Search

Climate change could add a variety of uncertainties to hydrological processes and water resources. Very limited efforts have been devoted to applying the US-EPA (Environmental Protection Agency)'s Hydrologic and Water Quality System (HAWQS) model for predicting climate change impacts on hydrological processes at the basin scale. Here, we applied the model to project the next 50 years' (from 2021 to 2070) hydrological processes at the Yazoo River basin in Mississippi, USA. Simulations showed that over the next 50 years, there are no significant trends in monthly precipitation, ET, runoff and discharge; only 2% of the annual precipitation percolated into the deep aquifer; and dry seasons become dryer and wet seasons become wetter. These findings provide very useful information to stakeholders for water resource management. Our study further suggests that the HAWQS model is a user-friendly and time-saving tool for basin-scale hydrological modelling. [ABSTRACT FROM AUTHOR]

Phosphorus (P) as an essential nutrient for life sustains the productivity of food systems; yet misdirected P often accumulates in wastewater and triggers water eutrophication if not properly treated. Although technologies have been developed to remove P, little attention has been paid to the recovery of P from wastewater. This work provides a comprehensive review of the state-of-the-art P removal technologies in the science of wastewater treatment. Our analyses focus on the mechanisms, removal efficiencies, and recovery potential of four typical water and wastewater treatment processes including precipitation, biological treatment, membrane separation, and adsorption. The design principles, feasibility, operation parameters, and pros & cons of these technologies are analyzed and compared. Perspectives and future research of P removal and recovery are also proposed in the context of paradigm shift to sustainable water treatment technology. P removal efficiencies and P recovery potential of four typical wastewater treatment processes are critically reviewed. Feasibility, transfer routes, operation parameters, and pros & cons of these technologies in P recovery are analyzed and compared P can be recovered from wastewater into value-added fertilizers or soil amendment. Perspectives and future research directions of P removal and recovery are outlined. [ABSTRACT FROM AUTHOR]

Recent advancement in molecular techniques has spurred numerous studies on responses of microorganisms to lead exposure, leveraging detailed phylogenetic analyses and functional gene identification to discern the effects of lead toxicity on microbial communities. A comprehensive review of recent research is provided on (1) lead resistance mechanisms of microorganisms; (2) microbial community changes in contaminated aquatic sediments and terrestrial soils; and (3) lead resistance genes applied to lead biosensor development. Ample evidence in the literature, including both in vitro and in situ studies, indicates that exposure to lead inhibits microbial activities (such as respiration and metabolism), reduces biomass and alters microbial community structure. Even at sites where microbial communities do not vary compositionally with contaminant levels, functional differences between microbial communities are evident. The main mechanisms of lead resistance involve extracellular and intracellular biosorption, precipitation, complexation, and/or efflux pumps. The suites of genes associated with lead resistance mechanisms can serve, when considered with phylogenetic information, as indicators of lead contamination. This holds potential for development of next generation lead biosensors. To promote applications of advanced knowledge, molecular techniques, and lead biosensor technology, perspectives on using microbial indicators for site ecological assessment are presented. [ABSTRACT FROM AUTHOR]

To assess the role of salicylic acid (SA) supplied with 5 approaches in alleviating chlorosis induced by iron (Fe) deficiency in peanut plants growing on calcareous soil, SA was supplied as soil incorporation, making slow-release particles, seed soaking, irrigation and foliar application. SA application, particularly, SA supplied by slow release particles, dramatically increased growth parameters, yield and quality of peanut, and increased Fe concentration in peanut grain. Meanwhile, SA application increased the H+-ATPase activity, reduced pH of soil, increased Fe3+-Chelate Reductase (FCR) activity in roots, and increased Fe concentration in roots. Furthermore, SA increased active Fe content and increased chlorophyll content. In addition, SA improved enzymes activities containing superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and protected Fe deficiency induced oxidative stress. Therefore, SA has a good effect on alleviating chlorosis induced by Fe deficiency on calcareous soil. However, in the 5 SA supplied approaches, foliar application and making slow release particles were more effective. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wheat straw hydrochar modified with 0.2 M KMnO 4 obtained optimal results. • KMnO 4 modification loaded MnOx microparticles on hydrochar surface. • Oxygen-containing surface functional groups increased after modification. • KMnO 4 modification enhanced adsorption of Pb(II), Cd(II), Cu(II) by > 10 times. Hydrochars formed by hydrothermal carbonization of hickory wood, bamboo, and wheat straw at 200 °C were modified by potassium permanganate (KMnO 4) for the sorption of Pb(II), Cd(II), and Cu(II). The wheat straw hydrochar (WSHyC) modified with 0.2 M KMnO 4 resulted in the most promising adsorbent (WSHyC-0.2KMnO 4). Characterization of WSHyC and WSHyC-0.2KMnO 4 revealed that the modified hydrochar features large specific surface area, rich of surface oxygenic functional groups (OCFG), and a significant amount of MnOx micro-particles. Batch adsorption experiments indicated that the adsorption rate by WSHyC-0.2KMnO 4 was faster than for WSHyC, attaining equilibrium after around 5 h. The optimum adsorption capacity (Langmuir) of Pb(II), Cd(II), and Cu(II) by WSHyC-0.2KMnO 4 was 189.24, 29.06 and 32.68 mg/g, respectively, 12 ∼ 17 times greater than by WSHyC. The significantly enhanced heavy metal adsorption can be attributable to the increased OCFG and MnOx microparticles on the surface, thereby promoting ion exchange, electrostatic interactions, and complexation mechanisms. [ABSTRACT FROM AUTHOR]

The increasing environmental and human health concerns about lead in the environment have stimulated scientists to search for microbial processes as innovative bioremediation strategies for a suite of different contaminated media. In this paper, we provide a compressive synthesis of existing research on microbial mediated biogeochemical processes that transform lead into recalcitrant precipitates of phosphate, sulfide, and carbonate, in a genetic, metabolic, and systematics context as they relate to application in both laboratory and field immobilization of environmental lead. Specifically, we focus on microbial functionalities of phosphate solubilization, sulfate reduction, and carbonate synthesis related to their respective mechanisms that immobilize lead through biomineralization and biosorption. The contributions of specific microbes, both single isolates or consortia, to actual or potential applications in environmental remediation are discussed. While many of the approaches are successful under carefully controlled laboratory conditions, field application requires optimization for a host of variables, including microbial competitiveness, soil physical and chemical parameters, metal concentrations, and co-contaminants. This review challenges the reader to consider bioremediation approaches that maximize microbial competitiveness, metabolism, and the associated molecular mechanisms for future engineering applications. Ultimately, we outline important research directions to bridge future scientific research activities with practical applications for bioremediation of lead and other toxic metals in environmental systems. [Display omitted] • Microorganisms mediate biomineralization and biosorption of Pb in the environment. • Tolerance of Pb toxicity is critical to selection of phosphate solubilizing bacteria. • Sulfate reduction functional genes may serve as environmental genetic markers. • Biogenesis of carbonate involves ureolytic organisms in alkaline environments. • Optimization of microbe functionalities is key to real world applications. [ABSTRACT FROM AUTHOR]

