Insight into the hetero-interactions of 4-nonylphenol with dissolved organic matter: multiple spectroscopic methods, 1H NMR study and principal component analysis.

Understanding the interactions between heterogeneous dissolved organic matter (DOM) and nonylphenols (NPs) is essential for predicting their behavior and fate in the environment. Herein, we firstly obtained different MW-fractionated humic acids (HAs) using the ultrafiltration method. Afterward, the molecular weight (MW)-dependent interactions of HAs with 4-nonylphenol (4-NP) were analysed by excitation emission matrix (EEM) fluorescence spectroscopy, fluorescence quenching, UV-vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and principal component analysis (PCA). EEM spectra indicated that the quenching mechanism was static. In the binding process, the higher MW fractions showed stronger interaction with 4-NP than the lower MW counterparts, exhibiting a clear MW-dependent interaction heterogeneity. The interaction constants for the 4-NP-HAs system were suppressed as the ionic strength decreased and pH increased, which was especially obvious in the binding of 4-NP to the lower MW-fractionated HAs. The FTIR spectra revealed that hydroxyl and aromatics were involved in the interaction process of HA fractions with 4-NP. It was also found from 1H NMR that π-π interactions between aromatic rings of 4-NP and MW-fractionated HAs were responsible for the complexation. The correlation analysis and PCA results indicated that aromaticity and MW play important roles in the interaction process and confirmed an obvious interaction heterogeneity among MW-fractionated HAs samples. This work highlighted MW-dependent interaction heterogeneities of HA, which suggested that heterogeneity in MW distribution should be taken into consideration when exploring the fate and biogeochemistry cycling of 4-NP from contaminated environments.

Effects of humic acid on Pb2+ adsorption onto polystyrene microplastics from spectroscopic analysis and site energy distribution analysis.

Microplastics (MPs), act as vectors of heavy metal pollutants in the environment, is of practical significance to study the adsorption process and mechanism on heavy metals. In this study, polystyrene microplastics (PSMPs) were used as model MPs to study the adsorption of Pb2+ on PSMPs and the effects of humic acid (HA) on the adsorption process. The results showed that HA promoted the adsorption of Pb2+ on PSMPs, and the higher the concentration of HA, the greater the adsorption of Pb2+. With the increase of pH value and decrease of ionic strength, the adsorption capacity of PSMPs for Pb2+ increased. The scanning electron microscope equipped with the energy dispersive spectroscope (SEM-EDS), fourier transform-infrared spectra (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis showed that Pb2+ could be adsorbed directly onto PSMPs and also indirectly by HA. The higher KSV values in the PSMPs-HA-Pb2+ system than PSMPs-HA system by fluorescence analysis of HA suggested that HA acted as a bridging role in the adsorption of Pb2+ on PSMPs. The site energy distribution analysis further revealed that HA increased the average site energy µ(E*) and its standard deviation σe* of PSMPs by introducing more adsorption sites, thus enhanced the adsorption affinity of PSMPs. This study provided more thoughts and insights into the adsorption behavior and mechanism of MPs for Pb2+ in aquatic environments.

Multiple pollutants stress the coastal ecosystem with climate and anthropogenic drivers.

Coastal ecosystem health is of vital importance to human well-being. Field investigations of major pollutants along the whole coast of China were carried out to explore associations between coastal development activities and pollutant inputs. Measurements of target pollutants such as PFAAs and PAHs uncovered notable levels in small estuary rivers. The Yangtze River was identified to deliver the highest loads of these pollutants to the seas as a divide for the spatial distribution of pollutant compositions. Soil concentrations of the volatile and semi-volatile pollutants showed a cold-trapping effect in pace with increasing latitudinal gradient. The coastal ecosystem is facing high ecological risks from metal pollution, especially copper (Cu) and zinc (Zn), while priority pollutants of high risks vary for different kinds of protected species, and the ecological risks were influenced by both climate and physicochemical properties of environmental matrices, which should be emphasized to protect and restore coastal ecosystem functioning.

