Continuous Flow-Double Purge and Trap Method for Preconcentrating Mercury in Large Volumes of Seawater for Stable Isotope Analysis.

Mercury (Hg) isotopes provide a useful tool to understand Hg sources and processes in the environment. The Hg isotopic composition of seawater remains poorly constrained due to the lack of an efficient method to process large volumes of low-Hg-concentration seawater samples. Here, we develop a continuous flow-double purge and trap device for the in situ preconcentration of Hg in seawater. This method yielded a good Hg recovery of 91.7 ± 3.3% (n = 4, 1SD) for spiked seawater samples and gave reasonably similar Hg isotope ratios of NIST 8610, indicating a limited matrix effect and limited Hg isotope fractionation during processing of seawater. NIST 8610 δ202Hg (-0.55 ± 0.09‰, n = 4, 1SD) and Δ199Hg (0.07 ± 0.02‰, n = 4, 1SD) were similar to previously published data. The method was successfully applied to seawater collected from the Xiamen Bay and the South China Sea. The seawater samples showed a Hg recovery of 91.6 ± 5.4% (n = 12, 1SD). Seawater Δ199Hg (-0.04 ± 0.05‰, n = 7, 1SD) in the Xiamen Bay was different from seawater Δ199Hg (0.05 ± 0.07‰, n = 5, 1SD) in the South China Sea, which implies distinct Hg sources to coastal and open ocean areas and highlights the robustness of our method in understanding the Hg isotopic composition of seawater.

Ignited competition: Impact of bioactive extracellular compounds on organelle functions and photosynthetic systems in harmful algal blooms.

Prevalent interactions among marine phytoplankton triggered by long-range climatic stressors are well-known environmental disturbers of community structure. Dynamic response of phytoplankton physiology is likely to come from interspecies interactions rather than direct climatic effect on single species. However, studies on enigmatic interactions among interspecies, which are induced by bioactive extracellular compounds (BECs), especially between related harmful algae sharing similar shellfish toxins, are scarce. Here, we investigated how BECs provoke the interactions between two notorious algae, Alexandrium minutum and Gymnodinium catenatum, which have similar paralytic shellfish toxin (PST) profiles. Using techniques including electron microscopy and transcriptome analysis, marked disruptions in G. catenatum intracellular microenvironment were observed under BECs pressure, encompassing thylakoid membrane deformations, pyrenoid matrix shrinkage and starch sheaths disappearance. In addition, the upregulation of gene clusters responsible for photosystem-I Lhca1/4 and Rubisco were determined, leading to weaken photon captures and CO2 assimilation. The redistribution of lipids and proteins occurred at the subcellular level based on in situ focal plane array FTIR imaging approved the damages. Our findings illuminated an intense but underestimated interspecies interaction triggered by BECs, which is responsible for dysregulating photosynthesis and organelle function in inferior algae and may potentially account for fitness alteration in phytoplankton community.

A Multi-Task Network Based on Dual-Neck Structure for Autonomous Driving Perception.

A vision-based autonomous driving perception system necessitates the accomplishment of a suite of tasks, including vehicle detection, drivable area segmentation, and lane line segmentation. In light of the limited computational resources available, multi-task learning has emerged as the preeminent methodology for crafting such systems. In this article, we introduce a highly efficient end-to-end multi-task learning model that showcases promising performance on all fronts. Our approach entails the development of a reliable feature extraction network by introducing a feature extraction module called C2SPD. Moreover, to account for the disparities among various tasks, we propose a dual-neck architecture. Finally, we present an optimized design for the decoders of each task. Our model evinces strong performance on the demanding BDD100K dataset, attaining remarkable accuracy (Acc) in vehicle detection and superior precision in drivable area segmentation (mIoU). In addition, this is the first work that can process these three visual perception tasks simultaneously in real time on an embedded device Atlas 200I A2 and maintain excellent accuracy.

Spectrophotometric determination of nitrate in small volume of seawater samples using a simple resorcinol method.

