Ultra-Low Level Somatic Mutations and Structural Variations in Focal Cortical Dysplasia Type II.

OBJECTIVE: Brain somatic mutations in mTOR pathway genes are a major genetic etiology of focal cortical dysplasia type II (FCDII). Despite a greater ability to detect low-level somatic mutations in the brain by deep sequencing and analytics, about 40% of cases remain genetically unexplained. METHODS: We included 2 independent cohorts consisting of 21 patients with mutation-negative FCDII without apparent mutations on conventional deep sequencing of bulk brain. To find ultra-low level somatic variants or structural variants, we isolated cells exhibiting phosphorylation of the S6 ribosomal protein (p-S6) in frozen brain tissues using fluorescence-activated cell sorting (FACS). We then performed deep whole-genome sequencing (WGS; >90×) in p-S6+ cells in a cohort of 11 patients with mutation-negative. Then, we simplified the method to whole-genome amplification and target gene sequencing of p-S6+ cells in independent cohort of 10 patients with mutation-negative followed by low-read depth WGS (10×). RESULTS: We found that 28.6% (6 of 21) of mutation-negative FCDII carries ultra-low level somatic mutations (less than 0.2% of variant allele frequency [VAF]) in mTOR pathway genes. Our method showed ~34 times increase of the average mutational burden in FACS mediated enrichment of p-S6+ cells (average VAF = 5.84%) than in bulky brain tissues (average VAF = 0.17%). We found that 19% (4 of 21) carried germline structural variations in GATOR1 complex undetectable in whole exome or targeted gene sequencing. CONCLUSIONS: Our method facilitates the detection of ultra-low level somatic mutations, in specifically p-S6+ cells, and germline structural variations and increases the genetic diagnostic rate up to ~80% for the entire FCDII cohort. ANN NEUROL 2023;93:1082-1093.

A case report of isolated orbital vasculitis mimicking retinal migraine: A potential cause of recurrent transient monocular blindness and ipsilateral headache.

BACKGROUND: Retinal migraine is an important differential diagnosis of recurrent transient monocular blindness accompanied by headache when other etiologies are excluded. Here, we report a case of orbital vasculitis which initially mimicked retinal migraine. CASE REPORT: A 47-year-old woman had recurrent episodes of fully reversible transient monocular blindness accompanied by ipsilateral headache for 15 months. The patient's neuroimaging and cardiac and ophthalmologic evaluations were normal. With a diagnosis of retinal migraine, her symptoms remitted in response to prophylactic treatment with topiramate and propranolol for 8 months. Three months after discontinuation of medications, transient monocular blindness recurred. High-resolution vessel wall magnetic resonance imaging revealed enhancement of the ipsilateral orbital vessels. Isolated orbital vasculitis was diagnosed. Complete remission of transient monocular blindness was achieved after steroid pulse therapy. DISCUSSION: Isolated orbital vasculitis should be considered in differential diagnosis of recurrent transient monocular blindness and ipsilateral headache. High-resolution vessel wall magnetic resonance imaging can be helpful for the diagnosis.

Low prevalence of mupirocin resistance in Staphylococcus pseudintermedius isolates from canine pyoderma in Korea.

BACKGROUND: Mupirocin is a topical antibacterial drug used for the treatment of staphylococcal infections, including meticillin-resistant Staphylococcus pseudintermedius (MRSP). The recent emergence of resistance to mupirocin is a major concern in many countries. OBJECTIVES: This study investigated the prevalence and genotype of mupirocin-resistant S. pseudintermedius isolated from pet dogs with pyoderma. SAMPLES: A total of 110 clinical isolates of S. pseudintermedius were collected from dogs with pyoderma (n = 110) between July 2010 and September 2016. All animals were client-owned dogs. METHODS: Low- and high-level mupirocin resistance were evaluated with both the broth microdilution and disk diffusion tests. Mupirocin resistance in S. pseudintermedius isolates was confirmed by genetic analysis of the ileS-2 and naïve ileS genes. RESULTS: MRSP and meticillin-susceptible S. pseudintermedius were detected in 69 and 41 dogs, respectively. One MRSP strain was highly resistant to mupirocin and contained the high-level mupirocin resistance gene ileS-2. There were no low-level mupirocin-resistant isolates. CONCLUSION AND CLINICAL IMPORTANCE: Mupirocin is a useful topical antibacterial for MRSP, but a clinical MRSP isolate that had not previously been exposed to mupirocin exhibited the high-level mupirocin resistance in phenotype and genotype. Therefore, continuous monitoring for mupirocin resistance is important in small animal practice.

