Kinetics, equilibrium, and mechanisms of sorption and desorption of 17α-ethinyl estradiol in two natural soils and their organic fractions

Sorption and desorption of epiandrosterone and cortisol on sewage sludge: Comparison to aquatic sediment

Steroids have aroused global concern due to their potent endocrine-disrupting effects. Androgens and glucocorticoids are the most abundant species in sewage; however, our understanding of their fate and risks from the source to environmental sinks remains elusive. This study compared the sorption-desorption characteristics of epiandrosterone (EADR) and cortisol (CRL) in sewage sludge and aquatic sediment, and the surface and molecular interactions were tentatively investigated through infrared spectroscopy and the fluorescence excitation-emission matrix. The results showed that the sorption capacities of EADR and CRL in the sludge were 4015 L/kg and 81.17 L/kg, respectively, which are much larger than those in the sediment (EADR: 78.77 L/kg, CRL: 6.39 L/kg); 0.02%-1.2% of EADR and 0.2%-14.5% of CRL could be desorbed from sludge, while the desorption ratios were even lower in the sediment. The high organic content in the sludge might contribute to the larger sorption capacities, while the weak interaction between steroids and organic matter could lead to larger desorption potential. The sediment contained more mineral content and featured a larger specific surface area, which could be responsible for the greater desorption hysteresis for EADR and CRL. These results will help to better understand the potential risk of sewage sludge-associated steroids and their distribution in sediment-water systems.

Comparison of adsorption behaviors of selected endocrine-disrupting compounds in soil

Bisphenol-A (BPA), 17α-ethinylestradiol (EE2), and 4-nonylphenol (4NP) are endocrine-disrupting chemicals (EDCs) that are useful models for studying the potential fate and transport of EDCs in soil and water environments. Two alluvial soils with contrasting physicochemical properties were used as adsorbents for this study. The Zook soil material had more organic matter and clay than the sandy loam Hanlon soil material. Batch equilibrium experiments were performed to generate adsorption isotherms, to determine the adsorption parameters, and to assess desorption hysteresis. Adsorption of BPA to both soils followed an L-type isotherm, and 4NP adsorbed to both Hanlon and Zook soils exhibited S-shape isotherms. EE2 adsorbed to the Zook soil also followed an S-shaped isotherm, but EE2 adsorbed to the Hanlon soil showed an H-type isotherm. Overall, the Sips model fit the data well, with standard errors of prediction generally ≤6%. The adsorption affinity (K_LF ) values were highest for 4NP, and BPA had the lowest hysteresis indices. The data suggest that BPA was most likely adsorbed by soil organic matter via hydrogen bonding involving its two phenolic groups. In contrast, isotherm shape, model affinity indices, lack of desorption, and molecular-scale characteristics led us to infer that 4NP was adsorbed largely by the retention of molecular clusters, perhaps in clay nanopores. Finally, the adsorption of EE2 exhibited different isotherm shapes for the two soils as well as intermediate affinity and desorption indices, suggesting that EE2 molecules could be retained both by soil organic matter and by clay.

Distinct assembly processes shape bacterial communities along unsaturated, groundwater fluctuated, and saturated zones

The subsurface soil environment through the unsaturated (vadose) zone and saturated (below groundwater table) zone is one of the most active layers in the Earth's surface with biogeochemical interactions. Geochemical variables and geographic distance are key driving forces shaping the distribution of soil microbial communities, but our understandings are mainly limited to surface soil or shallow unsaturated zone (1-3 m beneath the ground). In this study, soil and sediment samples were collected from the unsaturated zone, through groundwater fluctuated zone, to saturated zone (up to 20 m) to unravel the assembly processes mediating vertical bacterial community succession across these three zones. Our results suggested both geochemical niches and bacterial diversity had different vertical patterns in each zone. With increased depth, pH increased and nutrient levels (C, N, P, K) and bacterial diversity declined in the unsaturated zone, and nutrients and bacterial diversity remained low levels after reaching the fluctuated and saturated zones. Nutrients were the key drivers shaping bacterial variation in the unsaturated zone, but limited nutrients and only 'depth' significantly explained the variations in the fluctuated zone and saturated zone, respectively. The co-occurrence network supported a more species co-existence pattern in the unsaturated zone than that in the other two zones. Due to the geochemical variations across three zones, the assembly of phylogenetically more clustered communities was observed through deterministic processes (e.g., 55% homogenizing selection) in the unsaturated zone, but the stochastic process (e.g., 50%-70% dispersal limitation) was more important in the fluctuated and saturated zones. These findings together suggested that the vertical distribution of soil bacterial community assembly was zone-specific and shaped by the degree of deterministic vs. stochastic processes. Our results provide a novel insight into the microbial community assembly across three different ecosystems in the Earth's critical zone and shed a light on subsurface biogeochemical processes.

