Calcareous wetlands are rare in New England due to the limited occurrence of limestone-rich bedrock. Because of their great floristic diversity and their support of numerous rare and uncommon plant species, these habitats are targeted for conservation. Little is known about the intricate workings of these ecosystems. This research contributes significantly to understanding the complex biogeochemical relationships that exist between the plant and soil systems in calcareous freshwater wetland environments as a whole. A 3-year field study was initiated in May 1996, to collect data on soils, geochemistry, and hydrology along a 250-m-long transect. Monitoring was concentrated within the rooting zone. Field monitoring and water sampling were conducted biweekly across three growing seasons. Measurements were made for soil-water pH, conductivity, total iron, alkalinity and several dissolved metals. Strong seasonal patterns were observed for several parameters including calcium and iron. Seasonal changes in geochemistry were evaluated using Solmineq.88, a thermodynamic model. In July 1997, soils were sampled adjacent to each replicate instrumentation cluster and standard analyses conducted. Significant differences were measured between the stations for pH, cation exchange capacity, exchangeable calcium, phosphorus, manganese, and biologically available iron. A detailed vegetation analysis was completed in July 1997. High species richness and turnover were measured across the site. Ordination and cluster techniques were used to analyze the vegetation patterns and relate these to environmental site variables. The ordinations suggest that gradients in both soil chemistry (e.g., pH, exchangeable calcium, phosphorus, and iron) and geochemistry (e.g., pH and dissolved calcium) may have strong influences on the vegetation patterns observed in this study. These research results will serve as a baseline for the geochemistry in the greater watershed region, representing a relatively undisturbed system. No fen studies currently exist (for any geographical region) that monitored soil and geochemical parameters throughout the growing season. This research demonstrates the importance of seasonal sampling to describe the cycles present in site biogeochemistry accurately, and it defines several geochemical parameters that strongly influence plant species occurrence and distribution within these environments. This detailed analysis provides valuable information for conservation managers seeking to identify areas for future conservation, preservation, or restoration efforts.

Time of planting plays a critical role in nitrogen (N) uptake by rye cover crop (CC). Even a few days of delay in planting can severely decrease CC performance. Evaluating the amount of N accumulation related to time of planting is critical to the farmer who has to optimize the winter rye planting date based on completion of corn harvest, suitable weather conditions and time availability for fall manure application. Winter rye cover crop was planted at 6 planting dates in fall from mid August to early October at weekly intervals from 2004 to 2009. The results suggest that delay from critical planting date (CPD) will decrease rye N uptake dramatically. Suggested CPDs for northwest parts of Massachusetts are not applicable because they are too early (third to fourth week of August). CPDs for central parts of the State are from first to second week of September. Farmers in these zones can take advantage of cover crop by a better time management and planting no later than CPD. In Eastern areas of Massachusetts CPD is the third week of September. By evaluating the effect of planting date on rye growth and N accumulation throughout the State, this model provides a powerful decision making tool for increasing N recovery and reducing nutrient leaching. Sixteen units of cost effective and accurate automated lysimeters were designed and installed to measure post-harvest nitrate leaching from a rye cover crop field during the falls and winters of 2007 to 2009. The electronic system was designed to monitor soil tension and apply the equal amount of suction to the sampling media. Hourly data from soil tension and vacuum applied to the system were collected and stored by each unit. A safety system was designed for protecting vacuum pump against unexpected major vacuum leakage events. The controller can be easily reprogrammed for different performance strategies. Other major parts of lysimeter included the power supply systems, vacuum pump, vacuum tanks, sampling jars, suction cups and plates, and electronic valves. The electronic system showed a very reliable and accurate performance in the field condition.

