To Total Phosphorus Research Articles

Does nutrient enrichment alleviate stoichiometric constraint on plankton trophic structure?

AbstractStoichiometric mismatch between phytoplankton and zooplankton has implication for trophic transfer efficiency. Phosphorus (P) enrichment is expected to lower phytoplankton carbon (C) to P ratio (C : P) and thereby either alleviate P deficiency or induce excess P for zooplankton. However, the generality of zooplankton facing excess P and its effect on plankton trophic structure in natural systems are poorly understood. We analyzed the stoichiometry of seston and zooplankton, and plankton trophic structure in 32 (sub)tropical Chinese reservoirs. Our results showed that (1) stoichiometric mismatch between seston and zooplankton involved P or/and nitrogen (N) deficits in low‐nutrient reservoirs and P excess in high‐nutrient reservoirs; (2) at given seston C and phytoplankton compositional food quality levels, zooplankton to phytoplankton biomass ratio (Zoo : Phyto) showed a two‐segment piecewise relationship to seston N : P with a maximum at a breakpoint of 12.6 and strong reductions toward the extremes of seston N : P gradient; (3) increasing stoichiometric mismatch between seston and consumers reduced the contribution of cladocerans to zooplankton biomass and increased the trophic position of copepods; and (4) chlorophyll a (Chl a) to total phosphorus (TP) ratio (Chl a : TP) increased with decreasing Zoo : Phyto, and at a given Zoo : Phyto, it was higher in reservoirs with zooplankton dominated by copepods than in reservoirs with zooplankton dominated by cladocerans. These findings suggest that nutrient enrichment might improve stoichiometric constraint on plankton trophic structure in low‐nutrient reservoirs, but enhance negative effect of excess P in high‐nutrient reservoirs. Thus, negative impact of excess P on zooplankton may be a mechanism partly contributing to low Zoo : Phyto and high Chl a : TP in eutrophic reservoirs.

Airport Deicers: An Unrecognized Source of Phosphorus Loading in Receiving Waters.

Airport ice control products contributed to total phosphorus (TP) loadings in a study of surface water runoff at a medium-sized airport from 2015 to 2021. Eleven airport ice control products had TP concentrations from 1-807 mg L-1 in liquid formulas, while solid pavement deicer had a TP concentration of 805 mg kg-1. Product application data, formula TP concentrations, and surface water sampling results were used to estimate TP concentration and loading contributions from these ice control products to receiving streams. Airport ice control products were found to contribute to TP in 84% of the water samples collected at downstream sites during deicing events, and TP concentrations at those sites exceeded aquatic life benchmarks in 70% of samples collected during deicing. A receiving stream 6 km downstream had TP attributed to airport ice control sources in 78% of the samples. TP loadings at an upstream site and the receiving stream site were greatest during the largest runoff events as is typical in urban runoff, but this pattern was not always followed at airport outfall sites due to the influence of TP in deicer products. Products analyzed in this study are used at airports across the United States and abroad, and findings suggest that airport deicers could represent a previously unrecognized source of phosphorus to adjacent waterways.

Microplastic pollution in the offshore sea, rivers and wastewater treatment plants in Jiangsu coastal area in China

Offshore areas are particularly important in recognizing microplastics pollution because they are sinks of land imports and sources of ocean microplastics. This study investigated the pollution and distribution of microplastics in the offshore Sea, rivers and wastewater treatment plants (WWTPs) in Jiangsu coastal area in China. Results showed that microplastics were widely present in the offshore area, with an average abundance of 3.1–3.5 items/m3. Significantly higher abundance was present in rivers (3.7–5.9 item/m3), municipal WWTPs (13.7 ± 0.5 item/m3), and industrial WWTPs (19.7 ± 1.2 item/m3). The proportion of small-sized microplastics (1–3 mm) increased from WWTPs (53%) to rivers (64%) and the offshore area (53%). Polyamide (PA), polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), and rayon (RA) were dominant types of microplastics. Both living and industrial sources contributed to the prevalent microplastics in the offshore Sea. Redundancy analysis showed that small-sized microplastics (1–3 mm) were positively correlated to total phosphorus (TP), while large-sized microplastics (3–5 mm) were positively correlated to TP and NH3–N. The abundance of PE, PP and PVC microplastics were positively correlated to TP and total nitrogen (TN), thus nutrients could be indicators of microplastics pollution in the offshore area.

