Antibiotics pose a huge risk to human health and the environment, and thus it is important to assess and control their ecological risks. To better understand the factors that regulate the spatiotemporal dynamics of antibiotics in the tidal reach of a coastal city, four investigations were conducted in May 2022 (spring), August 2022 (summer), November 2022 (autumn), and February 2023 (winter) in the tidal reach of the Minjiang River. The results showed that sulfonamides were detected extensively and frequently (88.9-100 %) in four seasons, with concentrations of not detected (ND)-121.10 ngL-1. In addition, significant changes occurred in the concentrations of tetracyclines and quinolones were identified over time. The presence of these substances was only detected in spring (66.7 %, ND-46.70 ngL-1; 11.1 %, ND-0.10 ngL-1), followed by the summer (100.0 %, 19.40-6694.20 ngL-1; 55.6 %, ND-12.30 ngL-1) and autumn (33.3 %, ND-17.20 ngL-1; 100.0 %, 3.25-16.20 ngL-1). The season with the ecological risk quotient was ranked as follows: summer (3.80) > autumn (1.54) > spring (0.19) > winter (0.16). Dam operations significantly affected the accumulation of antibiotics in front of the dam, particularly following prolonged water retention, where their accumulation increased sharply in the summer. The effects of tides depended mainly on the influence of the accumulation of fresh water or dilution of saline water. The salinity levels increased markedly, exceeding 4.42 ppt under low-brackish water conditions (initial salinity: 0-5 ppt) and 8.57 ppt under intermediate-brackish conditions (initial salinity: 5-18 ppt), suggesting dilution by tides, which resulted in a decline in the accumulation of antibiotics. Finally, fish farms were identified as the main source of antibiotics during the spring (67.3 %), summer (71.0 %) and autumn (31.2 %). The contribution rates of antibiotics fluctuated according to the cultivation patterns on the fish farms. Moreover, livestock and sewage plants were identified as two stable sources of antibiotic contamination throughout the year. Thus, this study elucidated the seasonal changes in antibiotics and their associated ecological risks in a coastal tidal reach, highlighting the combined effects of upstream regulated freshwater, downstream tides, and human activities.

The invasive species Spartina alterniflora plays a significant role in heavy metal accumulation in sedimentary environments, and its global risk level warrants attention. In this study, seven sediment cores were collected according to the S. alterniflora invasion stage. The potential ecological and health risk of four typical carcinogenic heavy metals (Cr, Ni, Co, and Cd) were assessed following S. alterniflora invasion using Monte Carlo simulation. Heavy metal concentrations were in the order of Cr > Ni > Co > Cd, exhibiting three distinct trends. Cr and Ni increased in the early invasion stages (S0-S3, ∼10 years), subsequently decreasing to below background levels. Co remained stable from S0 to S3, but subsequently sharply declined in later stages (S4-S6). In contrast, Cd decreased initially, followed by an increase. Of the total potential ecological risks of these four heavy metals, Cd accounted for between 96.8% and 99.2%. The lowest risk probability was observed after 6-8 years of invasion (S2). The health risks associated with these heavy metals were insignificant with regard to non-carcinogenic risks, and fell below a 16.7% probability of acceptable carcinogenic risks during all invasion stages. The carcinogenic risk was entirely attributable to Cd and Cr. The parameters demonstrating the greatest sensitivity to heavy metal variations for adults and children were body weight. This study revealed changes in four typical carcinogenic heavy metals and the associated risks following S. alterniflora invasion, providing crucial insights for facilitating heavy metal regulation in estuarine sediments.

