Effects of nature organic matters and hydrated metal oxides on the anaerobic degradation of lindane,p,p'-DDT and HCB in sediments

Effects of natural organic matters(NOM) and hydrated metal oxides(HMO) in sediments on the anaerobic degradation of γ 666, p,p' DDT and HCB were investigated by means of removing NOM and HMO in Liaohe River sediments sequentially. The results showed that the anaerobic degradation of γ 666, p,p' DDT and HCB followed pseudo first order kinetics in different sediments. But, the extents and rates of degradation were different, even the other conditions remained the same. Anaerobic degradation rates of γ 666, p,p' DDT and HCB were 0 020 d -1 , 0 009 d -1 and 0 035 month -1 respectively for the sediments without additional carbon resources. However, with addition of carbon resources, the anaerobic degradation rates of γ 666, p, p ' DDT and HCB were 0 071 d -1 , 0 054 d -1 and 0 088 month -1 in the original sediments respectively. After removing NOM, the rates were decreased to 0 047 d -1 , 0 037 d -1 and 0 066 month -1 ; in the sediments removed NOM and HMO, the rates were increased to 0 067 d -1 , 0 059 d -1 and 0 086 month -1 . These results indicated that NOM in the sediments accelerated the anaerobic degradation of γ 666, p,p' DDT and HCB; the HMO inhibited the anaerobic degradation of γ 666, p,p' DDT and HCB.

Effects of pre-ozonation on organic matter removal by coagulation with IPF-PACl

Ozone plays an important role as a disinfectant and oxidant in potable water treatment practice and is increasingly being used as a pre-oxidant before coagulation. The purpose of this study is to obtain insight into the mechanisms that are operative in pre-ozonized coagulation. Effects ofpre-ozonation on organic matter removal during coagulation with IPF-PAC1 were investigated by using PDA （photometric disperse analysis）, apparent molecular weight distribution and chemical fractionation. The dynamic formation of flocs during coagulation process was detected. Changes of aquatic organic matter （AOM） structure resulted from the influence of pre-ozonation were evaluated. Results show that dosage of O3 and characteristics of AOM are two of the major factors influencing the performance of O3 on coagulation. No significant coagulation-aid effect of O3 was observed for all experiments using either A1C13 or PAC1. On the contrary, with the application of pre-ozonation, the coagulation efficiency of A1C13 was significantly deteriorated, reflected by the retardation of floc formation, and the removal decreases of turbidity, DOC, and UV254. However, if PACl was used instead of AlCl3, the adverse effects of pre-ozonation were mitigated obviously, particularly when the O3 dosage was less than 0.69 （mg O3/mg TOC）. The difference between removals of UV254, and DOC indicated that pre-ozonation greatly changed the molecular structure of AOM, but its capability of mineralization was not remarkable. Only 5% or so DOC was removed by pre-ozonation at 0.6--0.8 mg/L alone. Fractionation results showed that the organic products of pre-ozonation exhibited lower molecular weight and more hydrophilicity, which impaired the removal of DOC in the following coagulation process.

Characteristics of the natural organic matter sorption affects of organic contaminants

Several soil samples were used to study how the characteristics of natural organic matter (NOM) affect sorption of organic compounds. These soils contains different amounts and types of NOM. Aromaticity of NOM (percentage of aromatic carbons) was determined from solid state CPMAS 13 C NMR spectra and the soil effective polarity was computed from the equation developed by Xing et al . Naphthalene was used to examine the sorption characteristics of NOM. Both aromaticity and polarity of NOM strongly affected sorption of naphthalene. Old NOM showed higher affinity than that in the surface, young soils. Sorption increased with increasing aromaticity and decreasing polarity. Thus, the sorption coefficients of organic contaminants cannot be accurately predicted without some consideration of NOM characteristics.

