Identification of toxicity factors and causal analysis of toxicity in surface sediments from Liaohe river basin, Northeast China using an effect guidance strategy.

Sediments play a pivotal role in maintaining the aquatic ecological status of rivers. However, the determination of the key toxicants that consider the combined effects of all sediment-related contaminants are still challenging and necessary for an appropriate sediment risk assessment. The effects of sediments on aquatic organisms have been reported in Liaohe River, but their key toxicity factors are not well known. To determine the key toxicity factors, twenty-six surface sediment samples from Liaohe River tributaries in Northeast China were collected. Acute toxicity test of midge larvae results showed that 6 of 26 tributaries had obvious toxic effects, with survival rates of 37%-57% (p < 0.05). The masking test showed that the main pollutants in the surface sediments of T7 and T16 were metals, that of T8 was an organic pollutant, those of T19 and T26 were organic pollutants and ammonia, and those of T17 were heavy metal and ammonia. Chemical analysis showed that the relatively high concentrations of ammonia were only presented in surface sediments of T17, T19, and T26, with PTU of 1.5, 1.2 and 1.1, respectively, whereas heavy metals were markedly high in surface sediments from T7 and T16, with PTU of 0.92 and 0.61, respectively. Interestingly, the observed toxicity in surface sediments agreed with the toxicity predicted by chemical analysis Moreover, the significant correlation between the survival and volume ratio of the sediment and overlying water confirmed ammonia nitrogen was key toxicity factor in T17, T19, and T26, whereas Cu was the key toxicity factor in T7 that cause the biological toxicity. In conclusion, the major toxic factors of ammonia and copper in the sediments were identified. Moreover, our study suggested that effect guidance strategy was an effective method for sediment quality assessment.

A review on China's constructed wetlands in recent three decades: Application and practice.

Constructed wetlands (CWs) have been introduced to and developed in China for environmental engineering over the most prosperous three decades (1990-2020). To study the origin, development process, and future trend of CWs, this review summarized a wide range of literatures between 1990 and 2020 by Chinese authors. Firstly, the publication number over years, research highlights, and the author contributions with the most published papers in this field were conducted through bibliometric analysis. Secondly, the most principal components of CWs, substrates and macrophytes were summarized and analyzed. Thirdly, the typical application cases from traditional CWs, pond systems to combined pond-wetland systems were presented. In China, CWs were predominately distributed in the east of the so-called 'Hu Huanyong Line'. Therefore CWs were limited by the socio-economic level and climatic conditions. It is unquestionable that the overall level of China's CWs has improved significantly, and one of the most prominent features has started towards the plural pattern development. There has been a trend of large-scale or low-cost CW application in the recent years. However, lifecycle research and management are required for better strategies in the future.

High-resolution mapping of cis-regulatory variation in budding yeast.

Genetic variants affecting gene-expression levels are a major source of phenotypic variation. The approximate locations of these variants can be mapped as expression quantitative trait loci (eQTLs); however, a major limitation of eQTLs is their low resolution, which precludes investigation of the causal variants and their molecular mechanisms. Here we report RNA-seq and full genome sequences for 85 diverse isolates of the yeast Saccharomyces cerevisiae-including wild, domesticated, and human clinical strains-which allowed us to perform eQTL mapping with 50-fold higher resolution than previously possible. In addition to variants in promoters, we uncovered an important role for variants in 3'UTRs, especially those affecting binding of the PUF family of RNA-binding proteins. The eQTLs are predominantly under negative selection, particularly those affecting essential genes and conserved genes. However, applying the sign test for lineage-specific selection revealed the polygenic up-regulation of dozens of biofilm suppressor genes in strains isolated from human patients, consistent with the key role of biofilms in fungal pathogenicity. In addition, a single variant in the promoter of a biofilm suppressor, NIT3, showed the strongest genome-wide association with clinical origin. Altogether, our results demonstrate the power of high-resolution eQTL mapping in understanding the molecular mechanisms of regulatory variation, as well as the natural selection acting on this variation that drives adaptation to environments, ranging from laboratories to vineyards to the human body.

Dissecting the Genetic Basis of a Complex cis-Regulatory Adaptation.