CO2 Outgassing from an Urbanized River System Fueled by Wastewater Treatment Plant Effluents.

Continuous underway measurements were combined with a basin-scale survey to examine human impacts on CO2 outgassing in a highly urbanized river system in Korea. While the partial pressure of CO2 (pCO2) was measured at 15 sites using syringe equilibration, 3 cruises employing an equilibrator were done along a 30 km transect in the Seoul metropolitan area. The basin-scale survey revealed longitudinal increases in surface water pCO2 and dissolved organic carbon (DOC) in the downstream reach. Downstream increases in pCO2, DOC, fluorescence index, and inorganic N and P reflected disproportionately large contributions from wastewater treatment plant (WWTP) effluents carried by major urban tributaries. Cruise transects exhibited strong localized peaks of pCO2 up to 13 000 µatm and 13CO2 enrichment along the confluences of tributaries at an average flow, whereas CO2 pulses were dampened by increased flow during the monsoon period. Fluctuations in pCO2 along the eutrophic reach downstream of the confluences reflected environmental controls on the balance between photosynthesis, biodegradation, and outgassing. The results underscore WWTP effluents as an anthropogenic source of nutrients, DOC, and CO2 and their influences on algal blooms and associated C dynamics in eutrophic urbanized river systems, warranting further research on urbanization-induced perturbations to riverine metabolic processes and carbon fluxes.

Decreased Bone Volume and Bone Mineral Density in the Tibial Trabecular Bone Is Associated with Per2 Gene by 405 nm Laser Stimulation.

Low-level laser therapy/treatment (LLLT) using a minimally invasive laser needle system (MILNS) might enhance bone formation and suppress bone resorption. In this study, the use of 405 nm LLLT led to decreases in bone volume and bone mineral density (BMD) of tibial trabecular bone in wild-type (WT) and Per2 knockout (KO) mice. Bone volume and bone mineral density of tibial trabecular bone was decreased by 405 nm LLLT in Per2 KO compared to WT mice at two and four weeks. To determine the reduction in tibial bone, mRNA expressions of alkaline phosphatase (ALP) and Per2 were investigated at four weeks after 405 nm laser stimulation using MILNS. ALP gene expression was significantly reduced in the LLLT-stimulated right tibial bone of WT and Per2 KO mice compared to the non-irradiated left tibia (p < 0.001). Per2 mRNA expression in WT mice was significantly reduced in the LLLT-stimulated right tibial bone compared to the non-irradiated left tibia (p < 0.001). To identify the decrease in tibial bone mediated by the Per2 gene, levels of runt-related transcription factor 2 (Runx2) and ALP mRNAs were determined in non-irradiated WT and Per2 KO mice. These results demonstrated significant downregulation of Runx2 and ALP mRNA levels in Per2 KO mice (p < 0.001). Therefore, the reduction in tibial trabecular bone resulting from 405 nm LLLT using MILNS might be associated with Per2 gene expression.

Water extract of the fruits of Alpinia oxyphylla inhibits osteoclast differentiation and bone loss.

