Geogenic Phosphorus Enrichment in Groundwater due to Anaerobic Methane Oxidation-Coupled Fe(III) Oxide Reduction.

Accumulation of geogenic phosphorus (P) in groundwater is an emerging environmental concern, which is closely linked to coupled processes involving FeOOH and organic matter under methanogenic conditions. However, it remains unclear how P enrichment is associated with methane cycling, particularly the anaerobic methane oxidation (AMO). This study conducted a comprehensive investigation of carbon isotopes in dissolved inorganic carbon (DIC), CO2, and CH4, alongside Fe isotopes, microbial communities, and functions in quaternary aquifers of the central Yangtze River plain. The study found that P concentrations tended to increase with Fe(II) concentrations, δ56Fe, and δ13C-DIC, suggesting P accumulation due to the reductive dissolution of FeOOH under methanogenic conditions. The positive correlations of pmoA gene abundance versus δ13C-CH4 and Fe concentrations versus δ13C-CH4, and the prevalent presence of Candidatus_Methanoperedens, jointly demonstrated the potential significance of Fe(III)-mediated AMO process (Fe-AMO) alongside traditional methanogenesis. The increase of P concentration with δ13C-CH4 value, pmoA gene abundance, and Fe concentration suggested that the Fe-AMO process facilitated P enrichment in groundwater. Redundancy analysis confirmed this assertion, identifying P concentration as the primary determinant and the cooperative influence of Fe-AMO microorganisms such as Candidatus_Methanoperedens and Geobacter on P enrichment. Our work provided new insights into P dynamics in subsurface environments.

How to Improve People's Intentions Regarding COVID-19 Vaccination in China: A Randomized Controlled Trial.

BACKGROUND: The global COVID-19 pandemic has impaired the health and living conditions of millions of people. For governments to formulate policies promoting vaccination behavior, it is important to understand individuals' intentions to vaccinate. This study explores the effectiveness of a brief online intervention based on the Health Action Process Approach (HAPA) in improving individuals' COVID-19 vaccination intention, as well as considering the reasons for their unwillingness to get vaccinated. METHOD: A total of 1,258 participants were assessed using a questionnaire to determine their phase of vaccination intention (pre-intention, intention, and action). Subsequently, focused on the underlying factors in the pre-intention phase (i.e., task self-efficacy, outcome expectation, and risk perception), a 7-day randomized controlled HAPA intervention (n intervention = 57, n control = 49) was conducted online for individuals who were not willing to get vaccinated. The measurement points included pre- (T1), post- (T2), and 30-day follow-up (T3). RESULTS: The intervention may effectively improve participants' COVID-19 vaccination intentions; however, it had no impact on their planning and actions involved in taking the vaccine. CONCLUSIONS: This study provides relevant reference data for government stakeholders to use in developing public awareness campaigns and policies to encourage COVID-19 vaccination.

Online photography intervention reduces internet addiction during COVID-19: A randomised controlled trial.

The COVID-19 pandemic has escalated concerns regarding internet addiction. This study investigated the impact of an online photograph intervention on internet addiction and identified its effectiveness mechanisms. Individuals diagnosed with internet addiction (internet addiction test score > 36, Mage = 22.85, 78.6% women) were randomly allocated to either the intervention (n = 64) or control (n = 81) groups. For 10 days, the intervention group was tasked with photographing "things that make you feel a sense of control in life" and writing 100-word descriptions explaining the reason for the sense of control elicited by the image. Meanwhile, the control group participated only in the assessments. Assessments were conducted before the intervention, immediately afterward and 7 days later. A significant interaction between group and time was observed, with the intervention group showing a notable reduction in internet addiction and an increase in sense of control. The sense of control at post-test significantly mediated the intervention's effect on reducing internet addiction at follow-up, but only among individuals with high perceived social support. The findings indicate that online photography interventions can effectively diminish internet addiction, with a sense of control acting as a potent mechanism for intervention, particularly in individuals with substantial perceived social support.

The mediating role of default mode network during meaning-making aroused by mental simulation between stressful events and stress-related growth: a task fMRI study.

