Adsorption Capacity Of Sediments Research Articles

Characteristics of Phosphate Sorption on Surface Sediments: A Study in Kendari Bay

Phosphate adsorption and desorption are significant processes that influence the presence of phosphate in aquatic ecosystems and regulate the concentration of phosphate at the water-sediment interface. This research aims to investigate the characteristics of phosphate adsorption and desorption in Kendari Bay sediments, study the relationship between adsorption capacity and sediment characteristics and its phosphorus fraction, and evaluate its potential contribution to the overlying water column. Physicochemical measurements of the water and sediments were performed in the sampling location and the laboratory. Two types of adsorption-desorption kinetics models and two types of isothermal adsorption models were used to estimate the adsorption rate and capacity of the surface sediments. Adsorption kinetics and desorption kinetics experiments produced pseudo-second-order kinetic model equations with regression coefficients (R2) of 0.865–0.936 and 0.886–0.947, respectively. The isothermal adsorption experiment follows the Langmuir equation model with R2 = 0.964. The maximum adsorption capacity (Qmax) value was 156.3–227.3 mg/kg, and the phosphate concentration value at zero equilibrium (EPC0) was 0.0026–0.0047 mgP/L. Notably, the EPC0 value was higher than the SRP concentration, indicating that the resuspension of phosphate ions from sediment into the water column could occur. Furthermore, there was a correlation between Qmax values with OP, Al-P, Fe-P, clay particles, and organic materials. Potential practical applications may include integrating sediment adsorption capacity data into ecosystem models to inform nutrient management strategies and promote sustainable coastal development in Kendari Bay and beyond.

Effects of tire-road wear particles on the adsorption of tetracycline by aquatic sediments.

Tire-road wear particles (TRWPs) are formed by friction between the tire and the road. TRWPs are ubiquitous across the globe, especially in sediments. However, the possible effects of TRWPs on tetracycline (TC) in aquatic sediments are unknown. To investigate the potential role of TRWPs as carriers of co-pollutants, this study investigated the pore surface properties and TC adsorption behavior of TRWP-contaminated sediments and explored the TC behavior in water sediments, as well as the role of aging processes and TRWPs abundance. The results showed that the surface morphology of TRWP-contaminated sediments changed and the adsorption capacity of sediments to TC increased. The TC adsorption capacity of sediments contaminated by 2% TRWPs increased from 3.15 to 3.48mg/g. Moreover, the surface physical and chemical properties of TRWPs after UV aging changed, which further increased the TC adsorption capacity. The TC adsorption capacity of the sediments contaminated by aged TRWPs increased from 3.48 to 3.65mg/g. Changing the proportion of aged TRWPs, we found that the adsorption capacity of sediments contaminated by different proportions of TRWPs for TC was 2% > 1% > 0.5% > 4% > blank sediment. These results may contribute to predicting the potential environmental risks of TRWPs in aquatic sediments.

The influence of turbulence on sediment phosphorus sorption

The effect of mean flow velocity on phosphorus (P) partitioning between water and sediment has received much attention in recent decades. However, the impact of turbulence on the efficiency and capability of sediment adsorbing and desorbing dissolved inorganic phosphorus (DIP) is still unclear. A series of contrasting experiments on the sediment sorption and desorption of DIP with the flow turbulence kinetic energy (TKE) ranging from 1.95 to 2.93 pa have been conducted. It was found that the adsorbed P onto unit mass of sediment increases with the increase in TKE. It is because an increase in TKE results in a rise in the effective adsorption capacity of sediment (bm) by 20–30% during the adsorption process. The bm shows the maximum rise from 0.18 to 0.25 mg/g when TKE increases from 1.95 to 2.93 pa with a fixed sediment concentration of 0.5 g/L. To account for the direct effect of TKE on P adsorption, the Langmuir model is modified by introducing a newly defined coefficient (fA−TKE). The fA−TKE shows a good linear relationship with TKE. Comparison between the modified model and the classic model shows that the amount of adsorbed P could be overestimated by over 50% if the direct effect of turbulence intensity is ignored. The experimental data show that the increase in TKE also enhances the desorption process, with the degree of P desorption (Ddes) increased by 44%. The relation between Ddes and TKE can be well represented using a logarithmic function to quantify the direct effect of turbulence intensity on desorption of P.

