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The Reedy River in South Carolina is affected by the urban area of Greenville, the third most populous city in the state, and by the effluents from two large-scale municipal wastewater treatment plants (WWTPs) located on the river. Riverine water chemistry was characterized using grab samples collected annually under spring season baseflow conditions. During the 4-year time period associated with this study, climatic variations included two severe drought spring seasons (2001 and 2002), one above-normal precipitation spring season (2003), and one below-normal precipitation spring season (2004). The influence of drought and human activities on the baseflow chemistry of the river was evaluated by comparing concentrations of dissolved anions, total metals, and other important water chemistry parameters for these different years. Concentrations of copper and zinc, common non-point source contaminants related to urban activities, were not substantially elevated in the river within the urban area under baseflow conditions when compared with headwater and tributary samples. In contrast, nitrate concentrations increased from 1.2–1.6 mg/l up to 2.6–2.9 mg/l through the urban stream reach. Concentrations of other major anions (e.g., sulfate, nitrate) also increased along the reach, suggesting that the river receives continuous inputs of these species from within the urban area. The highest concentrations of major cations and anions typically were observed immediately downstream from the two WWTP effluent discharge locations. Attenuation of nitrate downstream from the WWTPs did not always track chloride changes, suggesting that nitrate concentrations were being controlled by biochemical processes in addition to physical processes. The relative trends in decreasing nitrate concentrations with downstream distance appeared to depend on drought versus non-drought conditions, with biological processes presumably serving as a more important control during non-drought spring seasons. [ABSTRACT FROM AUTHOR]

Little is known about atmospheric magnesium ion (Mg2+) wet deposition in relation to soil inorganic carbon sequestration. Understanding the conversion of carbon dioxide (CO2) or organic carbon to a form having a long residence time within the soil (e.g., dolomite, magnesian calcite) will greatly benefit agriculture, industry, and society on a global scale. This preliminary study was conducted to analyze atmospheric Mg2+ wet deposition within the continental United States (U.S.) and to rank the twelve major soil orders in terms of average annual atmospheric Mg2+ wet deposition. The total average annual Mg2+ wet deposition for each soil order was estimated with geographic information systems (GIS) using the following data layers: (1) atmospheric Mg2+ wet deposition data layers covering the continental U.S. for a 10-yr period (1994–2003) and (2) a soil order data layer derived from a national soils database. A map of average annual Mg2+ wet deposition for 1994–2003 reveals that the highest deposition (0.75–1.41 kg ha−1) occurred in Oregon, Washington, parts of California, and the coastal areas of East Coast states due to magnesium enrichment of atmospheric deposition from sea salt. The Midwestern region of the U.S. received about 0.25–0.75 kg ha−1 Mg2+ wet deposition annually, which was associated with loess derived soils, occurrence of dust storms and possibly fertilization. The soil orders receiving the highest average annual atmospheric Mg2+ wet deposition from 1994 to 2003 were: (1) Mollisols (3.7 × 107 kg), (2) Alfisols (3.6 × 107 kg) and (3) Ultisols (2.8 × 107 kg). In terms of potential soil carbon sequestration, the average annual atmospheric Mg2+ wet deposition was equivalent to formation of the following theoretical amounts of dolomite: (1) Mollisols (2.8 × 108 kg of CaMg(CO3)2), (2) Alfisols (2.7 × 108 kg of CaMg(CO3)2) and (3) Ultisols (2.1 × 108 kg of CaMg(CO3)2). The soil orders receiving the lowest average annual atmospheric Mg2+ wet deposition were: (1) Andisols (3.3 × 106 kg), (2) Histosols (3.4 × 106 kg) and (3) Vertisols (5.0 × 106 kg). The methods proposed here to estimate soil inorganic carbon sequestration potential from atmospheric wet deposition data can be useful for preliminary carbon accounting on a global scale. [ABSTRACT FROM AUTHOR]

The main objectives of this research were to examine the effects of colloidal and particulate matter in freshwaters on dissolved organic carbon (DOC) and ultraviolet light absorbance at 254 nm (UV254) and to develop some guidelines for filtering freshwater samples with widely varying turbidities. More than 90% of the organic matter in the natural waters tested in this study was in the dissolved form, and filter cake formation did not have a significant impact on the DOC values of a sample. The experimental results showed that the level and characteristics of turbidity in a water sample, as well as the nature of pore structures and pore size distributions of a membrane filter selected for filtration, play important roles in UV254 and specific ultraviolet absorbance254 (SUVA254). Results indicated that when filtrate turbidities were below 0.3 ntu, filtration volume, filter cake formation, and pretreatment processes had no significant impact on DOC and UV254 determinations and thus on calculated SUVA254 values. When filtrate turbidities were >0.5 ntu, however, they increased the UV254 values (and also SUVA254) without causing an apparent impact on the DOC measurements. These findings suggest that a conservative criterion for the turbidity of a filtered UV254 sample, such as <0.3 ntu, should be adopted to minimize interferences on the results. [ABSTRACT FROM AUTHOR]

Describes potential cation-pi interactions between pi donors and exchangeable cations accumulated at mineral surfaces via both spectroscopic and batch sorption methods. Sorption of polycyclic aromatic hydrocarbons (PAH) to different minerals saturated with different cations; Molecular interactions of deuterated solutes with mineral surfaces; Sorption mechanism controlling PAH sorption to mineral surfaces.

Interactions of Ag+ with naphthalene and pyrene in aqueous solution were investigated using ultraviolet (UV) absorption and steady-state and time-resolved fluorescence spectroscopies. Small red-shifts in the two primary absorption bands of naphthalene and pyrene were observed in the presence of high concentrations of Ag+, indicating that ground-state cation–aromatic π electron interactions occurred. Ag+ complexation constants (K1 and K2) for naphthalene were determined directly from steady-state and time-resolved fluorescence data, whereas the formation of a pyrene–Ag+ exciplex required an additional correction to remove its interference on apparent pyrene complexation constants. The correction utilized ratios of the exciplex and monomer preexponential factors obtained from pyrene fluorescence decay curves measured at several emission wavelengths that were impacted to different degrees by the exciplex emission. The novel approach developed here to quantify ground-state complexes between Ag+ and polycyclic aromatic hydrocarbons (PAHs) offers new opportunities to investigate weak metal–organic complexes such as those resulting from cation–π interactions. [Copyright &y& Elsevier]

Examines the characterization of cation-π interactions in aqueous solution using deuterium nuclear magnetic resonance spectroscopy. Bond between silver and aromatic hydrocarbons; Indication of normal electrostatic interaction; Interaction between the π electrons of aromatic molecules and metal cations.

