Soil microplastic contamination is an increasingly serious global environmental challenge with significant implications for soil health, ecosystem functioning, and potential human health risks. This study provides a comprehensive analysis of the spatial and temporal distribution patterns of soil microplastic pollution across different geographic regions. Data were synthesized from 94 published studies, encompassing 1 629 sampling sites collected between 2008 and 2022. The analysis revealed marked regional differences in microplastic abundance. Soils in China exhibited the highest pollution levels (mean: 3 486.0 items·kg-1), followed by EU countries (mean: 2 334.7 items·kg-1), while North America showed relatively lower concentrations (mean: 443.5 items·kg-1). Temporal trends indicated a significant increase in soil microplastic contamination since 2015, coinciding with the rapid global growth in plastic production, which surpassed 350 million tons annually. Land use assessments showed that forest and unused lands contained significantly higher concentrations of microplastics compared to agricultural and urban soils. This suggests complex pollution pathways that extend beyond direct human activities. Correlation analysis and XGBoost modeling identified agricultural and industrial activities as the primary drivers of soil microplastic accumulation, surpassing factors such as population density or general economic indicators in explanatory power. The study further underscores the critical importance of standardized detection methods, as analytical techniques significantly influence the reported levels of contamination. These findings offer essential insights for the development of targeted mitigation strategies and policy frameworks to address the escalating issue of soil microplastic pollution, highlighting the need for an integrated approach that simultaneously addresses economic development and environmental protection goals.

Tetrabromobisphenol S (TBBPS) is a widely used brominated flame retardant that has attracted environmental concern due to its abundant presence in water. The objective of this study is to systematically analyze the direct photolysis and degradation mechanisms of TBBPS in two different dissociation forms in water, as well as to evaluate their toxicological effects induced by •OH, 1O2, and •NO2 radicals. The degradation mechanism of TBBPS is investigated with density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, and the toxicity of the degradation products is assessed through toxicological studies. The results of the study indicate that the OH-addition and H-abstraction reactions are favorable pathways for •OH-induced TBBPS degradation. The H-abstraction reaction of TBBPS0 with •OH was more favorable than the •OH addition reaction. However, in the degradation of TBBPS−, the •OH addition reaction was favored over the H-abstraction reaction. Additionally, the indirect photolysis of TBBPS by 1O2 and •NO2 in water was found to be easier for TBBPS− compared to TBBPS0, with degradation mechanisms involving Br-substitution and NO2-addition reactions. The higher Ea values calculated indicate that the degradation of TBBPS by 1O2 and •NO2 in water has been a secondary reaction. The direct photolysis reaction pathway of TBBPS in water has involved the cleavage of the S1–C7 and S1–C16 bonds. For TBBPS0 in the S1/T1 states, the primary reaction pathway is the cleavage of the S1–C16 bond, while for TBBPS−, the primary reaction pathway is the cleavage of the S1–C7 bond. Furthermore, the computational toxicology results indicate a slight increase in the toxicity levels of most products, highlighting the significance of investigating the degradation byproducts of TBBPS in greater detail.

Florfenicol (FLO) is a widely used antibacterial drug, which is often detected in the environment. In this paper, the photolysis mechanism of FLO in water was investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The focus of the study is to elucidate the direct photolysis mechanism of FLO in the water environment and the indirect photolysis of free radicals (·OH, ·NO3, and ·SO4−) as active species. The effect of metal ions Ca2+/Mg2+/Zn2+ on the indirect photolysis was also investigated. The results show that the direct photolysis of FLO involves C–C/C–N/C–S bond cleavage, the C5–S7 bond cleavage is most likely to occur, and the C17–C18 cleavage reaction is not easy to occur during the direct photodegradation of FLO. The indirect photolysis of FLO is more likely to occur in the environment than direct photolysis. The main indirect photolysis involves OH-addition, NO3-addition, and SO4-addition on benzene ring. The order of difficulty in the indirect photolysis with ·OH is C2 > C3 > C4 > C5 > C6 > C1, Ca2+ can promote the indirect photolysis with ·OH, and Mg2+/Zn2+ has a dual effect on the indirect photolysis with ·OH. In other words, Mg2+ and Zn2+ can inhibit or promote the indirect photolysis with ·OH. These studies provide important information for theoretical research on the environmental behavior and degradation mechanism of drug molecules.

