Different phenanthrene degraders between free-cell mediated and biochar-immobilization assisted soil bioaugmentation as identified by RNA-based stable isotope probing (RNA-SIP).

Bioaugmentation (BA) is an effective approach to remove polycyclic aromatic hydrocarbons (PAHs) from contaminated soils, and biochar is frequently used to enhance PAH degradation performance. In this study, phenanthrene (PHE) degradation behavior and active degraders in a petroleum-contaminated soil were investigated and compared between free-cell mediated and biochar-immobilization assisted bioaugmentation. Biochar-immobilization assisted bioaugmentation (BA-IPB) introduced PHE degraders immobilized on biochar and effectively promoted PHE degradation, achieving higher PHE removal efficiencies within 24 h (~58 %) than free-cell mediated bioaugmentation (BA-FPB, ~39 %). Soil microbial community structure significantly changed in both BA-FPB and BA-IPB treatments. Through RNA-stable isotope probing (SIP), 14 and 11 bacterial lineages responsible for in situ PHE degradation were identified in BA-FPB and BA-IPB treatments, respectively. ASV_17 in BA-FPB treatment was Rhodococcus in the exogenous bacterial mixture; in contrast, none of exogenous bacteria were involved in PHE degradation in BA-IPB treatment. Methylobacterium (ASV_186), Xanthomonas (ASV_41), Kroppenstedtia (ASV_205), Scopulibacillus (ASV_243), Bautia (ASV_356), and Lactobacillus (ASV_376) were identified as PHE degraders for the first time. Our findings expanded the knowledge of the active PHE degraders and underlying mechanisms in bioaugmentation process, and suggested biochar-immobilization assisted bioaugmentation as a promising strategy for the bioremediation of PAH contaminated soils.

Anammox biofilter with denitrification sludge as seed in treating low nitrogen strength wastewater.

Deficient seed sludge, low substrate concentrations are recognized as the major barriers for the application of anaerobic ammonia oxidation (Anammox) to treat mainstream wastewater. In this work, anammox biofilter (A-BF) was started up by inoculating denitrification sludge at low nitrogen strength at 25 °C. The total nitrogen removal efficiency (TNRE) and nitrogen removal rate (NRR) reached 74.8 ± 3.4% and 0.81 kg-N m-3 d-1 under nitrogen loading rate (NLR) of 1.20 kg-N m-3 d-1 with 7.00 mg-NH4+-N L-1 and 10.00 mg-NO2--N L-1 as influent. 1.00-2.00 mg-DO L-1 negatively impacted effluent, but the total nitrogen of effluent (TNeff) was 10.65 ± 2.76 mg L-1, in limit of the standard of Class 1A for municipal WWTP discharge (GB18918-2002). The abundance of Planctomycetes increased from 0.6% to 1.4-2.6%, in which, Candidatus_Brocadia was the dominant genera. The results establish the application feasibility of A-BFs as advanced nitrogen removal technique in treating mainstream wastewater.

Altered active pyrene degraders in biosurfactant-assisted bioaugmentation as revealed by RNA stable isotope probing.

Bioaugmentation is an effective approach for removing pyrene from contaminated sites, and its performance is enhanced by a biosurfactant. To reveal the mechanisms of biosurfactant-assisted bioaugmentation, we introduced RNA stable isotope probing (RNA-SIP) in the pyrene-contaminated soils and explored the impacts of rhamnolipid on the pyrene degradation process. After 12-day degradation, residual pyrene was the lowest in the bioaugmentation treatment (7.76 ± 1.57%), followed by biosurfactant-assisted bioaugmentation (9.86 ± 2.58%) and enhanced natural attenuation (23.97 ± 1.05%). Thirteen well-known and two novel pyrene-degrading bacteria were confirmed to participate in the pyrene degradation. Pyrene degradation was accelerated in the biosurfactant-assisted bioaugmentation, manifested by the high diversity of active pyrene degraders. Our findings expand the knowledge on pyrene degrading bacteria and the mechanisms of pyrene degradation in a bioaugmentation process.

A review of biomass immobilization in anammox and partial nitrification/anammox systems: Advances, issues, and future perspectives.

