Characteristics of dissolved organic matter(DOM) in leachate with different landfill ages

The main objective of the study was to investigate the characteristics of dissolved organic matter （DOM） in leachate with different landfill ages through the chemical, spectroscopic, and elemental analysis. Humic acid （HA）, fulvic acid （FA）, and hydrophilic （HyI） fractions were isolated and purified by the XAD-8 resin combined with the cation exchange resin method. The analytical results of fluorescence excitation-emission matrix spectroscopy （EEMs） revealed that the fluorescence peaks were protein-like fluorescence for young landfill leachate, while the fluorescence peaks for medium and old landfill leachate were humic-like and fulvic-like fluorescence, respectively. Elemental analysis showed that carbon, hydrogen, and nitrogen content decreased with landfill age, while the oxygen content increased. Moreover, the nitrogen content in these isolated fractions followed： HA 〉 HyI 〉 FA. The results of elemental analysis, FT-IR, and fluorescence EEMs also confirmed that aromatic carbons and portions of aliphatic functional groups were more abundant in leachate samples with increasing landfill age.

Effect of dissolved organic matter on adsorption and desorption of mercury by soils

Effects of dissolved organic matter (DOM) on adsorption and desorption of Hg were investigated in two kinds of soils, Xanthi-Udic Ferralosols (XUF) and Typic Purpli-Udic Cambosols (TPUC). The DOM was obtained from humus soil (DOMH), rice straw (DOMR), and pig manure (DOMP). The presence of DOM obviously reduced Hg maximum adsorption capacity with up to 40% decreases over the control, being an order of DOMH (250.00 mg/kg)< DOMR (303.03 mg/kg) < DOMP (322.58 mg/kg) < CK (control 416.67 mg/kg) for the...

Sorption of dissolved organic matter and its effects on the atrazine sorption on soils

The dissolved organic matter(DOM), water soluble organic matter derived from sewage sludge was separated into hydrophobic fraction(Ho) and hydrophilic fraction(Hi). The sorption of DOM and its fractions on soils and the effects of DOM sorption on a nonionic pesticide(atrazine(2-chloro-4-ethylamino-6-isopropylamino-1,3,5-trazine)) distribution between soil and water were investigated using a batch equilibrium technique. The total DOM sorption on soils described by the Langmuir equation reached saturation as the DOM concentration increased. The sorption of Ho fit the Freundlich model. In contrast, a negative retention evidently occurred as adding Hi at higher level in tested soils. The sorption of Ho dominated the total DOM sorption and the release of soil organic matter(SOM). Effects of DOM on the atrazine sorption by soils were DOM-concentration dependent and dominated by the interaction of atrazine, DOM, and soil solids. Generally, the presence of DOM with lower concentration promoted atrazine sorption on soils, namely the apparent partitioning constant(K*_d) for atrazine sorption in the presence of DOM was larger than the distribution constant(K_d) without DOM; whereas the presence of DOM with higher concentration inhibited atrazine sorption(i.e., K*_d<K_d). The overall effects of DOM on atrazine sorption in soils might be related to the DOM sorption and the release of soil intrinsic organic matter into aqueous solution. The sorption of Ho on soils promoted the atrazine sorption on soil, while the release of SOM by Hi and the competitive sorption between Hi and atrazine on soil surface led to a decrease of atrazine sorption. Information provided in this work may contribute to a better understanding of the DOM sorption and its impacts on the contaminant soil-water distribution.

Fluorescence characteristic changes of dissolved organic matter during municipal solid waste composting

Dissolved organic matter（DOM） of municipal solid waste（MSW） consists of minerals, water, ash and humic substances, and is known to enhance plant growth. In this study, inoculating microbes（Z J, MS） were used in municipal solid wastes composting, and composting implemented a industrialized technology. During composting, dissolved organic matter was extracted from the compost and purified. The spectral characteristics of dissolved organic matter was determined by fluorescence emission, excitation, and synchronous spectroscopy. Fluorescence emission, excitation, and synchronous spectra characterized by different relative fluorescent intensities and peaks over time. Fluorescence spectra were similar to that of fulvic acid in sewage sludge, indicating the presence of dissolved organic matter with aromatic structures and a high degree of molecular polymerization. Compared with the controls with no microbial inoculation, the microbe-inoculated treatments exhibited the increase of aromatic polycondensation, in the following order： MS ＋ ZJ 〉 ZJ 〉 MS 〉 CK.