Microbial Changes in the Fluorescence Character of Natural Organic Matter from a Wastewater Source

Natural Organic Matter (NOM) is a mixture of aromatic and aliphatic organic compounds of natural origin in any type of aquatic system. Human activities impact the constituents of NOM, from its production to its fate, particularly in the treatment of domestic waste waters. In this work, the impact of microorganisms isolated from a Waste Water Treatment Plant (WWTP) was investigated to determine the fate of NOM fractions in raw sewage, using fluorescence spectroscopy. Wastewater samples were taken at three different times from a WWTP, and incubated for 4 days under two treatments: 1) “raw sewage”, and 2) “spiked”, i.e., the same raw sewage, spiked with bacteria previously isolated from the WWTP. The incubated waters were analyzed by fluorescence spectroscopy, digitally resolved into NOM components: humic- and fulvic-like, and two types of protein-like, i.e., tryptophan- and tyrosine-like, using a Parallel Factor Analysis routine (PARAFAC). The results demonstrate that the “spiked” samples showed the largest changes with incubation time. The signals of the tryptophan- and tyrosine-like components decreased, suggesting a net microbial digestion of proteinaceous material. In contrast, the fulvic-like signals, and to some extent, the humic-like signals increased, suggesting the production of the associated molecular materials during the incubation period. This study provides direct evidence of human impact on the make-up of NOM: the cultures of microbes found at a WWTP consume the proteinaceous material, whereas humic-like and fulvic-like materials are produced.

Investigation of the Photosensitized Mechanisms of PCBs in the Presence of Natural Organic Matter

The structures of 26 different congeners of polychlorinated biphenyls（PCBs, including monothrough deca-chlorinated） were optimized using density functional theory（DFT） calculations with the 6-31＋G（d,p） basis set. The activation energies for the dechlorination of these systems were calculated for direct photodegradation and photosensitized degradation reaction pathways in the presence of natural organic matter（NOM）. The dechlorination mechanism of these PCBs and the ring-opening reaction mechanisms（using QST3 method） of the photosensitive degradation products were analyzed. The results showed that（i） the activation energy for the photosensitized degradation of PCBs was much lower than that of direct photodegradation;（ii） the degradation activities（i.e., C–Cl bond cleavage energies） were the same for both degradation pathways and followed the order ortho 〉 meta 〉 para;（iii） the degradation activities of asymmetric PCBs were higher than those of the corresponding symmetrical PCBs for the direct photodegradation and it was completely opposite in the photosensitive degradation;（iv） there was no correlation between the dissociation energy and the number of C–Cl bonds for the direct photodegradation and dechlorination products were all biphenyl;（v） the degradation activity of PCBs decreased as the number of C–Cl bonds increased in the presence of NOM; and（vi） even when the dechlorination reaction was incomplete, it produced chlorophenol. Furthermore, the free radicals of NOM led to the ring-opening reactions of PCBs via an initial addition step. The main site of these ring-opening reactions was the ortho position. Notably, the likelihood of ring-opening reactions occurring involving the degradation products increased as the degradation degree of PCBs increased.

ATR-FTIR and XPS study on the structure of complexes formed upon the adsorption of simple organic acids on aluminum hydroxide

Information on the binding of organic ligands to metal （hydr）oxide surfaces is useful for understanding the adsorption behaviour of natural organic matter on metal （hydr）oxide. In this study, benzoate and salicylate were employed as the model organic ligands and aluminum hydroxide as the metal hydroxide. The attenuated total reflectance Fourier transform infrared （ATR-FTIR） spectra revealed that the ligands benzoate and salicylate do coordinate directly with the surface of hydrous aluminum hydroxide, thereby forming innersphere surface complexes. It is concluded that when the initial pH is acidic or neutral, monodentate and bridging complexes are to be formed between benzoate and aluminum hydroxide while bridging complexes predominate when the initial pH is alkalic. Monodentate and bridging complexes can be formed at pH 5 while precipitate and bridging complexes are formed at pH 7 when salicylate anions are adsorbed on aluminum hydroxide. The X-ray photoelectron （XP） spectra demonstrated the variation of C 1 s binding energy in the salicyate and phenolic groups before and after adsorption. It implied that the benzoate ligands are adsorbed through the complexation between carboxylate moieties and the aluminum hydroxide surface, while both carboxylate group and phenolic group are involved in the complexation reaction when salicylate is adsorbed onto aluminum hydroxide. The information offered by the XPS confirmed the findings obtained with ATR-FTIR.

Investigation of organic fouling of microfiltration membrane

Because the natural organic matters (NOMs) and proteins are the principal foulants of microfiltration membranes in drinking water, the primary aim of this paper is to obtain a better understanding of the interactions between those foulants and the microfiltration membrane from a novel view of coagulation. Based on reviewed literature and our own analysis, the authors consider that the behaviors of NOMs in the fouling of microfiltration membrane are like a form of crystal growth, and we recognize that the extent of the membrane hydrophobicity plays an essential role in NOMs fouling. However, proteins’ fouling is more affected by intermolecular interaction. Additionally, the effect of membrane surface chemistry is not as essential as it is in the situation of NOMs.

