Bioconcentration of Inorganic and Methyl Mercury by Algae Revealed Using Dual-Mass Single-Cell ICP-MS with Double Isotope Tracers.

Algae are an entry point for mercury (Hg) into the food web. Bioconcentration of Hg by algae is crucial for its biogeochemical cycling and environmental risk. Herein, considering the cell heterogeneity, we investigated the bioconcentration of coexisting isotope-labeled inorganic (199IHg) and methyl Hg (201MeHg) by six typical freshwater and marine algae using dual-mass single-cell inductively coupled plasma mass spectrometry (scICP-MS). First, a universal pretreatment procedure for the scICP-MS analysis of algae was developed. Using the proposed method, the intra- and interspecies heterogeneities and the kinetics of Hg bioconcentration by algae were revealed at the single-cell level. The heterogeneity in the cellular Hg contents is largely related to cell size. The bioconcentration process reached a dynamic equilibrium involving influx/adsorption and efflux/desorption within hours. Algal density is a key factor affecting the distribution of Hg between algae and ambient water. Cellular Hg contents were negatively correlated with algal density, whereas the volume concentration factors almost remained constant. Accordingly, we developed a model based on single-cell analysis that well describes the density-driven effects of Hg bioconcentration by algae. From a novel single-cell perspective, the findings improve our understanding of algal bioconcentration governed by various biological and environmental factors.

Digital health integration for noncommunicable diseases: Comprehensive process mapping for full-life-cycle management.

AIM: To create a systematic digital health process mapping framework for full-life-cycle noncommunicable disease management grounded in key stakeholder engagement. METHODS: A triphasic, qualitative methodology was employed to construct a process mapping framework for digital noncommunicable disease management in Shanghai, China. The first phase involved desk research to examine current guidance and practices. In the second phase, pivotal stakeholders participated in focus group discussions to identify prevalent digital touchpoints across lifetime noncommunicable disease management. In the final phase, the Delphi technique was used to refine the framework based on expert insights and obtain consensus. RESULTS: We identified 60 digital touchpoints across five essential stages of full-life-cycle noncommunicable disease management. Most experts acknowledged the rationality and feasibility of these touchpoints. CONCLUSIONS: This study led to the creation of a comprehensive digital health process mapping framework that encompasses the entire life cycle of noncommunicable disease management. The insights gained emphasize the importance of a systemic strategic, person-centered approach over a fragmented, purely technocentric approach. We recommend that healthcare professionals use this framework as a linchpin for efficient disease management and seamless technology incorporation in clinical practice.

Single-cell multi-element analysis reveals element distribution pattern in human sperm.

Multiple elements in human sperm have been demonstrated to play significant roles in the reproductive process, but their simultaneous detection in single cells remains challenging. We propose a novel analytical procedure using single-cell inductively coupled plasma-time of flight-mass spectrometry (scICP-TOF-MS) to simultaneously quantify multiple elements of individual sperm cells. A promising label-free cell identification strategy based on the endogenous element was developed to obtain valid data. The element contents exhibited varied degrees of heterogeneity in single cells. Machine learning-based analysis of the multi-dimension dataset indicated different distribution patterns and physiological roles among the simultaneously detected elements.

Exploring the performance of quadrupole, time-of-flight, and multi-collector ICP-MS for dual-isotope detection on single nanoparticles and cells.