Sorption Behavior and Prediction of Tetracycline on Sediments from the Yangtze Estuary and Its Coastal Areas

Sediments represent the major sink of antibiotics in aquatic systems. However, few studies have proposed effective models that can predict the adsorption capacity of sediments through their physicochemical parameters. Here, 49 sediment samples were collected from different locations in the Yangtze Estuary and its adjacent coastal areas. The sediments were characterized, and their adsorption behavior towards tetracycline (TC) was investigated. It was found that both the Langmuir and Freundlich models fit the TC adsorption data well, and the sediments in the mud area showed the highest adsorption capacity. Subsequently, through correlation analysis for the adsorption coefficients and physicochemical parameters of sediments, 11 models were established to predict the adsorption coefficients (Kd), in which clay and cation exchange capacity played significant roles. When the salinity was increased from 0 to 32.79‰, the Freundlich adsorption coefficient (Kf) of TC for most sediments was reduced by more than75% (except sediment C6). Therefore, the methods provided herein can be helpful in predicting the sorption behavior of antibiotics with similar structures toward TC by sediments in this region.

Assessing exchangeable phosphate and related data in coastal sediments: Theoretical and practical considerations

This article deals with the adsorption-desorption processes of phosphate on sediments according to the Langmuir theory. The theoretical developments are described and applied to the experiments which enable the determination of phosphate that is exchangeable with surrounding water (exch-P). Langmuir equation parameters such as the partition coefficient and the maximum adsorption capacity for exchange of phosphate between solid and water are assessed and discussed. The dataset consisted of contrasting sediments gathered over fifteen years from a large number of coastal and estuarine areas.The determination of exch-P was carried out with linear and asymptotic computations. The values, ranging from a few tenths of μmol g−1 in sandy sediments up to approximately 9 μmol g−1 in muddy sediments, are slightly more precise by using the linear computation. Partition coefficients (Kp: 0.03–3.8 L g−1), increasing with the proportion of fine particles, are likely related to the Fe content. It is proposed to use Kp as a criterion for the examination of the potential exchange of phosphate with the surrounding water.The maximum phosphate adsorption capacity of sediments (Qo) derived from the Langmuir equations exhibits large confidence interval. So, it is not found significantly higher than the exchangeable phosphate, as expected from published sediment saturation experiments.

Adsorption and desorption behavior of arsenite and arsenate at river sediment-water interface.

The adsorption of inorganic arsenic (As) plays an important role in the mobility and transport of As in the river environment. In this work, the adsorption and desorption of arsenite [As(III)] and arsenate [As(V)] on river sediment were conducted under different pH, initial As concentrations, river water and sediment composition to assess As adsorption behavior and mechanism. Both adsorption kinetics and equilibrium results showed higher adsorption capacity of sediment for As(V) than As(III). Adsorption of As(III) and As(V) on river sediment was favored in acidic to neutral conditions and on finer sediment particles, while sediment organic matter marginally reduced adsorption capacity. In addition, higher adsorption affinity of As(III) and As(V) in river sediment was observed in deionised water than in river water. For the release process, the desorption of both As(III) and As(V) followed nonlinear kinetic models well, showing higher amount of As(III) release from sediment than As(V). Adsorption isotherm was well described by both Langmuir and Freundlich models, demonstrating higher maximum adsorption capacity of As(V) at 298.7mg/kg than As(III) at 263.3mg/kg in deionised water, and higher maximum adsorption capacity of As(III) of 234.3mg/kg than As(V) of 206.2mg/kg in river water. The XRD showed the changes in the peaks of mineral groups of sediment whilst FTIR results revealed the changes related to surface functional groups before and after adsorption, indicating that Fe-O/Fe-OH, Si(Al)-O, hydroxyl and carboxyl functional groups were predominantly involved in As(III) and As(V) adsorption on sediment surface. XPS analysis evidenced the transformation between these As species in river sediment after adsorption, whilst SEM-EDS revealed higher amount of As(V) in river sediment than As(III) due to the lower signal of Al.