BACKGROUND: Stressful events and meaning-making toward them play an important role in adolescents' life and growth. However, ignoring positive stressful events leads to negativity bias; further, the neural mechanisms of meaning-making are unclear. We aimed to verify the mediating role of meaning-making in stressful events and stress-related growth and the function of the default mode network (DMN) during meaning-making in this functional magnetic resonance imaging (fMRI) study. METHODS: Participants comprised 59 university students. Stressful life events, meaning-making, and stress-related growth were assessed at baseline, followed by fMRI scanning during a meaning-making task aroused by mental simulation. General linear modeling and psychophysiological interaction (PPI) analyses were used to explore the activation and functional connectivity of DMN during meaning-making. RESULTS: Mental simulation triggered meaning-making, and DMN activity decreased during meaning-making. Activation of the DMN was negatively correlated with coping flexibility, an indicator of stress-related growth. PPI analysis showed that meaning-making was accompanied by diminished connectivity in the DMN. DMN activation during meaning-making can mediate the relationship between positive stressful events and coping flexibility. CONCLUSIONS: Decreased DMN activity and diminished functional connectivity in the DMN occurred during meaning-making. Activation of the DMN during meaning-making could mediate the relationship between positive stressful events and stress-related growth, which provides a cognitive neural basis for the mediating role of meaning-making in the relationship between stressful events and indicators of stress-related growth. IMPLICATIONS: This study supports the idea that prosperity makes heroes, expands the meaning-making model, and suggests the inclusion of enhancing personal resources and meaning-making in education. This study was the first to validate the activation pattern and functional connectivity of the DMN during meaning-making aroused by mental simulation using an fMRI task-state examination, which can enhance our sense of meaning and provide knowledge that can be used in clinical psychology interventions. TRIAL REGISTRATION: The study protocol was pre-registered in Open Science Framework (see osf.io/ahm6e for details).

Loss of Selenium from Mollisol Paddy Wetlands of Cold Regions: Insights from Flow-through Reactor Experiments and Process-Based Modeling.

Mollisols are critical agricultural resources for securing global food supply. Due to its health importance, selenium (Se) fate in the Mollisols attracts growing concerns. Land use change from conventional drylands to paddy wetlands impacts Se bioavailability in the vulnerable Mollisol agroecosystems. The underlying processes and mechanisms however remain elusive. Here, results of flow-through reactor experiments with paddy Mollisols from northern cold-region sites indicate that continuous flooding with surface water for 48 d induced redox zonation that facilitated the loss of Mollisol Se by up to 51%. Further process-based biogeochemical modeling suggests largest degradation rates of dissolved organic matter (DOM) in 30 cm deep Mollisols that contained the highest-level labile DOM and organic-bound Se. Electron shunting from degradation of Se-bearing DOM coupled to reductive dissolution of Se-adsorbed Fe oxides accounts mainly for Se(IV) release into the pore water. Consequent changes in DOM molecular composition make the reservoir of organic-bound Se vulnerable to flooding-induced redox zonation and likely enhance Se loss through destruction of thiolated Se and emission of gaseous Se from the Mollisol layer. This study highlights a neglected scenario where the speciation-driven loss of bioavailable Se from the paddy wetlands can be a significant consequence in the cold-region Mollisol agroecosystems.

Fluvial Deposition and Land Use Change Control Selenium Occurrence in Mollisols of Cold Region Agroecosystems.

Mollisols support the most productive agroecosystems in the world. Despite their critical links to food quality and human health, the varying distributions of selenium (Se) species and factors governing Se mobility in the mollisol vadose zone remain elusive. This research reveals that, in northern mollisol agroecosystems, Se hotspots (≥0.32 mg/kg) prevail along the regional river systems draining the Lesser Khingan Mountains, where piedmont Se-rich oil shales are the most probable source of regional Se. While selenate and selenite dominate Se species in the water-soluble and absorbed pools, mollisol organic matter is the major host for Se. Poorly crystalline and crystalline Fe oxides are subordinate in Se retention, hosting inorganic and organic Se at levels comparable to those in the adsorbed pool. The depth-dependent distributions of mollisol Se species for the non-cropland and cropland sites imply a predominance of reduced forms of Se under the mildly acidic and reducing conditions that, in turn, are variably impacted by agricultural land use. These findings therefore highlight that fluvial deposition and land use change together are the main drivers of the spatial variability and speciation of mollisol Se.

