Eutrophication Of Surface Waters Research Articles

Identification of multilevel priority management areas for diffuse pollutants based on streamflow continuity in a water-deficient watershed

Agricultural diffuse pollution is, on the global scale, one of the most important causes of surface water quality deterioration and eutrophication. However, the identification of agricultural priority management areas (APMAs) for diffuse pollutants is still an ongoing challenge in water-deficient watersheds. To enhance the accuracy of identification of APMA, a modified framework for APMA identification is proposed by combining the streamflow continuity index constructed by Reliability-Resilience-Vulnerability (R-R-V) indices and the SWAT model in this paper. This novel framework was tested in Zhang River Watershed and the main results are as follows. First, the SWAT model is calibrated and validated with a good performance of the Nash-Sutcliffe efficiency (NSE) and coefficient of determination (R2)greater than 0.75 and 0.80 for both the calibration and validation periods, respectively. Second, the wet year is found to be the critical period for diffuse TN and TP output at an annual scale. Specifically, the critical loss period of TN is identified as from April to October on the monthly scale, especially in July and August. However, the critical period of TP loss is mainly concentrated in the range from July to September in Zhang River Watershed. Third, the reaches with a high streamflow continuity index(SCI) are primarily located in mid-downstream part of the watershed. The reaches are mostly characterized by relatively low SCI values due to the lack of streamflow volume in the upper reaches. Fourth, the APMAs for TN and TP for the watershed final outlet connected to the Yuecheng Reservoir are approximately distributed in two areas by considering the SCI estimation, namely the Qingzhang River sub-watershed and the mid-downstream part of the Zhuozhang River sub-watershed. Compared with the results obtained from the modified APMA framework, the main areas of TN and TP APMAs may be overestimated by 27.17 and 10.02 percentage points, respectively, using the original APMAs framework without the SCI evaluation. This revised APMA framework can be easily extended to other water-deficient watersheds for improving the efficacy of the identification and the control of agricultural diffuse pollution.

Conservation practices modify soil phosphorus sorption properties and the composition of dissolved phosphorus losses during runoff

It is well established that shallow tillage (ST) and no-tillage (NT) of cultivated soils can have higher risk of dissolved phosphorus (P) loss during runoff than conventional tillage (CT). However, quantitative descriptors of how differences in tillage practices influence soil P sorption properties and how these properties in turn influence dissolved P loss remain lacking. Moreover, the influence of tillage practices on the forms of dissolved P, particularly molybdate unreactive dissolved P (MUDP), has rarely been investigated. Thus, we simulated runoff using pilot soils that had experienced three tillage practices (CT, ST, and NT) and two types of fertilization (pig and poultry manure) for 20 years. The results indicated that shifting from CT to ST or NT changed the soil’s capacity to bind P and increased Olsen-P, Dyer-P, equilibrium P concentration (EPC0), water soluble P (WSP), and the degree of P saturation (DPSOX). The experiment confirmed that switching from CT to ST or NT could increase P loss during runoff. The increase was evident for the two fertilizations (pig manure and poultry manure) with an amplified effect for the poultry manure modality. Switching from CT to ST or NT increased the loss of MUDP, which again was higher for poultry manure fertilization, for which the percentage of MUDP increased to more than 40% of TDP. Correlations between the risk of dissolved P loss and risk assessment indicators were positive, but DPSOX was opposite predicted results to other indicators, indicating that DPSOX was not suitable for predicting the risk of dissolved P loss. Our results suggest that MUDP should be considered when assessing the risk of dissolved P loss when adopting ST and NT, since MUDP is bioavailable and thus can contribute to the eutrophication of surface water.

