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Mammalian decomposition provides pulses of organic matter to the local ecosystem creating ephemeral hotspots of nutrient cycling. While changes to soil biogeochemistry in these hotspots have been described for C and N, patterns associated with deposition and cycling of other elements have not received the same attention. The goal of our study was to evaluate temporal changes to a broad suite of dissolved elements in soils impacted by human decomposition on the soil surface including: 1) abundant mineral elements in the human body (K, Na, S, P, Ca, and Mg), 2) trace elements in the human body (Fe, Mn, Se, Zn, Cu, Co, and B), and 3) Al which is transient in the human body but common in soils. We performed a four-month human decomposition trial at the University of Tennessee Anthropology Research Facility and quantified elemental concentrations dissolved in the soil solution, targeting the mobile and bioavailable fraction. We identified three groups of elements based on their temporal patterns. Group 1 elements appeared to be cadaver-derived (Na, K, P, S) and their persistence in soil varied based upon soluble organic forms (P), the dynamics of the soil exchange complex (Na, K), and gradual releases attributable to microbial degradation (S). Group 2 elements (Ca, Mg, Mn, Se, B) included three elements that have greater concentrations in soil than would be expected based on cadaver inputs alone, suggesting that these elements partially originate from the soil exchange (Ca, Mg), or are solubilized as a result of soil acidification (Mn). Group 3 elements (Fe, Cu, Zn, Co, Al) increased late in the decomposition process, suggesting a gradual solubilization from soil minerals under acidic pH conditions. This work presents a detailed longitudinal characterization of changes in dissolved soil elements during human decomposition furthering our understanding of elemental deposition and cycling in these environments.

Metformin is an anti‐diabetic drug that has received increased environmental attention due to probable toxic effects on aquatic ecosystems. Although several studies reported metformin adsorption on soils and minerals, spectroscopic evidence of adsorption mechanisms is limited. Thus, we evaluated metformin adsorption mechanisms on gibbsite and a Tennessee soil (Loring silt loam) using in situ attenuated total reflectance Fourier transform infrared (FTIR) spectroscopy. FTIR results (wavenumber shifts at 1638, 1570, and 1499 cm−1) suggested that 250 µM metformin interacts with soil and gibbsite through the lone pair of electrons on N atoms (N5, N6, or N7 moieties) and delocalized electrons in N3‐N5‐N6 systems. For soil, metformin may additionally bind via cation exchange in the inter‐layer spaces of permanent charge minerals. Direct spectroscopic evidence corroborates earlier studies and provides focus for future investigations to elucidate the fate of metformin at the soil–water interface, depending on different soil physicochemical properties and mineralogy. Core Ideas Metformin showed adsorption affinity for Tennessee soil and model mineral gibbsite at natural pH of 6.5. Changes in infrared bands of aqueous metformin spectra due to pH variation are consistent with reported pKa values. Spectroscopic results indicated adsorption of metformin on soil via combinations of cation exchange and electrostatic attractions. For gibbsite, the metformin adsorption was mainly by electrostatic attraction. Plain Language Summary Metformin is a new pollutant in US water that has recently received more attention because it may harm ecosystems. Several important studies have investigated the characteristics of metformin adsorption on different soils and minerals but direct interpretation on the mechanism is lacking. Our study provided an improved knowledge on the metformin binding on soil and minerals. Fate of Metformin in the Environment.

The environmental mobility of antimony (Sb) is largely unexplored in geochemical environments. Iron oxide minerals are considered major sinks for Sb. Among the different oxidation states of Sb, (+) V is found more commonly in a wide redox range. Despite many adsorption studies of Sb (V) with various iron oxide minerals, detailed research on the adsorption mechanism of Sb (V) on hematite using macroscopic, spectroscopic, and surface complexation modeling is rare. Thus, the main objective of our study is to evaluate the surface complexation mechanism of Sb (V) on hematite under a range of solution properties using macroscopic, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic, and surface complexation modeling. The results indicate that the Sb (V) adsorption on hematite was highest at pH 4–6. After pH 6, the adsorption decreased sharply and became negligible above pH 9. The effect of ionic strength was negligible from pH 4 to 6. The spectroscopic results confirmed the presence of inner- and outer-sphere surface complexes at lower pH values, and only outer-sphere-type surface complex at pH 8. Surface complexation models successfully predicted the Sb (V) adsorption envelope. Our research will improve the understanding of Sb (V) mobility in iron-oxide-rich environments.