Groundwater Quality and Health: Making the Invisible Visible.

Linking groundwater quality to health will make the invisible groundwater visible, but there are knowledge gaps to understand the linkage which requires cross-disciplinary convergent research. The substances in groundwater that are critical to health can be classified into five types according to the sources and characteristics: geogenic substances, biogenic elements, anthropogenic contaminants, emerging contaminants, and pathogens. The most intriguing questions are related to quantitative assessment of human health and ecological risks of exposure to the critical substances via natural or induced artificial groundwater discharge: What is the list of critical substances released from discharging groundwater, and what are the pathways of the receptors' exposure to the critical substances? How to quantify the flux of critical substances during groundwater discharge? What procedures can we follow to assess human health and ecological risks of groundwater discharge? Answering these questions is fundamental for humans to deal with the challenges of water security and health risks related to groundwater quality. This perspective provides recent progresses, knowledge gaps, and future trends in understanding the linkage between groundwater quality and health.

The Relationship Between Meaning in Life and Health Behaviors in Adults Aged 55 Years and Over During the COVID-19 Pandemic: the Mediating Role of Risk Perception and the Moderating Role of Powerful Others Health Locus of Control.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has impacted many people's meaning in life and health behaviors. This study aimed to verify the relationship among meaning in life (MIL), epidemic risk perception, health locus of control (HLC), and preventive health behaviors among older adults after the COVID-19 outbreak was declared a pandemic. METHOD: In this longitudinal study, 164 participants aged 55 years and above completed the following measures at time 1 (February 19, 2021) and one month later at time 2 (March 19, 2021): Meaning in Life in the Epidemic Questionnaire, Epidemic Risk Perception Questionnaire, Multidimensional Health Locus of Control Scale, and Health Behaviors Before and After the Epidemic Survey. Hayes' SPSS Process Macro was used to analyze the mediating effect of epidemic risk perception (model 4) and the moderating role of powerful others HLC in the mediation model (model 14). RESULTS: The results showed that after controlling for gender, age, education level, and health behaviors at the baseline, risk perception had a significant mediating effect on the relationship between MIL and preventive health behaviors (ß = .02, SE = .01, 95% CI [.00, .04]). In addition, powerful others HLC had a moderating effect on the second half of the mediating effect (ß = .02, p = .02, 95% CI [.00, .03]). Specifically, compared to the older adults with low powerful others HLC, the risk perception of older adults with high powerful others HLC increased preventive health behaviors. CONCLUSION: Practitioners should adequately cultivate older adults' risk awareness and reinforce the importance of advice from doctors and professionals, thereby effectively enhancing the preventive health behaviors of older adults in China during the COVID-19 pandemic.

Brief emotional eating scale: A multinational study of factor structure, validity, and invariance.

Emotional eating or the tendency to eat in response to emotional states can be assessed using self-report measures. The Emotional Eating Scale-II is a commonly used and reliable instrument that measures the desire to eat in response to a range of unpleasant and pleasant emotions. The current study aimed to corroborate the validity of the EES-II and expand its utility by investigating its dimensionality and testing its measurement invariance in samples from English-speaking and non-English-speaking countries. Convergent and predictive validity in respect of food craving, eating, and health indicators were also examined. This cross-national study included a total of 2485 adult participants recruited from Finland, North America, Philippines, United Kingdom, China, Italy, Spain, and South Korea, who completed the EES-II in six different languages. Factor analyses supported a four-factor structure including valence (pleasant, unpleasant) and activation (high, low) for a 12-item English version and slightly modified non-English adaptations. The model exhibited good fit in all samples, and convergent validity was demonstrated. Full invariance of factor loadings and partial invariance of factor loading, intercepts, and error variances was established across samples. Structural equation models revealed that high activation (pleasant and unpleasant) states predicted food cravings and reported eating. Overall findings across multiple samples and countries supported the factorial structure, reliability, invariance, and validity of the resulting Brief Emotional Eating Scale (BEES).