BACKGROUND: Excessive bone resorption by osteoclasts causes pathological bone destruction, seen in various bone diseases. There is accumulating evidence that certain herbal extracts have beneficial effects on bone metabolism. The fruits of Alpinia oxyphylla has been traditionally used for the treatment of diarrhea and enuresis. In this study, we investigated the effects of water extract of the fruits of Alpinia oxyphylla (WEAO) on osteoclast differentiation and osteoclast-mediated bone destruction. METHODS: For osteoclast differentiation assay, mouse bone marrow-derived macrophages (BMMs) were cultured in the presence of RANKL and M-CSF. RANKL signaling pathways and gene expression of transcription factors regulating osteoclast differentiation were investigated by real-time PCR and Western blotting. A constitutively active form of NFATc1 was retrovirally transduced into BMMs. Bone resorbing activity of mature osteoclast was examined on a plate coated with an inorganic crystalline calcium phosphate. The in vivo effect against bone destruction was assessed in a murine model of RANKL-induced osteoporosis by micro-computed tomography and bone metabolism marker analyses. RESULTS: WEAO dose-dependently inhibited RANKL-induced osteoclast differentiation from BMMs by targeting the early stages of osteoclast differentiation. WEAO inhibited RANKL-induced expression of NFATc1, the master regulator of osteoclast differentiation. Overexpression of a constitutively active form of NFATc1 blunted the inhibitory effect of WEAO on osteoclast differentiation, suggesting that NFATc1 is a critical target of the inhibitory action of WEAO. WEAO inhibited RANKL-induced expression of c-Fos, an upstream activator of NFATc1, by suppressing the classical NF-κB signaling pathway. WEAO also inhibited RANKL-induced down-regulation of Id2 and MafB, negative regulators of NFATc1. WEAO does not directly affect bone resorbing activity of mature osteoclasts. In accordance with the in vitro results, WEAO attenuated RANKL-induced bone destruction in mice by inhibiting osteoclast differentiation. CONCLUSIONS: This study demonstrates that WEAO exhibits a protective effect against bone loss by inhibiting RANKL-induced osteoclast differentiation. These findings suggest that WEAO might be useful for the prevention and treatment of bone diseases associated with excessive bone resorption.

Optical and molecular indices of dissolved organic matter for estimating biodegradability and resulting carbon dioxide production in inland waters: A review.

Biodegradable dissolved organic carbon (BDOC) constitutes the most labile fraction of dissolved organic matter (DOM), which also functions as a source of CO2 emissions from inland waters. However, no systematic review is available on DOM indicators of BDOC and CO2 production potential. Optical and molecular indices can be used to track small changes in DOM composition during biodegradation. In this review, we identified four different methods for measuring BDOC together with their strengths and limitations. In addition, we discuss the potential of using documented optical indices based on absorption and fluorescence spectroscopy and molecular indices based on Fourier transform ion cyclotron mass spectrometry as proxies for estimating BDOC and biodegradation-induced CO2 production based on previously reported relationships in the literature. Many absorbance- and fluorescence-based indices showed inconsistent relationships with BDOC depending on watershed characteristics, hydrology, and anthropogenic impacts. Nevertheless, several indices, including specific UV absorbance at 254 nm (SUVA254), humification index (HIX), and terrestrial humic-like fluorescent DOM (FDOM) components, tended to have negative relationships with BDOC in tropical and temperate watersheds under baseflow or drought periods. Protein-like FDOM exhibited the strongest correlation with BDOC in different systems, except during storms and flood events. Despite the limited number of studies, DOM molecular indices exhibited consistent relationships with BDOC, suggesting that the relative abundance of aliphatic formulas and the molecular lability index could act as reliable proxies. The DOM optical indices explain up to 96% and 78% variability in BDOC and CO2, respectively; nonetheless, there were limited studies on molecular indices, which explain up to 74% variability in BDOC. Based on literature survey, we recommend several sensitive indices such as SUVA254, HIX, and terrestrial humic- and protein-like FDOM, which could be useful indicators of BDOC and dissolved CO2 in inland water. Future research should incorporate a wider range of geographic regions with various land use, hydrology, and anthropogenic disturbances to develop system- or condition-specific DOM optical or molecular proxies for better prediction of BDOC and CO2 emissions.

Basin-specific pollution and impoundment effects on greenhouse gas distributions in three rivers and estuaries.

Large uncertainties exist regarding the combined effects of pollution and impoundment on riverine greenhouse gas (GHG) emissions. It has also been debated whether river eutrophication can transform downstream estuaries into carbon sinks. To assess human impacts on the riverine and estuarine distributions of CO2, CH4, and N2O, two source-to-estuary surveys along three impounded rivers in Korea were combined with multiple samplings at five or six estuarine sites. The basin-wide surveys revealed predominant pollution effects generating localized hotspots of riverine GHGs along metropolitan areas. The localized pollution effect was pronounced in the lower Han River and estuary adjacent to Seoul, while the highest GHG levels in the upper Yeongsan traversing Gwangju were not carried over into the faraway estuary. CH4 levels were elevated across the eutrophic middle Nakdong reaches regulated by eight cascade weirs in contrast to undersaturated CO2 indicating enhanced phytoplankton production. The levels of all three GHGs tended to be higher in the Han estuary across seasons. Higher summer-time δ13C-CH4 values at some Nakdong and Yeongsan estuarine sites implied that temperature-enhanced CH4 production may have been dampened by increased CH4 oxidation. Our results suggest that the location and magnitude of pollution sources and impoundments control basin-specific longitudinal GHG distributions and estuarine carryover effects, warning against simple generalizations of eutrophic rivers and estuaries as carbon sinks.