Isoxaflutole is a new pre-emergence herbicide which undergoes rapid conversion to a diketonitrile metabolite (DKN) in soil. In soil the half-life of isoxaflutole is very short, but the half-life of DKN is much longer. Sorption studies were conducted with five soils varying in physical and chemical properties using the batch equilibration technique. Analysis of 14C-ring labeled isoxaflutole and DKN was performed using liquid scintillation counting, and sorption data were fitted to the Freundlich model. Isotherms of isoxaflutole and DKN in all the soils were nonlinear as depicted by the exponent ( n < 1.0), indicating differential distribution of sorption site energies in various soils. Isoxaflutole and DKN sorption increased with an increase in organic matter content of soils and decreased as the soil pH increased from 4.5 to 8.5, which was depicted by the reduction of KF values. Clay content of the soils did not have a high correlation with KF values, while the sorption of isoxaflutole was not influenced by the Ca2+ concentration in the soil solution. There was an increase in the sorption of DKN with an increase in Ca 2+ concentration of the soil solution, while the net sorption constant (Kd) was correlated to the organic matter content of the soils. A high correlation existed between the desorption coefficient, KFd and the organic matter content of soils, while the clay content did not greatly influence the desorption of DKN. Although the sorption of DKN was generally reversible, a sorption-desorption hysteresis was apparent in all soils. The site energy distribution curves emphasized the fact that DKN binds tightly to soils with higher organic matter content, and a larger proportion of DKN was retained by those soils. In soils with high organic matter content, the sorption-desorption hysteresis was mainly governed by organic matter content, but in soils with low organic matter, clay content played an important role. When isoxaflutole and DKN were added to soil, the carbonyl stretching frequency decreased as observed in the diffuse reflectance Fourier transformed infrared (DRIFT) spectra. In conclusion, the potential for leaching through soil and crop injury due to isoxaflutole and its metabolite would decrease as soil organic matter and clay content increase.

Humic substances (HS) are major components of soil organic matter (SOM). Advances on characterization of HS and their interaction with minerals can provide a more fundamental understanding of HS functions in soils. The objectives of this research were to investigate potential fractionation of humic acid (HA) upon adsorption on minerals and to determine any variation on structure and sorption properties of humin extracted by different methods. Nuclear magnetic resonance (NMR) spectra, for the first time, provided direct evidence that HA was fractionated during adsorption on mineral surfaces. Aliphatic fractions of HA were preferentially adsorbed while aromatic fractions were more likely to be left in solution. The bound HA fractions had higher sorption linearity (N) and affinity (KOC) for phenanthrene than the source HA. For montmorillonite and kaolinite, the KOC values of adsorbed HA were up to several times higher than that of the source HA as a result of fractionation. Extraction procedures had substantial influences in structure and sorption characteristics of humin. Humin from 0.1 M NaOH exhaustive extraction and 6 M HF/HCl extraction at 60°C had relatively more aliphatic components as compared with 1 M HF extracted humin. The treatment of 6 M HF/HCl at 60°C reduced more than 50% carbohydrate components (50-108 ppm) and enriched amorphous poly(methylene) domains. The NaOH exhaustively extracted humin had the most nonlinear sorption isotherms and the HF extracted humin had the lowest KOC. We concluded that both NaOH and NaOH-HF procedures were appropriate approaches for humin extraction but the extraction with 6 M HF/HCl at 60 °C would be discouraged for use due to structural modifications of humin both chemically and physically. Segmental mobility of HA in solution was also explored by NMR relaxation. Proton spin-lattice relaxation time (T1) of HAs ranged from 0.3 to 0.8 s in d6-DMSO, and from 0.26 to 2.3 s in 0.5 M NaOD at 300 MHz. Proton correlation time of HA in solvents was in an order of 10-10 s. Carbohydrate was identified as the largest and the most immobile components while aliphatic and aromatic fragments were relatively smaller and more mobile in aqueous solution.

