Water-soluble NO3 Research Articles

Composition and Effects of Aerosol Particles Deposited on Urban Plant Leaves in Terrestrial and Aquatic Habitats.

Plants play a vital role in mitigating aerosol particles and improving air quality. This study investigated the composition characteristics and potential effects of particles retained on the leaf surfaces of two amphibious plants (i.e., Alternanthera philoxeroides and Hydrocotyle vulgaris) in both terrestrial and aquatic habitats. The results show that plant habitats influenced the composition of aerosol particles retained on leaf surfaces. Specifically, plants in terrestrial habitats retained a higher mass concentration of coarse and large particles rich in inorganic Ca2+, accounting for over 70% of total ions, whereas plants in aquatic habitats retained a greater abundance of fine and secondary particles with high fractions of water-soluble NO3- and SO42-, taking up over 65% of total anions. Secondary particles deposited on the surfaces of plants in aquatic habitats tend to deliquesce and transform from the particle phase to the liquid phase. Terrestrial habitats facilitate the deposition of large particles. Additionally, particle accumulation on leaf surfaces adversely affected the stomatal conductance of plant leaves, leading to reductions in both the transpiration and photosynthetic rates. This study provides insights into the impact and role of plants from different habitats in mitigating urban particulate pollution.

Electrocatalytic Reduction of Nitrogen Oxides By a Crystalline Carbon Nitride

Of the trillions of tons of Haber-Bosch fertilizers generated annually for global consumption, only 17% contribute to human feedstock proteins. A large fraction of Haber-Bosch nitrogen is lost as hazardous oxidized waste (N y O x ). Water-soluble NO3 – and NO2 – anions wash into aquatic ecosystems, where they feed dangerous algal blooms. The waste volatile N2O comprised nearly 7% of emissions in 2018, and has 300 times the global warming impact of CO2. Nature mediates N y O x redox through metalloheme chains aligned in enzymatic active sites. The poly(triazine imide) LiCl (PTI-LiCl) electrocatalyst mimics these heme chains through highly crystalline, layered carbon nitride nanosheets. PTI has advantages of both heterogeneous and homogeneous electrocatalysts: (i) PTI sequesters substrates as intercalants, (ii) PTI has high surface area with a known structure, and does not lose crystallinity upon introduction of abundant transition metals, (iii) PTI has an extended π system shuttles electrons to ordered active sites. PTI is active as a solid state electrocatalyst toward NO2 – reduction, with 31% Faradaic efficiency toward complete reduction to NH3. Approximately 50% of intrasheet Li+ can be exchanged with Cu2+ with no change to native crystallinity, suggesting an electrostatic interaction between PTI and Cu2+ single atoms. Remarkably, introducing Cu2+ improves the onset potential for electrocatalytic NO2 – reduction by nearly 0.5 V, and catalytic current increases by an order of magnitude. Since copper is also found at the active site in nitrous oxide reductase, CuPTI was investigated for electrocatalytic reduction of N2O. Preliminary results suggest CuPTI can electrochemically bind and reduce N2O. Figure 1

Biochar for urban agriculture: Impacts on soil chemical characteristics and on Brassica rapa growth, nutrient content and metabolism over multiple growth cycles

With possible food crises looming in the near future, urban farming, including small-scale community and home gardens for home consumption, presents a promising option to improve food security in cities. These small-scale farms and gardens often use planter boxes and raised beds filled with lightweight soil or potting mixes. While previous studies on biochar focused on its application on large-scale contiguous farmlands, this study aimed to evaluate the suitability of biochar as a partial soil substitute to produce a durable and lightweight soil-biochar mix for small-scale urban farms. The effects of biochar on the chemical properties of the soil-biochar mix, crop yield and, particularly, crop nutrients and metabolic content were assessed. A germination test using pak choi seeds (Brassica rapa L. cultivar group Pak choi, Green-Petioled Form) showed that the biochar contained phytostimulants. Through a nursery pot experiment over four growth cycles, biochar treatments performed better than pure soil at retaining water-soluble NO3− and K+ ions, but were worse at retaining PO43− ions. Nonetheless, despite its positive effect on soil NO3− retention, biochar application did not improve crop yield significantly when the application rate varied from 0% to 60% (v/v). Untargeted metabolomic analyses showed that biochar application may increase the production of carbohydrates and certain flavonoids and glucosinolates. The results of this study showed that biochar can potentially be used to improve pak choi nutritional values and applied in large quantity to obtain a lightweight soil mix for urban farming.

Role of soluble and exchangeable nitrogen pools in N cycling and the impact of nitrogen added in forest soil.

