To Total Nitrogen Research Articles

The identification of nutrient limitations on eutrophication in Dianchi Lake, China

AbstractDue to rapid urbanisation and economic development, Dianchi Lake has been eutrophic since the 1980s. Control of nutrient loading is regarded as the primary restoration method. Two independent approaches: analysis of 13 years of Dianchi Lake monitoring data using Support Vector Machines (SVM) and a nutrient‐enrichment experiment, identified phosphorus and nitrogen as simultaneously limiting. Total phosphorus (TP) has a clear, stable correlation with chlorophyll‐a (Chl‐a) concentrations in Dianchi Lake. Compared to total nitrogen (TN), TP shows a stronger correlation when Chl‐a concentration is below 0.051 mg/L and an almost equal correlation when it is above this level. An excessive phosphorus to nitrogen ratio may stimulate compensatory fixation of atmospheric N2 by cyanobacteria; therefore, only reducing the external nitrogen input may not necessarily result in lower total nitrogen and chlorophyll concentrations. We recommend that reducing the lake TP load to the lowest economically‐feasible level is the most cost‐effective restoration measure.

Cultivation of Spirulina platensis in Digested Piggery Wastewater Pretreated by SBR with Operating Conditions Optimization

Digested piggery wastewater(DPW) contains high concentrations of nitrogen and phosphorus which could be used as a cost-effective culture medium for Spirulina platensis. However, Spirulina platensis would be limited by many factors in the complex composition of DPW, especially the high concentration of ammonium. In this paper, a traditional sequencing batch reactor(SBR) was used to remove these inhibitors in DPW. The retention of nitrate and nitrite in the effluent, which was used as nitrogen source for cultivating Spirulina platensis, was studied at different ratios of chemical oxygen demand(COD) to total nitrogen(TN) in the influent. By comparing the growth of Spirulina platensis in the related effluents, the operation condition of SBR was optimized. The lab-scale cultivation results showed that Spirulina platensis possessed a high biomass yield of 0.084 g·(L·d)-1 in the effluent when the COD/TN ratio of SBR influent was 3.0. In particular, the concentrations of ammonium, nitrate and nitrite in the effluent were 51.2 mg·L-1, 91.6 mg·L-1and 213.1 mg·L-1, respectively. Furthermore, the aforementioned effluent was also used to culture Spirulina platensis in a 120 L outdoor raceway pond, and the growth rate of Spirulina platensis reached(0.075±0.003)g·(L·d)-1 after 10-day culture. The protein content of Spirulina platensis was approximately 60% and the removal efficiency of ammonium was 99%. This study provides an alternative method for the utilization of DPW.

Removal of veterinary antibiotics from anaerobically digested swine wastewater using an intermittently aerated sequencing batch reactor

A lab-scale intermittently aerated sequencing batch reactor (IASBR) was applied to treat anaerobically digested swine wastewater (ADSW) to explore the removal characteristics of veterinary antibiotics. The removal rates of 11 veterinary antibiotics in the reactor were investigated under different chemical organic demand (COD) volumetric loadings, solid retention times (SRT) and ratios of COD to total nitrogen (TN) or COD/TN. Both sludge sorption and biodegradation were found to be the major contributors to the removal of veterinary antibiotics. Mass balance analysis revealed that greater than 60% of antibiotics in the influent were biodegraded in the IASBR, whereas averagely 24% were adsorbed by sludge under the condition that sludge sorption gradually reached its equilibrium. Results showed that the removal of antibiotics was greatly influenced by chemical oxygen demand (COD) volumetric loadings, which could achieve up to 85.1%±1.4% at 0.17±0.041kgCOD/m-3/day, while dropped to 75.9%±1.3% and 49.3%±12.1% when COD volumetric loading increased to 0.65±0.032 and 1.07±0.073kgCOD/m-3/day, respectively. Tetracyclines, the dominant antibiotics in ADSW, were removed by 87.9% in total at the lowest COD loading, of which 30.4% were contributed by sludge sorption and 57.5% by biodegradation, respectively. In contrast, sulfonamides were removed about 96.2%, almost by biodegradation. Long SRT seemed to have little obvious impact on antibiotics removal, while a shorter SRT of 30–40day could reduce the accumulated amount of antibiotics and the balanced antibiotics sorption capacity of sludge. Influent COD/TN ratio was found not a key impact factor for veterinary antibiotics removal in this work.