Spin-lattice relaxation times (T[sub 1]) and chemical shifts (δ) of perdeuterated pyridine (α, β, γ deuterium of d[sub 5]-pyridine) in aqueous solution (e.g., water, 0.001 M benzoic acid and phenol) are found to decrease with increasing pH values. This is because the concentration distribution of the two pyridine species, protonated and unprotonated, varies with solution pH. The T[sub 1] values of γ are lower than α and β deuterium in water and methanol compared with n-hexane, indicating more anisotropic molecular movements of pyridine resulting from interactions between amine and the polar solvent. Spin-spin relaxation times (T[sub 2]) and δ of d[sub 5]-pyridine in aqueous suspensions of water-dispersible clay (WDC) soil components are highly pH dependent. The lowest T[sub 2] and the most downfield-shifted δ compared with aqueous solution show that the strongest sorption occurs at the weak acidic condition (pH 6). The downfield shifts of δ observed in WDC suspensions are directly caused by the increased mole ratio of protonated pyridine through sorption. However, no significant changes in δ are observed for organic free minerals (H[sub 2]O[sub 2]-treated WDCs and a standard clay mineral) compared with aqueous solution, indicating interactions with mineral surfaces are negligible in pyridine sorption. A sorption mechanism of cation exchange between protonated pyridine and charged sites of soil organic matter (SOM) is inferred based on the measured δ values. [ABSTRACT FROM AUTHOR]

Examines the molecular-level sorption behavior of monoaromatic compounds in suspensions of water-dispensable clay components. Measurement of the [sup2]H nuclear magnetic resonance spin-spin relaxation times; Indication of stronger solute-sorbent interactions; Increase in the sorption of solute.

Discusses the removal of hydrophobic organic contaminants from saturated subsurface environments using a solubility-enhanced electrokinetic remediation process. Removal of phenanthrene from the model soil; Removal of phenanthrene by flushing the anode reservoir of the column with high hydroxypropyl-beta-cyclodextrin concentration.

Examines removal of sorbed hydrophobic organic compounds (HOC) by hydroxypropyl-beta-cyclodextrin (HPDC) in surfactant-enhanced subsurface remediation. Role of HOC concentration in HOC-HPCD complex formation coefficients; HPDC ability of neglecting sorption to the solid phase; Impact of HOC size and hydrophobicity on HPCD role in HOC partitioning.

The framework of ecosystem services (ES) and disservices (ED) has increasingly been used in various science, technology, engineering, and mathematics (STEM) disciplines, including soil science. The objectives of this study were to use ES/ED concepts to extend and test an existing lecture and laboratory exercise on soil organic carbon (SOC) in an online introductory soil science course (FNR 2040: Soil Information Systems) taught to Clemson University students from various STEM disciplines (forestry, wildlife biology, and environmental and natural resources) in Fall 2020. The laboratory exercise was extended with a series of reusable learning objects (RLOs), which are self-contained digital modules commonly utilized in e-learning. The laboratory exercise consisted of identifying ES and calculating the avoided social cost of carbon (SC-CO2) from soil organic carbon stocks in the assigned soil's topsoil horizon. The laboratory exercise effectively increased student familiarity with ES/ED as indicated by the post-assessment survey with a +24.4% increase in the moderately familiar category and a +36.1% increase in the extremely familiar category. The graded online quiz consisted of ten questions and was taken by 51 students with an average score of 8.7 (out of 10). A post-assessment survey indicated that most of the students found that the laboratory was an effective way to learn about ES/ED with examples from soil science. Detailed students' comments indicated enjoyment of learning (e.g., calculations, applying new knowledge), the value of multimedia (e.g., PowerPoint, video), the flexibility of learning (e.g., different parts in the laboratory), the applicability of content (e.g., real-world examples), and criticism (e.g., tedious calculations). A word cloud based on students' comments about their experience with the laboratory exercise on soil ES indicated the most common words used by students to describe their experience, such as "soil services", "learning", "enjoyed", and "ecosystems", among others. Incorporating ES/ED into an undergraduate STEM course enabled students to connect ES/ED provided by soil with the societal systems reliant on the soil resources. [ABSTRACT FROM AUTHOR]

Peroxyoxalate chemiluminescence (PO-CL) spectra obtained simultaneously and continuously using a CCD spectrometer provide evidence of the complexity of PO-CL reactions. [ABSTRACT FROM AUTHOR]

