Establishment of a Multiplex Detection Method for Common Bacteria in Blood Based on Human Mannan-Binding Lectin Protein-Conjugated Magnetic Bead Enrichment Combined with Recombinase-Aided PCR Technology.

Objective: Recombinase-aided polymerase chain reaction (RAP) is a sensitive, single-tube, two-stage nucleic acid amplification method. This study aimed to develop an assay that can be used for the early diagnosis of three types of bacteremia caused by Staphylococcus aureus (SA), Pseudomonas aeruginosa (PA), and Acinetobacter baumannii (AB) in the bloodstream based on recombinant human mannan-binding lectin protein (M1 protein)-conjugated magnetic bead (M1 bead) enrichment of pathogens combined with RAP. Methods: Recombinant plasmids were used to evaluate the assay sensitivity. Common blood influenza bacteria were used for the specific detection. Simulated and clinical plasma samples were enriched with M1 beads and then subjected to multiple recombinase-aided PCR (M-RAP) and quantitative PCR (qPCR) assays. Kappa analysis was used to evaluate the consistency between the two assays. Results: The M-RAP method had sensitivity rates of 1, 10, and 1 copies/µL for the detection of SA, PA, and AB plasmids, respectively, without cross-reaction to other bacterial species. The M-RAP assay obtained results for < 10 CFU/mL pathogens in the blood within 4 h, with higher sensitivity than qPCR. M-RAP and qPCR for SA, PA, and AB yielded Kappa values of 0.839, 0.815, and 0.856, respectively ( P < 0.05). Conclusion: An M-RAP assay for SA, PA, and AB in blood samples utilizing M1 bead enrichment has been developed and can be potentially used for the early detection of bacteremia.

A Multiplex Recombinase-Aided qPCR Assay for Highly Sensitive and Rapid Detection of khe, blaKPC -2, and blaNDM -1 Genes in Klebsiella pneumoniae.

OBJECTIVE: This study aimed to establish a highly sensitive and rapid single-tube, two-stage, multiplex recombinase-aided qPCR (mRAP) assay to specifically detect the khe, blaKPC-2, and blaNDM-1 genes in Klebsiella pneumoniae. METHODS: mRAP was carried out in a qPCR instrument within 1 h. The analytical sensitivities of mRAP for khe, blaKPC-2, and blaNDM-1 genes were tested using recombinant plasmids and dilutions of reference strains. A total of 137 clinical isolates and 86 sputum samples were used to validate the clinical performance of mRAP. RESULTS: mRAP achieved the sensitivities of 10, 8, and 14 copies/reaction for khe, blaKPC-2, and blaNDM-1 genes, respectively, superior to qPCR. The Kappa value of qPCR and mRAP for detecting khe, blaKPC-2, and blaNDM-1 genes was 1, 0.855, and 1, respectively (p < 0.05). CONCLUSION: mRAP is a rapid and highly sensitive assay for potential clinical identification of khe, blaKPC-2, and blaNDM-1 genes in K. pneumoniae.

[Accumulation Characteristics, Sources, and Health Risks of Soil Lead of Urban Parks in Beijing].