A simple resorcinol method to determine nitrate (NO3-) in seawater using a microplate reader with a 48-well plate was established. The method involved the nitration of resorcinol in sulfuric acid to form a pink product that was detected at 505 nm. Reagent concentrations were optimized, and the effect of salinity on NO3- determination was investigated. The detection limit of this method was 0.8 µM, while the upper limit of the linear range was 100 µM. The recoveries ranged from 91.5 to 109.7% for spiked seawater samples with different salinities. The proposed method was compared with two reference methods, and the results revealed a good correlation. Compared to conventional methods that require the preparation of reactants, the proposed method used aqueous solutions as reagents for the reaction, which was simpler and more convenient. Compared to the methods that used organic solvents for the direct determination of NO3-, the proposed method was suitable for estuarine and coastal water samples with large salinity variations. All results indicated that the proposed method can satisfy the requirements of laboratory analysis and demonstrate high application potential for use in field determination.

Indocyanine green real-time-guided laparoscopic duodenum-preserving pancreatic head resection.

Duodenum-preserving pancreatic head resection (DPPHR) is very complicated due to its difficulty to find the lower common bile duct (CBD), and to preserve the blood supply of the duodenum and CBD. Recently, indocyanine green (ICG) has been widely applied for navigation during biliary system and liver surgery. However, the application of ICG-guided laparoscopic DPPHR has not been established. Herein, we report an intraoperative angiography technique using ICG fluorescence imaging to visualise blood flow, tissue perfusion, CBD navigation and bile leakage assessment.

Application of an Isotope Binary Mixing Model for Determination of Precise Mercury Isotopic Composition in Samples with Low Mercury Concentration.

An isotope binary mixing model was applied for high precision measurement of mercury isotope ratios in samples with low mercury concentrations by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). Standard addition was used to evaluate the precision and accuracy of the isotope composition calculations resulting from the isotope binary mixing model. A high, steady 202Hg signal of approximately 2.13 V was achieved, with the mercury concentration reaching 3 ng/mL. The isotopic composition of three standards (NIST SRM 1646a; NIST SRM 1575a; BCR 482) and natural samples were precisely determined. The standards and natural samples were diluted to low mercury concentrations (low to 0.90 ng/mL) and mixed with standard solutions (NIST SRM 3133) with high mercury concentrations (50 ng/mL); the isotopic compositions of low mercury concentration samples were calculated using an isotope binary mixing model after the isotopic compositions of the mixing solutions were measured. The results showed that the uncertainty of the calculated mercury isotopic compositions was in an acceptable range and the calculation isotope data were in good agreement with direct measurements. Our method allows the precise determination of mercury isotope composition in mercury solutions of concentrations (0.90 ng/mL) below the detection limit of the current system (3.00 ng/mL).

Binding pancreaticogastrostomy in laparoscopic central pancreatectomy: a novel technique in laparoscopic pancreatic surgery.

BACKGROUND: Even though more and more cases of laparoscopic central pancreatectomy (LCP) are reported (Machado et al. in Surg Laparosc Endosc Percutan Tech 23(6):486-490, 2013; Hong et al. in World J Surg Oncol 10:223, 2012; Gonzalez et al. in JOP 14(3):273-276, 2013, Zhang et al. in J Laparoendosc Adv Surg Tech A 23(11):912-918, 2013; Sucandy et al. in N Am J Med Sci 2(9):438-441, 2010; Sa Cunha et al. in Surgery 142(3):405-409, 2007), the management for pancreatic stumps remains the most technically challenging part which is the same as in pancreatoduodenectomy (PD), making it the bottleneck for laparoscopic pancreatic surgery. In open surgery, various pancreatic reconstruction techniques designed for either pancreaticojejunostomy (PJ) or pancreaticogastrostomy (PG) have been attempted to reduce the postoperative pancreatic fistula (POPF), including the binding anastomosis, invented by our team, i.e., binding PG (BPG) and binding PJ, which have been proved to be effective to reduce the POPF (Hong et al. 2012; Peng et al. in Ann Surg 245(5):692-698, 2007; Peng et al. in Updates Surg 63(2):69-74, 2011). However, despite of this, few reports are seen addressing such technique for laparoscopic surgery even though laparoscopic pancreatic surgery is more performed. After a previous successful laparoscopic BPG in a case of laparoscopic CP (LCP; Hong et al. 2012) and more than 50 cases of open PD and CP (Peng et al. 2011), we further performed laparoscopic BPG in 10 consecutive cases of LCP with satisfactory outcomes. OBJECTIVE: To explore the feasibility and efficacy of LCP with BPG. METHODS: Between October 2011 and July 2014, LCP with laparoscopic BPG was performed in ten consecutive patients with lesions of benign or low malignancy at the pancreatic neck. Operative and pathological data, complications, hospital stay and details on the surgical techniques were introduced. RESULTS: The operations were successfully performed in all the ten cases, with no conversions. The tumor size ranged from 2.0-3.0 to 2.5-3.0 cm, average (2.50 ± 0.35) to (2.66 ± 0.35) cm, and the diameter of pancreatic duct was (1.6-2.1) mm, average (1.71 ± 0.17) mm. Operation time was 170-250 (198.50 ± 25.82) min, and blood loss was 20-300 (125 ± 107.31) mL. Three cases had grade A pancreatic fistula (PF), and one case had delayed gastric emptying, which were all managed with conservative treatment. Upper GI bleeding occurred in one case which was cured with second operation, time for the recovery of bowl movement was 3-5 (4.2 ± 0.8) days, the time for semifluid dieting was 6-10 (8.2 ± 1.5) days, and the hospital stay was 8-20 (12.8 ± 4.63) days. The postoperative fast blood sugar was (6.3 ± 1.6) mmol/L with the normal diet, which was not significantly different from the preoperative data (5.3 ± 0.5) mmol/L (P > 0.05). The postoperative pathology was as follows: five cases of cystic serous adenoma, one case of intraductal papillary mucinous neoplasm, two cases of neuroendocrine tumor, and two cases of solid pseudopapillary tumor of pancreas. All the patients were followed up for 7-40 months, no recurrence happened, and no new incidence of diabetes or insufficiency of pancreatic exocrine function occurred. CONCLUSIONS: LCP with BPG is feasible and safe; the advantages lie in its minimal invasiveness, the efficacy for avoiding PF, and the preservation of the pancreatic endocrine and exocrine function insufficiency, making it an ideal procedure for the benign or low-malignant lesions at the pancreatic neck.