Effect of Perspective-Taking on Trust Between Doctors and Patients: A Randomized Controlled Trial.

Tension between doctors and patients as a social problem has existed for a long time; thus far, there is no good solution. From the perspective of trust between doctors and patients, this research studies the relieving effect of perspective-taking interventions on the tension between doctors and patients. This study used a randomized, single-blind online experiment. 133 participants were randomly divided into an intervention group (n = 67) and control group (n = 66). Participants were asked to complete writing tasks from the doctor's perspective. Patients' trust in doctors was measured at 3 time points: before intervention, immediately after intervention, and 10 days after the intervention. Findings showed a significant interaction effect between time measurement and group. In the intervention group, a pairwise comparison of time measurements showed a significant difference between T1 and T2. Perspective-taking interventions can improve patients' trust in doctors, but this effect diminishes over time.

Immediate and delayed psychological effects of province-wide lockdown and personal quarantine during the COVID-19 outbreak in China.

BACKGROUND: The COVID-19 pandemic has greatly affected public health and wellbeing. In response to the pandemic threat of the coronavirus epidemic, several countries, including China, adopted lockdown and quarantine policies, which may cause psychological distress. This study aimed to explore the psychological impact of province-wide lockdown and personal quarantine during the COVID-19 outbreak in China as well as the corresponding risk factors and protective factors. METHODS: We examined the immediate (2-week) and delayed (2-month) impact of province-wide lockdown and personal quarantine on psychological distress in a national sample of 1390 Chinese residents. RESULTS: No immediate impact of province-wide lockdown on psychological distress was observed, whereas personal quarantine increased individuals' anxiety, fear, and anger. Despite the lack of initial association, psychological distress increased among those in province-wide lockdown. Self-stigma and personal control both significantly moderated the association between lockdown and psychological distress, but in different directions. Those with higher self-stigma and lower personal control were more impacted by the lockdown. Government support moderated the impact of quarantine on psychological distress, but not that of lockdown. CONCLUSIONS: The delayed effects of lockdown and quarantine on psychological distress were observed, and self-stigma, social support, and perceived control moderate the relationships. This study is the first to demonstrate the psychological costs of province-wide lockdowns on individuals' mental health, providing evidence of the need for mitigation strategies and timely public mental health preparedness in countries with recent outbreaks of COVID-19.

The Interplay Between Strictness of Policies and Individuals' Self-Regulatory Efforts: Associations with Handwashing During the COVID-19 Pandemic.

BACKGROUND: Patterns of protective health behaviors, such as handwashing and sanitizing during the COVID-19 pandemic, may be predicted by macro-level variables, such as regulations specified by public health policies. Health behavior patterns may also be predicted by micro-level variables, such as self-regulatory cognitions specified by health behavior models, including the Health Action Process Approach (HAPA). PURPOSE: This study explored whether strictness of containment and health policies was related to handwashing adherence and whether such associations were mediated by HAPA-specified self-regulatory cognitions. METHODS: The study (NCT04367337) was conducted among 1,256 adults from Australia, Canada, China, France, Gambia, Germany, Israel, Italy, Malaysia, Poland, Portugal, Romania, Singapore, and Switzerland. Self-report data on cross-situational handwashing adherence were collected using an online survey at two time points, 4 weeks apart. Values of the index of strictness of containment and health policies, obtained from the Oxford COVID-19 Government Response Tracker database, were retrieved twice for each country (1 week prior to individual data collection). RESULTS: Across countries and time, levels of handwashing adherence and strictness of policies were high. Path analysis indicated that stricter containment and health policies were indirectly related to lower handwashing adherence via lower self-efficacy and self-monitoring. Less strict policies were indirectly related to higher handwashing adherence via higher self-efficacy and self-monitoring. CONCLUSIONS: When policies are less strict, exposure to the SARS-CoV-2 virus might be higher, triggering more self-regulation and, consequently, more handwashing adherence. Very strict policies may need to be accompanied by enhanced information dissemination or psychosocial interventions to ensure appropriate levels of self-regulation.