Adsorption-desorption behavior of the endocrine-disrupting chemical quinestrol in soils

Quinestrol (QUN), a synthetic estrogen used as an oral contraceptive or emergency contraceptive component, has been shown to be an endocrine-disrupting chemical. To assess the environmental risk of QUN, batch equilibration experiments were conducted to investigate the adsorption–desorption of QUN in five contrasting soils from different areas of China. The leaching properties were also calculated based on the adsorption and degradation data from our previous study with the same soils. The Freundlich and Langmuir models were applied to the sorption–desorption data to examine the affinity towards QUN of the soils, which had varying physical and chemical properties. The K_f and K_f^des values of QUN in the tested soils ranged from 3.72 to 20.47 mg¹⁻ⁿ Lⁿ kg⁻¹ and from 1.26 to 7.8 mg¹⁻ⁿ Lⁿ kg⁻¹, respectively, and Q_m ranged from 28.25 to 126.58 mg/kg. The desorption data showed that hysteresis occurred. The K_f and K_f^des values of QUN were positively correlated with the soil total organic carbon (OC) and cation exchange capacity (CEC), and it may be due to the content of TOC and CEC exhibited a positive correlation. A low mobility potential of QUN in soils was predicted and verified the adsorption results by the groundwater ubiquity score (GUS) and retardation factor (R_f).

Comparison of 17β-estradiol adsorption on soil organic components and soil remediation agent-biochar

Steroid estrogen residues (SEs) in the soil have attracted growing attention because of their potential for endocrine disruption. Soil organic matter (SOM) and soil remediation agent-biochar, both have important influences on the fate of SEs in the soil environment. This study compared the adsorption of 17β-estradiol (E2) on wheat straw biochar (W-BC) and cow manure biochar (C-BC) with main SOM components including biomacromolecules (cellulose, collagen and lignin) and humic acids (HA). The impact of pyrolysis temperature (350 °C, 550 °C, and 700 °C) on the adsorption capacity of biochar and different concentrations NaClO oxidation on the adsorption capacity of HA were also investigated. The experimental results showed that the adsorption of E2 by biomolecules conformed to the linear isotherm (R² > 0.88), and the adsorption of E2 on biochars and HA were well described by the Langmuir and Freundlich isotherm (R² > 0.94). Meanwhile, the order of the E2 adsorption capacity of sorbents was W-BC > C-BC > HA > lignin > collagen > cellulose. The adsorption capacity of biochar and SOM for E2 increased with the enhancement of aromaticity and hydrophobicity and the reduction of polarity. In addition, the increase of pyrolysis temperature of biochars also promoted the adsorption capacity of E2, while oxidation treatment with NaClO reduced the adsorption capacity of HA to E2. These results deepened the understanding of the adsorption behaviour of E2 on SOM and biochar, and expanded the understanding of the behaviour of SEs in the soil environment.

Effect of Heavy Metal Ions on Steroid Estrogen Removal and Transport in SAT Using DLLME as a Detection Method of Steroid Estrogen

Environmental endocrine-disrupting chemicals have become a global environmental problem, and the distribution, transport, and fate of estrogens in soil and water environments closely relate to human and ecological health as well as to the remediation scheme design. A new micro-extraction technique termed dispersive liquid–liquid micro-extraction (DLLME) combined with high-performance liquid chromatography with fluorescence detector (HPLC-FLD) was developed for the determination of the concentration of steroid estrogens in water samples. The detection limits of HPLC-FLD and DLLME-HPLC/FLD were 0.68–1.73 μg L−1 and 7.16–69.22 ng L−1, respectively. Based on this method, the isothermal adsorption of 17β-E2 on sand and a breakthrough experiment of 17β-E2 and Cu2+ in a soil aquifer treatment (SAT) system were studied. The 17β-E2 adsorption capacity of sand in 17β-E2 solution was detected to be larger than that in a mixed solution of 17β-E2 and Cu(NO3)2 solution, and the breakthrough curves of 17β-E2 and Cu2+ in the mixed solution shifted forward in sand column experiments. Both suggested that the competitive adsorption of 17β-E2 and Cu2+ in the mixed solution might occur on the surface of the sand. In the process of the removal of 17β-E2 in wastewater by SAT, the existence of Cu2+ slightly inhibited the adsorption of 17β-E2 and accelerated the breakthrough of 17β-E2. These results ought to be a warning for SAT application for 17β-E2 removal in water where heavy metals coexist.