Indocyanine green retention is a potential prognostic indicator after splenectomy and pericardial devascularization for cirrhotic patients.

BACKGROUND: Splenectomy and pericardial devascularization (SPD) is an effective treatment of upper gastrointestinal bleeding and hypersplenism in cirrhotic patients with portal hypertension. Indocyanine green retention at 15 minutes (ICGR15) was reported to offer better sensitivity and specificity than the Child-Pugh classification in hepatectomy, but few reports describe ICGR15 in SPD. The present study was to evaluate the prognostic value of ICGR15 for cirrhotic patients with portal hypertension who underwent SPD. METHODS: From January 2012 to January 2015, 43 patients with portal hypertension and hypersplenism caused by liver cirrhosis were admitted in our center and received SPD. The ICGR15, Child-Pugh classification, model for end-stage liver disease (MELD) score, and perioperative characteristics were analyzed retrospectively. RESULTS: Preoperative liver function assessment revealed that 34 patients were Child-Pugh class A with ICGR15 of 13.6%-43.0% and MELD score of 7-20; 8 patients were class B with ICGR15 of 22.8%-40.7% and MELD score of 7-17; 1 patient was class C with ICGR15 of 39.7% and MELD score of 22. The optimal ICGR15 threshold for liver function compensation was 31.2%, which offered a sensitivity of 68.4% and a specificity of 70.8%. Univariate analysis showed preoperative ICGR15, MELD score, surgical procedure, intraoperative blood loss, and autologous blood transfusion were significantly different between postoperative liver function compensated and decompensated groups. Multivariate regression analysis revealed that ICGR15 was an independent risk factor of postoperative liver function recovery (P=0.020). CONCLUSIONS: ICGR15 has outperformed the Child-Pugh classification for assessing liver function in cirrhotic patients with portal hypertension. ICGR15 may be a suitable prognostic indicator for cirrhotic patients after SPD.

Comparison of two laparoscopic splenectomy plus pericardial devascularization techniques for management of portal hypertension and hypersplenism.

