Integrating molecular descriptors for enhanced prediction: Shedding light on the potential of pH to model hydrated electron reaction rates for organic compounds.

Hydrated electron reaction rate constant (ke-aq) is an important parameter to determine reductive degradation efficiency and to mitigate the ecological risk of organic compounds (OCs). However, OC species morphology and the concentration of hydrated electrons (e-aq) in water vary with pH, complicating OC fate assessment. This study introduced the environmental variable of pH, to develop models for ke-aq for 701 data points using 3 descriptor types: (i) molecular descriptors (MD), (ii) quantum chemical descriptors (QCD), and (iii) the combination of both (MD + QCD). Models were screened using 2 descriptor screening methods (MLR and RF) and 14 machine learning (ML) algorithms. The introduction of QCDs that characterized the electronic structure of OCs greatly improved the performance of models while ensuring the need for fewer descriptors. The optimal model MLR-XGBoost(MD + QCD), which included pH, achieved the most satisfactory prediction: R2tra = 0.988, Q2boot = 0.861, R2test = 0.875 and Q2test = 0.873. The mechanistic interpretation using the SHAP method further revealed that QCDs, polarizability, volume, and pH had a great influence on the reductive degradation of OCs by e-aq. Overall, the electrochemical parameters (QCDs, pH) related to the solvent and solute are of significance and should be considered in any future ML modeling that assesses the fate of OCs in aquatic environment.

Seasonal differences in trace metal concentrations in the major rivers of the hyper-arid southwestern Andes basins of Peru.

The southern rivers of Peru originate in the Andes Mountains and flow in a southwestern direction to the Pacific Ocean through one of the most hyper-arid regions of the world. During each sub-equatorial summer from December to February, rains and snow melt in the Andes increase the streamflow in these rivers, even as they pass through the 100 km arid zone to the ocean. This study quantified seasonal dynamics of 34 trace metal elements (TM) and other constituent concentrations in four southern river basins of Peru (Chili-Quilca, Tambo, Camana-Majes-Colca, and Ocoña) during 2019-2020. Consistent with previous studies, we observed that: (1) the river water in the southern basins had relatively high concentrations of B, As, Fe, Al, Mn, P, Pb and Ni, with As the most ubiquitous toxic TM in all the basins, often detected at concentrations surpassing Peruvian and USEPA regulated concentrations; and (2) basins with the most to least toxic TM contamination were the Tambo > Chili-Quilca > Camana-Majes-Colca > Ocoña. Seasonal streamflow strongly influenced the concentrations of twenty TM, with 15 TM (Al, Au, Ba, Cd, Co, Cu, Fe, Gd, Mn, Ni, P, Pb, Ti, Yb and Zr) consistently higher in the wet season, and with As, B, Ge, Li, and Pd higher in the dry season. Our results improve the understanding of seasonal variability and vulnerability in western Andes superficial water sources, which are highly influenced by both local geogenic and anthropogenic conditions. A Spanish translation of this paper is available in the online Supplementary Material.

Slow Sand Filters for the 21st Century: A Review.

Safe drinking water remains a major global challenge, especially in rural areas where, according to UNICEF, 80% of those without access to improved water systems reside. While water, sanitation, and hygiene (WASH)-related diseases and deaths are common outcomes of unsafe water, there is also an economic burden associated with unsafe water. These burdens are most prominent in rural areas in less-developed nations. Slow sand filters (SSFs), or biological sand filters (BSFs), are ideal water treatment solutions for these low-resource regions. SSFs are the oldest municipal drinking water treatment systems and improve water quality by removing suspended particles, dissolved organic chemicals, and other contaminants, effectively reducing turbidity and associated taste and odor problems. The removal of turbidity and dissolved organic compounds from the water enables the use of low-cost disinfection methods, such as chlorination. While the working principles of slow sand filtration have remained the same for over two centuries, the design, sizes, and application of slow sand filters have been customized over the years. This paper reviews these adaptations and recent reports on performance regarding contaminant removal. We specifically address the removal of turbidity and microbial contaminants, which are of great concern to rural populations in developing countries.

