Liping Lou

Spatial variation and source apportionment of water pollution in Qiantang River (China) using statistical techniques

Understanding the spatial distribution and apportioning the sources of water pollution are important in the study and efficient management of water resources. In this work, we considered data for 13 water quality variables collected during the year 2004 at 46 monitoring sites along the Qiantang River (China). Fuzzy comprehensive analysis categorized the data into three major pollution zones (low, moderate, and high) based on national quality standards for surface waters, China. Most sites classified as low pollution zones (LP) occurred in the main river channel, whereas those classified as moderate and high pollution zones (MP and HP, respectively) occurred in the tributaries. Factor analysis identified two potential pollution sources that explained 67% of the total variance in LP, two potential pollution sources that explained 73% of the total variance in MP, and three potential pollution sources that explained 80% of the total variance in HP. UNMIX was used to estimate contributions from identified pollution sources to each water quality variable and each monitoring site. Most water quality variables were influenced primarily by pollution due to industrial wastewater, agricultural activities and urban runoff. In LP, non-point source pollution such as agricultural runoff and urban runoff dominated; in MP and HP, mixed source pollution dominated. The pollution in the small tributaries was more serious than that in the main channel. These results provide information for developing better pollution control strategies for the Qiantang River.

Evidence for nitrite-dependent anaerobic methane oxidation as a previously overlooked microbial methane sink in wetlands

Significance Given the current pressing need to more fully understand the methane cycle on Earth, in particular, unidentified sinks for methane, identifying and quantifying novel sinks for methane is fundamental importance. Here, we provide previously unidentified direct evidence for the nitrite-dependent anaerobic methane oxidation (n-damo) process as a previously overlooked microbial methane sink in wetlands by stable isotope measurements, quantitative PCR assays, and 16S rRNA and particulate methane monooxygenase gene clone library analyses. It is estimated that n-damo could consume 4.1–6.1 Tg of CH4 m−2 per year in wetlands under anaerobic conditions, which is roughly 2–6% of current worldwide CH4 flux estimates for wetlands. Given the worldwide increase in nitrogen pollution, this methane sink may become more important in the future. The process of nitrite-dependent anaerobic methane oxidation (n-damo) was recently discovered and shown to be mediated by “Candidatus Methylomirabilis oxyfera” (M. oxyfera). Here, evidence for n-damo in three different freshwater wetlands located in southeastern China was obtained using stable isotope measurements, quantitative PCR assays, and 16S rRNA and particulate methane monooxygenase gene clone library analyses. Stable isotope experiments confirmed the occurrence of n-damo in the examined wetlands, and the potential n-damo rates ranged from 0.31 to 5.43 nmol CO2 per gram of dry soil per day at different depths of soil cores. A combined analysis of 16S rRNA and particulate methane monooxygenase genes demonstrated that M. oxyfera-like bacteria were mainly present in the deep soil with a maximum abundance of 3.2 × 107 gene copies per gram of dry soil. It is estimated that ∼0.51 g of CH4 m−2 per year could be linked to the n-damo process in the examined wetlands based on the measured potential n-damo rates. This study presents previously unidentified confirmation that the n-damo process is a previously overlooked microbial methane sink in wetlands, and n-damo has the potential to be a globally important methane sink due to increasing nitrogen pollution.

Sorption and ecotoxicity of pentachlorophenol polluted sediment amended with rice-straw derived biochar

To investigate the feasibility of using biochar to control organic pollutants in sediments, we extracted biochar from rice-straw combustion residues (RBC) and studied its adsorption ability and effect on seed germination ecotoxicity of pentachlorophenol (PCP). The results showed that the Freundlich and dual-mode models could describe all the sorption isotherm data well, and the log K(OC) values increased with increasing RBC content. With 50 mg kg(-1) PCP in the sediment, a significant seed growth inhibition (P<0.01) was observed. The addition of 2.0% RBC lowered the PCP concentration in the extraction liquid from 4.53 to 0.17 mg L(-1) and increased the germination rate and root length significantly. Furthermore, it was found that the addition of RBC had no toxic but stimulative effect on root elongation. Consequently, RBC could serve as a potential supersorbent for the remediation of organic pollution in situ.

