Reducing the emissions of soil fumigants such as 1,3-dichloropropene (1,3-D) is essential to protecting air quality. Although biochar is useful in reducing such emissions, biochar-adsorbed fumigants may desorb and cause secondary air pollution. This study investigated the degradation of 1,3-D on iron (Fe)-impregnated biochar (FBC) amended with urea-hydrogen peroxide (UHP). The results indicated the degradation rate of trans-1,3-D on FBC-UHP was 54-fold higher than that on pristine biochar (PBC). Electron paramagnetic resonance (EPR) combined with other characterization methods revealed that the presence of semiquinone-type radicals in FBC effectively accelerated the Fe(III)/Fe(II) cycleto maintain enough Fe(IIII) for UHP activation and ·OH generation. ·OH, rather than ·O2-, was the dominant active oxidant. Soil column tests showed that application of FBC to the soil surface reduced cumulative 1,3-D emissions from 34.80 % (bare soil) to 0.81%. After the column experiment, the mixing of the FBC with UHP resulted in the residual cis-isomers decreasing from 32.5% to 10.5%. Greenhouse bioassays showed that mixing post-1,3-D degradation FBC-UHP with soil significantly promoted lettuce growth relative to PBC. The findings of this study provide a new approach for biochar application, especially for the emission reduction of hazardous volatile organic compounds from soil.

Observations of fumigant and pesticide emissions are needed for multiple public health and environmental protection mandates. The aerodynamic gradient method (ADM) is commonly used to measure fumigant and pesticide emissions. However, the ADM may over estimate emissions compared to other micrometeorological and modeling approaches, which would increase uncertainty over the true flux estimate. Different studies with ADM have also used multiple differing transport functions that relate concentration gradients to emissions. Therefore, we tested different and more recent transport functions to try to correct the anticipated observed higher values with ADM using observations from two sites in California, USA. We evaluated different transport functions against eddy covariance observations and found that using the functions developed by Högström (1996) corrected the ADM values to be in line with other observational methods. For the Fresno experiment, cumulative emission masses from the ADM- Högström functions were within 7% of other approaches while the Pruitt function was >15% higher. Applying the Högström functions to a series of previous fumigation experiments in California saw reductions in the ADM observations of >25% for cumulative mass emissions. The results indicate that the Högström functions should be used for future ADM experiments in the absence of more robust transport factors for local meteorological conditions. The results also illustrate how previous ADM observations could be corrected to reduce uncertainty in flux emissions estimates.

The volatile release of agricultural fumigants from soil to air is a critical concern in terms of human and environmental health. A major control on the release of fumigants from soil to air is their degradation rate within the soil; however, this is a function of human/soil/environmental conditions and their inter-relationships. For the common fumigant chloropicrin (CP), it is known that application rate has a marked effect on degradation rate, with a potential further influence on CP emissions. We conducted batch degradation studies to better understand how CP degradation rate changes in response to application rate (56, 224, 392kgha-1) under gradients of soil temperature (10, 25, and 40°C), soil moisture content (1, 8, and 15%), and organic matter content (1, 2, and 3%). A general trend of degradation rate decreasing with increasing application rate was observed across almost all such gradients, which is likely attributable to decreased microbial numbers and activity (i.e., degradation) at high (toxic) application rates. The effects of these ranges in degradation rate on emissions from soil to air were predicted using an analytical solution model, indicating that between the low and high application rates, total emissions percentage increased markedly (increases ranging from 69 to 99.8 percentage points, depending on prevalent conditions). The work will be useful to state and federal regulators in assessing the likely impact of CP use on air quality and human health.