Multi-Soil-Layering Technology: A New Approach to Remove Microcystis aeruginosa and Microcystins from Water

Eutrophication of surface waters caused by toxic cyanobacteria such as Microcystis aeruginosa leads to the release of secondary metabolites called Microcystins (MCs), which are heptapeptides with adverse effects on soil microbiota, plants, animals, and human health. Therefore, to avoid succumbing to the negative effects of these cyanotoxins, various remediation approaches have been considered. These techniques involve expensive physico-chemical processes because of the specialized equipment and facilities required. Thus, implementing eco-technologies capable of handling this problem has become necessary. Indeed, multi-soil-layering (MSL) technology can essentially meet this requirement. This system requires little space, needs simple maintenance, and has energy-free operation and high durability (20 years). The performance of the system is such that it can remove 1.16 to 4.47 log10 units of fecal contamination from the water, 98% of suspended solids (SS), 92% of biological oxygen demand (BOD), 98% of chemical oxygen demand (COD), 92% of total nitrogen (TN), and 100% of total phosphorus (TP). The only reported use of the system to remove cyanotoxins has shown a 99% removal rate of MC-LR. However, the mechanisms involved in removing this toxin from the water are not fully understood. This paper proposes reviewing the principal methods employed in conventional water treatment and other technologies to eliminate MCs from the water. We also describe the principles of operation of MSL systems and compare the performance of this technology with others, highlighting some advantages of this technology in removing MCs. Overall, the combination of multiple processes (physico-chemical and biological) makes MSL technology a good choice of cyanobacterial contamination treatment system that is applicable in real-life conditions, especially in rural areas.

Online rapid total nitrogen detection method based on UV spectrum and spatial interval permutation combination population analysis

Rapidly and accurately detect the total nitrogen (TN) concentration is enormously important for surface water protection considering the critical role it plays in reflecting the eutrophication of surface water. However, traditional TN detection methods have to experience a tedious oxygen digestion process, which tremendously limits the detection speed of TN. To solve this problem, we propose a novel online rapid TN detection method. The transformations of nitrogenous substances during the oxidative digestion process are observed by using ultraviolet (UV) spectroscopy and the concentration of TN can be predicted by only using the variation of spectrum in the early oxygen digestion process. To select the most informative variables hidden in the collected three-dimension spectrum, a new wavelength selection algorithm called spatial interval permutation combination population analysis (siPCPA) is proposed, which considers the spatial–temporal relationships among each variable in the spectrum. By using the real surface water samples collected from Houhu Lake, Changsha, China, the effectiveness of our proposed new detection and selection methods are verified and compared with other state-of-the-art methods. As a result, the practical application experiment shows that our methods can determine the concentration of TN in 5 min with a relative error of less than 5%.

Nutrient potentiate the responses of plankton community structure and metabolites to cadmium: A microcosm study

Metal pollution is a worldwide concern and may pose risks to aquatic organisms, communities, and ecosystems. The toxic effects of metals at the organism level are relatively clear. However, their impacts at the community level are still poorly understood, especially with concurred eutrophication in surface water. In the present study, the effects of Cd on the plankton community structure and function under varying nutrient conditions were evaluated using a microcosm study. The employed concentrations of Cd and nutrient were based on the values currently measured in the freshwater ecosystem. For the plankton structure, our results showed that the Chl a concentration, the abundances of total phytoplankton, Cyanophyta, and Chlorophyta, and the abundance of Copepoda decreased by Cd consistently. The Cyanophyta Oscillatoria tenuis and Copepoda nauplius were the most sensitive species to Cd in the phytoplankton and zooplankton community, respectively. For the community effects, we found the inhibitory effects of Cd on the photosystem II (PSII) activity of phytoplankton community because of the consistent decrease in the chlorophyll fluorescence parameters (Fv/Fm, Y(Ⅱ), and ETR). Furthermore, the reductions of DOC and pH by Cd were only found in the high nutrient condition, which indicated that the toxic effects of Cd on the community structure and community metabolites were aggravated by the increased nutrient. This study emphasizes the importance of considering nutrient conditions when assessing the metal ecotoxicological effects at environmentally relevant concentrations.