Adsorption behavior of enrofloxacin in soil and sediment and its response mechanism to environmental factors

ABSTRACT As an important part of lake and reservoir ecosystem, sediment is an important “source” and “sink” of pollutants. Antibiotics, as a kind of important emerging organic pollutants, have attracted global attention. In order to understand the adsorption behavior and mechanism of antibiotics in sediment, enrofloxacin (ENR) was used as the target pollutant to evaluate its adsorption behavior in sediment and soil and the response mechanism of environmental factors by using the intermittent equilibrium method. The results showed that the adsorption equilibrium time of ENR in sediment and soil was 6 h, and the adsorption kinetics was in line with the quasi-second-order kinetics. The two-compartment model Herry-Langmuir can better describe the adsorption of ENR by sediment and soil. There is a lag phenomenon in desorption process.The average lag coefficient HI of sediment and soil was 1.08 × 10−3 and 0.43 × 10−3, respectively, indicating that ENR was difficult to be released. When pH = 5, the adsorption capacity is the highest, indicating that the adsorption mechanism of ENR in the sample is mainly cation exchange; the higher the cationic valence state of the background liquid is, the stronger the competitive adsorption capacity is, which leads to the gradual decrease of ENR adsorption capacity in the sample. Because ENR contains -F group, resulting in complex reaction with Al3+ in the solution, thus reducing the activity of Al3+, reducing the competitive adsorption of Al3+ and ENR, then ENR adsorption capacity increased. The change of ENR adsorption capacity of sediment and soil is Q(Al3+)>Q(Na+)>Q(K+)>Q(Ca2+)>Q(Mg2+)>Q(Fe3+). The adsorption capacity of ENR on sediment was higher than that on soil under all conditions.

Sediment Microstructure in Gas Hydrate Reservoirs and its Association With Gas Hydrate Accumulation: A Case Study From the Northern South China Sea

Exploration and pilot production have confirmed that gas hydrates in the Shenhu area on the northern continental slope of the South China Sea have enormous resource potential. However, a meticulous depiction of gas hydrate reservoirs based on sediments is limited. The distributed low-flux gas hydrates are mainly deposited in the Shenhu area, and the gas hydrate saturation exhibits extreme vertical heterogeneity. In this study, we focused on the sediment microstructure of gas hydrate reservoirs. Based on the variation in gas hydrate saturation, the study interval was divided into non-gas hydrate (non-GH) as well as I-, II-, and III-gas hydrate reservoir layers. We analyzed the relationship between sediment microstructure and gas hydrate reservoirs based on computed tomography scans, specific surface area analysis, and scanning electron microscopy observations. The results showed that the sediment in gas hydrate reservoirs had three types of pores: 1) intergranular pores between coarse grains (CG-intergranular pores), 2) intergranular pores between fine grains (FG-intergranular pores), and 3) biologic grain pores (BG-pores). The CG- and FG-intergranular pores were mainly formed by the framework, which consisted of coarse minerals (such as quartz and feldspar) and clay minerals, respectively. The BG-pores were mainly formed by the coelomes of foraminifera. CG-intergranular pores and BG-pores can provide effective reservoir space and increase the permeability of sediment, which is conducive to gas hydrate accumulation. The FG-intergranular pores reduce permeability and are not conducive to gas hydrate accumulation. Clay minerals and calcareous ultramicrofossils with small grain sizes and complex microstructures fill the effective reservoir space and reduce the permeability of sediment; additionally, they improve the adsorption capacity of sediment to free gas or pore water, which is not conducive to gas hydrate formation and accumulation. The results of our study explicitly suggest that the microstructure of sediment is an important controlling factor for gas hydrate accumulation and reveals its underlying mechanism.