Many soil regulating ecosystem services (ES) are linked to Earth's atmosphere, but associated monetary values often are unknown or difficult to quantify. Atmospheric deposition of calcium (Ca2+) and magnesium (Mg2+) are abiotic flows (wet, dry, and total) from the atmosphere to land surfaces, which potentially can become available to sequester carbon (C) as soil inorganic carbon (SIC). However, these processes typically have not been included in economic valuations of ecosystem services. The primary objective of this study was to demonstrate an approach for valuing non-constrained potential SIC sequestration from atmospheric Ca2+ and Mg2+ deposition based on the concept of the avoided social cost of carbon dioxide emissions (SC-CO2). Maximum monetary values associated with the non-constrained potential SIC sequestration were compiled for the contiguous United States (U.S.) by soil order, land resource region (LRR), state, and region using available deposition data from the National Atmospheric Deposition Program (NRSP-3). For the entire contiguous U.S., an average annual monetary value for the non-constrained potential SIC sequestration due to atmospheric Ca2+ and Mg2+ deposition was $135M (i.e., $135 million U.S. dollars, where M = million = 106). Mollisols, Alfisols, and Entisols were soil orders with the highest average annual monetary values for non-constrained potential SIC sequestration. When normalized by land area, however, Vertisols had the highest average annual monetary values followed by Alfisols and Mollisols for non-constrained potential SIC sequestration. From a more agricultural perspective, the LRRs with the highest average annual monetary values for non-constrained potential SIC sequestration were the Western Range and Irrigated Region (D), the Central Feed Grains and Livestock Region (M), and the Central Great Plains Winter Wheat and Range Region (H). When normalized by area, the LRRS with the highest average annual monetary values were the Southwest Plateaus and Plains Range and Cotton Region (I) and the Florida Subtropical Fruit, Truck Crop and Range Region (U). Among the U.S. states, the highest average annual monetary values for non-constrained potential SIC sequestration were Texas, Kansas, and New Mexico, but when normalized by area the highest values by state were Kansas, Iowa, and Texas. Geographical regions in the contiguous U.S. with the highest average annual monetary values for non-constrained potential SIC sequestration were the South Central, Midwest, and West; when normalized by area, the highest values by region were South Central, Midwest, and Northern Plains. Constraints on maximum monetary values, based on physical, chemical, biological, economic, social, and political limitations, need to be considered and quantified to obtain more precise and accurate accounting of the ES associated with SIC sequestration due to atmospheric Ca2+ and Mg2+ deposition. [ABSTRACT FROM AUTHOR]

• Traditional site index (tree height at base age) may not be suitable for urban trees. • Rapid and non-destructive tree age evaluation methods need to be developed. • Loblolly pine tree age was determined using a minimally-invasive recording resistance drill based technique. • The method allowed rapid evaluation of tree age across an urban forest. Conventional site index (tree height at base age) may not be suitable for urban trees, therefore it is important to assess its applicability in urban environments. In addition, rapid and non-destructive tree age evaluation methods need to be developed. The objectives of this study were to: (1) develop a rapid and non-destructive method to determine tree age in urban environments, (2) examine the relationship between tree height, age, location, and soil type, and (3) compare the measured site indices with traditional site indices reported in Soil Survey Geographic Database (SSURGO). The study was conducted at the Clemson Experimental Forest (CEF) using conventionally-managed loblolly pine (Pinus taeda) stands, and loblolly pines in the urban environment of the Clemson University campus (CUC). Tree age obtained with a recording resistance drilling method and stump tree ring counting were comparable (R2 = 0.98, n = 14). Tree age estimates from recording resistance drilling and from increment boring were also similar (R2 = 0.93, n = 25). Replicate drilling samples had a low standard deviation, which indicated the high precision of the methodology. An additional benefit of the recording resistance drilling method is the ability to enable rapid evaluation of tree age across an urban forest. There was no discernible relationship between tree height and recording resistance drill age estimate for loblolly pines on the CUC (n = 25). In contrast, there was a relationship between measured diameter at breast height (DBH, cm) and recording resistance drill age estimates. A portion of the loblolly pine trees in the urban environment on the CUC appeared to have reduced productivity, as measured by the height/age relationship when predominantly surrounded by pavement or grass areas. [ABSTRACT FROM AUTHOR]

Carbon sequestered as soil inorganic carbon (SIC) provides a regulating ecosystem service, which can be assigned a monetary value based on the avoided social cost of carbon (SC-CO2). By definition, the SC-CO2 is a measure, in dollars, of the long-term damage resulting from the emission of a metric ton of carbon dioxide (CO2). Therefore, this dollar figure also represents the value of damages avoided due to an equivalent reduction or sequestration of CO2. The objective of this study was to assess the value of SIC stocks in the contiguous United States (U.S.) by soil order, soil depth (0–20, 20–100, 100–200 cm), land resource region (LRR), state, and region using information from the State Soil Geographic (STATSGO) database together with a reported SC-CO2 of $42 (U.S. dollars). With this approach, the calculated monetary value for total SIC storage in the contiguous U.S. was between $3.48T (i.e., $3.48 trillion U.S. dollars, where T = trillion = 1012) and $14.4T, with a midpoint value of $8.34T. Soil orders with the highest (midpoint) values for SIC storage were: 1) Mollisols ($3.57T), 2) Aridisols ($1.99T), and 3) Alfisols ($841B) (i.e., $841B is 841 billion U.S. dollars, where B = billion = 109). When normalized by land area, the soil orders with the highest (midpoint) values for SIC storage were: 1) Vertisols ($3.57 m−2), 2) Aridisols ($2.45 m−2), and 3) Mollisols ($1.77 m−2). Most of the SIC value was associated with the 100–200 cm depth interval, with a midpoint value of $4T and an area-normalized value of $0.54 m−2. The LRRs with the highest (midpoint) values of SIC storage were: 1) D—Western Range and Irrigated Region ($1.77T), 2) H—Central Great Plains Winter Wheat and Range Region ($1.49T), and 3) M—Central Feed Grains and Livestock Region ($1.02T). When normalized by land area, the LRRs were ranked: 1) I—Southwest Plateaus and Plains Range and Cotton Region ($5.36 m−2), 2) J—Southwestern Prairies Cotton and Forage Region ($4.56 m−2), and 3) H—Central Great Plains Winter Wheat and Range Region ($2.56 m−2). States with the highest (midpoint) values for SIC storage were: 1) Texas ($2.96T), 2) New Mexico ($572B), and 3) Montana ($524B). When normalized by land area, the states were ranked: 1) Texas ($4.47 m−2), 2) Utah ($2.77 m−2), and 3) Minnesota ($2.17 m−2). Lastly, regions with the highest (midpoint) values for SIC storage were: 1) South Central ($3.13T), 2) West ($1.98T), and 3) Northern Plains ($1.62T). When normalized by land area, the regions were ranked: 1) South Central ($2.90 m−2), 2) Midwest ($1.32 m−2), and 3) West ($1.02 m−2). Results from this study demonstrate a new approach for assigning monetary values to SIC stocks at various scales based on their role in providing ecosystem services for climate regulation and carbon sequestration. [ABSTRACT FROM AUTHOR]