Does Medicaid expansion influence county health spending? A case of New York counties.

We investigated the impacts of Medicaid expansion on New York county total health spending and specifics of health spending, including health services, public health facilities and public health administration. Little research considered the financial effect of Medicaid expansion on local governments while well reported are its influences on uninsured rates and health services utilization. New York counties have contributed to health in their boundaries by providing or funding public health services, and supporting a part of the non-federal share of Medicaid expenditures and uncompensated care. Medicaid expansion can reduce the size of county expenditures for health by enrolling more previously uninsured population in the program and offering more generous federal funding for the expanded Medicaid. We offer empirical evidence that Medicaid expansion was associated with reduced county health spending.

Behavioral Reserve in Behavioral Variant Frontotemporal Dementia.

"Reserve" refers to the individual clinical differences in response to a neuropathological burden. We explored the behavioral reserve (BR) and associated neural substrates in 40 participants with behavioral variant frontotemporal dementia (bvFTD) who were assessed with the frontal behavioral inventory (FBI) and magnetic resonance imaging. Because neuroimaging abnormality showed a high negative correlation with the FBI negative (but not positive) symptom scores, we developed a linear model only to calculate the nBR (BR for negative symptoms) marker using neuroimaging abnormalities and the FBI score. Participants were divided into high nBR and low nBR groups based on the nBR marker. The FBI negative symptom score was lower in the high nBR group than in the low nBR group having the same neuroimaging abnormalities. However, the high nBR group noted a steeper decline in cortical atrophy and showed less atrophy in the left frontotemporal cortices than the low nBR group. In addition, the fractional anisotropy (FA) values were greater in the high nBR than in the low nBR group, except in the sensory-motor and occipital areas. We identified an nBR-related functional network composed of bilateral frontotemporal areas and the left occipital pole. We propose the concept of BR in bvFTD, and these findings can help predict the disease progression.

Reassessing riverine carbon dioxide emissions from the Indian subcontinent.

Anthropogenic perturbations are increasing uncertainties in estimating CO2 emissions via air-water CO2 flux (FCO2) from large rivers of the Indian subcontinent. This study aimed to provide an improved estimate of the total FCO2 from the subcontinental rivers by combining calculations of the partial pressure of CO2 (pCO2) in eight major rivers with new measurements in the Ganges and Godavari. The average pCO2 in the two newly surveyed rivers, including tributaries, wastewater drains, and impoundments, were 3-6 times greater than the previously reported values. In some highly polluted urban tributaries and middle reaches of the Ganges that drain metropolitan areas, the measured pCO2 exceeded 20,000 µatm, ~40 times the background levels of the headwaters originating in the carbonate-rich Himalayas. The high pCO2 above 28,000 µatm in the lower reach of the Godavari was seven times the moderate levels of pCO2 in the headwaters of the volcanic Deccan Traps, indicating enhanced CO2 production in soils and anthropogenic sources under favorable conditions for organic matter degradation. Across the northern rivers, pCO2 exhibited a significant negative relationship with dissolved oxygen, but a positive relationship with inorganic N or P concentrations. The strong influence of water pollution on riverine pCO2 suggests that CO2 emissions from hypoxic, eutrophic reaches can greatly exceed phytoplanktonic CO2 uptake. Spatially resolved pCO2 data, combined with three gas transfer velocity estimates, provided a higher range of FCO2 from the subcontinental rivers (100.9-130.2 Tg CO2 yr-1) than the previous estimates (7.5-61.2 Tg CO2 yr-1). The revised estimates representing 2-5% of the global riverine FCO2 illustrate the importance of the Indian subcontinental rivers under increasing anthropogenic pressures in constraining global inland waters FCO2.