Biochar is a potential additive that can improve anaerobic digestion (AD) of kitchen waste by facilitating direct interspecies electron transfer (DIET). However, little is known about the relationship between biochar dosage and inoculum-to-substrate ratio (ISR) in promoting AD of kitchen waste. Here, the methanogenic performance was tested under the conditions of different biochar dosages (5, 15, and 45 g/L) and ISRs (0.52, 0.26 and 0.13) using batch AD. The results showed that acidogenesis outperformed methanogenesis when ISR was reduced from 0.52 to 0.13. Although increasing biochar dosage significantly improved the methanogenic performance at each ISR, the regulatory ability of biochar on methanogenesis gradually decreased with the decline of ISR to 0.13. Microbial analysis revealed that altering ISR not only caused selective enrichments of the VFA-producers and DIET participants, but also changed methanogenesis from multiple methanogenic pathways to the DIET-based CO2 reduction pathway in the biochar-amended AD systems. The positive effects of biochar on methanogenesis at low ISRs might be mainly ascribed to the enhancement of DIET between Petrimonas and Methanosaeta. The findings offered an important guidance for using biochar to treat perishable organic wastes at different ISRs.

Hyperaccumulators harbor potentials for remediating rare earth elements (REEs)-contaminated soils. However, how they thrive in low-nutrient abandoned REEs mining sites is poorly understood. Three ferns (REEs-hyperaccumulators Dicranopteris pedata and Blechnum orientale, and non-hyperaccumulator Pteris vittata) along with their rhizosphere soils were collected to answer this question by comparing differences in soil nutrient levels, soil and plant REEs concentrations, and bacterial diversity, composition, and functions. Results observed lower soil pH (4.67-4.95 vs. 7.96), total carbon (TC) (0.35-0.62 vs. 2.84 g kg-1), total nitrogen (TN) (20-23 vs. 133 mg kg-1), and total phosphorus (TP) (81-91 vs. 133 mg kg-1) at sites Dp and Bo than site Pv. Hyperaccumulators efficiently extracted soil REEs and translocated them to fronds (up to 6897-7759 mg kg-1). Bacterial α diversity in three soils did not significantly vary. In contrast, bacterial composition at sites Dp and Bo was dominant by higher abundances of copiotrophic bacteria (18 % vs. 12 %, p_Actinomycetota; 3.3-8.3 % vs. 1.9 %, p_Bacteroidota; 8.3-14 % vs. 6.9 %, c_Gammaproteobacteria) and autotrophic bacteria (18 % vs. 13 %, p_Chloroflexota; 13 % vs. 8.6 %, p_Cyanobacteriota) when compared to site Pv. These bacteria likely acted as nutrient cyclers that promoted the growth of hyperaccumulators, based on functional predictions from DiTing analyses. This study provides new insights into nutrient recovery in abandoned REEs mining sites, offering strategies to reclaim degraded soils using phyto-microbial technology.

Dam regulation, a hydraulic engineering measure, has a significant impact on dissolved organic matter (DOM) which works as the carbon pool; however, no exact relationship has been established between alterations in water level, caused by the long-time regulation of dams, on the distribution of DOM fluorescence components in the upstream reservoir. Here, four sampling campaigns were conducted under both high- and low-water levels in Shuikou Reservoir, and parameters of water quality and hydrology were comprehensively determined and statistically analyzed. Utilizing perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy technology and Mantel tests, we have found a significant correlation between DOM fluorescence components and both basic water quality parameters and indicators of inorganic pollutants, particularly during low-water level periods. High water velocity increased dissolved oxygen (DO) concentration to quench DOM fluorescence during low-water level periods, while low DO levels were correlated with increased fluorescence during high-water level periods. Turbidity showed a positive relation to certain DOM components and significantly influenced the composition of DOM. The main components of DOM (fulvic-like, humic-like and tryptophan-like fluorophores) increased to varying degrees under high-water levels, while decreased under low-water levels. Hence, the increment of DOM component in high-water level periods was more considerable than that in low-water level periods. Furthermore, DOM in urban river reaches mainly came from terrestrial organic matters introduced by human activities, while DOM in certain river sections originated from endogenous sources, such as the accumulation of humic substances in aquaculture systems. This study provided supporting data and optimization ideas for predicting the migration and transformation of pollutants in rivers and managing dam gates scientifically.

