clinical and epidemiological data as well as follow-up were gathered and analyzed. (3) Results: Compared with the non-SF-guided group, the SF-guided group revealed a significantly better EOR (87.0% vs. 62.1%) and a lower incidence of local recurrence (8.7% vs. 34.5%). Survival benefits were seen in patients with NSCLC, patients who were undergoing SF-guided surgery, and patients receiving postoperative systemic therapy. (4) Conclusions: SF-guiding under the YELLOW 560 nm filter is a safe and feasible tool for improving the EOR in patients with BMs from lung cancer, leading to better local recurrence control and prolonged survival.

Waste disposal sites are a serious concern due to their potential contamination threat. Site characterizations are the basis for contamination remediation, among which borehole-based methods are time-consuming. This study aims to utilize time-domain induced polarization (TDIP) to constrain groundwater and soil organic contamination. Fourteen TDIP profiles were arranged using three acquisition methods at a disposal site contaminated with benzene. A data quality analysis was first conducted to overcome poor signals in high-salinity groundwater conditions. The TDIP results show that solid waste can be classified into two distinct types based on chargeability. The results of induced polarization measurements and X-ray fluorescence analysis proved the presence of metal substances causing high chargeability. The waste with metals was the benzene contamination source. Finally, we propose a procedure for the integration of geophysical and geochemical methods to delineate contaminated areas. A new roll-along survey protocol was developed to meet the needs of long-profile surveys of contaminated shallow groundwater and soil sites.

Internal water storage within trees can be a critical reservoir that helps trees overcome both short- and long-duration environmental stresses. We monitored changes in internal tree water storage in a ponderosa pine using moisture probes, a dendrometer, and time-lapse electrical resistivity imaging (ERI) to investigate how patterns of in-tree water storage are affected by changes in sapflow rates, soil moisture, and meteorologic factors. ERI measurements are influenced by changes in moisture, temperature, solute concentration, and material properties; thus, to evaluate changes in moisture based on ERI, the first three factors must be considered. Measurements of xylem fluid electrical conductivity were constant in the early growing season, while inverted sapwood electrical conductivity steadily increased, suggesting that increases in electrical conductivity of the sapwood did not result from an increase xylem fluid electrical conductivity. Seasonal increases in stem electrical conductivity corresponded with seasonal increases in trunk diameter, suggesting that increased electrical conductivity may result from new growth. Changes in diel amplitudes of inverted sapwood electrical conductivity, which correspond to diel changes in sapwood moisture, indicated that tree water storage use was greatest ~4-5 days after storm events, when sapwood inverted electrical conductivity measurements suggest internal stores were high. A decrease in diel amplitudes of inverted sapwood electrical conductivity during dry periods, suggest that the ponderosa pine relied on internal water storage to supplement transpiration, but as drought conditions progressed, tree water storage contributions to transpiration decreased. Wavelet analyses indicated that lag times between inverted sapwood electrical conductivity and sapflow increased after storm events, suggesting that as soils dried reliance on internal water storage increased and the time required to refill daily deficits in internal water storage increased. Lag times peaked when soil moisture returned to pre-storm event levels and then decreased as drought progressed. Short time lags between sapflow and inverted sapwood electrical conductivity corresponded with dry conditions, when ponderosa pine are known to reduce stomatal conductance to avoid xylem cavitation. Time-lapse ERI- and wavelet-analysis results highlighted the important role internal tree water storage plays in supporting transpiration throughout the course of a day, and during periods of declining subsurface moisture.

