Search

In the Three Gorges reservoir region, central China, seismic activity increased substantially after the reservoir impoundment in 2003 which continues till date. Previous studies show that these are reservoir-triggered earthquakes and various factors are responsible for the increase in seismic activity after the reservoir impoundment. However, these studies do not provide a comprehensive assessment of influence of reservoir water level variations on spatiotemporal distribution of earthquakes. In this study, we statistically analyze the influence of the water level variations on the increased seismic activity in the reservoir region for the period from May 2003 to April 2020, using the power spectrum and singular spectrum techniques. Our statistical analyses confirm the influence of long-term variations in the water level time series on the occurrence of earthquakes after the reservoir impoundment. The analysis also indicates a positive role of annual reservoir water level fluctuations in the total seismicity of the region. Depending on the cluster patterns and relationship with faults, the earthquakes of the Three Gorges reservoir region are divided into three seismic zones (A, B, and C). For zone C, both the power spectrum and singular spectrum analyses confirm the strong periodic influence of reservoir water level variations on the earthquakes. Increase in seismicity of zone B is only in the initial period but not in the later stages of water impoundment and our statistical analyses indicate that the seismicity of this zone is not directly related to the annual reservoir water level variations. This confirms the conjecture in the earlier studies that the seismicity of this zone is related to the collapse of coal mines present in the area in the initial stages of reservoir impoundment. For zone A, our statistical analyses do not show strong influence of the annual reservoir water level variations on the occurrence of earthquakes. We suggest that this is due to the contribution of various other factors along with reservoir impoundment in the occurrence of earthquakes in this zone, as also opined in some earlier studies. [ABSTRACT FROM AUTHOR]

As the largest water conservancy and hydropower project in China, the Three Gorges Reservoir is a weak seismic activity area before impoundment, but the frequency of earthquakes increases significantly after impoundment. The spatial density scanning method was used to obtain the characteristics of spatio-temporal earthquake distribution in the reservoir area during loading and unloading processes. The results show that the frequencies of earthquakes during the loading and unloading processes were higher than that during the low-water-level operation period, which is well explained by the acoustic emission test results. The seismic b-value, fractal dimension D, and spatial correlation length SCL can be used together to indicate stress criticality. To analyze the impacts of reservoir water loading and unloading on seismicity in the reservoir area, time-scan analyses were performed on the b-value, D-value, and SCL of earthquakes near the Zigui segment and the Badong segment. Previous studies argued that the time-varying characteristics of b-values do not hold predictive significance for earthquakes in the M4.0–6.2 range. However, our study found that the time-varying characteristics of b-values are of predictive significance for earthquakes around M4.0. These seismic parameters decrease significantly before moderate earthquakes but at different rates in different regions. [ABSTRACT FROM AUTHOR]

Using the test–retest data of the relative gravity field and earthquake monitoring catalog of the Three Gorges Reservoir (TGR) from October 2001 to October 2009, this paper systematically analyzes the changes in the gravity field in the head area of the reservoir and the temporal and spatial distribution characteristics of seismic activity during the impoundment process. It also employs the surrogate reshuffling tests to calculate the cross-correlation between the reservoir water level and the seismic activity sequence and discusses the influence of the rising reservoir water level on the gravity field and seismic activity in the reservoir region. Then, by constructing a three-dimensional finite-difference model based on the theory of fluid–solid coupling, the mechanism of reservoir-induced earthquakes is discussed from the aspects of direct reservoir water load and reservoir water infiltration. The results show that: (1) The rising reservoir water level has had a critical impact on the gravity field and seismic activity in the reservoir's head area. The cumulative changes in the gravity field from October 2001 to November 2008 show that water impounding has led to a huge banded positive anomaly of gravity along the river near Xiangxi, which reached 450 × 10−8 ms−2. The seismicity activity dominated by micro-earthquakes after a 135 m water level rose rapidly, and the monthly average earthquake frequency increased from 2.00 before the impoundment to 92.60 after the 175 m stage. (2) From the beginning of the impoundment to the experimental impoundment stage of 175 m, the time series correlation test result between the monthly frequency of earthquakes and the water level of the reservoir also changed from uncorrelated before the water storage to correlated when the time lag was 0 months at a 95% confidence threshold. This indicates that the seismic activity obviously has a direct relationship with the load pressure produced by the rapid rise of the reservoir water level, which causes the instability of the mines, karst caves, shallow rock strata, and faults within 10 km along the river and near the reservoir bank, and consequently induces earthquakes. (3) As the TGR enters the 175 m high-level operation stage, the cross-correlation test confirmed that the seismic activity and the reservoir water level show negative correlation characteristics under the time lag of 4 to 5 months, indicating that the seismic activity has a lagging response to the reservoir water level change. The continued infiltration of the reservoir water, followed by the softening of the faults and other actions, triggered the Xiangxi M4.1 earthquake at the center of the four quadrants of gravity anomalies near Xiangxi on 22 November 2008. The Xiangxi segment of the reservoir and its periphery, a triangular geological region where the Xiannvshan faults, the Jiuwanxi fault, and the Yangtze River meet, might be at risk of having reservoir-induced tectonic earthquakes. [ABSTRACT FROM AUTHOR]

