The toxic effects of nanoparticles on individual organisms have been widely investigated, while few studies have investigated the effects of nanoparticles on ubiquitous multicommunity microbial ...aggregates. Here, periphyton as a model of microbial aggregates, was employed to investigate the responses of microbial aggregates exposed continuously to Fe2O3 nanoparticles (5.0 mg L-1) for 30 days. The exposure to Fe2O3 nanoparticles results in the chlorophyll (a, b, and c) contents of periphyton increasing and the total antioxidant capacity decreasing. The composition of the periphyton markedly changes in the presence of Fe2O3 nanoparticles and the species diversity significantly increases. The changes in the periphyton composition and diversity were due to allelochemicals, such as 3-methylpentane, released by members of the periphyton which inhibit their competitors. The functions of the periphyton represented by metabolic capability and contaminant (organic matter, nitrogen, phosphorus and copper) removal were able to acclimate to the Fe2O3 nanoparticles exposure via self-regulation of morphology, species composition and diversity. These findings highlight the importance of both physiological and ecological factors in evaluating the long-term responses of microbial aggregates exposed to nanoparticles.
Photic biofilms widely exist on the surface of paddy soil and play a key role in nutrient transformation and accumulation in the soil–water interface. However, whether and how photic biofilms affect ...nitrogen cycles in the subsoil remained unclear. This study investigated the processes and mechanisms of nitrate reduction in waterlogged paddy soil in the presence (treatment) or absence (control) of photic biofilms. The observed nitrate reduction rate constant (k obs ) in the treatment soil increased 1.7 times compared with control. This accelerated k obs was attributed to the synergistic effect between poorly crystalline Fe minerals and autotrophic denitrifiers in soil, which was highly related to the presence of the photic biofilms. Photic biofilms aggravating daily redox oscillations at the soil–water interface promoted the formation of poorly crystalline Fe minerals available for microorganisms. Thus, photic biofilms increased the relative abundance of electroactive bacteria (Sphingomonadaceae and Xanthobacteraceae), iron reduction bacteria (Geobacter and Ignavibacterium), and denitrifiers (Rhodanobacteraceae and Burkholderiaceae) with higher copy numbers of nirK, nirS, and nosZ genes, thereby accelerating the nitrate reduction. Additionally, poorly crystalline Fe minerals contributed to improving interfacial electron transfer ability, which improved the activity of denitrifiers. These results suggested that the photic biofilms bioelectrochemically mediated the nitrate reduction in the waterlogged paddy soil.
Heavy metals or metalloids (HMs) in agricultural soils at high geological background areas could inherit the characteristics of parent materials, which would affect HM accumulation in crops. However, ...the specific impact of different parent materials on the behavior of HMs was unclear. This study focused on the bioavailability and risk variations of HMs in paddy soils derived from eluvial and alluvial parent materials in the Xitiaoxi catchment based on the total concentration, fraction, and risk assessment of HMs. The results showed that the paddy soil in the alluvial area had a higher bioavailability and risk level of HMs than those in the eluvial area, due to the increased proportion of activated HMs in the alluvial paddy soil. The increase in activated HMs was associated with a decrease in soil acidity and fertility as well as intensified anthropogenic activities within the alluvial study area. The spatial distribution of HM risk in soil samples demonstrated that the risk level of HMs was related to the exposure of black shale in eluvial soil, while the risk level of HMs in alluvial soil was negatively correlated with distance from the riverside. The source apportionment results further indicated that the alluvial paddy soil had lower geological but higher anthropogenic sources, especially for Cd, Pb, and Cu. In summary, the alteration in the properties of parent materials during river transportation and more anthropogenic sources raised the bioavailability and risk of HMs in the alluvial paddy ecosystem. This study provided new insights into HM risk assessment and control in agricultural soils developed from different parent materials within a catchment with a high geological background.