SUMMARY4-D electrical resistivity tomography (ERT), an important geophysical method, is widely used to observe dynamic processes within static subsurface structures. However, because data acquisition and inversion consume large amounts of time, rapid changes that occur in the medium during a single acquisition cycle are difficult to detect in a timely manner via 4-D inversion. To address this issue, a scheme is proposed in this paper for restructuring continuously measured data sets and performing GPU-parallelized inversion. In this scheme, multiple reference time points are selected in an acquisition cycle, which allows all of the acquired data to be sequentially utilized in a 4-D inversion. In addition, the response of the 4-D inversion to changes in the medium has been enhanced by increasing the weight of new data being added dynamically to the inversion process. To improve the reliability of the inversion, our scheme uses actively varied time-regularization coefficients, which are adjusted according to the range of the changes in model resistivity; this range is predicted by taking the ratio between the independent inversion of the current data set and historical 4-D inversion model. Numerical simulations and experiments show that this new 4-D inversion method is able to locate and depict rapid changes in medium resistivity with a high level of accuracy.

Bioelectrochemical systems (BESs) are known to enhance the remediation of hydrocarbon-contaminated soil and sediments compared with natural attenuation, and the primary mechanism has been assumed as anaerobic degradation facilitated by electroactive bacteria (EAB) using the electrode as electron acceptor. However, known EAB were rarely found on the anodes of reported BESs, which challenged the fundamental mechanism of BESs although significant current generation was always observed during degradation of these recalcitrant substrates. This study however found the abundant EAB Geobacter (∼27.3%) in the anodic biofilms, which confirmed the role of electroactive bio-anode on the conversion of hydrocarbons into the current for the enhancement of remediation. Widespread occurrence of aerobic hydrocarbon-degrading bacteria (HDB) (e.g. ∼24.0% Parvibaculum and ∼30.6% Pseudomonas) was observed in soils with limited dissolved oxygen (∼0.4 mg/L). The higher abundance of dehydrogenase genes was found in the anode biofilms than that in soils, indicating anodic microorganisms may be mainly responsible for the removal of intermediates of aerobic hydrocarbons degradation in soils. High water saturation level and sandy soil texture showed positive impacts on bioelectrochemical remediation, while clay soil and unsaturation condition pose challenges in mass transfers in the matrix. The reactor performance was consistent with the phylogenetic molecular ecological network (pMENs) analysis, which showed that sandy soil BESs had tighter microbial network interactions than clay soil reactors.

Standardized prevalence of osteoporosis was 19.90% in the whole subjects aged between 50 and 87, 5.87% in men and 30.23% in women respectively. Risk factors associated with osteoporosis were analyzed. It is the first time to estimate the prevalence and characterize the epidemiology of osteoporosis in Chongqing, China. To investigate bone mineral density (BMD) profiles, osteoporosis prevalence, and its risk factors among residents aged above 20 years old in Chongqing Municipality, China. The study population consisted of 770 men and 1085 women aged 20 years and older with BMD measurements using central dual-energy X-ray absorptiometry (DXA). Information on sociodemographic characteristics and the potential risk factors associated with osteoporosis were collected by a standardized interviewer-administered questionnaire. Crude prevalence of osteoporosis was 12.99% in the whole subjects, 4.42% for men, and 19.08% for women by WHO criteria at various skeletal regions (among lumbar spine, femoral neck, and total hip). Standardized prevalence of osteoporosis was 19.90% in the whole subjects aged between 50 and 87, 5.87% in men and 30.23% in women respectively. Prevalence of osteoporosis increased with age, and the prevalence of osteoporosis in women was 6.10 times higher than it in men. The prevalence of osteoporosis was significantly associated with the past medical history of fracture (OR = 1.794, P = 0.007); overweight and obesity were considered to be protective factors for osteoporosis with OR of 0.514 and 0.300, respectively; high school graduate (OR = 0.399, P = 0.000 ) and milk intake (OR = 0.648, P = 0.008) were also protective factors for osteoporosis in men and women considered together; menopause was an independent risk factor of osteoporosis in females (OR = 1.782, P = 0.029); current smoking was an independent risk factor of osteoporosis in males (OR = 2.437, P = 0.046). The prevalence of osteoporosis and osteopenia was high among residents in Chongqing, China. Health education and behavior intervention should be focused on the elderly or female residents to promote the formulation of healthy lifestyle. Necessary steps are needed for more public education and a wider dissemination of information about osteoporosis and its prevention.