OBJECTIVE: Our research was conducted to analyze the outcomes of two laparoscopic splenectomy plus pericardial devascularization (LSPD) techniques in the management of portal hypertension (PTH) and hypersplenism. METHODS: Between May 2012 and May 2013, 41 patients with PTH and hypersplenism undergoing LSPD were retrospectively analyzed. Of them, 29 patients received LSPD by LigaSure Vessel Sealing System (LVSS) and Endo-GIA universal endoscopic vascular linear staplers (Endo-GIA) (EG Group) and 12 patients received LSPD by LVSS and Hem-o-Lock (HL Group). Operating time, intraoperative blood loss, postoperative course, and hospitalization costs were compared between the two LSPD combination techniques. RESULTS: There were no significant differences in preoperative patient characteristics of the two groups. Significantly less operating time, intraoperative blood loss, and postoperative complications were observed in EG Group. The incidence of portal vein thrombosis was lower in the EG Group (3.4 vs. 8.3%), as well as the incidence of pancreatic fistula (0 vs. 8.3%). Upper gastrointestinal hemorrhage was not observed in either group. Uncontrolled bleeding warranted conversion to open surgery in one case in EG Group (conversion rate 3.4%) and in two cases in HL Group (conversion rate 16.7%). Two patients (16.7%) in HL Group underwent successful emergency exploratory laparotomy due to uncontrolled intraabdominal bleeding postoperatively. No re-operation was needed in EG Group. Two patients experienced liver failure after surgery in each group. Of those, three patients were managed successfully and one patient refused further therapy. While the overall complication rate was significantly lower in EG Group (17.2 vs. 58.3%, P < 0.05), overall hospitalization costs remained significantly higher for EG Group. CONCLUSION: The results suggest that the modified Endo-GIA and LVSS technique is a safe and effective combination approach to LSPD with shorter operative time, less intraoperative blood loss, lower conversion rate to laparotomy, shorter hospital stay, better recovery, and lower postoperative complication rate compared with the Hem-o-Lock and LVSS approach. Higher hospitalization expenses associated with the Endo-GIA and LVSS approach.

Sirtuin 1 facilitates chemoresistance of pancreatic cancer cells by regulating adaptive response to chemotherapy-induced stress.

Chemotherapy drugs themselves may act as stressors to induce adaptive responses to promote the chemoresistance of cancer cells. Our previous research showed that sirtuin 1 (SIRT1) was overexpressed in pancreatic cancer patients and deregulation of SIRT1 with RNAi could enhance chemosensitivity. Thus, we hypothesized that SIRT1 might facilitate chemoresistance in pancreatic cancer cells through regulating the adaptive response to chemotherapy-induced stress. In the present study, SIRT1 in PANC-1, BXPC-3, and ASPC-1 cells was upregulated after treatment with gemcitabine. Moreover, the decrease in SIRT1 activity with special inhibitor EX527 had a synergic effect on chemotherapy with gemcitabine in PANC-1 and ASPC-1 cell lines, which significantly promoted apoptosis, senescence, and G0 /G1 cycle arrest. Western blot results also showed that SIRT1, acetylated-p53, FOXO3a, and p21 were upregulated after combined treatment, whereas no obvious change was evident in total p53 protein. To further confirm the role of SIRT1 in clinical chemotherapy, SIRT1 was detected in eight pancreatic cancer tissues acquired by endoscopy ultrasonography guided fine needle aspiration biopsy before and after chemotherapy. Compared to before chemotherapy, SIRT1 was significantly increased after treatment with gemcitabine in six cases. Thus, our results indicated a special role for SIRT1 in the regulation of adaptive response to chemotherapy-induced stress, which is involved in chemoresistance. Moreover, it indicates that blocking SIRT1 activity with targeting drugs might be a novel strategy to reverse the chemoresistance of pancreatic cancer.

High-sensitive determination of tetracycline antibiotics adsorbed on microplastics in mariculture water using pre-COF/monolith composite-based in-tube solid phase microextraction on-line coupled to HPLC-MS/MS.

Microplastics (MPs) act as carriers for organic pollutants (e.g. antibiotics) and microorganisms (e.g. bacteria) in waters, leading to the proliferation of antibiotic resistance genes. Moreover, the antibiotics adsorbed on MPs may exacerbate this process. For further research, it is necessary to understand the types and amounts of antibiotics adsorbed on MPs. However, due to the heavy work of MPs collection and sample pretreatment, there is a lack of analytical methods and relevant data. In this study, an in-tube solid phase microextraction (IT-SPME) on-line coupled to HPLC-MS/MS method based on amorphous precursor polymer of three-dimensional covalent organic frameworks/monolith-based composite adsorbent was developed, which could efficiently capture, enrich and analyze tetracycline (TCs) antibiotics. Under the optimal extraction parameters, the developed method was capable of detecting TCs at levels as low as 0.48-1.76 pg. This method was applied to analyze the TCs adsorbed on MPs of different particle sizes in mariculture water for the first time, requiring a minimum amount of MPs of only 1 mg. Furthermore, it was observed that there could be an antagonistic relationship between algal biofilm and TCs loaded on MPs. This approach could open up new possibilities for analyzing pollutants on MPs and support deeper research on MPs.