The influence of nutrients on the composition and quantity of buried organic carbon in a eutrophic plateau lake, Southwest China.

The regulation of lacustrine organic carbon (OC) burial by nutrient is an outstanding knowledge gap in the current understanding of lake carbon cycles. In this study, we determined how nutrients quantitatively correspond with OC burial using the parallel factor analysis (PARAFAC) method in Dianchi Lake, southwest China. Factors were classified into three types according to their historical sedimentation characteristics: the background factor (BF), response factor (RF), and contingency factor (CF). The BF represented the original OC input combination in the lake and was insensitive to nutrient changes. The RF represented the OC input combination that was induced or promoted by nutrient changes in the lake. The CF represented short-term discontinuous factors in sedimentary history, which may be related to unique historical events. The results indicate that changes in the total nitrogen (TN) to total phosphorus (TP) ratio correlated with changes in the BF contribution; whereas the quantity of OC was mainly correlated with TN. The >90% of OC buried in sediment was quantitatively simulated by BF and RF; the driving effect of RF on OC burial was approximately 13 times higher than that of BF. It was observed that a 1 mg kg-1 increase in TN led to approximately 2.2 units increase in RF contribution in Dianchi Lake, while the BF was insensitive to changes in TN. Thus, changes in lake nutrients may effectively change the composition and quantity of OC buried in lake sediment.

Effects of Environmental Concentrations of Total Phosphorus on the Plankton Community Structure and Function in a Microcosm Study.

The excessive nutrients in freshwater have been proven to promote eutrophication and harmful algae blooms, which have become great threats to water quality and human health. To elucidate the responses of the plankton community structure and function to total phosphorus (TP) at environmental concentrations in the freshwater ecosystem, a microcosm study was implemented. The results showed that plankton communities were significantly affected by the TP concentration ≥ 0.1 mg/L treatments. In terms of community structure, TP promoted the growth of Cyanophyta. This effect was transmitted to the zooplankton community, resulting in the promotion of Cladocera growth from day 42. The community diversities of phytoplankton and zooplankton had been continuously inhibited by TP. The principal response curve (PRC) analysis results demonstrated that the species composition of phytoplankton and zooplankton community in TP enrichment treatments significantly (p ≤ 0.05) deviated from the control. For community function, TP resulted in the decline in phytoplankton photosynthesis. The chlorophyll fluorescence parameters were significantly inhibited when TP concentration reached 0.4 mg/L. In TP ≥ 0.1 mg/L treatments, the reductions in total phytoplankton abundances led to a continuous decrease in pH. This study can directly prove that the plankton community changes significantly when TP concentrations are greater than 0.1 mg/L and can help managers to establish specific nutrient management strategies for surface water.

The Light-to-Nutrient Ratio in Alpine Lakes: Different Scenarios of Bacterial Nutrient Limitation and Community Structure in Lakes Above and Below the Treeline.

The light-to-nutrient hypothesis proposes that under high light-to-nutrient conditions, bacteria tend to be limited by phosphorus (P), while under relatively low light-to-nutrient conditions, bacteria are likely driven towards carbon (C) limitation. Exploring whether this light-to-nutrient hypothesis is fitting for alpine lakes has profound implications for predicting the impacts of climatic and environmental changes on the structures and processes of aquatic ecosystems in climate-sensitive regions. We investigated the environmental conditions and bacterioplankton community compositions of 15 high-elevation lakes (7 above and 8 below treeline). High light-to-nutrient conditions (denoted by the reciprocal value of the attenuation coefficient (1/K) to total phosphorus (TP)), high chlorophyll a (Chl a) concentrations, low TP concentrations and low ratios of the dissolved organic carbon concentration to the dissolved total nitrogen concentration (DOC:DTN) were detected in above-treeline lakes. Significant positive correlations between the bacterioplankton community compositions with 1/K:TP ratios and Chl a concentrations indicated that not only high light energy but also nutrient competition between phytoplankton and bacteria could induce P limitation for bacteria. In contrast, low light-to-nutrient conditions and high allochthonous DOC input in below-treeline lakes lessen P limitation and C limitation. The most abundant genus, Polynucleobacter, was significantly enriched, and more diverse oligotypes of Polynucleobacter operational taxonomic units were identified in the below-treeline lakes, indicating the divergence of niche adaptations among Polynucleobacter oligotypes. The discrepancies in the light-to-P ratio and the components of organic matter between the above-treeline and below-treeline lakes have important implications for the nutrient limitation of bacterioplankton and their community compositions.