Generalised autonomic failure as a prognostic factor in systemic light-chain (AL) amyloidosis.

BACKGROUND: In the present study, it was investigated whether autonomic dysfunction could predict prognosis in light-chain (AL) amyloidosis patients. PATIENTS AND METHODS: Seventy-two patients with biopsy-proven AL amyloidosis were included and underwent an autonomic function test (AFT) between January 2016 and June 2019. Autonomic failure was evaluated using the Composite Autonomic Severity Score (CASS). Survival curves and the three-year overall survival (OS) rate were estimated using the Kaplan-Meier curve, and the Cox proportional hazards regression method was used to evaluate the variables that influenced survival. RESULTS: Autonomic dysfunction was observed in 69 (96%) patients with AL amyloidosis, and the three-year OS rate was 67%. Generalised autonomic failure (GAF) was observed in 31 (43%) patients. In the Kaplan-Meier curve, the three-year OS rates in patients with sudomotor dysfunction or GAF were lower than that in control patients (35 vs. 84%, and 33 vs. 81%, respectively). In Cox proportional hazards regression model, female, bone marrow plasma cell percentage, left ventricular systolic dysfunction, and GAF were significant independent variables associated with survival. CONCLUSION: The results of this study indicate that GAF on the AFT is an independent adverse prognostic factor for survival in AL amyloidosis patients.

NUDT15 intermediate metabolisers are associated with lower loss of response in paediatric Crohn's disease patients treated by combination treatment with infliximab and azathioprine.

BACKGROUND: NUDT15 polymorphisms are associated with leukopenia during treatment with thiopurines. However, data regarding its effect on treatment outcomes are scarce. AIMS: To investigate the outcomes between NUDT15 normal and intermediate metabolisers in paediatric patients with Crohn's disease (CD) treated with a combination therapy of infliximab (IFX) and azathioprine (AZA). METHODS: In this retrospective observational study, 143 patients categorised into the NUDT15 normal and intermediate metaboliser groups were compared based on clinical remission (CR), biochemical remission (BR), mucosal healing (MH) at 1 year treatment, IFX trough levels (TLs), antibodies to IFX (ATIs), 6-thioguanine nucleotide (6-TGN) levels, loss of response (LOR) and IFX durability. RESULTS: No significant differences were observed between the groups in CR, BR, MH at 1 year, whereas IFX TLs and ATIs and 6-TGN levels were comparable. However, LOR (6.5% vs 27.7%, P = 0.025) was significantly lower and IFX durability significantly higher (96.8% vs 80.4% P = 0.027) in the intermediate group. Multivariable Cox proportional hazard regression analysis showed that ATI positivity (hazard ratio (HR): 4.76, 95% CI: 2.25-10.07, P < 0.001) and the NUDT15 metaboliser group was associated with LOR (HR: 0.18, 95% CI: 0.04-0.76, P = 0.019). The Kaplan-Meier survival curves showed that the LOR-free survival rate was significantly lower in normal metabolisers (log-rank test P = 0.009). CONCLUSION: NUDT15 intermediate metabolisers were associated with lower LOR in paediatric patients with CD treated with IFX and AZA combination therapy. This finding may partially explain the longer durability of IFX in Korean children than their counterparts in Western countries.

Comparison between Pediatric Crohn's Disease and Ulcerative Colitis at Diagnosis in Korea: Results from a Multicenter, Registry-Based, Inception Cohort Study.

Background/Aims: We aimed to compare the differences in pediatric Crohn's disease (CD) and ulcerative colitis (UC) at diagnosis in Korea. Methods: This was a multicenter, registry-based, inception cohort study conducted at five centers in Korea between 2013 and 2017. Baseline demographics, clinical characteristics, and results from laboratory, endoscopic, radiologic examinations were compared between pediatric CD and UC patients who were <19 years old at diagnosis. Results: A total 307 patients were included (227 CD [73.9%] and 80 UC [26.1%]). The male to female ratio was 2.49:1 for CD, and 1.49:1 for UC (p=0.019). Median age at diagnosis was 14.4 years (interquartile range, 12.4 to 16.2) for CD, and 14.4 years (interquartile range, 11.7 to 16.5) for UC (p=0.962). Hematochezia was the only dominant symptom in UC patients compared to CD patients (86.2% vs 30.8%, p<0.001). White blood cell counts, platelet counts, erythrocyte sedimentation rate, and C-reactive protein levels were significantly higher, and serum albumin level was significantly lower in CD patients than in UC patient. Anti-Saccharomyces cerevisiae antibody was positive in 44.5% and 16.2% of CD and UC patients, respectively (p<0.001), and antineutrophil cytoplasmic antibody was positive in 15.0% and 58.8% of CD and UC patients, respectively (p<0.001). Terminal ileal involvement was prominent in CD, while rectal involvement was more prominent in UC. Small bowel involvement and perianal perforating diseases were also more prominent in CD. Conclusions: This is the first a multicenter study in Korea to compare the differences between pediatric CD and UC at diagnosis in Korea. A large-scale, national study is expected to better clarify these findings in the future.