The frequent detection of pharmaceutical compounds in the environment has led to a growing awareness, which may pose a major threat to the aquatic environment. In this study, photodegradation (direct and indirect photolysis) of two different dissociation states of fluoxetine (FLU) was investigated in water, mainly including the determination of photolytic transition states and products, and the mechanisms of indirect photodegradation with center dot OH, CO3 *- and NO3 *. The main direct photolysis pathways are defluorination and C-C bond cleavage. In addition, the indirect photodegradation of FLU in water is mainly through the reactions with center dot OH and NO3 *, and the photodegradation reaction with CO3 *- is relatively difficult to occur in the water environment. Our results provide a theoretical basis for understanding the phototransformation process of FLU in the water environment and assessing its potential risk. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Daidzein (DAID), as a common phytoestrogen, is often detected in the environment. In this paper, the photodegradation mechanism and UV absorption spectra of three different dissociation forms of DAID in water were studied by density functional theory (DFT) and time-dependent density functional theory (TDDFT). The photodegradation mechanism includes direct photolysis and indirect photolysis by reacting with ·OH in water. The reaction types of indirect photolysis of DAID0 with ·OH are OH-addition and H-abstraction, and H-abstraction is more favorable than OH-addition. The indirect photolysis reaction type of DAID− and DAID2− with ·OH is OH-addition. The degree of difficulty in the reaction of the three dissociation forms of DAID in water with ·OH is: DAID0 < DAID− < DAID2−. Results have shown that DAID can undergo degradation and can be transformed by reacting with ·OH in water. In addition, the direct photolysis reaction is also considered in the excited state to reveal the mechanism of the photochemical reaction. The direct photolysis pathway of DAID in water is the cleavage of C–C bond and C–O bond, but the Ea values required for these reactions are higher than the Ea values for the indirect photolysis reactions, indicating that direct photolysis is not the main pathway of photodegradation. The method of quantum chemical calculation in this study is helpful to understand the photochemical transformation of DAID in water.

Bendazone (BNTE) is an herbicide and a highly concerned pollutant in aquatic environments. Understanding the photochemical behavior of BNTE in water is crucial for evaluating its photochemical conversion process in aquatic environments. This study analyzed the direct photolysis and indirect photolysis pathways of two dissociated forms of BNTE in water through density functional theory and time-dependent density functional theory method. The results show that the reaction types of indirect photolysis of BNTE with free radicals (•OH, •SO 4 − , and •CO 3 − ) are OH − addition, SO 4 − addition, and CO 3 − addition. In the process of indirect photolysis of BNTE and free radicals, the photolysis of •OH and BNTE was the easiest, followed by •SO 4 − . In addition, the active site of BNTE reacting with •OH is C8, and the active site of BNTE reacting with •SO 4 − is C10. However, the photolysis effect of •CO 3 − on BNTE is very small, indicating that •CO 3 − in water plays a secondary role in the indirect photolysis of BNTE. In the direct photolysis of BNTE, N1–C6 bond breaking is difficult to occur spontaneously in the environment due to its high endothermic property and energy barrier. The direct photolysis pathway of BNTE involves the break of the N1–S2/S2–N3/N3–C12 bond. In addition, the ecological toxicity evaluation showed that toxicity of most of the degradation products were reduced, but the toxicity level was still maintained at a harmful level. Our findings provide the photochemical fate of BNTE in aquatic environments and will help to more accurately understand their photochemical conversion mechanisms in the environment.

Citalopram (CIT) is a commonly prescribed medication for depression. However, the photodegradation mechanism of CIT has not yet been fully analyzed. Therefore, the photodegradation process of CIT in water is studied by density functional theory and time-dependent density functional theory. The calculated results show that during the indirect photodegradation process, the indirect photodegradation of CIT with ·OH occurs via OH-addition and F-substitution. The minimum activation energy of C10 site was 0.4 kcal/mol. All OH-addition and F-substitution reactions are exothermic. The reaction of 1O2 with CIT includes the substitution of 1O2 for F and an addition reaction at the C14 site. The Ea value of this process is 1.7 kcal/mol, which is the lowest activation energy required for the reaction of 1O2 with CIT. C–C/C–N/C–F cleavage is involved in the direct photodegradation process. In the direct photodegradation of CIT, the activation energy of the C7-C16 cleavage reaction was the lowest, which was 12.5 kcal/mol. Analysis of the Ea values found that OH-addition and F-substitution, the substitution of 1O2 for F and addition at the C14 site, as well as the cleavage reactions of C6–F/C7–C16/C17–C18/C18–N/C19–N/C20–N are the main pathways of photodegradation of CIT.

