Phosphorus Ratio Research Articles

Submarine groundwater-derived inorganic and organic nutrients vs. mariculture discharge and river contributions in a typical mariculture bay

• Fresh SGD carries 7.4-80 % of the total SGD nutrients in a typical mariculture bay. • SGD contributes much more nutrients than river and rivals mariculture wastewater. • SGD-derived organic nutrients are dominant but were typically ignored previously. • China-wide upscaling shows significance of SGD in the whole mariculture areas. Submarine groundwater discharge (SGD) is recognized as one of the most significant pathways for terrestrial nutrient entry into coastal systems. However, SGD-derived nutrient fluxes, particularly organic nutrients, have not yet been considered in the management of mariculture areas. We quantified both saline (12.5 cm day −1 ) and fresh (1.8 cm day −1 ) SGD and related nutrient fluxes using the radium quartet and water mass balance model, respectively, and then reassessed nutrient budgets in a typical mariculture bay. Although fresh SGD accounts for 13 % of the total SGD, it carries 7.4–80.5 % of the total SGD nutrients, suggesting that fresh SGD was an important source of new nutrients with high nitrogen to phosphorus (N/P) ratios (585) into the coastal waters. Based on the rebuilt nutrient budgets, total SGD and mariculture discharge were the two major nutrient sources into the coastal water, providing 2.8–21.2 and 1.9–13.9 times more nutrients than local rivers, respectively. The nutrient speciation results revealed that SGD-derived organic nutrients, which are typically ignored, were dominant (i.e., dissolved inorganic nitrogen and dissolved organic phosphorus through SGD contributed about 22.9 % and 41.5 % of all nutrient resources). Furthermore, China-wide upscaling showed that SGD-derived nutrient fluxes in the mariculture area along the coast of China are comparable those of the rivers in China. Therefore, we suggest that SGD-derived inorganic and organic nutrient fluxes should be incorporated into the ecosystem management of mariculture areas.

The influencing factors of leaf functional traits variation of Pinus densiflora Sieb. et Zucc.

Trait-based approaches have emerged as promising strategies for understanding plant adaptation mechanisms to the changing environment. At present, there are a large number of studies on the relationship between plant leaf functional traits and environment, but these studies mostly use the average value of traits instead of species, ignoring the intraspecific changes of traits. Pinus densiflora Sieb. et Zucc. is not only an urban greening tree species, but also an important afforestation tree species, which plays an important role in China's terrestrial ecosystem. In this study, the leaf nitrogen content (LN), the leaf phosphorus content (LP), nitrogen phosphorus ratio (N/P), leaf area (LA) and specific leaf area (SLA) of 16 sites (160 records) distributed in Chinese P. densiflora were measured. (1) The results showed that LN increased with the increase of mean annual precipitation (MAP) and decreased with the increase of soil organic matter (SOM). LP and SLA decreased with the increase of mean annual temperature (MAT) and increased with the increase of AN (soil available phosphorus) and AP (soil available phosphorus). N/P increased with the increase of MAT and MAP, and decreased with the increase of AN and AP. LA increased with the increase of MAT and MAP. (2) Relative importance analysis showed that MAP was the most important driver of LN and LA. The main driving factors of LP is MAT, the main driving factors of N/P is SOM, and the main influencing factors of SLA is AP. Overall, climate was the main driving factor for the variation of leaf functional traits. The variation law of leaf functional traits along environmental gradient strongly supported the temperature-plant physiological hypothesis. It enriches the understanding of leaf functional traits distribution pattern and its driving mechanism under environmental change.

Origin of dissolved organic carbon under phosphorus-limited coastal-bay conditions revealed by fluorescent dissolved organic matter