Health Status Stability of Patients in a Medical Rehabilitation Program: What Are the Roles of Time, Physical Fitness Level, and Self-efficacy?

BACKGROUND: Individuals' physical and mental health, as well as their chances of returning to work after their ability to work is damaged, can be addressed by medical rehabilitation. AIM: This study investigated the developmental trends of mental and physical health among patients in medical rehabilitation and the roles of self-efficacy and physical fitness in the development of mental and physical health. DESIGN: A longitudinal design that included four time-point measurements across 15 months. SETTING: A medical rehabilitation center in Germany. POPULATION: Participants included 201 patients who were recruited from a medical rehabilitation center. METHODS: To objectively measure physical fitness (lung functioning), oxygen reabsorption at anaerobic threshold (VO2AT) was used, along with several self-report scales. RESULTS: We found a nonlinear change in mental health among medical rehabilitation patients. The results underscored the importance of medical rehabilitation for patients' mental health over time. In addition, patients' physical health was stable over time. The initial level of physical fitness (VO2AT) positively predicted their mental health and kept the trend more stable. Self-efficacy appeared to have a positive relationship with mental health after rehabilitation treatment. CONCLUSIONS: This study revealed a nonlinear change in mental health among medical rehabilitation patients. Self-efficacy was positively related to mental health, and the initial level of physical fitness positively predicted the level of mental health after rehabilitation treatment. CLINICAL REHABILITATION: More attention could be given to physical capacity and self-efficacy for improving and maintaining rehabilitants' mental health.

Effects of Environmental Worry on Fruit and Vegetable Intake.

BACKGROUND: Environmental worry, a response to environmental pollution, is a well-established predictor of pro-environmental behaviors. However, its relationship with health-promoting behaviors, such as fruit and vegetable intake (FVI), is unclear. In three studies, we explored the associations between environmental worry, behavioral intention, and FVI. METHOD: Study 1, enrolling 358 company trainees who provided their data at Time 1 (T1) and Time 2 (T2; a 2-month follow-up), examined the relationship between environmental worry and FVI. Study 2, enrolling 226 employees providing their data at T1 and T2 (a 2-month follow-up), examined the mediating effects of intention in the relationship between environmental worry and FVI using a cross-lagged design. In study 3, data from 217 participants were collected three times over a period of 4 months. We re-examined the mediating effect of intention and further explored the moderating effect of future focus. RESULTS: Environmental worry predicted beneficial changes in FVI (studies 1, 2, and 3). Environmental worry predicted FVI through intention (studies 2 and 3). The mediating effect of intention on the relationship between environmental worry and FVI was moderated by future focus: individuals with high environmental worry formed stronger intention when they also reported a strong future focus (study 3). CONCLUSIONS: Our findings provide novel evidence for the direct and indirect links between environmental worry and health-promoting behavior (i.e., FVI).

Interdependent self-construal moderates the relationship between pro-generation investment and future orientation: A cross-cultural comparison.

INTRODUCTION: Cultural orientation and interdependent self-construal can moderate the relationship between perceived pro-generation investment and future orientation of young adults. To test how interdependent self-construal moderate the relationship between pro-generation investment and future orientation of young adults from two different cultural ecologies was the aim of the current study. METHODS: A cross-cultural comparison was conducted among study participants from China, Germany, and the United States. Interdependent self-construal, perceived pro-generation investment by parents (parental investment), and future orientation were measured. Cross-cultural data were collected from 205 college students in China, a collectivist culture, and 169 college students in Germany (n = 50) and the United States (n = 119), which are individualist cultures. We examined a three-way interaction with cultural orientation and interdependent self-construal as moderators in the relationship between perceived parental investment and future orientation. RESULTS: In the collectivist cultural context, there appeared no moderating effect of interdependent self-construal on the relationship between perceived parental investment and future orientation, although interdependent self-construal and perceived parental investment predicted future orientation. In the individualistic cultural context, there was a moderating effect. For individuals high in interdependent self-construal, future orientation remained stable as perceived parental investment increased. For individuals low in interdependent self-construal, future orientation decreased as perceived parental investment increased. CONCLUSIONS: The findings have practical implications in that parents should follow the cultural orientation of their background and provide their children with individualized investment and education to shape the future orientation of their offspring.