Background Air pollution is a potential environmental risk for sleep disturbance. However, the evidence is very limited in China. On the other hand, physical activity (PA) is a preventive behavior that can improve insomnia, but whether PA mitigates the negative impact of air pollution on insomnia is unknown. Methods We obtained data from the baseline of China Multi-Ethnic Cohort (CMEC) survey, and examined the association between air pollution and insomnia, as well as PA's modification effect of on this association. We included 70,668 respondents and assessed insomnia by self-reported symptoms collected using electronic questionnaires. Using satellite data, we estimated the residence-specified, three-year average PM1, PM2.5, PM10 (particulate matter with aerodynamic diameters of ≤1 μm, ≤2.5 μm and 10 μm, respectively), O3 (ozone), and NO2 (nitrogen dioxide) concentrations. We established the associations between air pollutants and insomnia through logistic regression. We evaluated the modification impact of total and domain-specific PA (leisure, occupation, housework, transportation) by introducing an interaction term. Results Positive associations were observed between long-term exposure to PM1, PM2.5, PM10, and O3 and insomnia symptoms, with ORs (95% CI) of 1.09 (1.03–1.16), 1.11 (1.07–1.15), 1.07 (1.05–1.10) and 1.15 (1.11–1.20), respectively. As total PA increased, the ORs of air pollution for insomnia tended to decrease and then rise. We observed varying modification effects of domain-specific PA. With an increase in leisure PA, the ORs for PM2.5 and PM10 significantly declined. However, increased ORs of air pollutants were related to insomnia among participants with higher levels of occupational and housework PA. Conclusion Long-term exposure to higher concentrations of PM1, PM2.5, PM10, and O3 increases the risk of insomnia symptoms. Moderate to high levels of leisure PA alleviate the harmful effects of air pollution on insomnia, while high levels of occupation and housework PA intensify such effects.

Background: Insomnia is linked with poor quality of life and many adverse health outcomes. Air pollution is a potential environmental risk for sleep disturbance. However, the evidence is very limited in China. On the other hand, physical activity (PA) is a preventive behavior that can improve insomnia, but whether PA mitigates the negative impact of air pollution on insomnia is unknown. Therefore, we examined the association between air pollution and insomnia, as well as PA’s modification effect of on this association. Methods: We obtained data from the baseline of China Multi-Ethnic Cohort (CMEC) survey, conducted from 2018 to 2019. We included 70668 respondents (out of 99,556). We assessed insomnia symptoms using any of the following self-reported symptoms, 1) difficulty initiating sleep or staying asleep, 2) waking up early in the morning, and 3) taking medication to help with sleep. Using satellite data, we estimated the residence-specified, three-year average PM1, PM2.5, PM10 (particulate matter with aerodynamic diameters of ≤1 μm, ≤2.5 μm and 10 μm, respectively), O3 (ozone), and NO2 (nitrogen dioxide) concentrations. We established the associations between air pollutants and insomnia symptoms through logistic regression. We evaluated the modification impact of total and domain-specific PA (leisure, occupation, housework, transportation) by introducing an interaction term into the model. Findings: After adjusting for potential confounders, we found that long-term exposure to PM1, PM2.5, PM10, and O3 is significantly associated with insomnia symptoms, with ORs (95% confidence interval [CI]) of 1.09 (1.03-1.16), 1.11 (1.07-1.15), 1.07 (1.05-1.10) and 1.15 (1.11-1.20), respectively. As total PA increased, the ORs of air pollution for insomnia tended to decrease and then rise. We observed varying modification effects of domain-specific PA. Transportation PA generally had no significant modification impact on the association between air pollution and insomnia. With an increase in leisure PA, the ORs for PM2.5 and PM10 significantly declined. However, we detected increased ORs of air pollutants in relation to insomnia among participants with higher levels of occupational and housework PA. Interpretation: Long-term exposure to higher concentrations of PM1, PM2.5, PM10, and O3 increases the risk of insomnia symptoms. Moderate to high levels of leisure PA alleviate the harmful effects of air pollution on insomnia, while high levels of occupation and housework PA intensify the effects. Funding Statement: The National Key Research and Development Program of China (Grant No. 2017YFC0907303), the Sichuan Science and Technology Program (Grant No. 2019YFS0274), and the National Natural Science Foundation of China (Grant No. 81773548). Declaration of Interests: The authors declare that they have no conflicts of interests. Ethics Approval Statement: We received approval from the Sichuan University Medical Ethical Review Board (K2016038).