Integrating ecosystem metabolism and consumer allochthony reveals nonlinear drivers in lake organic matter processing

AbstractLakes process both terrestrial and aquatic organic matter, and the relative contribution from each source is often measured via ecosystem metabolism and terrestrial resource use in the food web (i.e., consumer allochthony). Yet, ecosystem metabolism and consumer allochthony are rarely considered together, despite possible interactions and potential for them to respond to the same lake characteristics. In this study, we compiled global datasets of lake gross primary production (GPP), ecosystem respiration (ER), and zooplankton allochthony to compare the strength and shape of relationships with physicochemical characteristics across a broad set of lakes. GPP was positively related to total phosphorus (TP) in lakes with intermediate TP concentrations (11–75 μg L−1) and was highest in lakes with intermediate dissolved organic carbon (DOC) concentrations. While ER and GPP were strongly positively correlated, decoupling occurred at high DOC concentrations. Lastly, allochthony had a unimodal relationship with TP and related variably to DOC. By integrating metabolism and allochthony, we identified similar change points in GPP and zooplankton allochthony at intermediate DOC (4.5–10 mg L−1) and TP (8–20 μg L−1) concentrations, indicating that allochthony and GPP may be coupled and inversely related. The ratio of DOC:nutrients also helped to identify conditions where lake organic matter processing responded more to autochthonous or allochthonous organic matter sources. As lakes globally face eutrophication and browning, predicting how lake organic matter processing will respond requires an updated paradigm that incorporates nonlinear dynamics and interactions.

Succession of phytoplankton in a shallow lake under the alternating influence of runoff and reverse water transfer

Abstract Both runoff and water diversion can interfere with the physical and chemical environment of a lake and affect aquatic organisms. In this study, previously obtained data were used to analyze the phytoplankton community, water quality, water level, and temperature in Dongping Lake (DPH) before, during, and after the water diversion caused by the South-to-North Water Transfer Project. The results showed that the total density and diversity index of phytoplankton decreased in the water transfer period, and was related to low temperature. Temperature also affected the recovery of phytoplankton community structure when the water transfer period ended. In a water transfer cycle, changes in dominant genera were more drastic than that of a whole phytoplankton community, and dominant genera were sensitive to total phosphorus (TP) and total nitrogen (TN) changes. Water transfer alleviated the deterioration of water quality in DPH, but water transfer process increased the risk of water pollution. Runoff from Dawen River carried TN, TP, and chemical oxygen demand (COD) into DPH in the rainy season, which indirectly affected phytoplankton, while it also carried phytoplankton directly into DPH. Overall, these findings provide a clear understanding of the impact of water transfer projects on ecology in shallow lakes.

Spatio-temporal impacts of meteorological and geographic factors on the availability of nitrogen and phosphorus to algae in Chinese lakes