To meet the demand for multi-element/isotope analysis at the single nanoparticle (NP) or cell level, different types of inductively coupled plasma mass spectroscopy (ICP-MS) have been used to simultaneously monitor multiple mass-to-charge ratios in single-particle/cell ICP-MS (SP/SC-ICP-MS) analysis. Systematic evaluation and comparison of the performance of these techniques are urgently required. Herein, three ICP-quadrupole (Q)-MS, two ICP-time of flight (TOF)-MS, and one multi-collector (MC)-ICP-MS instruments were employed to simultaneously detect 107Ag and 109Ag on single Ag NPs and Ag-exposed cyanobacteria cells. The evaluation was conducted by comparing the measured event-specific 109Ag:107Ag ratios with the natural ratio. Duration of NP or cell events and time resolution in the peak hopping mode were the main factors affecting the performance of ICP-Q-MS. Under the optimal condition (100 µs for both dwell time and settling time), less than 45% of the NP or cell events had a 109Ag:107Ag ratio deviating <30% from the natural ratio. Most events obtained via ICP-TOF-MS were paired events with both isotopes detected. For large-size NPs and cells with high exposure levels, nearly 80% of the events had a ratio deviation within ±30%. MC-ICP-MS performed particularly well in isotope determination with all the events having a ratio deviation within ±5%. For ICP-TOF-MS and MC-ICP-MS, the signal intensity of the events was the main factor affecting the accuracy of the measured 109Ag:107Ag ratios due to the counting statistics. The established methods and results provide insight on the analyses of two elements/isotopes or more on single NPs or cells. Based on the comparison of the advantages and limitations of these instruments, this study provides a critical reference for future multi-element/isotope SP/SC-ICP-MS analyses.

Attitudes and perspectives of 534 Chinese pediatricians toward internet hospitals.

Background: Internet hospitals introduced in China have effectively reduced service time and space, promoted high-quality pediatric medical resources to grassroots areas, solved the contradiction between supply and demand of pediatric medical resources, and met patients' increasing multi-level and diversified medical service needs. However, pediatricians' attitudes toward and satisfaction with the use of internet hospitals remain unknown. Objective: This study aimed to investigate pediatricians' knowledge of, use of, and satisfaction with internet hospitals in order to identify major issues in internet hospital development, and to understand pediatricians' attitudes and opinions on the construction, development, and use of internet hospitals. Materials and methods: A total of 625 pediatricians in 17 public tertiary hospitals in Shanghai were surveyed from November 1-30, 2021. Five hundred and thirty four pediatricians completed the survey, and the response rate was 85.44%. Pediatricians' baseline demographic data were collected and information about their use of and satisfaction with internet hospitals. Results: About 70.22% (375/534) of pediatricians knew about internet hospitals and about 54.68% (292/534) use internet hospitals for patient consultation, diagnosis, and treatment. Utilized services mainly focused on online consultation (271/292, 92.81%), online follow-up consultation (174/292, 59.59%), and health sciences (111/292, 38.01%). Online services were provided by 69.18% (202/292) of pediatricians for less than 1 h a day, and 75.00% (219/292) responded to fewer than five patient consultations online every day. Pediatricians' overall satisfaction with internet hospitals was low (3.59 ± 0.92 points), user experience, systems functions, operation processes, service prices, and performance rewards of internet hospitals were main influencing factors. Pediatricians are enthusiastic about further development of internet hospitals, with 87.83% (469/534) willing to provide services on the internet hospital platform. Conclusion: Most pediatricians view internet hospitals favorably and are eager to contribute to the development of online diagnosis and treatment services. The development of internet hospitals will be more strongly supported by improving pediatricians' satisfaction and mobilizing their enthusiasm and initiative to participate in internet medical services.

Effect of ondansetron for preventing postoperative nausea and vomiting after breast cancer surgery.

OBJECTIVE: To evaluate the preventive effect of preoperative administration of ondansetron on postoperative nausea and vomiting (PONV) in patients receiving breast cancer surgery. METHODS: Data from 225 patients who received modified radical mastectomy from January 2019 to December 2020 were retrospectively reviewed. The patients were divided into an ondansetron group and a control group according to whether they received preoperative ondansetron or not. The incidence of PONV, visual analog scale (VAS) score, the rescue analgesics use and rescue antiemetic use, as well as the patient satisfaction degree about their PONV were compared between the two groups. RESULTS: The ondansetron group showed lower total incidence of PONV, lower VAS score at 6 h post-operation as well as less rescue antiemetic use than the control group (P<0.05). Patients in the ondansetron group were more satisfied with their PONV condition than those in the control group (P<0.05). CONCLUSION: Preoperative administration of ondansetron can prevent PONV and relieve pain 2-24 hours after breast cancer surgery.

A Novel Triphenylamine-Based Flavonoid Fluorescent Probe with High Selectivity for Uranyl in Acid and High Water Systems.