Binding of pyrene to dissolved organic matters: fractionation and characterization

Based on a modified Leenheer DOM fractionation scheme, fractionation of DOM from the paddy soil was conducted by using XAD-8 resin into hydrophobic bases(HOB), hydrophobic acids(HOA), acid-insoluble matter(AIM), hydrophobic neutrals(HON) and hydrophilic matter(HIM). In total carbon content of DOM, 35.32% were the HIM and only 0.73% the HOB. However, HOA and AIM altogether occupied 53.45%, while the HON fraction represented 10%. The sorption experiments were conducted to determine the sorption capacity of pyrene on unfractionated DOM and its fractions. Elemental analysis, 1H-NMR and FTIR spectra were carried out on unfractionated DOM and its fractions to examine the relationship between the structure of DOM and partition coefficients(K oc). The results showed that HON had a greater affinity for binding pyrene than other fractions. While HON was characterized by large long-chain alkylate (aliphatic structure). AIM exhibited relative higher K oc values than HOA and HIM, due to much aromatic structure in AIM, while the high content of carboxylic groups of HOA and HIM depressed their binding capacity. This study demonstrated HON is a key subcomponents of DOM in binding of pyrene, in other words, aliphalic structure in DOM play an important role in binding of pyrene.

Characteristics of dissolved organic matter in lakes with different eutrophic levels in southeastern Hubei Province,China

Dissolved organic matter(DOM)plays a crucial role in both the carbon cycle and geochemical cycles of other nutrient elements,which is of importance to the management and protection of the aquatic environments.To achieve a more comprehensive understanding the characteristics of DOM in the Changjiang(Yangtze)River basin,water samples from four natural lakes(Xiandao,Baoan,Daye,and Qingshan)in southeastern Hubei Province in China with different eutrophication levels were collected and analyzed.The optical characteristics were analyzed using ultraviolet-visible spectrophotometry and excitation-emission matrix spectroscopy coupled with parallel factor analysis.The results show that:(1)two humic-like components(C1 and C2)and two protein-like substances(C3 and C4)of DOM were identified in all waterbodies;(2)C3 originated primarily from the degradation of microalgae and contributed substantially to humic-like components during transformation.C4 was widely present in the Changjiang River basin and its formation was related to microbial activity,rather than algal blooms or seasons.Influenced by the water mixing,the protein-like components were more likely to be transformed by microorganism,whereas humic-like components were more easily to be photobleached;(3)the concentration of DOM and the fluorescence intensity of humic-like components gradually increased with rising lake eutrophication levels.With respect to protein-like components,only C3 showed changes along the eutrophication gradients;(4)DOM showed a high affinity with permanganate index(COD Mn)and chlorophyll a(chl a)while the relationship was variable with phosphorus.This study helps us systematically understand the DOM characteristics,microbial activities,and pollutant transformation in the Changjiang River basin and provides reference to the ecological restoration of aquatic environments.

Multivariate analysis of fluorescence and source identification of dissolved organic matter in Jiaozhou Bay, China

Hierarchical clustering analysis and principal component analysis （PCA） methods were used to assess the similarities and dissimilarities of the entire Excitation-emission matrix spectroscopy （EEMs） data sets of samples collected from Jiaozhou Bay, China. The results demonstrate that multivariate analysis facilitates the complex data treatment and spectral sorting processes, and also enhances the probability to reveal otherwise hidden information concerning the chemical characteristics of the dissolved organic matter （DOM）. The distribution of different water samples as revealed by multivariate results has been used to track the movement of DOM material in the study area, and the interpretation is supported by the results obtained from the numerical simulation model of substance tracing technique, which show that the substance discharged by Haibo River can be distributed in Jiaozhou Bay.