Designing effective management strategies for lake ecosystems requires an understanding of regional differences, interannual variability, and other drivers affecting the availability of nutrients to algae. In this study, generalized additive models (GAMs) based on meteorological factors and geographic location were developed to quantitatively estimate the availability of nutrients to algae (as represented by the ratio of Chlorophyll a (Chl a) to total phosphorus (TP) or total nitrogen (TN)) across 167 Chinese freshwater lakes and reservoirs. This model was then used to produce the first spatial and temporal estimates of Chl a/TP and Chl a/TN within mainland China from 1987 to 2016. The results revealed high spatial variability driven primarily by geographic location, which explained 58.86% of the observed variability in Chl a/TP (41.98% in Chl a/TN). In addition, high interannual variability was driven by annual average temperature for both Chl a/TP and Chl a/TN. These results point to a fundamental challenge in managing regions with high nutrient levels, because these regions also tend to exhibit the strongest interannual variability, such that the impact of changes in management practices will be modulated by meteorological variability. In addition, this study provides regionalization indicators that serve as a quantitative foundation for formulating nutrient ecoregions to better administer lakes and reservoirs in China. It is therefore imperative that models combining meteorological factors with geographic location are further developed to improve the simulation of spatio-temporal variability in the availability of nutrients to algae.

Preferential regeneration of P relative to C in a freshwater lake

Particulate organic matter (POM) is the main carrier of carbon (C), nitrogen (N), and phosphorus (P) in the biogeochemical cycle. Previous investigations have found that the regeneration of C, N, and P is obviously different during the degradation of POM in marine environments. However, little attention has been paid to lake system thus far. In an initial attempt to characterize the regeneration behaviors of C and P in lake system, contents of C, N, and P in suspended particulate matter (SPM) and surface sediments of Hongfeng Lake were systematically investigated in this study. The results showed that the total organic carbon (TOC) to total phosphorus (TP) ratios (TOC/P) were obviously lower in SPM than in surface sediments, which demonstrated the preferential regeneration of P relative to C in lake system for the first time. Possible mechanisms for such include reductive dissolution of Fe oxyhydroxide and poly-P remineralization under hypoxic/anoxic conditions.Based on the difference in the TOC/P ratios between SPM and surface sediments, about 25.1 t P was estimated to be released annually from settling seston and sediments in Hongfeng Lake, which is much higher than the previous results on the P release flux from sediment. This indicates that a significant percentage of P may be regenerated during particulate matter transport in the water column, providing new insight into the P regeneration in lake system. The preferential regeneration of P may result in a positive feedback loop among bottom water anoxia, enhanced P regeneration, and algal bloom in sub-deep lakes.