Cobalt doped nitrogenous porous carbon derived from covalent organic framework as cataluminescence catalyst for rapid determination of n-hexane in edible oil.

In this work, a catalytic material of cobalt doped nitrogenous porous carbon (Co/NPC) was fabricated from covalent organic frameworks (COFs) and cobalt ion via directly carbonization. Attribute to the excellent selective catalytic performance towards n-hexane, Co/NPC was employed in cataluminescence (CTL) for rapid and sensitive determination of n-hexane. Moreover, the detection conditions of CTL were evaluated, including temperature, flow rate and detecting wavelength. Under optimized conditions, a good linear relation between signal intensity of CTL and n-hexane concentration was obtained in the linear range of 0.4-250.0 mg/L and the limit of detection (LOD, S/N = 3) was 0.13 mg/L. Furthermore, the Co/NPC based CTL sensor was successfully applied to the determination of n-hexane in edible oil samples with the recoveries in the range of 92.0%-104.0%. The method comparison results of GC/MS and CTL on real sample analysis further proved the accuracy of the developed Co/NPC based CTL method. Additionally, the possible catalytic mechanism of n-hexane on the surface of Co/NPC was investigated, assisting by GC/MS on intermediation products identification. Overall, the Co/NPC based CTL sensor has been confirmed excellent performance in the n-hexane determination, which revealing extensive application in rapid residual n-hexane analysis in edible oil.

Bioaccumulation and human exposure of perfluoroalkyl acids (PFAAs) in vegetables from the largest vegetable production base of China.

This study investigated perfluoroalkyl acids (PFAAs) in edible parts of vegetables, soils, and irrigation water in greenhouse and open filed, for the first time, in Shouguang city, the largest vegetable production base in China, which is located nearby a fluorochemical industrial park (FIP). The bioaccumulation factors (BAFs) were calculated, and the human exposures of PFAAs via consumption of the vegetables for different age groups assuming the maximum levels detected in each vegetable and average consumption rates were also estimated. The ΣPFAA levels ranged from 1.67 to 33.5 ng/g dry weight (dw) in the edible parts of all the vegetables, with perfluorobutanoic acid (PFBA) being the dominant compound with an average contribution of 49% to the ΣPFAA level. The leafy vegetables showed higher ΣPFAA levels (average 8.76 ng/g dw) than the fruit and root vegetables. For all the vegetables, the log10 BAF values of perfluorinated carboxylic acids showed a decreasing trend with increasing chain length, with PFBA having the highest log10 BAF values (average 0.98). Cabbage had higher bioaccumulation of PFBA (log10 BAF 1.24) than other vegetables. For the greenhouse soils and vegetables, the average contribution of perfluorooctanoic acid (PFOA) to ΣPFAA was lower than that in the open field samples, while the contributions of PFBA, PFHxA, PFPeA to ΣPFAA were higher. Irrigation water may be an important source of PFAAs in greenhouse, while for open field vegetables and soils, atmospheric deposition may be an additional contamination pathway. The estimated maximum exposure to PFOA through vegetable consumption for urban preschool children (aged 2-5 years) was 63% of the reference dose set by the European Food Safety Authority. Suggestions are also provided for mitigating the health risks of human exposure to PFAAs.

Assessing the contribution of atmospheric transport and tourism activities to the occurrence of perfluoroalkyl acids (PFAAs) in an Alpine Nature Reserve.

