Low Molecular Weight Organic Acids Research Articles

Annual hypoxia causing long-term seawater acidification: Evidence from low-molecular-weight organic acids in the Changjiang Estuary and its adjacent sea area

In this study, components, concentrations, distribution characteristics, sources of low-molecular-weight organic acids (LMWOAs) and relationships among the annual hypoxia, LMWOAs and seawater acidification were investigated in the Changjiang Estuary and its adjacent sea area in July 2015. Lactic, acetic and formic acids were detected in the seawater samples in the study area, and their total concentrations (ΣLMWOAs) varied from 0 to 262.6 μmol·L−1, with an average value of 39.2 μmol·L−1. In the surface seawater, high concentration areas of ΣLMWOAs occurred in the sea area near the Changjiang Estuary and the Hangzhou Bay, and north of study area. In the sampling stations along transect A6, high concentration areas of ΣLMWOAs appeared in the bottom seawater of nearshore stations and middle seawater of offshore stations. The terrigenous inputs, especially the Changjiang runoff, were the dominant sources for LMWOAs in the sampling period. The consistency of hypoxia areas, high concentration areas of ΣLMWOAs and low pH value areas in winter and summer suggested that annual hypoxia could cause the long-term seawater acidification by producing LMWOAs in the Changjiang Estuary and its adjacent sea area.

Responses of the marine carbonate system to a green tide: A case study of an Ulva prolifera bloom in Qingdao coastal waters

As an environmental nuisance, Ulva prolifera green tides have occurred annually in the southern Yellow Sea since 2007. While it is expected that high levels of biological activity during these blooms can alter seawater carbonate chemistry, there has been little research on the responses of marine carbonate system to green tides. Here, the effects of the bloom on the carbonate system were examined on three cruises in June, July, and September, corresponding to the early-, late-, and after-bloom periods of the U. prolifera bloom in Qingdao coastal waters in 2018. Among these three stages, the pH (National Bureau of Standards scale), dissolved inorganic carbon (DIC), total alkalinity (TA), and partial pressure of CO2 (pCO2) were all affected by bloom, with the highest pH and lowest DIC and TA concentrations of the surface seawater occurring at the late-bloom stage. While pCO2 continuously increased from the beginning to the end of the bloom. TA increased by ∼40 μmol kg−1 between the early- and after-bloom periods likely due to the shifts in the carbonate system equilibrium caused by increased CO32− concentrations and the organic matter released by U. prolifera during decomposition. Compared to nearby areas with no U. prolifera bloom, the green tide, along with increasing temperature, reduced the pH and DIC but increased the TA and pCO2. This large-scale bloom also turned the coastal waters from being an atmospheric CO2 sink to a strong source, with the estimation of air-sea CO2 fluxes about 1.69 ± 1.70, 2.28 ± 1.16, and 7.44 ± 5.84 mmol m−2 d−1 during the early-, late-, and after-bloom periods, respectively. This bloom event also promoted the formation of CaCO3 and was an important source of low molecular weight organic acids. These new findings provide nuances for the current conversations on the role of biological processes in modulating marine carbonate system and the contribution of organic matter to alkalinity.

Effect of low-molecular-weight organic acids on phosphorus soil activation: A laboratory study of the soils from Wangbeng section of the Huaihe River Basin, China

Farmland soil samples from the northern and southern banks of the Wangbeng section of the Huaihe River Basin, China, were collected and treated with three different low-molecular-weight organic acids (LMWOAs) (malic acid, citric acid, oxalic acid). This study aimed to determine how these acids affect soil phosphorus activation. The results showed that the average activation rate of total phosphorus, inorganic phosphorus, Fe/Al-P and Ca-P in soil samples from the southern bank treated with malic and citric acid was above 162%, except for organic phosphorus, with the highest at 192.04%. The three organic acids displayed significantly greater phosphorus activation in the northern bank soil samples than those of the southern bank. However, the overall average activation rate in the northern bank soils was lower than that of the southern bank. The four factors of phosphorus species, acid species, acid concentration, and treatment time had significant effects on phosphorus activation in the soils from both banks. This study showed that the three organic acids significantly activated inert phosphorus in the soil. Among them, malic acid and citric acid had a stronger effect on activating soil phosphorus and increased the available soil phosphorus utilisation rate.