Chemical-free pressure washing system as pretreatment to harvest cathode materials.

Recycling cathode materials from spent lithium-ion batteries has the potential to reduce damages to the environment and human health due to hazardous waste treatment, and mitigate supply risks of raw materials. Related political incentives or regulations have led to increased research and development efforts on cathode recycling. Promising approaches include direct recycling and hydrometallurgical processes, where delamination is the first step after collection of cathodes. In this study, we examined a pressure washing system's ability to harvest cathode materials. A high-pressure water jet provides strong forces to overcome the adhesion provided by organic binders. Four factors (water pressure, distance between nozzle and cathode, incident angle of water jet, and nozzle type) were investigated using a 34-1 fractional factorial design to screen important parameters and find the optimal conditions. Compared with other delamination processes where chemical reagents and heating are involved, the chemical-free pressure washing system can achieve separation in a few seconds (∼74 min/m2) at room temperature, which remarkably improves the efficiency of delamination. The particle size of recycled products (D50 of 31.87 µm) is significantly reduced without Al contamination from current collectors or morphological damages. In addition, three types of recycled cathode materials were used as inputs for the acid leaching process. High leaching efficiencies of lithium (>90 %) and cobalt (>85 %) suggest that the pressure washing system could be a practical, economical, and eco-friendly pretreatment process to harvest cathode materials.

Emergency responder and public health considerations for plastic sewer lining chemical waste exposures in indoor environments.

The cured-in-place pipe (CIPP) manufacturing process is used to repair buried pipes, and its waste commonly discharged into the air can enter nearby buildings. Exposure can prompt illness and the need for medical care. A mass balance model was applied to estimate indoor styrene concentrations due to intrusion of CIPP emissions through plumbing under different bathroom ventilation conditions. To better understand building contamination and recommend emergency response actions, calculations to estimate chemical intrusion through plumbing were developed. Field reports and study calculations showed that contractor-applied external pressures during plastic manufacture have and can displace plumbing trap water seals. Modeled styrene vapor concentrations that entered the building (1, 300, 1000 ppm) were similar to those measured at CIPP worksites. Modeling revealed that in some cases, bathroom exhaust fan operation during a CIPP project may increase indoor styrene concentrations due to enhanced entrainment of styrene-laden air from the sink and toilet. However, styrene concentrations decreased with increasing air leakage across the bathroom door due to reduced suction from the plumbing system. CIPP waste discharge should be treated as a hazardous material release and can pose a threat to human health. Immediate building evacuation, respiratory protection, provision of medical assistance, source elimination, and building decontamination are recommended.

Polyethylene-water partition coefficients for polychlorinated biphenyls: Application of QSPR predictions models with experimental validation.

The water environmental recalcitrance and ecotoxicity caused by polychlorinated biphenyls (PCBs) are international issues of common concern. The partition coefficients with PCBs between low-density polyethylene (LDPE) and water (KPE-w) are significant to assess their environmental transport and/or fate in aquatic environment. Even moderately hydrophobic PCBs, however, possess large KPE-w values, which makes directly experimental measurement labored. Here, based on the combination of quantitative structure-property relationships (QSPRs) and machine-learning algorithms, 10 in-silico models are developed to provide a quick estimate of KPE-w. These models exhibit good goodness-of-fit (R2adj: 0.919-0.975), robustness (Q2LOO: 0.870-0.954) and external prediction performances (Q2ext: 0.880-0.971), providing a speedy feasibility to close data gaps for limited or absent experimental information, especially the RF-2 model. Particularly, an additional experimental verification is performed for models by a rapid and accurate three-phase system (aqueous phase, surfactant micelles and LDPE). The results of the experiments for 16 PCBs show the modeling results agree well with experimental values, within or approaching the residuals of ± 0.3 log unit. Mechanism interpretations imply that the number of chlorine atoms and ortho-substituted chlorines are the great effect parameters for KPE-w. This result also heightens interest in measuring and predicting the KPE-w values of chemicals containing halogen atoms in water.