Humic substances (HS) are the major components of soil organic matter (SOM), which are by far the most abundant organic materials in the environment. Advances on structural characterization of HS and their interaction with clay minerals will provide a more fundamental understanding of HS functions in such important roles as sorption of anthropogenic organic contaminants, stabilization of soil aggregates, and C sequestration. The objectives of this research were to determine any variation in structure and sorption properties of humic acids (HAs) and humins sequentially extracted from a soil and investigate characterization and fractionation of HA and relatively small carboxylic acids upon adsorption on clay minerals. In a phenanthrene sorption study of sequentially extracted HAs and humins, there were significant chemical and structural differences among the HA fractions and humins, and sorption was greatly affected by chemical structure and composition of humic substances, even from the same soil. A positive trend was observed between the sorption coefficient and the aliphaticity. Humin fractions with the highest aliphatic C contents and the lowest polarity showed the highest sorption capacity and nonlinearity as compared with the HAs. A negative relation was shown between the sorption capacity and polarity of HAs. The aliphatic-rich SOM in this study had less polar moieties, but had relatively high Koc. Therefore, the polarity of SOM is likely one of the important parameters controlling sorption of hydrophobic organic chemicals (HOCs). Adsorption of SOM onto clay minerals modifies their surfaces and reactivity and strongly influences the fate of organic contaminants and other species in soils and sediments. For investigation of the structural and conformation changes of HA and clay-HA complexes after sequential adsorption by goethite, kaolinite, and montmorillonite, UV-Visible spectroscopy, high performance size exclusion chromatography (HPSEC), Fourier transform infrared (FT-IR) spectroscopy, and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy were employed. Aliphatic rich HA fractions with polar functional moieties readily adsorb to the goethite surface, while aromatic fractions were left in solution. Similar to HA fractionation onto goethite, paraffinic fractions and polar aliphatic fractions sorbed preferentially on montmorillonite, but aromatic functional moieties likely remained in solution. However, paraffinic fractions were observed on kaolinite surfaces although the adsorbed proportion of these fractions was low. Because of high broken edge areas, kaolinite has more adsorption sites for carboxylic and carbonyl rich fractions than montmorillonite. With respect to MW fractionation after sorption, relatively low molecular weight (MW) HA fractions had a greater affinity for the goethite surface from the analysis and inference of the HPSEC chromatograms, which differs from the reported results in the literature. The low MW HA fractions might be intercalated into the interlayer of montmorillonite and high MW HA fractions adsorbed on external surfaces, which results in the adsorption of relatively wide range of MW HA fractions. The binding mode of small HA fractions on the clay minerals may be ligand exchange and/or electrostatic interaction, which gives HA-clay complexes new hydrophobic sorption sites for high MW HA fractions. To obtain information on the nature of the interactions between SOM and clay mineral surfaces, the adsorption of dicarboxylic acids by kaolinite and montmorillonite at different pH conditions was investigated using in situ attenuated total reflectance Fourier transformed infrared (ATR-FTIR) and ex situ diffuse reflectance infrared Fourier transformed (DRIFT) spectroscopy. The sorption was highly pH dependent and related to the surface characteristics of minerals; adsorption of dicarboxylic acids (succinic acid, glutaric acid, adipic acid, and azelaic acid) was the highest at pH 4 as compared with those at pH 7 and 9, and the sorption capacity of montmorillonite was greater than that of kaolinite. Furthermore, the complexation types, inner- or outer-sphere, depended upon dicarboxylic acid species, pH, mineral surfaces, and solvent conditions. Most samples tend to have outer-sphere adsorption with the mineral surfaces at all tested pHs. However, inner-sphere coordination between the carboxyl groups and mineral surfaces at pH 4 was dominant with freeze-dried complex samples. Therefore, organic acids in an aqueous environment prefer to adsorb onto kaolinite and montmorillonite by outer-sphere complexation, but inner-sphere complexation is favored under dry conditions. These results imply that organic acid binding onto clay minerals under dry conditions is stronger than that under wet conditions. The stable NOM/mineral complexes formed by frequent wetting-drying cycles in nature may resist chemical/microbial degradation of the NOM, which will affect carbon storage in the environment and influence the sorption of organic contaminants.