Performance and microbial community of aerobic dynamic membrane bioreactor enhanced by Cd(II)-accumulating bacterium in Cd(II)-containing wastewater treatment

In this study, a strain of Cd(II)-accumulating bacterium, Pseudoalteromonas sp. SCSE709-6, was inoculated into aerobic dynamic membrane bioreactor (ADMBR) as bioaugmentation to treat Cd(II)-containing wastewater, whilst the microbial community in the activated sludge and biofilm were compared integrated with performance under the cadmium stress and bioaugmentation. Results indicated that the performance of ADMBR was greatly inhibited by cadmium stress gradient but was substantially improved by bioaugmentation which corresponds to the obvious changes of microbial community. In genus level, Thiothrix and Meganema were predominant bacteria under cadmium stress, while Flavobacterium and Lactococcus were enriched after bioaugmentation. In phylum level, Bacteroidetes demonstrated a higher resistance against Cd(II) than Proteobacteria with bioaugmentation. Moreover, Stenotrophomonas and Dechloromonas relating to total nitrogen (TN) removal were mainly detected in biofilm, indicating the significant role of dynamic membrane. The promising results presented in this feasibility study demonstrated the great potential of using Cd(II)-accumulating bacterium to enhance the performance of activated sludge in treating Cd(II)-containing wastewater.

Response Characteristics of Algal Chlorophyll-a to Nitrogen, Phosphorus and Water Temperature in Lake Erhai Based on Quantile Regression

Based on water quality monitoring data of Lake Erhai from 1990 to 2013,the yearly and seasonally response characteristics of algal chlorophyll-a to total nitrogen (TN),total phosphorus (TP) and water temperature was investigated using quantile regression method.It indicated that water temperature was always the primary limiting factor of algal biomass indicated by chlorophyll a (Chl-a) across recent 24 years,but its limiting effect on algal Chl-a content was kept descending sharply and replaced much by nutrients (e.g.P,N) with the increasing eutrophic level.Especially the slope values of TP on Chl-a were kept ascending from -0.3 to 0.8.Since 2002,the positive effect of TN on Chl-a presented slow descending tendency,and P became the most important limiting nutrient factor of algal growth.According to the seasonal variation analysis,water temperature and N had dominant effects on algal Chl-a in spring and autumn,but they were replaced by P in the case of Chl-a>8 mg·m-3 in spring.In summer,N and P had strong interactive impacts on the algal growth,and the positive effect of P was stronger than that of N in the case of Chl-a>3 mg·m-3.In winter,algal biomass was co-limited by temperature and P.It suggested that P reduction is the prior choice of eutrophication control of Lake Erhai,and simultaneously reducing N load is necessary in the background of global warming.In addition,so far a emergency controlling measure should be taken to monitor algal blooming due to sharp ascending of water temperature within a few days in spring and autumn.

Performance and microbial community analysis of a novel DEAMOX based on partial-denitrification and anammox treating ammonia and nitrate wastewaters

In this study, a novel DEAMOX (DEnitrifying AMmonium OXidation) process coupling anammox with partial-denitrification generated nitrite (NO2−-N) from nitrate (NO3−-N) was developed for simultaneously treating ammonia (NH4+-N) and NO3−-N containing wastewaters. The performance was evaluated in sequencing batch reactors (SBRs) with different carbon sources for partial-denitrification: acetate (R1) and ethanol (R2). Long-term operation (180 days) suggested that desirable nitrogen removal was achieved in both reactors. The performance maintained stably in R1 despite the seasonal decrease of temperature (29.2 °C–12.7 °C), and high nitrogen removal efficiency (NRE) of 93.6% on average was obtained with influent NO3−-N to NH4+-N ratio (NO3−-N/NH4+-N) of 1.0. The anammox process contributed above 95% to total nitrogen (TN) removal in R1 with the nitrate-to-nitrite transformation ratio (NTR) of 95.8% in partial-denitrification. A little lower NRE was observed in R2 with temperature dropped from 90.0% at 22.7 °C to 85.2% at 16.6 °C due to the reduced NTR (87.0%–67.0%).High-throughput sequencing analysis revealed that Thauera genera were dominant in both SBRs (accounted for 61.53% in R1 and 45.17% in R2) and possibly played a key role for partial-denitrification with high NO2−-N accumulation. The Denitratisoma capable of complete denitrification (NO3−-N→N2) was found in R2 that might lead to lower NTR. Furthermore, different anammox species was detected with Candidatus Brocadia and Candidatus Kuenenia in R1, and only Candidatus Kuenenia in R2.