The aim of our study was to examine the relationship between age at menarche (AM) and hypertension and to evaluate whether different dietary patterns have an effect on associations between AM and hypertension in a large-scale Han Chinese population in southwest China. A cross-sectional study was performed that included 44,900 participants from 17 districts in southwest China from September 2018 to January 2019. The study comprised 23,805 individuals in the final analysis. Logistic regression and multivariable linear regression were applied to estimate the dietary pattern-specific associations between AM and hypertension or systolic/diastolic blood pressure (SBP/DBP). Restricted cubic spline regression was utilized to calculate the shape of the relationship between AM and the odds ratio of hypertension. After adjusting for multiple variables, women who had a history of AM > 14 years were associated with an increased risk of hypertension (OR 1.12, 95%CI 1.04–1.19) and elevated levels of SBP (β 0.90, 95%CI 0.41–1.38) compared with those with AM ≤ 14 years among the total population, and this association was still statistically significant when we further adjusted for body mass index (BMI). In participants with AM > 14 years, the odds ratio values of hypertension increased with increasing menarche age. After stratification by age at recruitment, the positive association between menarche age and hypertension only remained in the middle-aged group, and this association was not found in the young and old groups. After stratification by the Dietary Approaches to Stop Hypertension (DASH) score among the total population, the positive association between AM and hypertension was presented only in the low DASH score group; however, this association was not found in the high DASH score group. Women who have a history of AM > 14 years should pay close attention to blood pressure levels and incorporate the DASH diet more in order to achieve the early prevention of hypertension, especially middle-aged women.

Water inrush incidents threaten the safety of coal mining. Understanding of hydrogeologic parameter distributions is critical for preventing water-related hazards in coal mines. During the deep mining (>1000 m) under the North China Plain, water from water-bearing strata discharges into coal seams through geologic conduits (i.e. water inrush) due to the fractured zone under the floor of working faces. In this study, a water inrush incident was exploited as an active stimulus. A 3D groundwater flow model was built for the eighth member of the Middle Ordovician system in Xingdong coal mine. Using this model and an inverse approach, we first checked if the data from the incident and an independent pumping test carry non-redundant information about the heterogeneity of the mine. Afterward, we combined these datasets to conduct a large-scale (approximately 10 km) hydraulic tomography (HT) analysis. The estimated hydraulic conductivity distribution from the HT analysis is found consistent with the distribution of known geologic faults. That is, a cluster of faults is characterized as a high-conductivity zone. A high conductivity zone is identified at locations close to the water inrush location, which is the high cement consumption zone during the grouting project. Finally, results of this study promote exploiting the water inrush events as a HT survey for mapping geologic structures over a large area.

Background Mosquitoes are responsible for spreading many diseases and their populations are susceptible to environmental changes. The ecosystems in the Three Gorges Region were probably altered because of changes to the environment during the construction of the Three Gorges Dam (TGD), the world's largest hydroelectric dam by generating capacity. Methods We selected three sites at which to monitor the mosquitoes from 1997 to 2009. We captured adult mosquitoes with battery-powered aspirators fortnightly between May and September of each year in dwellings and sheds. We identified the mosquito species, and examined changes in the species density during the TGD construction. We monitored changes in the species and density of mosquitoes in this area for 13 years during the TGD construction and collected information that could be used to support the control and prevention of mosquito-borne infections. Results We found that the mosquito species composition around the residential areas remained the same, and the density changed gradually during the TGD construction. The changes in the populations tended to be consistent over the years, and the densities were highest in July, and were between 3 and 5 times greater in the sheds than in the dwellings. Conclusions The mosquito species and populations remained stable during the construction of the TGD. The mosquito density may have increased as the reservoir filled, and may have decreased during the clean-up work. Clean-up work may be an effective way to control mosquitoes and prevent mosquito-borne diseases.

