Hydrochemistry and nutrients determined the distribution of greenhouse gases in saline groundwater

The geography patterns and generation mechanisms of greenhouse gases (GHGs) in groundwater, especially in saline groundwater, are critical but rarely studied. Herein, we investigated the GHGs distribution in an aquifer, located upstream of Baiyangdian Lake, China, with a distinctive salinity gradient. A total of 132 groundwater samples were collected from 44 new-constructed wells along the lateral dimensions, and analyzed for dissolved GHGs concentrations, physiochemical parameters, and isotopes. The results showed that the dissolved CO₂, CH₄ and N₂O concentrations ranged from 9.47 to 79.3 mg/L, 1.05-56.9 μg/L, and 0.84-7.03 μg/L, respectively. The groundwater was supersaturated with GHGs with respect to atmospheric equilibrium, suggesting groundwater discharge as a potential source of GHGs emission. CO₂ significantly decreased while CH₄ and N₂O distinctively increased with the decline of total dissolved solids (TDS) concentration, illustrating an obvious spatial pattern in the GHGs distribution. The CO₂ distributions mainly depended on the bicarbonate radical and TDS, indicating carbonate equilibrium as the main process involving in the CO₂ generation. CH₄ and N₂O was primarily generated through the methanogenesis and denitrification processes, respectively. Nutrients including SO₄^2- and total organic carbon predominately shaped the CH₄ distributions, while nitrate mainly governed the N₂O distributions. Our study highlights the important roles of hydrochemistry and nutrients in the GHGs generation and distributions, which provides a significant insight on managing the GHGs emissions from the saline groundwater.

Differences in quinone redox system of humic substances between endemic and disease-free areas in Kashin-Beck disease-affected Changdu Region, Tibet, China

Kashin-Beck disease (KBD) is an endemic disease in China with the highest incidence rate in Tibet region. Promoted generation of oxygen free radicals by semiquinone structure of humic substance (HS) in drinking water was considered to be one of its pathogeneses. Therefore, detailed analysis of HS was performed in water and sediment samples collected from three endemic and three disease-free areas in Changdu Region, Tibet, China. After purification of the HS in the samples, the fractions of HS were characterized using electron paramagnetic resonance, ¹³C nuclear magnetic resonance, fluorescence spectroscopy with parallel factor analysis and Fourier transform infrared spectroscopy (FTIR). The organic carbon content of HS did not show a significant difference between endemic and disease-free areas or correlation with KBD-associated morbidity. Except FTIR, all techniques succeeded in characterization of the quinone redox system, indicating their validity and consistency. The quinone redox system in aquatic HS exhibited significantly higher level of the following indexes in endemic areas than disease-free areas: semiquinone radical content of fulvic acid (FA) (p < 0.05), aromaticity of FA (p < 0.05), fluorescence intensity (per gram carbon) of reduced quinone-like component of FA (p < 0.05) and humic acid (HA) (p < 0.1). Semiquinone radical content (r = 0.781, p < 0.1), aromaticity of FA (r = 0.891, p < 0.05), intensity of oxidized quinone-like component (r = 0.875, p < 0.05) and reduced quinone-like component of FA (r = 0.793 p < 0.1) showed medium to strong correlation with KBD-associated morbidity. Generally, the content of reduced quinone and aquatic FA showed stronger differences between endemic and disease-free areas than oxidized quinone and aquatic HA, respectively. The quinone redox system in sediment HS did not show any significant relationship with KBD. The present study is a successful attempt to combine the three indexes, semiquinone radical content, aromaticity and fluorescence intensity, in characterizing quinone redox system in HS, facilitating more comprehensive understanding of the characteristics of HS in KBD-affected regions.