不同林龄油茶人工林土壤酶化学计量及其影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 不同林龄油茶人工林土壤酶化学计量及其影响因素 DOI: 10.5846/stxb201809202059 作者: 作者单位: 中国科学院亚热带农业生态研究所,邵阳县林业局,邵阳县林业局,中国科学院亚热带农业生态研究所,中国科学院亚热带农业生态研究所,中国科学院亚热带农业生态研究所,中国科学院亚热带农业生态研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划（2017YFC0505500，2017YFC0505503）；国家自然科学基金项目（41601260） Patterns of soil ecoenzymatic stoichiometry and its influencing factors during stand development in Camellia oleifera plantations Author: Affiliation: Institute of Subtropical Agriculture, Chinese Academy of Sciences,,,,,,Institute of Subtropical Agriculture, Chinese Academy of Sciences 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:土壤酶化学计量比是揭示微生物生长代谢过程及评价土壤养分资源限制状况的重要指标。油茶是中国南方主要的木本油料作物，近年来愈来愈受关注，但鲜有从生态化学计量学的角度深入理解人工经济林的土壤微生物养分限制状况。本文以亚热带地区不同林龄油茶人工林土壤为研究对象，采用时空互代法在区域尺度上随机选取32个不同林龄油茶人工林并将其分为四个林龄组（ < 9年幼龄林；9-20年近熟林；21-60年成熟林； > 60年过熟林），通过测定土壤碳（C）、氮（N）、磷（P）转化酶活性（β-葡糖苷酶（BG）、α-纤维素酶（CBH）、β-乙酰葡糖胺糖苷酶（NAG）、亮氨酸氨基肽酶（LAP）、酸性磷酸酶（AP））及土壤理化因子，探讨不同林龄油茶人工林土壤C、N、P转化酶化学计量特征及其与土壤理化因子的关系。结果表明：五种C、N、P转化酶活性均有随林龄增大而增加的趋势，且AP活性显著高于其它四种酶活性。相关分析结果表明，五种土壤C、N、P转化酶活性均与土壤有机碳和总氮显著相关，与土壤总磷和速效磷含量不相关。土壤酶化学计量比ln（CBH+BG）：ln（NAG+LAP）、ln（CBH+BG）：ln（AP）和ln（NAG+LAP）：ln（AP）均随林龄增大而一定程度增加。亚热带区油茶人工林土壤酶C：N：P化学计量比为1：1：1.5，这与全球生态系统土壤酶C：N：P化学计量比1：1：1相偏离，表明亚热带地区油茶人工林土壤微生物生长受磷素限制。冗余分析（RDA）进一步揭示土壤有机碳含量是影响土壤酶活性和酶化学计量比的主要因子。因此，在油茶人工林经营管理中应考虑磷和外源碳的投入，提高土壤微生物酶活性，缓解油茶人工林生态系统的磷限制。研究结果可为亚热带区油茶人工林土壤养分管理和可持续利用提供基础理论支撑。 Abstract:The stoichiometry of soil enzymatic activity is a key indicator to predict microbial growth and metabolism and can be used to evaluate soil nutrient limitation. Camellia oleifera, the main economically important woody oil-producing plant in southern China, has received much attention recently; however, little is known about the soil ecoenzymatic stoichiometry and microbial resource limitation in C. oleifera plantations. In this study, to understand soil nutrient limitations in C. oleifera plantations in the subtropical region of China, we collected 96 soil samples from 32 sample site plantations with varying levels of C. oleifera stand development and analyzed the soils' enzymatic activities. Plantation with four different C. oleifera stand ages were chosen: < 9 years, 9-20 years, 21-60 years, and > 60 years. We examined the activities of 1,4-β-glucosidase (BG), α-cellulases (CBH), leucine aminopeptidase (LAP), 1,4-β-N-acetylglucosaminidase (NAG), and alkaline phosphatases (AP), as well as soil physicochemical parameters. We analyzed the stoichiometric characteristics of the enzymes and the relationships between the soils' physicochemical properties and ecoenzymatic stoichiometry. The results indicate that all soil enzyme activities increased with increasing stand age in the early stage, and then the activity of those enzymes stabilized. In addition, AP activity was greater than those of BG, CBH, NAG, and LAP. According to a correlation analysis, all soil enzyme activities were positively correlated with soil organic carbon (SOC) and total nitrogen (TN) content but were not correlated to total phosphorus (TP) or Olsen phosphorous (P) content. The ratios of ln(CBH+BG):ln(NAG+LAP), ln(CBH+BG):ln(AP), and ln(NAG+LAP):ln(AP) showed a similar pattern of increase with stand age. The soil ecoenzymatic C:N:P stoichiometry in our C. oleifera plantations was 1:1:1.5, which was inconsistent with the 1:1:1 global pattern of C:N:P stoichiometry. This result suggests that C. oleifera plantations in the subtropical region of China were limited by phosphorus. A canonical redundancy analysis (RDA) indicated that SOC was the dominant factor affecting soil enzymatic activity and ecoenzymatic stoichiometry. Additionally, TP and pH were selected by the RDA model as the significant environmental factors influencing soil ecoenzymatic stoichiometry. Our results suggest that carbon and phosphorus adjustments could be an important strategy to improve soil enzymatic activities and alleviate the phosphorus limitation of C. oleifera plantations. Our study provides solid data to support nutrient management and the sustainable management of C. oleifera plantations in the subtropical region of China. 参考文献 相似文献 引证文献

Impact of an Extreme Storm Event on River Corridor Bank Erosion and Phosphorus Mobilization in a Mountainous Watershed in the Northeastern United States