Plant-derived phenolic compounds could regulate redox reactions due to their antioxidative properties. In this study, soils from coastal wetlands including bare flat (BF), cyperus(Cyperus malaccensis) (CY), reed (Phragmites australis) (RE), and mangrove(Kandelia obovata) (MA) in Minjiang estuary region were selected. Anaerobic microcosm incubation experiments were conducted to investigate the petroleum hydrocarbon (PH) degradation process through denitrification. In addition, effect of plant-derived antioxidants (carotenoids, anthocyanins, flavones, and phenolic acids) on the activity of denitrifying bacteria, enzymes, and genes were studied. The results showed that addition of NO3- significantly (p < 0.05) promoted PH degradation in BF, RE, and CY by 14.1 %-31.7 % while not influenced on PH degradation in MA. Bacteria that could degrade petroleum through denitrification (e.g., Burkholderia and Rhodococcus) showed much higher abundances in CY and RE than in MA. Antioxidants of cover plants showed large varieties with RE containing highest contents of carotenoids while MA containing highest contents of phenolic compounds (anthocyanins, flavones, and phenolic acids). These phenolic antioxidants significantly reduced the activity of NO3- and NO2- reductase and abundances of denitrification genes (nirK) and the inhibition effect was positively correlated to Trolox Equivalent Antioxidant Capacity (TEAC). Overall, our results demonstrate the key regulation role of plant-derived antioxidants in OC degradation in eutrophic wetlands.

Abstract Bermudagrass is a summer forage crop with high nitrogen (N) demand. Introducing winter cover crops may sustain bermudagrass yields with less fertilizer, reducing environmental N losses. Field trials and lab incubation were carried out to evaluate the effects of white clover (Trifolium repens L.) and ryegrass (Lolium multiflorum) as winter cover crops on soil N losses through runoff and nitrous oxide (N2O) emissions in a subtropical bermudagrass (Cynodon dactylon L.) pasture field. The 2‐year field experiment included five treatments: (1) no winter cover and N fertilization as a control (CLT), (2) white clover without N fertilization (WC) (where WC represents white clover), (3) white clover mixed with ryegrass without N fertilization (WCR), (4) white clover with half‐rate N at 112 kg N ha−1 year−1 (WC112N), and (5) no cover crop with full‐rate N 224 kg N ha−1 year−1 (224N). Results showed that without N fertilization, WC increased bermudagrass biomass by 38% compared to CLT, while WCR had a similar bermudagrass biomass yield to CLT. WC112N produced comparable bermudagrass biomass as 224N as well as reduced NH4+ and NO3− runoff loss by 30%–35% and 11%–24%, respectively, compared than 224N, due to decreased runoff volume. There was no difference in N2O emissions between 224N and WC112N. Laboratory incubation of white clover residue‐amended soil showed that nitrification inhibitors dicyandiamide and 3,4‐dimethylpyrazole phosphate lowered N2O emission significantly, with a maximum reduction of 77%–91%, while urease inhibitor N‐(n‐butyl) thiophosphoric triamide had no effect. Overall, clover incorporation during the winter season helps in developing a low‐N‐input pasture production system, and nitrification inhibitors could be applied to mitigate associated N2O losses from clover residue decomposition.

The Si/TiO 2 /Ag heterostructures with high SERS sensitivity were prepared by sol-gel and electrochemical selfassembly. The electromagnetic (EM) and charge transferring (CT) synergistic mechanism for SERS enhancement was explored by FDTD. The "localized interfacial effect (LIE)" of metal-semiconductor heterostructures can result in the CT between them and the charge carriers' redistribution, which can facilitate the probe molecules' adsorption and generate the 3D volume -enhancement of electromagnetic fields, therefore improve the SERS performance effectively. Furthermore, the morphology of Ag was flexibly regulated by changing the applied voltage, and the optimal SERS performance was achieved. With the R6G as a probe molecule, the ultra -low concentration of 10 -13 M can be detected. The EF is estimated to be about 1.75 x 10 11 , and the RSD is about 4.3 %. The photocatalytic effect of Si/TiO 2 /Ag heterostructure can realize the SERS substrates' UV self-cleaning and recyclable use with high stability.