In-situ expressions of comammox Nitrospira along the Yangtze River

The recent discovery of comammox Nitrospira as complete nitrifiers has significantly enriched our understanding on the nitrogen cycle, yet little is known about their metabolic transcripts in natural aquatic ecosystems. Using the genome-centric metatranscriptomics, we provided the first in-situ expression patterns of comammox Nitrospira along the Yangtze River. Our study confirmed widespread expressions of comammox Nitrospira, with the highest transcription accounting for 33.3% and 63.8% of amoA and nxrAB genes expressed in ammonia-oxidizing prokaryotes (AOPs) and Nitrospira sublineages I/II, respectively. Moreover, comammox two clades differed in nitrification, with clade A acting as the dominator to ammonia oxidation in comammox, and clade B contributing more transcripts to nitrite oxidation than to ammonia oxidation. Compared to canonical Nitrospira, comammox community had lower expressions of ammonia/nitrite transporters and nitrogen assimilatory genes, but far higher expressions in urea transport and hydrolysis, facilitating to derivation of ammonia and energy mainly through intracellular ureolytic metabolism. This suggests no need for "reciprocal-feeding" between canonical Nitrospira and AOPs in a natural river. Aerobic mixotrophy of comammox bacteria was suggested by expressions of genes coding for respiratory complexes I-V, oxidative/reductive TCA cycle, oxygen stress defenses, and transport/catabolism of simple carbohydrates and low-biosynthetic-cost amino acids. Intriguingly, significant positive correlations among expressions of ammonia monooxygenases, hydroxylamine dehydrogenase and copper-dependent nitrite reductase indicated that comammox Nitrospira had the potential of converting nitrite to nitric oxide accompanied by ammonia oxidation under low-C/N and aerobic conditions, while gene expressions in this pathway were significantly and positively associated with pH. Overall, this study illustrated novel transcriptional characteristics of comammox Nitrospira, and highlighted the necessity of reassessing their contributions to biogeochemical carbon and nitrogen cycling with perspective of in-situ meta-omics as well as culture experiments.

Flagella and Their Properties Affect the Transport and Deposition Behaviors of Escherichia coli in Quartz Sand

The effects of flagella and their properties on bacterial transport and deposition behaviors were examined by using four types of Escherichia coli (E. coli) with or without flagella, as well as with normal or sticky flagella. Packed column, quartz crystal microbalance with dissipation, visible parallel-plate flow chamber system, and visible flow chamber packed with porous media system were employed to investigate the deposition mechanisms of bacteria with different properties of flagella. We found that the presence of flagella favored E. coli deposition onto quartz sand/silica surfaces. Moreover, by changing the porous media porosity and directly observing the bacterial deposition process, local sites with high roughness, narrow flow channels, and grain-to-grain contacts were found to be the major sites for bacterial deposition. Particularly, flagella could help bacteria swim near and then deposit at these sites. In addition, we found that due to the stronger adhesive forces, sticky flagella could further enhance bacterial deposition onto quartz sand/silica surfaces. Elution experiments indicated that flagella could help bacteria attach onto sand surfaces more irreversibly. Clearly, flagella and their properties would have obvious impacts on the transport/deposition behaviors of bacteria in porous media.

Metabolic syndrome cannot mask the changes of faecal microbiota compositions caused by primary hepatocellular carcinoma

Both hepatocellular carcinoma (HCC) and metabolic syndrome are closely associated with the composition of the gut microbiota (GM). Although it has been proposed that elements of the GM can be used as biomarkers for the early diagnosis of HCC, whether metabolic syndrome results in a misrepresentation of the results of the early diagnosis of HCC using GM remains unclear. We compared the differences in the faecal microbiota of 10 patients with primary HCC, six patients with type 2 diabetes mellitus (T2DM), seven patients with arterial hypertension, six patients with both HCC and T2DM, and 10 patients with both HCC and arterial hypertension, as well as 10 healthy subjects, using high-throughput sequencing of 16S rRNA gene amplicons. Our results revealed a significant difference in the GM between subjects with and without HCC. The 49 bacterial genera out of the 494 detected genera were significantly different between the groups. These results show that changes in the GM can be used to distinguish between subjects with and without HCC, and can resist interference of T2DM and arterial hypertension with the GM. The results of the present study provide an important basis for the clinical auxiliary diagnosis of HCC by detecting the GM.