Perfluoroalkyl acids (PFAAs) are ubiquitous in the global environment, even in remote regions. With increasing production and application of PFAAs in China, their distribution patterns have been widely reported, however with less attention to inland northwestern regions. Long-range transport and direct releases from local activities have been regarded as the main reasons for PFAAs distribution in such a remote area. To identify and quantify the contributions of different sources to PFAAs occurrences, an investigation was conducted in the Tianchi lake, nature reserve. A total of 20 water samples, 8 soil, 4 sediment and 10 fresh snow samples were collected and analyzed in 2015. The mean PFAAs concentrations were 3.38 ng L-1 in surface water, 1.06 ng g-1 dw in soil, 0.53 ng g-1 dw in sediment, and 3.31 ng L-1 in fresh snow, respectively. High levels of PFAAs were observed in surface water (15.41 ng L-1) from Western Tianchi pond and surface snow (14.24 ng L-1) from the site near a ski resort around Tianchi Lake indicating potential pollution by local human activities. The correlation between individual concentrations among water, soil and snow indicated the snow deposition as an important source. Although with limited sample size, principal component analysis associated with multiple linear regression (PCA-MLR) and positive matrix factorization (PMF) analyses have identified two major sources, which are characterized as tourism activities with dominance of perfluorooctanoic acid (PFOA) and long-range transport with abundant perfluorobutanoic acid (PFBA). Their contributions to total levels were 41% and 52%, respectively. These two sources contributed differently to the PFAAs presences in Tianchi and Western Tianchi Lakes. Source analysis indicates that the western Tianchi lake with a relatively small catchment was affected mainly by local activities.

Removal of perfluoalkyl acids (PFAAs) through fluorochemical industrial and domestic wastewater treatment plants and bioaccumulation in aquatic plants in river and artificial wetland.

The fluorochemical industry has shifted to the production of short chain homologues of perfluoalkyl acids (PFAAs) in recent years. Yet the effective removal of short-chain PFAAs from wastewater is still a major challenge. In this study, the removal efficiencies (RM) of short- and long-chain PFAAs emitted from two fluorochemical industrial parks were evaluated in one industrial and two domestic waste water treatment plants (WWTPs), and bioaccumulation factors (BAF) of PFAAs in various emerged and submerged aquatic plants in adjacent river and an artificial wetland were also calculated. Perfluorobutanoic acid (PFBA), perfluorobutane sulfonic acid (PFBS) and perfluorooctanoic acid (PFOA) were dominant in the whole area. The source water of the fluorochemical industrial WWTP (F-WWTP) gathered from the facilities in Park 2 contained total PFAAs (∑PFAAs) of 5,784 ng/L. Among the four main technologies, the biological aerated filter, combined with upflow sludge bed processes presented the greatest RM of ∑PFAAs in the F-WWTP, respectively. The source water of the wetland from the river brought ∑PFAAs to 21,579 ng/L, emerged plants showed higher BAF of PFBA and PFBS, while lower BAF of PFOA and PFOS than submerged plants. J. serotinus showed both the highest ∑PFAAs and the highest BAF for short chain PFAAs. With the increasing production capacity, this study provided valuable information for risk assessment and management of PFAA emission from point sources.

Multiple crop bioaccumulation and human exposure of perfluoroalkyl substances around a mega fluorochemical industrial park, China: Implication for planting optimization and food safety.

Perfluoroalkyl substances (PFASs) have become a recognized concern due to their mobility, persistence, ubiquity and health hazards in the environment. In this study, ten types of vegetables and three types of grain crops were collected in two open-air fields with different distances (0.3 km, 10 km) from a mega fluorochemical industrial park (FIP), China. Bioaccumulation characteristics of PFASs in light of crop types and organs were explored, followed by analyzing human exposure and risks to local residents with different age groups and dietary habits. Elevated levels of ∑PFASs were found nearby the FIP ranging from 79.9 ng/g to 200 ng/g in soils and from 58.8 ng/g to 8085 ng/g in crops. Perfluorooctanoic acid (PFOA) was the predominant PFAS component in soil; while shorter-chain perfluoroalkyl carboxylic acids (PFCAs), especially perfluorobutanoic acid (PFBA), were the major PFAS contaminants in multiple crops, resulting from their bioaccumulation preference. Depending on the crop types, the bioaccumulation factors (BAFs) of ∑PFASs for edible parts varied from 0.36 to 48.0, and the highest values were found in shoot vegetables compared with those in fruit vegetables, flower vegetables, root vegetables and grain crops. For typical grains, the BAFs of ∑PFASs decreased in the order of soybean (Glycine max (Linn.) Merr.), wheat (Triticum aestivum L.) and corn (Zea mays L.), possibly related to their protein and lipid content. Among specific organs in the whole plants, leaves exhibited the highest BAFs of ∑PFASs compared with corresponding roots, stems, husks or grains. With increasing carbon chain lengths of individual PFCAs (C4-C8), the logarithm of their BAFs for edible parts of various crops showed a linear decrease (0.1-1.16 log decrease per CF2 unit), and the largest decrease was observed in grains. Human exposure to PFOA via the consumption of contaminated crops represents a health risk for local residents, especially for low-age consumers or urban consumers with higher vegetable diet. Implications for planting optimization and food safety were provided aiming to reduce health hazards of PFASs.