State strategies to address medicaid prescription spending: negotiated pricing vs price transparency.

This research longitudinally examines the association between levels of state Medicaid prescription spending and the state strategies intended to constrain cost increases: the negotiated pricing strategy, as indicated by state rebate programs, and the price transparency strategy, as indicated by state operation of All-Payer Claims Databases. The findings demonstrate evidence that state Medicaid prescription spending is influenced by the negotiated pricing strategy, especially Managed Care Organization (MCO) rebates under the Patient Protection and Affordable Care Act, but not influenced by the price transparency strategy. State decisions for MCO rebates, such as carving prescription benefits into managed care benefits, were effective in containing levels of Medicaid prescription spending over time, while other single- and multi-state rebate programs were not. Based on these findings, state policymakers may consider utilizing the MCO rebate program to address increases in Medicaid prescription spending.

Pediatric Crohn's disease with severe morbidity manifested by gastric outlet obstruction: two cases report and review of the literature.

Crohn's disease (CD) presenting as gastric outlet obstruction is rare but serious clinical presentation of CD causing severe morbidity. However, there have been few case reports concerning this disorder in East Asian children and adolescents. The current case report describes 2 pediatric patients with CD who had had gastric outlet obstruction as an initial symptom of CD. Two pediatric patients developed postprandial vomiting, bloating, and unintentional weight loss. The upper endoscopy result indicated that there was pyloric obstruction with mucosal edema, inflammation and ulcers. The serologic test and colonoscopy results suggested CD. These patients were treated with infliximab, and endoscopic balloon dilation without surgery and showed remarkable improvement in obstructing symptoms with maintaining clinical and biochemical remission. This case report elucidates the benefits of early intervention using infliximab and endoscopic balloon dilation to improve gastric outlet obstruction and achieve baseline recovery in patients with upper gastrointestinal B2 phenotype of CD.

Phytoplankton nutrient use and CO2 dynamics responding to long-term changes in riverine N and P availability.

Long-term trends in riverine nutrient availability have rarely been linked to both phytoplankton composition and functioning. To explore how the changing availability of N and P affects not only phytoplankton abundance and composition but also the resource use efficiency of N, P, and CO2, a 25-year time series of water quality in the lower Han River, Korea, was combined with additional measurements of riverine dissolved organic carbon (DOC) and CO2. Despite persistent eutrophication, recent decreases in P relative to N have been steep in the lowest reach, increasing the annual mean mass ratio of N to P (N/P) from 24 (1994-2015) to 65 (2016-2018). While Chl a and cyanobacterial abundance exhibited overall positive and inverse relationships with P concentrations and N/P, respectively, severe harmful algal blooms (HABs) concurred with short-term increases in P and temperature. Microcystis often dominated HABs at low N/P that usually favors N-fixing cyanobacteria such as Anabaena. In the middle and lower reaches, phytoplanktonic P use efficiency was typically lower at low N/P. V-shaped relationships between N/P and CO2 concentrations, together with longitudinal upward shifts in the inverse relationship between Chl a and CO2, implied that eutrophication-enhanced phytoplankton biomass could turn into a significant source of CO2. after passing a threshold. The combined results suggest that cyanobacterial dominance co-limited by P availability and temperature can lower planktonic P use efficiency, while enhancing riverine CO2 emissions at low N/P ratios.

Rapid release and changing sources of Pb in a mountainous watershed during extreme rainfall events.

