Study on uranium ion adsorption property of porous glass modified with amidoxime group.

In this paper, we prepared three types of porous glasses (PGs) with specific surface areas of 311.60 m2/g, 277.60 m2/g, and 231.38 m2/g, respectively, via borosilicate glass phase separation. These glasses were further modified with amidoxime groups (AO) using the hydroxylamine method, yielding adsorbents named 1.5-PG-AO, 2-PG-AO, and 3-PG-AO. The adsorption performance of these adsorbents under various conditions was investigated, including sorption kinetics and adsorption mechanisms. The results reveal that the number of micropores and specific surface area of PG are significantly reduced after AO modification. All three adsorbents exhibit similar adsorption capabilities. Particularly, pH has a pronounced effect on U (VI) adsorption of PG-AO, with a maximum value at pH = 4.5. Equilibrium adsorption is achieved within 2 h, with a maximum adsorption capacity of 129 mg/g. Notably, a uranium removal rate of 99.94% is attained. Furthermore, the adsorbents show high selectivity in uranium solutions containing Na+ or K+. Moreover, the adsorbents demonstrate exceptional regeneration ability, with the removal rate remaining above 80% even after undergoing five adsorption-desorption cycles. The adsorption reaction of uranium on PG-AO involves a combination of multiple processes, with monolayer chemisorption being the dominant mechanism. Both the complex adsorption of AO and the ion exchange and physical adsorption of PG contribute to the adsorption of uranyl ions on the PG-AO adsorbents.

Modification of trophic level index with the contribution of macrophyte and its usage to classify trophic state of shallow lakes.

Trophic state index (TSI) only considers the influence of phytoplankton excluding that of macrophytes. It is necessary to combine the contribution of macrophytes into trophic classification systems in waters with extensive growths of macrophytes. A novel trophic level index (TLIECa) combined both trophic level index (TLI) and the TSI based on equivalent chlorophyll a (TSIECa) with the Chl a of submerged macrophytes as an addition in Chl a was developed to assess the spatial trophic state of 15 lakes and annual trophic state of four lakes in China. TLIECa obtained different but significantly correlated results as those of the traditional TLI, concerning the influences of both phytoplankton and macrophytes. The result of TLIECa indicated that the trophic state of the 15 lakes varied from mild-eutrophic to moderate-eutrophic. Small particles were the dominant factor for the trophic state of most sampling sites in the 15 lakes. Total phosphorus was the dominant factor for the trophic state for most time of the year in Lake Jinniu. Both small particles and total phosphorus were the dominant factors for the annual trophic state of Lake Taihu, Lake Xuanwu, and Lake Baijia.

Ecological regime shifts enhanced the contribution of microplastics to the burial of polycyclic aromatic hydrocarbons by sediments.

Ecological regime shifts and contamination of polycyclic aromatic hydrocarbons (PAHs), and microplastics (MPs) were found in many waters. How ecological regime shifts influence the contribution of microplastics to the burial of PAHs in sediments is unclear. Sediment cores in the largest lagoon (Lagoon Pinqing) of China were used to address this issue. Regime shifted from phytoplankton dominance to macrophyte dominance in the late 1970s in Lagoon Pinqing. The factor affecting the contribution of microplastics to the burial of PAHs in sediments varied from total phosphorus to total nitrogen during the periods from 1965 to 1970s, and from 1970s to 1990s. Phytoplankton dominated from the late 1990s to 2017. The increased aromaticity of sediment organic matter induced by regime shifts enhanced this contribution in this period. This contribution varied from 0 to 67.2%, influenced by the regime shifts in different periods. This contribution for the PAHs with moderate hydrophobicity was more susceptible to regime shifts than other PAHs. Our results suggested the contribution of microplastics to the burial of PAHs by sediments could be influenced by ecological regime shifts, and driven by various factors.

The roles of membrane permeability and efflux pumps in the toxicity of bisphenol S analogues (2,4-bisphenol S and bis-(3-allyl-4-hydroxyphenyl) sulfone) to Escherichia coli K12.