Urban parks have multiple functions such as social culture, economy, and environmental services during urban development. The rapid development of cities and economy may lead to the accumulation of heavy metals in the soil of urban parks, which may threaten human health. A total of 140 soil samples were collected in 32 typical parks in Beijing. The accumulation characteristics of Pb in the soil of urban parks were analyzed using the single-factor pollution and geo-accumulation indices. The sources of Pb pollution in soils were quantitatively analyzed using the stable isotope of Pb, and the health risk was assessed using the probabilistic risk assessment method based on Monte Carlo simulation. The results showed that the geometric mean of Pb in soils of urban parks in Beijing was 38.63 mg·kg-1, which was 1.48 times the background value. However, it did not exceed the risk screening value(GB 36600-2018). The accumulation of soil Pb in urban parks increased with the increase in the proximity between the park and the central urban area and the increase in the establishment time. The soil Pb pollution index of 2 ring, 2-4 ring, and 4-6 ring parks were 0.16, 0.10, and 0.09, which did not reach the pollution level, and the geo-accumulation indices were 0.80, 0.07, and -0.31, respectively. Except for the no-moderate pollution level in ring 2 and ring 2 to ring 4, the other rings did not reach the pollution level. The sources of Pb pollution in urban parks were coal combustion, road dust, and paint, with the contributions of 45.4%, 19.6%, and 13.9%, respectively. The 95% quantiles of hazard index(HI) of soil Pb in the park for different age groups were 1.11E-01, 8.57E-02, 6.39E-02, 1.64E-02, 1.36E-02, 1.26E-02, 1.64E-02, and 1.78E-02, respectively, which indicated that there was no potential non-carcinogenic risk(HI<1). Exposure duration was the most sensitive to non-carcinogenic risks in people aged 0-18 years, and soil Pb concentration was the most sensitive to non-carcinogenic risks in people aged 18-80 years. The increase in body weight often reduced the non-carcinogenic risks. These results can provide theoretical basis for soil environmental risk control in urban parks.

Approaches to reconstruction of inferior vena cava by ex vivo liver resection and autotransplantation in 114 patients with hepatic alveolar echinococcosis.

BACKGROUND: Hepatic alveolar echinococcosis (AE) is most commonly found in retrohepatic inferior vena cava (RHIVC). Ex vivo liver resection and autotransplantation (ELRA) can better realize the radical resection of end-stage hepatic AE with severely compromised hepatocaval confluences, and reconstruction of the affected vessels. Currently, there is a scarcity of information regarding RHIVC reconstruction in ELRA. AIM: To propose reasonable RHICV reconstruction strategies for ex vivo liver resection and autotransplantation. METHODS: We retrospectively summarized the clinical data of 114 patients diagnosed with hepatic AE who treated by ELRA in our department. A total of 114 patients were divided into three groups according to the different reconstruction methods of RHIVC: Group A with original RHIVC being repaired and reconstructed (n = 64), group B with RHIVC being replaced (n = 43), and group C with RHIVC being resected without reconstruction (n = 7). The clinical data of patients, including the operation time, anhepatic phase, intraoperative blood loss, complications and postoperative hospital stay, were analyzed and the patients were routinely followed up. The normally distributed continuous variables were expressed as means ± SD, whereas the abnormally distributed ones were expressed as median and analyzed by analysis of variance. Survival curve was plotted by the Kaplan-Meier method. RESULTS: All patients were routinely followed up for a median duration of 52 (range, 12-125) mo. The 30 d mortality rate was 7.0% (8/114) and 7 patients died within 90 d. Among all subjects, the inferior vena cava (IVC)-related complication rates were 17.5% (11/63) in group A and 16.3% (7/43) in group B. IVC stenosis was found in 12 patients (10.5%), whereas thrombus was formed in 6 patients (5.3%). Twenty-two patients had grade III or higher complications, with the complication rates being 17.2%, 16.3%, and 57.1% in the three groups. The average postoperative hospital stay in the three groups was 32.3 ± 19.8, 26.7 ± 18.2, and 51.3 ± 29.4 d (P = 0.03), respectively. CONCLUSION: ELRA can be considered a safe and feasible option for end-stage hepatic AE patients with RHIVC infiltration. The RHIVC reconstruction methods should be selected appropriately depending on the defect degree of AE lesions in IVC lumen. The RHIVC resection without any reconstruction method should be considered with caution.

Development of a duplex recombinase-aided amplification assay for direct detection of Mycoplasma pneumoniae and Chlamydia trachomatis in clinical samples.