Effects of environmental factors on phosphorus adsorption capacity and release risk in lake sediments

Sediment is an important part of the lake and reservoir ecosystem, and also an important "source" and "sink" of pollutants. In this paper, sediment A (Xinlicheng Reservoir Sediments), sediment B (eutrophic lake reservoir sediments) and soil C (topsoil at the inflow of Yitong River near Xinlicheng Reservoir) are used as research objects, and batch experiments are used to study the adsorption capacity and release risk of phosphorus (P). The results showed that the maximum adsorption capacity of the adsorbent for phosphorus accounted for 91.51–99.63% of the total adsorption capacity within 0–120 min; when the background liquid phosphorus concentration is lower, soil and sediment all have different degrees of phosphorus release. By this time soil and sediment is the "source" of pollutants; when the phosphorus concentration is 10 mg/L, the maximum adsorption capacity is 116.19–428.91 mg/kg, and the adsorption capacity of sediment A is 2.41 times and that of soil C and sediment B, respectively. 3.69 times, indicating that if phosphorus enters the water body from the soil due to surface runoff and other factors, the sediment has a strong adsorption capacity for phosphorus, that is, soil and sediment is an effective "sink" of phosphorus; the Henry equation is used to fit the P adsorption isotherm effect. Preferably, and r is greater than 0.968. The amount of phosphorus absorbed by sediment A and sediment B is affected by pH higher than that of soil C. When the value of pH is 7, the adsorption amount is the largest; the P induced lake eutrophication risk index (ERI) of sediment A, sediment B and soil C is sediment B > soil C > sediment A. As the temperature of sediment and soil rises, the ERI index of phosphorus gradually decreases.

Effects of virgin microplastics on the transport of Cd (II) in Xiangjiang River sediment

River sediments are considered as sinks of microplastics (MPs). Although numerous studies have been conducted on MPs pollution in river sediments, the impact of MPs on the environmental behavior of Cd (II) in river sediments is still unknown. In this work, the effects of six MPs (polyethylene, polypropylene, polystyrene, polyvinyl chloride, polymethyl methacrylate and polylactic acid) on the adsorption of Cd (II) by Xiangjiang River sediment and the transport of Cd (II) in sediment were studied. The results showed that the adsorption ability of sediment to Cd (II) decreased with the increase of the content of MPs in sediment. When the content of MPs in sediment increased to 10%, polypropylene had the greatest effect on the adsorption affinity of sediments to Cd (II). Moreover, the addition of MPs accelerated transport of Cd (II) in sediment, and the transport of Cd (II) in sediment increased with the increase of the content of MPs. The reason may be that after adding MPs, the adsorption capacity of sediment to Cd (II) decreases, and the mass transfer resistance of Cd (II) to sediment reduces, which leads to faster transport of Cd (II) in sediment. Especially, when the content of MPs in sediment increased to 10% (w/w), the saturation point of the breakthrough curve decreased by about 70 pore volumes. This work hopes to provide helpful views on the environmental behavior and risk assessment of Cd (II) in the presence of MPs.

Heavy metals on sediments of a Mexican tropical lake: chemical speciation, metal uptake capacity, and chemical states

Mobility and speciation of heavy metals in sediments of Mexican Lake Chapala were assessed through a five-step sequential extraction technique. Metal adsorption capacity of sediments was investigated from each sequential extraction through measurements of their specific surface areas using nitrogen adsorption data. X-ray photoelectron spectroscopy (XPS) was applied to every geochemical fraction to study the chemical metal species present on the surface of sediments. A low risk of detachment to water column was found for all metals, except Zn, Mn, and Fe, although these metals are not considered of high risk to biota. Despite this, the results of this study indicated that there has not been an adequate control from corresponding authorities regarding discharges containing heavy metals. The results of nitrogen adsorption measurements allowed deducing that sediments are mesoporous solids formed mainly by parallel lamellae (clays) composed of aluminosilicates. A clear relationship was observed between specific surface area and the amount of metals obtained by atomic absorption measurements. XPS results indicated that the main chemical states of metals observed were: silicon dioxide (SiO2), aluminum trioxide (Al2O3), iron/silicon oxide (Fe/SiO2), iron (III) oxyhydroxide [Fe(OH)O], aluminosilicate oxide [Al2SiO5], sodium acetate [NaC2H3O2], iron/aluminum oxide [Fe/Al2O3], aluminum hydroxide [Al(OH)3], and iron oxide [Fe2O3].