Removal and transformation of dissolved organic matter in secondary effluent during granular activated carbon treatment

This paper focused on the removal and transformation of the dissolved organic matter(DOM) in secondary effluent during the granular activated carbon(GAC) treatment. Using XAD-8/XAD-4 resins,DOM was fractionated into five classes:hydrophobic acid(HPO-A) ,hydrophobic neutral(HPO-N) ,transphilic acid(TPI-A) ,transphilic neutral(TPI-N) and hydrophilic fraction(HPI) . Subsequently,the water quality parameters of dissolved organic carbon(DOC) ,absorbance of ultraviolet light at 254 nm(UV-254) ,specific ultraviolet light absorbance(SUVA) and trihalomethane formation potential(THMFP) were analyzed for the unfractionated and fractionated water samples. The results showed that the order of the DOC removal with respect to DOM fractions was observed to be HPI>HPO-A>HPO-N>TPI-A>TPI-N. During the GAC treatment,the THMFP of the unfractionated water samples decreased from 397.4 μg/L to 176.5 μg/L,resulting in a removal efficiency of 55.6%. The removal order of the trihalomethanes(THMs) precursor was as follows:HPO-A>TPI-A>TPI-N>HPO-N>HPI. By the GAC treatment,the specific THMFP of HPO-A,TPI-A,TPI-N and the original unfractionated water samples had a noticeable decrease,while that of HPO-N and HPI showed a converse trend. The Fourier transform infrared(FTIR) results showed that the hydroxide groups,carboxylic acids,aliphatic C-H were significantly reduced by GAC treatment.

Dissolved Organic Matter-Complexed Iron in Two Rivers with Different Types of Soils in Watershed Area

Concentrations of dissolved organic matter (DOM), dissolved humic substances (DHS), and DOM-complexed Fe (DOM-Fe) in Yamakuni and Oita Rivers, Japan, of which headstream is near in location, flow pass length is similar, but watershed soil type differs, were investigated. Soil organic matter level was higher in black Andosols distributing 67% of the watershed area of the Oita River than in Cambisols covering 90% of the watershed area of Yamakuni River. However, the DOM concentration in the Yamakuni River (0.44 - 1.62 mg·C·L-1) tended to be higher than that in the Oita River (0.13 - 1.37 mg·C·L-1). DHS accounted for 49% - 80% of DOM in both rivers. Fe and DOM-Fe concentrations showed a trend to increase toward downstream but decrease at the estuary in both rivers. DOM-Fe accounted for 26% - 90% and 55% - 93% of dissolved Fe in the Yamakuni and Oita Rivers, respectively. Correlation analysis suggested that the DOM-Fe concentration in the river water was controlled by the capacity for supplying Fe ions rather than that for supplying DOM. Although the ability to form a complex with Fe was suggested to be greater in the DOM in the Oita River than that in the Yamakuni River, the DOM-Fe concentration at the estuary was similar in the two rivers. Thus, the effect of soil organic matter level in the watershed area on the supply of Fe or DOM-Fe to the estuarine ecosystem was not significant.

Improved speciation of dissolved organic nitrogen in natural waters: amide hydrolysis with fluorescence derivatization

The objective of this study was to improve primary-amine nitrogen (1°-N) quantification in dissolved organic matter (DOM) originating from natural waters where inorganic forms of N, which may cause analytical interference, are commonly encountered. Efforts were targeted at elucidating organic-N structural criteria influencing the response of organic amines to known colorimetric and fluorescent reagents and exploring the use of divalent metal-assisted amide hydrolysis in combination with fluorescence analyse...

Spatial heterogeneity and compositional profiles of dissolved organic matter in farmland soils across China' Mainland

Dissolved organic matter(DOM) plays an essential role in many geochemical processes,however its complexity, chemical diversity, and molecular composition are poorly understood. Soil samples were collected from 500 vegetable fields in administrative regions of China' Mainland, of which 122 were selected for further investigation. DOM properties were characterized by three-dimensional excitation-emission matrix(3D-EEM) fuorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry(FTICRMS)(field intensity is 15 Tesla). Our results indicated that the main constituents were UVA humic-like substances, humic-like substances, fulvic acid-like substances, and tyrosine-like substances. A total of 10,989 molecular formulae with a mass range of 100.04 to 799.59 Da were detected, covering the mass spectrometric information of the soil samples from 27 different regions. CHO and CHON molecules were dominant in DOM, whereas lignin, tannins,and aromatic substances served as the main components. The results of cluster analysis revealed that the soil properties in Jiangxi Province were considerably different from those in other regions. The key backgrounds of the DOM molecular characteristics in the vegetablefield soil samples across China' Mainland were provided at the molecular level, with large abundance and great variability.