Carbon dot-decorated porous organic cage as fluorescent sensor for rapid discrimination of nitrophenol isomers and chiral alcohols.

Isomers discrimination plays a vital role in modern chemistry, and development of efficient and rapid method to achieve this aim has attracted a great deal of interest. In this work, a novel carbon dot-decorated chiral porous organic cage hybrid nanocomposite (CD@RCC3) was prepared and used to fabricate fluorescent sensor. The resultant CD@RCC3 was characterized by using a range of techniques, finding that CD@RCC3 possesses strong and stable fluorescent property in common organic solvents, especially it exhibits chiral property. The potential application of CD@RCC3 in fluorescence sensing was demonstrated by isomers discrimination. The designed sensor was successfully used to rapid discriminate nitrophenol isomers. Meanwhile, it exhibited differentiation ability towards phenylalaninol and phenylethanol enantiomers. Our work enriches the type of synthetic materials for fluorescence sensing, and provides a simple method for distinguishing structural isomers and chiral isomers.

Climate change induced eutrophication of cold-water lake in an ecologically fragile nature reserve.

Aquatic ecosystem sustainability around the globe is facing crucial challenges because of increasing anthropogenic and natural disturbances. In this study, the Tianchi Lake, a typical cold-water lake and a UNESCO/MAB (Man and Biosphere) nature reserve located in high latitude and elevation with the relatively low intensity of human activity was chosen as a system to examine the linkages between climate change and eutrophication. As a part of the UNESCO Bogda Man and Biosphere Reserve, Tianchi Lake has been well preserved for prevention from human intervention, but why has it been infected with eutrophication recent years? Our results show that climate change played a significant role in the eutrophication in the Tianchi Lake. Increased temperature, changed precipitation pattern and wind-induced hydrodynamic fluctuations in the summer season were suggested to make a major contribution to the accelerated eutrophication. The results also showed that the local temperature and precipitation changes were closely linked to the large-scale atmospheric circulation, which opens the door for the method to be applied in other regions without local climatic information. This study suggests that there is an urgent need to take into consideration of climate change adaptation into the conservation and management of cold-water lakes globally.

Polarization properties of reflected light with natural light incidence and elimination of angle of incidence ambiguity.

Polarization imaging technology provides information about not only the irradiance of a target but also the degree of polarization and angle of polarization, which indicate extensive application potential in the field of ocean remote sensing. Natural light can be converted into partially polarized light by the reflection from an interface, and the Fresnel equations can describe the quantitative relationship between the angle of incidence and the degree of polarization of the reflected light. However, the relationship between the angle of polarization and angle of incidence has rarely been studied. In this study, we investigate the polarization state model of reflected light and establish the relationship between the angle of polarization and angle of incidence. This is verified using polarization imaging experiments on a glass plate and calm water surface. The results indicate that the theoretical model agrees well with the experimental results. A method to eliminate the ambiguity of the angle of incidence is proposed based on the model, and its effectiveness and feasibility are verified. It lays the theoretical foundation for imaging detection based on the polarization imaging of transparent media surfaces and sea surface ripples.

Multimedia fate and transport simulation of perfluorooctanoic acid/ perfluorooctanoate in an urbanizing area.