Influence of Iron Addition (Alone or with Calcium) to Elements Biofortification and Antioxidants in Pholiota nameko.

Mushrooms supplementation with iron (Fe) is usually limited, and therefore it would be beneficial to search for other vital elements able to improve the process. The aim of this study was to verify a possible interaction between Fe and calcium (Ca) to estimate the role of the addition of the latter metal to stimulate Fe accumulation in Pholiota nameko. Additionally, an analysis of phenolic compounds and low molecular weight organic acids (LMWOAs) was performed. The increase of Fe concentration in the substrate caused a significantly higher accumulation of this metal in P. nameko. The addition of Ca (5 or 10 mM) stimulated Fe accumulation, just as Fe concentration in the substrate stimulated Ca accumulation, which pointed to a synergism between these metals. The obtained results show that the presence of Fe in the substrate may also promote K, Mg, Mn, Na, P, and S accumulation. In contrast, the addition of Ca stimulates and/or inhibits their content in fruit bodies. The phenolic and organic acids profile was poor. Only gallic, 4-hydroxybenzoic, sinapic and syringic acids (phenolics), as well as citric and succinic acids (LMWOAs), were quantified in some combinations in P. nameko fruiting bodies.

A Possibility to Use Selected Crop Post-Extraction Wastes to Improve the Composition of Cultivated Mushroom Pleurotus citrinopileatus

A cultivated mushroom species, Pleurotus citrinopileatus, is becoming increasingly popular thanks to its attractive colour and medicinal properties. In this study, P. citrinopileatus was grown in a cultivation medium enriched with wheat bran (WB), thymus post-extraction waste (TPEW) and pumpkin post-extraction waste (PPEW) products. The study showed that the post-extraction wastes are a crucial factor determining the accumulation of minerals, the content/profile of low-molecular-weight organic acids (LMWOAs) and phenolic compounds in fruit bodies, thereby increasing their nutritional value. The use of the waste materials significantly increased LMWOAs contents. The sum of LMWOAs under all cultivation mediums increased, especially quinic, malic and citric acids under the 20% PPEW, 25 and 50% TPEW addition. Total phenolic content, phenolic content, as well as the composition and scavenging effect on DPPH radicals, were strongly dependent on the used substrate. The control variant was poor in phenolic compounds, while the supplementation increased the contents and diversity of these metabolites. In the control, only four phenolic compounds were quantified (chlorogenic, gallic, syringic and vanillic acids), while in the supplemented substrates up to 14 different phenolic compounds (caffeic, chlorogenic, p-coumaric, 2,5-dihydroxybenzoic acid, ferulic, gallic, protocatechuic, salicylic, sinapic, syringic, trans-cinnamic and vanillic acids, catechin and rutin).

Metal oxide loaded biochars derived from Chinese bai jiu distillers' grains used for the adsorption and controlled release of phosphate

The resource utilization of distillers' grains (DGs) is an essential issue for the sustainable development of Chinese bai jiu industry. In this study, metal oxide (MxOy, M=Mg, Al and Fe) loaded biochar (MBC) was prepared by using DGs for the production of novel adsorption/release materials for phosphate (P). The results indicated that the P adsorption capacity of Mg-BC, Al-BC and Fe-BC were as high as 14.74, 8.06 and 14.51 mg P/g, respectively. XPS and FTIR analysis demonstrated that the adsorption mechanism of MBC for P included electrostatic attraction, hydrogen bonding, ion exchange, precipitation and ligand exchange. The release of P from M-BC+P could be controlled by low molecular weight organic acids (LMWOAs), which were affected by the loaded metal oxides on the biochar. The release of P from Mg-BC+P was higher than 70 % after 7 days, which was about 60 % if Al-BC+P was used. Thus, M-BC+P can be used as a high-performance controlled release phosphate fertilizer, providing a promising value-added application approach for the bai jiu distillers' grains.