The associations among emotional factors, personality traits, and addiction-like eating: A study on university students in six Asian countries/regions.

OBJECTIVE: Addiction-like eating (AE) is characterized by food cravings and loss of control over excessive food consumption. This study investigated the associations among emotional factors, personality traits, and AE symptoms in Asian young adults. METHOD: This study included 6,823 Asian university students in South Korea, China, Singapore, Hong Kong/Macao, Japan, and Taiwan. Participants completed the modified Yale Food Addiction Scale (mYFAS) and scales on the Big-Five personality traits, impulsivity, anxiety, and depression. RESULTS: 6.2% of the participants met the mYFAS (DSM-IV-TR) food addiction diagnostic threshold. Participants from South Korea (7.9%) had the highest rate of food addiction, while participants from Japan (5.1%) and Taiwan (4.1%) reported the lowest rates. Emotional factors of anxiety and depression were the most robust correlates of AE symptoms, followed by country/region and personality factors of higher impulsivity, higher extraversion, and lower agreeableness. Personality correlates were region-specific. Higher impulsivity was a significant correlate for participants from South Korea and Taiwan, higher extraversion for participants from Singapore and Japan, and lower agreeableness for participants from China and Taiwan. Gender was also a significant correlate for participants from South Korea, Hong Kong/Macao, and Taiwan. DISCUSSION: Emotional and personality factors are important correlates of AE symptoms among Asian young adults.

The trajectory of COVID-19 pandemic and handwashing adherence: findings from 14 countries.

BACKGROUND: The COVID-19 pandemic has affected people's engagement in health behaviors, especially those that protect individuals from SARS-CoV-2 transmission, such as handwashing/sanitizing. This study investigated whether adherence to the World Health Organization's (WHO) handwashing guidelines (the outcome variable) was associated with the trajectory of the COVID-19 pandemic, as measured by the following 6 indicators: (i) the number of new cases of COVID-19 morbidity/mortality (a country-level mean calculated for the 14 days prior to data collection), (ii) total cases of COVID-19 morbidity/mortality accumulated since the onset of the pandemic, and (iii) changes in recent cases of COVID-19 morbidity/mortality (a difference between country-level COVID-19 morbidity/mortality in the previous 14 days compared to cases recorded 14-28 days earlier). METHODS: The observational study (#NCT04367337) enrolled 6064 adults residing in Australia, Canada, China, France, Gambia, Germany, Israel, Italy, Malaysia, Poland, Portugal, Romania, Singapore, and Switzerland. Data on handwashing adherence across 8 situations (indicated in the WHO guidelines) were collected via an online survey (March-July 2020). Individual-level handwashing data were matched with the date- and country-specific values of the 6 indices of the trajectory of COVID-19 pandemic, obtained from the WHO daily reports. RESULTS: Multilevel regression models indicated a negative association between both accumulation of the total cases of COVID-19 morbidity (B = -.041, SE = .013, p = .013) and mortality (B = -.036, SE = .014 p = .002) and handwashing. Higher levels of total COVID-related morbidity and mortality were related to lower handwashing adherence. However, increases in recent cases of COVID-19 morbidity (B = .014, SE = .007, p = .035) and mortality (B = .022, SE = .009, p = .015) were associated with higher levels of handwashing adherence. Analyses controlled for participants' COVID-19-related situation (their exposure to information about handwashing, being a healthcare professional), sociodemographic characteristics (gender, age, marital status), and country-level variables (strictness of containment and health policies, human development index). The models explained 14-20% of the variance in handwashing adherence. CONCLUSIONS: To better explain levels of protective behaviors such as handwashing, future research should account for indicators of the trajectory of the COVID-19 pandemic. TRIAL REGISTRATION: Clinical Trials.Gov, # NCT04367337.

Fractionation of carbon isotopes of dissolved organic matter adsorbed to goethite in the presence of arsenic to study the origin of DOM in groundwater.