A Bayesian approach of high impaired river reaches identification and total nitrogen load estimation in a sparsely monitored basin.

In this study, a modeling framework based on the theory of SPAtially Referenced Regression On Watershed attributes (SPARROW) model was developed to identify impaired river reaches with respect to total nitrogen (TN) and estimate the TN sources in the Xin'anjiang River basin, which had limited monitoring sites. A Bayesian approach was applied to estimate the mean values and uncertainties of parameters, including land use export coefficients and in-stream attention rates. Based on the parameters, the midranges (25-75%) of annual TN concentrations were assessed by the model and 4.5% of river reaches in the basin were found to be with higher impaired probabilities (namely [TN]>1.5mg/l) than other reaches. The amount and yields of TN discharged from diffuse sources were estimated for each county in the basin. The results suggested that Tunxi City had the highest TN yields from farm land and population, while the highest TN yields in Huangshan City were from tea plantations. The outcomes of this study will guide the implementation of practical management measures to reduce TN loads.

Simultaneous denitrification and denitrifying phosphorus removal in a full-scale anoxic–oxic process without internal recycle treating low strength wastewater

Performance of a full-scale anoxic–oxic activated sludge treatment plant (4.0×105m3/day for the first-stage project) was followed during a year. The plant performed well for the removal of carbon, nitrogen and phosphorus in the process of treating domestic wastewater within a temperature range of 10.8°C to 30.5°C. Mass balance calculations indicated that COD utilization mainly occurred in the anoxic phase, accounting for 88.2% of total COD removal. Ammonia nitrogen removal occurred 13.71% in the anoxic zones and 78.77% in the aerobic zones. The contribution of anoxic zones to total nitrogen (TN) removal was 57.41%. Results indicated that nitrogen elimination in the oxic tanks was mainly contributed by simultaneous nitrification and denitrification (SND). The reduction of phosphorus mainly took place in the oxic zones, 61.46% of the total removal. Denitrifying phosphorus removal was achieved biologically by 11.29%. Practical experience proved that adaptability to gradually changing temperature of the microbial populations was important to maintain the plant overall stability. Sudden changes in temperature did not cause paralysis of the system just lower removal efficiency, which could be explained by functional redundancy of microorganisms that may compensate the adverse effects of temperature changes to a certain degree. Anoxic–oxic process without internal recycling has great potential to treat low strength wastewater (i.e., TN<35mg/L) as well as reducing operation costs.

Nitrogen Removal from Anaerobically Digested Swine Wastewater through Combined Ammonia Stripping and Membrane Bioreactor Processes

<abstract> <b><sc>Abstract.</sc></b> Anaerobically digested swine wastewater has high concentrations of total ammoniacal nitrogen (TAN) (approximately 1,000 mg N L^-1) and a low chemical oxygen demand (COD) to total nitrogen (TN) (COD/TN) ratio of <3.0, making it difficult to achieve a high TN removal rate using traditional biological nitrogen removal processes. The purpose of this study was to investigate the effectiveness of combining ammonia stripping (AS) and membrane bioreactor (MBR) processes to remove nitrogen from anaerobically digested swine wastewater. The coupling parameters that would lead to a high TN removal rate and cost effectiveness were also explored. Ammonia stripping was conducted at two pH levels of 10.0-10.5 (High-pH) and 9.0-9.5 (Low-pH). The MBR had the configuration of anoxic biofilm and aerobic MBR, and it was operated at two influent COD/TN ratios of 6.0-8.0 and 5.0-6.0 coupled with two TAN sludge loading rates in the oxic zone of 0.04-0.05 and 0.12-0.16 kg N kg^-1 mixed liquid suspended solid (MLSS) d^-1. Total nitrogen removal rate for the High-pH and Low-pH AS was 83% and 65%, respectively. In the MBR at a dissolved oxygen (DO) level of 6.12 ±0.69 mg L^-1, increasing the TAN sludge loading rate from 0.04 to 0.16 kg N kg^-1 MLSS d^-1 led to an increase in free ammonia from 0 to 4-9 mg L^-1 and an increase in nitrite accumulation rate (NAR) from 0% to 71%. At a TAN sludge loading rate in the oxic zone of 0.12 kg N kg^-1 MLSS d^-1 and NAR of 53%, the TN removal rate reached 82% in the MBR through shortcut nitrification and denitrification (SND). The influent biochemical oxygen demand (BOD₅) to TN (BOD₅/TN) ratio was 1.41, COD/TN was 5.41, and the oxidation-reduction potential (ORP) of the denitrification zone was as low as -300 to -400 mV. Among the experimental conditions examined, the combined Low-pH AS+SND process provided the highest TN removal rate of 94% with the least cost and HRT.