Although single genes underlying several evolutionary adaptations have been identified, the genetic basis of complex, polygenic adaptations has been far more challenging to pinpoint. Here we report that the budding yeast Saccharomyces paradoxus has recently evolved resistance to citrinin, a naturally occurring mycotoxin. Applying a genome-wide test for selection on cis-regulation, we identified five genes involved in the citrinin response that are constitutively up-regulated in S. paradoxus. Four of these genes are necessary for resistance, and are also sufficient to increase the resistance of a sensitive strain when over-expressed. Moreover, cis-regulatory divergence in the promoters of these genes contributes to resistance, while exacting a cost in the absence of citrinin. Our results demonstrate how the subtle effects of individual regulatory elements can be combined, via natural selection, into a complex adaptation. Our approach can be applied to dissect the genetic basis of polygenic adaptations in a wide range of species.

The molecular mechanism of a cis-regulatory adaptation in yeast.

Despite recent advances in our ability to detect adaptive evolution involving the cis-regulation of gene expression, our knowledge of the molecular mechanisms underlying these adaptations has lagged far behind. Across all model organisms, the causal mutations have been discovered for only a handful of gene expression adaptations, and even for these, mechanistic details (e.g. the trans-regulatory factors involved) have not been determined. We previously reported a polygenic gene expression adaptation involving down-regulation of the ergosterol biosynthesis pathway in the budding yeast Saccharomyces cerevisiae. Here we investigate the molecular mechanism of a cis-acting mutation affecting a member of this pathway, ERG28. We show that the causal mutation is a two-base deletion in the promoter of ERG28 that strongly reduces the binding of two transcription factors, Sok2 and Mot3, thus abolishing their regulation of ERG28. This down-regulation increases resistance to a widely used antifungal drug targeting ergosterol, similar to mutations disrupting this pathway in clinical yeast isolates. The identification of the causal genetic variant revealed that the selection likely occurred after the deletion was already present at high frequency in the population, rather than when it was a new mutation. These results provide a detailed view of the molecular mechanism of a cis-regulatory adaptation, and underscore the importance of this view to our understanding of evolution at the molecular level.

Polygenic cis-regulatory adaptation in the evolution of yeast pathogenicity.

The acquisition of new genes, via horizontal transfer or gene duplication/diversification, has been the dominant mechanism thus far implicated in the evolution of microbial pathogenicity. In contrast, the role of many other modes of evolution--such as changes in gene expression regulation-remains unknown. A transition to a pathogenic lifestyle has recently taken place in some lineages of the budding yeast Saccharomyces cerevisiae. Here we identify a module of physically interacting proteins involved in endocytosis that has experienced selective sweeps for multiple cis-regulatory mutations that down-regulate gene expression levels in a pathogenic yeast. To test if these adaptations affect virulence, we created a panel of single-allele knockout strains whose hemizygous state mimics the genes' adaptive down-regulations, and measured their virulence in a mammalian host. Despite having no growth advantage in standard laboratory conditions, nearly all of the strains were more virulent than their wild-type progenitor, suggesting that these adaptations likely played a role in the evolution of pathogenicity. Furthermore, genetic variants at these loci were associated with clinical origin across 88 diverse yeast strains, suggesting the adaptations may have contributed to the virulence of a wide range of clinical isolates. We also detected pleiotropic effects of these adaptations on a wide range of morphological traits, which appear to have been mitigated by compensatory mutations at other loci. These results suggest that cis-regulatory adaptation can occur at the level of physically interacting modules and that one such polygenic adaptation led to increased virulence during the evolution of a pathogenic yeast.

Systematic detection of polygenic cis-regulatory evolution.

The idea that most morphological adaptations can be attributed to changes in the cis-regulation of gene expression levels has been gaining increasing acceptance, despite the fact that only a handful of such cases have so far been demonstrated. Moreover, because each of these cases involves only one gene, we lack any understanding of how natural selection may act on cis-regulation across entire pathways or networks. Here we apply a genome-wide test for selection on cis-regulation to two subspecies of the mouse Mus musculus. We find evidence for lineage-specific selection at over 100 genes involved in diverse processes such as growth, locomotion, and memory. These gene sets implicate candidate genes that are supported by both quantitative trait loci and a validated causality-testing framework, and they predict a number of phenotypic differences, which we confirm in all four cases tested. Our results suggest that gene expression adaptation is widespread and that these adaptations can be highly polygenic, involving cis-regulatory changes at numerous functionally related genes. These coordinated adaptations may contribute to divergence in a wide range of morphological, physiological, and behavioral phenotypes.

Calibration of Yld2000-2D Anisotropy Yield Criterion with Traditional Testing and Inverse Identification Strategies.