Comparing microscopy and DNA metabarcoding techniques for identifying cyanobacteria assemblages across hundreds of lakes

Accurately identifying the species present in an ecosystem is vital to lake managers and successful bioassessment programs. This is particularly important when monitoring cyanobacteria, as numerous taxa produce toxins and can have major negative impacts on aquatic ecosystems. Increasingly, DNA-based techniques such as metabarcoding are being used for measuring aquatic biodiversity, as they could accelerate processing time, decrease costs and reduce some of the biases associated with traditional light microscopy. Despite the continuing use of traditional microscopy and the growing use of DNA metabarcoding to identify cyanobacteria assemblages, methodological comparisons between the two approaches have rarely been reported from a wide suite of lake types. Here, we compare planktonic cyanobacteria assemblages generated by inverted light microscopy and DNA metabarcoding from a 379-lake dataset spanning a longitudinal and trophic gradient. We found moderate levels of congruence between methods at the broadest taxonomic levels (i.e., Order, RV=0.40, p < 0.0001). This comparison revealed distinct cyanobacteria communities from lakes of different trophic states, with Microcystis, Aphanizomenon and Dolichospermum dominating with both methods in eutrophic and hypereutrophic sites. This finding supports the use of either method when monitoring eutrophication in lake surface waters. The biggest difference between the two methods was the detection of picocyanobacteria, which are typically underestimated by light microscopy. This reveals that the communities generated by each method currently are complementary as opposed to identical and promotes a combined-method strategy when monitoring a range of trophic systems. For example, microscopy can provide measures of cyanobacteria biomass, which are critical data in managing lakes. Going forward, we believe that molecular genetic methods will be increasingly adopted as reference databases are routinely updated with more representative sequences and will improve as cyanobacteria taxonomy is resolved with the increase in available genetic information.

Microbial Nitrogen Transformation Potential in Sediments of Two Contrasting Lakes Is Spatially Structured but Seasonally Stable.

ABSTRACTThe nitrogen (N) cycle is of global importance, as N is an essential element and a limiting nutrient in terrestrial and aquatic ecosystems. Excessive anthropogenic N fertilizer usage threatens sensitive downstream aquatic ecosystems. Although freshwater lake sediments remove N through various microbially mediated processes, few studies have investigated the microbial communities involved. In an integrated biogeochemical and microbiological study on a eutrophic and oligotrophic lake, we estimated N removal rates from pore water concentration gradients in sediments. Simultaneously, the abundance of different microbial N transformation genes was investigated using metagenomics on a seasonal and spatial scale. We observed that contrasting nutrient concentrations in sediments were associated with distinct microbial community compositions and significant differences in abundances of various N transformation genes. For both characteristics, we observed a more pronounced spatial than seasonal variability within each lake. The eutrophic Lake Baldegg showed a higher denitrification potential with higher nosZ gene (N2O reductase) abundances and higher nirS:nirK (nitrite reductase) ratios, indicating a greater capacity for complete denitrification. Correspondingly, this lake had a higher N removal efficiency. The oligotrophic Lake Sarnen, in contrast, had a higher potential for nitrification. Specifically, it harbored a high abundance of Nitrospira, including some with the potential for comammox. Our results demonstrate that knowledge of the genomic N transformation potential is important for interpreting N process rates and understanding how the lacustrine sedimentary N cycle responds to variations in trophic conditions.IMPORTANCE Anthropogenic nitrogen (N) inputs can lead to eutrophication in surface waters, especially in N-limited coastal ecosystems. Lakes effectively remove reactive N by transforming it to N2 through microbial denitrification or anammox. The rates and distributions of these microbial processes are affected by factors such as the amount and quality of settling organic material and nitrate concentrations. However, the microbial communities mediating these N transformation processes in freshwater lake sediments remain largely unknown. We provide the first seasonally and spatially resolved metagenomic analysis of the N cycle in sediments of two lakes with different trophic states. We show that lakes with different trophic states select for distinct communities of N-cycling microorganisms with contrasting functional potentials for N transformation.