Paroxetine (abbreviated as PXT) has been widely used as one of the standard antidepressants for the treatment of depression. PXT has been detected in the aqueous environment. However, the photodegradation mechanism of PXT remains unclear. The present study aimed to use density functional theory and time-dependent density functional theory to study the photodegradation process of two dissociated forms of PXT in water. The main mechanisms include direct and indirect photodegradation via reaction with ·OH and 1O2 and photodegradation mediated by the metal ion Mg2+. Based on the calculations, PXT and PXT-Mg2+ complexes in water are photodegraded mainly indirectly and directly. It was found that PXT and PXT-Mg2+ complexes were photodegraded by H-abstraction, OH-addition and F-substitution. The main reaction of PXT indirect photolysis is OH-addition reaction, while the main reaction of PXT0-Mg2+ complex is H-abstraction. All the reaction pathways of H-abstraction, OH-addition and F-substitution are exothermic. PXT0 reacts more readily with ·OH or 1O2 in water than PXT+. However, the higher activation energy of PXT with 1O2 indicates that the 1O2 reaction plays a minor role in the photodegradation pathway. The direct photolysis process of PXT includes ether bond cleavage, defluorination, and dioxolane ring-opening reaction. In the PXT-Mg2+ complex, the direct photolysis process occurs via a dioxolane ring opening. Additionally, Mg2+ in water has a dual effect on the direct and indirect photolysis of PXT. In other words, Mg2+ can inhibit or promote their photolytic reactions. Overall, PXT in natural water mainly undergo direct and indirect photolysis reactions with ·OH. The main products include direct photodegradation products, hydroxyl addition products and F-substitution products. These findings provide critical information for predicting the environmental behavior and transformation of antidepressants.

Ketamine (KET) is a common psychoactive substance, but its photochemical transformation mechanism in aqueous environment has not been elucidated. Density functional theory and time-dependent density functional theory were used to investigate the photodegradation process of KET in water. The calculation results show that during direct photodegradation: The photodegradation reaction of KET in the S-1 state is the cleavage of the nitrogen atom connected to the cyclohexanone group and the methyl bond; KET in the T-1 state can be photo-dechlorinated. During indirect photodegradation: Electron rearrangement occurs after the reaction of KET with fluorenone (FL), thereby sensitizing and degrading KET. Cleavage of nitrogen and methyl bonds; photo-dechlorination and FL degradation of KET are the main reactions during photodegradation.

Sertraline (SER) is widely used to treat depression and related disorders. Despite several studies on the environmental photochemical behavior of SER, its photodegradation mechanism remains largely unknown. Accordingly, in this study, the direct photodegradation of SER in water and indirect photodegradation of SER by·OH and 1O2 in water were studied using density functional theory and time-dependent density functional theory. The results indicated that, for indirect photodegradation, the reaction of SER with·OH proceeds through the addition of hydroxyl groups and Cl substitution, which are exothermic reactions in all pathways, and that 1O2 reacts with SER by substituting Cl on the benzene ring. The direct photodegradation of SER involves dechlorination and cleavage of C8–C9/C7–N/C17–N. The cleavage of C–Cl bonds is indicated in the geometry of SER optimized by the first excited triplet state. The higher Ea values and endothermicity of the pathway indicate that cleavage of C8–C9/C17–N and the substitution of Cl by 1O2 are not the main photodegradation pathways. The·OH addition product,·OH substitution product, C7–N cleavage product, and dechlorination product are the main endpoints of SER photodegradation. These findings provide sufficient information on the degradation of SER in water that may be applied to its removal from the environment.

As the derivatives and structural analogs of polybrominated diphenyl ethers (PBDEs), hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) have attracted increasing concern. However, knowledge of the photochemical behaviors of OH-PBDEs and MeO-PBDEs in water is limited. Here, we used density functional theory and time-dependent density functional theory to examine the structure-related photochemical properties of OH-PBDEs and MeO-PBDEs in water and the effects of metal ions as environmental factors. Eight 6-OH-PBDEs with 1–8 bromine substituents and eight 6-MeO-PBDEs with 1–8 bromine substituents were selected for this study. The optimized geometries of the selected congeners and their complexes with metals in the lowest excited triplet state (T1) showed that one C–Br bond moderately or significantly elongated. The elongated C–Br bond in the T1 state was shown in the ortho-position for the 6-OH-PBDE congeners and the ortho-position or the meta-position for the 6-MeO-PBDE congeners. For the selected congeners, there were significant positive linear correlations between the number of bromine atoms (NBr) and the calculated average atomic charge of bromine and maximum electronic absorbance wavelength (λmax), and a negative linear correlation between the NBr and average bond dissociation energy of C–O bonds (BDEC–O). The photoreactivities of the 6-OH-PBDEs and 6-MeO-PBDEs increased with an increase in the bromination degree with or without metal ions. The calculated average atomic charge of bromine and BDEC–O of the complexes with Mg2+/Zn2+ was higher and lower than those of the corresponding monomers, respectively, indicating that the presence of Mg2+/Zn2+ increased the photoreactivity (debromination and dissociation of C–O bond) of the selected 6-OH-PBDEs and 6-MeO-PBDEs. The effects of the coordination of Mg2+/Zn2+ may be overestimated due to their missing explicit solvation shell. These results provide vital insight into the photochemical properties of OH-PBDEs and MeO-PBDEs in water.