Abstract Polycyclic aromatic hydrocarbons (PAHs) are a kind of persistent toxic substances, which have been frequently detected in environmental media. However, studies on their occurrences and distributions in drinking water are insufficient and their composition profiles in drinking water are still not clear. In this study, we investigated 16 priority polycyclic aromatic hydrocarbons (PAHs) in drinking water from different administrative level cities throughout mainland China, analyzed the influences of anthropogenic activities on PAHs, and assessed the health risk of the PAHs in drinking water. On the national scale, the sum concentration of the 16 priority-controlled PAHs (∑ 16 PAHs) designated by the U.S. Environmental Protection Agency (USEPA) was in a range of 3.89–231.39 (mean 56.25) ng L−1. With the decline of ∑ 16 PAHs, the concentration of 3-ring PAHs decreased, while its proportion increased, indicating 3-ring PAHs might be more difficult to remove than other PAHs in drinking water. The geographical distribution of PAHs in drinking water of China was in a descending order of West (69.81 ng L−1) > South (61.95 ng L−1) > North (58.63 ng L−1) > East (39.21 ng L−1) > Northeast China (37.93 ng L−1). ∑ 16 PAHs in drinking water of Prefecture-level City was the greatest (71.49 ng L−1) followed by Provincial Capital (52.12 ng L−1), County-level City (50.98 ng L−1) and Municipality (33.92 ng L−1). ∑ 16 PAHs was significantly negatively correlated with the per capita GDP of sampling city (P < 0.01 , n = 78), implying that waterworks is an effective way to control and reduce PAH pollution in drinking water. The carcinogenic risk of the 16 PAHs in drinking water of China was much greater than the non-carcinogenic risk. Graphical abstract Image 1 Highlights • Nationwide occurrence of PAHs in drinking water was investigated. • 3-ring PAHs were the dominated components in drinking water. • PAHs in drinking water varied among different cities of China. • ∑ 16 PAH were significantly negatively correlated with the per capita GDP. [ABSTRACT FROM AUTHOR]

Glyphosate-tolerant genetically modified (GM) soybeans (Glycine max (L.) Merr.), known commercially as Roundup Ready soybeans, dominate oil consumption and are partly used for protein intake in China. Chemical composition of soybean seed determines its nutritional value, its processing suitability for various protein products, and market decisions. We conducted a compositional comparison of eight GM and 16 conventional Chinese representative soybean varieties. Crude protein, crude fat, moisture, ash, carbohydrate, crude fibre, amino acid and fatty acid contents of the different soybean genotypes were compared and analysed. The GM soybeans had the highest oil concentration but poorer quality, whereas conventional soybeans from the Huanghuaihai region of China showed significantly higher protein, total amino acid, essential amino acid and oleic acid contents, and lower n-6 : n-3 ratio and carbohydrate content, which suggested superior nutritional value. Principal component analysis indicated that protein, carbohydrates and amino acids (except tryptophan, methionine, tyrosine, histidine and proline) contributed most to distinguishing GM soybeans from conventional Chinese soybeans. Differences among the GM and conventional soybeans collected from two major producing regions in China can help to guide manufacturing processes and market decisions with respect to soybeans. High protein and amino acid content in conventional Chinese soybeans mean the potential to expand and improve the International Life Sciences Institute Crop Composition Database used for safety assessment of GM soybean. Are there any differences in nutrient composition between the crucial global transgenic, glyphosate-resistant soybeans and conventional Chinese soybeans? Our results indicated that transgenic soybeans had the highest oil concentration but poorer quality, whereas soybeans from the Huanghuaihai region of China had superior nutritional value in terms of protein, oil, amino acid and fatty acid composition. The results of this study can help to guide soybean processing and promote safety assessment of transgenic soybeans. [ABSTRACT FROM AUTHOR]