Distribution and diversity of anaerobic ammonium‐oxidizing bacteria in the sediments of the Qiantang River

Anaerobic ammonium oxidation (anammox) is an important process in the marine nitrogen cycle. However, little is known about the distribution, diversity and abundance of anammox bacteria in inland river ecosystems. Here, we found the presence of diverse anammox bacteria in a freshwater river - the Qiantang River, Zhejiang Province (China). The phylogenetic analysis of 16S rRNA genes showed that Brocadia genus, Kuenenia genus, Scalindua genus and three new anammox bacterial clusters could be detected together in Qiantang River sediments, suggesting a higher anammox bacterial diversity in the Qiantang River ecosystem than in open ocean environments where only Scalindua genus was detected. Brocadia and Kuenenia appeared to be the most common anammox bacterial genera in the Qiantang River. Redundancy analysis showed that the sediment organic carbon (OrgC) content had significant influence on the distribution of anammox bacteria in Qiantang River sediments. Pearson correlation analyses showed that OrgC content significantly influenced the anammox bacterial diversity. The results of real-time quantitative PCR showed spatial variations of anammox bacterial abundances which were highly correlated with the sediment total inorganic nitrogen content. These results demonstrated the distribution of diverse anammox bacteria and the influences of environmental factors on anammox bacterial communities in Qiantang River sediments.

Distribution and Diversity of Nitrite-Dependent Anaerobic Methane-Oxidising Bacteria in the Sediments of the Qiantang River

Nitrite-dependent anaerobic methane oxidation (n-damo) process was reported to be mediated by “Candidatus Methylomirabilis oxyfera”, which belongs to the candidate phylum NC10. M. oxyfera-like bacteria have been detected in lake ecosystems, while their distribution, diversity and abundance in river ecosystems have not been well studied. In this study, both the 16S rRNA and the pmoA molecular biomarkers confirmed the presence of diverse NC10 phylum bacteria related to M. oxyfera in a river ecosystem—the Qiantang River, Zhejiang Province (China). Phylogenetic analysis of 16S rRNA genes demonstrated that the recovered M. oxyfera-like sequences could be grouped into several distinct clusters that exhibited 89.8xa0% to 98.9xa0% identity to the M. oxyfera 16S rRNA gene. Similarly, several different clusters of pmoA gene sequences were observed, and these clusters displayed 85.1–95.4xa0% sequence identity to the pmoA gene of M. oxyfera. Quantitative PCR showed that the abundance of M. oxyfera-like bacteria varied from 1.32u2009±u20090.16u2009×u2009106 to 1.03u2009±u20090.12u2009×u2009107 copies g (dry weight)−1. Correlation analysis demonstrated that the total inorganic nitrogen content, the ammonium content and the organic content of the sediment were important factors affecting the distribution of M. oxyfera-like bacterial groups in the examined sediments. This study demonstrated the distribution of diverse M. oxyfera-like bacteria and their correlation with environmental factors in Qiantang River sediments.

Broad Distribution of Diverse Anaerobic Ammonium-Oxidizing Bacteria in Chinese Agricultural Soils

ABSTRACT Anaerobic ammonium-oxidizing (anammox) bacteria have been detected in many marine and freshwater ecosystems. However, little is known about the distribution, diversity, and abundance of anammox bacteria in terrestrial ecosystems. In this study, anammox bacteria were found to be present in various agricultural soils collected from 32 different locations in China. Phylogenetic analysis of the 16S rRNA genes showed “Candidatus Brocadia,” “Candidatus Kuenenia,” “Candidatus Anammoxoglobus,” and “Candidatus Jettenia” in the collected soils, with “Candidatus Brocadia” being the dominant genus. Quantitative PCR showed that the abundance of anammox bacteria ranged from 6.38 × 104 ± 0.42 × 104 to 3.69 × 106 ± 0.25 × 106 copies per gram of dry weight. Different levels of diversity, composition, and abundance of the anammox bacterial communities were observed, and redundancy analysis indicated that the soil organic content and the distribution of anammox communities were correlated in the soils examined. Furthermore, Pearson correlation analysis showed that the diversity of the anammox bacteria was positively correlated with the soil ammonium content and the organic content, while the anammox bacterial abundance was positively correlated with the soil ammonium content. These results demonstrate the broad distribution of diverse anammox bacteria and its correlation with the soil environmental conditions within an extensive range of Chinese agricultural soils.

Spatial distribution and factors shaping the niche segregation of ammonia-oxidizing microorganisms in the Qiantang River, China.

ABSTRACT Ammonia oxidation is performed by both ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, the current knowledge of the distribution, diversity, and relative abundance of these two microbial groups in freshwater sediments is insufficient. We examined the spatial distribution and analyzed the possible factors leading to the niche segregation of AOA and AOB in the sediments of the Qiantang River, using clone library construction and quantitative PCR for both archaeal and bacterial amoA genes. pH and NH4 +-N content had a significant effect on AOA abundance and AOA operational taxonomy unit (OTU) numbers. pH and organic carbon content influenced the ratio of AOA/AOB OTU numbers significantly. The influence of these factors showed an obvious spatial trend along the Qiantang River. This result suggested that AOA may contribute more than AOB to the upstream reaches of the Qiantang River, where the pH is lower and the organic carbon and NH4 +-N contents are higher, but AOB were the principal driver of nitrification downstream, where the opposite environmental conditions were present.