Master of Science / Department of Chemical Engineering / Larry Erickson / Urban soils contaminated with lead can pose a health risk if vegetables and fruits from the garden are consumed. In general, we don’t think our gardens as dangerous or toxic, but unfortunately some garden soils do contain toxic levels of lead. Chipping paint around older structures will raise the lead level in the soils directly adjacent to the building. Restrictions to lead paint started in the 1950’s. Today lead paint content has been reduced; however paint companies are allowed to mix up to 0.05% lead in paints. Lead use has been reduced significantly, but not entirely eliminated. Soil can be contaminated with lead from other sources such as industrial sites, industrial sludge with heavy metals, auto emissions, old lead plumbing pipes or even old orchard sites in production when lead arsenate was in use. The main concern with lead in firing ranges is the fate and transport of heavy metals from bullets fragments accumulating in soil. Of these metals, lead is the predominant contaminant. Lead is considered the top environmental threat to children’s health. The U.S. military alone has cleaned up more than 700 firing ranges across the country over the past several years. The U.S. Air Force conducted a study at Shaw Air Force base to determine the lead concentrations in ground water and soil collected from the Small Arms Firing Range in 1992. The purpose of this study was to determine the levels of contamination in the soil in order to develop a restoration plan. The goal of the restoration plan was to clean up the land for future use. The Defense Environmental Restoration Program (DERP) conducted a project at Beale Air Force Base to clean up contaminated lead soil and to prevent any future fine and environmental expenses for the base. The main goal was to protect the base population from the lead and other contaminants hazards. In 1992 the Air Force conducted an investigation that included environmental sampling of soil and lead of the Tyndall Elementary School grounds. The Air Force collected lead samples in areas where children play on the school ground. Because lead concentrations results were below the toxic levels for lead, the Air Force concluded that no further action was needed. Further investigation for soil removal took part in 1992 and 2009. Under the Critical Removal Action field activities included site preparation, waste characterization, investigative sample chemical analysis, contaminated soil excavation, dust control, disposal, backfill and grading, and site restoration. Over the years the Air Force has been able to educate the military community on health hazards in the base facilities especially lead exposure and have been able to implement programs dedicated to prevent any lead overexposure.

<p>The majority of the current production, use, and disposal of engineered nanomaterials (ENMs) occur in terrestrial environments, and consequently terrestrial ecosystems are and will increasingly be some of the largest receptors of ENMs at all stages of their life cycles. In particular, soil is predicted to be one of the major receptors of ENMs due to ENM-contaminated biosolid fertilizer and nanopesticide application to agricultural fields, runoff from landfills or ENM-bearing paints, or atmospheric deposition. Both agricultural and natural systems are at risk to ENM contamination via these release scenarios, which makes it necessary to understand the interactions between ENMs, soils, and soil organisms such as plants in order to predict their impacts in real-world scenarios. Gravity-driven vertical transport of TiO2, CeO2, and Cu(OH)2 engineered nanomaterials (ENMs) and their effects on soil pH and nutrient release were measured in three unsaturated soils. ENM transport was found to be highly limited in natural soils collected from farmland and grasslands, with the majority of particles being retained in the upper 0-3 cm of the soil profile, while greater transport depth was seen in a commercial potting soil. Physical straining appeared to be the primary mechanism of retention in natural soils as ENMs immediately formed micron-scale aggregates, which was exacerbated by coating particles with Suwannee River natural organic matter (NOM). Changes in soil pH were observed in natural soils contaminated with ENMs that were largely independent of ENM type and concentration. These changes may have been due to enhanced release of naturally present pH-altering ions (Mg2+, H+) in the soil, likely via substitution processes. This suggests ENMs will likely be highly retained near source zones in soil and may impact local communities sensitive to changes in pH or nutrient availability. Few studies have investigated the influence of environmental conditions on ENM uptake and toxicity, particularly throughout the entire plant life cycle. Here, soil-grown plants (Clarkia unguiculata, Raphanus sativus, and Triticum aestivum) were exposed until maturity to TiO2, CeO2, or Cu(OH)2 ENMs under different illumination intensities, in different soils, and with different nutrient levels. Fluorescence and gas exchange measurements were recorded throughout growth and tissue samples from mature plants were analyzed for metal content. ENM uptake was observed in all plant species, but was seen to vary significantly with ENM type, light intensity, nutrient levels, and soil type. Light intensity in particular was found to be important in controlling uptake, likely as a result of plants increasing or decreasing transpiration in response to light. Significant impacts on plant transpiration, photosynthetic rate, CO2 assimilation efficiency, water use efficiency, and other parameters related to physiological fitness were seen. The impacts were highly dependent on environmental conditions as well as ENM and soil type. Notably, many of these effects were found to be mitigated in soils with limited ENM mobility due to decreased uptake. These results show that abiotic conditions play an important role in mediating the uptake and physiological impacts of ENMs in terrestrial plants.