Strong global demand leads to significant production of fluoropolymers (FP) in China which potentially release large quantities of perfluorooctanoic acid/perfluorooctanoate (collectively called PFOA/PFO) to the environment. Modelling the fate and transport of PFOA/PFO provides an important input for human health risk assessment. Considering the effects of urbanization and existing forms of PFOA/PFO, this study used the modified multispecies Berkeley-Trent-Urban-Rural model to simulate the transfer behavior of PFOA/PFO in the Bohai Rim, China. Spatial distributions of PFOA/PFO emissions during the year 2012 for the study area were illustrated. About two thirds of the total amount of PFOA/PFO was estimated to be released into fresh water, and the total releases to rural areas were 160-fold higher than those to urban areas due to the location of fluorochemical industrial parks. The simulations predicted that hydrosphere was the fate of PFOA/PFO, followed by soil and vegetation, which was consistent with field data. The highest PFOA/PFO concentration was modeled in the Xiaoqing River basin with a value of 32.57 µg/L. The PFOA/PFO concentrations in urban soils were generally higher than those in rural soils except for grids 1, 3 and 46. In addition, it was estimated that the total flux of PFOA/PFO entering into the Bohai Sea was 24.57 ton/year, 100-fold higher than that of perfluorooctane sulfonates (PFOS).

Major threats of pollution and climate change to global coastal ecosystems and enhanced management for sustainability.

Coastal zone is of great importance in the provision of various valuable ecosystem services. However, it is also sensitive and vulnerable to environmental changes due to high human populations and interactions between the land and ocean. Major threats of pollution from over enrichment of nutrients, increasing metals and persistent organic pollutants (POPs), and climate change have led to severe ecological degradation in the coastal zone, while few studies have focused on the combined impacts of pollution and climate change on the coastal ecosystems at the global level. A global overview of nutrients, metals, POPs, and major environmental changes due to climate change and their impacts on coastal ecosystems was carried out in this study. Coasts of the Eastern Atlantic and Western Pacific were hotspots of concentrations of several pollutants, and mostly affected by warming climate. These hotspots shared the same features of large populations, heavy industry and (semi-) closed sea. Estimation of coastal ocean capital, integrated management of land-ocean interaction in the coastal zone, enhancement of integrated global observation system, and coastal ecosystem-based management can play effective roles in promoting sustainable management of coastal marine ecosystems. Enhanced management from the perspective of mitigating pollution and climate change was proposed.

Transparent surface orientation from polarization imaging using vector operation.

The existing methods for shape measurement using polarization of transparent objects are based on two assumptions: (1) the paraxial assumption, assuming that the reflected ray is parallel to the optical axis of the imaging system; and (2) the s-component approximation assumption, which assumes that the s-component of the reflected light is predominant and the p-component is neglected. To overcome limitations posed by these two assumptions, this paper proposes a method based on the polarization characteristics of reflection from a transparent surface and vector operation. To overcome the paraxial assumption, the normal vector of the transparent surface is deduced by vector operation, analyzing the relationships between the direction vector of reflection, the normal vector of the reflection plane, the intersection line of the reflection plane and imaging plane, and the normal vector of the transparent surface. To overcome the limitations of the s-component approximation assumption, the angle between the s-component and the polarization direction of the reflected light is analyzed, which yields improved measurement precision. An experiment was performed with transparent targets (flat glass positioned at different angles), and the results show that the measurement error with this method is significantly less than those of existing methods. Thus, we believe this method overcomes the abovementioned limitations while also improving measurement precision.

Theory and analysis of a large field polarization imaging system with obliquely incident light.

Polarization imaging technology provides information about not only the irradiance of a target but also the polarization degree and angle of polarization, which indicates extensive application potential. However, polarization imaging theory is based on paraxial optics. When a beam of obliquely incident light passes an analyser, the direction of light propagation is not perpendicular to the surface of the analyser and the applicability of the traditional paraxial optical polarization imaging theory is challenged. This paper investigates a theoretical model of a polarization imaging system with obliquely incident light and establishes a polarization imaging transmission model with a large field of obliquely incident light. In an imaging experiment with an integrating sphere light source and rotatable polarizer, the polarization imaging transmission model is verified and analysed for two cases of natural light and linearly polarized light incidence. Although the results indicate that the theoretical model is consistent with the experimental results, the theoretical model distinctly differs from the traditional paraxial approximation model. The results prove the accuracy and necessity of the theoretical model and the theoretical guiding significance for theoretical and systematic research of large field polarization imaging.