Soil makes important contributions to the United Nations (UN) Land Degradation Neutrality (LDN) concept and targets; however, currently, soil is not integrated into measurable information (e.g., indicators, metrics) to monitor land degradation (LD) patterns and trends. This study examines the role of soil in LDN in the UN Convention to Combat Desertification (UNCCD), and UN Sustainable Development Goal (SDG 15: Life on Land). This study is specifically focused on the LDN and biodiversity loss as they relate to an indicator 15.3.1 Proportion of land that is degraded over total land area. Tracking of LD status can be improved by using detailed soils databases combined with satellite-derived land cover maps. This study has applied these newly improved methods to quantify and map the anthropogenic LD status and trends in the contiguous United States of America (USA), as well as to identify potential land areas for nature-based solutions (NBS) to compensate for LD. Anthropogenic LD in 2016 in the contiguous USA affected over two million square kilometers, about one-third of the country's total area, with high variability by state. Between 2001 and 2016, LD in the USA showed an overall increase of 1.5%, with some states exhibiting increases in degraded land while other states had overall improvements to their land. All ten soil orders present in the contiguous USA have been anthropogenically degraded, with Mollisols, Alfisols, and Vertisols having the highest LD levels. Compensating for LD requires a variety of strategies and measures (e.g., NBS), which often require additional land. In 2016, the potential land area for NBS was over two million square kilometers, an area approximately equal to that of degraded land. Some of the states that have high proportions of land available for potential NBS are dominated by soils (Aridisols) typical of deserts and therefore may have less promise for NBS. The variability of LD needs to be evaluated at finer spatial scales for realistic LDN analysis. [ABSTRACT FROM AUTHOR]

Presents correspondence exchanged as a result of a report by Mark A. Schlautman and James J. Morgan on hydrophobic pollutant transport in aquatic systems. Recognition of research done on the hydrocarbon solubilization process; Authors' acknowledgement of earlier researches done in the light of their research on humic substances.

Many climate change "solution" plans include net-zero goals, which involve balancing the anthropogenic greenhouse gas emissions (GHG) with their removal. Achieving net-zero goals is particularly problematic for soils because they are often excluded from GHG inventories and reduction plans. For example, Maryland's Climate Solutions Now Act (Senate Bill 528) put forward the goal of lowering emissions of GHG to 60% under 2006 quantities by 2031 and with a target of net-zero emissions by 2045. To achieve these goals, the state of Maryland (MD) needs to quantify GHG emissions from various sources contributing to the state's total emissions footprint (EF). Soils are currently excluded from MD's GHG assessments, which raises a question about how the soil impacts the net-zero goal. This study examines the challenges in meeting net-zero goals using an example of carbon dioxide (CO2) as one of the GHG types (net-zero CO2 emissions). The current study quantified the "realized" social costs of CO2 (SC-CO2) emissions for MD from new land developments in the period from 2001 to 2016 which caused a complete loss of 2.2 × 109 kg of total soil carbon (TSC) resulting in $383.8M (where M = million, USD = US dollars). All MD's counties experienced land developments with various emissions and SC-CO2 monetary values. Most of the developments, TSC losses, and SC-CO2 occurred near the existing urban areas of Annapolis and Baltimore City. These emissions need to be accounted for in MD's GHG emissions reduction plans to achieve a net-zero target. Soils of MD are limited in recarbonization capacity because 64% of the state area is occupied by highly leached Ultisols. Soil recarbonization potential is further reduced by urbanization with Prince George's, Montgomery, and Frederick counties experiencing the highest increases in developed areas. In addition, projected sea-level rises will impact 17 of MD's 23 counties. These losses will generate additional social costs because of migration, costs of relocation, and damages to infrastructure. The state of MD has a high proportion of private land ownership (92.4%) and low proportion of public lands, which will limit opportunities for relocation within the state. Net-zero targets are important but meeting these targets without specific and integrative approaches depending on the source and type of emissions may result in failure. These approaches should also focus on the social costs of emissions, which raises the need for a new concept of integrating net-zero emissions and social costs. [ABSTRACT FROM AUTHOR]

Conflicts of interest (COI) are an integral part of human society, including their influence on greenhouse gas (GHG) emissions and climate change. Individuals or entities often have multiple interests ranging from financial benefits to reducing climate change-related risks, where choosing one interest may negatively impact other interests and societal welfare. These types of COI require specific management strategies. This study examines COI from land-use decisions as an intersection of different perspectives on land use (e.g., land conservation versus land development), which can have various consequences regarding GHG emissions. This study uses the state of New Jersey (NJ) in the United States of America (USA) as a case study to demonstrate COI related to soil-based GHG emissions from land conversions between 2001 and 2016 which caused $722.2M (where M = million = 106) worth of "realized" social costs of carbon dioxide (SC-CO2) emissions. These emissions are currently not accounted for in NJ's total carbon footprint (CF), which can negatively impact the state's ability to reach its carbon reduction goals. The state of NJ Statutes Annotated 26:2C-37 (2007): Global Warming Response Act (GWRA) (updated in 2019) set a statewide goal of reducing GHG emissions to 80 percent below 2006 levels by 2050. Remote sensing and soil data analysis allow temporal and quantitative assessment of the contribution of land cover conversions to NJ's CF by soil carbon type, soil type, land cover type, and administrative units (state, counties), which helps document past, and estimate future related GHG emissions using a land cover change scenario to calculate the amount of GHG emissions if an area of land was to be developed. Decisions related to future land conversions involve potential COI within and outside state administrative structures, which could be managed by a conflict-of-interest policy. The site and time-specific disclosures of GHG emissions from land conversions can help governments manage these COI to mitigate climate change impacts and costs by assigning financial responsibility for specific CF contributions. Projected sea-level rise will impact 16 out of 21 NJ's counties and it will likely reach coastal areas with densely populated urban areas throughout NJ. Low proportion of available public land limits opportunities for relocation. Increased climate-change-related damages in NJ and elsewhere will increase the number of climate litigation cases to alleviate costs associated with climate change. This litigation will further highlight the importance and intensity of different COI. [ABSTRACT FROM AUTHOR]