Laser-induced breakdown spectroscopy (LIBS) is an elemental analysis technique that is based on the measurement of atomic emissions generated on a sample surface by a laser-induced microplasma. Although often recognized in the literature as a well-established analytical technique, LIBS remains untested relative to the quantitative analysis of elements in chemically complex matrices, such as soils. The objective of this study was to evaluate the capabilities of LIBS relative to the elemental characterization of surface soils. Approximately 65 surface soil samples from the Pond Creek watershed in east Tennessee were collected and subjected to total dissolution and elemental analysis by inductively coupled argon plasma-optical emission spectroscopy (ICP-OES). The samples were analyzed by LIBS using a Nd:YAG laser at 532 nm, with a beam energy of 25 mJ per pulse, a pulse width of 5 ns, and a repetition rate of 10 Hz. The wavelength range for the LIBS spectra collection was 200 to 600 nm, with a resolution of 0.03 nm. Elemental spectral lines were identified through the analysis of analytical reagent-grade chemicals and the NIST and Kurucz spectral databases. The elements that dominated the LIBS spectra were Al, Ca, Fe, and Mg. In addition, emission lines for Ti, Ba, Na, Cu, and Mn were isolated. The emission lines of Cr, Ni, and Zn, which were >100 mg kg-1 in numerous soil samples, were not detected. Further, spectral emission lines for P and K are >600 nm, eliminating them from LIBS analysis. The integrated peak areas of interference-free elemental emission lines were determined, then normalized to the area of the 288.16 nm Si(I) emission (internal standard) to reduce the variability between replicate analyses. The normalized spectral areas, coupled with linear regression (standard curves for single wavelength response) and multivariate techniques (chemometrics and multiple wavelengths), were used to predict ICP-OES elemental data. In general, the quantitative capabilities of LIBS proved disappointing. Detection and quantitation were generally restricted to those elements with concentrations > 0.5 g kg-1. The correlation between LIBS response and elemental content was poor (r < 0.98). Further, the relative errors of prediction for the LIBS-detected elements were less than acceptable for an analytical technique (<20%), ranging from 20 to 40% using linear regression analysis, and from 18 to 48% using partial least squares analysis. Based on these findings, the analytical capability of the LIBS method for soil metals analysis should be considered questionable.

New urease and nitrification inhibitors and polymer coatings were introduced in recent years, but their effects on N loss and plant N nutrition were scarcely examined in agronomic no-tillage production systems. A field experiment of urea treated with efficiency enhancers was conducted on no-tillage corn ( Zea mays L.) in Tennessee, the USA during 2013–2015. A field experiment on urea and ammonium nitrate (UAN) treated with efficiency enhancers was carried out on no-tillage corn in Tennessee in 2014 and 2015. Urea treated with N-(n-butyl) thiophosphoric triamide (NBPT) at concentrations of 20% (NBPT 1 ), 26.7% (NBPT 2 ), or 30% (NBPT 3 ) and polymer coated urea (PCU) were effective but maleic-itaconic copolymer treated urea was ineffective in reducing ammonia volatilization loss and improving N nutrition, grain yield, and N agronomic use efficiency of corn compared with untreated urea. Specifically, NBPT 1 , NBPT 2 , or NBPT 3 treated urea and PCU reduced the total ammonia volatilization loss by 29.1–78.8%, 35.4–81.9%, 77.3–87.4%, and 59.1–83.3% during the 20 days after N applications, but increased grain yield by 15.6–31.4%, 12.9–34.8%, 18.7–19.9%, and 14.6–41.1%, respectively. The inhibitory effect of NBPT on ammonia volatilization did not improve with NBPT concentration increased from 20% to 30%. UAN treated with NBPT 3 or a combination of urease and nitrification inhibitors resulted in 16.5–16.6% higher corn yield than untreated UAN only when they were surface applied. In conclusion, when urea-containing fertilizers are surface applied without any incorporation into the soil under no-tillage, their use efficiencies and performances on corn can be enhanced with an effective urease inhibitor in areas and years with noticeable urea N losses.