Developing a fluorescent probe for UO22+, which is resistant to interference from other ions such as Cu2+ and can be applied in acidic and high-water systems, has been a major challenge. In this study, a "turn-off" fluorescent probe for triamine-modified flavonoid derivatives, 2-triphenylamine-3-hydroxy-4H-chromen-4-one (abbreviated to HTPAF), was synthesized. In the solvent system of dimethyl sulfoxide:H2O (abbreviated to DMSO:H2O) (v/v = 5:95 pH = 4.5), the HTPAF solution was excited with 364 nm light and showed a strong fluorescence emission peak at 474 nm with a Stokes shift of 110 nm. After the addition of UO22+, the fluorescence at 474 nm was quenched. More importantly, there was no interference in the presence of metal ions (Pb2+, Cd2+, Cr3+, Fe3+, Co2+, Th4+, La3+, etc.), especially Cu2+ and Al3+. It is worth noting that the theoretical model for the binding of UO22+ to HTPAF was derived by more detailed density functional theory (DFT) calculations in this study, while the coordination mode was further verified using HRMS, FT-IR and 1HNMR, demonstrating a coordination ratio of 1:2. In addition, the corresponding photo-induced electron transfer (PET) fluorescence quenching mechanism was also proposed.

Study of ultrasound-guided ropivacaine combined with butorphanol continuous paravertebral block to prevent pain syndrome by evaluating ccl2 gene expression after radical mastectomy.

This study aimed to investigate the clinical effect of ultrasound-guided ropivacaine combined with butorphanol continuous paravertebral block in preventing postoperative pain syndrome of breast cancer. For this purpose, 100 women treated for breast cancer from April 2018 to July 2019 were enrolled as research objects. Surgical procedures included local sentinel lymph node biopsy, mastectomy, sentinel lymph node biopsy for mastectomy, modified radical mastectomy, and implantation. The selected patients were randomly divided into two groups: control group (routine operation anesthesia; n = 50) and observation group (ultrasound-guided thoracic paravertebral block before induction of ropivacaine+butorphanol anesthesia; n = 50). The Real-time PCR technique was performed to evaluate CCL2 gene expression. VAS scores were recorded during the postoperative period. Compared with the control group, the observation group had lower VAS scores at six h, 24h, and 48h (P<0.05). The pain effect of the observation group was less than that of the control group. The observation group had better analgesic effects after anesthesia. The observation group had a lower incidence of pain syndrome at the 6th, 8th, and 12th months (P<0.05), and the incidence of pain syndrome in the two groups decreased with the extension of time. The observation group had lower levels of related factors (P<0.05), and the observation group had lower traumatic stress responses. The protein expression of IL-6, IL-17, and CRP in the observation group was lower than that in the control group (P<0.05). The results of CCL2 gene expression also showed that gene expression in the control group increased significantly (P=0.0047). Since the expression of this gene is one of the factors that stimulate pain signals in the body, the method used in the present study was able to reduce the amount of pain significantly. Therefore, the combination of ropivacaine combined with butorphanol ultrasound-assisted paravertebral block can reduce the intensity of postoperative pain in patients with breast cancer surgery, decrease the incidence of pain syndrome, and increase pain tolerance.

Numerical Study on the Evaporation of a Non-Spherical Sessile Droplet.

To better understand the evaporation of a non-spherical droplet, a two-dimensional simulation was conducted to investigate the evaporation on the asymmetric cross-section of non-spherical sessile droplets, which are characterized by two curvatures with two different contact angles on both sides. The temperature distribution, internal flow, and evaporation flux distribution at a quasi-steady state were revealed to be different from the spherical droplets. When heated from the substrate, the lowest surface temperature moves to the side of higher curvature or larger contact angle, forming a single vortex in the droplet. This single-vortex formation continues to be enhanced by enlarging the contact angle discrepancy. Unlike spherical droplets, the smaller curvature side of a non-spherical sessile droplet will release more evaporation flux. In addition, it is found that the non-spherical sessile droplets could surpass the spherical sessile droplets in evaporation flux.

Wildfire Smoke Classification Based on Synthetic Images and Pixel- and Feature-Level Domain Adaptation.