Development of novel experimental and modelled low density polyethylene (LDPE)-water partition coefficients for a range of hydrophobic organic compounds.

Knowledge about partitioning constants of hydrophobic organic compounds (HOCs) between the polymer and aqueous phases is critical for assessing chemical environmental fate and transport. The conventional experimental method is characterized by large discrepancies in the measured values due to the limited water solubility of HOCs and other associated issues. In the current work, a novel three-phase partitioning system was evaluated to determine accurate low-density polyethylene (LDPE)-water partition coefficients (KPE-w). By adding sufficient surfactant (Brij 30) to form the micellar pseudo-phase within the polymer/water system, the KPE-w values were obtained from a combination of two experimentally measured values, that is, the micelle-water partition coefficient (Kmic-w) and the LDPE-micelle partition coefficient (KPE-mic). The method presented here is capable of shortening the equilibration time to half a month, and avoiding defects of the traditional method with respect to directly measured aqueous phase concentrations. Herein, the KPE-w values were determined for HOCs with little errors. Meanwhile, based on the 120 experimental KPE-w data, several in silico models were also developed as valid extrapolation tools to estimate missing or uncertain values. Analysis of the underlying solubility interactions in the nonionic surfactant micelles were investigated, providing additional support for the reliability of the proposed method.

Effects of ferric ion on the photo-treatment of nonionic surfactant Brij35 washing waste containing 2,2',4,4'-terabromodiphenyl ether.

The effects of ferric iron on the photo-treatment of simulated BDE-47 (2,2',4,4'- terabromodiphenyl ether)-Brij35 (Polyoxyethylene lauryl ether) washing waste were studied to evaluate the influences of ferric iron on BDE-47 removal and Brij35 recovery. The results show that Fe3+ accelerated BDE-47 degradation at lower concentrations (<0.5 mM) but attenuated it at higher concentrations (0.5-5 mM) and that Brij35 loss was increased with increasing Fe3+. These results likely are caused by changes in the rate of •OH production due to the ferric ion, association of Fe3+ and electron transfer from Brij35, and light attenuation at high concentration. The BDE-47 and Brij35 had different degradation rates at different pH values and at different dissolved oxygen concentrations. The BDE-47 products were identified by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). The results indicated that BDE-47 transformed into mainly lower-brominated products, a few bromodibenzofurans, some rearrangement products, and some hydroxylated polybrominated diphenyl ethers. A series of Brij35 oxidization products were detected by ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS), including hydroxylation products, carboxylation products, and some hydrophilic chain-breaking products. Brij35 was mainly oxidized by Fe3+ and/or reactive oxygen species (ROS) with the final products of CO2 and H2O. The iron ions apparently cycled from ferric to ferrous ions in the micelles such that the Fe3+-Brij35 complex dominated the main redox reaction, leading to both BDE-47 and Brij35 degradation. It appears that in any applied soil washing system, the ferric ions in the washing waste need to be removed because of the adverse effects on BDE-47 removal and eluate reuse.

An emerging mobile air pollution source: outdoor plastic liner manufacturing sites discharge VOCs into urban and rural areas.