Arsenic (As) species in groundwater pose a major global environmental concern. Bioremediation, as a detoxifying mechanism for As, holds considerable importance in addressing the As contamination. In the current study, the fungus Burkholderia cepacia (BK) was successfully immobilized to increase the elimination of As (III) and As(V) from aqueous solutions using reduced graphene oxide (rGO) produced using green tea extract (GT). The removal efficiency of BK alone for As (III) was only 48.87 %, and the composite rGO@BK can enhance the removal efficiency of As(III) by 11.3 %. In addition, the rGO@BK also enhances the removal efficiency of As(V), which the removal efficiency of As(V) can achieve to 79.04 %, 24.79 % increase compared to BK alone (54.25 %). Scanning electron microscopy (SEM) and scanning electron microscopy (CLSM) showed that the extracellular polymeric substances (EPS) were numerous and uniformly dispersed on the rGO surface, which also indicated that the BK was firmly bound to the surface. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses confirmed that EPS contains a significant number of functional groups, which are involved in As biosorption through complexation. Three-dimensional excitation-emission matrix (3D-EEM) analysis showed that 3D-EEM indicated that EPS mainly contained tryptophan and humic acid analogs, in which humic acid plays an important role in the redox reaction of arsenic. Electrochemical techniques confirm the function of rGO as a potential electron shuttler. Furthermore, rGO@BK showed significant removal efficiency of both As(III) (44.4 %) and As (V) (98.9 %) in groundwater, which indicate rGO@BK holds great potential in detoxification of As contamination.

Spartina alterniflora invasion is considered a critical event affecting sediment phosphorus (P) availability and stock. However, P retention and microbial phosphate solubilization in the sediments invaded with or without S. alterniflora have not been fully investigated. In this study, a sequential fractionation method and high-throughput sequencing were used to analyze P transformation and the underlying microbial mechanisms in the sediments of no plant (NP) zone, transition (T) zone, and plant (P) zone. Results showed that except for organic phosphate (OP), total phosphate (TP), inorganic phosphate (IP), and available phosphate (AP) all followed a significant decrease trend from the NP site to the T site, and to the P site. The vertical decrease of TP, IP, and AP was also observed with an increase in soil depth. Among the six IP fractions, Fe-P, Oc-P, and Ca10-P were the predominant forms, while the presence of S. alterniflora resulted in an obvious P depletion except for Ca8-P and Al-P. Although S. alterniflora invasion did not significantly alter the alpha diversity of phosphate-solubilizing bacteria (PSB) harboring phoD gene, several PSB belonging to p_Proteobacteria, p_Planctomycetes, and p_Cyanobacteriota showed close correlations with P speciation and IP fractions. Further correlation analysis revealed that the reduced soil pH, soil TN and soil EC, and the increased soil TOC mediated by the invasion of S. alterniflora also significantly correlated to these PSB. Overall, this study elucidates the linkage between PSB and P speciation and provides new insights into understanding P retention and microbial P transformation in the coastal sediment invaded by S. alterniflora.

Biofilters are the important source and sink of antibiotic resistance genes (ARGs) and antibiotic resistance bacteria (ARB) in the drinking water. Current studies generally ascribed the prevalence of BAR in biofilter from the perspective of gene behavior, i.e. horizontal gene transfer (HGT), little attentions have been paid on the ARGs carrier- ARB. In this study, we proposed the hypothesis that ARB participating in pollutant metabolism processes and becoming dominant is an important way for the enrichment of ARGs. To verify this, the antibiotic resistome and bacterial functional metabolic pathways of a sand filter was profiled using heterotrophic bacterial plate counting method (HPC), high-throughput qPCR, Illumina Hiseq sequencing and PICRUSt2 functional prediction. The results illustrated a significant leakage of ARB in the effluent of the sand filter with an average absolute abundance of approximately 102-103 CFU/mL. Further contribution analysis revealed that the dominant genera, such as Acinetobacter spp., Aeromonas spp., Elizabethkingia spp., and Bacillus spp., were primary ARGs hosts, conferring resistance to multiple antibiotics including sulfamethoxazole, tetracycline and β-lactams. Notably, these ARGs hosts were involved in nitrogen metabolism, including extracellular nitrate/nitrite transport and nitrite reduction, which are crucial in nitrification and denitrification in biofilters. For example, Acinetobacter spp., the dominant bacteria in the filter (relative abundance 69.97 %), contributed the majority of ARGs and 53.79 % of nitrite reduction function. That is, ARB can predominate by participating in the nitrogen metabolism pathways, facilitating the enrichment of ARGs. These findings provide insights into the stable presence of ARGs in biofilters from a functional metabolism perspective, offering a significant supplementary to the mechanisms of the emergence, maintenance, and transmission of BARin drinking water.