Diazotrophic bacterial community variability in a subtropical deep reservoir is correlated with seasonal changes in nitrogen.

Nitrogen-fixing microorganisms (diazotrophs) play important roles in aquatic biogeochemistry and ecosystem functioning. However, little is known about the spatiotemporal variation of diazotrophic microbial communities in deep subtropical reservoirs. In this study, denaturing gradient gel electrophoresis (DGGE), clone libraries, quantitative PCR, and quantitative reverse transcription (RT)-PCR were used together to examine the vertical and seasonal patterns of diazotrophic microbial communities based on nitrogenase (nifH) gene sequences in the Dongzhen Reservoir, China, across time (every 3 months for 1 year) and space (five different water depths). In general, the numbers of DGGE bands increased with water depth during the stratification seasons (spring, summer, and autumn), with the clone-library-based operational taxonomic unit (OTU) number and nifH gene diversity being highest in autumn (6 OTUs at depth 0 m; 15 OTUs at 33 m) and winter (12 OTUs at 0 m, 13 OTUs at 33 m) but decreasing drastically in spring (2 OTUs at 0 m, 3 OTUs at 33 m) and summer (3 OTUs at 0 m, 2 OTUs at 33 m). The nifH gene abundance was lowest in the water mixing season (winter average, 5.17 × 10(7) copies/L) but increased in the three other seasons (9.03 × 10(9) copies/L). Cyanobacteria (dominated by filamentous thermophilic cyanobacteria and Cylindrospermopsis raciborskii) were the most dominant diazotrophic group at all depths and seasons, while both alphaproteobacteria and gammaproteobacteria were co-dominant in the bottom waters in autumn and winter. The distinct seasonal and spatial patterns in diazotrophic communities were significantly related to total nitrogen (TN) and ammonium nitrogen (NH4-N) in the reservoir (P < 0.01). Further, TN showed a significant positive correlation with nifH RNA copy number (P < 0.05) and DGGE band number (P < 0.01), whereas the NH4-N was negatively correlated with nifH DNA copy number (P < 0.01) and positively with both RNA/DNA ratio (P < 0.01) and DGGE band number (P < 0.01). Our data indicated that water stratification, mixing, and nitrogen might drive the diazotrophic community structure and activity in complex ways, thereby influencing the aquatic nitrogen cycle. Therefore, adaptive reservoir management strategies should carefully consider the effects of water stratification for protecting drinking water quality and for controlling the potential for diazotrophic cyanobacteria blooms.