Nitrogen (N) cycle in forest soils is altered by water, salt, or acid solutions, and its internal transfers to and from each existing inorganic pools are not known comprehensively. To evaluate the soluble and exchangeable N pools, bulk soil (B soil), water-extracted soil (W soil), and the 0.5 mol L-1 K2SO4-treated soil (K soil) were incubated for up to 48 days to comprehend the dynamics of inorganic (NH4+ and NO3-) and soluble organic N (SON) in water-soluble, exchangeable, 2.5 mol L-1 H2SO4 (labile pool I, LPI) and 13 mol L-1 H2SO4 (labile pool II, LPII) pools. To test the N deposition effects, additional NH4NO3 solution was added to B, W, and K soils at amount of 40 mg N kg-1 soil. The results showed that though there was more NO3- removed when W soil was prepared, the similar net nitrification rate in W soil to B soil and more than 20 mg N kg-1 water-soluble NO3- were observed in W soil, which indicated that the loss of NO3- would be enhanced. In contrast, there was more water-soluble and exchangeable NH4+ for K soil compared with B soil. The different dynamic of NO3- between W and K soil suggested that nitrifiers might dominate in the soil matrix rather than the soil solution. After incubation, each N form in the LPI decreased, which can be attributed to the allocation of remaining N into the recalcitrant pool, except the increase of NH4+ for B soil and NO3- for K soil, and NO3- in LPII for B soil. Compared with control, N addition increased mineralization of exchangeable SON to promote nitrification regardless of soils, but weakened the immobilization of NO3-. In addition, N in LPI and LPII pools have increased, which might be related to decomposition of recalcitrant organic matter induced by N addition to transform when the water-soluble and exchangeable N was removed. Therefore, the changes of soluble and exchangeable nitrogen pools impact the N cycling. Our findings can give some explanation for whole soil N transformation responses to N deposition.

Assessing Soil Fertility Status of Edible Wild Plants Fields in Ulleung Island

The perennial edible wild plants such as Aster glehnii, Solidago virgaurea subsp. gigantean, Allium ochotense, Athyrium acutipinnulum, Aruncus dioicus var. kamtschaticus and Codonopsis lanceolata have cultivated as the main income crops introduced into the fields about 30 years ago in Ulleung island. Soil samples were collected from 190 fields and assessed the effects of management practices on soil chemical properties at wild edible plant fields under no-till system. The strong acidic soils of pH 5.4 or less were detected in 45% of the soil samples. The level of soil organic matter was being held at mean 63±28 g kg -1 , 2.7 times higher than upland soils in Korea. Available phosphate and exchangeable potassium showed more than recommended levels of upland crops as 680±489 mg kg -1 and 1.94±1.7 cmolc kg -1 , respectively. The fields of Solidago and Aster showing strong soil acidity and high level of available phosphate and water soluble NO₃ - were distinguished from other crops in analysis of variance and principal component analysis of soil chemicals. These results suggested that high frequency of acidic soil and high levels of available P₂O 5 , exchangeable K₂O and water soluble NO₃ - were accompanied with the use of urea and NPK-fertilizer based on nitrogen in the field. However, further research is needed to understand the appropriate management of fertilization and the prevention of soil acidification for wild edible plants.

Modeling Nonpoint Source Pollutant Losses from a Small Watershed Using HSPF Model

Hydrologic models play an important role in the assessment of nonpoint source (NPS) pollution, which is essential for the environmental management of water resources. The present study has been undertaken to evaluate the applicability of a physically based continuous time scale, hydrological, and water quality computer model—Hydrologic Simulation Program-Fortran (HSPF)—in simulating runoff and sediment associated NPS pollutant losses from a small mixed type (land under agriculture, shrubs and forest, rocks, grasses) watershed of the Damodar Valley Corporation, Hazaribagh, India. Water soluble NO3–N, NH4–N, and P were considered as pollutants and their concentrations in the runoff were measured at the outlet of the watershed, randomly for 15 dates during the monsoon season (June–October) of 2000 and 2001. The model calibration and validation results reveal that the seasonal trend of HSPF simulated runoff, sediment yield, and NPS pollutants compared reasonably with their measured counterparts. Although the concentrations of pollutants were generally overpredicted for NO3–N and underpredicted for NH4–N and water-soluble P in the month of June when fertilizers releasing NH4–N and P are applied in rice fields, the differences in the mean concentration were not significantly different at a 95% level of confidence. Variation in the simulated losses of water soluble N and P species between the years occurred largely due to differences in the amount and distribution of rainfall. These results indicate that the HSPF model can be used as a tool for simulating runoff and sediment associated NPS pollution losses from the study area.

Effects of spent mushroom substrate weathering on the chemistry of underlying soils.