Dynamic multimedia fate simulation of Perfluorooctane Sulfonate (PFOS) from 1981 to 2050 in the urbanizing Bohai Rim of China.

Perfluorooctane sulfonate (PFOS) and related substances are widely used in various industrial and commercial applications in China that ultimately discharge sufficient quantities of PFOS to the environment. It remains unclear how emissions of PFOS ultimately affect its concentrations as well as its fate in the environment. In this study, an improved Berkeley-Trent (BETR) multimedia model is developed to predict the PFOS levels with spatial and temporal distributions on unsteady state mode from 1981 to 2050, by taking the Bohai Rim of China as a case. The results showed that the modeled concentrations agreed well with the measured data. According to the model, PFOS concentrations in fresh water peaked in some months after the peak emission (2008 or 2009), whereas in urban soil the concentrations increased to peak slightly later (around 2014). Among the selected regions, Beijing and Tianjin were simulated with higher PFOS levels in the past and present because of their higher urbanization and industrialization since the 1980s, while in the future, Shandong and Liaoning are expected to have higher concentrations of PFOS than those in Beijing. The water system including coastal water, fresh water and sediment was the biggest sink for PFOS for coastal regions. Among the chemical inputs, direct primary emissions played a more important role, whereas for chemical removal processes, inter-regional advection and background outflow were the predominant pathways. The results would be useful to control the PFOS releases in China and will help the management agencies to implement the "Stockholm Convention" effectively.

Response of the phytoplankton community to water quality in a local alpine glacial lake of Xinjiang Tianchi, China: potential drivers and management implications.

Eutrophication has become one of the most serious threats to aquatic ecosystems in the world. With the combined drivers of climate change and human activities, eutrophication has expanded from warm shallow lakes to cold-water lakes in relatively high latitude regions and has raised greater concerns over lake aquatic ecosystem health. A two-year field study was carried out to investigate water quality, phytoplankton characteristics and eutrophication status in a typical alpine glacial lake of Tianchi, a scenic area and an important drinking water source in the Xinjiang Autonomous Region of China, in 2014 and 2015. Clear seasonal and annual variations of nutrients and organic pollutants were found especially during rainy seasons. For the phytoplankton community, Bacillariophyta held the dominant position in terms of both species and biomass throughout the year, suggesting the dominant characteristics of diatoms in the phytoplankton structure in such a high-altitude cold-water lake. This was quite different from plain and warm lakes troubled with cyanobacterial blooming. Moreover, the dominant abundance of Cyclotella sp. in Tianchi might suggest regional warming caused by climate change, which might have profound effects on the local ecosystems and hydrological cycle. Based on water quality parameters, a comprehensive trophic level index TLI (Σ) was calculated to estimate the current status of eutrophication, and the results inferred emerging eutrophication in Tianchi. Results from Canonical Correspondence Analysis (CCA) and correlation analysis of phytoplankton genera and physico-chemical variables of water indicated that abiotic factors significantly influenced the phytoplankton community and its succession in Tianchi Lake. These abiotic factors could explain 77.82% of the total variance, and ammonium was identified as the most discriminant variable, which could explain 41% of the total variance followed by TP (29%). An estimation of annual nutrient loadings to Tianchi was made, and the results indicated that about 212.97 t of total nitrogen and 32.14 t of total phosphorus were transported into Tianchi Lake annually. Human socio-economic activities (runoff caused by historical overgrazing and increasing tourism) were identified as the most important contributors to Tianchi nutrient loadings.

Crop bioaccumulation and human exposure of perfluoroalkyl acids through multi-media transport from a mega fluorochemical industrial park, China.