In order to improve predictive capabilities of numerical simulations, Yld2000-2D yield criterion is used to model the plastic anisotropic behaviors of AA5086 sheets. The parameters of Yld2000-2D yield criterion are identified based on the traditional testing strategy and the inverse identification strategy, respectively. The traditional testing strategy considers uniaxial and equi-biaxial tensile tests. The inverse identification strategy relies on the finite element model update (FEMU) method that couples with a biaxial tensile test using a dedicated cruciform specimen or the Pottier bulging test. The identified parameters are preliminarily evaluated by comparing predicted and experimental yield stresses, r-values, and yield loci. Then, the deep drawing test and simulations are performed. The identified parameter sets of Yld2000-2D yield criterion are further evaluated in terms of practical forming by comparing the predicted earing profile height with the experimental results. The results show that the inverse identification strategy can be an effective alternative to identify the parameters of Yld2000-2D yield criterion, and a well-designed heterogeneous test could lead to a better identification result.

Control of evolution of porous copper-based metal-organic materials for electroreduction of CO2 to multi-carbon products.

Electrochemcial reduction of CO2 to multi-carbon (C2+) products is an important but challenging task. Here, we report the control of structural evolution of two porous Cu(ii)-based materials (HKUST-1 and CuMOP, MOP = metal-organic polyhedra) under electrochemical conditions by adsorption of 7,7,8,8-tetracyanoquinodimethane (TNCQ) as an additional electron acceptor. The formation of Cu(i) and Cu(0) species during the structural evolution has been confirmed and analysed by powder X-ray diffraction, and by EPR, Raman, XPS, IR and UV-vis spectroscopies. An electrode decorated with evolved TCNQ@CuMOP shows a selectivity of 68% for C2+ products with a total current density of 268 mA cm-2 and faradaic efficiency of 37% for electrochemcial reduction of CO2 in 1 M aqueous KOH electrolyte at -2.27 V vs. RHE (reversible hydrogen electrode). In situ electron paramagnetic resonance spectroscopy reveals the presence of carbon-centred radicals as key reaction intermediates. This study demonstrates the positive impact of additional electron acceptors on the structural evolution of Cu(ii)-based porous materials to promote the electroreduction of CO2 to C2+ products.

Proton sponge-functionalized silica as high performance adsorbents for solid-phase extraction of trace perfluoroalkyl sulfonates in the environmental water samples and their direct analysis by MALDI-TOF-MS.

1,8-Bis(dimethylamino)naphthalene (DMAN), a classical 'proton sponge', was functionalized on silica particles as a novel solid-phase extraction (SPE) adsorbent (DMAN@silica) for extracting perfluoroalkyl sulfonates (PFSs). High reproducibility and excellent extraction capability for PFSs were obtained in a wide pH range (3.0~8.5). The adsorbed PFSs on DMAN@silica sorbents could be efficiently eluted by 1,8-bis(tetramethylguanidino)naphthalene (TMGN) solution which is a proton sponge with higher proton affinity than DMAN. The elution could be directly analyzed by MALDI-TOF-MS using TMGN as matrix. Clear mass spectra for the PFSs were obtained due to no matrix ions interference observed. Furthermore, a novel strategy based on the DMAN@silica-SPE enrichment, followed by MALDI-TOF-MS analysis, was proposed and applied for PFSs quantification in environmental water samples. The calibration curves of each of the target analytes showed a wide linear dynamic range of response (0.1-10 ng L(-1) for perfluorooctane sulfonate (PFOS), perfluorohexyl sulfonate (PFHxS) and perfluorobutylsulfonate (PFBS)), which were over 2 orders of magnitude. The detection limits for PFOS, PFHxS, and PFBS were 0.021, 0.016, and 0.013 ng L(-1), respectively (S/N = 3). Recoveries of PFOS, PFHxS, and PFBS are in the ranges of 92-104%, 95-102%, and 98-109% for spiked river water samples. These results indicated that the prepared DMAN@silica adsorbents could efficiently enrich PFSs and that the proposed method is reliable.

Occurrence and fate of steroid estrogens in the largest wastewater treatment plant in Beijing, China.