To determine the origins of dissolved organic carbon (DOC) in a bay of volcanic Jeju Island, where the discharge of fresh groundwater (FGW) is dominant, we measured fluorescent dissolved organic matter (FDOM) and implemented a parallel factor analysis (PARAFAC). The PARAFAC model identified three humic-like components (FDOMH) and one protein-like component (FDOMP). DOC was extremely deficient in the FGW (35 ± 13 μM) and positively correlated with salinity in the coastal environment, indicating oceanic DOC contribution. The FDOMP pattern was similar to that of DOC, suggesting that marine biological production is a primary DOC source in this region. Particularly, significant FDOMP correlations in the coastal waters with the fluxes of dissolved inorganic phosphorus (DIP; R2 = 0.31) and dissolved silicon (R2 = 0.46) from the FGW demonstrated that in situ biological production is facilitated by FGW-borne nutrient addition. However, the absence of a correlation between the fluxes of dissolved inorganic nitrogen (DIN) and FDOMP (R2 <0.01) indicated that anthropogenic DIN is not essential for DOC production under the P-limited nutrient conditions and diatom-dominant conditions prevailing on the coastal Jeju Island. Here, we calculated the potential capacity of carbon fixation by marine biological activity based on the Redfield ratio of carbon and phosphorus with DIP fluxes. The flux accounts for approximately 2% of the terrestrial carbon uptake in South Korea. Therefore, optical properties of FDOM may be good indicators of coastal DOC origin, and nutrient speciation may be linked to the carbon cycle.

Complex dynamics of twig elements and stoichiometric ratios with altitude changes in the typical dry valley, eastern Qinghai-Tibet plateau

The concentrations of carbon (C), nitrogen (N), phosphorus (P) and stoichiometric ratios of twig (i.e. stem and leaves) are the important indicators to connect plant individual and the abiotic environment, which reflects the nutritional status for plants and ecosystem function. However, the variations of stoichiometric characteristics of twig C, N and P across altitude gradient have not yet been extensively studied. In the present study, we determined the elements (C, N and P) concentrations of current-year twigs from 1050 to 3070 m woody plants in the Bailongjiang River Basin (BRB), a typical dry valley of eastern Qinghai-Tibet plateau. And then, the relationships between altitude and the element concentrations of twigs, stems, and leaves had been explored by linear regression, allometric analysis and phylogenetic analysis. The results showed that: the frequency distribution of elemental concentrations and stoichiometric ratios was left-deviations. The C, N and P concentrations were 395.66 mg g−1, 17.59 mg g−1 and 1.53 mg g−1 for leaves, 414.83 mg g−1, 8.76 mg g−1 and 1.13 mg g−1 for stems, and 401.72 mg g−1, 8.78 mg g−1 and 1.51 mg g−1 for twigs, respectively. The stems elemental concentrations and stoichiometric ratios were positively correlated to that of the leaves. Except for the N of stem and twig, the other elemental concentrations were significantly correlated to altitude. And the leaves and stems N/P and C/P, and twig C/P were significantly negative correlated to altitude. The significant isometry relationships were observed between N vs P of leaves, stems and twigs. The elemental concentrations and stoichiometric ratios of BRB woody plant had no statistical phylogenetic signal. This study presented the evidence that the leaf, stem and twig C, N and P concentrations and stoichiometric ratios from wider altitude-gradient within BRB, it was special and varied largely in different elements, stoichiometric ratios and locations, which supported the growth rate theory in the whole.

Application of low-solubility dolomite as seed material for phosphorus recovery from synthetic wastewater using fluidized-bed crystallization (FBC) technology

Fluidized-bed reactor technology was applied to recover phosphorus from solution via crystallization in a seeded (FBC, Fluidized-bed Crystallization) and unseeded (FBHC, Fluidized-bed Homogeneous Crystallization) system. Dolomite (CaMg(CO3)2) is applied as seed material to provide an existing surface in the seeded crystallization system. Under the optimum pH of 7.7, the presence of seed material in the FBC system enhanced the crystallization ratio of both phosphorus and calcium from 60% to 80%. The operating parameters, including - effluent pHe, up-flow velocity (U, m h−1), and cross-sectional loading (L, kg m−2 hr−1) were optimized in the FBC system. Under optimum conditions at pH 7.7, molar ratio of [Ca]0/[P]0=3.5/1, up-flow rate of 30 m h−1, and cross-sectional loading of 0.9 kg m−2 hr−1, the crystallization ratio (CR) and total removal (TR) of both phosphorus and calcium reached 85% and 92%, respectively. Based on the XRD and Raman pattern, it was confirmed the solid products consist of tricalcium phosphate (Ca3(PO4)2·xH2O) from both FBC and FBHC processes. An economic analysis shows that the disposal cost could be reduced from 0.92 US$ wastewater to 0.2 US$/m3. Phosphorus, encapsulated in a sparingly soluble crystalline form such as dolomite in the FBC system can be potentially used as a slow-release fertilizer and raw material for bio-ceramic and bioactive glass.