Aggregation and stability of selenium nanoparticles: Complex roles of surface coating, electrolytes and natural organic matter

The application of selenium nanoparticles(SeNPs)as nanofertilizers may lead to the release of SeNPs into aquatic systems.However,the environmental behavior of SeNPs is rarely studied.In this study,using alginate-coated SeNPs(Alg-SeNPs)and polyvinyl alcohol-coated SeNPs(PVA-SeNPs)as models,we systematically investigated the aggregation and stability of SeNPs under various water conditions.PVA-SeNPs were highly stable in mono-and polyvalent electrolytes,probably due to the strong steric hindrance of the capping agent.Alg-SeNPs only suffered from a limited increase in size,even at 2500 mmol/L NaCl and 200 mmol/L MgCl_(2),while they underwent apparent aggregation in CaCl_(2) and LaCl_(3) solutions.The binding of Ca^(2+) and La^(3+) with the guluronic acid part in alginate induced the formation of cross-linking aggregates.Natural organic matter enhanced the stability of Alg-SeNPs in monovalent electrolytes,while accelerated the attachment of Alg-SeNPs in polyvalent electrolytes,due to the cation bridge effects.The long-term stability of SeNPs in natural water showed that the aggregation sizes of Alg-SeNPs and PVA-SeNPs increased to several hundreds of nanometers or above 10μm after 30 days,implying that SeNPs may be suspended in the water column or further settle down,depending on the surrounding water chemistry.The study may contribute to the deep insight into the fate and mobility of SeNPs in the aquatic environment.The varying fate of SeNPs in different natural waters also suggests that the risks of SeNPs to organisms living in diverse depths in the aquatic compartment should be concerned.

Virus Removal by Iron Coagulation Processes

Waterborne viruses account for 30% to 40% of infectious diarrhea, and some viruses could persevere for some months in nature and move up to 100 m in groundwater. Using filtration setups, coagulation could lessen virus charges as an efficient pre-treatment for reducing viruses. This work discusses the present-day studies on virus mitigation using coagulation in its three versions i.e., chemical coagulation (CC), enhanced coagulation, and electrocoagulation (EC), and debates the new results of virus demobilization. The complexity of viruses as bioparticles and the process of virus demobilization should be adopted, even if the contribution of permeability in virus sorption and aggregation needs to be clarified. The information about virion permeability has been evaluated by interpreting empirical electrophoretic mobility (EM). No practical measures of virion permeability exist, a clear link between permeability and virion composition and morphology has not been advanced, and the direct influence of inner virion structures on surface charge or sorption has yet to be conclusively demonstrated. CC setups utilizing zero-valent or ferrous iron could be killed by iron oxidation, possibly using EC and electrooxidation (EO) methods. The oxidants evolution in the iron oxidation method has depicted promising findings in demobilizing bacteriophage MS2, even if follow-up investigations employing an elution method are needed to secure that bacteriophage elimination is related to demobilization rather than sorption. As a perspective, we could be apt to anticipate virus conduct and determine new bacteriophage surrogates following subtle aspects such as protein structures or genome size and conformation. The present discussion’s advantages would extend far beyond an application in CC—from filtration setups to demobilization by nanoparticles to modeling virus fate and persistence in nature.

Effect of a seasonal diffuse pollution migration on natural organic matter behavior in a stratified dam reservoir

This article aims to describe the influence of diffuse pollution on the temporal and spatial characteristics of natural organic matter （NOM） in a stratified dam reservoir, the Daecheong Dam, on the basis of intensive observation results and the dynamic water quality simulation using CE-QUAL-W2. Turbidity is regarded as a comprehensive representation of allochothonous organic matter from diffuse sources in storm season because the turbidity concentration showed reasonable significance in a statistical correlation with the UV absorbance at 254 nm and total phosphorus. CE-QUAL-W2 simulation results showed good consistency with the observed data in terms of dissolved organic matter （DOM） including refractory dissolved organic carbon （RDOC） and labile DOC and also well explained the internal movement of constituents and stratification phenomenon in the reservoir. Instead turbidity and NOM were related well in the upper region of the reservoir according to flow distance, gradually as changing to dissolved form of organic matter, RDOM affected organic matter concentration of reservoir water quality compared to turbidity. To control the increase of soluble organic matters in the dam reservoir, appropriate dam water discharge gate operation provided effective measurement. Because of the gate operation let avoid the accumulation of organic matter within a dam reservoir by shorten of turbid regime retention time.