Significant quantities of perfluoroalkyl acids (PFAAs) are released to the environment from fluorochemical manufacturing processes through wastewater discharge and air emission in China, which may lead to human exposure and health risks through crop bioaccumulation from PFAAs-contaminated soil and irrigation water. This paper systematically studied the distribution and transport of PFAAs in agricultural soil, irrigation water and precipitation, followed by crop bioaccumulation and finally human exposure of PFAAs within a 10km radius around a mega-fluorochemical industrial park (FIP). Hotspots of contamination by PFAAs were found near the FIP and downstream of the effluent discharge point with the maximum concentrations of 641ng/g in agricultural soil, 480ng/g in wheat grain, 58.8ng/g in maize grain and 4,862ng/L in precipitation. As the distance increased from the FIP, PFAAs concentrations in all media showed a sharp initial decrease followed by a moderate decline. Elevated PFAA concentrations in soil and grains were still present within a radius of 10 km of the FIP. The soil contamination was associated with the presence of PFAAs in irrigation water and precipitation, and perfluorooctanoic acid (PFOA) was the dominant PFAA component in soil. However, due to bioaccumulation preference, short-chain perfluoroalkyl carboxylic acids (PFCAs), especially perfluorobutanoic acid (PFBA), became the major PFAA contaminants in grains of wheat and maize. The bioaccumulation factors (BAFs) for both grains showed a decrease with increasing chain length of PFAAs (approximately 0.5 log decrease per CF2 group). Compared to maize grain, wheat grain showed higher BAFs, possibly related to its higher protein content. The PFCA (C4-C8) concentrations (on a log10 basis) in agricultural soil and grain were found to show a linear positive correlation. Local human exposure of PFOA via the consumption of contaminated grains represents a health risk for local residents, especially for toddlers and children.

BEAN 2.0: an integrated web resource for the identification and functional analysis of type III secreted effectors.

Gram-negative pathogenic bacteria inject type III secreted effectors (T3SEs) into host cells to sabotage their immune signaling networks. Because T3SEs constitute a meeting-point of pathogen virulence and host defense, they are of keen interest to host-pathogen interaction research community. To accelerate the identification and functional understanding of T3SEs, we present BEAN 2.0 as an integrated web resource to predict, analyse and store T3SEs. BEAN 2.0 includes three major components. First, it provides an accurate T3SE predictor based on a hybrid approach. Using independent testing data, we show that BEAN 2.0 achieves a sensitivity of 86.05% and a specificity of 100%. Second, it integrates a set of online sequence analysis tools. Users can further perform functional analysis of putative T3SEs in a seamless way, such as subcellular location prediction, functional domain scan and disorder region annotation. Third, it compiles a database covering 1215 experimentally verified T3SEs and constructs two T3SE-related networks that can be used to explore the relationships among T3SEs. Taken together, by presenting a one-stop T3SE bioinformatics resource, we hope BEAN 2.0 can promote comprehensive understanding of the function and evolution of T3SEs.

Computational Identification of Protein Pupylation Sites by Using Profile-Based Composition of k-Spaced Amino Acid Pairs.

Prokaryotic proteins are regulated by pupylation, a type of post-translational modification that contributes to cellular function in bacterial organisms. In pupylation process, the prokaryotic ubiquitin-like protein (Pup) tagging is functionally analogous to ubiquitination in order to tag target proteins for proteasomal degradation. To date, several experimental methods have been developed to identify pupylated proteins and their pupylation sites, but these experimental methods are generally laborious and costly. Therefore, computational methods that can accurately predict potential pupylation sites based on protein sequence information are highly desirable. In this paper, a novel predictor termed as pbPUP has been developed for accurate prediction of pupylation sites. In particular, a sophisticated sequence encoding scheme [i.e. the profile-based composition of k-spaced amino acid pairs (pbCKSAAP)] is used to represent the sequence patterns and evolutionary information of the sequence fragments surrounding pupylation sites. Then, a Support Vector Machine (SVM) classifier is trained using the pbCKSAAP encoding scheme. The final pbPUP predictor achieves an AUC value of 0.849 in 10-fold cross-validation tests and outperforms other existing predictors on a comprehensive independent test dataset. The proposed method is anticipated to be a helpful computational resource for the prediction of pupylation sites. The web server and curated datasets in this study are freely available at http://protein.cau.edu.cn/pbPUP/.