Rare earth elements (REEs) mining exerts adverse impacts on soil ecosystems. Attempts to recover REEscontaminated soils have been made through phytoremediation with Dicranopteris pedata. However, how it improves soil quality is still poorly understood. This study fully investigated the effects of D. pedata-aided phytoremediation on abandoned REEs mining sites, focusing on soil properties, REEs speciation, and microbial diversity. Results showed that D. pedata increased soil TC from 488 to 626 mg kg(-1), soil TN from 20.1 to 57.0 mg kg(-1), and soil TP from 232 to 259 mg kg(-1), while decreased concentrations of soil Fe, Mn, and REEs by 37 %, 62 %, and 43 %, respectively. The plant efficiently removed labile REEs and elevated non-labile fractions. Additionally, D. pedata increased microbial diversity and reshaped microbial composition, with microbial communities such as p_Chloroflexota and p_Acidobacteriota being decreased from 22-47 % to 17-27 % (p < 0.01), and p_Pseudomonadota, p_Acidobacteriota, p_GAL15, and p_Bacteroidota being increased from 0.25-16 % to 5.3-26 % (p < 0.01). Several communities belonging to these phyla significantly correlated to soil properties and metal concentrations, suggesting their roles in improving soil quality. This study provides new insights into soil quality improvement after D. pedata aided-phytoremediation and highlights the beneficial use of phytomicrobial technology for remediating abandoned REEs mining sites.

Mining activities can potentially release high levels of Pb(II) in acid mine drainage (AMD), which thereafter poses a significant threat to ecological security. In this study, green reduced graphene oxide/silver nanoparticles (rGO/Ag NPs) were successfully synthesized via a one-step approach using a green tea extract and subsequently used as a cost-effective absorbent to remove Pb(II) from AMD. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated that organic functional groups in the green tea extracts, such as C=O-C, CO, and CC, acted both as reductants and stabilizers in the synthesis of rGO/Ag NPs. In addition, the removal efficiency of Pb(II) by rGO/Ag NPs (84.2 %) was much better than either rGO (75.4 %) or Ag NPs (12.3 %) alone. Also, in real AMD, the distribution coefficient (Kd) of Pb(II) (4528 mL/g), was much higher than other heavy metal indicating the adsorbent had a high selective affinity for Pb(II). Interestingly, after five cycles of use, the removal efficiency of Pb(II) by rGO/Ag NPs from AMD actually increased from 46.4 to 65.2 % due to iron oxides (i.e., Fe2O3 and Fe3O4) being generated when rGO/Ag NPs was exposed to AMD. The removal of Pb(II) via adsorption on the rGO/Ag NPs surface involved formation of hexagonal rod-like precipitates. This work demonstrated the potential of rGO/Ag NPs to be continuously used for the removal of Pb(II) from AMD.

Antimony (Sb) in mine wastewater poses a serious threat to surrounding ecosystems. In this study, biosynthesized iron-manganese nanoparticles (Fe-Mn NPs) were devised to remove Sb species. The resultant removal efficiencies were 100% for Sb(III) and 82.6% for Sb(V) utilizing a Sb(III) and Sb(V) concentration of 1mg·L-1. To understand the removal process, Fe-Mn NPs before and after exposure to Sb species were characterized by various advanced techniques, which indicated that while both Sb(III) and Sb(V) were adsorbed onto the surface of Fe-Mn NPs, Sb(III) was also partly oxidized to Sb(V). Furthermore, removal of both Sb(III) and Sb(V) followed pseudo-second-order kinetics and best fit the Freundlich adsorption isotherm model, suggesting that the removal process involved non-homogeneous chemisorption. These studies provided the evidence for an adsorption and oxidation mechanism for Sb(III) removal and an adsorption-dominated mechanism for Sb(V) removal by Fe-Mn NPs. When the produced Fe-Mn NPs were applied to remove Sb from mine wastewater, 92.7% removal was attained, demonstrating the significant practical potential of these nanoparticles to Sb species from mine wastewaters. This study provides novel insights for future exploration for Sb removal from mine wastewaters.