6.7 Processes Governing Transport of Organic Solutes Sharon K. Papiernik, Sharon K. Papiernik USDA-ARS, George E. Brown, Jr. Salinity Laboratory, Riverside, CaliforniaSearch for more papers by this authorS. R. Yates, S. R. Yates USDA-ARS, George E. Brown, Jr. Salinity Laboratory, Riverside, CaliforniaSearch for more papers by this authorJ. Gan, J. Gan University of California, Riverside, CaliforniaSearch for more papers by this author Sharon K. Papiernik, Sharon K. Papiernik USDA-ARS, George E. Brown, Jr. Salinity Laboratory, Riverside, CaliforniaSearch for more papers by this authorS. R. Yates, S. R. Yates USDA-ARS, George E. Brown, Jr. Salinity Laboratory, Riverside, CaliforniaSearch for more papers by this authorJ. Gan, J. Gan University of California, Riverside, CaliforniaSearch for more papers by this author Book Editor(s):Jacob H. Dane, Jacob H. DaneSearch for more papers by this authorG. Clarke Topp, G. Clarke ToppSearch for more papers by this author First published: 01 January 2002 https://doi.org/10.2136/sssabookser5.4.c60Book Series:SSSA Book Series AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary The processes that affect the distribution, mobility, and persistence of organic solutes in soils are integral to understanding their transport in soils. Particular considerations include mass transfer among the soil, air, and water phases and abiotic and biological transformation processes. This chapter discusses the primary factors that affect the transport of organic solutes in soils and presents an overview of the methods used to obtain measures of the mass transfer and transformation processes, which are widely used as model inputs. Many experimental variables have been shown to affect the soil-water distribution of organic solutes, including pH, ionic strength, method of sample mixing, soil/solution ratio, and temperature. In addition to the methods used to experimentally determine Henry's Law constant of organic compounds, some estimation methods are available. While many organics are subject to significant photodegradation in aqueous solution, the rate of photodegradation in soils is slower because soils absorb light and quench photochemical reactions. Methods of Soil Analysis: Part 4 Physical Methods, 5.4 RelatedInformation

This review summarizes the characterization and quantification of interactions between dissolved organic matter (DOM) and estrogens as well as the effects of DOM on aquatic estrogen removal. DOM interacts with estrogens via binding or sorption mechanisms like π-π interaction and hydrogen bonding. The binding affinity is evaluated in terms of organic-carbon-normalized sorption coefficient (Log KOC) which varies with types and composition of DOM. DOM has been suggested to be a more efficient sorbent compared with other matrices, such as suspended particulate matter, sediment and soil; likely associated with its large surface area and concentrated carbon content. As a photosensitizer, DOM enhanced estrogen photodegradation when the concentration of DOM was below a threshold value, and when above, the acceleration effect was not observed. DOM played a dual role in affecting biodegradation of estrogens depending on the recalcitrance of the DOM and the nutrition status of the degraders. DOM also acted as an electron shuttle (redox mediator) mediating the degradation of estrogens. DOM hindered enzyme-catalyzed removal of estrogens while enhanced their transformation during the simultaneous photo-enzymatic process. Membrane rejection of estrogens was pronounced for hydrophobic DOM with high aromaticity and phenolic moiety content. Elimination of estrogens via photolysis, biodegradation, enzymolysis and membrane rejection in the presence of DOM is initiated by sorption, accentuating the role of DOM as a mediator in regulating aquatic estrogen removal.

Concerns about widespread contamination of surface water and groundwater aquifers by microbial pathogens have resulted in an increased interest in research of subsurface microbial transport. While bacteria and protozoa are primarily trapped between soil particles during transport, the smaller viruses are capable of greater passage through the soil. To better study the factors controlling microbial transport in the subsurface, reliable methodology is needed. This chapter presents and evaluates laboratory and field techniques that have been used by various researchers for studying microbial transport behavior in porous media. In particular, it emphasizes only virus transport, since their smaller size makes them more likely to be transported through the subsurface environment. Conventional flowthrough columns, as well as a novel continuously recirculating column, were used in laboratory viral transport studies. The batch equilibration method remains the primary method for obtaining sorption coefficient values for viruses.