The toxic effects of nanoparticles on individual organisms have been widely investigated, while few studies have investigated the effects of nanoparticles on ubiquitous multicommunity microbial ...aggregates. Here, periphyton as a model of microbial aggregates, was employed to investigate the responses of microbial aggregates exposed continuously to Fe
O
nanoparticles (5.0 mg L
) for 30 days. The exposure to Fe
O
nanoparticles results in the chlorophyll (a, b, and c) contents of periphyton increasing and the total antioxidant capacity decreasing. The composition of the periphyton markedly changes in the presence of Fe
O
nanoparticles and the species diversity significantly increases. The changes in the periphyton composition and diversity were due to allelochemicals, such as 3-methylpentane, released by members of the periphyton which inhibit their competitors. The functions of the periphyton represented by metabolic capability and contaminant (organic matter, nitrogen, phosphorus and copper) removal were able to acclimate to the Fe
O
nanoparticles exposure via self-regulation of morphology, species composition and diversity. These findings highlight the importance of both physiological and ecological factors in evaluating the long-term responses of microbial aggregates exposed to nanoparticles.
The roles of different extracellular polymeric substance (EPS) fractions in microbial communities, such as periphytic biofilms, are unclear. In this study, three EPS fractions extracted from a ...periphytic biofilm were employed to investigate their ability to affect Fe
2
O
3
nanoparticle (IONP) toxicity. The addition of IONPs promoted the production of EPS and reactive oxygen species. The bound EPS protected the microbial cells in the periphytic biofilm from oxidative damage caused by IONPs. Different EPS fractions had different roles in affecting IONPs
via
different mechanisms, specifically, the soluble EPS increased the hydrodynamic diameter of IONPs and promoted IONP aggregation, the flocculation efficiency of the tightly bound EPS increased during exposure to IONPs, and the loosely bound EPS presented high biosorption of IONPs. The binding of IONPs with abundant functional groups was the main combination mode between different EPS fractions and IONPs. The beneficial changes in composition, structure and functional groups of EPS during exposure to IONPs in turn facilitate the elimination of their toxicity. This study contributes to a better understanding of the resistance mechanism of the periphytic biofilm to IONP exposure and the roles of EPS fractions in defending against nanotoxicity.
The roles of different extracellular polymeric substance fractions of a periphytic biofilm in defending against Fe
2
O
3
nanoparticle toxicity.
The presence of nitrite (NO
) is inevitable with concentrations of several mg L
in some typical water bodies. In this study, UV at wavelength of 365 nm was investigated to degrade contaminants of ...emerging concern (CECs) in the presence of NO
at environmentally relevant concentrations (0.1-5.0 mg L
). Six selected CECs with different structures were efficiently removed because of the generation of reactive nitrogen species (RNS) and hydroxyl radical (HO
) from photolysis of NO
. Contributions of UV
photolysis, RNS, and HO
to CEC degradation in UV
/NO
system were calculated, and RNS were found to be the predominant species that are responsible for CEC degradation. The second major contributor is HO
for the degradation of selected CECs except for the case of sulfadiazine. Impacts of water matrix components (including dissolved oxygen, solution pH, and natural organic matter) on CEC degradation in UV
/NO
system were evaluated. Furthermore, evolution profiles of CECs and NO
in UV
/NO
system were tracked when actual water samples were used as background, and a simultaneous removal of CECs and NO
was observed. Transformation products of bisphenol A and carbamazepine were proposed according to the results of HPLC/MS and quantum chemistry calculations. Nitration induced by RNS and hydroxylation induced by HO
are main reactions occurred during CEC degradation in UV
/NO
system. Overall, UV
is a potential technology to remove CECs and NO
in aquatic environment when residual NO
is present. Our present study also provides possibility for the application of sunlight to remediate water co-polluted by CECs and NO
.
The roles of different extracellular polymeric substance (EPS) fractions in microbial communities, such as periphytic biofilms, are unclear. In this study, three EPS fractions extracted from a ...periphytic biofilm were employed to investigate their ability to affect Fe
2
O
3
nanoparticle (IONP) toxicity. The addition of IONPs promoted the production of EPS and reactive oxygen species. The bound EPS protected the microbial cells in the periphytic biofilm from oxidative damage caused by IONPs. Different EPS fractions had different roles in affecting IONPs
via
different mechanisms, specifically, the soluble EPS increased the hydrodynamic diameter of IONPs and promoted IONP aggregation, the flocculation efficiency of the tightly bound EPS increased during exposure to IONPs, and the loosely bound EPS presented high biosorption of IONPs. The binding of IONPs with abundant functional groups was the main combination mode between different EPS fractions and IONPs. The beneficial changes in composition, structure and functional groups of EPS during exposure to IONPs in turn facilitate the elimination of their toxicity. This study contributes to a better understanding of the resistance mechanism of the periphytic biofilm to IONP exposure and the roles of EPS fractions in defending against nanotoxicity.