Cell wall recalcitrance poses a major challenge on cellulosic biofuel production from feedstocks such as switchgrass (Panicum virgatum L.). As lignin is a known contributor of recalcitrance, transgenic switchgrass plants with altered lignin have been produced by downregulation of caffeic acid O‐methyltransferase (COMT). Field trials of COMT‐downregulated plants previously demonstrated improved ethanol conversion with no adverse agronomic effects. However, the rhizosphere impacts of altering lignin in plants are unknown. We hypothesized that changing plant lignin composition may affect residue degradation in soils, ultimately altering soil processes. The objective of this study was to evaluate effects of two independent lines of COMT‐downregulated switchgrass plants on soils in terms of chemistry, microbiology, and carbon cycling when grown in the field. Over the first two years of establishment, we observed no significant differences between transgenic and control plants in terms of soil pH or the total concentrations of 19 elements. An analysis of soil bacterial communities via high‐throughput 16S rRNA gene amplicon sequencing revealed no effects of transgenic plants on bacterial diversity, richness, or community composition. We also did not observe a change in the capacity for soil carbon storage: There was no significant effect on soil respiration or soil organic matter. After five years of establishment, δ13C of plant roots, leaves, and soils was measured and an isotopic mixing model used to estimate that 11.2 to 14.5% of soil carbon originated from switchgrass. Switchgrass‐contributed carbon was not significantly different between transgenic and control plants. Overall, our results indicate that over the short term (two and five years), lignin modification in switchgrass through manipulation of COMT expression does not have an adverse effect on soils in terms of total elemental composition, bacterial community structure and diversity, and capacity for carbon storage. Collecting soil samples from experimental plots grown with transgenic switchgrass (Panicum virgatum L.) with altered lignin.

Weed communities may potentially reduce row‐crop yields resulting in a loss of revenue for producers. Studies have reported a decrease in the efficacy of chemical methods of weed control due to increased weed resistance. With the goal of reducing reliance on chemical weed control and promoting sustainable crop production in mind, we evaluated different winter cover crop (CC) types (single‐, double‐, and multi‐species) and CC planting methods (broadcasting vs. drilling) on CC and weed groundcover and row‐crop yield in a no‐till corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation system in Tennessee from 2013 to 2017. Our results showed that winter CC reduced spring weed ground coverage by 64–76% compared with winter fallow with no herbicide application. A five‐species CC mixture increased soybean yields by 6 to 8.5% across seeding method treatments compared with other CC treatments and winter fallow. This yield increase was more visible in a drought year. Corn, grown in years with normal weather patterns, did not show a yield response to CC types. From this study, cover cropping was found to be an effective strategy for weed control compared with leaving the field fallow without herbicide application following row‐crop harvest; however, no consistent species‐specific trends were observed on weed suppression and row‐crop yield. Future research should focus on understanding CC species composition and biomass production in double‐ and multi‐species mixtures from this field experiment to draw robust conclusions on agronomic responses of individual CC species and planting methods.