BACKGROUND: Pneumonia caused by Mycoplasma pneumoniae is common in the elderly and children, and pneumonia caused by Chlamydia trachomatis is prevalent in newborns. This study aimed to establish a rapid, sensitive, and simple method for the direct detection of M. pneumoniae and C. trachomatis in clinical samples without DNA extraction. METHODS: We established a duplex recombinase-aided amplification (RAA) assay with the RNAseP gene as an internal control for detecting the P1 gene of M. pneumoniae and the ORF8 gene of C. trachomatis, respectively. The results were obtained at 39 °C within 15-20 min. A total of 130 clinical samples suspected of M. pneumoniae or C. trachomatis infection were collected and tested by duplex RAA and PCR. DNA extracted via a commercial kit or treated with a nucleic acid-releasing agent was used and compared, respectively. Standard recombinant plasmids were used to test the sensitivity of the duplex RAA assay. In addition, other similar common pathogens were used to verify the specificity of the duplex RAA assay. RESULTS: The sensitivity of the duplex RAA assay for detecting M. pneumoniae and C. trachomatis was 10 copies/µL using recombinant plasmids. Compared with PCR, the sensitivity and specificity of duplex RAA assays for M. pneumoniae and C. trachomatis was 100% using clinical DNA samples extracted using a commercial kit and a nucleic acid-releasing agent, and the Kappa value was 1. CONCLUSION: The advantages of this duplex RAA assay include high sensitivity and specificity, short duration, and simple extraction steps, with potential for use in the on-site detection of M. pneumoniae and C. trachomatis in resource-limited settings.

Detection of low-load Epstein-Barr virus in blood samples by enriched recombinase aided amplification assay.

Epstein-Barr virus (EBV), a common human γ-herpesvirus, infects more than 90% of adults worldwide. The purpose of this study was to establish a novel EBV detection method by combining the recombinase aided amplification (RAA) assay with an initial enrichment step that utilizes magnetic beads coated with a recombinant human mannan-binding lectin (rhMBL, M1 protein). An M1 protein-protein A magnetic bead complex (M1 beads) was prepared and used to achieve separation and enrichment of EBV from blood. After nucleic acid extraction, DNA was amplified by RAA. Using 388 whole blood samples and 1 serum sample, we explored the specificity, sensitivity and applicability of the newly developed detection method and compared it with commercial quantitative real-time polymerase chain reaction (qPCR) following M1 bead enrichment, traditional qPCR and traditional RAA. After enrichment, the positivity rate of EBV was increased from 15.94% to 17.74% by RAA (P < 0.05) and from 7.20% to 15.17% by qPCR (P < 0.05). The viral loads after enrichment were increased by 1.13 to 23.19-fold (P < 0.05). Our data demonstrates that an RAA assay incorporating M1 bead enrichment is a promising tool for detecting low EBV viral loads in blood samples that will facilitate an early response to EBV infection.

Development and evaluation of a sensitive recombinase aided amplification assay for rapid detection of Vibrio parahaemolyticus.

Vibrio parahaemolyticus (V. parahaemolyticus) is a widely distributed pathogen in the coastal areas, which causes food poisoning and leads to gastroenteritis and sepsis. Therefore, developing a simple, sensitive, and rapid detection method for V. parahaemolyticus is a major concern globally. This study established a sensitive and rapid technique based on recombinase aided amplification (RAA) to detect V. parahaemolyticus. The RAA reaction was carried out successfully at 39 °C within 30 min. The sensitivity of the RAA assay was 101 copies/µL using the recombinant plasmid and 10-3 ng/µL using the V. parahaemolyticus strain. In addition, RAA directly detected 7 × 103 CFU/mL of simulated fecal samples and 0.1 CFU/mL after enrichment for 4 h. The sensitivity and specificity of the RAA assay using fecal and fish samples were 100% similar to that of the real-time PCR. We conclude that the RAA assay is an ideal screening method for detecting V. parahaemolyticus due to its rapidity, high accuracy, and simplicity in operation.

Rapid Internal Control Reference Recombinase-Aided Amplification Assays for EBV and CMV Detection.