Deep-sea microplastics aging and migration exerted by seamount topography and biotopes in the subtropic Northwest Pacific Ocean.

Microplastics (MPs) have drawn exponential attention as anthropogenic pollutants, which have invaded every corner of planet. Seamounts are prominent features of the deep-sea topography, acting as breeding ground for marine animal calves and hotspots of pelagic biodiversity, yet MPs pollution in seamounts is scarcely studied. We investigated the MPs load in the whole vertical profile of seamount ambient water in the Subtropical Northwest Pacific Ocean. Based on focal plane array Fourier Transform Infrared spectrometry, MPs were detected in all layers, and varied from 0.9 to 3.8 items L-1, PP and PE were dominant, PA and PET tended to gather at the seamount summit. With depth increasing, small MPs (20-50 µm) were dominant, and MPs surface roughness including crack, hole, and biofouling showed an increase. Three plastic-degrading bacteria were noted in the layers around the seamount, indicating that the seamount community may accelerate MPs aging and further migration. Our work first unveiled the MPs occurrence in the whole vertical profile of the seamount. It reveals that ocean MPs migration and degradation are significantly affected by the unique topography and biotopes of the seamount.

Study of ultrasound-guided percutaneous microwave ablation combined with portal vein embolization for rapid future liver remnant increase of planned hepatectomy.

Purpose: To evaluate the efficacy of ultrasound-guided percutaneous microwave ablation (PMA) combined with portal vein embolization (PVE) for planned hepatectomy. Methods: We retrospectively reviewed data of 18 patients with multiple right liver tumors or hilar tumor of liver invades the surrounding tissue and insufficient future liver remnant (FLR) for hepatectomy from July 2015 to March 2017. Ultrasound-guided PMA was performed by using PMCT cold circulation microwave treatment apparatus. PVE was performed after PMA. The increase of FLR was evaluated by computed tomography (CT) 6-22 days after PVE. The proportion of FLR, increase in the amplitude of FLR, procedure-related complications, perioperative morbidity and mortality, and overall survival (OS) rates, the median survival time were analyzed. Results: The median volume of FLR before PMA and PVE was 369.7 ml (range: 239.4-493.1 ml). After a median waiting period of 11.5 days (range: 6-22 days), the median volume of FLR was increased to 523.4 ml (range: 355.4-833.3 ml). The changes in FLR before and after PMA and PVE were statistically significant (p<0.001). No serious perioperative complications or mortality were found. After a median follow-up time of 51.0 months (range: 2-54 months), the 6-month, 1-year, 2-year, 3-year and 4-year survival rates were 88.9%, 72.2%, 44.4%, 33.3%, 22.2%, respectively, and the median survival time was 15.0 ± 7.1 months. Conclusion: PMA combined with PVE increases FLR rapidly, avoids touching malignant tumors, and produces fewer procedure-related complications. It appears safe and efficacious for planned hepatectomy.

The Hg behaviors in mangrove ecosystems revealed by Hg stable isotopes: a case study of Maowei mangrove.

As one of the most productive marine ecosystems in the tropics and subtropics, mangroves are an important part of the global mercury (Hg) cycling. The environmental processes and effects of Hg in mangroves are complex and affect human Hg exposure, and it is crucial to understand Hg behaviors in the mangrove ecosystem. However, clarifying Hg behaviors in the mangrove ecosystem remains difficult because of an insufficient understanding of the dominant pathways. In this study, measurements of mercury (Hg) concentration and isotope ratios in sediment and plant tissues from a mangrove wetland were used to investigate Hg isotope fractionation in mangrove plants and sediments. Spatial patterns in Hg concentration and isotope signatures indicate that Hg re-emission in the sediment was suppressed by mangrove plants. The ratio of Δ199Hg/Δ201Hg was 0.93 for all sediments, indicating that Hg mass-independent fractionation in the mangrove ecosystem was primarily affected by photoreduction, while the ratios of Δ199Hg/Δ201Hg and Δ199Hg/δ202Hg for plant tissues suggested that natural organic matter reduction of Hg(II) was occurred in the plants. The distinct positive Δ199Hg values found in mangrove plants were supposed to be the results of the unique physiological characteristics of mangroves. The exterior Hg sources from atmosphere and seawater emphasize the role of mangrove ecosystems in the global Hg biogeochemistry. Our study highlights the distinct Hg isotope signatures in the mangrove from that in forests and indicates unique Hg behaviors in the mangrove ecosystem.