Graphic abstract Highlights • Governing adsorption mechanisms of heavy metals onto carbon adsorbents are summarized. • Various methods for introduction of oxygen, nitrogen, and sulfur functional groups onto carbon surfaces are categorized. • Effects of various functional groups on heavy metal adsorption onto different carbon materials are discussed. • Perspectives of future work on functionalized carbon adsorbents for heavy metal removal is also presented. Abstract Carbon-based adsorbents such as graphene and its derivatives, carbon nanotubes, activated carbon, and biochar are often used to remove heavy metals from aqueous solutions. One of the important aspects of effective carbon adsorbents for heavy metals is their tunable surface functional groups. To promote the applications of functionalized carbon adsorbents in heavy metal removal, a systematic documentation of their syntheses and interactions with metals in aqueous solution is crucial. This work provides a comprehensive review of recent research on various carbon adsorbents in terms of their surface functional groups and the associated removal behaviors and performances to heavy metals in aqueous solutions. The governing removal mechanisms of carbon adsorbents to aqueous heavy metals are first outlined with a special focus on the roles of surface functional groups. It then summarizes and categorizes various synthesis methods that are commonly used to introduce heteroatoms, primarily oxygen, nitrogen, and sulfur, onto carbon surfaces for enhanced surface functionalities and sorptive properties to heavy metals in aqueous solutions. After that, the effects of various functional groups on adsorption behaviors of heavy metals onto the functionalized carbon adsorbents are elucidated. A perspective of future work on functional carbon adsorbents for heavy metal removal as well as other potential applications is also presented at the end. [ABSTRACT FROM AUTHOR]

Alginate-based composites have been extensively studied for applications in energy and environmental sectors due to their biocompatible, nontoxic, and cost-effective properties. This review is designed to provide an overview of the synthesis and application of alginate-based composites. In addition to an overview of current understanding of alginate biopolymer, gelation process, and cross-linking mechanisms, this work focuses on adsorption mechanisms and performance of different alginate-based composites for the removal of various pollutants including dyes, heavy metals, and antibiotics in water and wastewater. While encapsulation in alginate gel beads confers protective benefits to engineered nanoparticles, carbonaceous materials, cells and microbes, alginate-based composites typically exhibit enhanced adsorption performance. The physical and chemical properties of alginate-based composites determine the effectiveness under different application conditions. A series of alginate-based composites and their physicochemical and sorptive properties have been summarized. This critical review not only summarizes recent advances in alginate-based composites but also presents a perspective of future work for their environmental applications. [ABSTRACT FROM AUTHOR]

Sedimentation and soil salinization are of serious concern in the Yellow River Delta. This study explores novel applications of dredged sediment to improve soil salinity environment and winter wheat (Triticum aestivum) production. Filed trials consisted of a control and applications of sediment at 100 Mg/ha (S100) and 200 Mg/ha (S200) replicated randomly within two blocks. Wheat growth and yield were assessed along with measurements of soil properties. Results indicated that sediment application significantly improved wheat growth. Wheat economic yield for S100 and S200 was 35% and 73% more than for the control. We attributed the improved wheat growth and yield to the reduced soil electrical conductivity, which, in turn, was associated with increased soil macropores and hydraulic conductivity with the incorporation of sandy sediment into the clayey saline soil. This study reveals that incorporating dredged Yellow River sediment into the saline land is a feasible agricultural practice in the Yellow River Delta. [ABSTRACT FROM AUTHOR]

Controlling water pollution by phosphorus (P) and satisfying high demand of P fertilizer in agriculture are two global challenges for sustainable development. This paper presents a novel application of iron modified biochar as an adsorbent to recover P from wastewater and reuse it as P fertilizer. Granular iron biochar (GIB) and ball milled powder iron biochar (PIB) were prepared from pinewood pretreated with iron salt. The biochars were characterized to determine their surface properties. Their effectiveness in P removal from wastewater was evaluated with packed column filters for GIB and continuous flow reactors for PIB. The spent biochar was tested to determine if it is safe for agricultural application as alternative P fertilizer. The results showed that GIB and PIB were highly porous, had high specific surface area (385 and 331 m2 g−1, respectively), and contained high levels of iron (mainly γ-Fe 2 O 3). Both GIB and PIB showed excellent performance for P removal from wastewater. The P adsorption capacity of GIB in the column filter was 16 times larger than that of sand. A fast P adsorption kinetic rate (0.144 min−1) was observed for PIB in the flow reactor. The spent biochars showed no negative effects on bean germination or even some positive effects on seedling growth, indicating they can be safely used as P fertilizer. This study provides the technical basis of a sustainable wastewater treatment strategy that can capture the full values of water, P, and biochar. [Display omitted] • Granular iron biochar (GIB) and ball milled power iron biochar (PIB) were prepared. • GIB and PIB are high in specific surface area and rich in iron oxides. • GIB and PIB remove P efficiently from wastewater in column filters and flow reactors. • Spent biochars showed no negative effects on bean germination and seedling growth. [ABSTRACT FROM AUTHOR]

Understanding anthropogenic and hydro-climatic influences on nutrient concentrations and export from highly managed catchments often necessitates trend detection using long-term monitoring data. This study analyzed the temporal trend (1979–2014) of total nitrogen (TN) and total phosphorus (TP) concentrations and export from four adjacent coastal basins in south Florida where land and water resources are highly managed through an intricate canal network. The method of integrated seasonal-trend decomposition using LOESS (LOcally weighted regrESSion) was employed for trend detection. The results indicated that long-term trends in TN and TP concentrations (increasing/decreasing) varied with basins and nutrient species, reflecting the influence of basin specific land and water management practices. These long-term trends were intervened by short-term highs driven by high rainfall and discharges and lows associated with regional droughts. Seasonal variations in TP were more apparent than for TN. Nutrient export exhibited a chemostatic behavior for TN from all the basins, largely due to the biogenic nature of organic N associated with the ubiquity of organic materials in the managed canal network. Varying degrees of chemodynamic export was present for TP, reflecting complex biogeochemical responses to the legacy of long-term fertilization, low soil P holding capacity, and intensive stormwater management. The anthropogenic and hydro-climatic influences on nutrient concentration and export behavior had great implications in nutrient loading abatement strategies for aquatic ecosystem restoration of the downstream receiving waterbody. [ABSTRACT FROM AUTHOR]

Numerical hydrodynamic modeling provides quantitative understanding of how physical alterations of an estuary may alter the waterbody hydrodynamics and the rate of mixing with the ocean. In this study, a three dimensional hydrodynamic model (CH3D) was used to compare simulated salinities between the existing condition and five historical cases representing varying physical alterations of the Caloosahatchee Estuary involving (1) removal of the headwater structure (S-79); (2) removal of the downstream causeway to Sanibel Island; (3) backfilling an oyster bar near the estuary month; (4) refilling the navigation channel; and (5) the pre-development bathymetric condition. The results suggested that some alterations including the Sanibel Causeway, backfilling the oyster bar and the S-79 structure may have some local effects but did not change estuarine salinity structure significantly. Refilling the navigation channel had a more profound effect, resulting in a dry season salinity reduction of about 5 when compared with the existing condition. The reduced salt transport was more pronounced with the pre-development bathymetry because the estuary as a whole was much shallower than today. The significant system-wide increase in salt transport caused by the historic dredging of the navigation channel in the Caloosahatchee Estuary has significant implications in the development of attainable environmental flow targets for protecting the estuarine ecosystem. [ABSTRACT FROM AUTHOR]