黄土高原不同乔木林土壤微生物量碳氮和溶解性碳氮的特征

PDF HTML阅读 XML下载 导出引用 引用提醒 黄土高原不同乔木林土壤微生物量碳氮和溶解性碳氮的特征 DOI: 10.5846/stxb201404030633 作者: 作者单位: 中国科学院水利部水土保持研究所,中国科学院水利部水土保持研究所,中国科学院水利部水土保持研究所,中国科学院水利部水土保持研究所,中国科学院水利部水土保持研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目(41171226);国家自然科学基金重点基金(41030532);新世纪优秀人才支持计划(NCET-12-0479);西北农林科技大学"优秀人才科研专项(QN2011049)" Soil microbial biomass nitrogen and carbon, water soluble nitrogen and carbon under different arbors forests on the Loess Plateau Author: Affiliation: Institute of soil and water conservation, CAS&MWR,Institute of soil and water conservation, CAS&MWR,Institute of soil and water conservation, CAS&MWR,Institute of soil and water conservation, CAS&MWR,Institute of soil and water conservation, CAS&MWR Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:选取黄土丘陵区子午岭4种不同乔木林下的0-5 cm和5-20 cm的土壤为研究对象,通过氯仿熏蒸浸提方法测定了微生物量碳氮、溶解性碳氮以及土壤的理化性质。研究结果表明,不同乔木林下0-5 cm土层土壤微生物量氮(MBN)土壤微生物量碳(MBC)均表现为:辽东栎 > 侧柏 > 油松 > 刺槐,5-20 cm土层为:侧柏 > 辽东栎 > 油松 > 刺槐,说明不同乔木林对土壤表层和下层的微生物量有明显的影响。上层土壤溶解性碳(DOC)、溶解性氮(DON)大于下层土壤。土壤微生物量碳氮比(MBC/MBN)在4-8之间,MBC/MBN 、MBN、MBC均表现为随着土层的深度逐渐降低的趋势。MBC与MBN具有显著的正相关性,MBN、MBC与有机碳(SOC)、土壤全氮(TN)、MBC/MBN、溶解性碳与微生物量碳之和(DOC+MBC)、溶解性氮与微生物量氮之和(DON+MBN)呈现出极显著的正相关性(P < 0.01)。DOC+MBC、DON+MBN比DOC、DON、MBC、MBN更能反映土壤微生物量与活性碳氮库。总体来说,人工刺槐林对土壤碳氮库的增加有一定的作用,但是相对于辽东栎和侧柏等天然次生林有一定的差距。 Abstract:The Loess Plateau is an important site for many ecological restoration studies in China. Different forest types can have a great influence on the soil environment, including carbon and nitrogen biogeochemical cycles. The soil microbial biomass can have a large effect on soil processes and soil microorganisms after vegetation restoration in the loess hilly area of the Loess Plateau. Understanding the relationships between soil physicochemical properties and soil microbial biomass under different forest types can provide useful information for vegetation restoration in the Loess Plateau. This study sampled soils in four different forest types to investigate the soil composition and correlation with soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN), soil dissolved organic nitrogen (DON) and soil dissolved organic carbon (DOC), the sum of DOC and MBC (DOC+MBC) and the sum of DON and MBN (DON+MBN). The sample sites were located on Ziwuling Mountain of the Loess Plateau. The four different forests were all established 15 years ago. The results showed that in the 0–5 cm soil layer of the 4 forest types, MBC ranged between 350 and 693.15 mg/kg, MBN ranged between 52.21 and 93.61 mg/kg, DON ranged between 53.49 and 89.07 mg/kg, DOC ranged between 302.33 and 460.87 mg/kg, DOC+MBC ranged between 543.72 and 1114.76 mg/kg and DON+MBN ranged between 105.70 and 182.68 mg/kg. All values at 0–5 cm were higher than values obtained in the 5–20 cm soil layer. Quercus liaotungensis and Biota orientalis had the highest MBC and MBN, Pinus tabulaeformis Carr. and Robinia pseudoacacia had the lowest SMBC and MBN. Soil DOC was not significantly different between forest soils for the soil layer 0-5 cm. DOC+MBC of Q. liaotungensis and B. orientalis were significantly higher than for P. tabulaeformis Carr. and R. pseudoacacia, with R. pseudoacacia having the lowest values of DOC+MBC. Soil DON was highest for Q. liaotungensis and was significantly different from the other three forest soils. Soil DON+MBN were highest for Q. liaotungensis, lowest for P. tabulaeformis Carr. and R. pseudoacacia, and there were no significant differences between P. tabulaeformis Carr. and R. pseudoacacia. Soil DON+MBN was lowest for B. orientalis in the 5-20 cm soil layer. The ratio of MBC to MBN (MBC/MBN) ranged from 4 to 8, the ratio of MBN to total nitrogen (TN) (MBN/TN) ranged from 3.21% to 5.03% and the ratio of MBC to the total organic carbon (SOC) (MBC/SOC) ranged from 2.02 to 3.29%. MBC and MBN were correlated or significantly correlated with MBC/MBN, DOC, DON, DOC+MBC, DON+MBN, TN and SOC. MBC was significantly correlated with MBN. DOC+MBC better reflected soil available carbon than MBC and DOC alone, and similarly DON+MBN better reflected soil available nitrogen. Different forests have a significant influence on the microbial biomass and water dissolved carbon and nitrogen. Q. liaotungensis and B. orientalis had much greater effects on the soil organic carbon and soil nitrogen content, which could improve the soil quality. R. pseudoacacia is a native species in this region, and this species had lower effects on the contents of soil carbon and nitrogen. For the process of vegetation restoration in the Loess Plateau, Q. liaotungensis and B. orientalis were more suitable forest species than R. pseudoacacia. 参考文献 相似文献 引证文献