Epstein-Barr virus (EBV) and cytomegalovirus (CMV), two of the most prevalent human herpesviruses, cause a wide spectrum of diseases and symptoms and are associated with serious health problem. In this study, we developed an internal control reference recombinase-aided amplification (ICR-RAA) assay for the rapid detection of EBV and CMV within 30 min. The assay had a sensitivity of 5 and 1 copies/test for EBV and CMV, respectively, with no cross reaction with other pathogens. In comparison with those of the commercial quantitative polymerase chain reaction (qPCR), the sensitivity of the EBV and CMV ICR-RAAs using extracted DNA was 93.33% and 84.84%, respectively; the specificity was 98.75% and 100.00%, respectively; and the Kappa values were 0.930 and 0.892 ( P < 0.05), respectively. In comparison with those of qPCR, the sensitivity of the EBV and CMV ICR-RAAs using the DNA by thermal lysis was 72.22% and 80.00%, respectively; the specificity was 100.00%; and the Kappa values were 0.764 and 0.878 ( P < 0. 05), respectively. Thus, rapid and specific detection of EBV and CMV is possible using ICR-RAA assays.

A highly sensitive one-tube nested quantitative real-time PCR assay for specific detection of Bordetella pertussis using the LNA technique.

OBJECTIVES: Bordetella pertussis is a highly contagious respiratory agent and is the causative pathogen of pertussis, which primarily affects children. Current diagnostic techniques for this pathogen have a variety of limitations including a long culture time, low bacterial load, and lack of specificity. METHODS: This article reports the development of a one-tube nested quantitative real-time PCR assay using the locked nucleic acid (LNA) technique (LNA-OTN-q-PCR), targeting the BP485 gene and using a simple inexpensive extraction method. A total of 130 clinical samples from patients with clinically suspected pertussis, collected from the Children's Hospital of Hebei, China, were tested by LNA-OTN-q-PCR assay. RT-PCR and two-step semi-nested PCR assays were performed in parallel for comparison. RESULTS: Only strains of B. pertussis were identified as positive, whereas all of the remaining strains were appropriately identified as negative by the LNA-OTN-q-PCR assay. A single copy per reaction can be detected by the LNA-OTN-q-PCR assay. Additionally, the sensitivity of this method was 100 times that of the RT-PCR assay (100 copies per reaction). Sixty-three of the 130 clinical samples were detected positive by LNA-OTN-q-PCR assay; in contrast, RT-PCR was able to detect only 41 positive samples. Following this, all 63 samples were positively identified by two-step semi-nested PCR. Compared with the two-step semi-nested PCR assay, both the specificity and sensitivity of the LNA-OTN-q-PCR assay using purified DNA and crude extract were 100%. CONCLUSIONS: This assay was able to detect B. pertussis infection with high sensitivity and specificity. This test shows great potential as a promising technique to detect B. pertussis in both clinical laboratories and public health settings.

Termination of a partial hydatidiform mole and coexisting fetus: A case report.

BACKGROUND: We describe the treatment strategy for a patient who was found to have a partial hydatidiform mole and coexisting fetus (PHMCF) during the second trimester. The patient was a 38-year-old Chinese woman who had become pregnant following in vitro fertilization and embryo transplantation. We wanted to determine the safest therapeutic strategy to terminate the PHMCF during the second trimester. CASE SUMMARY: In this case, we present a patient who was found to have a PHMCF complicated with serious continuous vaginal bleeding and pre-eclampsia during the second trimester. After careful evaluation, the pregnancy was considered to be unsustainable and was terminated via caesarean section (CS). An infant with weak vital signs and a partially cystic placenta measuring 110 mm × 95 mm × 35 mm were delivered by CS. The patient was discharged after 4 d. The serum levels of ß-human chorionic gonadotropin decreased to within a normal range 5 wk after the operation, and no evidence of persistent trophoblastic disease or lung metastases was noticed at the 6-mo follow-up. CONCLUSION: CS termination of PHMCF during the second trimester may be a relatively safe therapeutic strategy.