Pharmaceuticals and personal care products in the seawater around a typical subtropical tourist city of China and associated ecological risk.

Pharmaceuticals and personal care products (PPCPs) in the sea area surrounding a densely populated tourist city in southeastern China were investigated. In total, 32 PPCP pollutants classified into 23 categories were detected. Different spatial distribution patterns of PPCPs indicated possible contamination from runoff and multiple local sources. The labile-to-conservative ratios of PPCPs showed the influence of untreated domestic sewage. In addition, increased concentrations of ciprofloxacin, enrofloxacin, and erythromycin around aquaculture farms imply that aquaculture cannot be neglected as a source. The concentrations of oxytetracycline, ranitidine, ciprofloxacin, miconazole, and sulfamethizole were higher in the wet season than those in the dry season, and the difference in pharmaceutical consumption was suspected to be the main driving factor of this seasonal variation. The risk quotients calculated with the maximum concentrations of miconazole, triclosan, dehydronifedipine, and triclocarban exceeded 0.1, indicating potential moderate or high risks. Antibacterial agents in daily chemicals and azole broad-spectrum antifungals were associated with the highest risks in this study; this might be another significant pollution characteristic in the sea area around this subtropical tourist city.

linc­ROR facilitates hepatocellular carcinoma resistance to doxorubicin by regulating TWIST1­mediated epithelial­mesenchymal transition.

Long non­coding RNAs are associated with cancer progression. Long intergenic non­protein coding RNA (linc)­regulator of reprogramming (ROR) enhances tumor development in hepatocellular carcinoma (HCC). However, the effect of chemoresistance and its underlying mechanisms in HCC are not completely understood. The present study aimed to identify the effect of ROR on sensitivity to doxorubicin (DOX) in HCC cells. In the present study, Cell Counting Kit­8 and EdU assays were performed to assess cell viability and proliferation, respectively. In addition, E­cadherin and vimentin protein expression levels were assessed via western blotting and immunofluorescence.The results of the present study demonstrated that HCC cells with high linc­ROR expression levels were more resistant to DOX, and linc­ROR knockdown increased HCC cell DOX sensitivity compared with the control group. The results indicated that compared with the NC siRNA group, linc­ROR knockdown notably suppressed epithelial­mesenchymal transition by downregulating twist family bHLH transcription factor 1 (TWIST1) expression. TWIST1 knockdown displayed a similar effect on HCC cell DOX sensitivity to linc­ROR knockdown. Moreover, linc­ROR knockdown­induced HCC cell DOX sensitivity was inhibited by TWIST1 overexpression. The present study provided evidence that linc­ROR promoted HCC resistance to DOX by inducing EMT via interacting with TWIST1. Therefore, linc­ROR might serve as a therapeutic target for reducing DOX resistance in HCC.

Distribution of mercury isotope signatures in Yundang Lagoon, Xiamen, China, after long-term interventions.

Isotope signatures of mercury (Hg) were determined for Hg fractions in seawater, sediments, porewaters, core sediments and fish from the Yundang Lagoon, Xiamen, China. Sequential extraction was used to extract Hg fractions in sediments and the purge-trap method was used to preconcentrate Hg in seawater. A large variation in mass dependent fractionation (δ202Hg: -2.50‰ to -0.36‰) was observed in the lagoon. Seawater and fish samples showed positive mass-independent fractionation (Δ199Hg: -0.06‰-0.45‰), while most of sediment and porewater samples displayed insignificant mass-independent fractionation (Δ199Hg: -0.10‰-0.07‰). Ancillary parameters (total organic carbon, sulfide, pH, Eh, water content and grain size) were also measured in the sediments to investigate correlations with Hg isotopes. Three sources (domestic sewage, sediments and atmospheric deposition) were identified as the main sources of Hg in the lagoon seawater. Photochemical reaction was the main process causing isotope fractionation in seawater. Through Hg partitioning and deposition, light isotopes were enriched from dissolved Hg to particulate Hg, then to sediments, and then to porewaters. Finally, Hg isotope signatures were used to identify the Hg sources and fractionation processes in core sediments from different depths. Our results demonstrate that Hg isotopes are powerful tools for tracing Hg sources and arriving at a better understanding of Hg biogeochemical cycling in the lagoon after long-term interventions.