This review covers liquid chromatography–mass spectrometry (LC-MS) strategies for structural elucidation of degradation and transformation products of environmental steroid hormones due to their estrogenic and/or androgenic effects on environmental living life. We focus on identification fundamentals of unknown metabolites rather than on target analysis. We discuss LC-MS capacities and overall MS-based steps for structural elucidation of unknown metabolites. Also summarized in the review are the fragmentation reactions and fragmentation pathways of protonated and deprotonated molecules of unknown compounds. We pay particular attention to versatile orthogonal techniques (e.g., isotopic labeling, hydrogen/deuterium exchange and model compound utilization) associated with MS and intelligent spectral interpretation strategies used in literature for structural elucidation of steroid hormone metabolites. We provide up-to-date applications of LC-MS on structural elucidation of biotic and abiotic transformation products of steroid hormones in environmental samples. Most of what is discussed in this review also applies to other emerging environmental contaminants.

This chapter integrates the processes of sorption, biotic and abiotic transformation, and vapor transport into chemical mass transport models that can be used to forecast environmental exposure. It emphasizes chemical transport rather than mass water flow. For completeness, the chapter includes a brief overview of water flow through saturated and unsaturated soils. Decoupling the water and chemical transport is a major assumption in the chapter. This means that the influence of the chemical is insignificant on water flow, and properties such as density gradients that can cause fluid movement can be ignored. This makes it possible to calculate the water flux independent of the chemical and then use the water fluxes in calculating the chemical flux. The most common approach to chemical transport is to consider the contaminant to be nonvolatile and miscible in the liquid phase.

Field experiments offer the most acceptable approach to quantifying agricultural fumigant emissions but there is an absence of replicated field data in reported literature. Air concentration profiles of 1,3-dichloropropene (1,3-D) were determined on duplicate masts above the center of a treated field over 14 days. Meteorological parameters were also measured. Three meteorological approaches were then used to determine the total and flux density emissions of 1,3-D. Across the three calculation methods, the averages of the duplicated measurements showed total emission losses of cis 1,3-D ranging from 27% to 36% and of trans 1,3-D ranging from 18% to 24%. The replicate measurements differed by between 1.6 and 7.7 percentage points, which we consider to be excellent replicability. Flux densities over time showed maximum emissions during the first nighttime and early morning of the day following application. A general declining trend in emission fluxes was accompanied by nighttime peaks. Flux density curves during the experiment showed excellent agreement between replicates, with linear regression of the two data sets yielding r2 values of 0.95–0.98 and slopes of 1.01–1.17. To our knowledge, this is the first time that replicated fumigant fluxes have been reported. The high degree of replicability indicates the robustness of the approaches and lends credence to previous non-replicated flux data.

Laboratory degradation tests with two model estrogen conjugates, 17 Laboratory degradation tests with two model estrogen conjugates, 17ss-estradiol-3-glucuronide (E2-3G) and 17ss-Laboratory degradation tests with two model estrogen conjugates, 17ss-estradiol-3-glucuronide (E2-3G) and 17ss-estradiol-3-glucuronide (E2-3G) and 17ss- estradiol-3-sulphate (E2-3S), using river water and sediment as inoculum under aerobic conditions were investigated. Throughout the 14-day incubation, degradation of E2-3G in river water, at environmentally-relevant level (25 ng/L), obeyed first-order kinetics with the formation of 17-ss estradiol and estrone; in contrast, E2-3S was slowly converted to estrone-3-sulphate stoichiometrically. Degradation of the two conjugates across the spiking concentrations (0.01-1 mu g/g) was much faster in sediment than in river water where 25 ng/L of conjugate standards were spiked, possibly due to relatively high population densities of microorganisms in sediment. De-conjugation of the thio-ester bond at C-3 position and oxidation at C-17 position were the predominant degradation mechanisms for E2-3G and E2-3S, respectively, with negligible presence of metabolites estrone-3-glucuronide for E2-3G and 17ss-estradiol for E2-3S. In addition, delta-9(11)-dehydroestrone and 6-ketoestrone were determined as new metabolites of the two conjugates. Also, a lactone compound, hydroxylated estrone and a few sulfate conjugates were tentatively identified. With the observation of new metabolites, biodegradation pathways of E2-3G and E2-3S were proposed. The formation of new metabolites may pose unknown risks to aquatic biota. Published by Elsevier Ltd.