Greenhouse gas (GHG) emissions from landcover conversions contribute to the total carbon (C) footprint (CF), which is the sum of GHG emissions from various sources and events expressed as carbon dioxide (CO2) equivalent. Soil-based emissions from land conversions are often excluded from the total CF, which can lead to underreporting the CF. This study uses the state of Connecticut (CT) as a case study to demonstrate the importance of soil-based emissions from land cover conversions to the state's CF. The state of CT Public Act 08-98 (2008): Global Warming Solutions Act (GWSA) set a statutory requirement to cut GHG emissions 10 percent below 1990 levels by 2020 and 80 percent below 2001 levels by 2050 without considering soil-based emissions from land conversions. This omission results in underestimates of past and current emissions related to CT's CF. In addition, not accounting for soil-based emissions from land conversions may increase the future size of CT's CF. Remote sensing and soil data analysis provide an opportunity for rapid, quantitative, and temporal assessment of the contribution of land cover conversions to CT's CF by soil type, land cover type, and administrative units (counties). Results are reported for soil organic carbon (SOC), soil inorganic carbon (SIC), and total soil carbon (TSC) based on C contents and monetary values of social costs of carbon. The state of CT experienced soil-based emissions from land cover conversions from 2001 to 2016 with $388.1M (where $ = USD, M = million = 106) worth of "realized" social costs of carbon dioxide (SC-CO2) emissions which should be accounted for in CT's total CF. The current methodology could be used to optimize future land conversions to minimize the amount of soil GHG emissions by considering the soil C resources in different development scenarios. With an extensive, densely populated coastal area, CT will be directly affected by rising sea levels and other climate change impacts. Future research can focus on owner-specific CF contributions to address the responsibility for costs of GHG emissions as well as limiting the CF impact of land conversions. [ABSTRACT FROM AUTHOR]

Abstract: Changes in the characteristics of a leaf litter-derived humic substance (LLHS) that resulted from its adsorption onto kaolinite or exposure to simulated solar irradiation were tracked using selected spectroscopic descriptors, apparent weight-average molecular weight (MWw) and pyrene binding. Heterogeneity within the original bulk LLHS was confirmed by a range of different characteristics obtained from ultrafiltration-based size fractions. In general, trends of some changing LLHS characteristics were similar for the adsorption and irradiation processes when tracked against percent carbon removal. For example, the overall values of specific ultraviolet absorbance (SUVA), MWw, and humification index (HIX) all decreased with increasing irradiation time and with increasing concentration of mineral adsorbent in the respective experiments, indicating that both processes resulted in less aromatic and smaller-sized LLHS components remaining in solution. In addition, both the adsorption and irradiation experiments resulted in enrichment of the relative distribution of protein-like fluorescence (PLF), implying the PLF-related components had low affinities for phototransformation and mineral surface adsorption. Despite these apparently similar overall trends in LLHS characteristics caused by the adsorption and irradiation processes, closer examination revealed considerable differences in how the two processes altered the original material. Net production of intermediate-sized constituents was observed only with the irradiation experiments. In addition, residual LLHS resulting from the adsorptive fractionation experiments exhibited consistently higher pyrene binding versus the irradiated LLHS despite having comparable MWw values. Changes in LLHS characteristics due to adsorption by kaolinite were likely caused by physical mechanisms (primarily hydrophobic interactions between LLHS components and the kaolinite surface) whereas the irradiation-induced changes appear to have been governed by the combined effects of several alteration mechanisms, including the transformation of more condensed aromatic structures to less aromatic constituents, conformational changes resulting from selective photooxidation, and the photochemical disruption of intramolecular charge-transfer interactions. [Copyright &y& Elsevier]

The primary mechanism responsible for the dynamic fluorescence quenching of polycyclic aromatic compounds (PACs) by Ag+ ions is enhanced intersystem crossing from the lowest singlet excited state to the lowest triplet excited state. For some PACs, however, exciplex formation with Ag+ in polar organic solvents has also been reported. Quenching of pyrene fluorescence by Ag+ in two polar solvent systems (aqueous and ethanolic solutions) was examined here using steady-state and time-resolved fluorescence techniques. In both solvents, quenching led to the formation of a pyrene–Ag+ exciplex, (1Py⋯Ag+)*, which rapidly equilibrated with excited singlet pyrene molecules (1Py*) and Ag+ ions. The exciplex and pyrene monomer emission spectra strongly overlapped, with the dominant exciplex peaks in water and ethanol red shifted from the 0–0 transition of pyrene by 5.08 and 2.56 kJ/mol, respectively. Rate constants for the formation and dissociation of the exciplex were much larger than the radiative and nonradiative decay rate constants for both the excited state monomer and exciplex. The short exciplex fluorescence lifetimes and very low quantum yields observed in the two solvents can be attributed to enhanced nonradiative decay processes for the exciplex. The emission quantum yield of the exciplex formed in aqueous solution was approximately an order of magnitude larger than that in ethanolic solution, which is likely to be attributable to the higher polarity of water versus ethanol. [Copyright &y& Elsevier]

Application of accurate and low-cost sensor technology to collect soil color data provides an opportunity to increase the density, quality and quantity of soil data to monitor our changing soil resources. The objective of this study was to develop a mobile application that would enable users to create their own soils database consisting of GPS location and soil color data gathered using the application and a mobile sensor. A mobile application was created utilizing the Nix™ Pro color sensor that produces multiple color results, including Munsell color notation. The application also allows users to toggle between “in-field” sampling as well as dry or moist soil samples. Users can choose to record GPS location and a photo of the soil sample to upload into an online database for storage. The application was tested for functionality in the field and for its ability to match Munsell notation values determined using a Munsell Soil Color Chart (MSCC). Field data were synchronized to a cloud database and subsequently retrieved and used to produce a Geographic Information Systems (GIS) layout showing sample point locations and soil color attributes. The Soil Scanner application allows for rapid analysis and collection of soils data that can be stored for further study and reference using various color systems and location data. [ABSTRACT FROM AUTHOR]