We collected spectral induced polarization spectra with clean sand mixed with metallic particles (either silver, graphite, copper, steel, magnetite, or pyrite particles). The initial pore water conductivity was either 1500 or [Formula: see text] depending on the experiments (25°C, NaCl). For each of the 15 experiments, we used a narrow and unimodal grain size distribution for the metallic particles. The resulting polarization spectra display clear polarization peaks in the phase and can be fitted with a Cole-Cole complex conductivity model. In addition to this, the chargeability scales with the volume content of the metallic particles in a way that is consistent with the theory of disseminated metallic particles in a weakly polarizable background. Similarly, the phase scales with the content of the metallic particles in a predictable way. The Cole-Cole relaxation time shows a rough dependence with the mean particle size. The trend between these two parameters can be used to determine an apparent diffusion coefficient for the charge carriers responsible for the polarization. Finally, we conducted a laboratory sandbox experiment in which we put a copper plate in tap water-saturated sand. We use an approach based on self-potential tomography and compactness to invert the secondary source current density from the secondary voltages associated with time-domain induced polarization. With this approach, we localized the copper plate and determined a value for the relaxation time that is consistent with the laboratory core sample experiments.

Hydraulic tomography (HT) is a well-established approach to successfully describe subsurface hydraulic heterogeneity. This work explored the potential of HT and the simultaneous successive linear estimator algorithm to map the distribution and connectivity of karst conduits and their hydraulic parameters at the engineering scale. Three generalized synthetic karst conduit models, auxiliary conduit, cave and waterfall, were established. A series of pumping tests were conducted at different locations as forward simulations to collect hydraulic head responses. These responses were then used for the HT inversion analysis to estimate hydraulic parameter fields of karst aquifers under steady-state and transient conditions. Our results show that high-density observation wells substantially assist with interpreting the reliable spatial distribution of hydraulic parameters. With the increase in the number of pumping wells in the HT inversion, the estimates of hydraulic conductivity and specific storage became more accurate for the auxiliary conduit model, but for the cave and waterfall models, there was no significant improvement. The hydraulic conductivity (K) tomograms from transient hydraulic tomography (THT) better indicated the heterogeneity of the three karst models than those from steady-state hydraulic tomography (SSHT) because a large number of hydraulic head records were introduced into the THT inversion process. Moreover, when reliable geological data are available, the accuracy of the estimated hydraulic parameter maps can be greatly improved even if only infrequent hydraulic head measurements can be obtained, implying that a priori geological information may be extremely valuable in mapping karst conduit heterogeneity. Finally, the robustness of HT in mapping karst conduits is verified through the simulation of independent cross-hole pumping tests. This study proved that hydraulic tomography utilizing groundwater responses from a series of cross-hole pumping tests is an efficient and cost-effective way and provided a feasible method for accurate identification of hydraulic heterogeneity of karst aquifers.

Efficient noninvasive techniques are desired for monitoring the remediation process of contaminated soils. We applied the direct current resistivity technique to image conductivity changes in sandbox experiments where two sandy and clayey soils were initially contaminated with diesel hydrocarbon. The experiments were conducted over a 230 day period. The removal of hydrocarbon was enhanced by a bioelectrochemical system (BES) and the electrical potentials of the BES reactors were also monitored during the course of the experiment. We found that the variation in electrical conductivity shown in the tomograms correlate well with diesel removal from the sandy soil, but this is not the case with the clayey soil. The clayey soil is characterized by a larger specific surface area and therefore a larger surface conductivity. In sandy soil, the removal of the diesel and products from degradation leads to an increase in electrical conductivity during the first 69 days. This is expected since diesel is electrically insulating. For both soils, the activity of BES reactors is moderately imaged by the inverted conductivity tomogram of the reactor. An increase in current production by electrochemically active bacteria activity corresponds to an increase in conductivity of the reactor.