Effects of low-molecular-weight organic acids/thiols on hydroxyl radical production from natural siderite oxidation

Oxygenation of siderite produces hydroxyl radicals (•OH) that are capable of transforming the pollutants. Yet, the influence of low-molecular-weight organic acids (LMWOAs)/ thiols (LMWOTs) which are widely occurring in soils and waters on •OH production from the oxygenation process of siderite is poorly understood. Results of this study show that the presence of LMWOAs/LMWOTs significantly facilitated •OH production from siderite oxidation by O2 at pH 6–8. For instance, at pH 7, the cumulative •OH concentration within 24 h was only 1.3 μM for oxygenation of 1 g/L siderite, while it boosted to 19.7 and 7.2 μM, respectively, with the respective addition of 1 mM ethylenediaminotetraacetate and cysteine. The mechanisms responsible for the enhanced •OH production are associated with the complexation ability and redox activity of LMWOAs/LMWOTs. In the absence of LMWOAs/LMWOTs, •OH is mainly produced from the oxidation of adsorbed Fe(II) by O2, followed by the oxidation of structural Fe(II) on siderite surface. In the presence of LMWOAs, LMWOAs react with adsorbed Fe(II) and structural Fe(II) to produce complexed Fe(II). Therefore, the oxidation of LMWOAs complexed Fe(II) by O2 predominantly contributed to •OH production. Although the complexation ability of LMWOTs is weaker than that of LMOWAs, LMWOTs can reduce O2 to generate •O2− and H2O2, thus facilitating •OH production. Based on the proposed mechanisms, a kinetic model was developed to quantify the relative contribution of each pathway to •OH production. The addition of 1 mM citrate and cysteine in siderite suspension could increase the removal of trichloroethylene from <5% to 15% and 7%, respectively. Our study reveals the overlooked catalytic effects of LMWOAs/LMWOTs in enhancing •OH production from siderite oxidation by O2 under redox-dynamic conditions.

The pH-sensitive sorption governed reduction of Cr(VI) by sludge derived biochar and the accelerating effect of organic acids

Reduction coupling immobilization is one of the most commonly adopted strategies for the remediation of Cr(VI) contamination. Biochar is a carbon-rich material with abundant active functional groups for sorption and reduction reactions. In previous reports, phytomass derived biochars and organic functional groups have been emphasized, while the performance of sludge derived biochar (SBC) has often been understated. In the present study, a 30 d kinetic study proved that the removal route involved the sorption of Cr(VI), reduction to Cr(III) and immobilization of Cr(III), and that the sorption process was the primary and rate determining step. As a result of the SBC alkalinity, the solution pH increased, and sorption was largely inhibited, which then governed the overall removal ratio. The FTIR spectra suggested the involvement of hydroxyls in these processes. Low molecular weight organic acids accelerated the removal process in the early phase and improved the reduction process.

Enhanced mobilization of arsenic from tailing soil by four types of low molecular weight organic acids with different functional groups

Enhanced mobilization of arsenic from tailing soil by four types of low molecular weight organic acids with different functional groups

Dynamics of low-molecular-weight organic acids for the extraction and sequestration of arsenic species and heavy metals using mangrove sediments