Quantifying soil organic carbon (SOC) is important for soil management, precision agriculture, soil mapping and carbon dynamics research. Inexpensive sensor technologies offer the potential for rapid quantification of SOC in laboratory samples as well as in the field. The objective of this study was to use a commercially-available color sensor to develop SOC prediction models for both dry and moist soils from the Piedmont region of South Carolina. Thirty-one soil samples were analyzed for lightness to darkness, redness to greenness, and yellowness to blueness (CIEL*a*b*) color using a Nix Pro™ color sensor. Soil color was measured under both dry and moist soil conditions and the depth of each soil sample was also recorded. Using L*, a*, b* and soil depth for each sample as initial predictors, regression analyses were conducted to develop SOC prediction models for dry and moist soils. The resulting residual plots, root mean squared errors (RMSE), and coefficients of determination (R 2 ) were used to assess model fits for predicting the SOC content of soil. Cross validation was conducted to determine the efficiency of the predictive models and the mean squared prediction error (MSPE) was calculated. The final models included soil depth, L*, and a* as independent variables (dry soils R 2 = 0.7978 and MSPE = 0.0819, moist soils R 2 = 0.7254 and MSPE = 0.1536). The results suggest that soil color sensors have potential for rapid SOC determination, and soil depth and color are useful in predicting SOC content in soils. [ABSTRACT FROM AUTHOR]

Organic and inorganic soil C pools are major components of the global C budget, yet they are still poorly estimated and understood. This study ranked atmospheric wet Ca2+ deposition from 1994 to 2003 within the continental United States by soil order using spatial analysis of Ca2+ wet deposition data and a state soil geographic database. The total average annual atmospheric wet deposition (AAAWD) of Ca2+ within the continental United States was 8.6 x 108 kg, which would be equivalent to the theoretical formation of 2.6 x 108 kg C as soil inorganic C (SIC), barring losses from erosion and deep leaching. The soil orders receiving the highest area-normalized total AAAWD of Ca2+ were: (i) Alfisols (172 kg km-2 Ca2+), (ii) Mollisols (170 kg km-2 Ca2+), (iii) Histosols (168 kg km-2 Ca2+, and (iv) Vertisols (157 kg km-2 Ca2+). Barring losses from erosion and leaching, these Ca2+ wet deposition fluxes would equate to the theoretical formation of the following amounts of area-normalized total C equivalents in the pedon: (i) Alfisols, 52 kg C km-2 (ii) Mollisols, 51 kg C km-2 (iii) Histosols, 50 kg C km-2 and (iv) Vertisols, 47 kg C km-2. The sequestration of SIC has been shown to be important in soil orders of nonarid regions, particularly in Mollisols and Aluisols. [ABSTRACT FROM AUTHOR]

Abstract: A new, simple, and rapid method to determine Setschenow (i.e., salting-out) constants for luminescent organic compounds in aqueous solutions has been developed using steady-state and time-resolved fluorescence measurements. Application of the new method was demonstrated using pyrene in the presence of nonquenching (K+) and dynamically quenching (Cs+) akali metal chloride salt solutions at room temperature. For these two model systems, Setschenow constants for pyrene salting-out by KCl and CsCl were determined to be 0.211 and 0.355M−1, respectively. We expect that the methodology reported in this paper can be applied equally well to interactions between a variety of salting-out agents and fluorescent biological and/or environmental molecules in aqueous solutions. [Copyright &y& Elsevier]

Abstract: Emission from two different peroxyoxalate chemiluminescence (PO-CL) reaction pathways (i.e., 1,1′-oxalyldiimidazole (ODI) and bis(2,4,6-trichlorophenyl)oxalate (TCPO) CL reactions) is significantly reduced in the presence of increasing Cu2+ concentrations. The CL intensity decrease in the ODI-CL reaction results from deactivation of the high-energy intermediate(s) by Cu2+, whereas the apparent quenching in the TCPO-CL reaction results from both this effect and formation of Cu2+–imidazole (ImH) complexes [Cu(ImH) n=1–4]2+. Because the reaction between Cu2+ and ImH occurs competitively with the formation of a high-energy intermediate (X) in TCPO-CL reactions, accurately determining Cu2+ concentrations with a TCPO-CL-based system is more difficult versus an ODI-CL-based system. Using ODI-CL, the detection limit of Cu2+ dissolved in water was determined to be 5.0×10−8 M (signal:noise=3) in a 1cm fluorescence flow micro-cell. ODI-CL-based systems are expected to be useful for the rapid quantification of many quenchers in environmental and biological samples because the interactions between the high-energy intermediate(s) and quencher are very rapid relative to other competitive reactions. [Copyright &y& Elsevier]

Development of low-cost strategies enabling phosphorus (P) use, recovery, and reuse across multiple economic sectors is needed to ensure its long-term availability for those industries that require P to enhance plant productivity. Irrigation return water from conventional agriculture and specialty crop production remains a source of excess P loading to aquatic ecosystems. Low-cost and technology treatment options are critical for the long-term economic and environmental sustainability of agricultural producers. To address P removal with a sustainable lens, we identified iron oxides (FeOx, a waste product from treating coal mine drainage) as a potential substrate for P sorption, and further evaluated the potential for reuse of P-saturated FeOx as a fertilizer source. The overall objectives of this study were to quantify P sorption, desorption, and plant availability of P adsorbed to FeOx. Batch sorption experiments were conducted to measure the effect of mixing FeOx with silica sand (1:1; FeOx:sand, by mass) on P sorption capacity. The sorption capacity of the FeOx:sand mixture was 21.5 mg P/g FeOx using deionized water. Less than 1% of initially adsorbed P desorbed over 96 h in treatments using irrigation reservoir water adjusted to either pH 6.0 or pH 10.0, demonstrating the stability of the sorption complexes against pH changes expected in irrigation return water systems. Plant available P, which we define as P that desorbed after contact with a CaCl 2 solution, ranged from 0.10–0.12 mg/L P; this range is within nutrient recommendations for most plants. Phosphorus-saturated FeOx may be suitable as a fertilizer amendment, as well as a sustainable option for P removal from water. This research provides the foundation for a circular P economy, with viable P treatment and reuse paired with managing a waste product from another widespread industry. Unlabelled Image [ABSTRACT FROM AUTHOR]