洞庭湖DOM组成与有机碳收支对江湖水力连通的响应

洞庭湖是我国最大的通江湖泊之一,为探究洞庭湖溶解性有机物(DOM)组成、(DOC)收支与江湖水力连通间的内在关联,于2018年5月、7月、9月和11月在洞庭湖湘、资、沅、澧4支流和长江荆南松滋、虎渡、藕池3个入湖口以及洞庭湖出湖口城陵矶采集水样,并探究洞庭湖流域DOM的组成分异特征及其对江湖水力连通的响应.结果表明,入湖河流和城陵矶DOM吸收系数a254和陆源类腐殖酸组分C1在7月最高.DOC由入湖口(2.4±1.3mg)/L下降至出湖口(2.1±0.3)mg/L,而a254由入湖口(9.7±2.2)m^(-1)上升至出湖口(10.1±1.7)m^(-1).微生物培养前的DOC浓度为(2.4±1.0)mg/L,微生物降解后的DOC浓度为(2.1±0.9mg)/L,DOC的微生物活性,即BDOC最高值出现在澧水为50.3%.5月、7月、9月和11月入湖的DOC通量分别为(63.7±43.6)×10^(3)t,(60.1±7.3)×10^(3)t,(27.6±3.6)×10^(3)t,(31.9±13.9)×10^(3)t.洞庭湖因自身水力滞留时间短,导致DOM在湖内运移过程中较少被降解,全湖DOM来源组成受流域不同季节来水条件影响较大.

供水管网系统中DOM解析与DBPs生成特征

为保障城市供水安全,实现南方某市优质饮用水入户,通过对目前供水管网水质情况进行调查分析,明确供水管网系统中溶解性有机物(DOM)在不同季节、余氯及停留时间等参数条件下对消毒副产物(DBPs)生成情况的影响。研究表明:供水管网系统中常规水质指标如浑浊度、余氯和溶解性有机物主要取决于出厂水的浓度,供水管网中余氯变化较大,在管道中进行补氯有利于提升供水管网中不利点的居民饮用水安全。紫外和荧光光谱分析方法在供水管道中检测方便、检测限较低且不受其他工艺影响且检测浓度较低,可有效指示供水管道中存在的异常风险。三氯甲烷与卤乙酸是供水管网系统中主要存在的DBPs,其生成受到出厂水水质、管道、管道距离及季节性等多因素的影响,在供水管线中的含量变为随管线距离增长而增大;在温度较高的季节DBPs生成浓度高、反应速度快,应受到重点关注。

水厂臭氧-生物活性炭工艺对短链PFCs及DOM去除特性的中试

全氟化合物(PFCs)在水环境中广泛分布并存在潜在毒性,活性炭吸附是目前被认为从饮用水中去除PFCs的有效技术之一。然而,关于臭氧-生物活性炭(O3-BAC)在实际水体中对短链PFCs去除特性的研究较少,因此在目前地表水环境中短链PFCs的污染水平不断升高的背景下,亟需评估该工艺的应用效果。文中以水厂砂滤产水为水源,研究了3种短链PFCs(PFBA、PFPeA、PFHxA)和溶解性有机物(DOM)在连续运行90 d的O3-BAC中试装置中的去除效果,同时探讨了关停臭氧和臭氧的投加量对短链PFCs和DOM去除效果的影响。结果表明,随着运行时间的延长,3种短链PFCs在O3-BAC中试中的去除率显著下降并且出现了PFCs穿透和解吸附现象,去除率下降程度为:PFBA>PFPeA>PFHxA,而DOM相关的DOC、UV_(254)和Φ_((T,n))指标的去除率下降程度则相对缓慢。臭氧的投加能够氧化DOM从而改善短链PFCs在炭滤中的吸附去除,关停臭氧后流入炭滤的DOM会抢占已吸附短链PFCs的吸附位点,使PFCs解吸附提前发生。过高的臭氧投加量又会使更具竞争性的低分子量有机物增多,从而削弱炭滤对短链PFCs的去除能力。