A rapid and sensitive recombinase aided amplification assay incorporating competitive internal control to detect Bordetella pertussis using the DNA obtained by boiling.

OBJECTIVES: Pertussis is a highly transmissible acute respiratory infection caused by the bacterial pathogen Bordetella pertussis. The purpose of this study was to develop a rapid, simple and sensitive diagnostic test for detecting this pathogen. METHODS: Here we present a recombinase aided amplification (RAA) assay incorporating competitive internal amplification control (IAC) to detect Bordetella pertussis using the DNA obtained by boiling. This assay was performed in a single closed tube at 39°C within 30min. A total of 115 clinical samples suspected of pertussis were collected and tested by the internally controlled RAA assay using both extracted DNA with the commercial kit and the DNA obtained by boiling. For comparison, the real-time PCR (RT-PCR) was also performed with DNA extraction in parallel. RESULTS: The sensitivity of the internally controlled RAA assay was 101 copies or 10CFU/ml per reaction in detecting plasmid DNA or B. pertussis strain. The optimum concentration of the IAC plasmid was determined to be 100 copies, and the introduction of IAC effectively reduced the occurrence of false negatives. Compared to the RT-PCR, RAA results with DNA extraction obtained 100% sensitivity and specificity, and the RAA results with heat-treated DNA showed 85.96% sensitivity and 100% specificity. CONCLUSION: With the advantages of 45min turn-around time and simple steps of DNA purification, this assay could become a useful diagnostic tool for Bordetella pertussis detection and is potentially suitable for point-of-care identification to guide prompt clinical treatment.

Development of an Internally Controlled Reverse Transcription Recombinase-aided Amplification Assay for the Rapid and Visual Detection of West Nile Virus.

West Nile virus (WNV) causes West Nile fever and West Nile encephalitis. Because infection by WNV creates serious public health problems, its simple, rapid, and visual detection is very important in clinical practice, especially in resource-limited laboratories. We have developed a rapid, specific, and highly sensitive internally controlled reverse transcription recombinase-aided amplification (RTRAA) assay to detect WNV, using both real-time fluorescence and the lateral flow dipstick (LFD) at 39.0 °C for 30 min. The analytical sensitivity of the RT-RAA assay was 10 plasmid copies and 1.6 pfu per reaction with real-time fluorescence, and 1,000 plasmid copies per reaction with the LFD. No crossreaction with other control viruses was observed. Compared with the RT-qPCR assay, the RT-RAA assay demonstrated 100% sensitivity and 100% specificity for WNV.

Applicability of duplex real time and lateral flow strip reverse-transcription recombinase aided amplification assays for the detection of Enterovirus 71 and Coxsackievirus A16.

BACKGROUND: Enterovirus 71 (EV71) and coxsackievirus A16 (CA16) are the two main etiological agents of Hand, Foot and Mouth Disease (HFMD). Simple and rapid detection of EV71 and CA16 is critical in resource-limited settings. METHODS: Duplex real time reverse-transcription recombinase aided amplification (RT-RAA) assays incorporating competitive internal amplification controls (IAC) and visible RT-RAA assays combined with lateral flow strip (LFS) for detection of EV71 and CA16 were developed respectively. Duplex real time RT-RAA assays were performed at 42 °C within 30 min using a portable real-time fluorescence detector, while LFS RT-RAA assays were performed at 42 °C within 30 min in an incubator. Recombinant plasmids containing conserved VP1 genes were used to analyze the sensitivities of these two methods. A total of 445 clinical specimens from patients who were suspected of being infected with HFMD were used to evaluate the performance of the assays. RESULTS: The limit of detection (LoD) of the duplex real time RT-RAA for EV71 and CA16 was 47 copies and 38 copies per reaction, respectively. The LoD of the LFS RT-RAA for EV71 and CA16 were both 91 copies per reaction. There was no cross reactivity with other enteroviruses. Compared to reverse transcription-quantitative PCR (RT-qPCR), the clinical diagnostic sensitivities of the duplex real time RT-RAA assay were 92.3% for EV71 and 99.0% for CA16, and the clinical diagnostic specificities were 99.7 and 100%, respectively. The clinical diagnostic sensitivities of the LFS RT-RAA assay were 90.1% for EV71 and 94.9% for CA16, and the clinical diagnostic specificities were 99.7 and 100%, respectively. CONCLUSIONS: The developed duplex real time RT-RAA and LFS RT-RAA assays for detection of EV71 and CA16 are potentially suitable in primary clinical settings.