Two biomass immobilization techniques; entrapment and carrier-based, attract increasing attention in anammox and partial nitrification/anammox (PN/A) systems. This paper provides a comprehensive review of the advances, outstanding issues, and future research directions in this field. The application of both entrapment and carrier-based biofilm immobilization for reactor start up, improving the nitrogen removal performance, and protecting autotrophic bacteria from environmental fluctuations in anammox and partial nitrification/anammox systems are summarized and discussed. The key characteristics of carriers for biomass immobilization are biocompatibility for supporting microbial growth, permeability for effective mass transfer, and physical/chemical stability for long-term use. Carriers without these characteristics must be improved and re-evaluated for their feasibility in applications. Lab-scale, pilot, and full-scale studies are needed to overcome the potential obstacles of preliminary studies, and to investigate the long-term performance of biomass immobilization techniques, especially using real wastewater as influent, which may introduce more complexity and threaten the carrier's immobilization. In addition, calculating the 'nitrogen removal rate normalized by the packing ratio of carriers (NRR-C)' in the immobilization system is strongly suggested to obtain a direct comparison of immobilization performance/limitations from different studies. This review will improve understanding of the major challenges of immobilization technology in anammox and PN/A systems and provide insights into the next-stage of research and full-scale applications.

Identification of pyrene degraders via DNA-SIP in oilfield soil during natural attenuation, bioaugmentation and biostimulation.

Pyrene is a model contaminant of high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs), which are compounds that have potential carcinogenic effects and pose a serious threat to human health. Finding effective pyrene-degrading bacteria is crucial for removing PAHs from soil. In this study, DNA-based stable isotope probing (DNA-SIP) technology was used to investigate pyrene degraders in PAH-contaminated oilfield soil during natural attenuation (NA), bioaugmentation (BA) and biostimulation (BS). The results show that BA played an important role in pyrene degradation with the highest pyrene removal rate (~95%) after 12 days incubation, followed by removal rates of ~90% for NA and ~30% for BS. In addition, 6 novel pyrene degraders were identified, while 12 well-known PAH degraders were demonstrated to participate in the biodegradation of pyrene. Additionally, the external homologous strains introduced during BA promoted the degradation of pyrene, but not by directly participating in the metabolism of the target compound. Rhamnolipid supplementation during BS promoted the involvement of more microorganisms in the degradation of pyrene, which was beneficial to identifying more pyrene degraders via DNA-SIP. These findings provide new insight into the effects of external homologous strains and supplementary rhamnolipids on pyrene degradation.

Insight: High intensity and activity carrier granular sludge cultured using polyvinyl alcohol/chitosan and polyvinyl alcohol/chitosan/iron gel beads.

The newly developed carrier granular sludge (CGS) with polyvinyl alcohol/chitosan (PVA/CS) and PVA/CS/Fe gel beads assistance showed higher intensity and anammox activity than the natural granular sludge (NGS). Through comprehensive investigation, it was found: (1) the gel beads provided a stable framework of cells entangle with extracellular polymeric substances (EPS) to enhance the sludge intensity. In this framework, ß-polysaccharides are distributed at the edge of CGS as a protection layer, α-polysaccharides and proteins are spread in the whole cross-section as backbones, and Fe2+/Fe3+ in CGS-PVA/CS/Fe act as bridges to link with the negatively charged groups on bacterial surfaces and proteins. (2) The porous gel beads satisfied a relatively unimpeded mass transfer. Thus, the sludge activity, microbe's metabolism, membrane transportation and environmental adaption in CGS were apparently improved. The results improved the understanding about the advantages of the CGS and indicated their possible application in full-scale anammox processes.

Enhancing anammox resistance to low operating temperatures with the use of PVA gel beads.