Comparison and interpretation of freshwater bacterial structure and interactions with organic to nutrient imbalances in restored wetlands.

Chemical oxygen demand to nitrogen (COD/N) and nitrogen to phosphorus (N/P) ratios have distinct effects on bacterial community structure and interactions. However, how organic to nutrient imbalances affect the structure of freshwater bacterial assemblages in restored wetlands remains poorly understood. Here, the composition and dominant taxa of bacterial assemblages in four wetlands [low COD/N and high N/P (LH), low COD/N and low N/P (LL), high COD/N and high N/P (HH), and high COD/N and low N/P (HL)] were investigated. A total of 7,709 operational taxonomic units were identified by high throughput sequencing, and Actinobacteria, Proteobacteria, and Cyanobacteria were the most abundant phyla in the restored wetlands. High COD/N significantly increased bacterial diversity and was negatively correlated with N/P (R2 = 0.128; p = 0.039), and the observed richness (Sobs) indices ranged from 860.77 to 1314.66. The corresponding Chao1 and phylogenetic diversity (PD) values ranged from 1533.42 to 2524.56 and 127.95 to 184.63. Bacterial beta diversity was negatively related to COD/N (R2 = 0.258; p < 0.001). The distribution of bacterial assemblages was mostly driven by variations in ammonia nitrogen (NH4+-N, p < 0.01) and electrical conductivity (EC, p < 0.01), which collectively explained more than 80% of the variation in bacterial assemblages. However, the dominant taxa Proteobacteria, Firmicutes, Cyanobacteria, Bacteroidetes, Verrucomicrobia, Planctomycetes, Chloroflexi, and Deinococcus-Thermus were obviously affected by variation in COD/N and N/P (p < 0.05). The highest node and edge numbers and average degree were observed in the LH group. The co-occurrence networkindicated that LH promoted bacterial network compactness and bacterial interaction consolidation. The relationships between organic to nutrient imbalances and bacterial assemblages may provide a theoretical basis for the empirical management of wetland ecosystems.

A novel indicator for defining plain urban river network cyanobacterial blooms: resource use efficiency

Increasing eutrophication and climate change have led to heavy cyanobacterial blooms in water diversion sources (e.g., lakes, reservoirs), which can potentially cause algae-bearing water to spread to downstream to an urban river network via diversion channels. Defining the extent of cyanobacterial blooms in an urban river network has become a novel concern in urban river management. In this paper, we investigated the physicochemical and algae community characteristics of a small, closed, urban river network, JiangXinZhou (JXZ), in the Lake Taihu basin. We propose a novel indicator, resource use efficiency (RUE), for defining the extent of cyanobacterial blooms in JXZ, whose recreational drinking water comes entirely from outside diversion sources. The results show that the JXZ's aquatic habitat conditions (mean water temperature, total nitrogen concentration, total phosphorus concentration, and nitrogen to phosphorus ratio) are highly suitable for the proliferation of cyanobacterial biomass during the high-water period. The RUE was used for calculation and shows a strong relationship with algae density, which means that it can be used as an index to define the degree of urban river cyanobacterial blooms. The findings indicate that the risk of cyanobacterial bloom is absent when the RUE is less than 46.81; blooms appear in the water bodies when the RUE reaches up to 106.68. This work provides theoretical support for the sustainable use of regional water resources.

Patterns and driving factors of soil ecological stoichiometry in typical ecologically fragile areas of China