AbstractMovement of sediment, and associated phosphorus, from stream banks to freshwater lakes is predicted to increase with greater frequency of extreme precipitation events. This higher phosphorus load may accelerate harmful algal blooms in affected water bodies, such as Lake Champlain in Vermont, New York, and Québec. In the Mad River, a subwatershed in central Vermont's Lake Champlain Basin, extreme flooding from Tropical Storm Irene in 2011 caused extensive erosion. We measured stream channel change along the main stem between 2008 and 2011 by digitizing available prestorm and poststorm aerial imagery. Soils were sampled post Irene at six active stream erosion sites, using an experimental design to measure differences in soil texture and phosphorus both with depth (90 cm) and distance from the stream. In addition to total phosphorus (TP), we determined bioavailable (soil test) phosphorus (STP) and the degree of phosphorus saturation (DPS). The six sites represented a 0.87‐km length of stream bank that contributed an estimated 17.6 × 103 Mg of sediment and 15.8 Mg of TP, roughly the same as average annual watershed export estimates. At four sites, the STP and DPS were low and suggested little potential for short‐term phosphorus release. At two agricultural sites where the lateral extent of erosion was high, imagery showed a clear loss of well‐established riparian buffer. Present‐day near‐stream soils were elevated in STP and DPS. An increase in these extreme events will clearly increase sediment loads. There will also be increasing concentration of sediment phosphorus if stream banks continue to erode into actively managed agricultural fields.

Colorimetric Chemical Differentiation and Detection of Phosphorus in Eutrophic and High Particulate Waters: Advantages of a New Monitoring Approach

Phosphorus (P) is a key factor forcing eutrophication in limnic and marine systems, and all monitoring programs for water quality accordingly include P determinations. However, traditional monitoring does not allow an analysis of the different components involved in the P cycle taking place in the water column. Nonetheless, the implementation of measures addressing eutrophication requires a full understanding of the processes involved in the transformation and transport of P, in all its chemical forms. In this study, the P categories present in a river and its estuary in northern Germany, which discharge into the Baltic Sea, were characterized. Using the molybdenum blue method we found that the classification of P into the traditional fractions (DIP, DOP, POP) applied in the ocean cannot be applied to turbid waters such as rivers because interferences between the fractions seems to occur. Therefore a new nomenclature has been introduced. In addition to total phosphorus (TP) and dissolved molybdate-reactive phosphorus (DRP; previously referred to as inorganic phosphorus), dissolved non-molybdate-reactive phosphorus (DNP), particulate molybdatereactive phosphorus (PRP), and particulate non-molybdate-reactive phosphorus (PNP) were distinguished. The high spatial and temporal variations in the proportions of these forms with respect to the TP concentration well demonstrate the complexity of the P cycle and the involved P fractions and emphasize the need for expanded monitoring approach. The potential of eutrophication could be underestimated if not all P categories were considered. With the new operational nomenclature the common and standardized molybdenum blue reaction could be used to implement the analysis of various P components into regular monitoring programs.

Spatial and Temporal Variations of Water Quality and Trophic Status in Sembrong Reservoir, Johor

A study of spatial and temporal variations on water quality and trophic status was conducted to determine the temporal (average reading by month) and spatial variations of water quality in Sembrong reservoir and to evaluate the trophic status of the reservoir. Water samples were collected once a month from November 2016 to June 2017 in seventeen (17) sampling stations at Sembrong Reservoir. Results obtained on the concentration of dissolved oxygen (DO), water temperature, pH and secchi depth had no significant differences compared to Total Phosphorus (TP) and chlorophyll-a. The water level has significantly decreased the value of the water temperature, pH and TP. The water quality of Sembrong reservoir is classified in Class II which is suitable for recreational uses and required conventional treatment while TSI indicates that sembrong reservoir was in lower boundary of classical eutrophic (TSI &gt; 50).

Factors controlling the three-decade long rise in cyanobacteria biomass in a eutrophic shallow lake

We aimed at quantifying the importance of limnological variables in the decadal rise of cyanobacteria biomass in shallow hemiboreal lakes. We constructed estimates of cyanobacteria (blue-green algae) biomass in a large, eutrophic lake (Estonia, Northeastern Europe) from a database comprising 28 limnological variables and spanning more than 50years of monitoring. Using a dual-model approach consisting in a boosted regression trees (BRT) followed by a generalized least squares (GLS) model, our results revealed that six variables were most influential for assessing the variance of cyanobacteria biomass. Cyanobacteria response to nitrate concentration and rotifer abundance was negative, whereas it was positive to pH, temperature, cladoceran and copepod biomass. Response to total phosphorus (TP) and total phosphorus to total nitrogen ratio was very weak, which suggests that actual in-lake TP concentration is still above limiting values. The most efficient GLS model, which explained nearly two thirds (r2=0.65) of the variance of cyanobacteria biomass included nitrate concentration, water temperature and pH. The very high number of observations (maximum n=525) supports the robustness of the models. Our results suggest that the decadal rise of blue-green algae in shallow lakes lies in the interaction between cultural eutrophication and global warming which bring in-lake physical and chemical conditions closer to cyanobacteria optima.