Concern over steroid estrogens has increased rapidly in recent years due to their adverse health effects. Effluent discharge from wastewater treatment plants (WWTPs) is the main pollutant source for environmental water. To understand the pollutant level and fate of steroid estrogens in WWTPs, the occurrence of estrone (E1), 17-ß-estradiol (E2), estriol (E3), and 17-ß-ethinylestradiol (EE2) was investigated in the Gaobeidian WWTP in Beijing, China. Water samples from influent as well as effluent from second sedimentation tanks and advanced treatment processes were taken monthly during 2006 to 2007. In influent, steroid estrogen concentrations varied from 11.6 to 1.1 × 10(2) ng/l, 3.7 to 1.4 × 10(2) ng/l, no detection (nd) to 7.6×10(2) ng/l and nd to 3.3 × 10(2) ng/l for E1, E2, E3, and EE2, respectively. Compared with documented values, the higher steroid estrogen concentrations in the WWTP influent may be due to higher population density, higher birthrate, less dilution, and different sampling time. Results revealed that a municipal WWTP with an activated sludge system incorporating anaerobic, anoxic, and aerobic processes could eliminate natural and synthetic estrogens effectively. The mean elimination efficiencies were 83.2%, 96.4%, 98.8%, and 93.0% for E1, E2, E3, and EE2, respectively. The major removal mechanism for natural estrogens and synthetic estrogen EE2 were biodegradation and sorption on the basis of mass balance in water, suspension particles, and sludge. In the WWTP effluent, however, the highest concentrations of E1, E2, E3, and EE2 attained were 74.2, 3.9, 5.1, and 4.6 ng/l, respectively. This is concerning as residual steroid estrogens in WWTP effluent could lead to pollution of the receiving water. Advanced flocculation treatment was applied in the WWTP and transformed the residual estrogen conjugates to free species, which were reduced further by filtration with removal shifting from 32% to 57% for natural estrogen, although no EE2 was removed.

Occurrences of six steroid estrogens from different effluents in Beijing, China.

Concentration levels of six natural and anthropogenic origin steroid estrogens, namely, diethylstilbestrol (DES), estrone (E1), estradiol (E2), estriol (E3), ethinylestradiol (EE2), and estradiol-17-valerate (Ev), from different effluents in Beijing were assessed. Sampling sites include two wastewater treatment plants (WWTPs), a chemical plant, a hospital, a pharmaceutical factory, a hennery, and a fish pool. In general, concentrations of estrogens in the effluents varied from no detection (nd) to 11.1 ng/l, 0.7 to 1.2 × 10(3) ng/l, nd to 67.4 ng/l, nd to 4.1 × 10(3) ng/l, nd to 1.2 × 10(3) ng/l, and nd to 11.2 ng/l for DES, E1, E2, EE2, E3, and Ev, respectively. The concentration levels of steroid estrogens from different effluents decreased in the order of pharmaceutical factory and WWTP inlets > hospital > hennery > chemical factory > fish pool. This study indicated that natural estrogens E1, E2, and E3 and synthetic estrogen EE2 are the dominant steroid estrogens found in the different Beijing effluents. For source identification, an indicator (hE = E3/(E1 + E2 + E3)) was used to trace human estrogen excretion. Accordingly, hE in effluents from the hospital and WWTP inlets exceeded 0.4, while much smaller values were obtained for the other effluents. Human excretions were the major contributor of natural estrogens in municipal wastewater. Estimation results demonstrated that direct discharge was the major contributor of steroid estrogen pollution in receiving waters.

Synthesis of l-ascorbic acid-amino acid-norcantharidin conjugates and their biological activity evaluation in vitro.

Three components of L-ascorbic acid, amino acid and functionalized norcantharidins were constructed together in several steps to form 42 norcantharidin derivatives in a high yield. The structure of these synthesized l-ascorbic acid-amino acid-norcantharidin conjugates are determined by 1HNMR, 13CNMR and MS spectrum. The results showed that compounds 6e, 6g, 6j, 6l, 6m, 6b, 6e, 6i, and 6n showed high cytotoxicity to HepG2 and compounds 6b, 6e-g, 6l, 6n, 7b, 7d, 7h, 7i, 7n, 8g, 8i exhibited high cytotoxicity to SW480; Meanwhile, besides 6b, 6e, 6g, and 6k, the other compounds showed less toxic to LO2 at a concentration of 50 µg/mg after 72 h. Compound 6g can induce Mφ-type macrophages derived from mouse bone marrow to polarize to M1-type macrophages.

Exposure Risk of Global Surface O3 During the Boreal Spring Season.