Low temperatures, or a sudden decrease in operating temperature, can seriously inhibit anammox activity, it is, therefore, important to maintain anammox activities at a low temperature. In this study, the use of gel beads to enhance the resistance of anammox biomass to a low temperature was investigated. The performance of three reactors: R1 without gel beads; R2 with polyvinyl alcohol/chitosan (PVA/CS); R3 with PVA/CS/Fe, was studied and compared in a temperature transition from 35 to 8 °C. When the operating temperature was ≥25 °C, there was little difference in nitrogen removal among the three reactors. Decreasing the temperature to < 25 °C created obvious difference between R1 and R2/R3. R1 had a nitrogen removal efficiency (NRE) of 33.1 ± 25.3% at 10 °C, significantly lower than that of R2 (90.5 ± 2.5%) or R3 (87.7 ± 11.1%). Unclassified Candidatus Brocadiaceae was the dominant genus at 10 °C, with an abundance of 44.4, 56.5 and 58.7% in R1, R2 and R3, respectively. These differences were attributed to the use of gel beads, which promoted the granulation of both the non-immobilized sludge and the immobilized biomass, resulting in higher anammox activities in R2/R3. The non-immobilized sludge of R1 was dominated by small particles (<300 µm) at 10 °C, while in R2 and R3 large particles (1000-2000 µm) were the main components. Furthermore, the immobilized biomass on gel beads exhibited much higher anammox activity and maintained a relatively high level of nitrate reductase and nitrite reductase in response to the temperature decrease. The Fe2+/Fe3+ in the PVA/CS/Fe gel beads further promoted microbial aggregation and led to an improved performance in R3 compared to R2. The results of this study demonstrate an effective approach to increase anammox resistance at low operating temperatures.

Achieving reliable partial nitrification and anammox process using polyvinyl alcohol gel beads to treat low-strength ammonia wastewater.

In this study, polyvinyl alcohol (PVA) gel beads were used to aid the partial nitrification and anammox process (PN/A) for treating low-strength ammonia wastewater. When treating synthetic and municipal wastewater, the reactor amended with PVA gel beads achieved a total nitrogen removal efficiency of 75.1 ± 8.4% and 66.6 ± 7.0% respectively, while the control reactor without PVA gel beads achieved 63.2 ± 7.8% and 28.2 ± 11.5% respectively. Dissolved oxygen (<0.5 mg O2 L-1) and substrate diffusion in porous PVA gel beads facilitated the formation of microbial stratification in the gel beads. Unclassified Candidatus Brocadiaceae (major anammox bacteria) and Ignavibacterium (major ammonia oxidizing bacteria) enriched in the inside and outside layers of PVA gel beads, which benefited the synergetic cooperation of these bacteria and protecting them from environmental fluctuations. This study provides a promising solution for achieving a reliable PN/A process in mainstream wastewater treatment.

DNA-SIP identification of phenanthrene-degrading bacteria undergoing bioaugmentation and natural attenuation in petroleum-contaminated soil.

DNA-stable isotope probing (SIP) with 13C labeled phenanthrene (PHE) as substrate was used to identify specific bacterial degraders during natural attenuation (NA) and bioaugmentation (BA) in petroleum contaminated soil. BA, with the addition of a bacterial suspension mixture named GZ, played a significant role in PHE degradation with a higher PHE removal rate (∼90%) than that of NA (∼80%) during the first 3 days, and remarkably altered microbial communities. Of the five strains introduced in BA, only two genera, particularly, Ochrobactrum, Rhodococcus were extensively responsible for PHE-degradation. Six (Bacillus sp., Acinetobacter sp., Xanthomonas sp., Conexibacter sp., Acinetobacter sp. and Staphylococcus sp.) and seven (Ochrobactrum sp., Rhodococcus sp., Alkanindiges sp., Williamsia sp., Sphingobium sp., Gillisia sp. and Massilia sp.) bacteria responsible for PHE degradation were identified in NA and BA treatments, respectively. This study reports for the first time the association of Xanthomonas sp., Williamsia sp., and Gillisia sp. to PHE degradation.

Nonoperative treatment versus volar locking plate fixation for elderly patients with distal radial fracture: a systematic review and meta-analysis.

BACKGROUND: This systematic review and meta-analysis assessed the role of nonoperative treatment and volar locking plate (VLP) fixation in elderly patients with distal radial fracture. METHODS: The systematic literature review identified randomized controlled trials (RCTs) and observational studies using VLP and nonoperative treatment for distal radial fractures in the elderly. Two investigators independently extracted data and evaluated the quality of the studies. A meta-analysis was performed using RevMan version 5.3. RESULTS: The five RCTs and six observational studies included 585 and 604 patients in the VLP and nonoperation groups, respectively. The quality of these 11 studies was moderate. Compared to nonoperation treatment, VLP did not improve the disabilities of the arm, shoulder and hand (DASH) score (weighted mean difference [WMD] = -1.67; 95% confidence interval [CI], -3.58--0.24; P = 0.09), decrease complications (odds ratio = 1.05; 95% CI, 0.51-2.19; P = 0.89), or improve range of motion in flexion, extension, pronation, supination, and radial deviation. The VLP group had better grip strength (WMD = 10.52; 95% CI, 6.19-14.86; P < 0.0001) and radiographic assessment than the nonoperation group. CONCLUSIONS: Although insufficient, the study evidence shows that VLP does not improve DASH scores, complications, or range of motion, but it might provide better grip strength and radiographic assessment than nonoperation treatment.