Molecular characterization of transformation and halogenation of natural organic matter during the UV/chlorine AOP using FT-ICR mass spectrometry

UV/chlorine process,as an emerging advanced oxidation process(AOP),was effective for removing micro-pollutants via various reactive radicals,but it also led to the changes of natural organic matter(NOM)and formation of disinfection byproducts(DBPs).By using negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS),the transformation of Suwannee River NOM(SRNOM)and the formation of chlorinated DBPs(Cl-DBPs)in the UV/chlorine AOP and subsequent post-chlorination were tracked and compared with dark chlorination.In comparison to dark chlorination,the involvement of Cl O·,Cl·,and HO·in the UV/chlorine AOP promoted the transformation of NOM by removing the compounds owning higher aromaticity(AI mod)value and DBE(double-bond equivalence)/C ratio and causing the decrease in the proportion of aromatic compounds.Meanwhile,more compounds which contained only C,H,O,N atoms(CHON)were observed after the UV/chlorine AOP compared with dark chlorination via photolysis of organic chloramines or radical reactions.A total of 833 compounds contained C,H,O,Cl atoms(CHOCl)were observed after the UV/chlorine AOP,higher than 789 CHOCl compounds in dark chlorination,and one-chlorine-containing components were the dominant species.The different products from chlorine substitution reactions(SR)and addition reactions(AR)suggested that SR often occurred in the precursors owning higher H/C ratio and AR often occurred in the precursors owning higher aromaticity.Post-chlorination further caused the cleavages of NOM structures into small molecular weight compounds,removed CHON compounds and enhanced the formation of Cl-DBPs.The results provide information about NOM transformation and Cl-DBPs formation at molecular levels in the UV/chlorine AOP.

Effects of a dynamic membrane formed with polyethylene glycol on the ultrafiltration of natural organic matter

The formation of a dynamic membrane(DM)was investigated using polyethylene glycol(PEG)(molecular weight of 35000 g/mol,concentration of 1 g/L).Two natural organic matters(NOM),Dongbok Lake NOM(DLNOM)and Suwannee River NOM(SRNOM)were used in the ultrafiltration experiments along with PEG.To evaluate the effects of the DM with PEG on ultrafiltration,various transport experiments were conducted,and the analyses of the NOM in the membrane feed and permeate were performed using high performance size exclusion chromatography,and the effective pore size distribution(effective PSD)and effective molecular weight cut off(effective MWCO)were determined.The advantages of DM formed with PEG can be summarized as follows:(1)PEG interferes with NOM transmission through the ultrafiltration membrane pores by increasing the retention coefficient of NOM in UF membranes,and(2)low removal of NOM by the DM is affected by external factors,such as pressure increases during UF membrane filtration,which decreases the effective PSD and effective MWCO of UF membranes.However,a disadvantage of the DM with PEG was severe flux decline;thus,one must be mindful of both the positive and negative influences of the DM when optimizing the UF performance of the membrane.

Formation of regulated and unregulated disinfection byproducts during chlorination and chloramination: Roles of dissolved organic matter type, bromide, and iodide

Algal blooms and wastewater effluents can introduce algal organic matter(AOM) and effluent organic matter(Ef OM) into surface waters, respectively. In this study, the impact of bromide and iodide on the formation of halogenated disinfection byproducts(DBPs) during chlorination and chloramination from various types of dissolved organic matter(DOM, e.g., natural organic matter(NOM), AOM, and Ef OM) were investigated based on the data collected from literature. In general, higher formation of trihalomethanes(THMs) and haloacetic acids(HAAs) was observed in NOM than AOM and Ef OM, indicating high reactivities of phenolic moieties with both chlorine and monochloramine. The formation of haloacetaldehydes(HALs), haloacetonitriles(HANs) and haloacetamides(HAMs) was much lower than THMs and HAAs. Increasing initial bromide concentrations increased the formation of THMs, HAAs, HANs, and HAMs, but not HALs. Bromine substitution factor(BSF) values of DBPs formed in chlorination decreased as specific ultraviolet absorbance(SUVA) increased. AOM favored the formation of iodinated THMs(I-THMs) during chloramination using preformed chloramines and chlorination-chloramination processes. Increasing prechlorination time can reduce the I-THM concentrations because of the conversion of iodide to iodate, but this increased the formation of chlorinated and brominated DBPs. In an analogous way, iodine substitution factor(ISF) values of I-THMs formed in chloramination decreased as SUVA values of DOM increased. Compared to chlorination, the formation of noniodinated DBPs is low in chloramination.