Researchers are paying increasing attention to soil stoichiometry (carbon:nitrogen:phosphorus (C:N:P) ratios) in efforts to explore biogeochemical cycles, but little is known about the spatial pattern, implications, and driving factors of this stoichiometry in large, ecologically fragile areas. To explore these factors, we established three transects that covered a total length of about 4300 km in ecologically fragile areas of China, and sampled at intervals of about 25 km. These transects covered the karst area and the agro-pastoral ecotone of southwestern China, the Qinghai-Tibet Plateau, the Loess Plateau, and the forest-grassland ecotone. We collected 312 soil samples to a depth of 30 cm from 156 plots. The soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) in the ecologically fragile areas showed strong coupling relationships. Soil C:N:P was 51:4:1 to a depth of 30 cm, which is lower than the average global C:N:P (111:8:1). SOC and TN concentrations at 0 to 20 cm were significantly higher than that at 20 to 30 cm, but TP did not differ significantly among depths. SOC, TN, and TP concentrations were highest in the agro-pastoral ecotone, and were lowest in the Loess Plateau. C:N, C:P, and N:P were highest in the karst area. C:N were lowest in the Qinghai-Tibet Plateau, and C:P and N:P were lowest in the Loess Plateau. The spatial pattern of C, N, and P stoichiometry along environmental gradients was variable. The contributions to explaining the soil stoichiometry were highest for climate (21.7%), vegetation (8.9%), soil properties (6.4%), and topography (0.6%) to a depth of 20 cm, versus vegetation (35.9%), climate (5.3%), soil properties (3.3%), and topography (2.1%) at 20 to 30 cm. The results provide new insights into the biogeochemical cycles of C, N, and P and guidance for their impacts on ecological restoration in ecologically fragile areas.

Nitrogen to phosphorus ratio shapes the bacterial communities involved in cellulose decomposition and copper contamination alters their stoichiometric demands.

All living organisms theoretically have an optimal stoichiometric nitrogen: phosphorus (N: P) ratio, below and beyond which their growth is affected, but data remain scarce for microbial decomposers. Here, we evaluated optimal N: P ratios of microbial communities involved in cellulose decomposition and assessed their stability when exposed to copper Cu(II). We hypothesized that (1) cellulose decomposition is maximized for an optimal N: P ratio; (2) copper exposure reduces cellulose decomposition and (3) increases microbial optimal N: P ratio; and (4) N: P ratio and copper modify the structure of microbial decomposer communities. We measured cellulose disc decomposition by a natural inoculum in microcosms exposed to a gradient of N: P ratios at three copper concentrations (0, 1 and 15µM). Bacteria were most probably the main decomposers. Without copper, cellulose decomposition was maximized at an N: P molar ratio of 4.7. Contrary to expectations, at high copper concentration, the optimal N: P ratio (2.8) and the range of N: P ratios allowing decomposition were significantly reduced and accompanied by a reduction of bacterial diversity. Copper contamination led to the development of tolerant taxa probably less efficient in decomposing cellulose. Our results shed new light on the understanding of multiple stressor effects on microbial decomposition in an increasingly stoichiometrically imbalanced world.

Hydrogen energy of mining waste waters: Extraction and analysis of solving issues

Billions liters of wastewater are created every day from industrial and domestic locations, and while wastewater is frequently regarded as a concern, it includes the potential to be regarded as a rich supply of energy and materials. The creation of hydrogen gas by electrolysis utilizing a solar system is an alternate method for treating this residual water. Wastewater has four to five times the energy necessary to its treatment and a good source of bio-hydrogen as a feedstock chemical, clean energy vector, and a fuel generally acknowledged to play a part in the energy system's decarburization. The goal of this research was to see how well wastewater might be used to produce anaerobic hydrogen. Synthetic wastewater with high- and ordinary strength organic loadings as real-time residential wastewater with(out) a combination of food waste was examined. Hydrogen generation during sewage sludge and mining residue suspensions coupled was measured using electro dialytic methods at 50 and 100 mA. Hydrogen purity has been reached at 33 % along the electro dialytic treat of sewage sludge. Hydrogen purity reached 71 percent and 34 percent, respectively, while adding sewage sludge or effluent as enhancers in waste solutions. The maximum extraction ratios of phosphorus (71 %) and tungsten (62 %), respectively, were obtained while the technique has been performed to waste suspensions mixed with sewage sludge. This study's findings could be used to develop onsite household energy and wastewater recovery systems.