Importance of the ratios of the forms of nutrients for assessment of the modern state of Rybinsk Reservoir

Various ratios of nutrient forms have been analyzed on the basis of the materials collected in Rybinsk Reservoir in the years 2001 to 2011. The analysis was used for assessment of the modern state of the reservoir. The total nitrogen (TN) to total phosphorus (TP) ratio is the most informative parameter. During the study period at all sampling stations, the average value of this ratio was 17.0. This value indicates the lack of limitation of development of phytoplankton by these nutrients. High values of the absolute concentration of nitrate nitrogen and its proportion in the total mineral nitrogen (which are important indicators of increasing eutrophication), as well as the percentage of inorganic phosphorus, were revealed in Volzhskii reach and the upper part of Sheksninskii reach of the reservoir. These values indicate the eutrophic state of the above areas of the reservoir.

Potential of hydrolysis of particulate COD in extended anaerobic conditions to enhance biological phosphorous removal.

The effect of anaerobic hydrolysis of particulate COD (pCOD) on biological phosphorous removal in extended anaerobic condition was investigated through (i) sequencing batch reactors (SBR)s with anaerobic hydraulic retention time (HRT) of 0.8, 2, and 4 h; (ii) batch tests using biomass from a full scale biological nutrient removal (BNR) plant; and (iii) activated sludge modeling (BioWin 4.1 simulation). The results from long-term SBRs operation showed that phosphorus removal was correlated to the ratio of filtered COD (FCOD) to total phosphorus (TP) in the influent. Under conditions with low FCOD/TP ratio (average of 20) in the influent, extending anaerobic HRT to 4 h in the presence of pCOD did not significantly improve overall phosphorous removal. During the period with high FCOD/TP ratio (average of 37) in the influent, all SBRs removed phosphorous completely, and the long anaerobic HRT did not have negative effect on overall phosphorous removal. The batch tests also showed that pCOD at different concentration during 4 h test did not affect the rate of anaerobic phosphorus release. The rate of anaerobic hydrolysis of pCOD was significantly low and extending the anaerobic HRT was ineffective. The simulation (BioWin 4.1) of SBRs with low influent FCOD/TP ratio showed that the default kinetics of anaerobic hydrolysis in ASM2d overestimated phosphorous removal in the SBRs (high anaerobic hydrolysis of pCOD). The default anaerobic hydrolysis rate in BioWin 4.1 (ten times lower) could produce similar phosphorous removal to that in the experiment. Results showed that the current kinetics of anaerobic hydrolysis in ASM2d could lead to considerable error in predicting phosphorus removal in processes with extended anaerobic HRT. Biotechnol. Bioeng. 2016;113: 2377-2385. © 2016 Wiley Periodicals, Inc.

Lake‐type‐specific seasonal patterns of nutrient limitation in German lakes, with target nitrogen and phosphorus concentrations for good ecological status