Integrated bio- and chemostratigraphy of the Cretaceous – Paleogene boundary interval in the Zagros Basin (Iran, central Tethys)

An expanded Upper Cretaceous – Lower Paleocene succession, which encompasses the Cretaceous – Paleogene boundary (K – Pg), was studied in detail from the Zagros Basin (southwest Iran, central Tethys). In order to characterize the K – Pg transition, high resolution sampling was performed in the upper part of the Gurpi Formation. The studied interval consists of dark grey marly shales and marls with interbedded limestones. Based on calcareous nannofossils, the studied section is attributed to calcareous nannofossil zones CC26b to NP3 (latest Maastrichtian – early Paleogene). High relative abundances of the nannofossil species Micula staurophora (= Micula decussata) in the Maastrichtian part (CC26) might delineate cool surface water conditions, which are followed by an increase in abundance of Micula murus about 2 m below the K – Pg boundary. Reworked Cretaceous taxa were found at the K – Pg boundary and in the overlying Danian (NP 1–3). These findings hamper a reliable determination of the last occurrence of Cretaceous calcareous nannofossil taxa at the K – Pg boundary. The K – Pg boundary is located in the uppermost part of a positive carbon isotope excursion. Diversity and absolute abundances of calcareous nannofossils show a significant decrease at the K – Pg boundary. A bloom of the dinoflagellate cyst Cervisiella operculata (formerly Thoracosphaera operculata), which is indicating environmental stress, is recorded slightly below the boundary. Throughout the lowermost Danian (NP1), the assemblages are dominated by a bloom of small species like Neobiscutum romeinii, Neobiscutum parvulum, Futyania petalosa and small Cruciplacolithus primus. These taxa indicate stressful, and eutrophic surface water conditions throughout the initial recovery phase. The Dan-C2 and Lower C29n events, recorded in the lower Danian NP1 and lower NP2 biozones, are marked by negative carbon isotope excursions. High relative abundances of Prinsius dimorphosus followed by a Coccolithus pelagicus bloom in the full recovery phase (middle Danian, NP 3), are attributed to a short term cooling phase followed by warm surface water environments recorded along with the highest absolute abundance of calcareous nannofossils.

Synergistic process using calcium peroxide and ferrous iron for enhanced ultrafiltration of Microcystis aeruginosa-laden water

Algal blooms and eutrophication in natural surface water not only pose a threat to human health, but also adversely affect the water purification process. Ultrafiltration (UF) has been proved to be effective for the retention of algal cells, but its further application is still restricted by the relatively limited removal of algal organics and membrane fouling. To enhance the UF performance, a synergistic process using calcium peroxide and ferrous sulfate (CaO2/FeSO4) was proposed for the treatment of Microcystis aeruginosa-laden water. The results suggested that the removal of algal cells and organics, fluorescent components were effectively increased with the synergism of CaO2 and FeSO4. The particle size distribution and morphology revealed that the size of algal pollutants apparently increased due to the formation of algal flocs. With CaO2/FeSO4 pretreatment, the terminal specific flux of polyethersulfone and polyvinylidene fluoride membranes were increased by 75.0% and 56.5%, individually. The fouling resistances were significantly reduced, and the fouling mechanism transition to cake filtration was delayed. The membrane interface properties including morphologies and functional groups were characterized, further verifying the effectiveness. The in-situ formed Fe3+ integrated with Ca(OH)2 showed excellent coagulation effect, thus promoting the agglomeration of algal foulants. Simultaneously, the generated hydroxyl radical could improve the oxidative degradation of algal organics. In conclusion, the CaO2/FeSO4 strategy has great advantages and application prospects in enhancing UF performance for Microcystis aeruginosa-laden water treatment.

Long-Term Biosolids Application on Land: Beneficial Recycling of Nutrients or Eutrophication of Agroecosystems?

The impact of repeated application of alkaline biosolids (sewage sludge) products over more than a decade on soil concentrations of nutrients and trace metals, and potential for uptake of these elements by crops was investigated by analyzing soils from farm fields near Oklahoma City. Total, extractable (by the Modified Morgan test), and water-soluble elements, including macronutrients and trace metals, were measured in biosolids-amended soils and, for comparison, in soils that had received little or no biosolids. Soil testing showed that the biosolids-amended soils had higher pH and contained greater concentrations of organic carbon, N, S, P, and Ca than the control soils. Soil extractable P concentrations in the biosolids-amended soils averaged at least 10 times the recommended upper limit for agricultural soils, with P in the amended soils more labile and soluble than the P in control soils. Several trace elements (most notably Zn, Cu, and Mo) had higher total and extractable concentrations in the amended soils compared to the controls. A radish plant assay revealed greater phytoavailability of Zn, P, Mo, and S (but not Cu) in the amended soils. The excess extractable and soluble P in these biosolids-amended soils has created a long-term source of slow-release P that may contribute to the eutrophication of adjacent surface waters and contamination of groundwater. While the beneficial effects of increased soil organic carbon on measures of “soil health” have been emphasized in past studies of long-term biosolids application, the present study reveals that these benefits may be offset by negative impacts on soils, crops, and the environment from excessive nutrient loading.