Feeding Selectivity of Ruditapes philippinarum on Phytoplankton

A monthly survey of the feeding selectivity of Ruditapes philippinarum in the Yalu River Estuary in 2020–2021 was conducted using high-throughput sequencing identification and visual grading technology. The results showed that the most-dominant species in the water of the shellfish culture area and in the stomachs of R. philippinarum was Karlodinium veneficum in those years. The selectivity index (E) indicated that R. philippinarum avoided consuming Bacillariophyta, Chrysophyta and Cryptophyta throughout the year and preferentially consumed Dinophyta and Chlorophyta. In 2020, the annual average biomass of Dinophyta, Bacillariophyta, Chlorophyta, Dictyochophyta, Cryptophyta and Chrysophyta in the stomach contents of R. philippinarum was 54:14:16:1:10:4; it was 41:12:28:0:1:17 in 2021. The annual average biomass ratio of picophytoplankton, nanophytoplankton and microphytoplankton in the stomachs of R. philippinarum was 13:48:39 in 2020; it was 14:66:20 in 2021. R. philippinarum actively fed on nanophytoplankton and avoided picophytoplankton. Among the phytoplankton of different sizes and groups that R. philippinarum prefer to feed, chemical oxygen demand (COD) and organic phosphorus (DOP) have a significant negative effect on the nanophytoplankton community, pH has a positive effect on the Dictyochophyta community and COD and the inorganic nitrogen to phosphorus ratio (DI-N/P) have a significant positive effect on the Chlorophyta community.

Optimizing the electronic structure of NiSe2/CoSe2 nanosheet arrays by phosphorus doping for high-efficiency oxygen evolution electrocatalysts

Transition metal selenides with pyrite cubic phase structure have attracted much attention in the field of electrochemistry, for their low resistivity properties (<10−3 Ω cm) of Pauli paramagnetic metals. In view of the multi-step catalytic reaction in electrocatalytic oxygen evolution, NiSe2 and CoSe2 with the same crystallographic space group are selected to construct NiSe2/CoSe2 nanosheet arrays on carbon cloth by a facile layered double hydroxides (LDHs) selenization derived method. Moreover, the effect of phosphorus doping on electronic structure and electrocatalytic activity of NiSe2/CoSe2 is also investigated. When the mole ratio of phosphorus to selenium is 10%, the prepared phosphorus-doped NiSe2/CoSe2 nanosheet arrays (10%P-NiSe2/CoSe2) show superior oxygen evolution reaction (OER) performance in alkaline media. It exhibits a small overpotential of 287 mV to realize a current density of 50 mA cm−2 and a low Tafel slope of 68 mv dec−1 in 1 M KOH solution. Furthermore, the cyclic stability test displays that the current density of 10%P-NiSe2/CoSe2 only decreases from 30.0 to 26.5 mA cm−2, after 12 h of continuous water oxidation reaction at 270 mV overpotential. The excellent OER activity of 10%P-NiSe2/CoSe2 can be attributed to the changes in charge density on the crystal surface and the lattice distortion in crystal caused by phosphorus doping. Our work provides an efficient approach for designing OER electrocatalysts through a LDHs derivation assembling with an anion doping method.

Solventing out crystallization-basic magnesium carbonate percipitation for thorough phosphorus removal from ammonium tungstate solution.

The ammonium tungstate solution obtained by leaching scheelite with phosphate contains a large amount of phosphorus. For production of qualified ammonium paratungstate products, phosphorus must be deeply removed from the ammonium tungstate solution. In this study, a novel process for ammonium phosphate recovery and deep phosphorus removal from the solution was proposed. First, ammonium phosphate was crystallized and separated from the ammonium tungstate solution by blowing ammonia and cooling. Results showed that the crystallization ratio of phosphorus was above 95% under the conditions of an ammonia concentration of 4.18 mol/L, an initial phosphorus concentration ranging from 15 g/L to 30 g/L, a holding time of 60 min and the temperature of 20°C. Then, the small portion of phosphorus remaining in the ammonium tungstate solution was further deeply removed by basic magnesium carbonate percipitation. The phosphorus removal efficiency was above 99% and tungsten loss was less than 0.22% under the following conditions: the basic magnesium carbonate stoichiometric ratio was 1.5, the initial phosphorus concentration was ranging from 0.5 to 4 g/L, the reaction time was 120 min and temperature was 25°C. After phosphorus removal, the concentration of phosphorus in the ammonium tungstate solution was below 10 ppm, which meant deep phosphorus removal was achieved.

An electricity-generating bacterium separated from oil sludge microbial fuel cells and its environmental adaptability.