Evidence for the Cooccurrence of Nitrite-Dependent Anaerobic Ammonium and Methane Oxidation Processes in a Flooded Paddy Field

ABSTRACT Anaerobic ammonium oxidation (anammox) and nitrite-dependent anaerobic methane oxidation (n-damo) are two of the most recent discoveries in the microbial nitrogen cycle. In the present study, we provide direct evidence for the cooccurrence of the anammox and n-damo processes in a flooded paddy field in southeastern China. Stable isotope experiments showed that the potential anammox rates ranged from 5.6 to 22.7 nmol N2 g−1 (dry weight) day−1 and the potential n-damo rates varied from 0.2 to 2.1 nmol CO2 g−1 (dry weight) day−1 in different layers of soil cores. Quantitative PCR showed that the abundance of anammox bacteria ranged from 1.0 × 105 to 2.0 × 106 copies g−1 (dry weight) in different layers of soil cores and the abundance of n-damo bacteria varied from 3.8 × 105 to 6.1 × 106 copies g−1 (dry weight). Phylogenetic analyses of the recovered 16S rRNA gene sequences showed that anammox bacteria affiliated with “Candidatus Brocadia” and “Candidatus Kuenenia” and n-damo bacteria related to “Candidatus Methylomirabilis oxyfera” were present in the soil cores. It is estimated that a total loss of 50.7 g N m−2 per year could be linked to the anammox process, which is at intermediate levels for the nitrogen flux ranges of aerobic ammonium oxidation and denitrification reported in wetland soils. In addition, it is estimated that a total of 0.14 g CH4 m−2 per year could be oxidized via the n-damo process, while this rate is at the lower end of the aerobic methane oxidation rates reported in wetland soils.

Microbiology, ecology, and application of the nitrite-dependent anaerobic methane oxidation process

Nitrite-dependent anaerobic methane oxidation (n-damo), which couples the anaerobic oxidation of methane to denitrification, is a recently discovered process mediated by “Candidatus Methylomirabilis oxyfera.” M. oxyfera is affiliated with the “NC10” phylum, a phylum having no members in pure culture. Based on the isotopic labeling experiments, it is hypothesized that M. oxyfera has an unusual intra-aerobic pathway for the production of oxygen via the dismutation of nitric oxide into dinitrogen gas and oxygen. In addition, the bacterial species has a unique ultrastructure that is distinct from that of other previously described microorganisms. M. oxyfera-like sequences have been recovered from different natural habitats, suggesting that the n-damo process potentially contributes to global carbon and nitrogen cycles. The n-damo process is a process that can reduce the greenhouse effect, as methane is more effective in heat-trapping than carbon dioxide. The n-damo process, which uses methane instead of organic matter to drive denitrification, is also an economical nitrogen removal process because methane is a relatively inexpensive electron donor. This mini-review summarizes the peculiar microbiology of M. oxyfera and discusses the potential ecological importance and engineering application of the n-damo process.

Enrichment of an anammox bacterial community from a flooded paddy soil.

This study describes the enrichment of anammox bacteria in a column simulating oxygen limited flooded paddy soils, which are important man-made ecosystems that receive substantial amounts of fixed nitrogen. The upper 50 cm of the paddy soil, containing a high amount of ammonium [1.6-10.4 mmol N kg (dry weight)(-1)], was selected as the inoculum for anammox enrichment. After 18 months of incubation with freshwater from the paddy soil ecosystem, the enrichment culture consumed approximately 4 mmol ammonium l(-1) day(-1) and 5 mmol nitrite l(-1) day(-1). The maximum specific anammox activity of the culture was 35.7 μmol N g (dry weight)(-1) h(-1). Fluorescence in situ hybridization indicated that anammox cells constituted 50% ± 10% of the enrichment culture. The phylogenetic analyses of 16S rRNA and the diagnostic hydrazine synthase (hzsA) genes showed that two dominant anammox species were enriched from paddy soil. The enriched Candidatus Anammoxoglobus-like organisms showed a 16S rRNA gene similarity of 97.5-99.2% to Candidatus Anammoxoglobus propionicus and the Candidatus Jettenia-like organisms showed 92.1-93.1% 16S rRNA gene identity to Candidatus Jettenia asiatica. Real-time quantitative PCR of hzsA gene suggested that up to 10(10) copies g (dry weight)(-1) of soil anammox bacteria were present in the enrichment culture.