Abstract Perfluoroalkyl acids (PFAAs) are a group of emerging persistent organic pollutants (POPs), which have been ubiquitously detected in the environmental media. However, national scale investigations on their occurrence and distribution in drinking water are still insufficient. In this study, we detected the 17 priority PFAAs in drinking water from 79 cities of 31 provincial-level administrative regions throughout China, and investigated their occurrence and distribution. Additionally, we also analyzed the influencing factors on their profiles, such as the existence of industrial sources, socioeconomic factors (population density and GDP), and assessed levels of risk associated with contaminated drinking water. On the national scale, the sum concentrations of the 17 PFAAs (∑ 17 PFAAs) in drinking water was in a range of 4.49–174.93 ng/L with a mean value of 35.13 ng/L. Among the 17 individual PFAAs, perfluorobutanoic acids (PFBA) was the most abundant individual PFAAs with the median concentration of 17.87 ng/L, followed by perfluorooctanoic acid (PFOA, 0.74 ng/L), perfluorononanoic acid (PFNA, 0.40 ng/L) and perfluorooctane sulfonic acid (PFOS, 0.25 ng/L). The geographic distribution characteristic of ∑ 17 PFAAs in drinking water was in a descending order of Southwestern China (57.67 ng/L) > Eastern coastal China (32.85 ng/L) > Middle China (29.89 ng/L) > Northwestern China (28.49 ng/L) > Northeastern China (22.03 ng/L), and in general, the existence of the industrial sources could positively affect the contamination levels of PFAAs in drinking water. The pollution level of PFAAs in drinking water also varied among the three different city levels (medium-sized city > big city > town). In towns, the positive correlations were observed between the population density and the ∑ 17 PFAAs (R 2 = 0.45, p < 0.01), and the individual concentration of PFHxA, PFBS, and PFOA (p < 0.01). Moreover, besides PFAAs in Yunnan, Jiangsu, and Jiangxi, concentrations of related PFAAs in drinking water from 28 provinces were less than the suggested drinking water advisories. The relatively higher concentrations of PFAAs in Yunnan, Jiangsu, and Jiangxi suggest that further studies focusing on their sources and potential health risk to humans are needed. Graphical abstract Unlabelled Image Highlights • The nationwide occurrence of PFAAs in drinking water of China was investigated. • PFBA, PFOA, and PFHxS were dominated components in drinking water. • PFAAs concentration in drinking water varied among different regions and city levels of China. • PFAAs in drinking water might not pose a serious risk in most sample sites. [ABSTRACT FROM AUTHOR]