Dissolved humic substances supplied as potential enhancers of Cu, Cd, and Pb adsorption by two different mangrove sediments

The external supply of humic substances has been recently suggested for the remediation of metal-polluted sediments; however, little is known about how to supply them and their effects on metal mobility. The study sought to investigate the sediment—metals—humic substance interaction in mangrove forest sediments. We aimed to evaluate the sediment adsorption potential in the case of large and rapid metal loads, as recently occurred in the Doce River (Brazil). In each mangrove forest sampling point of the Benevente River (RB) and Vitoria bay (MO), sediments were collected randomly along the river banks at a depth of 0–10 cm. Samples were characterized in terms of pH, CEC, organic carbon, texture, specific surface area, and elemental composition. The heavy metal content was measured by mass absorption spectrophotometry. Humic substances were extracted from the sediments according to the International Humic Substances Society (IHSS) method, avoiding separation of fulvic and humic acids. Original sediments were supplemented with humic substances and six Cu, Cd, or Pb concentrations. Freundlich and Langmuir equations were employed to create adsorption isotherms. The two sediments are significantly different, specifically with regard to organic carbon and Fe content, texture, and specific surface area. External humic substances increased the Cu adsorption capacity in both sediments but without an important change in Cu adsorption dynamics. Humic substances slightly increased the sediment adsorption capacity of Pb in RB sediment while they decreased in MO sediment, characterized by lower specific surface area, probably due to coverage of the active adsorption sites. Cd isotherms showed that the different characteristics of sediments alone do not affect Cd adsorption, but coupled with humic substances; Cd affinity for the soil surface increased five times in RB sediments confirming sediment-metal-humic substance interactions. Humic substances affect soil metal retention mainly by altering the ion affinity for sediment surface, leading to contrasting results. The Fe concentration could be important depending on specific surface area and humic substance percentage, due to its capacity to form spheroids linked to molecules of humic substances on the clay surface. Several works have been carried out on this research area, but due to the many variables and different metal ions, we recommend further studies.

Differences in major ions as well as hydrogen and oxygen isotopes of sediment pore water and lake water

Isotopic and chemical compositions of pore water (PW) are highly relevant to environmental and forensic study. Five lake water (LW) samples and five sediment samples were collected to investigate the effects of pore sizes of sediments on PW chemistry and stable isotopes and determine mechanisms controlling their variations. Six pore water fractions were extracted from different-sized pores in each sediment sample at six sequential centrifugal speeds for chemical and isotopic analysis. The sediments consisted mainly of quartz, feldspar, and clay minerals. The hydrogen and oxygen isotopic compositions of PW are mainly controlled by the overlying LW, although the lag effect of exchange between overlying LW and PW results in isotopic differences when recharge of LW is quicker than isotopic exchange in PW. Identical isotopic compositions of PW from sediments with different pore sizes indicate that isotopic exchange of water molecules with different pore sizes is a quick process. The ratio of average total dissolved solid (TDS) concentration of PW to TDS concentration of LW shows a strong relationship with adsorption capacity of sediments, demonstrating that remobilization of ions bound to sediments mainly causes a chemical shift from LW to PW. Concentrations of Ca2+, Mg2+, and Cl– in PW remain unchanged, while concentrations of Na+, K+, and SO42− slightly increase with decreasing pore size. Chemical differences of PW from sediments with different pore sizes are governed by ion adsorption properties and surface characteristics of different-sized particles.

Reduced phosphorus retention by anoxic bottom sediments after the remediation of an industrial acidified lake area: Indications from P, Al, and Fe sediment fractions

Formerly acidified lakes and watersheds can become more productive when recovering from acidity, especially when exposed to anthropogenic disturbance and increased nutrient loading. Occasional toxic cyanobacterial blooms and other signs of eutrophication have been observed for a decade in lakes located in the Sudbury, Ontario, mining area that was severely affected by acid deposition before the start of smelter emission reductions in the 1970s. Oligotrophic Long Lake and its upstream lakes have been exposed to waste water input and development impacts from the City of Greater Sudbury and likely have a legacy of nutrient enrichment in their sediment. Based on observations from other published studies, we hypothesized that P, which was previously adsorbed by metals liberated during acidification caused by the mining activities, is now being released from the sediment as internal P loading contributing to increased cyanobacteria biomass. Support for this hypothesis includes (1) lake observations of oxygen depletion and hypolimnetic anoxia and slightly elevated hypolimnetic total P concentration and (2) P, Al, and Fe fractionation of two sediment layers (0–5, 5–10 cm), showing elevated concentrations of TP and iron releasable P (BD-fraction), decreased concentrations in fractions associated with Al, and fraction ratios indicating decreased sediment adsorption capacity. The comparison with two moderately enriched lakes within 200 km distance, but never directly affected by mining operations, supports the increasing similarity of Long Lake surficial sediment adsorption capacity with that of unaffected lakes. There is cause for concern that increased eutrophication including the proliferation of cyanobacteria of formerly acidic lakes is wide-spread and occurs wherever recovery coincides with anthropogenic disturbances and physical changes related to climate change.