Bisphenol S (BPS) analogues are a group of recently reported emerging contaminants in the environment. Bacteria are important components of food webs. However, the potential risks of BPS analogues in bacteria have not been fully addressed. The toxicity effects and related mechanisms of two BPS analogues with different molecular weights (2,4-bisphenol S (2,4-BPS) and bis-(3-allyl-4-hydroxyphenyl) sulfone (TGSA)) on Escherichia coli K12 were compared. The minimum inhibitory concentration (MIC) of 2,4-BPS in the wild-type of E. coli K12 was lower than that of TGSA. The membrane permeability of the wild-type increased significantly after exposed to the same concentrations (0.5-50 nmol L-1) of 2,4-BPS and TGSA. In addition, 2,4-BPS induced more significant changes in membrane permeability than TGSA. Hormetic effects of 2,4-BPS and TGSA in the wild-type strain were noted in the levels of outer membrane proteins (ompC and ompF), multidrug efflux pump acriflavine resistance B (acrB) and type II topoisomerases. Transcriptomic results indicated these two BPS analogues inhibited the function of ABC transporters. In contrast to TGSA, 2,4-BPS affected DNA replication, tricarboxylic acid cycle, oxidative phosphorylation, and inhibited energy metabolism. Compared with wild-type strain, the ΔacrB mutant strain showed enhanced susceptibility to 2,4-BPS and TGSA with their MICs reduced by 20% and 11%, respectively. Deletion of the acrB affected the growth characteristics and induced stronger oxidative stress than the wild-type strain when exposed to 2,4-BPS or TGSA. The results suggested that 2,4-BPS were more toxic to E. coli K12 than TGSA in the concentration range of 0.5-50 nmol L-1, which was supported by the evidence from their impacts on membrane permeability and efflux pumps.

Spatial-temporal occurrence and sources of organochlorine pesticides in the sediments of the largest deep lake (Lake Fuxian) in China.

Compared with shallow lakes, less attention has been paid on pollutions in deep lakes. Lake Fuxian is the largest deep lake and an important water resource in China. The knowledge on organochlorine pesticides (OCPs) in sediments of Lake Fuxian was rare. Fifteen surface sediments and one sediment core were collected from Lake Fuxian. Sediment chronology was dated with the activities of 137Cs and 210Pb. Twenty-one OCPs in the surface sediments and sediment core were analyzed by a GC-MS. Spatial and temporal occurrences of OCPs in the sediments of this lake were studied. Correlations, isomer ratios, and principal component analysis (PCA) were applied to apportion the sources of OCPs in the sediments of this lake. The OCPs in the sediments of Lake Fuxian were dominated by p,p'-DDT (4,4'-dichlorodiphenyltrichloroethane) and HCHs (hexachlorocyclohexane). The concentration of ΣOCPs in the surface sediments ranged from 0.42 to 67.5 ng g-1, with an average of 42.3 ± 23.5 ng g-1 (mean ± SD, n = 15). The concentration of ΣOCPs in the sediment core varied from 3.5 to 707.9 ng g-1 in the period from 1950 to 2010, with an average of 167.7 ± 203.7 ng g-1 (n = 24). The highest concentrations and fluxes of α-HCH, γ-HCH, and p,p'-DDT were found in the years of 1964 and 1967, respectively. The fluxes of HCH isomers in the sediment core decreased in the orders as γ-HCH > ß-HCH > α-HCH in the period from 1950 to 2010. The concentrations of HCHs and p,p'-DDT in the sediments of Lake Fuxian were higher than those of most shallow and deep lakes in the world. HCHs and p,p'-DDT were derived from both the technical HCH and DDT and the usage of lindane and dicofol. Technical DDT and technical HCH may be used simultaneously, but technical DDT and lindane were not applied simultaneously in the catchment. Lindane was used not only in the period from 2002 to 2010 but also in the period from 1950 to 1964 in the catchment.

Pollution status of heavy metals and metalloids in Chinese lakes: Distribution, bioaccumulation and risk assessment.