The in situ manufacture of cured-in-place-pipe (CIPP) plastic liners in damaged sewer pipes is an emerging mobile source of anthropogenic air pollution. Evidence indicates volatile organic compounds (VOCs) can be released before, during, and after manufacture. The chemical composition of a popular uncured styrene-based CIPP resin was examined, along with the VOCs that remained in the new cured composite. The roles of curing temperature and heating time in waste discharged into the air were examined. Uncured resin contained approximately 39 wt% VOCs. Multiple hazardous air pollutants were present, however, 61 wt% of the uncured resin was not chemically identified. A substantial mass of VOCs (8.87 wt%) was emitted into the air during manufacture, and all cured composites contained about 3 wt% VOCs. Some VOCs were created during manufacture. Curing temperature (65.5-93.3 °C) and heating time (25-100 min) did not cause different composite VOC loadings. High styrene air concentrations inhibited the detection of other VOCs in air. It is estimated that tens of tons of VOCs may be emitted at a single CIPP manufacturing site. Regulators should consider monitoring, and potentially regulating, these growing mobile air pollution and volatile chemical product sources as they are operating in urban and rural areas often in close proximity to residential and commercial buildings.

Time series analysis of water use and indirect reuse within a HUC-4 basin (Wabash) over a nine year period.

Anthropogenic water use and reuse represent major components of the water cycle. In the context of climate change, water reuse and recycling are considered necessary components for an integrated water management approach. Unplanned, or de facto, indirect water reuse occurs in most of the U.S. river systems, however, there is little real-time documentation of it. Despite the fact that there are national and state agencies that systematically collect data on water withdrawals and wastewater discharges, their databases are organized and managed in a way that makes it challenging to use them for water resource management analysis. The ability to combine reported water data to perform large scale analysis about water use and reuse is severely limited. In this paper, we apply a simple but effective methodology to complete a time series watershed-scale analysis of water use and unplanned indirect reuse for the Wabash River Watershed. Results document the occurrence of indirect water reuse, ranging from 3% to 134%, in a water-rich area of the U.S. The time series analysis shows that reported data effectively describe the water use trends through nine years, from 2009 to 2017, clearly reflecting both anthropogenic and natural events in the watershed, such as the retirement of thermoelectric power plants, and the occurrence of an extreme drought in 2012. We demonstrate the feasibility and significance of using available water datasets to perform large scale water use analysis, describe limitations encountered in the process, and highlight areas for improvement in water data management.

Decomposition of complexed Pb(II) and subsequent adsorption of Pb(II) with yolk-shell Fe3O4@ hydrous zirconium oxide sphere.

Purification of water containing heavy metals that are complexed by organic chelating agents remains a challenging task. In this study, a yolk-shell Fe3O4@hydrous zirconium oxide (Zr(OH)x) sphere sphere (YHZOs) nanomaterial was evaluated for its ability to remove ethylene diamine tetraacetic acid complexed Pb2+ (Pb-EDTA) from aqueous solution. Specifically, it is hypothesized that upon addition of H2O2, the Fe3O4 core of YHZOs served as a Fenton-type catalyst that results in oxidation of the Pb-complexed EDTA, and the Zr(OH)x shell acted as an adsorbent, removing the released Pb2+ from solution. From an aqueous solution containing 0.1 mM Pb-EDTA at pH 5, 0.5 g/L YHZOs, and 20 mM H2O2, TOC reduction and Pb removal were determined to be 65.3% and 89.8%, respectively. HPLC-MS, IC and continuous flow analyzer results identified major intermediates of EDTA decay to be ethylenediaminetriacetate, (ED3A), ethylenediamine-N,N'-diacetate (ED2A), nitrilotriacetate (NTA), iminodiacetate (IDA), ethylenediamine (EDA), acetic acid, formic acid, oxalic acid, ammonia, and nitrate, with the first 5 species having some affinity to remain complexed to Pb2+. The adsorption of Pb2+ onto the Zr(OH)x shells was confirmed by scanning transmission electron microscopy (STEM) with mapping and X-ray photoelectron spectra (XPS). Moreover, the Pb2+-adsorbed YHZOs could be easily recovered due to their magnetic properties, with the Pb2+ rinsed from them at low pH. Indeed, reused for five cycles showed only minor capacity loss. These findings suggest that the removal of chelated Pb2+ from water, and presumably other heavy metals, by yolk-shell Fe3O4@Zr(OH)x may prove to be a useful technology for some contaminated waters.