Training a deep learning-based classification model for early wildfire smoke images requires a large amount of rich data. However, due to the episodic nature of fire events, it is difficult to obtain wildfire smoke image data, and most of the samples in public datasets suffer from a lack of diversity. To address these issues, a method using synthetic images to train a deep learning classification model for real wildfire smoke was proposed in this paper. Firstly, we constructed a synthetic dataset by simulating a large amount of morphologically rich smoke in 3D modeling software and rendering the virtual smoke against many virtual wildland background images with rich environmental diversity. Secondly, to better use the synthetic data to train a wildfire smoke image classifier, we applied both pixel-level domain adaptation and feature-level domain adaptation. The CycleGAN-based pixel-level domain adaptation method for image translation was employed. On top of this, the feature-level domain adaptation method incorporated ADDA with DeepCORAL was adopted to further reduce the domain shift between the synthetic and real data. The proposed method was evaluated and compared on a test set of real wildfire smoke and achieved an accuracy of 97.39%. The method is applicable to wildfire smoke classification tasks based on RGB single-frame images and would also contribute to training image classification models without sufficient data.

Improvement in outpatient services using the WeChat calling system in the Shanghai Children's Hospital.

OBJECTIVES: We explored the utility of WeChat applet as part of the Outpatient Department (OPD) to provide patients with timely queuing information and compared it with the traditional calling system. METHODS: Data for the WeChat calling system was extracted for the period of May 2018 to September 2018. Data for the traditional system was extracted for the same period from the year 2017. We compared the effective patient waiting time and nurse idle time i.e. nonproductive time spent on factors outside of employees' control with the two systems. We also analyzed the relationship between the length of waiting time and conflicts between doctors and patients. RESULTS: The mean wait time for the traditional calling system was 126 minutes, while the average idle time for nurses was 96 minutes/day. On the other hand, the mean wait time for the WeChat calling system was 33 minutes, and the average idle time for nurses was 72 minutes/day. The incremental profit (cost of traditional calling system - cost of WeChat calling system) achieved from switching systems was 13,879 yuan/month. Behavioral observations showed that wait time (OR=2.745, 95%CI 1.936~3.892 P<0.0001) was a risk factor for staff-patient conflict. CONCLUSION: The cost of the WeChat calling system was significantly lower than the traditional system. Also, the traditional calling system was time-consuming. Longer waiting time was the main factor affecting OPD quality and caused conflicts between doctors and patients.

Development and Evaluation of a Combined Immunoassay Method Based on a Stable Isotope Tagging Strategy and Inductively Coupled Plasma Mass Spectrometry for Detecting Human Chorionic Gonadotropin.

BACKGROUND: The development of a combined immunoassay method, based on a stable isotope tagging strategy and inductively coupled plasma mass spectrometry (ICP-MS), has created options for quantitative bioanalysis. The aim of the study was to develop a combined immunoassay, featuring ICP-MS and a stable element labeling strategy, for the detection of human chorionic gonadotropin (HCG), and developed methodology applicable for clinical practice. METHODS: In accordance with guidelines published by the Clinical and Laboratory Standards Institute (CLSI), we developed our assay and then evaluated its analytical performance, including the limit of detection (LOD), the upper limit of quantification (ULoQ), linearity, precision, recovery, cross reactivity, and interference. Next, we collected 130 clinical samples for analysis with the new assay. The data derived from our assay were then compared with those derived by an existing electrochemiluminescence immunoassay (ECLIA). RESULTS: The LOD of the assay was 0.33 mIU/mL and the ULoQ was 11,300 mIU/mL. The coefficient of determina-tion of linearity was higher than 0.99 in the range of 1 to 8,917 mIU/mL (R2 = 0.9964). The obtained recoveries ranged from 97.08% to 103.50%, while the intra-assay imprecision of high value samples and low value samples were 2.97% and 6.08%, respectively. The inter-assay imprecision of high value samples and low value samples were 3.98% and 7.08%, respectively. Interference test results deviated by less than ± 10% in the presence of hemoglobin ≤ 2 g/L, bilirubin ≤ 274 mol/L, or triglycerides ≤ 37 mmol/L. Compared with the commercial ECLIA method for clinical sample detection, the proposed method showed a significant correlation (R2 = 0.9770) and satisfactory agreement. CONCLUSIONS: The combination of ICP-MS and a stable element labeling based immunoassay for HCG detection was established successfully and the general performance of this system was acceptable, thus indicating that the assay has potential for the clinical application.