Estrogen conjugates are precursors of free estrogens such as 17ß-estradiol (E2) and estrone (E1), which cause potent endocrine disrupting effects on aquatic organisms. In this study, microcosm laboratory experiments were conducted at 25°C in an agricultural soil to investigate the aerobic degradation and metabolite formation kinetics of 17ß-estradiol-3-glucuronide (E2-3G) and 17ß-estradiol-3-sulfate (E2-3S). The aerobic degradation of E2-3G and E2-3S followed first-order kinetics and the degradation rates were inversely related to their initial concentrations. The degradation of E2-3G and E2-3S was extraordinarily rapid with half of mass lost within hours. Considerable quantities of E2-3G (7.68ng/g) and E2-3S (4.84ng/g) were detected at the end of the 20-d experiment, particularly for high initial concentrations. The major degradation pathway of E2-3G and E2-3S was oxidation, yielding the primary metabolites 17ß-estrone-3-glucuronide and 17ß-estrone-3-sulfate, respectively. Common metabolites were E2, the second primary metabolite, and E1, the secondary metabolite. Additionally, ring B unsaturated estrogens and their sulfate conjugates were tentatively proposed as minor metabolites. The persistence of E2-3G and E2-3S (up to 20 d) suggests that the high rate of application of conjugated estrogen-containing substances could be responsible for the frequent detection of free estrogens in surface and subsurface water.

Soil fumigation is an important agricultural practice used to produce many vegetable and fruit crops. However, fumigating soil can lead to atmospheric emissions which can increase risks to human and environmental health. A complete understanding of the transport, fate, and emissions of fumigants as impacted by soil and environmental processes is needed to mitigate atmospheric emissions. Five large-scale field experiments were conducted to measure emission rates for 1,3-dichloropropene (1,3-D), a soil fumigant commonly used in California. Numerical simulations of these experiments were conducted in predictive mode (i.e., no calibration) to determine if simulation could be used as a substitute for field experimentation to obtain information needed by regulators. The results show that the magnitude of the volatilization rate and the total emissions could be adequately predicted for these experiments, with the exception of a scenario where the field was periodically irrigated after fumigation. In addition, the timing of the daily peak 1,3-D emissions was not accurately predicted for these experiments due to the peak emission rates occurring during the night or early-morning hours. This study revealed that more comprehensive mathematical models (or adjustments to existing models) are needed to fully describe emissions of soil fumigants from field soils under typical agronomic conditions.

Here we report enrichment from a marine-derived inoculum of a nonphotosynthetic electroactive biofilm that is capable of both consuming electricity (electrotrophy) and producing electricity (electrogenesis) from a single electrode. With the alternation of the electrode potential between -0.4 and 0.0 V-SHE every 10 min, alternating anodic and cathodic currents increased in lock step (maximum current density of +/- 1.4 +/- 0.4 A/m(2) in both modes, Coulombic efficiency of similar to 98% per chargedischarge cycle), which is consistent with alternating between generation and consumption of energy storage compounds by the biofilm. Cyclic voltammetry exhibited a single sigmoid-shaped feature spanning anodic and cathodic limiting currents centered at -0.15 V-SHE, a phenomenon not observed to date for an electroactive biofilm, and square wave voltammetry exhibited reversible peaks at -0.15 and -0.05 V-SHE, suggesting the same redox cofactor(s) facilitates electron transport at the biofilm-electrode interface in both modes. Hydrogen and carbon monoxide, known energy and/or carbon sources for cellular metabolism, but no volatile fatty acids, were detected in reactors. Cells and cell clusters were spread across the electrode surface, as seen by confocal microscopy. These results suggest that a single microbial electrochemical biofilm can alternate between storing energy and generating power, furthering the potential applicability of bioelectrochemical systems.