A study of subsurface wastewater infiltration systems for distributed rural sewage treatment

Three types of subsurface wastewater infiltration systems (SWIS) were developed to study the efficiency of organic pollutant removal from distributed rural sewage under various conditions. Of the three different layered substrate systems, the one with the greatest amount of decomposed cow dung (5%) and soil (DCDS) showed the highest removal efficiency with respect to total nitrogen (TN), where the others showed no significant difference. The TN removal efficiency was increased with an increasing filling height of DCDS. Compared with the TN removal efficiency of 25% in the system without DCDS, the removal efficiency of the systems in which DCDS filled half and one fourth of the height was increased by 72% and 31%, respectively. Based on seasonal variations in the discharge of the typical rural family, the SWIS were run at three different hydraulic loads of 6.5, 13 and 20 cm/d. These results illustrated that SWIS could perform well at any of the given hydraulic loads. The results of trials using different inlet configurations showed that the effluent concentration of the contaminants in the system operating a multiple-inlet mode was much lower compared with the system operated under single-inlet conditions. The effluent concentration of a pilot-scale plant achieved the level III criteria specified by the Surface Water Quality Standard at the initial stage.

Distribution of nutrients, heavy metals, and PAHs affected by sediment dredging in the Wujin'gang River basin flowing into Meiliang Bay of Lake Taihu

This paper's survey of the pollution of the Wujin'gang River is important because it is one of the main rivers flowing into Meiliang Bay of Lake Taihu in eastern China. Trace metals (TMs) in this paper are described according to their pollution index (P i). Cluster analysis and correlation analysis are utilized for group sites and to assess co-contamination. Toxicity effect analysis was conducted using individual sediment quality guideline quotients (SQGQs) and mean SQGQs. The results showed that sediment from the Wujin'gang River basin was affected by nutrients, heavy metals, and polycyclic aromatic hydrocarbons (PAHs), which are an essential contamination source for both Meiliang Bay and Zhushan Bay of Lake Taihu. The discharge of TMs has significant correlations to total nitrogen (TN) and total phosphorus (TP); however, no significant correlations were observed between the content of PAHs and TMs. Toxicity effect results show that sediment in the Wujin'gang River basin threatens sediment-dwelling organisms. The harmful effect was mainly caused by heavy metals especially Cd, Cr, Ni, and Cu. Sediment dredging is an effective way to control pollution from internal rivers especially for the pollution of TN and heavy metals in the Wujin'gang River basin.

A field study on seed bank and its potential applications in vegetation restoration of a polluted urban river in China

As an important component of restorations of polluted and/or degraded rivers, vegetation recovery has become a research highlight in the last two decades. Seed bank have been used as the best tool to allow natural recolonization of indigenous plants probably occurring before the degradation of the water bodies. To illustrate the relationship between water pollution and distribution of seed bank and evaluate the potential application of seed bank in vegetation restoration of polluted rivers, an urban river, Nanfeihe River was selected as the investigation target. A total of 27 species from 17 families with dominant families of Poaceae (5 species) and Polygonaceae (4 species) were identified in 38 channel bed samples. The observed species included 4 aquatic, 7 wetland and 16 terrestrial species, which occupied 15%, 26% and 59% of the total species, respectively. The species richness at the 10 sampling sites varied from 7 to 19, and the seed densities varied from 804 to 1.48×104seedlingsm−2. Species richness and seed density in the river margin were significantly higher than those in the mid-channel (P<0.05), and those in upper sediment layers were also higher than those in sub-layers. The species richness and Shannon Index of seed bank were significantly related to total nitrogen (TN) concentration in the sediment by Gauss regression (R2=0.94, P<0.001 and R2=0.91, P<0.001). Increasing TN concentrations in sediment eventually led to the decline of species richness and diversity. CCA ordination suggested that water depth and NH4+–N concentration in water column played an important role in shaping the pattern of seed bank in the river. Perhaps water pollution not only caused degradation or even disappearance of standing vegetations, but also influenced the storage and distribution of seed bank. In addition, nitrogen-loading gradient along the river was probably capable of determining the pattern of seed bank at certain extend. The quantitative relations between the pattern of seed bank and water pollution give us insight to evaluate the potential application of seed bank in vegetation recovery in polluted urban rivers, and it would also contribute to urban riverine management, diversity conservation and ecological assessment.