Rare earth element geochemistry characteristics of seawater and porewater from deep sea in western Pacific

Deep-sea sediments contain high concentrations of rare earth element (REE) which have been regarded as a huge potential resource. Understanding the marine REE cycle is important to reveal the mechanism of REE enrichment. In order to determine the geochemistry characteristics and migration processes of REE, seawater, porewater and sediment samples were systematically collected from the western Pacific for REE analysis. The results show a relatively flat REE pattern and the HREE (Heavy REE) enrichment in surface and deep seawater respectively. The HREE enrichment distribution patterns, low concentrations of Mn and Fe and negative Ce anomaly occur in the porewater, and high Mn/Al ratios and low U concentrations were observed in sediment, indicating oxic condition. LREE (Light REE) and MREE (Middle REE) enrichment in upper layer and depletion of MREE in deeper layer were shown in porewater profile. This study suggests that porewater flux in the western Pacific basin is a minor source of REEs to seawater, and abundant REEs are enriched in sediments, which is mainly caused by the extensive oxic condition, low sedimentation rate and strong adsorption capacity of sediments. Hence, the removal of REEs of porewater may result in widespread REE-rich sediments in the western Pacific basin.

Adsorption behaviors of glyphosate, glufosinate, aminomethylphosphonic acid, and 2-aminoethylphosphonic acid on three typical Baltic Sea sediments

Abstract A batch experiment was conducted to study the adsorption behaviors of glyphosate , glufosinate , aminomethylphosphonic acid (AMPA), and 2-aminoethylphosphonic acid (2-AEP) in marine sediments (mud, silt, and sand) from the Baltic Sea. The experiment took into account the influence of pH, salinity, and temperature on the adsorption behaviors of the studied compounds. In contrast to glufosinate, glyphosate exhibited an adsorption affinity for the three types of sediments. AMPA and 2-AEP showed similar adsorption behaviors on mud and silt, while their adsorption on sand was negligible. The equilibrium adsorption data for glyphosate, AMPA, and 2-AEP on mud and silt fit well with the linear partitioning and Freundlich isotherms, whereas the data for glyphosate on sand could only be fitted with the Freundlich isotherm. The Freundlich distribution coefficients (k f) were in the range of 6.1–259.5 L/kg for glyphosate, 9.2–39.5 L/kg for AMPA, and 7.7–38.5 L/kg for 2-AEP under the experimental conditions of pH 8.1, temperature = 21 °C, and a salt concentration of 8 g/L. The adsorption kinetic was better described by the pseudo-second-order than the pseudo-first-order model, suggesting chemisorption as the adsorption mechanism. The order of adsorption of the compounds on the sediments was: glyphosate > AMPA ≥ 2-AEP > glufosinate. The adsorption capacity of sediments followed the sequence: mud > silt > sand. Increasing the pH, salinity, or temperature of the solution significantly reduced the adsorption capacity of the compounds. The data obtained in this study provide valuable information on the fate and distribution of the investigated phosphonates in the Baltic Sea.

Quantitative prediction and typical factor effects of phosphorus adsorption on the surface sediments from the intertidal zones of the Yellow River Delta, China

Using 13 sediment physicochemical properties and a partial least squares (PLS) regression method, a predictive model was developed for the phosphorus (P)-adsorption capacity of sediments in the intertidal zones of the Yellow River Delta. The cross-validated regression coefficient (Q2cum=0.823) and correlation coefficient (R2=0.854) indicated significantly high robustness of the model. Moreover, P adsorption characteristics of sediments in the intertidal zones were systematically studied. The maximum adsorption rate (274.80mgkg–1h–1) was seen for sediment of the site around which there was aquaculture, which could have led to a higher organic matter content in the sediment. The mass fraction of clay and silt (<62.5µm) in the sediment of this site was 74%. The P-adsorption capacities ranged from 86.63 to 297.49mgkg–1 for all sites. The quantity of P adsorbed decreased with increasing salinity (2–30), and exhibited an inverted U-trend under the effect of pH (5–11). P adsorption increased with increasing P concentration under oxidation conditions (>400mV), but decreased under reduction conditions (0±100mV). These results could contribute to the restoration and management of intertidal zones.