Summary We developed a lumped conceptual rainfall–runoff model for rapid prediction of runoff generated in the unique hydrological setting with flat terrain, sandy soils, high groundwater table, and a dense drainage canal network in south Florida. The model is conceptualized as rainfall and evapotranspiration filling and emptying the root zone and excess rainfall recharging three storage zones. Outflows from these storage zones, routed with parallel arrangement of three linear reservoirs, represent different flow components of catchment runoff, i.e., slow drainage (shallow subsurface flow), medium drainage (interflow and saturation excess overland flow), and fast drainage (direct runoff from impervious urban areas or from water table management in agricultural land). The model is parsimonious with eight model parameters along with two optional water management parameters. A regionalization study was conducted through model parameterization to achieve target hydrological behavior of typical land uses, which are the most significant basin descriptor affecting catchment hydrology in south Florida. Cross validation with 16 gauged basins dominated by urban, agricultural, and natural lands, respectively, indicated that the model provides an effective tool for rapid prediction of runoff in ungauged basins using the regionalized model parameters. A case study is presented, involving application of the model to support real-time adaptive management to hydrological operations for protection of estuarine ecosystems. [ABSTRACT FROM AUTHOR]

This study determined the interactive effects of biochar and lead toxicity on the soil microbial community in a phytoextraction experiment. Arranged with a completely randomized design in a greenhouse, banana liners were planted singly in a sandy soil spiked with Pb(NO 3) 2 at 0, 400 and 1200 mg kg−1 and amended with bamboo biochar (pyrolyzing at 600 °C) at 0, 1, 3%. Soil samples were taken from triplicated pots five months after planting and measured for (i) content of lead and organic carbon; (ii) lead speciation; and (iii) microbial community composition through 16S rRNA gene sequencing. DNA sequencing results showed that lead and biochar treatments had significant individual and interactive effects on soil microbial dissimilarities from taxonomic levels of phyla to genera. While some specific taxa were lead resistant, biochar addition apparently alleviated lead toxicity and increased their richness (e.g., Alkanibacter, Muciaginibacter , Burkholderiaceae , and Beggiatoaceae). Soil analysis data indicated that biochar not only helped retain more lead in the soil matrix but created a soil environment inducive for transformation of lead into highly insoluble pyromorphite. This study highlights the effectiveness of biochar for lead remediation and the sensitivity of soil microorganisms in sensing changes in soil environment and lead bioavailability. [Display omitted] • Lead had a greater effect on soil microbial communities than biochar • Biochar amendment enhanced Pb sorption and pyromorphite formation • Biochar had interactive effects in alleviating Pb toxicity and increasing richness of Pb resistant taxa [ABSTRACT FROM AUTHOR]

Highlights: [•] A 3-D hydrodynamic model was used to calculate residence time in a subtropical estuary. [•] Residence time changed with freshwater inflows and location in the estuary. [•] We demonstrated the existence of a “residence time maximum” zone in the estuary. [•] The “residence time maximum” correlated with field peak chlorophyll a concentrations. [Copyright &y& Elsevier]

Abstract: Knowledge of estuarine hydrodynamics and water quality comes mostly from studies of large estuarine systems. The processes affecting algae, nutrients, and dissolved oxygen (DO) in small and shallow subtropical estuaries are relatively less studied. This paper documents the development, calibration, and verification of a three dimensional (3D) water quality model for the St. Lucie Estuary (SLE), a small and shallow estuary located on the east coast of south Florida. The water quality model is calibrated and verified using two years of measured data. Statistical analyses indicate that the model is capable of reproducing key water quality characteristics of the estuary within an acceptable range of accuracy. The calibrated model is further applied to study hydrodynamic and eutrophication processes in the estuary. Modeling results reveal that high algae concentrations in the estuary are likely caused by excessive nutrient and algae supplies in freshwater inflows. While algal blooms may lead to reduced DO concentrations near the bottom of the waterbody, this study indicates that stratification and circulation induced by freshwater inflows may also contribute significantly to bottom water hypoxia in the estuary. It is also found that high freshwater inflows from one of the tributaries can change the circulation pattern and nutrient loading, thereby impacting water quality conditions of the entire estuary. Restoration plans for the SLE ecosystem need to consider both a reduction of nutrient loading and regulation of the freshwater discharge pattern. [Copyright &y& Elsevier]

Abstract: Attachment of stormwater treatment areas (STAs) or constructed wetlands to stormwater retention reservoirs can achieve substantial reductions in pollutant loadings if properly operated and maintained. Besides water quality improvement, optimally operated reservoir-assisted STAs provide support for ecosystem remediation, flood control, and supplemental water supply. An adaptive, multiobjective real-time control model is developed for reservoir-assisted STA systems that incorporates fuzzy rule-based operating rules optimized using a genetic algorithm interacting with a simulation model of the system. The model is applied to the North Fork reservoir-assisted STA located in the watershed of the St. Lucie Estuary, Florida. Optimal daily feedback operational policies are developed for managing freshwater discharges to the Estuary for coastal ecosystem restoration, maximizing the natural treatment efficiency and of the STA, and providing supplemental water supply for irrigation. Testing and validation results from application of the fuzzy optimal control model confirm achievement of multiple targets and criteria for the North Fork project, while demonstrating potential for adaptive management of reservoir-assisted STA systems throughout the coastal regions of south Florida. [Copyright &y& Elsevier]

Many coastal ecosystems have been adversely impacted by increased storm-water drainage due to expanding urbanization. The ecosystem of the St. Lucie Estuary (SLE), located on the east coast of south Florida, has been greatly influenced by development of an intricate network of storm-water drainage canals in the tributary watershed. A suite of models dealing with watershed hydrology, reservoir optimization, and estuary salinity and ecology are applied for optimal sizing and operation of storm-water reservoirs. The multipurpose storm-water control facilities provide for hydrologic restoration to predrained or natural hydrologic conditions for recovery of salinity-sensitive biota in the SLE, as well as supplemental irrigation water and pollution control through connected storm-water treatment areas. The optimization is challenging since the ecological goal is for mean monthly storm-water discharges to the SLE to coincide with the desired natural frequency distribution, rather than simply attempting to control individual extreme events. The OPTI6 optimization model applies a genetic algorithm, coupled with a daily simulation model of the storm-water drainage network, to optimize the sizing and fuzzy operating rules of reservoirs for controlling storm-water discharges to the SLE. Results indicate that the desired frequency distribution is closely matched and the level of service for the supplemental irrigation demand is met under reduced storage requirements. [ABSTRACT FROM AUTHOR]

Starting in 1998, a study was conducted to characterize storm water quality from predominant land use types in a coastal watershed along the south central coast of Florida, namely citrus, pasture, urban, natural wetland, row crop, dairy, and golf courses. Sixty-three sampling sites were located at strategic points on drainage conveyances for each of seven specific land use areas. Runoff samples were collected following storm events that met defined rainfall criteria for a period of 30 months. Nitrogen (N), phosphorus (P), heavy metals, pesticides, and other water quality parameters were determined, and the results were analyzed to compare and characterize land uses as relative sources for these constituents in runoff. Results showed that runoff from most land use types had low dissolved oxygen concentration and that sediment and nutrient concentrations were closely related to land use, particularly to the amount of fertilizer applied in each land use. Among the eight heavy metals tested, copper was the most frequently detected and was mostly associated with runoff from citrus and golf course land uses. High levels of arsenic were also detected in golf course runoff. The most frequently detected pesticide was simazine from citrus. The information and methodologies presented may facilitate pollution source characterization and ecological restoration efforts. [ABSTRACT FROM AUTHOR]