Mangrove wetlands are subjected to pollution due to anthropogenic activities. Mangrove fitness is mainly determined by root exudates and microorganisms activities belowground, but the mechanisms are not yet well known. Rhizospheric interactions among mangrove sediments, microorganisms and root exudates were simulated. In particular, low-molecular-weight organic acids (LMWOA), were examined to explore the metal(loid)s rhizospheric dynamics via batch experiments. Using a combination of comparative sterilised and unsterilised sediments, LMWOA extracts and sediments constituents were examined. Factors such as the solution pH, dissolved organic carbon (DOC), arsenic and iron species and metal(loid)s in the aqueous phase were evaluated. The results show that on an average, the As decreased by 68.3 % and 42.1 % under citric and malic acid treatments, respectively, after sterilisation. In contrast, the As content increased by 29.6 % under oxalic acid treatment. Microorganisms probably facilitate sediment As release in the presence of citric and malic acids but suppress As mobilisation in the presence of oxalic acid. Fe, Mn and Al were significantly (p < 0.05) positively correlated with the trace metal(loid)s (Zn, Pb, Ni, Cu, Cr, Co, Ba, Cd and As). The solution pH was negatively correlated with the solution As. Both DOC and pH reach the peaks at the end of all treatments. The As absorption–desorption dynamics are closely linked to proton consumption, Fe-Mn-Al sedimentation of ageing performance and organic ligand complexation. The study provides an insight into the rhizospheric processes of microbial involvement and gives an enlightening understanding of the metal(loid)s redeployment for plant adaptation in mangrove wetlands.

Towards a Soil Remediation Strategy Using Biochar: Effects on Soil Chemical Properties and Bioavailability of Potentially Toxic Elements.

Soil contamination with potentially toxic elements (PTEs) is considered one of the most severe environmental threats, while among remediation strategies, research on the application of soil amendments has received important consideration. This review highlights the effects of biochar application on soil properties and the bioavailability of potentially toxic elements describing research areas of intense current and emerging activity. Using a visual scientometric analysis, our study shows that between 2019 and 2020, research sub-fields like earthworm activities and responses, greenhouse gass emissions, and low molecular weight organic acids have gained most of the attention when biochar was investigated for soil remediation purposes. Moreover, biomasses like rice straw, sewage sludge, and sawdust were found to be the most commonly used feedstocks for biochar production. The effect of biochar on soil chemistry and different mechanisms responsible for PTEs’ immobilization with biochar, are also briefly reported. Special attention is also given to specific PTEs most commonly found at contaminated soils, including Cu, Zn, Ni, Cr, Pb, Cd, and As, and therefore are more extensively revised in this paper. This review also addresses some of the issues in developing innovative methodologies for engineered biochars, introduced alongside some suggestions which intend to form a more focused soil remediation strategy.

Key factors affecting seed germination in phytotoxicity tests during sheep manure composting with carbon additives

The germination index (GI) was widely applied to evaluate the phytotoxicity of compost. This study investigated the key phytotoxicity factors affecting seed germination in compost by using aqueous extracts in seed germination tests. The relationship between water-soluble substances in compost and seed germination, and their association with the microbial community were identified. In this study, sheep manure (SM) composted along or with three carbon additives (mushroom substrate, MS; cornstalks, CS; garden substrate, GS) for 49 days and, during this time, changes in multiple physical-chemical parameters, carbon and nitrogen matters, germination indexes (GI) and the compost microbiome were monitored. The results showed that all additives decreased water-soluble total nitrogen (TN), ammonium nitrogen (NH4+-N) and low molecular weight organic acids, and significantly improved the seed germination indexes (seed germination rate, radical length and GI). The GI was correlated with water-soluble carbon degradation products (TOC, butyric acid, humic acid) and certain bacteria (Planifilum, Oceanobacillus, Ruminococcaceae_UCG_005 and Saccharomonospora). A structural equation model revealed that the main factors affecting seed germination were TOC (SM compost), acetic acid (SM+MS compost), humic acid (SM+CS compost), and pH (SM+GS compost). Low TOC and low molecular weight organic acids contents and higher humic acid content promoted GI. The research results could provide theoretical basis and measures for directional regulation of compost maturity.