Oxidation of manganous manganese (Mn II ) is an important process driving manganese cycles in natural aquatic systems and leading to the formation of solid-phase Mn III,IV (hydr)oxide products. Previous research has shown that some simple ligands (e.g., phosphate, sulfate, chloride, fluoride) can bind with Mn II to make it unreactive to oxidation by dissolved oxygen. However, there is little to no understanding of the role played by stronger, complex-forming ligands in Mn II oxidation reactions. The objective of this study was to evaluate the rates of abiotic Mn II oxidation by O 2 in the presence of low concentrations of several complex-forming model ligands (pyrophosphate, tripolyphosphate, ethylenediaminetetraacetic acid, oxalate) in bicarbonate-carbonate buffered laboratory solutions of pH 9.42, 9.65, and 10.19. The influence of increasing ligand concentrations on observed autocatalytic profiles of Mn II oxidation was investigated, and initial oxidation rates were linked quantitatively to the initial Mn II speciation in experimental solutions. Observed rates of Mn II oxidation decreased with increasing ligand concentration for all four ligands tested. However, the profiles observed with time and the magnitudes of decrease in initial oxidation rates were different for the different ligands. Likely explanations for these observations include the denticity of the tested ligands, the relative strength of the ligands to complex Mn II versus Mn III , and the ability of some ligands to enhance the reduction of Mn III back to Mn II on a time scale comparable to the forward homogeneous Mn II oxidation reaction.

Natural organic matter (NOM) sorption to nanoparticles (NPs) can influence their transport and bioavailability in the aquatic environment. The sorption affinity of NOM to surfaces including NPs is size dependent, and depending on environmental conditions, NOM may enhance or mitigate NPs toxicity. The aim of this study was to investigate the preferential sorption of different-sized fractions of NOM to titanium dioxide (TiO2) NPs. We specifically investigated the influence of pH, ionic strength, and NOM concentration on the extent of this preferential sorption using a constant sorbent concentration (400 mg/L TiO2 NPs). Additionally, sorption of NOM to TiO2 NPs at varying pH was investigated. The nonsorbed NOM was separated from the sorbed, by 50 nm polycarbonate membrane filters and ultracentrifugation. High-performance size exclusion chromatography (HPSEC) was used to determine the average molecular weights of NOM (MWw). Corroborative evidence of preferential sorption of different-sized molecular weight fractions of NOM was obtained from optical techniques such as absorbance and fluorescence spectrophotometry. The total organic carbon was measured by the Total Organic Carbon Analyzer-Shimadzu (TOC-VCPH). The results indicated that there is preferential sorption of larger sized fractions of NOM to TiO2 NPs irrespective of NOM concentration. It was observed that the sorption of larger sized fractions of NOM was much enhanced at lower pH and at higher ionic strength. Both absorbance and fluorescence spectrophotometric techniques gave credible corroborative evidence on the extent of preferential sorption of lager sized fractions of NOM with respect to pH and ionic strength. The sorption results demonstrated higher sorption at lower pH than at higher pH. Overall, the results of this study suggest that the environmental conditions are key factors that can contribute to NOM's fractional preferential sorption to NPs in the aquatic environment.

A novel liquid chromatographic (LC) method with repeated injections of Suwannee River Fulvic Acid (SRFA) was used to investigate its adsorptive fractionation by synthetic α-Al(2)O(3). Eluent (i.e., non-retained) SRFA for each injection was monitored by two ultraviolet (UV) absorbance detection channels (300 and 365 nm) and one fluorescence detection channel (λ(ex)=350 nm, λ(em)=450 nm). Preferential adsorption of SRFA constituents was revealed by the different responses of the three LC detection channels. Samples of non-retained SRFA from injections of three independent replicate experiments were collected and aggregated for subsequent analysis by steady state ultraviolet-visible (UV/vis) absorption spectrometry and size exclusion chromatography (SEC). The ratio of absorbance at 254 and 204 nm, a surrogate for specific UV absorbance at 254 nm, increased with increasing injection number for the non-retained SRFA, indicating the preferential adsorption of SRFA constituents containing aromatic moieties. SEC analysis confirmed the preferential adsorption of higher molecular weight (MW) SRFA constituents as the non-adsorbed SRFA fractions increased in MW across the series of injections. The SEC results also suggested that certain SRFA constituents in the ca. 2-5 kDa MW range adsorbed in early injections were displaced by higher MW species (ca. 5-10 kDa) in later injections., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Divalent cations have been reported to develop bridges between anionic polyelectrolytes and negatively-charged colloidal particles, thereby enhancing particle flocculation. However, results from this study of kaolinite suspensions dosed with various anionic polyacrylamides (PAMs) reveal that Ca(2+) and Mg(2+) can lead to colloid stabilization under some conditions. To explain the opposite but coexisting processes of flocculation and stabilization with divalent cations, a conceptual flocculation model with (1) particle-binding divalent cationic bridges between PAM molecules and kaolinite particles and (2) polymer-binding divalent cationic bridges between PAM molecules is proposed. The particle-binding bridges enhanced flocculation and aggregated kaolinite particles in large, easily-settleable flocs whereas the polymer-binding bridges increased steric stabilization by developing polymer layers covering the kaolinite surface. Both the particle-binding and polymer-binding divalent cationic bridges coexist in anionic PAM- and kaolinite-containing suspensions and thus induce the counteracting processes of particle flocculation and stabilization. Therefore, anionic polyelectrolytes in divalent cation-enriched aqueous solutions can sometimes lead to the stabilization of colloidal particles due to the polymer-binding divalent cationic bridges., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The capabilities of three simplified analytical equations to accurately model electrostatic interactions during proton binding and release by linear anionic polyelectrolytes in aqueous solution were evaluated. The impermeable sphere (IS), Donnan (DN), and cylindrical (CY) electrostatic models were fit to experimental acid-base titration curves of linear polyacrylamide-co-acrylate having ionizable site densities ranging from ca. 10-35%. The titrations were conducted in 0.003-0.12M NaCl solutions and the sum of squared errors from modeled and experimental data was used as a comparative index of each model's capability. In addition, the relative size of each polyelectrolyte was estimated from its measured specific viscosity and then compared against the values obtained from the fitting procedure for the size parameter that each model contained. Although the IS and DN electrostatic models could be used to obtain reasonably good fits to each titration curve, the size parameter values obtained by each model were not reflective of the actual polyelectrolyte sizes, indicating that the models had limited physical meaning and that the size parameter was essentially just an additional fitting parameter in each model. In contrast, the CY model was not only more effective in its ability to fit the titration data but also provided a better physical representation of the polyelectrolyte size. Therefore, for polyelectrolytes that remain essentially linear or are only loosely coiled such that counter ions are free to travel throughout the polymer structure, we conclude that the CY model and its morphological representation of a cylindrical polyelectrolyte are more valid and realistic than the IS and DN models and their representation of polyelectrolytes as spheres., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The Reedy River in South Carolina is affected by the urban area of Greenville, the third most populous city in the state, and by the effluents from two large-scale municipal wastewater treatment plants (WWTPs) located on the river. Riverine water chemistry was characterized using grab samples collected annually under spring season baseflow conditions. During the 4-year time period associated with this study, climatic variations included two severe drought spring seasons (2001 and 2002), one above-normal precipitation spring season (2003), and one below-normal precipitation spring season (2004). The influence of drought and human activities on the baseflow chemistry of the river was evaluated by comparing concentrations of dissolved anions, total metals, and other important water chemistry parameters for these different years. Concentrations of copper and zinc, common non-point source contaminants related to urban activities, were not substantially elevated in the river within the urban area under baseflow conditions when compared with headwater and tributary samples. In contrast, nitrate concentrations increased from 1.2-1.6 mg/l up to 2.6-2.9 mg/l through the urban stream reach. Concentrations of other major anions (e.g., sulfate, nitrate) also increased along the reach, suggesting that the river receives continuous inputs of these species from within the urban area. The highest concentrations of major cations and anions typically were observed immediately downstream from the two WWTP effluent discharge locations. Attenuation of nitrate downstream from the WWTPs did not always track chloride changes, suggesting that nitrate concentrations were being controlled by biochemical processes in addition to physical processes. The relative trends in decreasing nitrate concentrations with downstream distance appeared to depend on drought versus non-drought conditions, with biological processes presumably serving as a more important control during non-drought spring seasons.