Evaluation of an Element-Tagged Duplex Immunoassay Coupled with Inductively Coupled Plasma Mass Spectrometry Detection: A Further Study for the Application of the New Assay in Clinical Laboratory.

BACKGROUND: Element-tagged immunoassay coupled with inductively coupled plasma mass spectrometry (ICP-MS) detection has the potential to revolutionize immunoassay analysis for multiplex detection. However, a further study referring to the standard evaluation and clinical sample verification is needed to ensure its reliability for simultaneous analysis in clinical laboratories. METHODS: Carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) were chosen for the duplex immunoassay. The performance of the assay was evaluated according to guidelines from the Clinical and Laboratory Standards Institute (CLSI). Moreover, reference intervals (RIs) of CEA and AFP were established. At last, 329 clinical samples were analyzed by the proposed method and results were compared with those obtained with electrochemiluminescent immunoassay (ECLIA) method. RESULTS: The measurement range of the assay was 2-940 ng/mL for CEA and 1.5-1000 ng/mL for AFP, with a detection limit of 0.94 ng/mL and 0.34 ng/mL, respectively. The inter-assay and intra-assay imprecision were all less than 6.58% and 10.62%, respectively. The RI of CEA and AFP was 0-3.84 ng/mL and 0-9.94 ng/mL, respectively. Regarding to clinical sample detection, no significant difference was observed between the proposed duplex assay and the ECLIA method. CONCLUSIONS: The ICP-MS-based duplex immunoassay was successfully developed and the analytical performance fully proved clinical applicability. Well, this could be different with other analytes.

Very High Cycle Fatigue (VHCF) Characteristics of Carbon Fiber Reinforced Plastics (CFRP) under Ultrasonic Loading.

A liquid nitrogen cooling system was developed to ensure the successful ultrasonic testing of composite materials to characterize the very High Cycle Fatigue (VHCF) of carbon fiber reinforced plastics (CFRP). The fatigue failure of CFRP occurs even in the very high cycle range and there is no traditional fatigue limit. The S-N curve of the CFRP presents a step whose characteristics appear in the transition between high cycle and very high cycle fatigue. The damage evolution of CFRP in the same field of view is investigated. The morphology of damaged CFRP composites under ultrasonic loading is described by three characteristics: matrix damage at the intersection of fiber bundles, near fiber bundle parallel section matrix cavity and matrix penetration. With the increasing of cycles, the damage process is also presented in turn according to these three characteristics. The post-fatigue bending modulus changed significantly from the pre-fatigue values, indicating that the VHCF had a considerable impact on the mechanical properties of the composite. An evolution threshold was introduced from the S-N curve to determine the fatigue evolution law from the high cycle regime to the very high cycle regime.

Development and evaluation of an element-tagged immunoassay coupled with inductively coupled plasma mass spectrometry detection: can we apply the new assay in the clinical laboratory?

Introduction Element-tagged immunoassay coupled with inductively coupled plasma-mass spectrometry (ICP-MS) detection has the potential to revolutionize immunoassay analysis in clinical detection; however, a systematic evaluation with the standard guidelines of the assay is needed to ensure its performance meets the requirements of the clinical laboratory. Methods Carcinoembryonic antigen (CEA) was chosen for analysis using the proposed method. A systematic evaluation of the proposed assay was carried out according to the Clinical and Laboratory Standards Institute (CLSI). The 469 clinical samples were analyzed using the new method and compared with the electrochemiluminescent immunoassay (ECLIA) method. Results The measurement range of the assay was 1-900 ng/mL, with a detection limit of 0.83 ng/mL. The inter-assay and intra-assay imprecision were 4.67% and 5.38% with high concentration samples, and 9.27% and 17.64% with low concentration samples, respectively. The cross-reactivity (%) for different antigens was less than 0.05%, and the recovery was between 94% and 108%. Percentage deviation of all the dilutions was less than 12.5% during linearity estimation. The interference bias caused by different substances was less than 10%. The reference interval of the assay was 0-4.442 ng/mL. Comparison with the commercial ECLIA method for clinical sample detection, the proposed method showed a correlation of 0.9878 and no significant differences between the methods were observed (p = 0.6666). Conclusions The ICP-MS based immunoassay was successfully developed, and the analytical performance of the assay met the requirements of the CLSI, which fully proved the clinical transferability and application of the new method.