Considerations for emission monitoring and liner analysis of thermally manufactured sewer cured-in-place-pipes (CIPP).

Cured-in-place-pipes (CIPP) are plastic liners chemically manufactured inside existing damaged sewer pipes. They are gaining popularity in North America, Africa, Asia, Europe, and Oceania. Volatile and semi-volatile organic compound (VOC/SVOC) emissions from storm sewer CIPP installations were investigated at a dedicated outdoor research site. Tedlar bag, sorbent tube, and photoionization detector (PID) air sampling was conducted for five steam-CIPP installations and was coupled with composite characterizations. New CIPPs contained up to 2.21 wt% volatile material and only 6-31% chemical mass extracted per CIPP was identified. Each 6.1 m [20 ft] liner contained an estimated 5-10 kg [11-22 lbs] of residual chemical. Extracted chemicals included hazardous air pollutants and suspected and known carcinogens that were not reported by others. These included monomers, monomer oxidation products, antioxidants, initiator degradation products, and a plasticizer. PID signals did not accurately represent styrene air concentration differing sometimes by 10s- to 1000s-fold. Multiple VOCs found in air samples likely affected PID responses. Styrene (>86.4 ppmv) and methylene chloride (>1.56 ppmv) air concentrations were likely greater onsite and phenol was also detected. Additional studies are needed to examine pollutant emissions so process monitoring can be improved, and environment impacts and associated human exposures can be minimized.

Outdoor manufacture of UV-Cured plastic linings for storm water culvert repair: Chemical emissions and residual.

Storm water culverts are integral for U.S. public safety and welfare, and their mechanical failure can cause roadways to collapse. To repair these buried assets, ultraviolet (UV) light cured-in-place-pipes (CIPP) are being installed. Chemical emission and residual material left behind from the installation process was investigated in New York and Virginia, USA. Samples of an uncured resin tube and field-cured styrene-based resin CIPPs were collected and analyzed. Also collected were air and water samples before, during, and after installations. Chemicals were emitted into air because of the installation and curing processes. Particulates emitted into the air, water, and soil contained fiberglass, polymer, and contaminants, some of which are regulated by state-level water quality standards. The uncured resin tube contained more than 70 chemical compounds, and 19 were confirmed with analytical standards. Compounds included known and suspected carcinogens, endocrine disrupting compounds, hazardous air pollutants, and other compounds with little aquatic toxicity data available. Compounds (14 of 19 confirmed) were extracted from the newly installed CIPPs, and 11 were found in water samples. Aqueous styrene (2.31 mg/L), dibutyl phthalate (12.5 µg/L), and phenol (16.7 µg/L) levels exceeded the most stringent state water quality standards chosen in this study. Styrene was the only compound that was found to have exceed a 48 h aquatic toxicity threshold. Newly installed CIPPs contained a significant amount volatile material (1.0 to > 9.0 wt%). Recommendations provided can reduce chemical emission, as well as improve worksite and environmental protection practices. Recommended future research is also described.

Investigation of the factors that influence lead accumulation onto polyethylene: Implication for potable water plumbing pipes.

The influence of polymer aging, water pH, and aqueous Pb concentration on Pb deposition onto low density polyethylene (LDPE) was investigated. LDPE pellets were aged by ozonation at 85 °C. ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analysis of aged LDPE surfaces showed that a variety of polar functional groups (>CO<, >CO, >COO) were formed during aging. These functional groups likely provided better nucleation sites for Pb(OH)2 deposition compared to new LDPE, which did not have these oxygen-containing functional groups. The type and amount of Pb species present on these surfaces were evaluated through XPS. The influence of exposure duration on Pb deposition onto LDPE was modeled using the pseudo-first-order equation. Distribution ratios of 251.5 for aged LDPE and 69.3 for new LDPE showed that Pb precipitates had greater affinity for the surface of aged LDPE compared to new LDPE. Aged LDPE had less Pb surface loading at pH 11 compared to loading at pH 7.8. Pb surface loading for aged LDPE changed linearly with aging duration (from 0.5-7.5 h). Pb surface loading on both new and aged LDPE increased linearly with increasing Pb initial concentration. Greater Pb precipitation rates were found for aged LDPE compared to new LDPE at both tested pH values.