Migration of two antibiotics during resuspension under simulated wind–wave disturbances in a water–sediment system

In this study, the migration of antibiotics (norfloxacin, NOR; and sulfamethoxazole, SMX) under simulated resuspension conditions across the sediment-water interface were quantified for two locations in China: point A, located in Meiliang Bay of Lake Taihu, and point B, located in Dapukou of Lake Taihu. The concentrations of suspended solids (SS) in the overlying water amounted to 100, 500, and 1000 mg/L during background, moderate, and strong simulated wind–wave disturbances, respectively. At each SS level, the initial concentrations of the two antibiotics were set to 1, 5, and 10 mg/L. The results showed that both resuspended SS and the initial concentration of antibiotics could influence the migration of NOR in the water–sediment system. Specifically, both higher SS and initial antibiotic concentrations were associated with higher rates of migration and accumulation of NOR from water to sediment. In contrast, the migration of SMX in the water–sediment system was not impacted by SS or initial antibiotic concentration. The adsorption capacities of sediments for NOR and SMX were significantly different at both locations, possibly reflecting differences in cation exchange capacity (CEC) and organic material (OM) contents. In general, higher CEC and OM values were found in sediments with a higher adsorption capacity for the antibiotics. When CEC and OM values of sediments were higher, the adsorption capacity reached up to 51.73 mg/kg. Large differences in the migration from water to sediment were observed for the two antibiotics, with NOR migration rates higher than those of SMX. The accumulation of NOR in surface sediment during resuspension was about 14 times higher than that of SMX. The main reason for this is that the chemical adsorption of NOR is seldom reversible. Overall, this study demonstrates that resuspension of NOR and SMX attached to sediments under simulated wind–wave disturbances can promote the migration of the antibiotics from water to sediment; these results could be useful for assessing the migration and fate of commonly used antibiotics in water–sediment systems.

Identification and Quantification of Nitrogen in a Reservoir, Jiaodong Peninsula, China.

Identification of nitrogen (N) sources is important in water quality control and management. Nitrogen pollution can lead to eutrophication of waterbodies and high concentrations of nitrate in drinking water can pose potential health problems. The 15N isotope and nitrogen fluxes budget approach is useful for determining the source of <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="00369-ilm01.gif"/> to surface waters. In this study, mass balance and 15N isotope approaches and nitrogen flux budgets were applied to identify total nitrogen (TN) sources and nitrogen transformation processes in the Menlou Reservoir (MR), Jiaodong Peninsula, China. The different fractions of nitrogen and their 15N isotope signatures were analyzed in the reservoir water, river water, groundwater, soil, and atmospheric precipitation. The results indicate that surface runoff pollution (e.g., fertilizer and animal manure) is the main source of <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="00369-ilm12.gif"/> in MR. High concentrations of TN in MR are caused by low nitrogen self-purification (denitrification) rate, low sediment adsorption capacity, and the influx of <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="00369-ilm23.gif"/> rich groundwater.

Effects of Reclaimed Water on the Characteristics of Dimethyl Phthalate Adsorption on Sediments

Adsorptions of Dimethyl Phthalate (DMP) on three sediments in both reclaimed and ultrapure water were studied using the batch technique and the effects of reclaimed water on it were clarified. The data were interpreted by using Freundlich and Dubinin-Radushkviech models. The values of 1/n were among 0.207 to 0.766, showing the presence of multiple adsorption sites on sediments. Compared with the ultrapure water as the background solution, the adsorption capacities of sediments for DMP were reduced in case of reclaimed water due to the competition of substances in reclaimed water. The mean adsorption energy, E, is smaller in the reclaimed water than that in ultrapure water.