Due to intensive human activities, most of Chinese lakes are suffering from the pollution of heavy metals and metalloids. Previous studies on heavy metals and metalloids in Chinese lakes were limited to a few lakes and mainly focused on sediments, to date the knowledge on heavy metals and metalloids in multiple media of Chinese lakes from a national perspective is scarce. We collected the data of nine heavy metals and metalloids including Copper (Cu), Cadmium (Cd), Lead (Pb), Mercury (Hg), Arsenic (As), Chromium (Cr), Nickel (Ni), Zinc (Zn), and Manganese (Mn) in water, surface sediments, and fish of 87 Chinese lakes sampled in the period from 2009 to 2019 from the literature, summarized the distribution of heavy metals and metalloids, evaluated their pollution, and apportioned their sources from a national perspective. Concentration of individual heavy metal and metalloid in water, surface sediments, and fish in Chinese lakes was in the ranges of 0.0080-282 µg/L, 0.020-33858 µg/g, and 0.00030-207 µg/g, respectively. 5.6 % and 33.3 % of lake water were polluted by Cd and As. 88.2 %, 78.6 %, and 66 % of lake sediments were polluted by Cd, Hg, and As. 35.3 %, 11.3 %, 52.4 %, and 12.8 % of Cd, Pb, As, and Cr concentrations in lake fish exceeded the food limits. Concentrations of heavy metals and metalloids in fish viscera were higher than those in other organs. Higher partition coefficient and bioaccumulation factors were found for Pb and Cd, Hg and Zn, respectively. Concentrations of heavy metals and metalloids in both water and sediments of lakes in eastern China were higher than those in western China. Concentrations of heavy metals and metalloids in both lake water and sediments of urban lakes were higher than those of rural lakes. Lakes with extremely high ecological risk of heavy metals and metalloids were mainly located in central China and eastern China. Pollution of heavy metals and metalloids in Chinese lakes was closely correlated with regional economic development. Heavy metals and metalloids in Chinese lakes were mainly derived from industrial, domestic, and mixed discharges. Cd and Hg were selected as the heavy metals for priority control in Chinese lakes.

Microplastics contributed much less than organic matter to the burial of polycyclic aromatic hydrocarbons by sediments in the past decades: a case study from an urban lake.

The role of microplastics in burying hydrophobic organic compounds remains largely unknown. Sediment cores collected from the center of a typical urban lake (Lake Qianhu) in China were chosen to explore the contribution of microplastics to the burial of polycyclic aromatic hydrocarbons (PAHs) by sediments, and to elucidate how this contribution changed with microplastic composition and the hydrophobicity of PAHs on a decade scale. Our results showed that the concentration of individual PAHs adsorbed by microplastics varied from detection limit (LOD) to 7.2 mg g-1 MP, which was much higher than the LOD to 31.0 µg g-1 TOC buried by total organic carbon. However, the amount of individual PAHs adsorbed by microplastics only contributed to 0-34.2% of that in sediments. Changes in the composition of microplastics, including the increased proportion of polyethylene and polypropylene : polyethylene polymer in sediments, resulted in the average microplastic sediment burial ratios (MSBRs) of most PAHs increasing by 0.13% to 2.7% in the period from 1997 to 2018 compared with those in the period from 1975 to 1996. The average MSBRs varied with the hydrophobicity of PAHs, which increased with log Kow value if it varied from 3.45 to 5.20, but decreased with log Kow if it was in the range of 5.30 to 6.50. Our study provides novel knowledge on the contribution of microplastics to the burial of PAHs by sediments.

Electrolytic Corrosion Behavior of 20 Cu-20 Ni-54 NiFe2O4-6 NiO Cermet with Interpenetrating Structure at 880 °C and 960 °C.