Granule-based immobilization and activity enhancement of anammox biomass via PVA/CS and PVA/CS/Fe gel beads.

Granule-based immobilization of anammox biomass assisted by polyvinyl alcohol/chitosan (PVA/CS) and PVA/CS/Fe gel beads was studied, via the operation of three identical up-flow reactors (R1 without gel beads, R2 with PVA/CS, R3 with PVA/CS/Fe) for 203 days. In the end, the nitrogen removal rates (NRR) were 5.3 ± 0.4, 10.0 ± 0.3 and 13.9 ± 0.5 kg-N m-3 d-1 for R1, R2 and R3, respectively. The porous PVA/CS and PVA/CS/Fe created a suitable eco-niche for anammox bacteria to grow and attach, thus being retained in the reactor. The EPS entangles newly grown cells within the gel beads, resulting in compact aggregation. The interaction between Fe ions added to PVA/CS/Fe gel beads and negatively charged EPS groups strongly promoted granule strength and compactness. The immobilization method proposed by this study was found to effectively improve biomass retention in the reactors, which is promising for advanced anammox process applications.

PVA/CS and PVA/CS/Fe gel beads' synthesis mechanism and their performance in cultivating anaerobic granular sludge.

Biomass washout from high-speed anaerobic suspended bed bio-reactors is still a challenge to their stable operation. Preserving active biomass to efficiently retain biomass in the reactor is one of the solutions to this problem. Herein, two carriers (polyvinyl alcohol/chitosan (PVA/CS) and PVA/CS/Fe gel beads) were prepared using the cross-linking method. The fourier transform infrared (FTIR) and 13C nuclear magnetic resonance (13C NMR) analyses showed that PVA/CS gel beads formed mainly through hydrogen-bonds (NH2OH-). Furthermore, FTIR, 13C NMR, energy dispersive spectrum (EDS), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed that PVA/CS/Fe gel beads formed mainly through chelate bond (NH2-FeM+OH-). The scanning electron microscope (SEM) results affirmed that the gel beads had rough and well-developed porous structure for the attachment of microbes. Furthermore, the abilities of gel beads on the cultivation of granular sludge in an up-flow anaerobic sludge bed (UASB) reactor were effectively demonstrated while treating wastewater polluted with glucose and alkali lignin. The results showed that the gel beads-assisted reactors had a higher performance than those without the gel beads. The cultivation of granules in these reactors was accelerated, while the granules became bigger and exhibited better settling velocities. The reactor with gel beads was easier to withstand a higher organic loading rate due to dense microbial aggregates, which were caused by more humic-like substance. Particularly, the reactor with PVA/CS/Fe gel beads was able to improve the overall robustness of the system due to stronger mechanical properties of gel beads, and also prevented cells detachment.

Biodegradation of Lignin Monomers Vanillic, p-Coumaric, and Syringic Acid by the Bacterial Strain, Sphingobacterium sp. HY-H.

Many bacterial strains have been demonstrated to biodegrade lignin for contaminant removal or resource regeneration. The goal of this study was to investigate the biodegradation amount and associated pathways of three lignin monomers, vanillic, p-coumaric, and syringic acid by strain Sphingobacterium sp. HY-H. Vanillic, p-coumaric, and syringic acid degradation with strain HY-H was estimated as 88.71, 76.67, and 72.78%, respectively, after 96 h. Correspondingly, the same three monomers were associated with a COD removal efficiency of 87.30, 55.17, and 67.23%, and a TOC removal efficiency of 82.14, 61.03, and 43.86%. The results of GC-MS, HPLC, FTIR, and enzyme activities show that guaiacol and o-dihydroxybenzene are key intermediate metabolites of the vanillic acid and syringic acid degradation. p-Hydroxybenzoic acid is an important intermediate metabolite for p-coumaric and syringic acid degradation. LiP and MnP play an important role in the degradation of lignin monomers and their intermediate metabolites. One possible pathway is that strain HY-H degrades lignin monomers into guaiacol (through decarboxylic and demethoxy reaction) or p-hydroxybenzoic acid (through side-chain oxidation); then guaiacol demethylates to o-dihydroxybenzene. The p-hydroxybenzoic acid and o-dihydroxybenzene are futher through ring cleavage reaction to form small molecule acids (butyric, valproic, oxalic acid, and propionic acid) and alcohols (ethanol and ethanediol), then these acids and alcohols are finally decomposed into CO2 and H2O through the tricarboxylic acid cycle. If properly optimized and controlled, the strain HY-H may play a role in breaking down lignin-related compounds for biofuel and chemical production.