As one group of emerging pollutants, the threat of organophosphate esters (flame retardants and plasticizers, OPEs) to drinking water safety is not well recognized. Now, the oral reference dose (RfD) and oral cancer slope factor (SFO) of OPEs have been updated by USPEA, therefore the threat of OPEs to drinking water safety could be assessed. In this study, occurrence, health risk and key impact factor of OPEs in drinking water of China were analyzed covering 79 cities, whose population and gross domestic product (GDP) accounted for 28.8% and 44.1% of them in China, respectively. Total concentration of 14 common OPEs in drinking water was 13.42–265.48 ng/L. The exposure level of OPEs via ingestion of drinking water was much lower than that of food ingestion but was comparable with dust ingestion, inhalation and dermal absorption. A health assessment for OPEs via ingestion of drinking water suggested that the potential cancer risk occurred (>1.00E-6) but no obvious non-carcinogenic effects occurred (<1). Tris-(2,3-dibromopropyl) phosphate (TDBPP) contributed to about 72.4% of carcinogenic risk, which should be treated as "prior monitoring OPEs" in further studies. The occurrence and distribution of OPEs in drinking water of China have a good corresponding relationship with the Aihui-Tengchong Line, and drinking water treatment technology (DWTT) was found to be a key factor. Total OPEs, halogeno-OPEs and alkyl-OPEs in drinking water from advanced DWTT cities were much lower than those of conventional DWTT cities. Compared with conventional DWTT, advanced DWTT could reduce about 65.6% and 36.5% of carcinogenic risk and non-carcinogenic risk of OPEs, respectively. Considering the annual growth of OPEs consumption in China and world, further studies regarding the environmental threat of OPEs are required. Image 1 • Comprehensive information about OPEs in drinking water was provided. • Exposure and health risk of OPEs via drink water were assessed. • OPEs in drinking water have potential cancer risk for consumer. • TDBPP should be treated as prior monitoring OPEs. • DWTT is a key factor on OPEs in drinking water of China. [ABSTRACT FROM AUTHOR]

The North China Craton is a natural laboratory for studying thinning, transformation, and replacement of ancient lithospheres. Its density structure and isostatic state of the crust provide key information for a better understanding of the deep tectonic characteristics and dynamic mechanism. In this study, we analyze observed seismic and gravity/GNSS co-located data, and explore the tectonic characteristics and dynamic significance in the southeastern margin of the North China Craton, using isostatic gravity analysis based on Airy theory and crustal density structure inversions. The results indicate that depth of the Moho interface in the research area ranges between 32 km and 41 km. The crust gradually thins from west to east, and the changing trend of the upper, middle, and lower crust is similar to the Moho interface. There has been significant replacement of the deep mantle and lower crust in the research area, especially where fault zones are located. In addition, the overall area is in a positive isostatic state, indicating that the crust is on an upward trend. The lithosphere on the east side is basically in the state of isostasy, but with a slight tendency for Moho subsidence, indicating a potential thickening of the lithosphere in this region. • The seismic and gravity/GNSS co-site observation data of the southeast margin of the North China Craton are analyzed. • The S-wave velocity structure below the station is obtained by fitting the HVSR curve based on Monte Carlo inversion method. • The 3D gravity inversion method constrained by Lagrange multiplier method is used to invert the crustal density structure. • The study area has undergone significant material replacement, the lithosphere on the east side showed a trend of thickening. [ABSTRACT FROM AUTHOR]