Passive weathering of heaped material in the field is a popular method for treating spent mushroom substrate (SMS) before its reuse. During the weathering process, leachate containing high concentrations of dissolved organic matter and inorganic salts is released into the underlying soils, but effects on soil and ground water quality remain uncertain. We conducted a field study to measure the effects of SMS weathering on chemical and morphological properties of underlying soils. Two SMS piles, 20 m long, 6 m wide, and either 90 or 150 cm high, were placed in a fallow agricultural field dominated by grasses and weathered for 24 mo. Soil samples were taken from each genetic horizon under the SMS piles following their removal and analyzed for pH, total organic carbon (TOC), electrical conductivity (EC), water-soluble organic carbon (WSOC), water-soluble inorganic cations and anions, and exchangeable inorganic cations. Compared with an unaffected control, SMS weathering did not raise soil TOC, but did alter soil pH, and significantly increased EC, WSOC, and water-soluble and exchangeable inorganic ions. At 200 cm below the soil surface, the EC, WSOC, and water-soluble Cl-, NO3-, Ca2+, Mg2+, Na+, and K+ under SMS piles were 4 to 20 times higher than in unaffected soils. Water-soluble NO3- was minimal in the surface soil but peaked in the C horizon (120-180 cm) under the 90-cm SMS pile, indicating that these soils may have little capacity for retaining NO3-. Concentration profiles of the different solutes reflect their relative mobilities in the soil environment and indicate the potential for effects on subsurface water supplies.

Field evaluation of anion exchange membranes as a N soil testing method for grasslands

The in situ use of anion exchange membranes (AEMs) as a soil-testing procedure may provide a more precise evaluation of N availability to forages than standard methods. The main objective of this study was to evaluate the potential of AEMs to predict soil NO3–N availability for forage production in the western part of the province of Quebec, Canada. In 1995 and 1996, AEMs were buried (0–15 cm) in soils at four sites. The fertilizer treatments consisted of five NH4NO3 rates (0, 60, 120, 180, and 240 kg N ha–1). At all sites, NO3−sorbed on the AEMs (NO3AEMs) increased with increasing N fertilizer rates. The NO3AEMs fluxes were significantly related to water soluble NO3–N (NO3w) concentration in soil (R2 varied from 0.35 to 0.98) in the two growing seasons. Forage N uptake was better related with NO3AEMs fluxes (R2 = 0.88 and 0.92 in spring 1996 and 1995, respectively) than with NO3w concentration (R2 = 0.39 and 0.97 in spring 1996 and 1995, respectively). Based on their simplicity, rapidity, and low cost, AEMs have many practical advantages over water NO3–N extraction for assessing grass forage soil N availability in cool continental climates. Key words: Resin, nitrogen, N uptake, grass forage, N mineralization

Changes in water‐soluble and exchangeable ions, cation exchange capacity, and phosphorusmax in soils under alternating waterlogged and drying conditions

The effects of waterlogging and subsequent drying on pH, Eh, dissolved oxygen (DO), water soluble ions, exchangeable cations, cation exchange capacity (CEC), and phosphorus sorption capacity (Pmax) in three soils were studied (krasnozem, sandy loam, and highly organic material from a Melaleuca wetland). Fifty grams of each soil were mixed with 75 mL of distilled water, and left in a waterlogged state for 21 days. After removing a sample of the ponded water and sediment for analysis, the remaining water was discarded and the soils allowed to dry at room temperature for 21 days. All soils demonstrated a decrease in Eh, PO4, NO3 and DO, and an increase in pH, soluble organic carbon (SOC), iron (Fe), manganese (Mn), NH4, calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na), in the solution phase due to waterlogging, but the magnitudes of change were greatest in soils with the higher levels of organic matter. Increases in Fe and Mn were attributed to the dissolution of Fe and Mn oxides under chemically reducing conditions. Increases in Ca, Mg, K, and Na were attributed to increased solubility of organic carbon, and from increased competition for the CEC sites due to elevated Fe and Mn concentrations. Increases in CEC due to the presence of colloids with variable charge were largely balanced by Fe and Mn. Mineralization of organic nitrogen (N) by anaerobic bacteria, and the absence of DO, was considered responsible for the accumulation of water soluble NH4. Decreases in water soluble NO3 and PO4 due to waterlogging were attributed to denitrification and sorption by amorphous Fe(OH)2, respectively. Reoxidation by drying caused increases in Eh and DO, decreases in exchangeable Fe and Mn, but had no significant effect on pH, exchangeable cations or CEC. Waterlogging nearly doubled Pmax in the krasnozem A horizon and wetland soils, and produced only small changes in the other soils. Sorption by freshly precipitated Fe(OH)2 is considered the major mechanism increasing PO4 sorption.