Time-domain induced polarization (TDIP) is a nonintrusive imaging technique of the subsurface that can be used to localize polarizable bodies including metallic objects and clay-rich materials. We first reviewed recent advances in the interpretation of induced polarization data. Then, we performed laboratory and sandbox experiments to determine the frequency-domain and TDIP signature of (1) a metal bar in sand, (2) dispersed semiconductors (e.g., pyrite) in sand, and (3) bentonite. In the case of the sandbox experiments, the three types of bodies were localized in the center of the sandbox, which was filled with water-saturated sand. We determined that chargeability was the best parameter to characterize metallic bodies (the metallic bar and the dispersed pyrite), whereas normalized chargeability was the best parameter to characterize the cation exchange capacity and therefore the clay content of the subsurface at a given clay mineralogy. For interpretation purposes, it was therefore important to display the right parameters in TDIP depending on the type of target we wanted to image for engineering applications.

The secondary voltage associated with time-domain induced polarization data of disseminated metallic particles (such as pyrite and magnetite) in a porous material can be treated as a transient self-potential problem. This self-potential field is associated with the generation of a secondary-source current density. This source current density is proportional to the gradient of the chemical potentials of the [Formula: see text]- and [Formula: see text]-charge carriers in the metallic particles or ionic charge carriers in the pore water including in the electrical double layer coating the surface of the metallic grains. This new way to treat the secondary voltages offers two advantages with respect to the classical approach. The first is a gain in terms of acquisition time. Indeed, the target can be illuminated with a few primary current sources, all the other electrodes being used simultaneously to record the secondary voltage distribution. The second advantage is with respect to the inversion of the obtained data. Indeed, the secondary (source) current is linearly related to the secondary voltage. Therefore, the inverse problem of inverting the secondary voltages is linear with respect to the source current density, and the inversion can be done in a single iteration. Several iterations are, however, required to compact the source current density distribution, still obtaining a tomogram much faster than inverting the apparent chargeability data using the classical Gauss-Newton approach. We have performed a sandbox experiment with pyrite grains locally mixed to sand at a specific location in the sandbox to demonstrate these new concepts. A method initially developed for self-potential tomography is applied to the inversion of the secondary voltages in terms of source current distribution. The final result compares favorably with the classical inversion of the time-domain induced polarization data in terms of chargeability, but it is much faster to perform.

Experiments on crack initiation and propagation of double-notched rocks caused by thermal–mechanical loading were carried out by using in-situ SEM observation technique. The results indicated that thermal-induced or thermal–mechanical-induced cracking mechanisms depend strongly on thermal deformation mismatch between the mineral compositions. Micro cracks initiation occurred mainly in the harder and larger quartz grains, but the failure strength of rock did not adequately degrade when surface micro crack density is less than 40 (mm−2). At last, a reliability analysis of 3-parameter Weibull distribution model is presented to discuss the effect of the thermal-induced micro crack on failure strength of rock. Threshold value by thermal-induced micro crack density to influence on the failure strength of crustal rock can be estimated at about 50–60 (mm−2).

Summary The feedbacks among forest transpiration, soil moisture, and subsurface flowpaths are poorly understood. We investigate how soil moisture is affected by daily transpiration using time-lapse electrical resistivity imaging (ERI) on a highly instrumented ponderosa pine and the surrounding soil throughout the growing season. By comparing sap flow measurements to the ERI data, we find that periods of high sap flow within the diel cycle are aligned with decreases in ground electrical conductivity and soil moisture due to drying of the soil during moisture uptake. As sap flow decreases during the night, the ground conductivity increases as the soil moisture is replenished. The mean and variance of the ground conductivity decreases into the summer dry season, indicating drier soil and smaller diel fluctuations in soil moisture as the summer progresses. Sap flow did not significantly decrease through the summer suggesting use of a water source deeper than 60 cm to maintain transpiration during times of shallow soil moisture depletion. ERI captured spatiotemporal variability of soil moisture on daily and seasonal timescales. ERI data on the tree showed a diel cycle of conductivity, interpreted as changes in water content due to transpiration, but changes in sap flow throughout the season could not be interpreted from ERI inversions alone due to daily temperature changes.