Halobenzoquinones (HBQs) are an emerging class of drinking water disinfection byproducts (DBPs) that have been frequently detected in drinking water and are highly relevant to bladder cancer. Among the studied HBQs, 2,6-dichloro-1,4-benzoquinone (DCBQ) had the highest detection frequency and concentrations in drinking water. However, compared to other countries, the studies on HBQs that are being conducted in China, especially those on HBQs in drinking water, are not sufficient. Therefore, the concentrations of DCBQ in the Tianjin drinking water supply system were investigated in two seasons (winter and summer), and the risk that is posed by DCBQ in drinking water was evaluated for the first time. In addition, since HBQs are prone to hydrolysis in neutral and alkaline environments, identification of the hydrolytic characteristics of DCBQ at various pH values and in the real water environment is essential for better describing the environmental behavior of DCBQ; hence, the hydrolysis characteristics of DCBQ in phosphate buffers with various pH values and in four water samples were also examined in our study. The results demonstrated that DCBQ was widely detected in the drinking water treatment process and distribution systems, and the average concentration in our study (12.0 ng/L) was at a moderately high level compared with the reported concentration of DCBQ in the drinking water distribution networks. The risk quotient (RQ) of DCBQ is equivalent to that of trihalomethanes (THMs); thus, the relatively low concentrations of DCBQ should also be considered. Furthermore, the results demonstrated that the hydrolysis of DCBQ follows first-order reaction kinetics, the reaction rate accelerates as the pH of the phosphate buffer system increases, and the rate of hydrolysis of DCBQ in drinking water is affected not only by the pH but also by other environmental factors, such as the organic matter concentration. Therefore, further investigation is necessary to identify the main factor of DCBQ hydrolysis in real water environments., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: The role of partner types in modifying HIV seroconversion risk among men who have sex with men (MSM) is complex. We sought to understand the role of regular sexual partners and risky sexual behavior in contributing to incident HIV infection among MSM., Methods: From July 2011 to August 2017, we recruited HIV-negative men who reported having anal or oral homosexual encounters in the past 6 months and they were followed up every 3 months for 2 visits. We collected sociodemographic and behavioral characteristics by a self-administrated questionnaire. HIV status was confirmed by a sequential rapid test and confirmatory test. We used multivariable Cox regression to identify risk factors and interaction models to evaluate the relative excess risk between relevant variables., Results: Among 1218 participants, the HIV seroconversion rate was 3.66/100 person-years. HIV seroconversion was associated with lower educational attainment [adjusted hazards ratio (aHR)] = 1.73, 95% CI: 1.06 to 2.81), having had penetrative sex with male before age of 18 years (aHR = 2.44, 95% CI: 1.20 to 4.99), not using condoms in the last sexual encounter (aHR = 2.19, 95% CI: 1.29 to 3.71), and having regular but not committed partners (aHR = 3.33, 95% CI: 1.77 to 6.93). Among 890 (73%) of men reported having regular partners, HIV seroconversion was more frequent in men whose stable partners were not committed as boyfriends (aHR = 3.31, 95% CI: 1.73 to 6.36) and in men having unprotected anal sex (aHR = 2.61, 95% CI: 1.42 to 4.80). Interaction between these 2 factors was observed (relative excess risk of interaction = 4.53)., Conclusions: Incidence among MSM in China was high; unprotected sex with steady but not committed partners was associated with increased seroconversion risk. It is imperative to expand safer sex education and training for MSM to reduce unsafe sexual behaviors, including awareness that casual partners are not the only source of infection.

Human enterovirus B106 (EV-B106) is a recently identified member of enterovirus species B. In this study, we report the complete genomic characterization of an EV-B106 strain (148/YN/CHN/12) isolated from an acute flaccid paralysis patient in Yunnan Province, China. The new strain had 79.2-81.3% nucleotide and 89.1-94.8% amino acid similarity in the VP1 region with the other two EV-B106 strains from Bolivia and Pakistan. When compared with other EV serotypes, it had the highest (73.3%) VP1 nucleotide similarity with the EV-B77 prototype strain CF496-99. However, when aligned with all EV-B106 and EV-B77 sequences available from the GenBank database, two major frame shifts were observed in the VP1 coding region, which resulted in substantial (20.5%) VP1 amino acid divergence between the two serotypes. Phylogenetic analysis and similarity plot analysis revealed multiple recombination events in the genome of this strain. This is the first report of the complete genome of EV-B106.

Objective: We investigated the awareness and acceptability of pre-exposure prophylaxis (PrEP) among men who have sex with men (MSM) and potential predicting factors., Methods: This study was conducted among MSM in Beijing, China. Study participants, randomly selected from an MSM cohort, completed a structured questionnaire, and provided their blood samples to test for HIV infection and syphilis. Univariate logistic regression analyses were performed to evaluate the factors associated with willingness to accept (WTA) PrEP. Factors independently associated with willingness to accept were identified by entering variables into stepwise logistic regression analysis., Results: A total of 152 MSM completed the survey; 11.2% had ever heard of PrEP and 67.8% were willing to accept it. Univariate analysis showed that age, years of education, consistent condom use in the past 6 months, heterosexual behavior in the past 6 months, having ever heard of PrEP and the side effects of antiretroviral drugs, and worry about antiretroviral drugs cost were significantly associated with willingness to accept PrEP. In the multivariate logistic regression model, only consistent condom use in the past 6 months (odds ratio [OR]: 0.31; 95% confidence interval [CI]: 0.13-0.70) and having ever heard of the side effects of antiretroviral drugs (OR: 0.30; 95% CI: 0.14-0.67) were independently associated with willingness to accept PrEP., Conclusions: The awareness of PrEP in the MSM population was low. Sexual behavioral characteristics and knowledge about ART drugs may have effects on willingness to accept PrEP. Comprehensive prevention strategies should be recommended in the MSM community.