Anion Exchange on Cationic Surfactant Micelles, and a Speciation Model for Estimating Anion Removal on Micelles during Ultrafiltration of Water.

Surfactant micelles combined with ultrafiltration can partially, or sometimes nearly completely, separate various ionic and nonionic pollutants from water. To this end, the selectivity of aqueous micelles composed of either cetyltrimethylammonium (CTA+) bromide or cetylpyridinium (CP+) chloride toward many environmentally relevant anions (IO3-, F-, Cl-, HCO3-, NO2-, Br-, NO3-, H2PO4-, HPO42-, SO42-, and CrO42-) was investigated. Selectivity coefficients of CTA+ micelles (with respect to Br-) and CP+ micelle (with respect to Cl-) for these anions were evaluated using a simple thermodynamic ion exchange model. The sequence of anion affinity for the CTA+ micelles and for the CP+ micelles were the same, with decreasing affinity occurring in the order of: CrO42- > SO42- > HPO42- > NO3- > Br- > NO2- > Cl- > HCO3- > H2PO4- ≈ F-. From the associated component mass balance and ion exchange (i.e., mass action) equations, an overall speciation model was developed to predict the distribution of all anions between the aqueous and micellar pseudophase for complex ionic mixtures. Experimental results of both artificial and real surface waters were in good agreement to model predictions. Further, the results indicated that micelles combined with ultrafiltration may be a potential technology for nutrient and other pollutant removal from natural or effluent waters.

Soil microbial response to photo-degraded C60 fullerenes.

Recent studies indicate that while unfunctionalized carbon nanomaterials (CNMs) exhibit very low decomposition rates in soils, even minor surface functionalization (e.g., as a result of photochemical weathering) may accelerate microbial decay. We present results from a C60 fullerene-soil incubation study designed to investigate the potential links between photochemical and microbial degradation of photo-irradiated C60. Irradiating aqueous (13)C-labeled C60 with solar-wavelength light resulted in a complex mixture of intermediate products with decreased aromaticity. Although addition of irradiated C60 to soil microcosms had little effect on net soil respiration, excess (13)C in the respired CO2 demonstrates that photo-irradiating C60 enhanced its degradation in soil, with ∼ 0.78% of 60 day photo-irradiated C60 mineralized. Community analysis by DGGE found that soil microbial community structure was altered and depended on the photo-treatment duration. These findings demonstrate how abiotic and biotic transformation processes can couple to influence degradation of CNMs in the natural environment.

The assessment of water use and reuse through reported data: A US case study.

Increasing demands for freshwater make it necessary to find innovative ways to extend the life of our water resources, and to manage them in a sustainable way. Indirect water reuse plays a role in meeting freshwater demands but there is limited documentation of it. There is a need to analyze its current status for water resources planning and conservation, and for understanding how it potentially impacts human health. However, the fact that data are archived in discrete uncoordinated databases by different state and federal entities, limits the capacity to complete holistic analysis of critical resources at large watershed scales. Humans alter the water cycle for food production, manufacturing, energy production, provision of potable water and recreation. Ecosystems services are affected at watershed scales but there are also global scale impacts from greenhouse gas emissions enabled by access to cooling, processing and irrigation water. To better document these issues and to demonstrate the utility of such an analysis, we studied the Wabash River Watershed located in the U.S. Midwest. Data for water extraction, use, discharge, and river flow were collected, curated and reorganized in order to characterize the water use and reuse within the basin. Indirect water reuse was estimated by comparing treated wastewater discharges with stream flows at selected points within the watershed. Results show that during the low flow months of July-October, wastewater discharges into the Wabash River basin contributed 82 to 121% of the stream flow, demonstrating that the level of water use and unplanned reuse is significant. These results suggest that intentional water reuse for consumptive purposes such as landscape or agricultural irrigation could have substantial ecological impacts by diminishing stream flow during vulnerable low flow periods.