Increasingly stringent regulations to control soil-air emissions of soil fumigants has led to much research effort aimed at reducing emission potential. Using laboratory soil columns, we aimed to investigate the relationship between chloropicrin (CP) application rate and its emissions from soil across a wide range of CP applications (equivalent to 56–392kgha−1). In contrast to the known behavior of other fumigants, total emission percentages were strongly and positively related to application rate (i.e., initial mass), ranging from 4 to 34% across the application rate range. When combined, data from a previous study and the present study showed good overall comparability in terms of CP application rate vs. emission percentage, yielding a second-order polynomial relationship with an R2 value of 0.93 (n=12). The study revealed that mass losses of CP were strongly disproportional to application rate, also showing a polynomial relationship. Based on degradation studies, we consider that a shorter half-life (faster degradation) at lower application rates limited the amount of CP available for emission. The non-linear relationship between CP application rate and CP emissions (both as % of that applied and as total mass) suggests that low application rates likely lead to disproportionally low emission losses compared with higher application rates; such a relationship could be taken into account when assessing/mitigating risk, e.g., in the setting of buffer zone distances.

The present study investigated the occurrence of 13 parent and conjugated estrogens and progestagens in surface water of the Santa Ana River. With the exception of the synthetic hormones 17α‐ethynylestradiol and mestranol, other compounds were detected at least twice at 10 representative sites, with the ubiquitous estrone (E1) and 17β‐estradiol‐3‐sulfate as the dominant compounds quantified (0.24–6.37 ng/L and 0.49–9.25 ng/L, respectively). Sites near dairy farms exhibited high levels of conjugates, whereas those close to a sewage treatment plant (STP) effluent outlet displayed relatively high concentrations of E1. Principle component analysis coupled with multiple linear regression revealed dairy farms and the STP as the 2 significant contamination sources, accounting for 69.9% and 31.1% of the total hormone burden, respectively. Risk assessment results suggested E1 and 17β‐estradiol (E2) as the 2 hormones with the largest risks to aquatic organisms, and which combined, contributed >90% of the total estrogenicity. Most of the sites investigated showed that E1 and E2 posed a medium risk (0.1 < risk quotient < 1), whereas each induced a high risk (risk quotient >1) at sites severely impacted by the STP and dairy farms. These results suggest that river health would benefit from effective treatment of waste at the STP and dairy farms prior to discharge. Environ Toxicol Chem 2016;35:2657–2664. © 2016 SETAC

Emissions of volatile soil fumigant 1,3-dichloropropene (1,3-D) from soil to air are a significant concern in relation to air quality, and cost-effective strategies to reduce such emissions are urgently required by growers to help them comply with increasingly stringent regulations. In this work, application of a rice husk-derived biochar to the surface of a sandy loam soil chamber reduced soil-air emissions of 1,3-D from 42% in a control (no biochar) to 8% due to adsorption onto the biochar. This adsorbed 1,3-D showed a potential for re-volatilization into air and solubilization into the soil-liquid phase. Biochar at the soil surface also reduced soil-gas concentrations in the upper soil; based on the determination of concentration-time values, this may limit 1,3-D-induced nematode control in the upper soil. In batch studies, the mixing of biochar into the soil severely limited nematode control; 1,3-D application rates around four times greater than the maximum permissible limit would be required to give nematode control under such conditions. Therefore, the use of biochar as a surface amendment, while showing an emission reduction benefit, may limit pest control during subsequent fumigations if, as seems probable, it is plowed into the soil.