Membrane flux dynamics in the submerged ultrafiltration hybrid treatment process during particle and natural organic matter removal

Particles and natural organic matter （NOM） are two major concerns in surface water, which greatly influence the membrane filtration process. The objective of this article is to investigate the efiect of particles, NOM and their interaction on the submerged ultrafiltration （UF） membrane flux under conditions of solo UF and coagulation and PAC adsorption as the pretreatment of UF. Particles, NOM and their mixture were spiked in tap water to simulate raw water. Exponential relationship, （JP/JP0 = a×exp{-k[t-（n-1）T]}）, was developed to quantify the normalized membrane flux dynamics during the filtration period and fitted the results well. In this equation, coefficient a was determined by the value of JP/JP0 at the beginning of a filtration cycle, refiecting the flux recovery after backwashing, that is, the irreversible fouling. The coefficient k refiected the trend of flux dynamics. Integrated total permeability （ΣJP） in one filtration period could be used as a quantified indicator for comparison of different hybrid membrane processes or under different scenarios. According to the results, there was an additive effect on membrane flux by NOM and particles during solo UF process. This additive fouling could be alleviated by coagulation pretreatment since particles helped the formation of flocs with coagulant, which further delayed the decrease of membrane flux and benefited flux recovery by backwashing. The addition of PAC also increased membrane flux by adsorbing NOM and improved flux recovery through backwashing.

Linking the electron donation capacity to the molecular composition of soil dissolved organic matter from the Three Gorges Reservoir areas,China

Soil dissolved organic matter(DOM)plays an essential role in the Three Gorges Reservoir(TGR)as a linkage between terrestrial and aquatic systems.In particular,the reducing capacities of soil DOM influence the geochemistry of contaminants such as mercury(Hg).However,few studies have investigated the molecular information of soil DOM and its relationship with relevant geochemic al reactivities,including redox properties.We collected samples from eight sites in the TGR areas and studied the link between the molecular characteristics of DOM and their electron donation capacities(EDCs)toward Hg(II).The average kinetic rate and EDC of soil DOM in TGR areas were(0.004±0.001)hr-1 and(2.88±1.39)nmol e-/mg DOMbulk,respectively.Results suggest that higher EDCs and relatively rapid kinetics were related to the greater electron donating components of ligninderived and perhaps pyrogenic DOM,which are the aromatic constituents that influenced the reducing capacities of DOM in the present study.Molecular details revealed that even the typical autochthonous markers are important for the EDCs of DOM as well,in contrast to what is generally assumed.More studies identifying specific DOM molecular components involved in the abiotic reduction of Hg(II)are required to further understand the relations between DOM sources and their redox roles in the environmental fate of contaminants.

Combination of chlorine and magnetic ion exchange resin for drinking water treatment of algae

The effectiveness of a magnetic ion exchange resin （MIEX） for the treatment of Hongze Lake water in China was evaluated, The kinetics of natural organic matter （NOM） removal at various MIEX doses and contact time, multiple-loading experiments, impacts of MIEX prior to coagulation on coagulant demands and the effectiveness of combination of MIEX, pre-chlorination and coagulation were investigated. Kinetic experimental results show that more than 80% UV254 and 67% dissolved organic carbon （DOC） from raw water can be removed by the use of MIEX alone. 94% sulfate, 69% nitrate and 98% bromide removals are obtained after the first use of MIEX in multiple-loading experiments. It is suggested that MIEX can be loaded up to 1 250 bed volume （BV, volume ratio of tested water to resin） or more without saturation when regarding organics removal as a target. MIEX can remove organics to a greater extend than coagulation and lower the coagulant demand when combining with coagulation. Chlorination experimental results show that MIEX can remove 57% chlorine demand and 77% trihalomethane formation potential （THMFP） for raw water. Pre-chlorination followed by MIEX and coagulation can give additional organic and THMFP removals. The results suggest that MIEX provides a new method to solve thc problem algae reproduction.