A multiplex one-tube nested real time RT-PCR assay for simultaneous detection of respiratory syncytial virus, human rhinovirus and human metapneumovirus.

BACKGROUND: Respiratory syncytial virus (RSV), human Rhinovirus (HRV) and human Metapneumo Virus (HMPV) are important viral pathogens causing acute respiratory tract infections in the hospitalized patients. Sensitive and accurate detection of RSV, HRV and HMPV is necessary for clinical diagnosis and treatment. RESULTS: A locked nucleic acid (LNA)-based multiplex closed one-tube nested real-time RT-PCR (mOTNRT-PCR) assay was developed for simultaneous detection of RSV, HRV and HMPV. The sensitivity, specificity, reproducibility and clinical performance of mOTNRT-PCR were evaluated and compared with individual real time PCR (RT-qPCR) assay using clinical samples. The analytical sensitivity of mOTNRT-PCR assay was 5 copies/reaction for RSV, HRV and HMPV, respectively, and no cross-reaction with other common respiratory viruses was observed. The coefficients of variation (CV) of intra-assay and inter-assay were between 0.51 to 3.67%. Of 398 nasopharyngeal aspirates samples tested, 109 (27.39%), 150 (37.69%) and 44 (11.06%) were positive for RSV, HRV and HMPV, respectively, whereas 95 (23.87%), 137 (34.42%) and 38 (9.55%) were positive for RSV, HRV and HMPV, respectively, by individual RT-qPCR assay. Thirty three samples that were positive by mOTNRT-PCR but negative by RT-qPCR were confirmed as true positives by sequencing using reported traditional two-step nested PCR assay. CONCLUSION: mOTNRT-PCR assay reveals extremely higher sensitivity than that of RT-qPCR assay for detecting RSV, HRV and HMPV in clinical settings.

Ex vivo liver resection and autotransplantation as alternative to allotransplantation for end-stage hepatic alveolar echinococcosis.

BACKGROUND & AIMS: Radical resection is the best treatment for patients with advanced hepatic alveolar echinococcosis (AE). Liver transplantation is considered for selected advanced cases; however, a shortage of organ donors and the risk of postoperative recurrence are major challenges. The aim of this study was to assess the clinical outcomes of ex vivo liver resection and autotransplantation for end-stage AE. METHODS: In this prospective study, 69 consecutive patients with end-stage hepatic AE were treated with ex vivo resection and liver autotransplantation between January 2010 and February 2017. The feasibility, safety and long-term clinical outcome of this technique were assessed. RESULTS: Ex vivo extended hepatectomy with autotransplantation was successful in all patients without intraoperative mortality. The median weight of the graft and AE lesion were 850 (370-1,600) g and 1,650 (375-5,000) g, respectively. The median duration of the operation and anhepatic phase were 15.9 (8-24) h and 360 (104-879) min, respectively. Six patients did not need any blood transfusion. Complications higher than IIIa according to Clavien classification were observed in 10 patients. The 30-day-mortality and overall mortality (>90 days) were 7.24% (5/69) and 11.5% (8/69), respectively. The mean hospital stay was 34.5 (12-128) days. Patients were followed-up systematically for a median of 22.5 months (14-89) without recurrence. CONCLUSION: This is the largest series assessing ex vivo liver resection and autotransplantation in end-stage hepatic AE. This technique could be an effective alternative to liver transplantation in patients with end-stage hepatic AE, with the advantage that it does not require an organ nor immunosuppressive agents. LAY SUMMARY: Ex vivo liver resection and autotransplantation were performed in a large series of patients with end-stage hepatic alveolar echinococcosis. The results showed that this surgical option was feasible, with acceptable postoperative mortality, but 100% disease-free survival in survivors. Careful patient selection, as well as precise assessment for size and quality of the remnant liver are key to successful surgery.