Here, 20 Cu-20 Ni-54 NiFe2O4-6 NiO (wt%) cermets were prepared via the powder metallurgy process, and the electrolytic corrosion behavior of the cermets at 880 °C and 960 °C was studied through the microstructure analysis by SEM and EDS. Results show that the ceramic phase is seriously affected by chemical corrosion at 880 °C electrolysis, and it is difficult to form a dense ceramic surface layer. A dense ceramic surface layer is formed on the bottom of the anode electrolyzed at 960 °C, and the dense layer thickens with the extension of the electrolysis time. The formation of the dense surface layer is mainly caused by the oxidation of Ni. The oxidation rate of the metallic phase and the corrosion rate of the ceramic phase have an important effect on the formation of the dense layer. In the corrosion process of NiFe2O4 phase, preferential corrosion of Fe element occurs first, and then NiO phase is precipitated from NiFe2O4 phase. After the NiO is dissolved and corroded, the NiFe2O4 grains collapse and the ceramic phase peels off from the anode.

Ecological regime shifts reduced burial ability of aromatic hydrocarbons by both inland and coastal waters but driven by various nutrients.

Huge synthetic chemicals and hydrocarbons have been released to inland waters and oceans, composing anthropogenic dissolved organic carbon (ADOC). They complement a large budget for CO2. Burial by inland and coastal marine sediments is crucial to reduce this budget. How ecological regime shifts influence the burial ability of ADOC by inland waters and coastal oceans, and what are the differences between them remain largely unknown. We collected sediment cores from an inland lake (Lake Qianhu) and the largest coastal lagoon (Lagoon Pinqing) in China, and chose 16 polycyclic aromatic hydrocarbons (PAHs) to address these issues. Burial ability of PAHs by sediments decreased by 55.1% - 98.5% in Lagoon Pinqing in the period from 1963 to 2018, and by 91.5% - 99.5% in Lake Qianhu in the period from 1970 to 2018. Burial ability and its decrease rate for most PAHs in Lagoon Pinqing were larger than those in Lake Qianhu in the same period. PAHs with higher hydrophobicity were more ready to be buried by both lake sediments and lagoon sediments. Burial ability of most PAHs in Lagoon Pinqing was negative correlated with total phosphorus concentration. In contrast, burial ability of most PAHs in Lake Qianhu was negative correlated with total nitrogen concentration. Regime shifted from phytoplankton to submerged macrophytes dominance in the year of 1976, and from submerged macrophytes to phytoplankton dominance in the year of 1999 in Lagoon Pinqing, driven by nitrogen. Regime shifted from vascular plants to phytoplankton dominance in Lake Qianhu in the year of 1991, driven by phosphorus. Different aromaticity and sources of organic matter related to regime shifts were responsible for the discrepancy of burial ability for PAHs by sediments of these two waters. Our study suggests that burial ability of ADOC by inland and coastal marine sediments will be reduced if eutrophication results in ecological regime shifts, which may undermine the efforts to mitigate global warming.

Thyroid endocrine disruption and hepatotoxicity induced by bisphenol AF: Integrated zebrafish embryotoxicity test and deep learning.

Bisphenol AF (BPAF) is an emerging contaminant prevalent in the environment as one of main substitutes of bisphenol A (BPA). It was found that BPAF exhibited estrogenic effects in zebrafish larvae in our previous study, while little is known about its effects on the thyroid and liver. A 7 d zebrafish embryotoxicity test was conducted to study the potential thyroid disruption and hepatotoxicity of BPAF. BPAF decreased levels of thyroid hormones and deiodinases but increased expressions of transthyretin at 12.5 and 125 µg/L after 7 d exposure, indicating that both the metabolism and transport of thyroid hormones were perturbed. The thyroid hormone receptor (TR) levels decreased significantly upon exposure to ≥12.5 µg/L BPAF, implying that BPAF acts as a TR antagonist, which coincided well with the prediction from the Direct Message Passing Neural Network. The liver impairment (mainly cell necrosis of hepatocytes) and apoptosis were triggered by 125 µg/L and ≥12.5 µg/L BPAF respectively, accompanied by the increased activities of caspase 3 and caspase 9. Thus BPAF might not be a safe alternative to BPA given the thyroid and liver toxicity. DMPNN appears useful to screen for thyroid disrupting activity from molecular structures.