华南中小型闸控入海河流DOM特征及藻源影响

本研究以华南地区中小型闸控入海河流黄江河、东溪河和练江(三河)为研究对象,于2022年逐月持续监测三河DOM特征,探讨DOM浓度时空分布、来源和藻类大量增殖对其影响.结果表明:黄江河、东溪河和练江溶解有机碳(DOC)占总有机碳(TOC)比例分别为78.6%、81.3%和67.2%,DOC为三河有机碳主要存在形式;三河DOC年均浓度分别为2.6,4.3和5.1mg/L,低于世界河流平均浓度但高于华南地区大型河流.荧光参数结果表明三河DOM具有陆源内源双重特征,内源贡献更明显.利用吸光特征量化藻源DOC贡献,三河藻源DOC浓度分别为1.2,1.8和2.2mg/L,藻源DOC占比分别为49.6%、42.6%和48.0%,进一步表明藻类内源是三河DOM主要来源.平行因子解析出3种类蛋白组分和2种类腐殖质组分,其中,受藻类异常增殖影响,表征内源类蛋白组分C1和C3总荧光强度枯水期显著高于丰水期,表征来自陆源类腐殖质组分C2和C4总荧光强度呈练江>东溪河>黄江河.因此,藻类大量增殖是三河DOC浓度高于华南地区大型河流、枯水期类蛋白组分C1和C3显著高于丰水期的主要原因之一,外源输入及河流理化参数,包括降雨、温度、盐度和营养盐浓度以及人为干扰(闸控调度)共同影响三河DOM浓度和组分.

基于FT-ICR MS表征达古冰川冬春季节表层雪中DOM分子组成变化

分析冰川中溶解性有机质(dissolved organic matter,DOM)的迁移转化特征是评估冰川消融对下游生态环境效应的重要依据,但冰川表层雪中DOM在冬春季节的迁移转化特征尚不明确。本文以达古冰川冬春季节表层雪和春季冰川径流为研究对象,使用傅里叶变换离子回旋共振质谱(FT-ICR MS)对表层雪和径流中DOM进行分子层次表征。结果显示:达古冰川冬春季节表层雪中DOM化学组成非常丰富,主要包括脂类、多肽类、不饱和烃类,还含有少量的酚类、多环芳烃类和糖类,来源包括微生物活动和陆源性输入。春季径流中DOM的主要来源是陆源性输入,受人类活动影响较大。分析不同季节表层雪DOM的分子组成变化,发现冬季低温环境有利于表层雪中脂类、多肽类和含S类DOM分子的富集,春季气温升高则有利于表层雪中多肽类、不饱和烃类和含N类DOM分子的富集。比较春季径流和表雪中DOM的分子组成变化,发现径流中杂原子类DOM含量降低,微生物来源的脂类和多肽类DOM含量降低,陆源性的酚类和多环芳烃类含量显著增加,说明径流中DOM的生物活性降低而光反应活性增加。因此随着冰川持续消融大量的冰川融水将DOM带入下游水环境,在微生物活动和光反应过程的共同作用下增加温室气体CO_(2)的排放,增强温室效应。

Ultraviolet humic-like component contributes to riverine dissolved organic matter biodegradation

Biological degradation of dissolved organic matter(DOM)regulates its structure and fate in river ecosystems.Previous views suggested that labile components were dominantly consumed by microbial metabolism.Here we provide new observations that a part of recalcitrant compounds largely contribute to riverine DOM biodegradation.The excitationemission matrix fluorescent spectroscopy combined with peak picking and parallel factor analysis are used to explore component variability during DOM incubation.Humic-like and tryptophan-like DOM are the primary components of riverine DOM,with proportion contributions of 39%–82% and 16%–61% for % of the maximumfluorescence intensity,respectively.After 56 days of aerobic incubation in the dark,large amounts of tyrosine-like DOM generation are observed.Elevated temperature enhances the decomposition of ultraviolet humiclike substance and further stimulates labile DOM bio-mineralization into carbon dioxide.Meanwhile,averaged proportions of amino acid compositions(peak B and T)markedly increase(p<0.05)as the humic-like compositions(peak A,M and C)decrease after DOM incubation,suggesting incomplete degradation of refractory DOM from high-molecular to low-molecular weight compounds.The findings support the new notion of the continuous DOM biodegradation in a mode as“steps by steps”,contributing to a new understanding of carbon cycling for the UN Sustainable Development Goal.