Inspired by the features of both transition metal oxide and natural clinoptilolite (flaky structure with suitable pore diameter and open skeleton structure), we adopted a robust strategy by ...immobilization of nickel ferrite nanoparticles (NiFe
O
) on the clinoptilolite surface via typical citric acid combustion method. The hybrid catalyst exhibited enhanced peroxymonosulfate (PMS) activation efficiency and bisphenol A (BPA) degradation performance. Calculated by effective equivalent of NiFe
O
, it is found that the reaction rate constant (k) of NiFe
O
/clinoptilolite/PMS system (0.1859 min
) was 11.9 times higher than that of bare NiFe
O
/PMS system (0.0156 min
), which demonstrated that catalyst would be conjugated to PMS or contaminant efficiently and renders the rapid degradation and mineralization in the presence of clinoptilolite. After comprehensive characterization analysis and DFT simulations, natural mineral carrier effect (i.e. decreased crystalline size, increased oxygen vacancy content, etc.), abundant surface-bonded and structural hydroxyl groups as well as effective bonding with iron or nickel ions charged for the potential activation mechanism of PMS by NiFe
O
/clinoptilolite composite. And it is indicated that not only
OH and SO
, but also
O
was involved into series reactions. Overall, this study put forward a green and promising technology for high-toxic wastewater treatment.
The responses of periphytic biofilm to CeO
nanoparticle (CNP) exposure were explored by investigating community shifts and pollutant removal. Results showed that CNPs entered the sensitive microbial ...cells in the periphytic biofilm, leading to cytomembrane damage and intracellular reactive oxygen species (ROS) generation. The periphytic biofilm communities were, however, able to adapt to the prolonged exposure and maintain their pollutant removal (i.e., phosphorus, nitrogen and copper, organic matter) performance. Observations under synchrotron radiation scanning transmission X-ray microscopy revealed that fewer CNPs were distributed in algal cells compared to bacterial cells, wherein the transformation between Ce(IV) and Ce(III) occurred. High-throughput sequencing further showed that the proportion of algae, such as Leptolyngbya and Nostoc, significantly increased in the periphytic biofilm exposed to CNPs while the proportion of bacteria, such as Bacilli and Gemmatimonadetes, decreased. This change in community composition might be the primary reason for the sustained pollutant removal performance of the periphytic biofilm.
An innovative advanced oxidation process was successfully developed to photocatalytic-degradation of estrone through the synergistic effect of biochar and Bi/Bi
O
in bismuth-containing photocatalytic ...biochar (BiPB). The highest reaction rate constant (k
) of estrone degradation by BiPB was 0.045 min
under the conditions of initial concentration of estrone =10.4 μmol L
, BiPB =1 g L
, pH = 7.0. The k
was almost tenfold and more than 20 times than that of biochar without bismuth impregnation and pristine Bi/Bi
O
, respectively. The best photocatalytic performance of BiPB composites for the degradation of estrone was primarily attributed to generation of OH radicals. Impregnation of bismuth helped control the concentration of persistent free radicals (PFRs) and develop a hierarchical porous structure of biochar. The presence of biochar facilitated pre-concentration estrone on BiPB and improved the separation and transfer efficiency of charge carriers. The synergistic effect between biochar and Bi/Bi
O
contributed to the generation of OH radicals for estrone degradation under neutral pH conditions. The transformation pathway of estrone was also proposed based on the measured transformation products in the presence of BiPB. The high efficiency of BiPB composites indicated that this easily-obtained material was promising for estrone-wastewater treatment applications as a low-cost composite photocatalyst.