Effect of corn straw biochar application to sediments on the adsorption of 17α-ethinyl estradiol and perfluorooctane sulfonate at sediment-water interface

The immobilization of organic contaminants in sediment-water systems is of growing concern. Using biochar as sorbent amendment to reduce the mobility of pollutants in the sediment-water interface is becoming increasingly popular as a low-cost and environmentally friendly option. In this study, we mixed sediment from the Weishan Lake with biochar (0%, 2%, and 5% (w/w)) derived from corn straw to investigate the adsorption of perfluorooctane sulfonate (PFOS) and 17α-ethinyl estradiol (EE2). Biochar addition significantly improved the adsorption rates and capacities of EE2 and PFOS on sediments by the factors 1.7-3.5; the organic carbon concentration in the sediment was the main factor influencing this process. The sorption of EE2 and PFOS to sediment was near-linear (Freundlich exponent 1/n of 0.799-0.805), but non-linear for biochar (0.430-0.476) and sediment+biochar (0.370-0.421). The mobility of PFOS in the water-sediment system after biochar addition was significantly reduced, with a considerable increase (about three times) in the sediment-water distribution coefficient K_d. Compared to EE2, PFOS is anionic compound and contains hydrophobic C-F chains and hydrophilic S-O groups, making it more susceptible pH influences and resulting in interactions with-OH, -C=O, Si-O-Si, -O-Si, and -Al-O-Al groups via hydrogen bonding, ligand exchange, and surface complexation. We suggest that biochar amendment at ～5% is a viable approach to immobilize EE2 and PFOS at the sediment-water interface.

Adsorption characteristics of organics in the effluent of ultra-short SRT wastewater treatment by single-walled, multi-walled, and graphitized multi-walled carbon nanotubes

With a conceptual shift in sewage treatment from ‘waste pollution’ to ‘vehicle of resource and energy recovery’ and the further intensification of the energy crisis, the separation and recovery of carbon resources from discharged sewage has gained increasing recent attention in the field of water treatment. The ultra-short Solids Retention Time (SRT) activated sludge process (SRT ≤ 4 d) is highly efficient for separating organic matter and improving the energy recovery rate in wastewater treatment plants, but the effluent quality is relatively poor. If organics in the ultra-short SRT effluent can be reduced further to separate and recover carbon resources, the process may soon replace the traditional activated sludge process. We conducted physical adsorption carbon recovery experiments in an ultra-short SRT (SRT = 2 d) activated sludge system using three carbon nanotubes. Considering that Chemical Oxygen Demand (COD) arises from a mixture of organic compounds, and because humic acid (HA) makes up a large fraction of the effluent and can cause great environmental harm, further experiments were conducted on the adsorption of HA in the effluent COD to three nanotubes. This study proposes a novel method to completely remove organics from the effluent from ultra-short SRT activated sludge processes and reveals nanotube adsorption properties and mechanisms.

Design of an enhanced SAT using the graphene-MAR mixture for the removal of 17β-E2 at a demonstration site of Qianjin farm in China

An adsorption-enhanced soil aquifer treatment (SAT) system was designed to reduce the level of estrogens below the threshold stipulated by the standards. The 17β-E2 adsorption by graphene and MARs (H103) was investigated and an optimum amount of graphene and MARs in the mixture was determined using the linear programming. The kinetics and isotherm characteristics of both adsorbents were well described by the Lagergren pseudo-second order and the Freundlich model, respectively. The 17β-E2 adsorption on graphene and H103 was 88% and 70.37%, and the high temperature was beneficial to the 17β-E2 adsorption on graphene while the thermodynamic behaviors of H103 were in direct contrast to that of graphene. The study found that the maximum economic benefits could be achieved when the mass of graphene and H103 in the mixture is 2.79 g and 13.20 kg, respectively.