The influence of amorphous clay-size materials on geotechnical engineering properties is recognized only for soils developed from volcanic ash under extremely wet, alumina-rich soil environments (called Andisols). The objective of this study was to quantify the amorphous clay-size materials in less weathered volcanic soils that are rich in silica, and to determine the influence of the amorphous materials on plasticity and shrink-swell behavior of these soils. Soil and weathered rock samples were taken from a slow-moving landslide site in Honolulu. Quantification of amorphous and crystalline clay content was performed with x-ray diffraction and the Rietveld method. Atterberg limits and shrink-swell potential of the soil samples were determined. The results showed that clay-size fraction in both soil and weathered rock samples were predominantly amorphous (55-74% in soil and 48-63% in weathered rock). Smectite and halloysite were the primary crystalline clay minerals, constituting about 15-30% of the clay fraction in soils. Atterberg limits of the soil ranged from 65 to 135 for liquid limit, from 30 to 40 for plastic limit, and 9 to 25 for shrinkage limit. Volumetric free swell ranged from 2 to 21%. The plasticity and shrink-swell potential increased with increasing the content of amorphous clay-size materials in the soil. Air drying and oven drying did not significantly change the plasticity. The study concluded that silica-rich amorphous materials dominate the clay mineralogy of the soils studied, resulting in the plasticity and shrink-swell behavior similar to that of smectite-rich soils and distinct from that of Andisols. [ABSTRACT FROM AUTHOR]

The shear behavior of soils rich in amorphous clay-size materials was not well reported in the literature. This study analyzed the direct shear and ring shear test data of soil samples containing 55–74% amorphous materials in the clay fraction from a slow-moving landslide in eastern Honolulu, HI. The direct shear test results showed that the undisturbed soil samples when not sheared internally had peak cohesion (c) of about 50 kPa and internal friction angle (Ø) of about 10°. This implies that the amorphous clay-size materials provided strong interparticle bonds for the soils. Breaking of the bonds during the softening process and redistribution of the amorphous clay-size materials were primarily responsible for the drop from the peak strength to the residual strength (c=0, Ø=10° from back calculation with SLOPE/W and c=0, Ø=5–7° from the ring shear test). The drained residual failure envelope is stress dependent due to the interaction of the gel-like amorphous clay-size materials with crystalline silt- and sand-sized particles. The amorphous clay-size materials act as the contact between crystalline particles. The contact increases with increasing consolidation stress, resulting in a decrease in the shear strength and the residual friction angle. [Copyright &y& Elsevier]

Ball milling was used to fabricate a nanocomposite of 20% hickory biochar (600 °C) and 80% expanded vermiculite (20%-BC/VE). This novel composite adsorbent had much higher removal of As(V) from aqueous solutions than ball-milled biochar and expanded vermiculite. Characterization of these adsorbents showed that the enhanced As(V) adsorption was ascribed to much larger surface area and pore volume (2–6 times), notable changes in crystallinity, activation of cations, and increased functional groups in the nanocomposite compared with the ball-milled products of their pristine counterparts. The As(V) adsorption process by the 20%-BC/VE fitted well with the pseudo-second-order kinetic model (R 2 = 0.990) and Langmuir isotherm model (R 2 = 0.989) with a maximum adsorption capacity of 20.1 mg g−1. The 20%-BC/VE best performed at pH about 6. The adsorption efficiency was not sensitive to the competition of N O 3 − , C l − , S O 4 2 − , as well as the coexistence of humic acid. However, the adsorption capacity for As(V) was significantly reduced by coexisting with P O 4 3 − . The 20%-BC/VE composite can potentially serve as a superior low-cost adsorbent for As(V) removal in real-world applications. Image 1 • Ball milling was used to fabricate a novel biochar/vermiculite nanocomposite. • Ball milling enhanced physiochemical properties and activated cations in the composite. • The composite feature Langmuir maximum As(V) sorption capability of 20.1 mg g−1. • Adsorption of As(V) by the composite was insensitive to humic acid and anions. [ABSTRACT FROM AUTHOR]

Pristine and ball milled wheat stalk biochars pyrolysed at 300 °C, 450 °C, 600 °C were studied for tetracycline hydrochloride (TCH) adsorption from aqueous solution. Surface characteristics of ball milled biochar (BM-biochar) were significantly enhanced over their pristine counterparts. TCH adsorption occurred largely on external surface and by filling pores of biochars as evidenced by strong positive correlation between adsorption and external specific surface area (SSA), total pore volume, or mesoporous volume. A two-stage intra-particle diffusion model, limited by the TCH diffusion through the boundary liquid layer, well described TCH adsorption. Maximum TCH adsorption occurred at about pH = 6–8. While solution cations including Na+, K+ and Mg2+ subdued TCH adsorption as they competed for adsorption sites, Ca2+ promoted TCH adsorption due to formation of tetracycline-Ca2+ complexes. The best performing BM-biochar was the one pyrolysed at 600 °C with TCH adsorption amount of 84.54 mg/g. Therefore, this BM-biochar has the potential for TCH removal from aqueous solutions. And the research shed light on the management of organic contaminants in real wastewater by BM-biochar. Image 1 • Ball milling enhanced external specific surface area and mesoporous volume of biochar. • Ball milling increased sorption ability of biochars to TCH. • TCH adsorption by BM-biochars was controlled by surface adsorption and pore filling. • TCH adsorption on BM-biochars was affected by pH and cation in solution. [ABSTRACT FROM AUTHOR]

A facile ball-milling method was developed to synthesize MgO/biochar nanocomposites as a dual-functional adsorbent. The physicochemical properties of the synthesized nanocomposites indicated that the composites achieved nano-scaled morphologies and mesoporous structure with MgO nanoparticles, which is approximate 20 nm and dispersed uniformly on the surface of the biochar matrix. Batch sorption experiments yielded 62.9% removal of phosphate, an anion, and 87.5% removal of methylene blue, a cationic organic dye, at low adsorbent dosages of 1.0 g L−1 and 0.2 g L−1, respectively. This work indicates that ball milling, as a facile and promising method for synthesis of carbon-metal oxide nanocomposites, lends the advantage of operational flexibility and chemical adjustability for targeted remediation of diverse environmental pollutants. Image 1 • Solvent-free synthesis of MgO/biochar nanocomposites was achieved through ball milling. • MgO nanoparticles (20 nm) dispersed uniformly on the surface of the biochar matrix. • MgO/biochar nanocomposites showed dual functions to effectively adsorb cationic dye and anionic phosphate. • Ball milling method has the advantage of operational flexibility and chemical adjustability. [ABSTRACT FROM AUTHOR]

The development of alginate-based composites in agriculture to combat nutrient loss and drought for sustainable development has drawn increasing attention in the scientific community. Existing studies are however scattered, and the retention and slow-release mechanisms of alginate-based composites are not well understood. This paper systematically reviews the current literature on the preparation, characterization, and agricultural applications of various alginate-based composites. The synthesis methods of alginate-based composites are firstly summarized, followed by a review of available analytical techniques to characterize alginate-based composites for the attainment of their desired performance. Secondly, the performance and controlling factors for agricultural applications of alginate-based composites are discussed, including aquasorb, slow-release fertilizer, soil amendment, microbial inoculants, and controlled release of pesticides for pest management. Finally, suggestions and future perspectives are proposed to expand the applications of alginate-based composites for sustainable agriculture. [Display omitted] • Preparation methods affect the physicochemical properties of alginate-based composites. • The selection of encapsulation object depends on the actual demand. • Alginate-based composites function as conditioners in agriculture. • Recommendations and future perspectives are proposed. [ABSTRACT FROM AUTHOR]