Whole Farm Performance of Centrifuge Extraction of Phosphorus from Dairy Manure

HighlightsA centrifuge can be used to extract manure phosphorus to a more concentrated form for easier transport.Extraction for more efficient transport to distant cropland reduced production costs in a scraped manure system.Use of a centrifuge in a flush manure system was less practical and economical due to handling of much more material.The cost of producing highly concentrated phosphorus material for export was greater than phosphate fertilizer prices.Abstract. As the size of dairy farms has increased, feeds produced on the farm as well as those purchased from off-farm sources can be transported long distances to feed the herd. Transporting the manure back to the cropland used to produce the feed can be difficult and uneconomical. Technology such as a centrifuge can be used to extract nutrients into a more concentrated form for more efficient transport. A dairy farm with 2000 cows and 1400 ha of land in Pennsylvania was simulated with the Integrated Farm System Model to evaluate the feasibility of extracting phosphorus (P) to reduce transport requirements on farm or to produce a concentrated P product for off-farm use. On this farm where manure must be transported to distant cropland to obtain uniform distribution, P extraction with a centrifuge provided a better ratio of nitrogen and P contents for use on nearby cropland and reduced transport costs for nutrients applied to more distant cropland. The centrifuge was found to be more practical and economical when used with manure scraped from the barn floor than with flushed manure because much less material was handled. Moving less material through the centrifuge both improved extraction efficiency and reduced electricity consumption, providing more economical P extraction. To avoid long-term accumulation of soil P on the farm with less land (2000 cows and 1100 ha) where concentrate feed (27% of total feed) was imported, centrifuge extraction provided a material with a high P concentration exported from the farm for other uses. Extracting the P for off-farm use cost about $2.51/kg P, which was greater than the price of phosphate fertilizer, but the extract also included other nutrients and micronutrients of value to crops. A centrifuge provides a useful tool for extracting and concentrating manure P, but the economic benefit to the producer depends upon the value of the full array of nutrient contents in the product, other manure handling practices, and the end use of the extracted material. Reducing the risk of eutrophication of surface waters provides additional benefit to society. Keywords: Dairy farm, Integrated Farm System Model, Manure handling, Manure management.

Emissions of Gaseous Pollutants from Pig Farms and Methods for their Reduction – A Review

Abstract Agriculture contributes significantly to anthropogenic emissions of greenhouse gases (GHG). Livestock production, including pig production, is associated with several gaseous pollutants released into the atmosphere, including carbon dioxide (CO2), methane (CH4), ammonia (NH3) and nitrous oxide (N2O). Emissions of volatile organic compounds (VOCs), including alcohols, aldehydes, and aromatic and aliphatic hydrocarbons, as well as typically odorous pollutants, are an inseparable element of raising and breeding farm animals. These emissions can degrade local and regional air quality, contribute to surface water eutrophication and acid rain, and increase the greenhouse gas footprint of the production sector. The paper is organized as follows. First, the sources and factors influencing the level of emissions from pig houses are described. Next, the effects of dietary methods (optimization of animal diets), hygienic methods (including microclimate optimization) and technological methods (application of technological solutions) for mitigating emissions from pigs are discussed.