Natural dissolved organic matter (DOM) in groundwater plays a crucial role in mobilizing arsenic (As). The complex contribution of DOM sources makes it hard to predict how the variation of environmental conditions would affect the distribution of As concentrations. Identifying the carbon isotope fractionation of DOM is the key to quantify DOM sources based on stable carbon isotopes. To understand the magnitude and variability in the carbon isotopic fractionation of DOM in competitive adsorption with As(V), this study investigated the δ13C values of fulvic acid (FA) and DOM during adsorption to goethite in the presence of As(V), at a specific pH and temperature. The carbon isotopic enrichment factor (ε) of FA in the adsorption to goethite was 0.65 ± 2.11‰ at pH 4.1, 25 °C, suggesting that FA molecules containing 13C were more easily adsorbed to goethite. An increasing temperature increased εFA from 0.32 ± 1.17‰ to 0.82 ± 5.39‰ at 15-35 °C. For dissolved sediment organic matter (DSOM) cases, molecules containing 13C were more easily adsorbed to goethite. However, enrichment factors were not detected due to a reduction in DSOM adsorption and the diversity of natural humic substances or groups. The findings provide basic data for accurately ascertaining DOM sources through carbon isotopes, which is significant for predicting As fluctuation in aquifers affected by monsoon climate and/or human activities.

Distribution, origin and speciation of soil selenium in the black soil region of Northeast China.

Selenium (Se) is an essential trace element within human beings that hold with crucial biological functions. Investigating the complex origin of soil Se is of great importance to scientifically approach the land use of Se-rich land use, and the respective promotion of regional economic development. In this study, 160 soil samples from 10 profiles in farmland and woodland were collected in Hailun city, which is a typical black soil region in Northeast China, in order to characterize the distribution and speciation of Se in the black soil, and to identify the origin of soil Se. The total selenium content in the soil ranges from 0.045 to 0.444 µg g-1, with an average selenium content in black soil (0.318 µg g-1) of three times greater than that found in the yellow-brown soil (0.114 µg g-1). The land-use type has a significant influence on the distribution of selenium in the black soil. Moreover, Se and heavy metals have a significant (positive or negative) correlation, in which TOC plays an important role. The black soil presents a consistent REE distribution pattern with underlying yellow-brown soil indicating black soil originates from yellow-brown soil. REE geostatistical analysis suggests that the soil Se partly originates from shale weathering and enriches in black soil. Moreover, elemental geochemical analysis and XRD results show that the paleoclimate change from humid and warm to dry and cold is favorable for organic matter accumulation, resulting in less leaching and enhanced adsorption of selenium into the black soil.

Impact of Physico-Chemical Heterogeneity on Arsenic Sorption and Reactive Transport under Water Extraction.

Heterogeneity in physical and chemical properties is a common characteristic in a subsurface environment. This study investigated the effect of physico-chemical heterogeneity on arsenic (As) sorption and reactive transport under water extraction in a layered system with preferential flow paths. A flume experiment was performed to derive the spatio-temporal data of As reactive transport. The results indicated that the heterogeneous system significantly accelerated downward (vertical direction) As migration as a coupled effect of physical and chemical heterogeneity that led to fast As transport with low As sorption along the preferential flow paths. The results also indicated that such a heterogeneity effect was driven by water extraction that enhanced the downward groundwater flow along the preferential flow paths. Numerical simulations were performed by matching the experimental results to provide insights into the dominant processes controlling the As migration in the heterogeneous systems. The simulation results highlighted the importance of the kinetic oxidation of mineral-bonded Fe(II) to Fe(III) in the clay matrix that dynamically increased As sorption affinity and retarded As reactive transport. A coupled model of reactive transport along the preferential flow paths, sorption-retarded diffusion from the preferential flow paths into the clay matrixes, and reactions that change sorption affinity in the matrix was required to describe the As reactive transport systems with physico-chemical heterogeneities. The results have strong implications for understanding and modeling As downward migration from shallow to deep aquifers under groundwater pumping conditions in field systems with inherent heterogeneity.