Calibration and application of an automated seepage meter for monitoring water flow across the sediment-water interface.

The advective flow of sediment pore water is an important parameter for understanding natural geochemical processes within lake, river, wetland, and marine sediments and also for properly designing permeable remedial sediment caps placed over contaminated sediments. Automated heat pulse seepage meters can be used to measure the vertical component of sediment pore water flow (i.e., vertical Darcy velocity); however, little information on meter calibration as a function of ambient water temperature exists in the literature. As a result, a method with associated equations for calibrating a heat pulse seepage meter as a function of ambient water temperature is fully described in this paper. Results of meter calibration over the temperature range 7.5 to 21.2 °C indicate that errors in accuracy are significant if proper temperature-dependence calibration is not performed. The proposed calibration method allows for temperature corrections to be made automatically in the field at any ambient water temperature. The significance of these corrections is discussed.

A novel method for measuring polymer-water partition coefficients.

Low density polyethylene (LDPE) often is used as the sorbent material in passive sampling devices to estimate the average temporal chemical concentration in water bodies or sediment pore water. To calculate water phase chemical concentrations from LDPE concentrations accurately, it is necessary to know the LDPE-water partition coefficients (KPE-w) of the chemicals of interest. However, even moderately hydrophobic chemicals have large KPE-w values, making direct measurement experimentally difficult. In this study we evaluated a simple three phase system from which KPE-w can be determined easily and accurately. In the method, chemical equilibrium distribution between LDPE and a surfactant micelle pseudo-phase is measured, with the ratio of these concentrations equal to the LDPE-micelle partition coefficient (KPE-mic). By employing sufficient mass of polymer and surfactant (Brij 30), the mass of chemical in the water phase remains negligible, albeit in equilibrium. In parallel, the micelle-water partition coefficient (Kmic-w) is determined experimentally. KPE-w is the product of KPE-mic and Kmic-w. The method was applied to measure values of KPE-w for 17 polycyclic aromatic hydrocarbons, 37 polychlorinated biphenyls, and 9 polybrominated diphenylethers. These values were compared to literature values. Mass fraction-based chemical activity coefficients (γ) were determined in each phase and showed that for each chemical, the micelles and LDPE had nearly identical affinity.

Comparison of export dynamics of nutrients and animal-borne estrogens from a tile-drained Midwestern agroecosystem.

Concentrated animal feeding operations (CAFOs) are known to be a source of nutrients and hormones found in surface water bodies around the world. While the fate and transport of nutrients have been studied for decades, much less research has been conducted on the fate and transport of hormones. To facilitate a comparison of nutrient and hormone export dynamics from farm fields, nitrate + nitrite (N), dissolved reactive phosphorus (DRP), 17α- and 17ß-estradiol (E2), estrone (E1), and estriol (E3) were monitored in a tile drain and receiving ditch for one year on a working farm in north central Indiana. Repeated animal waste applications led to high frequency detection of hormones (>50% in tile drain; >90% in the ditch) and nutrients (>70% for DRP; 100% for N). Hydrologic variability was found to be a dominant factor controlling export of N, DRP, and E1 to the drain and ditch. Of the estrogens, the temporal trend in E1 export was most similar to that of DRP. Differences in temporal export between P and the other estrogens likely were due to differences in the biogeochemical processes that affect their fate and transport within the agroecosystem. During short periods when the flowrate exceeded the 80(th) percentile for the year, over 70% of the total mass export of DRP and E1 occurred for the year in both the tile drain and ditch, demonstrating the importance of high-flow events. Therefore, best management practices must be effective during large flow events to substantially reduce transport to downstream locations.