Spatiotemporal distribution characteristics and key sources of nitrogen pollution in a typical agricultural watershed based on SWAT model

水资源恶化、水体富营养化严重威胁生态环境健康，农业活动所产生的氮是造成水污染的主要原因之一.本研究以句容水库农业流域为研究对象，基于实地监测数据验证了SWAT模型模拟当地氮污染的适用性，并分析了氮素负荷的时空分布特征及其关键源.结果表明：硝态氮（NO₃^--N）和总氮（TN）的年均入库量分别为9.98和27.22 t.时间尺度上，入库氮素负荷量年际呈现“M”型波动趋势；年内主要集中在汛期（6—9月），汛期氮素负荷量占到全年的84%以上.空间尺度上，径流NO₃^--N负荷量和TN负荷量均呈现“局部集中，临近水体”的分布特征，主要集中在农田占比高的地区.流域入库TN负荷量主要来源是农田施肥，贡献率达49.60%.研究结果可为当地流域氮污染控制提供理论依据.;The deterioration of water resources and surface water eutrophication threaten the health of the ecological environment seriously. Nitrogen (N) pollution from agricultural activities is an important source of water pollution. In this study, the Jurong Reservoir agricultural watershed was taken as the research object, and the local applicability of the SWAT model for N pollution was validated based on field monitoring data. In addition, the spatial and temporal distribution characteristics of N load and key pollution sources were analyzed. During the monitoring period, the annual N load showed an M type fluctuation trend, with a high N load occurred in the flood season from June to September, which accounted for more than 84% of the total N load of the whole year. Moreover, the spatial distribution of nitrate nitrogen (NO₃^--N) and total nitrogen(TN) load showed a trend of local concentration, adjacent to water body, mainly concentrated in the area with a high proportion of farmland. Farmland fertilizer is the main source of TN load in this watershed, contributing to 49.60% of total N load and the average annual storage capacity of NO₃^--N and TN was 9.98 t and 27.22 t, respectively. Our results can serve as a theoretical basis for the control of N pollution at the watershed scale.

Groundwater phosphorus concentrations: global trends and links with agricultural and oil and gas activities

Although observations show that anthropogenic phosphorus (P) can reach groundwater supplies, there has been no comprehensive evaluation of P in groundwater at the global scale and P contamination from sources such as agriculture and oil and gas activities are poorly understood. We compile and analyze 161 321 groundwater P measurements in 12 different countries to determine the extent of P contamination at the global scale. We find that all 12 countries report groundwater samples with concentrations >0.1 mg P l−1, a concentration at which the risk for eutrophication of surface waters is high. In Canada and the United States (US), we perform an analysis of 1529 dissolved oxygen (DO) concentrations to determine the degree of association between DO and groundwater P measurements. For P concentrations <0.1 mg P l−1, we find a strong inverse relationship between DO and P. However, for P concentrations >0.1 mg P l−1, we find a weak inverse correlation, which suggests anthropogenic sources are responsible for elevated P concentrations in groundwater. To identify anthropogenic sources of P, we conduct an analysis on land use data and the 24 146 P concentrations in Canada and the US. Although we find that 12% (2899) of all P concentrations are >0.1 mg P l−1, 33% of P concentrations from P monitoring sites located on pastureland (managed grassland) report concentrations >0.1 mg P l−1. In Alberta and Ontario, we analyze P measurements with respect to their proximity to oil and gas wells and find the relationship to be inconclusive. Overall, we find a positive correlation with agriculture and elevated groundwater P concentrations, but additional data are needed to identify a relationship between oil and gas wells and elevated groundwater P concentrations. Characterizing the role of agriculture and oil and gas wells on groundwater P contamination can help regulators develop effective strategies to protect water quality and ecosystem health.

Excessive application of chemical fertilizer and organophosphorus pesticides induced total phosphorus loss from planting causing surface water eutrophication