Examination of Cd Accumulation Within Sunflowers Enhanced by Low Molecular Weight Organic Acids in Alkaline Soil Utilizing an Improved Freundlich Model

Examination of Cd Accumulation Within Sunflowers Enhanced by Low Molecular Weight Organic Acids in Alkaline Soil Utilizing an Improved Freundlich Model

Insight into the Influencing Mechanism of Endophytic Bacteria on the Adsorption of Heavy Metals by Plants: A Review

The research of endophytic bacteria (EB) has attracted increased attention, especially where its application provides a new and effective solution for heavy metals (HMs) polluted control in soil. Therefore, the investigation of endophytes has boomed in hopes of insight into their deeper and complex mechanisms in the phytore-mediation process. Endophytes can not only facilitate plants’ growing and developing, but also promote the enrichment of heavy metals, so as to achieve the goal of environmental restoration. This paper summarizes the research achievements about endophytes in recent years from the following aspects: the discovery and application of endophytes, effects of endophytes on plant growth, heavy metal absorption promoted by endophytes in plants. The study found that endophytes can perfectly symbiosis with plants. Endophytes promote the growth and tolerance to heavy metals of plants by secreting IAA, 1-aminocyclopropane-1 carboxylic deaminase (ACC deaminase), iron carrier, biosurfactant and low molecular weight organic acids. There were other studies that showing that endophytes can enhance the resistance of host plants in adverse environments such as drought resistance, heat resistance and disease resistance. Future application prospects and development direction of endophytes in plants are also discussed in detail. Such as (1) endophytes can help plants resist pests and diseases reflected in the competition with pathogenic bacteria for niche and nutrients to prevent the invasion and reproduction of pathogenic bacteria. (2) Some metabolites produced by endophytic bacteria can be used in medicine. (3) endophytes can effectively reduce the harmful substances accumulated in plants, and the toxic effect of pollutants on plants and enable plants to repair themselves.

Insights into the molecular mechanism of tetracycline transport in saturated porous media affected by low-molecular-weight organic acids: Role of the functional groups and molecular size

The transport of tetracycline possessed a great challenge in its environmental applications. This study looked at how various low-molecular-weight organic acids (LMWOAs) affect the transport of tetracycline in environments. To that end, four LMWOAs were employed in experiments; acetic acid, malonic acid, malic acid, and citric acid. It was observed that LMWOAs promoted the tetracycline passage in presence of various experimental environments. The LMWOAs steric hindrance and deposition competition facilitated tetracycline transport at pH 5.0. The other deposition mechanism for tetracycline was the electrostatic repulsion between tetracycline and sand enhanced by deprotonated LMWOAs at pH 7.0. Moreover, the enhanced effects of LMWOAs on tetracycline mobility were intensively dependent on LMWOA type with more functional groups (e.g. carboxyl and hydroxyl groups) and larger molecular size supported stronger deposition competition, steric hindrance as well as electrostatic repulsion. Additionally, cation-bridging played a vital role for the enhanced effects of LMWOAs on tetracycline transport with divalent cations (e.g., Ca2+ and Pb2+). Interestingly, tetracycline exhibited a higher mobility in the presence of Ca2+ relative to Pb2+ regardless of LMWOAs-free or LMWOAs-addition. This phenomenon was attributed to the fact that Pb2+ has a greater affinity with tetracycline and LMWOAs than Ca2+. Furthermore, under the shadow of numerous LMWOAs, the non-equilibrium two site transportation model was employed to investigate the movement of tetracycline in porous saturated media. The present study suggests that LMWOAs may be important considerations in assessing the antibiotic passage in soil as well as groundwater.

Production of Organic Acids by Arbuscular Mycorrhizal Fungi and Their Contribution in the Mobilization of Phosphorus Bound to Iron Oxides.