Dissolved organic matter (DOM) is a heterogeneous mixture of dissolved material found ubiquitously in aquatic systems and dissolved organic nitrogen is one of its most important components. We hypothesised nitrogen species and salinity intrusions affect the DOM changes. Here, using the nitrogen rich Minjiang River as an easily accessible natural laboratory 3 field surveys with 9 sampling sites (S1-S9) were conducted in November 2018, April and August 2019. The excitation emission matrices (EEMs) of DOM were explored with parallel factor (PARAFAC) and cosine-histogram similarity analysis. Four indices including fluorescence index (FI), biological index (BIX), humification index (HIX) and the fluorescent DOM (FDOM) were calculated and the impact of physicochemical properties was assessed. The results suggested that the highest salinities of 6.15, 2.98 and 10.10, during each campaign corresponded to DTN concentrations of 119.29-240.71, 149.12-262.42 and 88.27-155.29 μmol·L-1, respectively. PARAFAC analysis revealed the presence of tyrosine-like proteins (C1), tryptophan-like proteins or a combination of the peak N and tryptophan-like fluorophore (C2) and the humic-like material (C3). The EEMs in the upstream reach (i.e. S1-S3) were complex with larger spectra ranges, higher intensities and similar similarity. Subsequently, the fluorescence intensity of three components decreased significantly with low similarity of EEMs (i.e. S4-S7). At the downstream, the fluorescence levels dispersed significantly and no obvious peaks were seen except in August. In addition, FI and HIX increased, while BIX and FDOM decreased from upstream to downstream. The salinity positively correlated with FI and HIX, and negatively related to BIX and FDOM. Besides, the elevated DTN had a significant effect on the DOM fluorescence indices. Altogether, salinity intrusion and elevated nitrogen are relevant for the distribution of the DOM, which is helpful for the water management tracing the DOM source according to the on-line monitoring of salinity and nitrogen in estuaries.

As one of the polycyclic aromatic hydrocarbons (PAHs), naphthalene is of serious environmental concern due to its carcinogenicity, persistence and refractory degradation. In this study, a new functional biomaterial based on Burkholderia cepacia (BK) immobilized on reduced graphene oxide (rGO) was prepared, resulting in the removal of 99.0% naphthalene within 48 h. This was better than the 67.3% for free BK and 55.6% for rGO alone. Various characterizations indicated that reduced graphene oxide-Burkholderia cepacia (rGO-BK) was successfully synthesized and secreted non-toxic and degradable surfactants which participated in the degradation of naphthalene. The adsorption kinetics and degradation kinetics conformed best to non-linear pseudo-second-order and pseudo-first-order kinetic models, respectively. Demonstrated in this work is that removing naphthalene by rGO-BK involved both chemically dominated adsorption and biodegradation. As well, GC-MS analysis revealed two things: firstly, that the degraded products of naphthalene were dibutyl phthalate, diethyl phthalate, phthalic acid, and benzoic acid; and secondly, two potentially viable biodegradation pathways of naphthalene by rGO-BK could be proposed. Finally, for practical application experiment, the rGO-BK was exposed to river water samples and generated 99% removal efficiency of naphthalene, so this study offers new insights into biomaterials that can remove naphthalene.