Microbial degradation of various types of dissolved organic matter in aquatic ecosystems and its influencing factors

Interactions between chemodiverse dissolved organic matter(DOM)and biodiverse microbes are governed by a myriad of intrinsic and extrinsic factors which are not well understood.Here,we update and bridge the gap of this interdisciplinary theme comprehensively.At an ecosystem level,aquatic ecosystems dominated by algae-sourced DOM(e.g.,eutrophic lake or coastal upwelling areas)harbor more biolabile DOM,such as directly assimilable monomers and readily hydrolysable biopolymers.However,other ecosystems prevailed by DOM supply from soil and vascular plants(e.g.,river or wetland)have more biorefractory DOM,such as low molecular weight(LMW)residue of aliphatic C skeletons and geopolymers.A variety of heterotrophic bacteria,archaea,fungi,phagotrophic protists,and even photoautotrophic phytoplankton shows genomic and/or culturing experimental evidence of being able to process a diverse type of organics.The various biodegradable organics have different chemical structures and chemical bonds such as carbohydrates,amino acids,proteins,lignins,lipids,carboxylic acids,humic acids,hydrocarbons,and nanoplastics.Meanwhile,bio-production of metabolism intermediates and/or biorefractory organics(e.g.,carboxyl-rich alicyclic molecules,CRAM)is observed despite general decay of bulk dissolved organic carbon(DOC)during bioassay experiments.In particular,emerging evidence shows that archaea contribute significantly to biomass in the marine mesopelagic zone and subsurface environments and their abundance often increases with depth in sediments.Furthermore,not only intrinsic factors(e.g.,DOM composition and structure),but also extrinsic ones(e.g.,sunlight and dissolved oxygen)play important roles in interplays between DOM and microbes.

Simultaneous degradation of sulfadiazine and dissolved organic matter based on low-impact development facilities

Sulfadiazine(SD)is a common antibiotic administered to treat bacterial infections in livestock,and its fate andmigration are greatly affected by dissolved organicmatter(DOM).The soil infiltration system[a typical low-impact development(LID)facility]can significantly alterDOMproperties during runoff pollution,thus affecting the complexation of SDwithDOM.Here,the binding characteristics of different DOM components and SD in the soil infiltration system were explored using spectroscopic techniques(excitation–emission matrices,parallel factor analysis,and synchronous fluorescence spectroscopy).Combined with the weakening of DOM fluorescence intensity and 78.63%reduction in mean SD concentration following treatment,synchronous degradation may have occurred.The binding sequence of SD and DOM fluorophores was further explored using two-dimensional correlation spectroscopy.Effluent DOM showed greater sensitivity to SD and more binding sites than influent DOM.Moreover,hydrophobic protein-like substances exhibited higher log K_(M) values than other fluorescent components,indicating that protein-like components play significant roles in SD complexation.The soil percolation system improved the complexation stability and binding sequence of fulvic-like substances.Thus,SD–DOM can be intercepted and degraded using LID facilities to reduce the risk of SD in aquatic environments.

污水厂尾水补水对受纳水体氮磷形态与DOM时空分布特征的影响

城镇污水厂尾水水量稳定、水质可控,是补给河湖水系生态基流的可靠水源.为保障污水厂尾水补水安全,以合肥市王建沟为研究对象,分别于枯水期、丰水期开展污水厂尾水回补河道氮、磷形态及溶解性有机质(dissolved organic matter,DOM)的时空分布特征研究,探明污水厂尾水对回补河流的影响.结果表明:①王建沟经尾水补水后水质明显改善,补水河段污染物浓度空间上沿程上升,时间上水质标识指数特征表现为丰水期>枯水期,总氮(total nitrogen,TN)为主要污染因子.②尾水回补河道中氮形态以溶解态为主,主要存在形式为溶解态无机氮(dissolved inorganic nitrogen,DIN,占60.9%),且以硝态氮(NO_(3)^(−)-N)为主.除溶解态有机氮(dissolved organic nitrogen,DON)和亚硝态氮(NO2−-N)以外,其余形态氮浓度均表现为丰水期>枯水期.③磷主要以溶解态无机磷(dissolved inorganic phosphorus,DIP,占80.3%)为主,各形态磷浓度均表现为丰水期>枯水期.④枯、丰水期尾水回补河道DOM均以类腐殖质为主,占68%以上,DOM具有较强自生源、低腐殖化特征;同时,较枯水期而言,丰水期DOM结构更为复杂,平均相对分子质量和含量升高.研究显示:污水厂尾水回补河流尽管会导致氮、磷等污染负荷的输入,但在丰富河流水动力、生态基流保障、河流生态恢复等方面具有积极的效应;同时建议丰水期强化入河城市面源污染管控.