Vertical distribution of archaeal communities associated with anaerobic degradation of pentabromodiphenyl ether (BDE-99) in river-based groundwater recharge with reclaimed water

When groundwater is recharged with reclaimed water, the presence of trace amounts of biorefractory pentabromodiphenyl ether (PBDE, specifically BDE-99) might cause potential groundwater pollution. A laboratory-scale column was designed to investigate the distribution of the community of archaea in this scenario and the associated anaerobic degradation of BDE-99. The concentration of BDE-99 decreased significantly as soil depth increased, and fluorescence in situ hybridization (FISH) analysis suggested that archaea exerted significant effects on the biodegradation of PBDE. Through 454 pyrosequencing of 16s rRNA genes, we found that the distribution and structure of the archaeal community associated with anaerobic degradation of BDE-99 in the river-based aquifer media changed significantly between different soil depths. The primary debrominated metabolites varied with changes in the vertically distributed archaeal community. The archaea in the surface layer were dominated by Methanomethylovorans, and the middle layer was mainly composed of Nitrososphaera. Nitrosopumilus and Nitrososphaera were equally abundant in the bottom layer. In addition, Methanomethylovorans abundance depended on the depth of soil, and the relative abundance of Nitrosopumilus increased with increasing depth, which was associated with the oxidation-reduction potential and the content of intermediate metabolites. We propose that Nitrososphaera and Nitrosopumilus might be the key archaeal taxa mediating the biodegradation of BDE-99.

Adsorption of 17 α-ethyl estradiol with the competition of bisphenol A on the marine sediment of Hong Kong

The present experimental study was to characterize the adsorption behavior of 17 α-ethyl estradiol (EE2) onto marine sediment in both the single and binary solute systems. Stepwise spiking was innovatively performed to better understand the competition effects. Adsorption of EE2 on the marine sediment can be well fitted by the Freundlich model with an affinity coefficient (K_F) varying from 15.8 to 39.8L/kg. It was significantly influenced by SOM and the particle properties. Co-presence of BPA brought about a significant competition effect on the adsorption of EE2, leading to a reduced EE2 adsorption. The competitive effect imposed by EE2 to BPA, however, was even more serious owing probably to the large molecular structure and high hydrophobicity of EE2. The sediment sample with the highest SOM and SSA presented a mild competition effect, while the sediment with the lowest SOM and largest particle size exhibited the most serious competition effect.

Quicklime-induced changes of soil properties: Implications for enhanced remediation of volatile chlorinated hydrocarbon contaminated soils via mechanical soil aeration

Mechanical soil aeration is used for soil remediation at sites contaminated by volatile organic compounds. However, the effectiveness of the method is limited by low soil temperature, high soil moisture, and high soil viscosity. Combined with mechanical soil aeration, quicklime has a practical application value related to reinforcement remediation and to its action in the remediation of soil contaminated with volatile organic compounds. In this study, the target pollutant was trichloroethylene, which is a volatile chlorinated hydrocarbon pollutant commonly found in contaminated soils. A restoration experiment was carried out, using a set of mechanical soil-aeration simulation tests, by adding quicklime (mass ratios of 3, 10, and 20%) to the contaminated soil. The results clearly indicate that quicklime changed the physical properties of the soil, which affected the environmental behaviour of trichloroethylene in the soil. The addition of CaO increased soil temperature and reduced soil moisture to improve the mass transfer of trichloroethylene. In addition, it improved the macroporous cumulative pore volume and average pore size, which increased soil permeability. As soil pH increased, the clay mineral content in the soils decreased, the cation exchange capacity and the redox potential decreased, and the removal of trichloroethylene from the soil was enhanced to a certain extent. After the addition of quicklime, the functional group COO of soil organic matter could interact with calcium ions, which increased soil polarity and promoted the removal of trichloroethylene.

Sorption of tylosin and sulfamethazine on solid humic acid

Tylosin (TYL) and sulfamethazine (SMT) are ionizable and polar antimicrobial compounds, which have seeped into the environment in substantial amounts via fertilizing land with manure or sewage. Sorption of TYL and SMT onto humic acid (HA) may affect their environmental fate. In this study, the sorption of TYL and SMT on HA at different conditions (pH, ionic strength) was investigated. All sorption isotherms fitted well to the Henry and Freundlich models and they were highly nonlinear with values of n between 0.5 and 0.8, which suggested that the HA had high heterogeneity. The sorption of TYL and SMT on HA decreased with increasing pH (2.0-7.5), implying that the primary sorption mechanism could be due to cation exchange interactions between TYL(+)/SMT(+) species and the functional groups of HA. Increasing ionic strength resulted in a considerable reduction in the Kd values of TYL and SMT, hinting that interactions between H bonds and π-π EDA might be an important factor in the sorption of TYL and SMT on HA. Results of Fourier transform infrared (FT-IR) and (13)C-nuclear magnetic resonance (NMR) analysis further demonstrated that carboxyl groups and O-alkyl structures in the HA could interact with TYL and SMT via ionic interactions and H bonds, respectively. Overall, this work gives new insights into the mechanisms of sorption of TYL and SMT on HA and hence aids us in assessing the environmental risk of TYL and SMT under diverse conditions.