Summary: Cultivated peanut (Arachis hypogaea L.) is an important oil and cash crop. Pod size is one of the major traits determining yield and commodity characteristic of peanut. Fine mapping of quantitative trait locus (QTL) and identification of candidate genes associated with pod size are essential for genetic improvement and molecular breeding of peanut varieties. In this study, a major QTL related to pod size, qAHPS07, was fine mapped to a 36.46 kb interval on chromosome A07 using F2, recombinant inbred line (RIL) and secondary F2 populations. qAHPS07 explained 38.6%, 23.35%, 37.48%, 25.94% of the phenotypic variation for single pod weight (SPW), pod length (PL), pod width (PW) and pod shell thickness (PST), respectively. Whole genome resequencing and gene expression analysis revealed that a RuvB‐like 2 protein coding gene AhRUVBL2 was the most likely candidate for qAHPS07. Overexpression of AhRUVBL2 in Arabidopsis led to larger seeds and plants than the wild type. AhRUVBL2‐silenced peanut seedlings represented small leaves and shorter main stems. Three haplotypes were identified according to three SNPs in the promoter of AhRUVBL2 among 119 peanut accessions. Among them, SPW, PW and PST of accessions carrying Hap_ATT represent 17.6%, 11.2% and 26.3% higher than those carrying Hap_GAC，respectively. In addition, a functional marker of AhRUVBL2 was developed. Taken together, our study identified a key functional gene of peanut pod size, which provides new insights into peanut pod size regulation mechanism and offers practicable markers for the genetic improvement of pod size‐related traits in peanut breeding. [ABSTRACT FROM AUTHOR]

Vertical density stratification often plays an important role in the formation and expansion of coastal hypoxic zones through its effect on near-bed circulation and vertical oxygen flux. However, the impact of future climate change on estuarine circulation is widely unknown. Here, we developed and calibrated a three-dimensional hydrodynamic model for Pensacola Bay, a shallow subtropical estuary in the northeastern Gulf of Mexico. Model simulations based on years 2013–2017 were applied to examine changes in salinity, temperature, and density under future climate scenarios, including increased radiative forcing (IR) and temperature (T), increased freshwater discharge (D), sea level rise (SLR), and wind intensification (W). Simulations showed that the impacts of climate change on modeled state variables varied over time with external forcing conditions. The model demonstrated the potential for sea level rise and increased freshwater discharge to episodically increase vertical density gradients in the Bay. However, increased wind forcing destabilized vertical gradients, at times reducing the spatial extent and duration of stable stratification. For time periods with low freshwater discharge, moderate increases in wind speed (10%) can destabilize density gradients strengthened by increased discharge (10%) and sea level rise (0.48 m). In contrast, destruction of strong density gradients that form near the mid-Bay channel following flood events requires stronger wind forcing. These results highlight the importance of considering natural variability in freshwater and wind forcing, as well as local phenomena that are generally unresolved by global climate models. • Estuarine stratification can affect the development of summertime benthic hypoxia. • Impacts of climate change on stratification and water quality are widely unknown. • Sea level rise and increased freshwater inputs will likely enhance stratification. • Intensification of cross-shore winds may destruct stable vertical density gradients. [ABSTRACT FROM AUTHOR]

Auxin response factors (ARFs) play important roles in plant growth and development; however, research in peanut (Arachis hypogaea L.) is still lacking. Here, 63, 30, and 30 AhARF genes were identified from an allotetraploid peanut cultivar and two diploid ancestors (A. duranensis and A. ipaensis). Phylogenetic tree and gene structure analysis showed that most AhARFs were highly similar to those in the ancestors. By scanning the whole-genome for ARF-recognized cis-elements, we obtained a potential target gene pool of AhARFs, and the further cluster analysis and comparative analysis showed that numerous members were closely related to root development. Furthermore, we comprehensively analyzed the relationship between the root morphology and the expression levels of AhARFs in 11 peanut varieties. The results showed that the expression levels of AhARF14/26/45 were positively correlated with root length, root surface area, and root tip number, suggesting an important regulatory role of these genes in root architecture and potential application values in peanut breeding. [ABSTRACT FROM AUTHOR]

Variations in freshwater inflow have ecological consequences for estuaries ranging among eutrophication, flushing and transport, and high and low salinity impacts on biota. Predicting the potential effects of the magnitude and composition of inflow on estuaries over a range of spatial and temporal scales requires reliable mathematical models. The goal of this study was to develop and test a model of ecosystem processes with variable freshwater inflow to the sub-tropical Caloosahatchee River Estuary (CRE) in southwest Florida from 2002 to 2009. The modeling framework combined empirically derived inputs of freshwater and materials from the watershed, daily predictions of salinity, a box model for physical transport, and simulation models of biogeochemical and seagrass dynamics. The CRE was split into 3 segments to estimate advective and dispersive transport of water column constituents. Each segment contained a sub-model to simulate changes in the concentrations of organic nitrogen and phosphorus (ON and OP), ammonium (NH 4 + ), nitrate-nitrite (NO x − ), ortho-phosphate (PO 4 −3 ), phytoplankton chlorophyll a (CHL), and sediment microalgae (SM). The seaward segment also had sub-models for seagrasses ( Halodule wrightii and Thalassia testudinum ). The model provided realistic predictions of ON in the upper estuary during wet conditions since organic nitrogen is associated with freshwater inflow and low salinity. Although simulated CHL concentrations were variable, the model proved to be a reliable predictor in time and space. While predicted NO x − concentrations were proportional to freshwater inflow, NH 4 + was less predictable due to the complexity of internal cycling during times of reduced freshwater inflow. Overall, the model provided a representation of seagrass biomass changes despite the absence of epiphytes, nutrient effects, or sophisticated translocation in the formulation. The model is being used to investigate the relative importance of colored dissolved organic matter (CDOM) vs. CHL in submarine light availability throughout the CRE, assess if reductions in nutrient loads are more feasible by controlling freshwater quantity or N and P concentrations, and explore the role of inflow and flushing on the fates of externally and internally derived dissolved and particulate constituents. [ABSTRACT FROM AUTHOR]

Short- and long-term changes in estuarine biogeochemical and biological attributes are consequences of variations in both the magnitude and composition of freshwater inputs. A common conceptualization of estuaries depicts nutrient loading from coastal watersheds as the stressor that promotes algal biomass, decreases submarine light penetration, and degrades seagrass habitats. Freshwater inflow depresses salinity while simultaneously introducing colored dissolved organic matter (color or CDOM) which greatly reduces estuarine light penetration. This is especially true for sub-tropical estuaries. This study applied a model of the Caloosahatchee River Estuary (CRE) in southwest Florida to explore the relationships between freshwater inflow, nutrient loading, submarine light, and seagrass survival. In two independent model series, the loading of dissolved inorganic nitrogen and phosphorus (DIN and DIP) was reduced by 10%, 20%, 30%, and 50% relative to the base model case from 2002 to 2009 (2922 days). While external nutrient loads were reduced by lowering inflow ( Q 0 ) in the first series ( Q 0 series), reductions were accomplished by decreasing the incoming concentrations of DIN and DIP in the second series (NP Series). The model also was used to explore the partitioning of submarine light extinction due to chlorophyll a , CDOM, and turbidity. Results suggested that attempting to control nutrient loading by decreasing freshwater inflow could have minor effects on water column concentrations but greatly influence submarine light and seagrass biomass. This is because of the relative importance of Q 0 to salinity and submarine light. In general, light penetration and seagrass biomass decreased with increased inflow and CDOM. Increased chlorophyll a did account for more submarine light extinction in the lower estuary. The model output was used to help identify desirable levels of inflow, nutrient loading, water quality, salinity, and submarine light for seagrass in the lower CRE. These findings provide information essential to the development of a resource-based approach to improve the management of both freshwater inflow and estuarine biotic resources. [ABSTRACT FROM AUTHOR]