Removal of Natural Organic Matter by Forward Osmosis Membrane： Flux Behaviour and Foulant Characterization

Fouling of cellulose triacetate（CTA） forward osmosis（FO） membranes by natural organic matter（NOM） was studied by means of a cross-flow fiat-sheet forward osmosis membrane system. The NOM solution was employed as the feed solution（FS）, and a sodium chloride solution（3 tool/L） was used for the draw solution（DS）. The process was conducted at various temperatures and cross-flow velocities. The flux decline was investigated with 3 h forward osmosis operation. The substances absorbed on the membranes were cleaned by ultrasonic oscillation of the fouled membranes and were characterized by methodologies including fluorescence excitation-emission matrices （EEMs） and liquid chromatography with an organic carbon detector（LC-OCD）, and the variations of membrane properties were also investigated by Fourier transform infrared spectrometer（FTIR） and a contact angle meter. It was noted that the rejection efficiency of NOM is remarkable and that ultrasonic oscillation is an effective method to extract the NOM fouled on the CTA membranes after FO process. A higher cross-flow velocity and lower temperature benefit the anti-fouling capacity of the membrane significantly. Although humic substances accounted for the majority of the NOM, aromatic proteins and amino acids were the main fouling components on the membranes, with symbolic FTIR peaks at 2355, 1408 and 873 cm^-1. The present surface foulant made the membranes becoming more hydrophilic, as demonstrated by a significant decrease in contact angle（ranging from 20% to 46%） under all the operation conditions.

Environmental Behaviors and Biological Effects of Engineered Nanomaterials:Important Roles of Interfacial Interactions and Dissolved Organic Matter

With the fast development of nanotechnology,reactive engineered nanomaterials(ENMs)are increasingly discharged into the environment,where they interact with environmental components and organisms and thus pose potential risks.The interactions-derived formation of nano-environmental and nano-bio interfaces determines environmental behaviors and biological effects of ENMs,and ubiquitous dissolved organic matter(DOM)is bound to impact the interfacial interactions and the resulted environmental risks.Herein,we systematically investigated adsorptive interactions between ENMs and various DOM representatives,and thereby demonstrated the effects of DOM on the aqueous suspension/aggregation,mobility in porous media,adsorption of contaminants,transformation,and biological accumulation and toxicity of ENMs.Overall,we conclude that natural DOM can in general expand environmental distribution of ENMs while limit their toxicity to organisms.

Characterization of natural organic matter in water for optimizing water treatment and minimizing disinfection by-product formation

Introduction Natural organic matter（NOM）present in source water has significant impact on water treatment processes and on the quality of drinking water.NOM is a complex mixture of diverse groups of organic compounds,humic and fulvic acids,proteins,peptides,carbohydrates,and heterogeneous materials

Underestimation of phosphorus fraction change in the supernatant after phosphorus adsorption onto iron oxides and iron oxide–natural organic matter complexes

The phosphorus（P） fraction distribution and formation mechanism in the supernatant after P adsorption onto iron oxides and iron oxide-humic acid（HA） complexes were analyzed using the ultrafiltration method in this study.With an initial P concentration of 20 mg/L（I =0.01 mol/L and pH = 7）,it was shown that the colloid（1 kDa-0.45 μm） component of P accounted for 10.6%,11.6%,6.5%,and 4.0%of remaining total P concentration in the supernatant after P adsorption onto ferrihydrite（FH）,goethite（GE）,ferrihydrite-humic acid complex（FH-HA）,goethite-humic acid complex（GE-HA）,respectively.The 〈1 kDa component of P was still the predominant fraction in the supernatant,and underestimated colloidal P accounted for 2.2%,55.1%,45.5%,and 38.7%of P adsorption onto the solid surface of FH,FH-HA,GE and GE-HA,respectively.Thus,the colloid P could not be neglected.Notably,it could be interpreted that Fe3＋ hydrolysis from the adsorbents followed by the formation of colloidal hydrous ferric oxide aggregates was the main mechanism for the formation of the colloid P in the supernatant.And colloidal adsorbent particles co-existing in the supernatant were another important reason for it.Additionally,dissolve organic matter dissolved from iron oxide-HA complexes could occupy large adsorption sites of colloidal iron causing less colloid P in the supernatant.Ultimately,we believe that the findings can provide a new way to deeply interpret the geochemical cycling of P,even when considering other contaminants such as organic pollutants,heavy metal ions,and arsenate at the sediment/soil-water interface in the real environment.