[The role of Artificial intelligent-based FFRCT in assessing the hemodynamic relevance of deep myocardial bridge of the left anterior descending coronary artery]

Objective: To investigate the role of artificial intelligence-based coronary CT blood flow reserve score (FFR_CT) in assessing hemodynamic relevance in patients with deep myocardial bridge (MB) of the left anterior descending coronary artery. Methods: A total of 113 patients diagnosed with deep MB of the left anterior descending coronary artery by coronary CT angiography (CCTA) at the Department of Radiology of Tongji Hospital Affiliated to Tongji University from January 2017 to December 2019 were retrospectively analyzed. The location, length, depth, and degree of systolic compression of the MB were measured. The artificial intelligence-based coronary FFR_CT software was employed to calculate the FFR_CT value of the deep MB of the left anterior descending coronary artery. With the boundary of 0.80, all patients were divided into FFR_CT normal group (FFR_CT>0.80) and FFR_CT abnormal group (FFR_CT≤0.80), and the relationship between FFR_CT abnormality and the location, length, depth, and degree of systolic stenosis of the deep MB of the left anterior descending branch was analyzed. The effectiveness of the receiver operating characteristic (ROC) curve in predicting FFR_CT abnormalities was measured by using ROC curve to analyze the length, depth, and degree of systolic stenosis of MB. Results: There were no significant differences in age, gender and high-risk factors between FFR_CT normal group (n=79) and FFR_CT abnormal group (n=34) (P>0.05). In terms of clinical symptoms, unstable angina, asymptomatic myocardial ischemia, stable angina in the FFR_CT normal group were 15.2%, 41.8%, 32.9%,respectively, while 32.4%, 23.5%, 35.3% in the FFR_CT abnormal group,respectively. Except for unstable angina (χ²=4.32,P=0.038), there were no significant differences in asymptomatic myocardial ischemia and stable angina between the two groups (χ²=3.42, 0.06, P>0.05). The length of deep MB was about (36±5) mm in the FFR_CT normal group and (44±5) mm in the FFR_CT abnormal group, respectively. The difference between the two groups was statistically significant (t=-7.703, P<0.001). The ROC curve showed that the optimal critical value of the length of the deep MB was 39.7 mm, the area under the curve was 0.88 (95%CI:0.81-0.95, P<0.001), and the accuracy rate of diagnosing FFR_CT ≤0.80 was 82.3%. Conclusion: FFR_CT value is of great value in the evaluation of hemodynamics in patients with deep myocardial bridge of left anterior descending coronary artery, and the length of deep myocardial bridge is an important factor affecting FFR_CT value.

[Present and future: artificial intelligence in medical imaging]

Artificial intelligence (AI) is a hot point in clinical medicine research. In recent years, AI has played an important role in recognizing the lesion, improving the diagnostic accuracy and assessing the diagnostic efficacy. To accelerate the pace of AI industry, it should be a first thing to improve relevant industrial policies and regulations and to build a transformation platform for industry-university-research. All these will contribute to the standardization in further development of medical imaging AI industry.

Predictive Value of Serum Creatinine/Cystatin C in Acute Ischemic Stroke Patients under Nutritional Intervention

BACKGROUND AND PURPOSE

As a very common risk of adverse outcomes of the ischemic stroke patients, sarcopenia is associated with infectious complications and higher mortality. The goal of this retrospective study is to explore the predictive value of serum Cr/CysC ratio in acute ischemic stroke patients receiving nutritional intervention.

METHODS

We reviewed adult patients with AIS from December 2019 to February 2020. Patients with acute kidney injury were excluded and all patients received nutritional intervention during a 3-month follow-up period. We collected baseline data at admission including creatinine and cystatin C. The primary poor outcome was major disability (modified Rankin Scale score ≥ 4) at 3 months after AIS.

RESULTS

A total of 217 patients with AIS were identified for this study. Serum Cr/CysC ratio was significantly correlated with NIHSS at discharge, 1-month modified Rankin Scale score, and 3-month modified Rankin Scale score. During 3 months, 34 (15.70%) patients had a poor outcome after AIS and 11 (5.10%) patients died within 30 days. In multivariable logistic regression analyses, serum Cr/CysC ratio at admission was independently associated with 3-month poor outcomes (OR: 0.953, 95% CI: 0.921-0.986, p = .006) and 30-day mortality (OR: 0.953, 95% CI: 0.921-0.986, p = .006).