为揭示江苏克氏原螯虾养殖环境中抗生素的分布特征和污染现状,利用超高效液相色谱-串联质谱法(UPLC-MS/MS)调查浦口和盱眙两个地区4个典型养殖塘水和沉积物中抗生素的残留情况.共检出14种抗生素(包括4种大环内酯类、2种四环素类、4种喹诺酮类和4种磺胺类),除浦口两养殖塘水体中的CTC HCL、OFL和AZI(浓度分别为16.528～57.140 ng·L-1和9.803～47.400 ng·L-1),其他抗生素均以低浓度存在.抗生素浓度与水质指标的相关性分析结果表明,抗生素在水环境中的降解可能受水体富营养化、有机污染程度等水质状况的影响.基于RQs值对养殖环境中的抗生素进行风险评估,它们对生态系统中浮游动物的生长基本不会造成威胁;对藻类等浮游植物而言,浦口养殖水体中部分大环内酯类(SP、CTM)和喹诺酮类(OFL)抗生素具有中高度风险(0.161≤RQs≤2.92),盱眙养殖环境中目标抗生素生态风险较低(RQs≤0.181).研究表明,江苏(特别是盱眙)克氏原螯虾养殖水体中抗生素污染水平相对较低,但仍存在一定的生态风险.建议采取全面的抗生素控制措施,以保护水产养殖生态系统的健康.

Herein we systematically examined the roles of water chemistry (pH, dissolved organic carbon (DOC), and divalent cations) and particle surface functionality that control the aqueous stability, aggregation, and toxicity of engineered nanoplastic particles in simulated natural environmental conditions. Model polystyrene latex nanoparticles (PLNPs) with three different functional groups, namely unmodified (uPLNPs), amine-modified (aPLNPs), and carboxyl-modified (cPLNPs), were investigated. Results indicate that the presence of only DOC increased the surface charge and exhibited negligible effects on the size distribution of the PLNPs in aqueous suspensions. The presence of the divalent cations (Ca2+ and Mg2+) was observed to decrease the surface charge and increase the size of the PLNPs. The coexistence of DOC and the divalent cations enhanced the extent of aggregation of the PLNPs in the water columns. The surface modification and pH were sensitive factors influencing the stability of PLNPs during long-term suspension when DOC and the divalent cations coexisted. Direct visual further testified the conclusions on the combined effects of solution and surface chemistry parameters. Furthermore, in situ transmission electron microscope observations revealed that the enhancement of PLNP aggregation in the presence of DOC and the divalent cation was caused by bridge formation. Toxicity test indicated the PLNPs exhibited acute toxicity and physical damage to Daphnia magna. The more complex the solution conditions, the more toxicity the aPLNPs and cPLNPs. Analysis of mode of toxic action implied that the PLNPs mainly caused the accumulation of oxidative damage to the gut of D. magna.

Joint biomarker responses, oxidative stress and membrane systems, were determined for nano-metal-oxides (nMeO, i.e., nCeO2, nMgO, and nFe3O4) and sulfadiazine (SDZ) exposed at relevant low concentrations to two freshwater microalgae Scenedesmus obliquus and Chlorella pyrenoidosa. The impacts of dissolved organic matter (DOM) on the joint biomarker responses were also investigated. Results indicated that the presence of SDZ significantly decreased the level of intercellular reactive oxygen species (ROS) in the algal cells exposed to each nMeO. Reduction of cell membrane permeability (CMP) and mitochondrial membrane potential (MMP) in the algal cells was observed when the algae were exposed to the mixture of SDZ and the nMeO. The degree of reduction of the ROS level, CMP, and MMP significantly went down with the addition of DOM to a certain extent. Changes in cellular oxidative stress and membrane function depended on the types of both nMeO and algal species. This contribution provides an insight into the hazard assessment of a mixture consisting of emerging contaminants and DOM, as they can coexist in the aquatic environment.