Combining stable carbon isotope analysis and petroleum-fingerprinting to evaluate petroleum contamination in the Yanchang oilfield located on loess plateau in China.

This study evaluated petroleum contamination in the Yanchang (Shaanxi Yanchang Petroleum (Group) Co., Ltd.) oilfield, located in the loess plateau region of northern Shaanxi, China. Surface soil and sediment samples were collected from the wasteland, farmland, and riverbed in this area to assess the following parameters: total petroleum hydrocarbon (TPH), n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and carbon isotope ratios (δ13C). The results showed that TPH and PAH levels in the study area were 907-3447 mg/kg and 103.59-563.50 µg/kg, respectively, significantly higher than the control samples (TPH 224 mg/kg, PAHs below method quantification limit, MQL). Tests using δ13C to detect modified TPH (2238.66 to 6639.42 mg/kg) in the wastelands adjacent to the oil wells revealed more significant contamination than tests using extraction gravimetric analysis. In addition, "chemical fingerprint" indicators, such as low to high molecular weight (LMW/HMW) hydrocarbons, carbon preference index (CPI), and pristine/phytane (Pr/Ph), further confirmed the presence of heavy petroleum contamination and weathering. This has resulted in a nutrient imbalance and unsuitable pH and moisture conditions for microbial metabolic activities. This study evaluates petroleum contamination, which can inform contamination remediation on a case by case basis.

Ginsenoside Rb2 inhibits osteoclast differentiation through nuclear factor-kappaB and signal transducer and activator of transcription protein 3 signaling pathway.

Ginsenoside-Rb2 (Rb2) is a 20(S)-protopanaxadiol glycoside extracted from ginseng possessing various bioactivities which has drawn considerable interest regarding the area of bone metabolism. However, the effect of Rb2 on osteoclast differentiation remains unknown. In this study, we aimed to investigate the potential role of Rb2 in regulating osteoclast differentiation and the underlying molecular mechanisms. Osteoclast differentiation was induced by receptor activator nuclear factor-kappaB (NF-κB) ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) in mouse RAW 264.7 cells. The results showed that Rb2 dose-dependently inhibited the formation of the tartrate resistant acid phosphatase (TRAP)-positive multinucleated cells and TRAP expression. Furthermore, Rb2 promoted osteoprotegerin expression and bone resorption. The expression of osteoclast marker genes including nuclear factor of activated T cells c1 (NFATc1), c-Fos, OSCAR, and cathepsin K were also markedly inhibited by Rb2 treatment. Moreover, Rb2 significantly inhibited the RANKL-induced NF-κB activation. In addition, Rb2 also markedly suppressed the activation of signal transducer and activator of transcription protein 3 (STAT3) signaling pathway. Interestingly, the knockdown of STAT3 significantly strengthened the inhibitory effect of Rb2 on osteoclast differentiation. Taken together, our study suggests that Rb2 inhibits osteoclast differentiation associated with blocking NF-κB and STAT3 signaling pathways.

Kraft Lignin Biodegradation by Dysgonomonas sp. WJDL-Y1, a New Anaerobic Bacterial Strain Isolated from Sludge of a Pulp and Paper Mill.

Wastewater containing kraft lignin (KL) discharged from pulp and paper industries could cause serious environmental contamination. Appropriate effluent treatment is required to reduce the pollution. Investigations on anaerobic bacteria capable of degrading KL are beneficial to both lignin removal and biofuel regeneration from the effluent. In this paper, an anaerobic strain capable of degrading KL was isolated from the sludge of a pulp and paper mill and identified as Dysgonomonas sp. WJDL-Y1 by 16S rRNA analysis. Optimum conditions for KL degradation by strain WJDL-Y1 were obtained at initial pH of 6.8, C:N ratio of 6 and temperature of 33°C, based on statistical analyses by response surface methodology. For a 1.2 g/l KL solution, a COD removal rate of 20.7% concomitant with biomass increase of 17.6% was achieved after 4 days of incubation under the optimum conditions. After the treatment by strain WJDL-Y1, KL was modified and degraded.