Total phosphorus (TP) loss from planting was one of the resources causing agricultural non-point source pollution. It is significant to clarify the factors influencing TP loss, as well as explore the relationship between TP loss from planting and surface water eutrophication for making recommendations on the reduction of environmental pollution. In this study, the minimum and maximum of average TP loss was appeared in Qinghai and Shandong province with the TP loss of 7.7 × 102 t and 7.5 × 103 t from 2012 to 2014, respectively. The results of structural equation model (SEM) indicating that the effect of anthropogenic drivers on TP loss was more important than natural conditions due to the higher path coefficient of anthropogenic drivers (0.814) than that of natural conditions (0.130). For anthropogenic drivers, the path coefficients of usage of fertilizer and pesticides, which was often excessively applied in China, were 0.921 and 0.909, respectively causing they the two dominant factors affecting TP loss. Annual precipitation and relative humidity, which were belongs to natural conditions, increased TP loss by enhancing leaching and surface runoff. However, light duration could reduce TP loss by promoting crop growth and increasing TP absorption of crops, with a path coefficient of − 0.920. TP loss of each province in per unit area from planting was significantly correlated with TP concentration of its surface water (p < 0.05), suggesting that TP loss from planting was the main factor causing surface water eutrophication. This study targeted presented three proposals to reduce the TP loss from planting, including promotion of scientific fertilization technologies, restriction of organophosphorus pesticides, and popularization of water saving irrigation technologies. These findings as well as suggestions herein would provide direction for the reduction of TP loss from planting.

Enhanced removal of ammonium from water using sulfonated reed waste biochar-A lab-scale investigation

The removal of excessive ammonium from water is vital for preventing eutrophication of surface water and ensuring drinking water safety. Several studies have explored the use of biochar for removing ammonium from water. However, the efficacy of pristine biochar is generally weak, and various biochar modification approaches have been proposed to enhance adsorption capacity. In this study, biochar obtained from giant reed stalks (300, 500, 700 °C) was modified by sulfonation, and the ammonium adsorption capabilities of both giant reed biochars (RBCs) and sulfonated reed biochars (SRBCs) were assessed. The ammonium adsorption rates of SRBCs were much faster than RBCs, with equilibrium times of ∼2 h and ∼8 h for SRBCs and RBCs, respectively. The Langmuir maximum adsorption capacities of SRBCs were 4.20–5.19 mg N/g for SRBCs, significantly greater than RBCs (1.09–1.92 mg N/g). Physical-chemical characterization methods confirmed the increased levels of carboxylic and sulfonic groups on sulfonated biochar. The reaction of ammonium with these O-containing functional groups was the primary mechanism for the enhancement of ammonium adsorption by SRBCs. To conclude, sulfonation significantly improved the adsorption performance of biochar, suggesting its potential application for ammonium mitigation in water.

Phosphorus availability and leaching losses in annual and perennial cropping systems in an upper US Midwest landscape

Excessive phosphorus (P) applications to croplands can contribute to eutrophication of surface waters through surface runoff and subsurface (leaching) losses. We analyzed leaching losses of total dissolved P (TDP) from no-till corn, hybrid poplar (Populus nigra X P. maximowiczii), switchgrass (Panicum virgatum), miscanthus (Miscanthus giganteus), native grasses, and restored prairie, all planted in 2008 on former cropland in Michigan, USA. All crops except corn (13 kg P ha−1 year−1) were grown without P fertilization. Biomass was harvested at the end of each growing season except for poplar. Soil water at 1.2 m depth was sampled weekly to biweekly for TDP determination during March–November 2009–2016 using tension lysimeters. Soil test P (0–25 cm depth) was measured every autumn. Soil water TDP concentrations were usually below levels where eutrophication of surface waters is frequently observed (> 0.02 mg L−1) but often higher than in deep groundwater or nearby streams and lakes. Rates of P leaching, estimated from measured concentrations and modeled drainage, did not differ statistically among cropping systems across years; 7-year cropping system means ranged from 0.035 to 0.072 kg P ha−1 year−1 with large interannual variation. Leached P was positively related to STP, which decreased over the 7 years in all systems. These results indicate that both P-fertilized and unfertilized cropping systems may leach legacy P from past cropland management.