The Application Status of Nanoscale Cellulose-Based Hydrogels in Tissue Engineering and Regenerative Biomedicine.

As a renewable, biodegradable, and non-toxic material with moderate mechanical and thermal properties, nanocellulose-based hydrogels are receiving immense consideration for various biomedical applications. With the unique properties of excellent skeletal structure (hydrophilic functional groups) and micro-nano size (small size effect), nanocellulose can maintain the three-dimensional structure of the hydrogel to a large extent, providing mechanical strength while ensuring the moisture content. Owing to its unique features, nanocellulose-based hydrogels have made excellent progress in research and development on tissue engineering, drug carriers, wound dressings, development of synthetic organs, 3D printing, and biosensing. This review provides an overview of the synthesis of different types of nanocellulose, including cellulose nanocrystals, cellulose nanofibers, and bacterial nanocellulose, and describes their unique features. It further provides an updated knowledge of the development of nanocellulose-based functional biomaterials for various biomedical applications. Finally, it discusses the future perspective of nanocellulose-based research for its advanced biomedical applications.

Eutrophication-induced regime shifts reduced sediment burial ability for polycyclic aromatic hydrocarbons: Evidence from Lake Taihu in China.

Regime shifts from a vegetated state with clear water to a turbid state with high contents of phytoplankton and suspended particles have been found in numerous waters worldwide. The fate and risks of hydrophobic organic contaminants (HOCs) in such waters may be altered, and the effects on burial ability of HOCs remain unknown. Influences of regime shifts on sediment burial ability for 16 polycyclic aromatic hydrocarbons (PAHs) (defined as burial/emission ratio) were investigated based on the evidence from the third largest freshwater lake (Lake Taihu) in China. The results of δ13C, δ15N, atomic ratio of Corg/N, and the content of total organic carbon testing and historical data suggested that the regime shifted abruptly from macrophytes to phytoplankton dominance in Lake Taihu in the late 1980s. The annual burial ability for the PAHs decreased gradually over time by 63.2%-98.9% in the period from 1980 to 2016. Meanwhile, the decrease rates of PAH burial ability varied from -1.65% y-1 to -2.98% y-1, depending on the hydrophobicity of the compound. The PAH burial ability varied with the dominant primary producers associated with the trophic level index of the water column. Regime shifts had a stronger influence on the burial ability of PAHs with higher hydrophobicity. This study helps to understand the fate and potential risks of HOCs in waters due to eutrophication-induced regime shifts.

Occurrence and Fluxes of Polycyclic Aromatic Hydrocarbons in the Third Largest Fresh Water Lake (Lake Taihu) in China.

Polycyclic aromatic hydrocarbons (PAHs) pose great risks to lake ecosystem and human health. Comprehensive knowledge on PAHs in lakes is critical for their risk control. 118 samples were collected from different environmental medium to study the occurrence and fluxes of 16 PAH in Lake Taihu. The average ∑PAH16 in air, water, phytoplankton, zooplankton, suspended particle matter, and surface sediments were 122 ng m-3, 61.3 ng L-1, 6500 ng g-1, 4940 ng g-1, 27,900 ng g-1, and 522 ng g-1, respectively. Sediments were contaminated by PAHs from pyrogenic sources. The average fluxes of air-water, dry deposition, and sinking of the 16 individual PAHs were 2900, 300, and 251 ng m-2 d-1. In the air-water column-surface sediments system, air-water exchange was the main transport pathway. In order to ensure safety of drinking water resources for local residence, the governments are suggested to work together to reduce PAHs emission and implement new energy policy.

Source apportionment of priority PAHs in 11 lake sediment cores from Songnen Plain, Northeast China.