Microbial toxicity of the insensitive munitions compound, 2,4-dinitroanisole (DNAN), and its aromatic amine metabolites.

2,4-Dinitroanisole (DNAN) is an insensitive munitions compound considered to replace conventional explosives such as 2,4,6-trinitrotoluene (TNT). DNAN undergoes facile microbial reduction to 2-methoxy-5-nitroaniline (MENA) and 2,4-diaminoanisole (DAAN). This study investigated the inhibitory effect of DNAN, MENA, and DAAN toward various microbial targets in anaerobic (acetoclastic methanogens) and aerobic (heterotrophs and nitrifiers) sludge, and the bioluminescent bacterium, Aliivibrio fischeri, used in the Microtox assay. Aerobic heterotrophic and nitrifying batch experiments with DAAN could not be performed because the compound underwent extensive autooxidation in these assays. DNAN severely inhibited methanogens, nitrifying bacteria, and A. fischeri (50% inhibitory concentrations (IC50) ranging 41-57µM), but was notably less inhibitory to aerobic heterotrophs (IC50>390 µM). Reduction of DNAN to MENA and DAAN lead to a marked decrease in methanogenic inhibition (i.e., DNAN>MENA≈DAAN). Reduction of all nitro groups in DNAN also resulted in partial detoxification in assays with A. fischeri. In contrast, reduction of a single nitro group did not alter the inhibitory impact of DNAN toward A. fischeri and nitrifying bacteria given the similar IC50 values determined for MENA and DNAN in these assays. These results indicate that reductive biotransformation could reduce the inhibitory potential of DNAN.

Pathways of reductive 2,4-dinitroanisole (DNAN) biotransformation in sludge.

As the use of the insensitive munition compound 2,4-dinitroanisole (DNAN) increases, releases to the environment may pose a threat to local ecosystems. Little is known about the environmental fate of DNAN and the conversions caused by microbial activity. We studied DNAN biotransformation rates in sludge under aerobic, microaerophilic, and anaerobic conditions, detected biotransformation products, and elucidated their chemical structures. The biotransformation of DNAN was most rapid under anaerobic conditions with H2 as a cosubstrate. The results showed that the ortho nitro group in DNAN is regioselectively reduced to yield 2-methoxy-5-nitroaniline (MENA), and then the para nitro group is reduced to give 2,4-diaminoanisole (DAAN). Both MENA and DAAN were identified as important metabolites in all redox conditions. Azo and hydrazine dimer derivatives formed from the coupling of DNAN reduction products in anaerobic conditions. Secondary pathways included acetylation and methylation of amine moieties, as well as the stepwise O-demethylation and dehydroxylation of methoxy groups. Seven unique metabolites were identified which enabled elucidation of biotransformation pathways. The results taken as a whole suggest that reductive biotransformation is an important fate of DNAN leading to the formation of aromatic amines as well as azo and hydrazine dimeric metabolites.

Distribution and source analysis of aluminum in rivers near Xi'an City, China.

To study the status and source of aluminum (Al) contamination, a total of 21 sampling sites along six rivers near Xi'an City (Shaanxi province, China) were investigated during 2008-2010. The results indicated that the average concentration of total Al (Al(t)) in the six rivers increased by 1.6 times from 2008 to 2010. The spatial distribution of Al(t) concentrations in the rivers near Xi'an City was significantly different, ranged from 367 µg/L (Bahe River) to 1,978 µg/L (Taiping River). The Al(t) concentration was highest near an industrial area for pulp and paper-making (2,773 µg/L), where the Al level greatly exceeded the water quality criteria of both the USA (Criterion Continuous Concentration, 87 µg/L) and Canada (100 µg/L). The average concentration of inorganic monometric aluminum (Al(im)) was 72 µg/L which would pose threats to fishes and other aquatic lives in the rivers. The concentrations of exchangeable Al (Al(ex)) in the sediment of the Taiping River sampled were relatively high, making it to be an alternative explanation of increasing Al concentrations in the rivers near Xi'an City. Furthermore, an increasing Al level has been detected in the upstream watershed near Xi'an City in recent years, which might indicate another notable pollution source of Al.