Surface ozone (O3) is an oxidizing gaseous pollutant; long-term exposure to high O3 concentrations adversely affects human health. Based on daily surface O3 concentration data, the spatiotemporal characteristics of O3 concentration, exposure risks, and driving meteorological factors in 347 cities and 10 major countries (China, Japan, India, South Korea, the United States, Poland, Spain, Germany, France, and the United Kingdom) worldwide were analyzed using the MAKESENS model, Moran' I analysis, and Generalized additive model (GAM). The results indicated that: in the boreal spring season from 2015 to 2020, the global O3 concentration exhibited an increasing trend at a rate of 0.6 µg/m3/year because of the volatile organic compounds (VOCs) and NOx changes caused by human activities. Due to the lockdown policies after the outbreak of COVID-19, the average O3 concentration worldwide showed an inverted U-shaped growth during the study period, increasing from 21.9 µg/m3 in 2015 to 27.3 µg/m3 in 2019, and finally decreasing to 25.9 µg/m3 in 2020. According to exposure analytical methods, approximately 6.32% of the population (31.73 million people) in the major countries analyzed reside in rapidly increasing O3 concentrations. 6.53% of the population (32.75 million people) in the major countries were exposed to a low O3 concentration growth environment. Thus, the continuous increase of O3 concentration worldwide is an important factor leading to increasing threats to human health. Further we found that mean wind speed, maximum temperature, and relative humidity are the main factors that determine the change of O3 concentration. Our research results are of great significance to the continued implementation of strict air quality policies and prevention of population hazards. However, due to data limitations, this research can only provide general trends in O3 and human health, and more detailed research will be carried out in the follow-up. Supplementary Information: The online version contains supplementary material available at 10.1007/s12403-022-00463-7.

Improved ClickTags enable live-cell barcoding for highly multiplexed single cell sequencing.

Click chemistry-enabled DNA barcoding of cells provides a universal strategy for sample multiplexing in single-cell RNA-seq (scRNA-seq). However, current ClickTags are limited to fixed samples as they only label cells efficiently in methanol. Herein, we report the development of a new protocol for barcoding live cells with improved ClickTags. The optimized reactions barcoded live cells without perturbing their physiological states, which allowed sample multiplexing of live cells in scRNA-seq. The general applicability of this protocol is demonstrated in diversified types of samples, including murine and human primary samples. Up to 16 samples across these two species are successfully multiplexed and demultiplexed with high consistency. The wide applications of this method could help to increase throughput, reduce cost and remove the batch effect in scRNA-seq, which is especially valuable for studying clinical samples from a large cohort.

Kindlin-2 Mediates Lipopolysaccharide-Induced Acute Lung Injury Partially via Pyroptosis in Mice.

Acute lung injury (ALI) is characteristic of the wholesale destruction of the lung endothelial barrier, which results in protein-rich lung edema, influx of pro-inflammatory leukocytes, and intractable hypoxemia, contributing to high mortality. Kindlin-2 is involved in the process of tumor- and wound healing-associated inflammation. However, the effects of kindlin-2 on lipopolysaccharide (LPS)-induced ALI and its mechanisms remain unknown. In this study, we found that the concentration of kindlin-2 was elevated in the lungs of ALI mice. The specific deletion of kindlin-2 by kindlin-2 siRNA attenuated the severity of lung injury, which was demonstrated by the reduced number of pro-inflammatory cells in bronchoalveolar lavage fluid and lung wet/dry weight ratio, and ameliorated pathologic changes in the lungs of ALI mice. Furthermore, kindlin-2 siRNA decreased the mRNA levels of pro-inflammatory factors (IL-1ß, IL-6, and TNF-α) and the protein levels of pyroptosis-related proteins. In vitro studies confirmed that LPS + ATP promoted the expressions of pro-inflammatory factors and pyroptosis-related proteins, which was prevented by kindlin-2 siRNA pretreatment in endothelial cells (ECs). In conclusion, inhibition of kindlin-2 developes protective effects against LPS-induced ALI and the cytotoxicity of ECs, which may depend on blocking pyroptosis.

Evolution of bismuth-based metal-organic frameworks for efficient electroreduction of CO2.