CONCLUSION

As a blood biochemical indexes reflecting the muscle mass and aiding in risk stratification, Cr/CysC ratio at admission could be used as a predictor of 30-day mortality and long-term poor prognosis in AIS patients.

Enrichment of antibiotics in an inland lake water

Inland water is very susceptible to the input of pollutants. However, little is known about the occurrence of antibiotics in inland lakes. In this study, a total of 83 target antibiotics were quantified in water and sediment samples collected from the Qinghai Lake, the largest inland lake of China located on the northeast of Qinghai-Tibet plateau, and its inflowing rivers. The results showed that 27 and 25 antibiotics were detected in water and sediments, respectively, with the summed concentrations (SUM) of 1.14-17.3 ng/L and 0.72-8.31 ng/g. Compared with the input rivers, significantly higher levels of sulfonamides (SAs), quinolones (QNs), polyethers (PEs), and SUM in water samples were observed in Qinghai Lake water. The average proportions of SAs (50.9-52.7%) and QNs (22.0-28.3%) in Qinghai Lake water nearly doubled compared to those in input rivers. An enrichment factor (EF) was proposed to reveal the enrichment degree of antibiotics in Qinghai Lake compared to its input river water. Sulfaguanidine (SGD), flumequine (FLU), and nalidixic acid (NDA) were enriched in Qinghai Lake up to several ten times based on the calculated EF values, due to their persistence in such a cold saline lake. Risk assessment showed that most antibiotics except anhydrochlortetracycline (ACTC) had insignificant risks to aquatic organisms and antibiotic resistance selection in Qinghai Lake water. This study was the first to reveal the enrichment of antibiotics in Qinghai Lake water, and suggests the urgent need to investigate the possible long-term enrichment and environmental risks of antibiotics in inland lakes.

Interpreting main features of the differential absorbance spectra of chlorinated natural organic matter: Comparison of the experimental and theoretical spectra of model compounds

This study compared chlorination-induced changes of the properties of natural organic matter (NOM) represented by standard humic substances and NOM present in pristine and anthropogenically-affect reservoirs, rivers, groundwater and seawater. The chlorination-induced changes of NOM properties were quantified using the differential absorbance spectra (DAS) which were processed via numeric deconvolution. Six Gaussian bands were found to comprise the DAS of all examined waters. These bands (denoted as A0, A1, A2, A3, A4 and A5, respectively) have maxima located at ca. 200, 240, 276, 316, 385 and 547 nm. The bands A1-A4 were observed in the DAS of representative model chlorinated compounds. Quantum chemical (QC) calculations were carried out to examine the intrinsic nature of these bands and electronic transitions associated with them. QC data demonstrate that bands A1 and A2 are present in almost all aromatic organic species, A3 is likely to be associated with acetophenone- and/or styrene-like groups. A4 can be attributed to the engagement of m-hydroxyaromatic and flavone-type groups typical for the polyphenolic moiety in NOM and known to be the key precursors of disinfection by-product (DBP) formation. Thus, the intensity of band A4 is predicted to be an especially strong predictor of DBP formation.

Yeast cell wall product enhanced intestinal IgA response and changed cecum microflora species after oral vaccination in chickens

The study was designed to explore the effect of a commercial yeast cell wall product (YP) on chicken intestinal IgA response and cecum microbiome after oral vaccination. Chickens were fed with YP during the experiments and orally immunized with live Newcastle disease virus (NDV) vaccine at 2 wk of age. Then, the animals were sacrificed, and samples were collected to measure the indicators of hemagglutination inhibition (HI), IgA response, IgA + cells, and cecum microbiome populations. The results showed that supplement of YP significantly enhanced serum NDV HI titer, intestinal NDV-specific secretory IgA, and intestinal IgA + cells. The sequencing results revealed that obviously increased relative abundance of Ruminococcaceae and decreased population of Bacteroidaceae in cecum were found in YP group. In summary, YP supplementation in diet enhanced intestinal IgA response to NDV vaccination by oral route and modulated the cecum microbiota to the advantage of the host in chickens.