Stream Nitrogen Sources Apportionment and Pollution Control Scheme Development in an Agricultural Watershed in Eastern China

A modeling system that couples a land-usebased export coefficient model, a stream nutrient transport equation, and Bayesian statistics was developed for stream nitrogen source apportionment. It divides a watershed into several sub-catchments, and then considers the major landuse categories as stream nitrogen sources in each subcatchment. The runoff depth and stream water depth are considered as the major factors influencing delivery of nitrogen from land to downstream stream node within each sub-catchment. The nitrogen sources and delivery processes are lumped into several constant parameters that were calibrated using Bayesian statistics from commonly available stream monitoring and land-use datasets. This modeling system was successfully applied to total nitrogen (TN) pollution control scheme development for the ChangLe River watershed containing six sub-catchments and four land-use categories. The temporal (across months and years) and spatial (across sub-catchments and land-use categories) variability of nonpoint source (NPS) TN export to stream channels and delivery to the watershed outlet were assessed. After adjustment for in-stream TNretention, the time periods and watershed areas with disproportionately high-TN contributions to the stream were identified. Aimed at a target stream TN level of 2 mg L-1, a quantitative TN pollution control scheme was further developed to determine which sub-catchments, which land-use categories in a sub-catchment, which time periods, and how large of NPS TN export reduction were required. This modeling system provides a powerful tool for stream nitrogen source apportionment and pollution control scheme development at the watershed scale and has only limited data requirements.

Exploring estuarine eutrophication sensitivity to nutrient loading

The sensitivity of surface chlorophyll (Chl) and bottom water dissolved oxygen (DO) to total nitrogen (TN) load was investigated using a Bayesian‐based process model fit to data from a range of estuaries. The model was used to test if the sensitivity of DO depletion to TN loads is dependent only on factors controlling the sensitivity of surface Chl, or if additional factors are important. Results indicate that separate processes control Chl and DO sensitivity, and that these sensitivities vary among estuaries. Analysis of fitted parameters across estuaries showed that Chl sensitivity to TN loading was positively correlated with water residence time, and DO sensitivity to Chl was positively correlated with relative mixing depth.

Pretreatment methods for aquatic plant biomass as carbon sources for potential use in treating eutrophic water in subsurface-flow constructed wetlands

Plant biomass is usually added to constructed wetlands (CW) to enhance denitrification. In this study, we investigated effects of different pretreatments on two common external plant carbon sources, cattail and reed litter. We determined the average ratio of chemical oxygen demand (COD) to total nitrogen (TN), designated as C/N, in water samples after addition of litter subjected to various pretreatments. The C/N in the water samples ranged from 4.8 to 6.4 after addition of NaOH-pretreated cattail litter, which was four to six times greater than that of water from the Yapu River and 3.84-39.15% higher than that of systems that received untreated cattail litter. The C/N of systems that received H(2)SO(4)-pretreated carbon sources varied from 1.7 to 3.6. These two methods resulted in TN and total phosphorus (TP) levels lower than those in river water. The C/N was 1.4-1.7 after addition of CH(3)COOH-pretreated reed litter, which was 34.87-53.83% higher than that of river water. The C/N was 2.5 in systems that received mild alkali/oxidation-pretreated reeds, which was 30.59% higher than that of systems that received non-pretreated reeds. The residue rates of cattail and reed litter subjected to various pretreatments were greater than 60%. Our results showed that NaOH, H(2)SO(4), and mild alkali/oxidation pretreatments were useful to rapidly improve the C/N of river water and enhance denitrification.