Recent molecular modeling and spectroscopic studies have suggested that relatively strong interactions can occur between aromatic pi donors and metal cations in aqueous solutions. The objective of this study was to characterize potential cation-pi interactions between pi donors and exchangeable cations accumulated at mineral surfaces via both spectroscopic and batch sorption methods. Quadrupolar splitting in deuterium nuclear magnetic resonance ((2)H NMR) spectroscopy for d(2)-dichloromethane, d(6)-benzene, and d(8)-toluene (C(6)D(5)- moiety) in aqueous suspensions of a Na-saturated reference montmorillonite unambiguously indicated the ordering of solute molecules with respect to the clay surface. The half line broadening (Delta nu(1/2)) of (2)H NMR of d(6)-benzene in montmorillonite suspensions showed that soft exchangeable cations generally resulted in more benzene sorption compared with harder cations (e.g., Ag(+) > Cs(+) > Na(+) > Mg(2+), Ba(2+)). In batch sorption experiments, saturating minerals (e.g., porous silica gels, kaolinite, vermiculite, montmorillonite) with a soft transition metal or softer base cations generally increased the polycyclic aromatic hydrocarbon (PAH) sorption relative to harder cations (e.g., Ag(+) >> Cs(+) > K(+) > Na(+); Ba(2+) > Mg(2+)). Sorption of phenanthrene to Ag(+)-saturated montmorillonite was much stronger compared with 1,2,4,5-tetrachlorobenzene, a coplanar non-pi donor having slightly higher hydrophobicity. In addition, a strong positive correlation was found between the cation-dependent sorption and surface charge density of the minerals (e.g., vermiculite, montmorillonite >> silica gels, kaolinite). These results, coupled with the observations in (2)H NMR experiments with montmorillonite, strongly suggest that cation-pi bonding forms between PAHs and exchangeable cations at mineral surfaces and affects PAH sorption to hydrated mineral surfaces.

Chemical interactions of aromatic organic contaminants control their fate, transport, and toxicity in the environment. Recent molecular modeling studies have suggested that strong interactions can occur between the pi electrons of aromatic molecules and metal cations in aqueous solutions and/or on mineral surfaces, and that such interactions may be important in some environmental systems. However, spectroscopic evidence for these so-called cation-pi interactions has been extremely limited to date. In this paper, cation-pi interactions in aqueous salt solutions were characterized via 2H nuclear magnetic resonance (NMR) spin-lattice relaxation times (T1) and calculations of molecular correlation times (tau(c)) for a series of perdeuterated (d6-benzene) benzene-cation complexes. The T1 values for d6-benzene decreased with increasing concentrations of LiCl, NaCl, KCl, RbCl, CsCl, and AgNO3, with the largest effects observed in the AgNO3 and CsCl solutions. Upon normalizing tau(c) values by solution viscosity effects, an overall affinity trend of Ag+ >> Cs+ > K+ > Rb+ > Na+ > Li+ was derived for the d6-benzene-cation complexes. The ability of Ag+ to complex d6-benzene was significantly reduced upon addition of NH3, which strongly coordinates Ag+ at high pH. Results with d6-benzene, d8-naphthalene, d2-dichloromethane, and d12-cyclohexane in 0.1 M methanolic salt solutions confirmed that spin-lattice relaxation rates are characterizing cation-pi interactions. The relatively strong cation-pi bonding observed between Ag+ and aromatic hydrocarbons probably results from covalent interactions between the aromatic pi electrons and the d orbitals of Ag+, in addition to the normal electrostatic interaction.