While hydraulic tomography (HT) is a mature aquifer characterization technology, its applications to characterize hydrogeology of kilometer-scale fault and fracture zones are rare. This paper sequentially analyzes datasets from two new pumping tests as well as those from two previous pumping tests analyzed by Illman et al. (2009) at a fractured granite site in Mizunami, Japan. Results of this analysis show that datasets from two previous pumping tests at one side of a fault zone as used in the previous study led to inaccurate mapping of fracture and fault zones. Inclusion of the datasets from the two new pumping tests (one of which was conducted on the other side of the fault) yields locations of the fault zone consistent with those based on geological mapping. The new datasets also produce a detailed image of the irregular fault zone, which is not available from geological investigation alone and the previous study. As a result, we conclude that if prior knowledge about geological structures at a field site is considered during the design of HT surveys, valuable non-redundant datasets about the fracture and fault zones can be collected. Only with these non-redundant data sets, can HT then be a viable and robust tool for delineating fracture and fault distributions over kilometer scales, even when only a limited number of boreholes are available. In essence, this paper proves that HT is a new tool for geologists, geophysicists, and engineers for mapping large-scale fracture and fault zone distributions.

Water hazards threat the safety of underground mining. A detailed characterization of hydraulic parameters is helpful for the design of engineering projects to prevent underground water hazards. Utilizing aquifer’s natural artesian condition, water releasing tests are often performed in China’s underground mines. In this research, we propose to interpret water releasing test data with hydraulic tomography (HT) technique. A 216-hour duration test was performed to localize water hazard areas in Ningtiaota underground coal mine. Groundwater was released with four sequential stages from 30 boreholes. HT analysis clearly shows that the study area has a potential water hazard region in southern part by only using data from the first two stages, which coincides with existing water inrush incident location. With the addition of more pressure responses from stages 3 and 4, it discovers low transmissivity and storativity values in northern part. Our numerical examples further demonstrate that sequential water releasing tests produce comparable hydraulic parameter distributions to tomographic tests. In the end, we conclude that water releasing tests aided by HT technique can leads to a high resolution characterization of water hazard aquifers.

We have investigated the influence of temperature and salinity upon the spectral induced polarization of 10 samples including rocks with their mineralization (galena, chalcopyrite) plus sand mixed with semiconductors such as magnetite grains, graphite, and pyrite cubes of two different sizes. Measurements are made in a temperature-controlled bath with a high-precision impedance meter and using NaCl solutions. We cover the temperature range 5°C−50°C and the frequency range [Formula: see text] to 45 kHz. For one large pyrite cube, we also investigated six salinities from 0.1 to [Formula: see text] (at 25°C, NaCl) and three salinities for graphite. The spectra are fitted with a Cole-Cole complex parametric conductivity model for which we provide a physical meaning to the four Cole-Cole parameters. As expected, the Cole-Cole exponent and the chargeability are independent of the temperature and salinity. The instantaneous and steady state (direct current [DC]) conductivities depend on the salinity and temperature. This temperature dependence can be fitted with an Arrhenius law (combining the Stokes-Einstein and Vogel-Fulcher-Tammann equations) with an activation energy in the range of [Formula: see text]. This activation energy is the same as for the bulk pore-water conductivity demonstrating the control by the background electrolyte of these quantities, as expected. The instantaneous and DC conductivities depend on the salinity in a predictable way. The Cole-Cole relaxation time decreases with the temperature and decreases with the salinity. This behavior can be modeled with an Arrhenius law with an apparent activation energy of [Formula: see text]. A finite-element model is used further to analyze the mechanisms of polarization, and it can reproduce the temperature and salinity dependencies observed in the laboratory.