A nationwide assessment of litter on China's beaches using citizen science data.

China is the largest plastic consumer in the world. Despite its plastic waste import ban in 2017, this populous economy inevitably generates a large amount of waste, including plastic waste, a considerable part of which has become marine litter. Data from the 2018 National Coastal Cleanup and Monitoring Project, the largest beach litter monitoring activities using the citizen science approach in China, have been retrieved and analyzed to understand spatial patterns, composition, and original usage of marine litter. Within this project, 24 beaches were surveyed every two months. As a result, the mean density was 3.85 ± 5.39 items m-2, much higher than that reported by previous studies in China. There were great differences in the spatial distribution of litter. The highest densities appeared in the runoff-affected area of the Yangtze River, which was another difference from previous studies. Low-density, easy-to-transport foamed plastics were the major contributor to marine litter in these areas. Along China's coast, approximately 90% of litter was from land-based sources, and over half of that originated from domestic sources. Including foamed plastic products, plastic litter with low recycling value dominated. Both natural and human factors influencing the spatiotemporal distribution and composition of litter are discussed. Socioeconomic factors, such as the lifestyle and consumption levels of citizens and local waste management systems, are possible explanations for the low-value characteristic of marine litter. The deviation between previous data and citizen science data in this study may be caused by many factors. Based on the discussion on these factors, some suggestions for citizen science research in China are also put forward.

Study of mercury transport and transformation in mangrove forests using stable mercury isotopes.

Mangrove forests are important wetland ecosystems that are a sink for mercury from tides, rivers and precipitation, and can also be sources of mercury production and export. Natural abundance mercury stable isotope ratios have been proven to be a useful tool to investigate mercury behavior in various ecosystems. In this study, mercury isotopic data were collected from seawater, sediments, air, and plant tissues in two mangrove forests in Guangxi and Fujian provinces, China, to study the transport and transformation of mercury in mangrove sediments. The mangroves were primarily subject to mercury inputs from external sources, such as anthropogenic activities, atmospheric deposition, and the surrounding seawater. An isotope mixing model based on mass independent fractionation (MIF) estimated that the mangrove wetland ecosystems accounted for <40% of the mercury in the surrounding seawater. The mercury in plant root tissues was derived mainly from sediments and enriched with light mercury isotopes. The exogenous mercury inputs from the fallen leaves were diluted by seawater, leading to a positive Δ199Hg offset between the fallen leaves and sediments. Unlike river and lake ecosystems, mangrove ecosystems are affected by tidal action, and the δ202Hg and Δ199Hg values of sediments were more negative than that of the surrounding seawater. The isotopic signature differences between these environmental samples were partially due to isotope fractionation driven by various physical and chemical processes (e.g., sorption, photoreduction, deposition, and absorption). These results contribute to a better understanding of the biogeochemical cycling of mercury in mangrove wetland ecosystems.

Microplastic abundance, distribution and composition in the mid-west Pacific Ocean.

Microplastic pollution is widespread across most ocean basins around the world. Microplastics (MPs) are small plastic particles that have a significant impact on the marine environment. Various research on plastic pollution have been conducted in several regions. However, currently, there is limited data on the distribution and concentration of MPs in the mid-west Pacific Ocean. Therefore, this study we investigated the abundance, distribution, characteristics, and compositions of MPs in this region. Sea surface water samples collected from 18 stations showed a microplastic concentration range of 6028-95,335 pieces/km2 and a mean concentration of 34,039 ± 25,101 pieces/km2. Highest microplastic concentrations were observed in the seamount region of western Pacific. We observed a significant positive correlation between microplastic abundance and latitude across the study region. It was observed that microplastic concentrations decreased with increasing offshore distance at sites located on a 154° W transect. Fibres/filaments were the dominant microparticles observed in this study (57.4%), followed by fragments (18.3%). The dominant particle size range was 1-2.5 mm (35.1%), followed by 0.5-1 mm (28.5%), and the dominant particle colour was white (33.8%), followed by transparent (31.0%) and green (24.6%). The most common polymer identified by µ-Raman was polypropylene (39.1%), followed by polymethyl methacrylate (16.2%), polyethylene (14.1%) and polyethylene terephthalate (14.2%). The possible sources and pathways of microplastics in the study area were proposed based on the morphological and compositional characteristics of particles, their spatial distribution patterns, and shipboard current profiling (ADCP). Our study contributes to the further understanding of MPs in remote ocean areas.