The widespread use of antibiotics, such as oxytetracycline (OTC) and levofloxacin (LEV), has led to dangerous levels of environmental contamination. In this study, functionalized iron/manganese nanoparticles (Fe/Mn NPs), which act as both adsorbent and Fenton catalyst, were green-synthesized using a reducing agent derived from a tea extract. The resulting pre-sorption/Fenton-like oxidation system effectively removed both OTC and LEV from the aqueous solution with adsorption capacities of Fe/Mn NPs for OTC and LEV of 58.8 and 192.3 mg center dot g(-1), respectively. In addition, Fe/Mn NPs also showed high catalytic activity, oxidizing more than 99.9 % of both OTC and LEV, while sodium persulfate (PDS) removed only 26.6 and 29.0 % of OTC and LEV, respectively. Mechanisms of PDS activation typically involve either catalyst-initiated or mediated electron transfer reactions. Fe/Mn NPs through heterogeneous catalytic and metal leaching-induced homogeneous Fenton reactions, which generated various reactive oxygen species (ROS) including O-1(2), center dot OH, SO4-center dot and center dot O-2(-). Characterization of Fe/Mn NPs before and after reaction, and the identification of specific OTC and LEV degradation products by LC-MS, helped to elucidate a potential degradation pathway, as well as the removal mechanism. Finally, the practicality of using this system for wastewater treatment was demonstrated using real wastewater samples indicating that the system has great potential for simultaneously degrading both OTC and LEV in contaminated wastewater. (c) 2022 Elsevier Inc. All rights reserved.

选取闽江感潮河段,进行 2018-2020 年连续 3 年枯水期溶解性有机物(DOM)监测实验,获取不同河段涨落潮 DOM 的三维荧光图谱,并对 DOM 荧光特征参数进行相关性和主成分分析(PCA),得到如下结果.1)研究区域三年枯水期的 DOM 由人为源腐植酸 C1(Ex/Em = 220～240 nm/330～370 nm)? 陆地源腐殖质 C2(Ex/Em =220～240 nm/405～445 nm)及游离氨基酸与蛋白质结合类物质 C3(Ex/Em = 255～285 nm/310～360 nm)组成.上游河流段 DOM 受水库调度和人为输入影响,中游河流段 DOM 与组分性质和内外源输入有关,下游河口段 DOM 则表现为外海稀释和污染阻滞两种作用特点.C1 为研究区域的特征污染物.2)荧光特征参数 FI,BIX 和 Fn(355)呈现逐年下降的趋势,HIX指数先降低后升高;沿水流方向,FI和HIX呈上升趋势,BIX 和 Fn(355)呈下降趋势,越接近河口水体,外源性和自生源特征越明显.3)相关性分析发现,研究区域 DOM 荧光特征参数可能受到盐度和溶解氧(DO)的影响,当下泄流量较大时,溶解性总氮(DTN)和溶解性总磷(DTP)也有较大的影响;PCA 结果显示,2020 年研究区域 DOM 荧光特征参数组成与 2018 和 2019 年有较大的差异,可能与 2020 年下泄流量较高有关.

Identifying the mixing processes of waters and currents in tidal reach is an important aspect of environmental management to protect freshwater resources and prevent water pollution. In this study, three field investigations conducted in a typical tidal reach in August, November and the following April focused on two isotopes (δD and δ18O) and salinity. A salinity-isotope conservative mixing model was established to differentiate water flows of the important control interface (CI) from freshwater, transition zone and saltwater end-members. Results suggested that the average δD and δ18O values during the ebb and flood tides depleted from August to November, then enriched significantly in the following April and were even higher than those in August. The δD and δ18O values in the saltwater zone enriched markedly compared with those in freshwater zone and transition zone due to the stronger evaporation occurring in the saltwater zone. Based on the revised model, the average contributions of freshwater end-member, transition zone end-member and saltwater end-member in three months were, respectively, 51.50 %, 36.93 % and 11.57 %. However, the contributions of freshwater and transition zones in April end-member were equivalent (47.45 % vs 44.31 %). Meanwhile the largest contribution of saltwater end-member was 20.56 % and occurred in August. The proportions of three end-members that contributed to CI changed with different evaporation scenarios and moisture sources of precipitation. Our research provides important information that furthers our understanding of the isotopes and their applications to environmental management in estuarine regions.