Purification Effect of &lt;i&gt;Lolium multiflorum&lt;/i&gt; Ecological Floating Beds System in Urban Malodorous River at Low Temperature

An ecological floating beds system was constructed to treat natural urban malodorous river in Changzhou at low temperature. Taking Lolium multiflorum as an example of water plant, the characteristics and contribution of its uptake to total nitrogen (TN), NH4+-N, total phosphorus (TP) and chemical oxygen demand (CODMn) in the system were studied in a period of 80 days. Significant growth of the plant Lolium multiflorum was observed with total biomass ranging from 53 g to 785 g, and the highest growth rates were 8.82 and 9.23 for biomass of above water and under water part, respectively. Different concentrations of TN, NH4+-N, TP and COD were found between in the floating beds and out the floating beds. The highest removal rates of TN, NH4+-N, TP and CODMn using Lolium multiflorum ecological floating beds system were 16.8%, 33.0%,10.8% and 17.8%, respectively. The purification effect of ecological floating beds shows it can be well applied to cleaning natural rivers at low temperatures.

Effect of Drought Conditions on Plankton Community and on Nutrient Availability in an Oligotrophic High Mountain Lake

Natural water level fluctuations (WLFs) are an inherent characteristic of Mediterranean inland waters, which are projected to be amplified by global climate change. La Caldera (Sierra Nevada National Park, Spain) is an oligotrophic high mountain lake (3050 m a.s.l.) that has experienced large fluctuations in water volume (13–100%) during the past 20 years due to irregular annual precipitation patterns (371–1816 mm). Because of the lake’s cold and dilute abiotic environment, it is likely susceptible to projected increases in global temperature and represents an ideal sentinel of global change. We analyze the effect of WLFs on water quality and on plankton community in La Caldera to better understand the potential effects of recurrent droughts (3 droughts in a 20-year period) on lake ecology. We have found significantly positive effects of WLFs on total phosphorus (TP) concentrations. There was extreme variability in TP concentrations during three recurrent droughts (1995, 1999, and 2005) reflecting sediment resuspension. However, the data also suggest that this was not the only source of phosphorus. Extremely high P-enriched atmospheric dust inputs could have maintained the abnormally high TP in-lake concentrations measured during 2005. The data indicate that recurrent droughts have reduced lake resistance to TP changes but have increased lake resistance to total nitrogen (TN) changes, which supports the idea that a P-enriched atmospheric dust inputs during 2005. An increase in dissolved inorganic nitrogen (DIN)∶TP mass ratio after 2005 was observed, revealing a higher ecosystem homeostasis of this ratio.

APPLICATION OF ARTIFICIAL NEURAL NETWORK TO PREDICTION OF CANTONESE SOY SAUCE BREWING AND CHANGING PATTERN CONCERNING TOTAL NITROGEN AND α‐AMINO ACID NITROGEN

ABSTRACTIn the present study, the artificial neural network was used to predict the brewing of traditional Cantonese soy sauce and its changing pattern with regard to total nitrogen (TN) andα‐amino acidic nitrogen (AN). The effects of parameters during brewing on the contents of TN and AN were modeled by various networks. After the 7‐40‐2 network was determined statistically, it was used to extract the possible correlations between TN and AN, and the relative significance of some factors. It was found that the change of TN and AN contents with the change of time and acidic protease activity was strongly correlated with an R value of 0.9848 and 0.9916, respectively. As for the relative significances of inputs, aging time is the key factor for both outputs during the moromi aging. And for other inputs, it was temperature &gt; pH &gt; neutral protease activity &gt; acid protease activity for TN, and temperature &gt; acidic protease activity &gt; neutral protease activity &gt; pH for AN, respectively.PRACTICAL APPLICATIONSBecause of its open‐air brewing and lengthy brewing time of Cantonese soy sauce, it was difficult to predict its quality indices, the contents of total nitrogen and α‐amino acidic nitrogen, which would change with outside factors (time and temperature) and inside factors (protease activity and pH values). So the study on brewing‐state predication and changing pattern of quality indices were performed by using the artificial neural network on an experimental scale. And results from this preliminary study would help manufacturers to foresee the change and contents of quality indices accurately in the brewing process on an industrial scale. Furthermore, it was anticipated that more effective control and improvement on the quality of traditional Cantonese would be achieved in the future study. Finally, the trained network also can be used in the research of online prediction for other time‐consuming natural fermentation.