Abstract: Significant reductions in pollutant loadings can be achieved through coordinated operation of constructed wetlands or stormwater treatment areas (STAs) when connected to retention reservoirs for maintaining ideal water levels and hydraulic residence times in STAs that maximize treatment efficiency. Reservoir-assisted STA systems can provide additional benefits including maintenance of target frequency distributions of stormwater inflows into coastal estuarine systems for ecosystem rehabilitation, dry season flow augmentation in coastal riverine systems for maintaining the lower salinity zone, and supplemental water supply. An implicit stochastic optimization approach is applied to adaptive, multiobjective control of interconnected reservoir-assisted STAs that optimizes fuzzy rule-based operating rules using a genetic algorithm interacting with a simulation model of the stormwater drainage system. The model is applied to the four interconnected reservoir/STAs in the design configuration of the Indian River Lagoon-South project for the St. Lucie River watershed and estuary, South Florida. Results of simulated long-term performance of the optimal operating rules show attainment of targets for remediation of the aquatic ecology of the St. Lucie estuary, riverine environmental protection, and reliable supplemental water supply. [Copyright &y& Elsevier]

Peanut (Arachis hypogaea L.) is an important source of oil and food around the world, and the testa color affects its appearance and commercial value. However, few studies focused on the mechanism of pigment formation in peanut testa. In this study, cultivars Shanhua 15 with pink testa and Zhonghua 12 with red testa were used as materials to perform the combined analysis of transcriptome and metabolome. A total of 198 flavonoid metabolites were detected, among which petunidin 3-O-glucoside and cyanidin O-acetylhexoside in Zhonghua12 were 15.23 and 14.72 times higher than those of Shanhua 15 at the R7 stage, revealing the anthocyanins underlying the red testa. Transcriptome analysis showed that there were 6059 and 3153 differentially expressed genes between Shanhua 15 and Zhonghua 12 in different growth periods, respectively. These differentially expressed genes were significantly enriched in the flavonoid biosynthesis, biosynthesis of secondary metabolites, and metabolic pathways. Integrated analysis of transcriptome and metabolome indicated CHS gene (arahy.CM90T6), F3 ′ H genes (arahy. 8F7PE4 and arahy. K8H9R8), and DFR genes (arahy. LDV9QN and arahy. X8EVF3) may be the key functional genes controlling the formation of pink and red testa in peanut. Transcription factors MYB (arahy.A2IWKV, arahy.US2SKM, arahy.SJGE27, arahy.H8DJRL, and arahy.PR7AYB), bHLH (arahy.26781N, arahy.HM1IVV, and arahy.MP3D3D), and WD40 (arahy.L6JJW9) in the biosynthetic pathway of anthocyanin were significantly upregulated in Zhonghua 12 which may be the key regulatory genes in testa pigment formation. This is a comprehensive analysis on flavonoid metabolites and related genes expression in peanut testa, providing reference for revealing the regulatory mechanism of pigment accumulation in peanut testa. [ABSTRACT FROM AUTHOR]

Compared with other crops, peanut planting costs are lower, and it is very drought-tolerant, and can obtain better benefits. In this paper, 16 peanut varieties were selected, and drought resistance tests were carried out at the flowering and cutting stage under water stress conditions. The root characteristics related to drought resistance of peanuts and the physiological mechanism of drought resistance of different varieties were studied to screen peanut varieties with better drought resistance. According to the relative value (RV) of each trait, the drought resistance coefficient (DC) and drought resistance are calculated. The results show that A596, NC6, Shanhua11 and shanhua7 have strong drought resistance, Shanhua12, Nongda 818, Shanhua 8, Huayu 20, Haihua 1, 79266, Shanhua 9, Hua 17 have moderate drought resistance, while Jihua 4, Guihua 836 , ICG6848 and Baisha1016 have weaker drought resistance. [ABSTRACT FROM AUTHOR]

Aims: Determining the soil factors that drive the dynamics of soil-borne pathogens is an essential step toward the formulation and implementation of strategies for the control of plant diseases. Methods: We sampled 48 healthy and infected soils in peanut fields from six counties in Eastern China to explore the relationships between soil multifunctionality, microbial communities, and peanut stem rot pathogen, Athelia rolfsii. Results: The results showed that peanut stem rot infection did not affect soil microbial richness, but it increased soil multifunctionality, altered the microbial community composition, and decreased the complexity of microbial co-occurrence networks significantly. Soil biotic and abiotic factors had markedly effects on A. rolfsii, and specific soil functions and microbial taxa were significantly associated with A. rolfsii abundance. Soil multifunctionality and microbial community compositions negatively affected A. rolfsii abundance, while the effects of bacterial and fungal richness were contrasting for healthy and infected soils. Longitude and latitude indirectly and positively affected A. rolfsii abundance. Conclusions: The results demonstrate that soil multifunctionality and microbial communities play a vital role in regulating the dynamics of peanut stem rot pathogen, which could enhance our understanding of the relationships between soil factors, pathogen dynamics, and plant health. [ABSTRACT FROM AUTHOR]

It's well known that the development and distribution of roots could be regulated to obtain deep soil resource and enhance the grain yield by increasing the depth of fertilization, but little is known about whether increasing P fertilization depth can optimize the root distribution to delay leaf senescence, enhance photosynthetic performance and root-shoot coordination or not. We conducted a field experiment that tested the following four placement depths of P fertilization: 5 cm (P 5), 10 cm (P 10), 15 cm (P 15), and 20 cm (P 20). The experiment was designed to explore the regulatory effects of the P fertilization depth on the root growth and distribution, the photosynthetic performance, the root-shoot coordination, the yield formation, the N and P fertilizer utilization of maize plants. We found that deep P placement did indeed alter the root parameters. In the 20–60 cm soil layer, both the root dry weight and length of P 15 treatment were on average 23.2% higher than those of P 5 treatment. The specific root length and specific root surface area of P 15 treatment were 4.5% and 5.6% higher than those of P 5 treatment. In addition, the P 15 treatment achieved a significantly improved photosynthetic performance over the P 5 treatment: The leaf area index at the R6 stage was 10.2% higher, the leaf senescence index from the R2 to the R6 stages was 31.4% lower, the photosynthetic rate at the R3 stage was 25.9% higher. The P placement depth also optimized the root-shoot coordination: The ratios of root weight to shoot weight, root surface area to leaf area, and root length to leaf area of P 15 treatment were 6.7%, 13.8%, and 12.7% higher than those of P 5 treatment, respectively. Finally, the root P and N uptake efficiency, the photosynthetic P-use efficiency, and the physiological P-use efficiency of P 15 treatment were all significantly higher than those of P 5 treatments. And together these responses had the effect of increasing the mature biomass by 12.5%, and the grain yield by 22.0%. In conclusion, increasing the P fertilization placement depth to 15 cm regulates the growth and development of the root system, which in turn improves the capability of plant to uptake and utilize N and P in the soil, delays the onset of leaf senescence, enhances its photosynthetic performance and biomass accumulation rate, and thus ultimately increases the yield. [Display omitted] • Deep P fertilization optimizes root growth, and root-shoot coordination. • Deep P fertilization delays leaf senescence and improves photosynthetic performance. • Optimized root-shoot coordination improves the grain yield and nutrient use efficiency. [ABSTRACT FROM AUTHOR]