Summary Eutrophication is a global environmental problem that leaves many lakes with impaired ecological status. Human activity has increased the total concentrations of both nitrogen and phosphorus in aquatic systems, but their relative influence on phytoplankton biomass is uncertain. Their action as alternative limiting resources complicates assessment of their relative influence and disagreement may be in part due to seasonal shifts and lake‐type‐specific differences in the prevalence of limitation by nitrogen versus phosphorus. Debate continues as to whether measures to reduce nitrogen would be beneficial in addition to controls placed on phosphorus. We used a piecewise model to test whether total nitrogen (TN) concentrations, in addition to total phosphorus (TP), influence phytoplankton biomass in 369 lowland German lakes. The piecewise model predicts biomass from TN for low N : P ratio lakes, and from TP for high N : P ratio lakes. We tested three N : P mass ratios to divide lakes: dissolved inorganic nitrogen to TP (DIN : TP), DIN to dissolved reactive phosphorus (DIN : DIP) and TN : TP. TN was a better predictor of biomass than TP when either the DIN : TP ratio was below 1.6, DIN : DIP was below 8.4, or TN : TP below 29; predictions were most accurate when using the DIN : TP ratio. To investigate seasonal and lake‐type‐specific patterns of N and P limitation, we used the DIN : TP ratio, together with absolute concentrations of DIN and DIP, to predict the limiting nutrient at each lake in each month of the vegetation period. N limitation was much more common in polymictic than stratified lakes. While a high proportion of both stratified and polymictic lakes were P limited in early spring (60–70%), for polymictic lakes, we found a strong shift from P limitation to N limitation in summer: more than 50% of polymictic lakes were N limited between June and September and only 15–30% were P limited. To obtain lake‐type‐specific nutrient targets we estimated the average TN and TP concentrations at which lakes of different types achieved good ecological status according to EU water framework directive criteria. Stratified lakes achieved good ecological status at concentrations of 400–500 μg L−1 TN or 20–35 μg L−1 TP, while for polymictic lakes values of 500–1000 μg L−1 TN, or 35–75 μg L−1 TP were required. We estimate that nitrogen has an important influence on phytoplankton biovolume, and thus ecological status, for many polymictic lakes in Germany. While there is some uncertainty in the nutrient targets required to achieve good ecological status, this uncertainty is small compared with the range of concentrations currently observed, and lakes with moderate or worse status have concentrations of both TN and TP that are far above these current target estimates.

Fast eutrophication assessment for stormwater wet detention ponds via fuzzy probit regression analysis under uncertainty.

Stormwater wet detention ponds have been a commonly employed best management practice for stormwater management throughout the world for many years. In the past, the trophic state index values have been used to evaluate seasonal changes in water quality and rank lakes within a region or between several regions; yet, to date, there is no similar index for stormwater wet detention ponds. This study aimed to develop a new multivariate trophic state index (MTSI) suitable for conducting a rapid eutrophication assessment of stormwater wet detention ponds under uncertainty with respect to three typical physical and chemical properties. Six stormwater wet detention ponds in Florida were selected for demonstration of the new MTSI with respect to total phosphorus (TP), total nitrogen (TN), and Secchi disk depth (SDD) as cognitive assessment metrics to sense eutrophication potential collectively and inform the environmental impact holistically. Due to the involvement of multiple endogenous variables (i.e., TN, TP, and SDD) for the eutrophication assessment simultaneously under uncertainty, fuzzy synthetic evaluation was applied to first standardize and synchronize the sources of uncertainty in the decision analysis. The ordered probit regression model was then formulated for assessment based on the concept of MTSI with the inputs from the fuzzy synthetic evaluation. It is indicative that the severe eutrophication condition is present during fall, which might be due to frequent heavy summer storm events contributing to high-nutrient inputs in these six ponds.

Effect of COD/TP ratio on biological nutrient removal in A2O and SBR processes coupled with microfiltration and effluent reuse potential

ABSTRACTTwo bench-scale hybrid processes, anaerobic/anoxic/oxic (A2O) reactor and sequencing batch reactor (SBR), each followed by the microfiltration (MF) system, were simultaneously operated to compare their performances on the removal of organics and phosphorus from both synthetic and real wastewater to further explore the potential for effluent reuse. The effects of different influent chemical oxygen demand (COD) to total phosphorus (TP) ratios (27, 50, 80, and 200) were investigated. For both processes, when the influent COD/TP ratio was 200, the effluent quality was satisfactory for some reuse potential. The MF membrane system showed an evident further removal of COD (20–89%) and color (18–60%), especially the removal of suspended solids (SS) and turbidity with the final effluent SS <1 mg/L and turbidity <0.1 NTU. When real wastewater was tested, the effluent quality was adequate and met the standard goals for regional reuse purposes.