Although atmospheric Pb is known to accumulate in forest soils over time, little is known about the hydrologic Pb export from mountain forest soils. Short-term changes in Pb release and its sources during monsoon rainfall events were investigated in a mountainous watershed in the northern extreme of South Korea by combining intensive storm sampling with measurements of Pb concentrations and isotope ratios in soils and size-fractionated sediments. Biweekly monitoring of forest and agricultural streams showed relatively low dissolved Pb concentrations compared to those found in precipitation. Particulate Pb concentrations in both streams were higher than the dissolved concentrations and increased rapidly during rainfall events. Particulate Pb concentrations were substantially higher in the agricultural stream; the highest concentrations were associated with silt-size sediment followed by sand. A comparison of (206)Pb/(207)Pb and (208)Pb/(206)Pb among sediment fractions and source soils indicated that major sources for silt- and sand-associated Pb in the agricultural stream change between streambank and cropland soils, whereas Pb in the forest stream is primarily derived from forest floors. The results suggest that Pb isotopes can be efficiently applied to tracing short-term changes in sediment and Pb sources and that extreme rainfall events can significantly increase Pb mobilization from erosion-prone mountain soils.

Temperature control on wastewater and downstream nitrous oxide emissions in an urbanized river system.

Although eutrophic urban rivers receiving loads of wastewater represent an important anthropogenic source of N2O, little is known as to how temperature and other environmental factors affect temporal variations in N2O emissions from wastewater treatment plants (WWTPs) and downstream rivers. Two-year monitoring at a WWTP and five river sites was complemented with available water quality data, laboratory incubations, and stable isotopes in N2O and NO3- to explore how wastewater effluents interact with seasonal changes in environmental conditions to affect downstream metabolic processes and N2O emissions from the lower Han River traversing the megacity Seoul. Water quality data from four WWTPs revealed significant inverse relationships between water temperature and the concentrations or fluxes of total N (TN) in effluents. Increased TN fluxes at low temperatures concurred with N2O surges in WWTP effluents and downstream rivers, counteracting the long-term decline in TN fluxes resulting from enhanced wastewater treatments. Incubation experiments with river water and sediment, in isolation or combined, implied the hypoxic winter sediment as a large source of N2O, whereas the anoxic summer sediment produced a smaller amount of N2O only when it was added with oxic water. For both WWTP effluents and downstream rivers, bulk isotope ratios and intramolecular distribution of 15N in N2O distinctly differed between summer and winter, indicating incomplete denitrification in the hypoxic sediment at low temperatures as a primary downstream source adding to WWTP-derived N2O. Winter surges in wastewater TN and sediment N2O release highlight temperature variability as an underappreciated control over anthropogenic N2O emissions from increasingly urbanized river systems worldwide.

Variability of water quality and metal pollution index in the Ganges River, Bangladesh.

The Ganges River is one of the biggest transboundary streams in the Indian sub-continent. The significant part of this waterway channel drains one of the most densely populated areas on the planet so it is unequivocally influenced by human activities. Unprecedented high-temporal-resolution samples were collected for investigating the seasonal variability of water quality. Water quality index (WQI) reveals large seasonal variation among three major seasons and also indicates that the river water is not suitable for drinking and other household uses. The dominant water facies is bicarbonate (HCO3-). The water quality indices, %Na, Kelley's ratio (KR), sodium adsorption ratio (SAR), and magnesium adsorption ratio (MAR), reveal that the water is appropriate for irrigation. The permeability index (PI) indicated that the water is moderate to poorly useable for agricultural purposes. Heavy metals concentrations demonstrated significant seasonal variations with high concentrations during the monsoon due to flushing of pollutants from catchment areas by intense monsoonal precipitations. In addition, local activities such as oil spills from the boat, vehicle washing water, and agricultural runoff may also added pollutants. The single-factor pollution index (Ii) and Nemerow pollution index (Ni) exhibits minor pollution. The values of heavy metal pollution index (HPI) are far below than the critical limit (100) for the studied month, although relatively higher HPI values found for April, August, and November than other months might come from domestic wastes and agricultural activities. The heavy metal evaluation index (HEI) values of all the months indicated a low degree of pollution. Even though the river water pollution level is low, the authority should take proper management and monitoring strategy for sustainable use.