Sorption of testosterone on partially-dispersed soil particles of different size fractions: Methodology and implications

Sorption of hormones to soil particles of different size fractions (DSFs) has been studied to understand their fate and transport (F/T) in soils. Conventional studies fractionated the soil particles into DSFs by using the high speed stirring method and/or adding surfactants to fully disperse the bulk soil. However, the natural processes (e.g., soil erosion, irrigation) often are relatively mild, and many soil particles may be still in the aggregate form. In this study, a method was developed for conducting the sorption test of a representative hormone (i.e., testosterone) to bulk soils first and then analyzing the results against DSFs. Results indicated the particle size distribution (PSD) of the two representative soils tested with partially-dispersed and fully-dispersed methods was significantly different due to the attachment of clay particles on sand and silt. Testosterone was sorbed mainly by the dominant aggregates even though they might have relatively lower sorption affinity than that of clays. However, the small particles (<2000 nm), even with ∼5% mass of the bulk soil, contributed more than 30% of sorbed testosterone in the "whole" soils. The partially-dispersed soil particles of DSFs should be used to understand the transport of hormone in runoff, because using the fully-dispersed soil particles will overestimate while the whole soil method will underestimate the transport potential. With the methodology developed in this study, the sorption tests will not compromise soil's original properties (e.g., aggregates) or the competition (e.g., sorption) among soil particles, and the contribution of DSFs (particularly the partially-dispersed aggregates) to the sorption of the "whole" soil can be determined.

Sorption behavior of tylosin and sulfamethazine on humic acid: kinetic and thermodynamic studies

Sorption and transport of TYL and SMT in soils is complicated and the transportation abilities of TYL and SMT might be weak for the soils rich in organic matter.

Preparation and application of amorphous Fe–Ti bimetal oxides for arsenic removal

A series of Fe–Ti bimetal oxides for As(iii) and As(v) removal were synthesized through a co-precipitation method.

Testosterone sorption and desorption: effects of soil particle size

Soils contain a wide range of particles of different diameters with different mobility during rainfall events. Effects of soil particles on sorption and desorption behaviors of steroid hormones have not been investigated. In this study, wet sieve washing and repeated sedimentation methods were used to fractionate the soils into five ranges. The sorption and desorption properties and related mechanisms of testosterone in batch reactors filled with fractionated soil particles were evaluated. Results of sorption and desorption kinetics indicate that small soil particles have higher sorption and lower desorption rates than that of big ones. Thermodynamic results show the sorption processes are spontaneous and exothermal. The sorption capacity ranks as clay>silt>sand, depending mainly on specific surface area and surface functional groups. The urea control test shows that hydrogen bonding contributes to testosterone sorption onto clay and silt but not on sand. Desorption tests indicate sorption is 36-65% irreversible from clay to sand. Clays have highest desorption hysteresis among these five soil fractions, indicating small particles like clays have less potential for desorption. The results provide indirect evidence on the colloid (clay)-facilitated transport of hormones (micro-pollutants) in soil environments.

Adsorption behaviors of 17α-ethinylestradiol in sediment-water system in northern Taihu Lake, China

Adsorption behavior of 17α-ethinylestradiol (EE2) in northern Taihu Lake sediment was analyzed by using batch equilibrium experiment. Freundlich isotherm could describe the adsorption thermodynamic behavior of EE2 in sediment. Sediment organic matter (SOM) contents had important impacts on the adsorption capacity for EE2. The pH values also influenced the adsorption capacity for EE2. Increase of pH value could decrease the EE2 adsorption, which might be due to the electrostatic repulsion between the anionic form of EE2 and sediments with negative charge under high pH values. Competitive effects of bisphenol A (BPA) on EE2 adsorption were further analyzed. The results showed that low concentration BPA did not have significant influences on EE2 adsorption. However, high concentration BPA could reduce EE2 adsorption, which might be due to the similar molecular diameter of BPA with adsorption sites and one more benzene ring with a hydroxyl group in BPA. These results provide primary information of EE2 adsorption in sediment-water system in Taihu Lake, which is useful for the environmental risk assessment and management of EE2 in studied area.