Hydrologic and Nutrient Fluxes in a Small Watershed with Changing Agricultural Practices

Nonpoint-source nutrients contribute to eutrophication of surface waters. While effects of particular management actions are difficult to identify at the watershed scale, assessing nutrient fluxes over time can illuminate the net impact of trends in land use and management. We investigated nutrient fluxes in upper Kamm Creek in northwest Washington State to determine if historical changes in land management, responding to economic and regulatory shifts, had impacted nutrient export. We compared current (October 2015 to September 2018) nitrogen and phosphorus fluxes in Kamm Creek to data from a previous study (1993 to 1998). We found significantly higher current fluxes of nitrate, and significantly lower current fluxes of orthophosphate (P) and total phosphorus (TP), compared to the historical sampling period. The increased annual nitrate flux resulted from slightly higher average discharge and significantly higher nitrate concentrations throughout the year. In contrast, current P and TP concentrations were significantly lower throughout the year than previously. The Nooksack River, which receives water from the study stream, showed similar patterns for P and TP, but not nitrate. Kamm Creek had reduced phosphorus fluxes and increased nitrate fluxes between the 1993 to1998 and 2015 to 2018 time periods. The watershed experienced several concurrent land-use changes, including reductions in hay and corn acreage, increases in berry crop acreage, legislation to reduce manure application, and altered use of nitrate-enriched groundwater. We cannot currently distinguish among these. Further understanding relationships between specific management changes and nutrient fluxes will help to maintain local agricultural productivity and improve water quality.

Removal of Nitrate Ions Using Thermally and Chemically Modified Bioadsorbents

Nitrate ions are one of the causes of surface water eutrophication. In the present research, the effective adsorption of nitrate ions (NO3) on bioadsorbents prepared from yam skins (Dioscorea alata) was evaluated. The yam skin was chemically modified with ammonium chloride (NH4Cl), and biochar was prepared from the thermally modified biomass. The results were compared with commercial coal (CC). The bioadsorbents were characterized by SEM-EDS analysis, which showed that the synthesized adsorbents have a heterogeneous surface with pores. The batch adsorption tests showed that the pH has the most significant effect on the NO3 adsorption capacity when using the modified yam skin (MYP), obtaining as best conditions pH 12 and a 0.5 mm particle size with an adsorption capacity of 25.75 mg/g; the best adsorption capacity when using the carbon synthesized from yam skin (CYP) and CC was obtained at pH 2, reaching values of 36 and 33.34 mg/g, respectively. The following performance in terms of adsorption capacity was found: CYP &gt; CC &gt; MYP, according to Langmuir’s model. The equilibrium isotherm of NO3 adsorption on MYP and CYP was adjusted by the Freundlich model, while the Langmuir model described adsorption on CC. The kinetics of all the systems studied showed a good fit to the pseudo-first-order, pseudo-second-order and Elovich models with R2 &gt; 0.95, suggesting a mechanism of chemical adsorption by means of species exchange between the aqueous phase and the surface of the material, with the intervention of an intraparticle diffusion stage; based on these findings, the studied biomasses reached promising adsorption capacities in the removal of nitrate anions, showing that the carbon synthesized from yam skins and modified with ammonium chloride had a remarkable behavior in comparison with commercial carbon and NH4Cl-modified yam skins.

Characterization of Phosphate Solubilizing Bacterial Endophytes and Plant Growth Promotion In Vitro and in Greenhouse.

Phosphate is one of the most important nutrients for plant growth and development, and only 0.1% of the phosphate in soils is available to plants. Currently, the use of excess phosphate fertilizer has caused surface and ground water pollution and water eutrophication, resulting in algal blooms in lakes and oceans. Therefore, it is imperative to explore alternative ways to solve these problems for sustainable agricultural production and improvement of soil fertility, while protecting the environment. Microorganisms from the rhizosphere and within plants are able to solubilize insoluble soil phosphate, making it available to plants. Five high phosphate solubilizing bacteria from our bacterial endophyte library were chosen for this study and identified as Pantoea vagans IALR611, Pseudomonas psychrotolerans IALR632, Bacillus subtilis IALR1033, Bacillus safensis IALR1035 and Pantoea agglomerans IALR1325. All five bacteria significantly promoted tall fescue growth in vitro. Greenhouse experiments showed that IALR1325 significantly promoted pepper and tomato growth, and IALR632 was the best in promoting tomato growth. In addition, all these bacteria had extracellular acid phosphatase and phytase activities. One of the mechanisms for phosphate solubilization by bacteria is pH reduction caused by gluconic acid production. Our results indicate that P. agglomerans IALR1325 is a promising bacterium for future applications.