Aquaculture has attracted significant attention as an environmental gateway to the development of antibiotic resistance. The industry of Chinese mitten crab Eriocheir sinensis contributes significantly to the freshwater aquaculture industry in China. However, the situation of antibiotic resistance in the E. sinensis aquaculture environment is not known. In this study, high-throughput sequencing based metagenomic approaches were used to comprehensively investigate the structure of bacterial communities, the abundance and diversity of antibiotic resistance genes (ARGs), as well as mobile genetic elements (MGEs) in three E. sinensis aquaculture ponds in Jiangsu Province, China. The dominant phyla were Proteobacteria, Actinobacteria, and Bacteroidetes in water samples and Proteobacteria, Chloroflexi, Verrucomicrobia, and Bacteroidetes in sediment samples. Bacitracin and multidrug were predominant ARG types in water and sediment samples, respectively. There was a significant correlation between MGEs and ARGs. In particular, plasmids were the most abundant MGEs and strongly correlated with ARGs. This is the first study of antibiotic resistome that uses metagenomic approaches in the E. sinensis aquaculture environment. The results indicate that the opportunistic pathogens may acquire ARGs via horizontal gene transfer, intensifying the potential risk to human health.

The importance of attention to unravel the interaction of nano-plastic particles (NPs) with natural acidic organic polymer (NAOP) in freshwater environment should not be neglected. However, toxicological data available for the interaction between NPs and NAOP remain limited. Here, we investigate the toxicological effects of three model polystyrene (PS) NPs with different functional groups (unmodified, amino- and carboxyl-modified PS NPs) on two freshwater organisms of different trophic levels (Scenedesmus obliquus and Danio rerio) in the absence and presence of two classes of NAOP, namely fulvic acid and humic acid. The NAOP interaction with the NPs is shown to alter oxidative stress and disturb membrane function in S. obliquus cells to a certain extent. Combined oxidative stress responses to the NPs and NAOP in D. rerio as a function of their mixture levels showed inhibition, alleviation, and reinforce. Changes in cellular oxidative stress and membrane function depended on the concentration and types of both NPs and NAOP. Furthermore, the characterization parameters of the NPs were important for the explanation of the ecotoxicological mechanism of the NPs in the presence of NAOP. Our findings emphasized the critical role of NAOP in the fate and toxicity of plastic particles in freshwater environment.

Tetrabromobisphenol A (TBBPA) is the most widely used commercial brominated flame retardant. However, the mechanisms underlying the photodegradation of TBBPA remain unclear. Here we use density functional theory and time-dependent density functional theory to examine the photodegradation of the two species of TBBPA in water: TBBPA (neutral form) and TBBPA- (anionic form). The study includes direct photodegradation and indirect photodegradation of TBBPA with ·OH and 1O2. The results of the calculations indicate that indirect photodegradation of TBBPA and TBBPA- with ·OH occurs via OH-addition and Br-substitution. All of the OH-addition and Br-substitution pathways are exothermic. Indirect photodegradation of TBBPA and TBBPA- by 1O2 proceeds via H abstraction by 1O2.Ea was higher for H abstraction of TBBPA than H abstraction of TBBPA-. The mechanisms for the direct photodegradation of TBBPA and TBBPA- include debromination, C1C7/C7C13 cleavage, and cyclization. CBr cleavage was observed in the optimized geometries of TBBPA and TBBPA- at the lowest excited triplet state. However, high Ea values and an endothermic nature indicated that C1C7/C7C13 cleavage and cyclization reactions were not the main pathways. OH-adducts, Br-substitution products, H-abstraction (by 1O2) products, and debromination products were the main products of photodegradation of TBBPA. These findings provide useful information for risk assessment and pollution control of brominated flame retardants.