Effect of lung protective ventilation on perioperative pulmonary infection in elderly patients with mild to moderate COPD under general anesthesia.

OBJECTIVE: The research aims to explore the effects of different ventilation time on postoperative pulmonary infection in elderly patients with the mild and moderate chronic pulmonary obstructive disease (COPD), so as to provide evidence for reducing postoperative pulmonary infection complications in patients with COPD. METHODS: 120 elderly patients with mild and moderate COPD were selected as the research objects. First, the general information of patients with COPD before surgery and the difference between healthy population and lung forced expiratory volume in 1s (FEV1), forced vital capacity (FVC), FEV1/FVC and maximum midexpiratory flow (MMEF) functional indexes were analyzed and detected. Patients with COPD were operated on with single lung ventilation and general anesthesia. Patients with mild and moderate COPD were divided into two groups according to lung ventilation time (ventilation time 1.0-2.0h group, ventilation time >2.0h group). The inflammatory factors of IL-6, IL-21, TNF-α, and CXCL13 as well as inflammatory indicators of polycaprolactam (PCT), C-reactive protein (CRP) and white blood cell (WBC) in serum of all patients were detected after the operation. The probability of pulmonary infection after COPD was diagnosed and analyzed. Finally, the regression analysis of postoperative pulmonary infection in COPD patients was analyzed. RESULTS: (1) The results showed that the smoking rate of mild and COPD patients was significantly higher than that of healthy people (P<0.05). (2) The lung function indexes of the mild and moderate groups were significantly lower than those of the control group (P<0.01), while the lung function indexes of the moderate group were significantly lower than those of the mild group (P<0.05). (3) All the inflammatory indicators of moderate COPD patients were significantly higher than those of mild COPD patients (P<0.05). (4) All inflammation-related indicators in patients with mild and moderate COPD with ventilation time of >2.0h were significantly higher than those in the 1.0-2.0h group (P<0.05). (5) The probability of postoperative pulmonary infection in moderate patients was significantly higher than that in mild patients (P<0.01). The probability of postoperative pulmonary infection in >2.0h group was significantly higher than that in the 1.0-2.0h group (P<0.01). (6) Multivariate Logistic regression analysis results showed that lung function, duration of lung ventilation and smoking were independent risk factors for postoperative pulmonary infection in COPD patients. CONCLUSION: It is important to detect pulmonary function before surgery, maintain single lung ventilation protection for no more than 2.0h during surgery, and quit smoking to improve pulmonary infection in patients with COPD after surgery. In addition, the incidence of postoperative pulmonary infection in patients with moderate COPD was higher than that in patients with mild COPD, suggesting that early treatment in patients with COPD was also of great significance in reducing the incidence of postoperative pulmonary infection.

The Effect of Microstructure and Axial Tension on Three-Point Bending Fatigue Behavior of TC4 in High Cycle and Very High Cycle Regimes.

The effects of microstructure and axial tension on the fatigue behavior of TC4 titanium alloy in high cycle (HCF) and very high cycle (VHCF) regimes are discussed in this paper. Ultrasonic three-point bending fatigue tests at 20 kHz were done on a fatigue life range among 105109 cycles of the alloys with equiaxed, bimodal and Widmanstatten microstructures. Experimental results without axial tension show that three typical shapes of S-N curves clearly present themselves for the three different microstructures. Moreover, the crack initiation sites abruptly shifted from surface to subsurface of the specimen in the very high cycle fatigue regime for equiaxed and bimodal microstructures. But for the Widmanstatten microstructure, both surface and subsurface crack initiation appeared in the high cycle fatigue regime, and the multi-points crack initiation was found in the bimodal microstructure. The subsurface fatigue crack originated from the αp grains in equiaxed and bimodal microstructures. However, it originated from the coarse grain boundary α in the Widmanstatten microstructure. Additionally, the S-N curve shape, fatigue life and fatigue crack initiation mechanism with axial tension are similar to that without axial tension. However, the crack origin point shifts inward with axial tension.