Variations in long-term precipitation trends due to climate forcings have been observed in many parts of the world, exacerbating hydrological uncertainties to predicting droughts, floods, water resource availability, and ecosystem services. The Lower Mississippi River Alluvial Valley (LMRAV) is an important economic region of the midsouth USA, which is prone to natural disasters from extreme climate events and is known historically for cyclic flooding events and, within the last 20 years, for groundwater level declines. However, our knowledge of long-term precipitation trends in this region is fragmented. Using 100-year historic daily precipitation data from six stations of forest lands along with multivariate statistical analysis, we found that there were significant increasing trends (p ≤ 0.05) in annual precipitation near the south coastal area of the LMRAV and only marginally increasing trends in the northern area. Spatial variation in seasonality was observed at the decadal scale with increasing trends in fall near the coastal area and in spring around the north area. In addition to becoming wetter, the coastal area also experienced higher precipitation intensity with shorter return period over the past 100 years. These findings are useful to water resource managers for adapting to changing climate conditions in the LMRAV. [ABSTRACT FROM AUTHOR]

The use of controlled-release urea (CRU) has become one of best management practices for increasing crop yield and improving nitrogen (N) use efficiency (NUE). However, the effects of CRU on direct-seeded rice are not well understood while direct-seeding has gradually replaced transplanting due to increasing labor cost and lack of irrigation water. The objective of this two-year field experiment was to compare the effects of the CRU at four rates (120, 180, 240 and 360 kg N ha −1 , CRU1, CRU2, CRU3 and CRU4, respectively) with a conventional urea fertilizer (360 kg N ha −1 ; U) and a control (no N fertilizer applied; CK) on yield, biomass, NUE of direct-seeded rice and soil nutrients. The results indicated that the successive release rates of N from CRU corresponded well to the N requirements of rice. The use of CRU3 and CRU4 increased rice grain yields by 20.8 and 28.7%, respectively, compared with U. In addition, the NUEs were improved by all CRU treatments compared to the U treatment. Concentrations of NO 3 − -N and NH 4 + -N in the soil were increased, especially during the later growth stages of the rice, and the leaching of N was reduced with CRU treatments. In conclusion, applying CRU on direct-seeded rice increased the crops yields and NUE, increased nitrogen availability at the late growth stages, and reduced N leaching. [ABSTRACT FROM AUTHOR]

A vast amount of future climate scenario datasets, created by climate models such as general circulation models (GCMs), have been used in conjunction with watershed models to project future climate variability impact on hydrological processes and water quality. However, these low spatial-temporal resolution datasets are often difficult to downscale spatially and disaggregate temporarily, and they may not be accurate for local watersheds ( i.e ., state level or smaller watersheds). This study applied the US-EPA (Environmental Protection Agency)’s Climate Assessment Tool (CAT) to create future climate variability scenarios based on historical measured data for local watersheds. As a case demonstration, CAT was employed in conjunction with HSPF (Hydrological Simulation Program-FORTRAN) model to assess the impacts of the potential future extreme rainfall events and air temperature increases upon nitrate-nitrogen (NO 3 -N) and orthophosphate (PO 4 ) loads in the Lower Yazoo River Watershed (LYRW), a local watershed in Mississippi, USA. Results showed that the 10 and 20% increases in rainfall rate, respectively, increased NO 3 -N load by 9.1 and 18% and PO 4 load by 12 and 24% over a 10-year simulation period. In contrast, simultaneous increases in air temperature by 1.0 °C and rainfall rate by 10% as well as air temperature by 2.0 °C and rainfall rate by 20% increased NO 3 -N load by 12% and 20%, and PO 4 load by 14 and 26%, respectively. A summer extreme rainfall scenario was created if a 10% increase in rainfall rate increased the total volume of rainwater for that summer by 10% or more. When this event occurred, it could increase the monthly loads of NO 3 -N and PO 4 , by 31 and 41%, respectively, for that summer. Therefore, the extreme rainfall events had tremendous impacts on the NO 3 -N and PO 4 loads. It is apparent that CAT is a flexible and useful tool to modify historical rainfall and air temperature data to predict climate variability impacts on water quality for local watersheds. [ABSTRACT FROM AUTHOR]

This study was to investigate peanut response to application of nitric oxide (NO) at different growth stages and the effects of NO application on peanut yield and quality in calcareous soil. Sodium nitroprusside (SNP, a NO donor) solution was poured into calcareous soil at sowing, seedling, flowering, and podding stages, respectively, or at each aforesaid critical stage. Results showed that NO application increased the content of active Fe and leaf chlorophyll, which improved the photosynthesis of peanut; enhanced the ability of resistance to oxidative stress by decreased the accumulation of O2•−, H2O2, and MDA and increased the activity of antioxidant enzymes. Nitric oxide increased the content of soil available Fe and root FCR activity, which can promote peanut absorb more Fe from the calcareous soil. What's more, peanut plants may pump a large amount of H+ from root cell membrane to consume in neutralization of HCO3−, and decrease the pH in apoplast, cytoplasm, and xylem, finally balance the mineral elements (Fe, Ca, Mg, Zn, and Cu) uptake and distribution. These results indicated that NO could improve peanut growth and development, increase peanut yield and quality. Furthermore, the application of NO at sowing or seedling stage did the most obvious effect on alleviating chlorosis of peanut in calcareous soil. [ABSTRACT FROM AUTHOR]

Biochar application as a soil amendment has been proposed as a strategy to improve soil fertility and increase crop yields. However, the effects of successive biochar applications on cotton yields and nutrient distribution in soil are not well documented. A three-year field study was conducted to investigate the effects of successive biochar applications at different rates on cotton yield and on the soil nutrient distribution in the 0–100 cm soil profile. Biochar was applied at 0, 5, 10, and 20 t ha-1 (expressed as Control, BC5, BC10, and BC20, respectively) for each cotton season, with identical doses of chemical fertilizers. Biochar enhanced the cotton lint yield by 8.0–15.8%, 9.3–13.9%, and 9.2–21.9% in 2013, 2014, and 2015, respectively, and high levels of biochar application achieved high cotton yields each year. Leaching of soil nitrate was reduced, while the pH values, soil organic carbon, total nitrogen (N), and available K content of the 0–20 cm soil layer were increased in 2014 and 2015. However, the changes in the soil available P content were less substantial. This study suggests that successive biochar amendments have the potential to enhance cotton productivity and soil fertility while reducing nitrate leaching. [ABSTRACT FROM AUTHOR]