Elevated concentrations of polycyclic aromatic hydrocarbons (PAHs) have been observed with rapid agricultural and industrial development in the Songnen Plain, Northeast China, but the prospective sources have not been yet apportioned. The concentration of PAHs was measured in 31 sediment samples from 11 Songnen Plain lakes in 2015. The background flux of PAHs in these lake sediments is < 463 µg m-2 year-1. The maximal concentration of 16 U.S. EPA priority PAHs (599 ng g-1) recorded in this study is lower or similar to that found in most of the lake sediments across China, but higher than remote areas, such as North America Rocky Mountains. Both concentration and flux of PAHs increased after the 1950s, which correspond to the industrial development in this area and would probably mark the beginning of the Anthropocene in this region. A chemical mass balance model estimated that straw burning was a major source of Σ13PAH (3-6 rings) during the past 200 years, with an average contribution of 22.1%, followed by forest fire (21.2%), burning of gasoline (19.1%), coal (12.2%), coke (4.8%) and diesel (3.9%), whereas the contribution from crude oil and natural gas was negligible (<1%). Straw burning (20.2-25.2%) and forest fire (16.7-30.6%) were major sources of PAHs and contributed increasing flux in the past 200 years. The elevated level of PAH recorded after 1950s in this region are also from burning of gasoline (26.1-26.4%), coal (15.3-15.8%), and coke (5.1-9.0%). The contribution of petrogenic sources (e.g., direct oil spill) to the concentration of Σ13PAH seemed to be ignorable, at least in these lakes.

Climate change has weakened the ability of Chinese lakes to bury polycyclic aromatic hydrocarbons.

Burial in sediments is a crucial way to reduce mobilization and risks of hydrophobic organic contaminants (HOCs), but ability of sediments to bury HOCs may be altered if the environment is changed. Whether the ability of sediments to bury HOCs has been affected by climate change remains largely unclear. We excluded the impacts of anthropogenic emissions and eutrophication from that of climate change, and for the first time found that not only the rising surface air temperature but also the declining wind speed and the reducing days with precipitation had weakened the ability of Chinese lakes to bury 16 polycyclic aromatic hydrocarbon (PAHs) by 69.2% ±â€¯9.4%-85.7% ±â€¯3.6% from 1951 to 2017. The relative contributions of the climatic variables to the reduced burial ability depended on the properties of the PAHs, and lakes. Burial ability of the PAHs responded differently to climate change, and was correlated to their volatilization and aqueous solubility, and lake area, catchment area/lake area ratio, and water depth. Our study suggests that not only the rising surface air temperature but also the declining wind speed and the reducing days with precipitation can undermine global efforts to reduce environmental and human exposure to PAHs.

Spatial and Historical Occurrence, Sources, and Potential Toxicological Risk of Polycyclic Aromatic Hydrocarbons in Sediments of the Largest Chinese Deep Lake.

Lake sediments are important reservoirs for polycyclic aromatic hydrocarbons (PAHs) in catchments. Knowledge of occurrence, sources, and toxicological risk of PAHs is crucial to abate their pollution and risk. We investigated the spatial and temporal occurrence, sources, and potential toxicological risks of 12 PAHs in the surface sediments and one sediment core of the largest deep lake (Lake Fuxian) of China. Our results indicated the average ΣPAH12 in the surface sediments of this lake was 1550.6 ± 231.4 ng g dw -1 , much higher than those of most Chinese shallow lakes. The average ΣPAH12 in the lake area was higher than that in the estuaries. The average ΣPAH12 in the estuaries of influent rivers was higher than that of the outlet river. Coal combustion, gasoline combustion, and diesel combustion were the major sources, which contributed 68.5%, 19.8%, and 11.8% to the ΣPAH12. The average total benzo[a]pyrene toxic equivalent concentration (TEQcarc) of the six most carcinogenic PAHs was 317.1 ± 86.3 ngTEQcarc g-1 in the surface sediments. The ΣPAH12 increased from 301.7 to 1964.4 ng g dw -1 from 1945 to 2011 and significantly increased with the GDP and population of the catchment. The contribution of coal combustion to the concentrations of PAHs increased gradually with time. The total TEQcarc, and the percentage of ΣPAHcarc to ΣPAH12 in the sediment core increased from 5.0 to 84.6 ngTEQcarc g-1 and from 5.7 to 23.3%, respectively. Our study highlights the importance of such deep waters in burying PAHs and the increasing risk of PAHs from human activities.