Geochemical modeling of mercury speciation in surface water and implications on mercury cycling in the everglades wetland.

The geochemical model PHREEQC, abbreviated from PH (pH), RE (redox), EQ (equilibrium), and C (program written in C), was employed on the datasets generated by the USEPA Everglades Regional Environmental Monitoring and Assessment Program (R-EMAP) to determine the speciation distribution of inorganic mercury (iHg) in Everglades water and to explore the implications of iHg speciation on mercury cycling. The results suggest that sulfide and DOM were the key factors that regulate inorganic Hg speciation in the Everglades. When sulfide was present at measurable concentrations (>0.02 mg/L), Hg-S complexes dominated iHg species, occurring in the forms of HgS22-, HgHS2-, and Hg(HS)2 that were affected by a variety of environmental factors. When sulfide was assumed nonexistent, Hg-DOM complexes occurred as the predominant Hg species, accounting for almost 100% of iHg species. However, when sulfide was presumably present at a very low, environmentally relevant concentration (3.2 × 10-7 mg/L), both Hg-DOM and Hg-S complexes were present as the major iHg species. These Hg-S species and Hg-DOM complex could be related to methylmercury (MeHg) in environmental matrices such floc, periphyton, and soil, and the correlations are dependent upon different circumstances (e.g., sulfide concentrations). The implications of the distribution of iHg species on MeHg production and fate in the Everglades were discussed.

Tracing the Uptake, Transport, and Fate of Mercury in Sawgrass ( Cladium jamaicense) in the Florida Everglades Using a Multi-isotope Technique.

The role of macrophytes in the biogeochemical cycle of mercury (Hg) in the Florida Everglades is poorly understood. Stable isotope tracer techniques were employed to investigate Hg uptake by sawgrass ( Cladium jamaicense) from soil and atmospheric pathways and the fate of Hg after absorption. Our results suggest that soil spiked 201Hg2+ was rapidly taken up by roots and transported to aboveground parts. The spiked 201Hg that was transported to the aboveground parts was trapped; no release of the spiked 201Hg from the leaf to the air was detected. Atmospheric 199Hg0 exposure experiments revealed that the majority of the previously deposited 199Hg0 taken into the leaf was fixed, with a very limited proportion (1.6%) available for re-emission to the atmosphere. The percentage of 199Hg0 fixed in the leaf will help reduce the model uncertainty in estimating the Hg0 exchange over the air-vegetation surface. We propose that sawgrass needs to be viewed as an important sink for atmospheric Hg0 in the regional Hg mass balance; this would have important implications for the critical loads of Hg to the Everglades. The multi-isotope tracer technique could be an effective tool to identify the role of plants in biogeochemical cycling of Hg in other ecosystems.

Occurrence of Methylmercury in Rice-Based Infant Cereals and Estimation of Daily Dietary Intake of Methylmercury for Infants.

Recent reports of elevated levels of methylmercury (MeHg) in rice revealed the possible occurrence of MeHg in infant rice cereals, leading to potential MeHg exposure through cereal consumption. Total mercury (THg) and MeHg levels in 119 infant cereal samples commonly marketed in the United States and China and estimated daily intake of MeHg through cereal consumption were determined. Concentrations of THg and MeHg in the tested cereal samples ranged from 0.35 to 15.9 µg/kg and from 0.07 to 13.9 µg/kg with means of 2.86 and 1.61 µg/kg, respectively. Rice-based cereals contained MeHg levels significantly higher than those of nonrice cereals, indicating that MeHg in rice could be source of MeHg in cereals. Cereal consumption could be a potential pathway of MeHg exposure for infants, as the EDI through cereal consumption amounted to 4-122% of the MeHg reference dose, suggesting the necessity of further evaluation of the potential health risk of dietary MeHg exposure to infants.