<p> With future climate change and increased water demand and scarcity in the Colorado River Basin, the Bureau of Reclamation estimates that the costs of salinity damage will increase for Colorado River users and will exacerbate the current salinity challenges. This study focuses on saline and sodic soils associated with the Mancos Shale formation in order to investigate the mechanisms driving sediment and salinity loads in the Price-San Rafael River Basin of the upper Colorado River. A Walnut Gulch rainfall simulator was operated with a variety of slope angles and rainfall intensities at two field sites (Price, Dry-X) near Price, Utah in order to evaluate how the amount and spatial distribution of vegetation affects salinity in runoff. For each simulated rainfall event, the time-varying concentrations of major cations, anions, and sediment in runoff were measured. Principal component analysis revealed that the two field sites are generally different in runoff water chemistry and soil chemistry, likely due to the difference in parent material and soil indicative of their location on different geologic members. The Dry-X site also has substantially greater total dissolved solids (TDS) and sediment in runoff, soil sodium absorption ratio (SAR), and soil cation exchange capacity (CEC) than the Price site. Despite these differences, a consistent positive linear relationship between the plot-averaged sediment and TDS concentration was found across both sites. The Rangeland Hydrology Erosion Model (RHEM) was calibrated to provide unbiased estimates of sediment in runoff from 23 runs of the rainfall simulator. RHEM simulated the plot-plot variability best at Dry-X compared to Price. Sensitivity analysis of the RHEM input parameters showed that the splash and sheet erodibility coefficient (Kss) and the effective saturated conductivity coefficient (Ke) had the largest influence on the model&rsquo;s sediment and discharge outputs, respectively. The regression that predicted TDS concentration from sediment was applied to RHEM outputs to show that the model could be used to provide salinity estimates for different storm intensities on this part of the Mancos Shale. The potential influence of vegetation canopy cover on sediment production from these two sites was inferred by running RHEM with canopy cover values ranging from 0% to 100%. This changed sediment output by 111% to -91% relative to the present vegetation cover. Measures of the geometry of soil and vegetation patches at Dry-X, such as fractal dimension index and proximity index, showed a relationship to error residuals from RHEM. As the vegetation becomes less isolated, more uniform, and the tortuosity of the bare soil area increases, observed sediment decreases relative to RHEM predictions. The results of this study will help land management agencies assess the feasibility of mitigation strategies for reducing sediment and salinity loads from the saline and sodic soils of the Mancos Shale formation and indicate a possible benefit to incorporating the parameters that describe the spatial pattern of vegetation in RHEM.</p>

<p>Southwest Foods in Lafayette, Louisiana has multiple underground storage tanks that leaked petroleum products over a period of time, releasing numerous toxic constituents of concern into the surrounding soil and groundwater. During the assessment phase of risk evaluation, the Synthetic Precipitation Leaching Procedure (SPLP) test was used to measure the leaching potential of possibly contaminated soils and lithologies when exposed to acidic rainfall. However, during the site investigation, SPLP data produced erratic results that apparently are related to the type of geologic material (?soil?) involved. These erratic results could have major implications for assessment, remediation, and the establishment of Risk Evaluation/Corrective Action Program (RECAP) standards in the state of Louisiana. Incorrectly applied RECAP standards could ultimately mean contaminants of concern could reach points of exposure (POEs), and potentially harm nearby residents and the environment. Previously, lithological composition had not been considered when evaluating the environmental impact of the test. At the site, numerous geotechnical soil boring logs were completed, and soil samples were sent to analytical laboratories for analysis of contamination. Soil analytical data compiled by the laboratories along with samples acquired from multiple groundwater monitoring wells at the site provided an in-depth view into the degree of contamination at Southwest Foods and produced the first signs of erratic SPLP test results. Contour maps of contamination and groundwater potentiometric levels were created to show both the level of contaminants in soil and the possible migration paths of affected groundwater. The SPLP sample data were evaluated and categorized into lithological subgroups for further examination. The lithologies, or soil types (with USCS symbols), that produced erratic results (i.e., some ?passed? and some ?failed?) for the SPLP analyses included ?clay, high plasticity? (CH) and ?clayey silt/sandy silt/silt? (ML). The results for ?silty clay/sandy clay? (CL) were more consistent. The inconsistent SPLP data could result in incorrect application of site-specific RECAP standards and the subsequent cleanup at Southwest Foods and conceivably at other contaminated sites as well.