Trophic status affects the distribution of polycyclic aromatic hydrocarbons in the water columns, surface sediments, and plankton of twenty Chinese lakes.

The influence of trophic status on the distribution of hydrophobic organic contaminants (HOCs) in different subtropical shallow waters at large spatial scales remains largely unknown. In this study, samples of surface sediments, water, total suspended particles, phytoplankton, and zooplankton were simultaneously collected from 83 sampling sites in 20 subtropical oligotrophic to hyper-eutrophic shallow lakes in China to investigate the influence of trophic status on the spatial distribution and sinking fluxes of 16 polycyclic aromatic hydrocarbons (PAHs). The total concentration of the 16 PAHs (ΣPAH16) in the water columns of these lakes varied from 0.22 to 5.81 µg L-1, and increased with the trophic state index (TSI) and phytoplankton biomass. Phytoplankton were the dominant reservoir for the PAHs in the water column. However, the fraction of ΣPAH16 in phytoplankton decreased with the TSI. The average sinking flux of ΣPAH16 of the individual lakes varied from 2257.1 to 261674.1 mg m-2 d-1, and increased with the TSI of the lakes. The concentration of ΣPAH16 in the surface sediments ranged from 385.77 to 3784.37 ng gdw-1, and increased with the TSI and the ratio of phycocyanin/sediment organic carbon. It suggested that cyanobacterial biomass affected by trophic status dominated the occurrence of the PAHs in the surface sediments of these lakes. Biomass dilution and the biological pump affected the accumulation of the PAHs in phytoplankton, and zooplankton, and had more influence on the PAHs with higher hydrophobicity. Both the bioconcentration factors and bioaccumulation factors of the PAHs decreased with the TSI. No biomagnification was observed for the PAHs from phytoplankton to zooplankton in these lakes in spring. Our study provided novel knowledge for the coupling between eutrophication and HOCs in 20 subtropical shallow lakes with different trophic status.

Factors affecting annual occurrence, bioaccumulation, and biomagnification of polycyclic aromatic hydrocarbons in plankton food webs of subtropical eutrophic lakes.

The biological pump plays a critical role in the occurrence and fate of hydrophobic organic contaminants (HOCs) mostly in temperate and frigid oligotrophic waters. However, the factors for the long-term occurrence and fate of HOCs in subtropical eutrophic waters remain largely unknown. This study provides novel insights into biogeochemical and physical factors on the annual occurrence, bioaccumulation, and biomagnification of 16 polycyclic aromatic hydrocarbons (PAHs) in the plankton food webs of four Chinese subtropical eutrophic lakes by one-year simultaneous field observations for five compartments. The annual mean ΣPAH16 in the water columns ranged from 359.69 ±â€¯31.52 ng L-1 to 682.69 ±â€¯65.41 ng L-1, and increased with the annual mean trophic state index, and phytoplankton biomass of these lakes, but was independent on the proximity of the lakes to urban areas. Biodilution effect played an important role in the occurrence of the PAHs in both phytoplankton and zooplankton. In contrast to previous studies in oligotrophic waters, not only the biological pump but also the equilibrium partitioning and the indirect influence of eutrophication (high pH induced by phytoplankton, and phytoplankton life cycling) modulated the annual occurrence of the PAHs in the water columns of these eutrophic lakes. Biphasic correlations were found between the bioaccumulation factors of the PAHs by plankton and the temperature (n = 97-136, R2 = 0.06-0.24, p ≤ .008), and were related to plankton phenology. Bioaccumulation factors by plankton were dependent on the hydrophobicity of the PAHs (n = 16, R2 = 0.27-0.31, p ≤ .023), and decreased with plankton biomass (n = 94-103, R2 = 0.09-0.27, p ≤ .010). Trophic transfer of the PAHs from phytoplankton to zooplankton increased with phytoplankton biomass (n = 26, R2 = 0.27, p = .004), and the temperature (n = 102-135, R2 = 0.06-0.13, p ≤ .004), but decreased with lake trophic state index. Biomagnification only occurred during phytoplankton bloom periods.