Comammox Nitrospira within the Yangtze River continuum: community, biogeography, and ecological drivers

The recent discovery of comammox Nitrospira as complete nitrifiers has fundamentally renewed perceptions of nitrogen cycling in natural and engineered systems, yet little is known about the environmental controls on these newly recognized bacteria. Based on improved phylogenetic resolution through successful assembly of ten novel genomes (71-96% completeness), we provided the first biogeographic patterns for planktonic and benthic comammox Nitrospira in the Yangtze River over a 6030 km continuum. Our study revealed the widespread distributions and relative abundance of comammox Nitrospira in this large freshwater system, constituting 30 and 46% of ammonia-oxidizing prokaryotes (AOPs) and displaying 30.4- and 17.9-fold greater abundances than canonical Nitrospira representatives in water and sediments, respectively. Comammox Nitrospira contributed more to nitrifier abundances (34-87% of AOPs) in typical oligotrophic environments with a higher pH and lower temperature, particularly in the plateau (clade B), mountain and foothill (clade A) areas of the upper reach. The dominant position of planktonic comammox Nitrospira was replaced by canonical Nitrospira sublineages I/II and ammonia-oxidizing bacteria from the plateau to downstream plain due to environmental selection, while the dissimilarity of benthic comammox Nitrospira was moderately associated with geographic distance. A substantial decrease (83%) in benthic comammox Nitrospira abundance occurred immediately downstream of the Three Gorges Dam, consistent with a similarly considerable decrease in overall sediment bacterial taxa. Together, this study highlights the previously unrecognized dominance of comammox Nitrospira in major river systems and underlines the importance of revisiting the distributions of and controls on nitrification processes within global freshwater environments.

Perfluoroalkyl substances in the Yangtze River: Changing exposure and its implications after operation of the Three Gorges Dam

Potential ecological risk from perfluoroalkyl substances (PFASs) under changing exposure in large river systems has become a new challenge recently. Based on systematic monitoring of PFASs at 43 hydrologic stations along a 4300 km continuum of the Yangtze River, we investigated the ecological risk of PFASs under changing exposure resulting from operation of the Three Gorges Dam (TGD). Importantly, perfluorooctanoic acid (PFOA) was found extensively exposed in most mainstream water samples, accounting for about 90% of the total content of PFASs in both spring and autumn, while short-chain PFASs contributed more than PFOA in sediment. The significant inversion of long-chain PFASs occurrence from sediment to water reflected a profound change in exposure due to loss of finer sediments resulting from long-distance and long-term scour of the riverbed downstream of the TGD. The coarsening of bed materials would weaken sorption of long-chain PFASs in sediments and enhance their exposure in water, resulting in substantial increase of ecological risk to representative aquatic organisms. In the long term, particular attention should be paid to reduction of PFOA discharge to downstream of the TGD from typical industries. This also highlights the significance of huge dams to alternative exposures of persistent organic pollutants and the necessity of new strategy for ecological risk management of large river systems.

Cerebral Microbleeds Are Associated with Loss of White Matter Integrity

BACKGROUND AND PURPOSE

Previous studies have shown that diffusion tensor imaging suggests a diffuse loss of white matter integrity in people with white matter hyperintensities or lacunes. The purpose of this study was to investigate whether the presence of cerebral microbleeds and their distribution are related to the integrity of white matter microstructures.

MATERIALS AND METHODS

The study comprised 982 participants who underwent brain MR imaging to determine microbleed status. The cross-sectional relation between microbleeds and the microstructural integrity of the white matter was assessed by 2 statistical methods: a multilinear regression model based on the average DTI parameters of normal-appearing white matter and Tract-Based Spatial Statistics analysis, a tract-based voxelwise analysis. Fiber tractography was used to spatially describe the microstructural abnormalities along WM tracts containing a cerebral microbleed.