<p> Soil health assessment uses a combination of potential indicators affecting soil processes to comprehensively monitor soil change, caused by cropping systems and soil management. The objectives of the study were to assess the effects of selected cropping systems, soil management and landscape slope positions on the soil health characteristics of the Sanborn Field long-term experimental study in Columbia, Missouri, United States. Soil samples were collected on each of four dates over two years (8^th May 2014, 4^th September 2014, 1^st April 2016, and 18^th August 2016) from selected plots to address each objective, and these time samples were used as replications. Soil physical, chemical, and biological characteristics were analyzed in the laboratory for these samples to assess soil health using the Cornell Comprehensive Assessment of Soil Health (CASH) method. To assess soil health in this study, soil health scoring was determined used R-studio version 1.1.149 to relate the interaction of cropping systems, soil management, and slope positions. Most soil resources on Sanborn Field are a poorly-drained claypan soil classified as a Mexico silt loam (fine, smectitic, mesic Vertic Epiaqualf). In addition, soil samples collected from Tucker Prairie was used as a proxy for the original state of Sanborn Field soils. The first study was conducted to evaluate the effects of long-term cropping systems on soil health properties. The results from the characterization indicated that continuous timothy (<i>Phleum pretense</i> L.) and warm season grass treatments were classified with very high soil health scores, and the lowest score was found for continuous corn (<i>Zea mays</i> L.). In addition, results showed strong positive linear associations between soil organic carbon, total nitrogen, potentially mineralizable nitrogen, active carbon, microbial biomass, and water stable aggregates; while a strong negative linear correlation existed between each of these properties and bulk density. The second study was conducted to evaluate the effects of long-term annual applications of no fertilizer, full fertilizer, and manure on soil health measurements of selected cropping systems. Different cropping systems, including continuous corn, continuous wheat (<i>Triticum aestivum</i> L.), corn-wheat-red clover (<i>Trifolium pretense</i> L.) rotation, and corn-soybean (<i>Glycine max</i> L.)-wheat rotation treatments were used in this study. Results showed that annual dairy cow (<i>Bos Taurus </i>) manure applications had the greatest effect on all soil health indicators and had the largest overall soil health score compared to full fertility and no fertilizer treatments. Moreover, continuous wheat with manure application presented the best combination of effects on soil properties with the largest score for most soil health indicators and an overall health score of 82 out of 100 classified as very high which is the best. The last study evaluated the effects of landscape slope positions on soil health properties of the long-term experiment. Results showed that the summit position had the highest overall soil health score while the lowest score was found on the shoulder position. However, there were no significant differences along the transect slope for water-stable aggregates and bulk density. There were significant differences along the transect for the biological properties such as soil organic carbon, active carbon, potentially mineralizable nitrogen, and microbial biomass. Results of this study illustrate the effect of selected variables on soil health and provide the recent addition of using biological characteristics to account for soil health properties. It is important to remember that this study of the long-term Sanborn Field experiment is just for a small-sized plot area. Future studies of soil management effects on soil health need to account for their own field conditions and their own unique environment.</p><p>