Electricity-generating bacteria as biocatalysts for microbial fuel cells (MFCs), their species, and power generation performance determine the pollution control and power generation performance of MFCs. And there are few studies on the types and performance of electricity-generating bacteria isolated from oily sludge microbial fuel cells. For improving the power generation performance of oily sludge MFCs, an electricity-generating bacterium was isolated from the oily sludge. More importantly, the adaptability of nitrogen to phosphorus ratio, temperature, and pH of the electricity-generating bacteria were adjusted by a controlled variable method. The results of this study showed that the electricity-generating bacterium was identified as Bacillus cereus, with a rod-shaped cell, about 0.5-1.0μm in length. The optimal nitrogen-phosphorus ratio, temperature, and pH of MFCs were 4.67:1, 25 ℃, and pH = 7, respectively. Its maximum power density, COD, and oil removal rate was up to 65 mW·m-3, 90.51%, and 87.76%, respectively. The study of this functional bacterium will provide beneficial assistance for the improvement of oil removal and power generation performance of oily sludge MFCs.

Grain mineral concentration of Chinese winter wheat varieties released between 1970 and 2005 under diverse nutrient inputs

Wheat yields have significantly increased through breeding, but the trends of grain mineral concentrations following the breeding progress are inconsistent. In this study, we established a factorial trial combining 9 nutrient regimes with three (2013–14) and five (2014–15) varieties released from 1970 to 2005 to evaluate changes in grain zinc (Zn), iron (Fe) and selenium (Se) concentrations of Chinese winter wheat (Triticum aestivum L.). The ranges of grain Zn, Fe and Se concentrations were 16.3–49.8 mg kg−1 with a mean of 26.5 mg kg−1, 16.1–39.2 mg kg−1 with a mean of 28.3 mg kg−1, and 0.022–0.078 mg kg−1 with a mean of 0.044 mg kg−1, respectively. Fertilizer inputs significantly decreased grain Zn concentration, generally lowered grain Fe concentration, and had no significant effect on grain Se concentration compared with no fertilizer input. Grain Zn was significantly and negatively correlated with grain yield, soil available Zn concentration, and the ratio of soil available phosphorus to available Zn (P/Zn), but significantly and positively correlated with grain nitrogen (N), Fe, and Se concentrations. The breeding progress had no significant effect on grain Zn, Fe and Se concentrations. In the future, it is necessary to apply for specific fertilizers and breeding new variety for increasing grain mineral concentration to meet the needs of human health.

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.

Influent carbon to phosphorus ratio drives the selection of PHA-storing organisms in a single CSTR

Enriching a biomass with a high fraction of polyhydroxyalkanoate-storing organisms (PHA-storers) represents an essential step in the production of PHAs (bioplastics) from municipal wastewater using mixed microbial cultures. A major challenge is however to create selective growth conditions that are favourable to PHA-storers. Our study thus investigates to what extent the influent COD to phosphorus (COD:P) ratio can be used as a tool for the robust selection of PHA-storers in a single continuous-flow stirred-tank reactor (CSTR). Therefore, we operated five CSTRs in parallel, fed with synthetic wastewater (50% acetate - 50% propionate) with different COD:P ratios (200−1000 gCOD gP−1), and performed a detailed analysis of the microbial communities over long-term (30−70 solid retention times). Our study demonstrates that efficient and robust selection of PHA-storers can be achieved in a single CSTR at high influent COD:P ratios. The selective advantage for PHA-storers increases with the influent COD:P ratio, but only if growth conditions remain limited by both C-substrate and P. In contrast, selection performance deteriorates when COD:P ratios are too high and growth conditions are limited by P only. At an optimal COD:P ratio of 800 gCOD gP−1, a stable microbial community consisting of >90% PHA-storers and dominated by Pannonibacter sp. was selected in the long-term. Finally, our results suggest that high COD:P ratios provide a selective advantage to microorganisms with low cellular P requirements, explaining why different PHA-storers (i.e., Xanthobacter sp. vs. Pannonibacter sp.) were selected depending on the influent COD:P ratio (i.e., 200 vs. 800 gCOD gP−1). Overall, our results provide relevant insights for the development of a new approach for selecting PHA-storers, based on the use of a single CSTR and control of the influent COD:P ratio.