Improved experimental model of hepatic cystic hydatid disease resembling natural infection route with stable growing dynamics and immune reaction.

AIM: To investigate a safer way to set up the disease model of cystic echinococcosis without contamination risk and develop a novel experimental murine model of hepatic cystic echinococcosis. METHODS: C57B/6 mice were injected with human protoscolices of three different concentrations via the portal vein. The mice were followed for 10 mo by ultrasound, gross anatomy, and pathological and immunological examinations. The protoscolex migration in the portal vein, hydatid cyst growth, host immune reaction, and hepatic histopathology were examined periodically. RESULTS: The infection rates in the mice in the high, medium, and low concentration groups were 90%, 100%, and 63.6%, respectively. The protoscolices migrated in the portal vein with blood flow, settled in the liver, and developed into orthotopic hepatic hydatid cysts, resembling the natural infection route and course. CONCLUSION: We have established an improved experimental model of hepatic cystic echinococcosis with low biohazard risk but stable growing dynamics and immune reaction. It is especially useful for new anti-parasite medication trials against hydatid disease.

[Effects of Fulvic Acid on Absorption and Form Distribution of Heavy Metals on Sediments].

Based on the extracted fulvic acid (FA) from Lake Wuliangsuhai sediments by sequential alkali extraction, this work studied the effects of FA on the adsorption and fraction distribution of heavy metals (HM) on sediments using original sediments and sediments treated with 30% H2O2 as adsorbents. The results showed both organic matter and FA had effects on the HM adsorption onto sediments; The treatments of FA-free conditions and the sediments treated by H2O2 showed relatively strong influence on Cu²âº adsorption, which decreased the Cu²âº adsorption by 17.85%. With the increasing FA addition, the adsorption percentage of HM on both types of sediments showed gradually decreasing trends, with the order of Cu²âº >> Cd²âº > Zn²âº > Pb²âº; when the FA content was more than 5% , FA became the governing factor on the decreasing adsorption percentage of HM. With increasing FA addition, forms distribution of HM showed significant changes in both types of sediments; i. e. FA additions showed significant negative and positive correlations with percentages of metals bound to carbonates and organic matter, respectively, since the FA addition increased the H⁺ concentration of the system, in which H⁺ could activate the metals bound to carbonate from the sediments. As an organophilic weak element, the fraction percentage of Cd bound to organic matter was the lowest with the minimal changes.

[Ecological risk assessment of bisphenol A in Chinese freshwaters].

Bisphenol A (BPA) has many toxic effects on aquatic organisms, of which the most obvious effect is the estrogenic effect. The data collected in the study were divided into two parts, based on the response of the tested organisms to the estrogenic effects of BPA and their exposed time, and the risk of BPA to Chinese aquatic water was assessed by using quotient method, quotient exponent and probability method, safety threshold value method and joint probability risk assessment, respectively. Similar results were derived from the above four methods. Aquatic organisms were more sensitive to the estrogenic effects of BPA than other toxic effects. The results of risk assessment from safety threshold value method were more accurate and confident than the other three methods. Using the chronic data of BPA's estrogenic effect on tested organisms as the endpoint for risk assessment in safety threshold value method, it was found that in 64.70% of the Chinese freshwaters more than 5% of aquatic organisms were affected by the estrogenic toxicity of BPA, and the maximum allowable concentration of BPA was 15.72 ng x L(-1). Using the acute data of such effects as endpoint in safety threshold value method, in about 20.43% volume of the Chinese freshwaters more than 5% of aquatic organisms were affected by the estrogenic toxicity of BPA, and the maximum allowable concentration was 2.24 x 10(2) ng x L(-1).