RESULTS

The presence of cerebral microbleeds was associated with lower mean fractional anisotropy and higher mean diffusivity, axial diffusivity, and radial diffusivity, and the association remained when cardiovascular risk factors and cerebral small-vessel disease markers were further adjusted. Tract-Based Spatial Statistics analysis indicated strictly lobar cerebral microbleeds associated with lower fractional anisotropy, higher mean diffusivity, and higher radial diffusivity in the internal capsule and corpus callosum after adjusting other cerebral small-vessel disease markers, while only a few voxels remained associated with deep cerebral microbleeds. Diffusion abnormalities gradients along WM tracts containing a cerebral microbleed were not found in fiber tractography analysis.

CONCLUSIONS

Cerebral microbleeds are associated with widely distributed changes in white matter, despite their focal appearance on SWI.

Polyfluoroalkyl substances in Danjiangkou Reservoir, China: Occurrence, composition, and source appointment

Legacy polyfluoroalkyl substances (PFASs) have been widely detected in various environmental matrices, which has caused great public concern. This study investigated the concentration, composition, partitioning, source apportionment, estimated daily intake (EDI), and ecological risks of 18 PFASs in water and sediments from Danjiangkou Reservoir. The total PFASs concentrations were 0.46-97.94 ng/L in water and 0.07-1.62 μg/kg in sediments. The total PFASs concentrations in water followed the order of spring > summer > winter > autumn (p < 0.05), and the PFAS compositions in water also varied among four seasons. However, no seasonal differences in the concentrations and compositions of PFASs were observed in sediments. The calculated logK_oc values of perfluoroalkyl carboxylic acids (PFCAs) were dependent on carbon chain length, decreasing first from C6 to C8 and then increasing from C8 to C13 due to the combined effects of steric hindrance and hydrophobic interaction, while the logK_oc values of C14 and C16 PFCAs were the lowest because of their very limited use. Principal component analysis-multiple linear regression analysis (PCA-MLRA) showed that food packaging/metal plating were the main sources of PFASs in spring, autumn, and winter, accounting for 64.8-81.9% and 50.5-76.9% of the total PFASs in water and sediments, respectively. However, in summer, 68.6% of total PFASs in water originated from leather/fabrics/textiles, and 70.0% of total PFASs in sediments were derived from textile treatment agents. The total EDI values through drinking water and dermal contact were 0.85, 0.69, 0.51, and 0.47 ng/kg bw/day for children (2-6, 7-12, and 13-17 years old) and adults, respectively, which were lower than the European Food Safety Authority's tolerable daily intake. However, the detected PFASs could pose low to medium ecological risks to daphnids and fish in spring. The study was significant for the development of effective strategies for controlling PFASs pollution in the Danjiangkou Reservoir.

Vertical distribution of microbial communities and their response to metal(loid)s along the vadose zone-aquifer sediments

AIMS

This study attempted to demonstrate the vertical shift in bacterial, archaeal and fungal communities along the vadose zone-aquifer sediments and their respective responses to environmental factors.

METHODS AND RESULTS

We collected samples from the vadose zone and three aquifer sediments along a 42·5 m bore of a typical agricultural land. The results showed that the bacterial community shifted greatly with depth. The classes of Actinobacteria (19·5%) and NC10 (11·0%) were abundant in the vadose zone while Alphaproteobacteria (22·3%) and Gammaproteobacteria (20·1%) were enriched in the aquifer. Archaeal and fungal communities were relatively more homogeneous with no significant trend as a function of depth. Process analyses further indicated that selection dominated in the bacterial community, whereas stochastic processes governed archaeal and fungal communities. Moreover environment-bacteria interaction analysis showed that metal(loid)s, especially alkali metal, had a closer correlation with the bacterial community than physicochemical variables.

CONCLUSIONS

Depth strongly affected bacterial rather than archaeal and fungal communities. Metal(loid)s prevailed over physicochemical variables in shaping the bacterial community in the vadose zone-aquifer continuum.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our study provides a new perspective on the structure of microbial communities from the vadose zone to the deep aquifers.