Understanding the structural and chemical changes that reactive metal-organic frameworks (MOFs) undergo is crucial for the development of new efficient catalysts for electrochemical reduction of CO2. Here, we describe three Bi(iii) materials, MFM-220, MFM-221 and MFM-222, which are constructed from the same ligand (biphenyl-3,3',5,5'-tetracarboxylic acid) but which show distinct porosity with solvent-accessible voids of 49.6%, 33.6% and 0%, respectively. We report the first study of the impact of porosity of MOFs on their evolution as electrocatalysts. A Faradaic efficiency of 90.4% at -1.1 V vs. RHE (reversible hydrogen electrode) is observed for formate production over an electrode decorated with MFM-220-p, formed from MFM-220 on application of an external potential in the presence of 0.1 M KHCO3 electrolyte. In situ electron paramagnetic resonance spectroscopy confirms the presence of ·COOH radicals as a reaction intermediate, with an observed stable and consistent Faradaic efficiency and current density for production of formate by electrolysis over 5 h. This study emphasises the significant role of porosity of MOFs as they react and evolve during electroreduction of CO2 to generate value-added chemicals.

Synthesis and biological evaluation of camptothecin substituted norcantharimide derivatives.

In this paper, a series of novel derivatives of camptothecin substituted norcantharimide was designed by mimic strategy. These compounds were synthesized in moderate yields by directly coupling CPT with N-amino acid norcantharimides. Their cytotoxicity to four human tumour cell lines (HepG2, BGC-803, SW480 and PANC-1) and normal human cell lines L-O2 and HIEC was evaluated. The synthesized CPT substituted norcantharimide analogs (3g and 3f) showed better anti-hepatocarcinoma activity than CPT. Compounds 3d, 3e, 3g, 3h and 3i also showed strong inhibition activity against BGC803.

Risks to aquatic environments posed by 14 pharmaceuticals as illustrated by their effects on zebrafish behaviour.

The presence of pharmaceutical residues in aquatic ecosystems is a worldwide problem that may pose serious threats and challenges to the environment, especially to the safety of aquatic biota. In the present study, we investigated the effects of 14 environmentally relevant pharmaceutical compounds on individual and collective-related behaviours in juvenile zebrafish (Danio rerio) for 21 days. The tested concentrations of the compounds spanned three orders of magnitude. This study also compared the potential risks of these compounds in Chinese surface waters based on the data on their toxic effects or only on behavioural effects. In the case of individual behaviours, most antidepressants, but not anti-inflammatory agents or blood lipid-lowering agents, decreased fish locomotor activity (LMA) and individual social activity (IDS); however, all three classes of compounds induced significant disruptions in the light/dark transition locomotor response (LMR-L/D) performance, even at lower treatment levels (0.1-1 µg/L). Furthermore, collective behaviour (CLB) analysis suggested that most of the compounds significantly altered the group sociability of fish and frequently occurred at environmentally relevant concentrations. Finally, a risk assessment suggested that the presence of ibuprofen, fluoxetine, and venlafaxine in the surface waters of China poses a relatively high risk to fish, regardless of the risk ranking based on the data of the toxic or behavioural effects.

A feasible strategy to improve confident elemental composition determination of compounds in complex organic mixture such as natural organic matter by FTICR-MS without internal calibration.

Confident elemental composition determination of compounds in complex samples such as natural organic matter (NOM) by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is challenging due to the interference between multiple components in these samples during detection. Here the performance of Solarix 15T-FTICR-MS in terms of accurate relative natural isotope abundance (RIA) and mass measurements for elemental composition determination of compounds in complex samples such as NOM was systematically evaluated. The optimal sweep excitation power values ranging from 20% to 22% was found to significantly diminish the underestimation of RIA measurement for 13C1 peaks of NOM components by FTICR-MS. Random error was found to be one of the main sources for the RIA errors of 13C1 peaks with S/N ratios <25. The mean averaged RIA errors of less than 10% could be obtained by averaging the measured RIAs of each 13C1 peaks in five replicated runs. By adjusting the total ion abundance of NOM complex sample between 3.8-E7 and 1.4-E8 which was simultaneously similar to that of external calibrant during detection, mass errors of lower than 1 ppm for NOM components with m/z lower than 700 Da could be obtained without internal calibration. Meanwhile, a linear correlation between mass errors of ions in NOM complex sample and their m/z values could be obtained. The mass error deviation derived from the linearity was firstly used as new criterion to reduce the number of false formula candidates. A novel strategy of combination of high mass accuracy, high spectral accuracy, and mass error deviation for elemental composition determination of unknown compounds in complex sample such as NOM by FTICR-MS was proposed and applied for different complex samples. Compared to the traditional method, about one fold increasement in the number of the unique formula assignments for measured ions was obtained by using our strategy.