Phosphorous (P) concentration in stormwater runoff varies at different spatial and temporal scales. Excessive P loading from agriculture system into the St. Lucie Estuary (SLE) contributed to water quality deterioration in southern Indian River Lagoon. This study examines the spatial and temporal shifts of different P forms in runoff and storm water under different land use, water management, and rainfall conditions. Storm water samplings were conducted monthly between April 2013 and December 2014 in typical farmland and along the waterway (Canal C-24) that connects lands to the SLE. Concentrations of different P forms and related water quality variables were measured. Approximately 89% of the collected water samples contained total P (TP) concentrations exceeding the total maximum daily load (TMDL) level (0.081 mg L −1 ). Concentrations of different P forms declined from agricultural field furrows to the canal and then increased from the upstream to the downstream in the canal where urban activities dominated land use. Total dissolved P (TDP) was the predominant form of TP, followed by PO 4 -P. Speciation and concentrations of P varied with sites and sampling times, but were significantly higher in the summer months (from June to September) than in the winter. Water pH explained ∼20% of TP variation. Spatiotemporal variations of P concentrations and compositions provide a data-based guide for development of best management practices (BMPs) to minimize P export from the SLE watershed. [ABSTRACT FROM AUTHOR]

Salicylic acid (SA) and nitric oxide (NO), which are known as important signaling molecules in plants, could be promising compounds for the reduction in stress sensitivity. The aim of the present work was to study the physiological changes in peanut (Arachis hypogaea L.) seedlings grown in growth medium that contained 0.1 mM SA, 0.25 mM sodium nitroprusside (SNP, a NO donor), or in full (SA+SNP) or half [1/2 (SA+SNP)] combined strengths under iron (Fe) deficiency. After 21 days of treatment, Fe deficiency significantly inhibited peanut plant growth, destroyed photosynthetic system, and caused oxidative damages. Addition of SA, SNP, and 1/2 (SA+SNP), especially SA+SNP, alleviated the stress, increased the contents of chlorophylls, and promoted plant growth. They improved Fe uptake, transport, and availability in peanut plants by increasing the activities of H+-ATPase and ferric chelate reductase (FCR), and promoting Fe translocation from cell wall to cell organelle and soluble fraction in leaves. Furthermore, they also effectively mitigated oxidative damages by increasing the activities of antioxidant enzymes in peanut leaves and roots. The results from the present study indicate that application of SA, SNP, or 1/2 (SA+SNP) can overcome the adverse effect of Fe deficiency, but the combined application of SA+SNP is more effective in alleviating Fe deficiency stress. [ABSTRACT FROM AUTHOR]

In this study, biochar derived from bamboo pretreated with aluminum salt was synthesized for the removal of two sulfonamide antibiotics, sulfamethoxazole (SMX) and sulfapyridine (SPY), from wastewater. Batch sorption experiments showed that Al-modified bamboo biochar (Al-BB-600) removed both sulfonamides effectively with the maximum sorption capacity of 1200–2200 mg/kg. The sorption mechanism was mainly controlled by hydrophobic, π-π, and electrostatic interactions. Fixed bed column experiments with Al-modified biochar packed in different dosages (250, 500 and 1000 mg) and flow rates (1, 2 and 4 mL/min) showed the dosage of 1000 mg and flow rate of 1 mL/min performed the best for the removal of both SMX and SPY from wastewater. Among the breakthrough (BT) models used to evaluate the fixed bed filtration performance of Al-BB-600, the Yan model best described the BT behavior of the two sulfonamides, suggesting that the adsorption process involved multiple rate-liming factors such as mass transfer at the solid surface and diffusion Additionally, the Bed Depth Service Time (BDST) model results indicated that Al-BB-600 can be efficiently used in fixed bed column for the removal of both SMX and SPY in scaled-up continuous wastewater flow operations. Therefore, Al-modified biochar can be considered a reliable sorbent in real-world application for the removal of SMX and SPY from wastewater. [Display omitted] • Fixed bed column packed with Al-modified biochar effectively removed SMX and SPY from wastewater. • SMX and SPY adsorption on Al-modified biochar was controlled by multiple mechanisms. • Yan model best described the breakthrough behaviors of SMX and SPY. • BDST model showed a strong linear relationship between service time and the amount of Al-modified biochar. [ABSTRACT FROM AUTHOR]

Complex simulation models are a valuable tool to inform nutrient management decisions aimed at reducing hypoxia in the northern Gulf of Mexico, yet simulated hypoxia response to reduced nutrients varies greatly between models. We compared two biogeochemical models driven by the same hydrodynamics, the Coastal Generalized Ecosystem Model (CGEM) and Gulf of Mexico Dissolved Oxygen Model (GoMDOM), to investigate how they differ in simulating hypoxia and their response to reduced nutrients. Different phytoplankton nutrient kinetics produced 2–3 times more hypoxic area and volume on the western shelf in CGEM compared to GoMDOM. Reductions in hypoxic area were greatest in the western shelf, comprising 72% (∼4,200 km2) of the total shelfwide hypoxia response. The range of hypoxia responses from multiple models suggests a 60% load reduction may result in a 33% reduction in hypoxic area, leaving an annual hypoxic area of ∼9,000 km2 based on the latest 5-yr average (13,928 km2). • Complex model formulations significantly altered outcomes of hypoxia simulations. • Hypoxic area and volume varied spatially across the shelf between two models. • Hypoxia responded differently to reduced nutrient load scenarios between models. • Models must be evaluated in context with multiple models to inform decision making. [ABSTRACT FROM AUTHOR]

The South Florida landscape is highly engineered featuring ∼3380 km of canals, ∼1225 water control structures, >70 pumping stations, managed wetlands, densely populated coastal watersheds, and impacted estuaries. Landscape scale agricultural and urban modifications require flood control which sometimes results in the release of excess freshwater that potentially damages estuarine ecology. The Central Everglades Planning Project (CEPP) is a partnership between the U.S. Army Corps of Engineers and the South Florida Water Management District focused on restoring natural patterns of freshwater flow to the Everglades and associated estuaries. One of the primary project goals is to reduce deleterious inflows eastward to the St. Lucie Estuary (SLE) and westward to the Caloosahatchee River Estuary (CRE) by diverting freshwater south from Lake Okeechobee. Performance evaluation of the CEPP relies upon integrated modeling which links the watershed engineering projects to estuarine salinities and biotic responses. The objective of this study was to utilize seagrass and oyster models to evaluate the effectiveness of alternative inflow scenarios. There are three different scenarios: the existing condition base (ECB), the future without proposed CEPP projects (FWO) but with other landscape features that could alter freshwater inflows, and alternative 4R (ALT4R) that incorporates a suite of restoration projects including those associated with the CEPP. Each of these inflow scenarios was used to generate daily salinity time series from 1965 to 2005 at multiple locations in the SLE and CRE which were used to run site-specific seagrass and oyster models. The hydrodynamic and ecological effects of freshwater inflow were greater in the SLE compared to the much larger CRE. Predicted densities of oysters (individuals m −2 ) and seagrass (shoots m −2 ) were greater in the wet season (May–Oct) vs. the dry season (Nov–Apr) in both estuaries. Oyster and seagrass densities increased under the ALT4R inflow scenario that mitigated high inflows to the estuaries in the wet season. This result improved environmental conditions while increasing freshwater availability for other parts of the Greater Everglades and the southern estuaries such as Florida Bay and Biscayne Bay. [ABSTRACT FROM AUTHOR]