Assessment of physico-chemical parameters of surface waters of a tropical brackish water lake in South Asia

Brackish lake systems and estuaries are unique aquatic systems that support diversified life forms and strongly influence a region's economy. Major chemical water quality parameters of India's second-largest brackish water lake, Pulicat were assessed. Physico-chemical parameters like pH, temperature, suspended solid concentrates, total dissolved solids, salinity, nitrogenous nutrients, phosphate, silicate, and chlorophyll a were analysed. The results obtained for different parameters were compared and interpreted with statistical software SPSS version 20 and images were plotted using the Arc GIS spatial analyst tool. During the summer months, the nitrogen to phosphorus ratio ranges from a minimum of 1.96 to a maximum of 16.64 (9.55 ± 4.01) while it ranges from a minimum of 7.98 to a maximum of 15.52 (12.47 ± 2) during the pre-monsoon. In the monsoon season, the nitrogen to phosphorus ratio of surface water suggests a range from a minimum of 8.64 to a maximum of 17.58 (13.87 ± 2.14). During the post-monsoon season, the nitrogen to phosphorus ratio ranges from 4.98 to 17.34 (11.77 ± 3.68). The average nitrogen to phosphorus ratios were 9.6, 12.5, 13.9 and 11.8 in summer, pre-monsoon, monsoon, and post-monsoon respectively. The nitrogen to phosphorus ratio was lower than the Redfield ratio for all the seasons. The average concentration of chlorophyll a was 14.9, 13.4, 12.8 and 11.8 in summer, pre-monsoon, monsoon, and post-monsoon respectively. As per the Pearson Correlation Coefficient, there was no significant correlation among nitrogen, phosphorus, and chlorophyll a. This suggests the influence of suspended solid concentrates, and nitrogen and phosphorus flux in the sediment-water interface might be interfering with the nutrient cycles and primary productivity.

Stoichiometric Ratios of Carbon, Nitrogen and Phosphorus of Shrub Organs Vary with Mycorrhizal Type

Mycorrhizal types are a predictive framework for nutrient cycling within and across ecosystems, and their types represent different nutrient-acquisition strategies for plants. Carbon (C), nitrogen (N) and phosphorus (P) stoichiometric ratios are essential for understanding biogeochemical processes. The purpose of this study was to reflect the balance in the process of plant resource acquisition by exploring the C, N and P stoichiometric ratios (C/N, N/P, and C/P) in shrub organs in different mycorrhizal types. In this study, the C, N, and P stoichiometric ratios in leaves, stems and roots were analyzed in the types of arbuscular mycorrhizal (AM), ectomycorrhizal (ECM) and AM + ECM of shrubs in Northern China. The results showed that C/N in the stems and roots of AM plants (95.75 and 81.42) was significantly lower than in AM + ECM plants (109.89 and 102.37) and ECM plants (107.67 and 96.93), while both N/P and C/P in the leaves, stems and roots of AM shrubs (38.67, 36.17, 40.69; 1028.14, 2989.13, and 2659.18) were significantly higher than in ECM shrubs (30.52, 22.31, 20.47; 796.51, 2208.28, and 1714.95). Moreover, different elements among the same plant organs were closely correlated, and the same pattern was found among the same element ratios among different plant organs. This suggests that mycorrhizal type can influence C, N and P ratios among different organs.

Pathways of Nitrogen and Phosphorus Utilization and Removal from Cyanobacteria Wastewater by Combining Constructed Wetlands with Aerobic Reactors

Due to its low C/N ratio and high concentrations of nitrogen and phosphorus, the effluent of anaerobic cyanobacteria fermentation cannot be directly discharged without further treatment. To effectively reduce nutrient loads and utilize the nutrient resources of biogas slurry generated from the anaerobic digestion of stored algae, two different aerobic treatment units (AUs) were combined with an ecological treatment unit (EU) to create two different treatment systems. The two AUEU systems paired a constructed wetland (CW) with either a cascade biological contact reactor (CBCR) or a carrousel oxidation ditch reactor (CODR). In this paper, the water quality characteristics of biogas slurry were measured, and comprehensive experiments on the two trial-treatment systems were carried out to validate their performance in removing pollutants and utilizing resources. Furthermore, the pollutant removal efficiencies of the combined systems, along with the removal mechanisms and utilization of the nitrogen and phosphorus in the CWs, were also investigated. The results showed that the CWs, with aquatic vegetation, took up the majority of removed nitrogen and phosphorus by absorption, which effectively reduced the concentration of pollutants in the effluent and enabled the nitrogen and phosphorus to be reused in plants. Biomass assimilation by the absorption by vegetation took up 75.8%, 66.1%, 70.3%, and 86% of the removed NH4+-N, NOx−-N, TN, and TP, respectively.