Land application of manure can change soil chemical properties, thus affecting fate and mobility of agricultural antibiotics in soil. The main objective of this study was to examine the effects of dissolved organic C (DOC) and background electrolyte cation type on the sorption and transport of chlortetracycline (CTC), tylosin (TYL), and sulfamethazine (SMT) in two different soils. A series of batch isotherm and column miscible displacement experiments were conducted using surface and subsurface soils of Etowah clay loam (fine‐loamy, siliceous, semiactive, thermic Typic Paleudults) and Captina sandy loam (fine‐silty, siliceous, active, mesic Typic Fragiudults). Decreased retention of CTC and TYL to soils was observed in the presence of Ca2+ ion compared with Na+. For example, the Freundlich coefficient (KF) for TYL ranged from 67 to 341 under a Na+ system while it ranged from 17 to 173 under a Ca2+ system. Sorption of CTC and TYL decreased on the addition of DOC extracted from dairy manure, while SMT sorption increased by DOC addition. For example, in the Ca2+ system, CTC KF values without DOC ranged from 2.40 × 103 to 4.84 × 103 while they ranged from 1.52 × 103 to 2.86 × 103 with the addition of DOC. Column transport experiments generally agreed with the batch study results, showing increased CTC mass recovery in effluents (i.e., increased from 2.1–4.3% for both surface and subsurface soils) and decreased retardation factors (R) in the presence of dairy manure DOC (i.e., from 890–371). The reduced CTC adsorption may be explained by competition between the DOC and CTC for sorption sites or by the aqueous association of CTC with DOC. Elevated levels of DOC also resulted in increased mobility of TYL and SMT for surface soil column. In summary, changes in background electrolyte cation type and DOC level in soil solution caused by addition of animal manure can influence fate and transport of agricultural antibiotics in soils.

Human decomposition in terrestrial ecosystems is a dynamic process creating localized hot spots of soil microbial activity. Longer-term (beyond a few months) impacts on decomposer microbial communities are poorly characterized and do not typically connect microbial communities to biogeochemistry, limiting our understanding of decomposer communities and their functions. We performed separate year-long human decomposition trials, one starting in spring, another in winter, integrating bacterial and fungal community structure and abundances with soil physicochemistry and biogeochemistry to identify key drivers of microbial community change. In both trials, soil acidification, elevated microbial respiration, and reduced soil oxygen concentrations occurred. Changes in soil oxygen concentrations were the primary driver of microbial succession and nitrogen transformation patterns, while fungal community diversity and abundance was related to soil pH. Relative abundance of facultative anaerobic taxa (Firmicutes and Saccharomycetes) increased during the period of reduced soil oxygen. The magnitude and timing of the decomposition responses were amplified during the spring trial relative to the winter, even when corrected for thermal inputs (accumulated degree days). Further, soil chemical parameters, microbial community structure, and fungal gene abundances remained altered at the end of 1 year, suggesting longer-term impacts on soil ecosystems beyond the initial pulse of decomposition products.

PurposeRiver impoundments disrupt natural water flow patterns and sediment distribution throughout the impacted reach, which often results in a damaging effect on aquatic ecosystems. Dam removal can release sediments that may contain fugitive agricultural nutrients and organochlorine pesticide residues (OCPRs).MethodsSediment samples from an impoundment on the Oostanaula Creek (HUC 03,565,432) in Athens, Tennessee, were obtained, as were surface soil samples from the agricultural watershed. A subset of cores were used for simulated weathering, and all samples were extracted and analyzed for nutrients and OCPRs.ResultsThe impoundment sediments tested low in P and K, but sediment pore water contained elevated concentrations of NO3, NH4, and SO4 relative to reservoir water. Endrin aldehyde and p,p’-DDD were commonly detected in sediment and soil, while aldrin, dieldrin, and p,p’-DDE occurred in a smaller number of samples. When detected, dieldrin and endrin aldehyde frequently exceeded the threshold effect concentration (TEC), but never exceeded the probable effect concentration (PEC) in the sediment samples; p,p’-DDD always exceeded TEC and exceeded PEC in 49% of the sediment samples. The concentrations of NO3 and NH4 in the weathered sediment leachates were similar to those in the reservoir water, and NH4 became the dominant cation in leachates at the conclusion of simulated weathering. Weathering decreased sediment p,p’-DDD concentrations to less than the PEC; however, the concentrations of other OCPRs were not influenced.ConclusionThe dam sediments may have harmful effects on sediment-dwelling organisms and a long-term impact on stream reclamation following low-head dam removal.