为评价江苏典型中华绒螯蟹(Eriocheir sinensis)养殖区抗生素污染水平和生态风险,利用超高效液相色谱-串联质谱仪(UPLC-MS/MS)分别检测了江苏高淳和金坛4个中华绒螯蟹养殖塘水体和沉积物中大环内酯类、四环素类、β-内酰胺类、喹诺酮类和磺胺类5类抗生素水平.结果表明:研究区中华绒螯蟹养殖水体中均存在一定程度的抗生素污染.高淳养殖水体中污染物主要为喹诺酮类、四环素类和大环内酯类抗生素,而金坛养殖水体中5类抗生素分布均匀.4个养殖塘中,养殖塘GC2水体中抗生素检出浓度最高,主要包括盐酸金霉素(241.99 ng·L-1)、螺旋霉素(198.53 ng·L-1)、环丙沙星(168.81 ng·L-1)、沙拉沙星(165.40 ng·L-1)、诺氟沙星(126.17 ng·L-1)、恩诺沙星(117.42 ng·L-1)和依诺沙星(103.08 ng·L-1);而沉积物中抗生素含量均较低.水体抗生素浓度与对应的水质指标的相关性分析结果显示,水体克林霉素、强力霉素和青霉素G钠盐浓度与CODMn呈显著相关.采用风险商值法对水体残留抗生素进行风险评估,结果表明江苏高淳和金坛中华绒螯蟹养殖环境中残留抗生素具有一定的生态风险,尤其是养殖塘GC2水体中大环内酯类和喹诺酮类抗生素对相应敏感物种的风险较高,直接影响藻类等浮游植物的生长.建议控制该类抗生素在养殖过程中的使用,以降低生态风险.

Elucidation of the mechanisms underlying the effects of different dissociated forms and metal ion complexation on the photochemical behavior of antibiotics in aqueous media is a key problem and requires further research. We examined the mechanism of the direct photolysis of enrofloxacin (ENRO) in different dissociated forms in water and the impact of metal ions (Mg2+) on the photolysis of ENRO using density functional theory and time-dependent density functional theory. The results showed that different dissociated forms of ENRO exhibited diverse maximum electronic absorbance wavelengths (ENRO3+ (264 nm) < ENRO− (278 nm) < ENRO0 (280 nm) < ENRO2+ (282 nm) < ENRO+ (306 nm)). The calculations of the reaction pathways and activation energies (Ea) in the photolysis of ENRO0/ENRO+/ENRO− showed that defluorination was the main reaction pathway. The removal of cyclopropane was the main reaction pathway for the direct photolysis of ENRO2+/ENRO3+. Furthermore, the presence of Mg2+ was observed to change the order of the maximum electronic absorbance wavelengths and increases the intensities of the ENRO absorbance peaks. Calculations of the photolysis reaction pathways showed that the presence of Mg2+ increased the Ea for the most direct photolysis pathways of ENRO, while its presence decreased the Ea for several partial direct photolysis pathways such as the pathway in which the piperazine ring moiety of ENRO0/ENRO3+ is damaged and the pathway in which cyclopropane is released from ENRO3+. The findings on the photolysis behavior of ENRO in water system have provided useful information on the risk assessment of antibiotics.

Concomitant releases of various engineered nanoparticles (NPs) into the environment have resulted in concerns regarding their combined toxicity to aquatic organisms. It is however, still elusive to distinguish the contribution to toxicity of components in NP mixtures. In the present study, we quantitatively evaluated the relative contribution of NPs in their particulate form (NP(particle)) and of dissolved ions released from NPs (NP(ion)) to the combined toxicity of binary mixtures of ZnO NPs and graphene oxide nanoplatelets (GO NPs) to three aquatic organisms of different trophic levels, including an alga species (Scenedesmus obliquus), a cladoceran species (Daphnia magna), and a freshwater fish larva (Danio rerio). Our results revealed that the effects of ZnO NPs and GO NPs were additive to S. obliquus and D. magna but antagonistic to D. rerio. The relative contribution to toxicity (RCT) of the mixture components to S. obliquus decreased in the order of RCTGO NP(particle) >RCTZnO NP(particle)>RCTZnO NP(ion), while the RCT of the mixture components to D. magna and D. rerio decreased in the order of RCTZnO NP(particle)>RCTGO NP(particle)>RCTZnO NP(ion). This finding also implies that the suspended particles rather than the dissolved Zn-ions dictated the combined toxicity of binary mixtures of ZnO NPs and GO NPs to the aquatic organisms of different trophic level. The alleviation of the contribution to toxicity of the ionic form of ZnO NPs was caused by the adsorption of the dissolved ions on GO NPs. Furthermore, the ZnO NP(particle) and GO NP(particle) displayed a different contribution to the observed mixture toxicity, dependent on the trophic level of the aquatic organisms tested. The difference of the contributions between the two particulate forms was mainly associated with differences in the intracellular accumulation of reactive oxygen species. Our findings highlight the important role of particles in the ecological impact of multi-nanomaterial systems.