Indirect influence of eutrophication on air - water exchange fluxes, sinking fluxes, and occurrence of polycyclic aromatic hydrocarbons.

How eutrophication affects biogeochemical processes of hydrophobic organic contaminants (HOCs) in aquatic environments is a pending challenge. Although the direct influence of eutrophication on biogeochemical processes of HOCs in waters has been well addressed, the indirect influence of eutrophication on biogeochemical processes of HOCs remains largely unknown. Here we take the large shallow eutrophic Lake Taihu in China and polycyclic aromatic hydrocarbons (PAHs) as examples to provide novel knowledge on the indirect influence of eutrophication on air - water exchange fluxes, sinking fluxes, and occurrence of HOCs. The air - water exchange fluxes of individual PAHs varied dramatically at different sites in all studied seasons. The sinking flux of ΣPAH16 was 14 855.3 ± 1579.9, 3548.9 ± 650.6, and 5588.4 ± 530.7 ng m-2 d-1 in spring, summer, and winter. The corresponding concentration of ΣPAH16 in surface sediments was 713.1 ± 78.6, 339.7 ± 36.6, and 293.0 ± 35.2 ng g-1 d.w. Our study for the first time suggested that recruitment of cyanobacteria from surface sediments to water column in spring reduced the concentrations of PAHs in surface sediments, but enhanced their concentrations in the bulk water column, and overwintering of cyanobacteria in winter enhanced the concentrations of PAHs in surface sediments. High pH induced indirectly by eutrophication decreased seasonal air - water exchange fluxes (enhanced net volatilization) of PAHs, reduced the aromaticity of surface sediments and the hydrophobicity of phytoplankton cell surface, and reduced the accumulation of PAHs in surface sediments and phytoplankton consequently. Sinking fluxes and daily loss of PAHs from the water column decreased with phytoplankton biomass because the fraction of organic matter sinking from the water column decreased with phytoplankton biomass. Our study provides novel complementary knowledge for the biological pump for HOCs, and has important implications for understanding the coupling between eutrophication and biogeochemical processes of HOCs in subtropical shallow eutrophic waters.

Effects of climate change on bioaccumulation and biomagnification of polycyclic aromatic hydrocarbons in the planktonic food web of a subtropical shallow eutrophic lake in China.

To date effects of climate change on bioaccumulation and biomagnification of chemical pollutants in planktonic food webs have rarely been studied. Recruitments of plankton have shifted earlier due to global warming. Global warming and precipitation patterns are projected to shift seasonally. Whether and how the shifts in plankton phenology induced by climate change will impact bioaccumulation and biomagnification of chemical pollutants, and how they will respond to climate change are largely unknown. Here, we combine data analysis of the past seven decades, high temporal resolution monitoring and model development to test this hypothesis with nine polycyclic aromatic hydrocarbons (PAHs) in the planktonic food web of a subtropical shallow eutrophic lake in China. We find biphasic correlations between both bioconcentration factors and bioaccumulation factors of the PAHs and the mean temperature, which depend on the recruitment temperatures of cyanobacteria, and copepods and cladocerans. The positive correlations between bioconcentration factors, bioaccumulation factors and the mean temperature will be observed less than approximately 13-18 days by 2050-2060 due to the shifts in plankton phenology. The PAHs and their bioaccumulation and biomagnification will respond seasonally and differently to climate change. Bioaccumulation of most of the PAHs will decrease with global warming, with higher decreasing rates appearing in winter and spring. Biomagnification of most of the PAHs from phytoplankton to zooplankton will increase with global warming, with higher increasing rates appearing in winter and spring. Our study provides novel insights into bioaccumulation and biomagnification of chemical pollutants in eutrophic waters under climate change scenarios.