Most plants living in tropical acid soils depend on the arbuscular mycorrhizal (AM) symbiosis for mobilizing low-accessible phosphorus (P), due to its strong bonding by iron (Fe) oxides. The roots release low-molecular-weight organic acids (LMWOAs) as a mechanism to increase soil P availability by ligand exchange or dissolution. However, little is known on the LMWOA production by AM fungi (AMF), since most studies conducted on AM plants do not discriminate on the LMWOA origin. This study aimed to determine whether AMF release significant amounts of LMWOAs to liberate P bound to Fe oxides, which is otherwise unavailable for the plant. Solanum lycopersicum L. plants mycorrhized with Rhizophagus irregularis were placed in a bicompartmental mesocosm, with P sources only accessible by AMF. Fingerprinting of LMWOAs in compartments containing free and goethite-bound orthophosphate (OP or GOE-OP) and phytic acid (PA or GOE-PA) was done. To assess P mobilization via AM symbiosis, P content, photosynthesis, and the degree of mycorrhization were determined in the plant; whereas, AM hyphae abundance was determined using lipid biomarkers. The results showing a higher shoot P content, along with a lower N:P ratio and a higher photosynthetic capacity, may be indicative of a higher photosynthetic P-use efficiency, when AM plants mobilized P from less-accessible sources. The presence of mono-, di-, and tricarboxylic LMWOAs in compartments containing OP or GOE-OP and phytic acid (PA or GOE-PA) points toward the occurrence of reductive dissolution and ligand exchange/dissolution reactions. Furthermore, hyphae grown in goethite loaded with OP and PA exhibited an increased content of unsaturated lipids, pointing to an increased membrane fluidity in order to maintain optimal hyphal functionality and facilitate the incorporation of P. Our results underpin the centrality of AM symbiosis in soil biogeochemical processes, by highlighting the ability of the AMF and accompanying microbiota in releasing significant amounts of LMWOAs to mobilize P bound to Fe oxides.

Lead speciation and availability affected by plants in a contaminated soil

Changes in lead (Pb) speciation in the rhizosphere may be plant species-dependent and dictate Pb fate and behavior in the soil-plant system. X-ray absorption near edge structure (XANES) spectroscopy can explain how these changes affect Pb availability in soils and its uptake by plants. We investigated the changes in Pb speciation and availability in the rhizosphere of eucalypt (Eucalyptus urophylla x Eucalyptus grandis), palisade grass (Urochloa brizantha cv. Marandu), and Indian mustard (Brassica juncea L.) using XANES spectroscopy. A greenhouse experiment was performed in a complete randomized design, with three plant species and a no plant control treatment. After three months, rhizosphere and bulk soil samples were collected, Pb speciation was assessed by Pb L3-edge XANES spectroscopy, and Pb concentration was determined in plant tissue. In bulk soil, we found Pb primarily as Pb-Il (Pb sorbed to illite; 48%) and lead monoxide (PbO; 36%). In the rhizosphere, Pb-Ka (Pb sorbed to kaolinite; 33–56%) and (CH₃COO)₂Pb (25–41%) were the main Pb forms, the latter suggesting Pb complexation by low molecular weight organic acids (LMWOAs). Palisade grass rhizospheric soil had a lower abundance of Pb-Ka and a higher abundance of (CH₃COO)₂Pb than eucalypt and mustard, which led to low Pb concentration in plant tissue. LMWOAs exudation followed by Pb2+ complexation is the apparent mechanism used by palisade grass to detoxify the rhizosphere and control Pb uptake. Given its low Pb uptake and potential to complex Pb in organic forms, palisade grass may be a promising species for Pb phytostabilization in contaminated soils.

Rice Seedling Growth Promotion by Biochar Varies With Genotypes and Application Dosages.

While biochar use in agriculture is widely advocated, how the effect of biochar on plant growth varies with biochar forms and crop genotypes is poorly addressed. The role of dissolvable organic matter (DOM) in plant growth has been increasingly addressed for crop production with biochar. In this study, a hydroponic culture of rice seedling growth of two cultivars was treated with bulk mass (DOM-containing), water extract (DOM only), and extracted residue (DOM-free) of maize residue biochar, at a volumetric dosage of 0.01, 0.05, and 0.1%, respectively. On seedling root growth of the two cultivars, bulk biochar exerted a generally negative effect, while the biochar extract had a consistently positive effect across the application dosages. Differently, the extracted biochar showed a contrasting effect between genotypes. In another hydroponic culture with Wuyunjing 7 treated with biochar extract at sequential dosages, seedling growth was promoted by 95% at 0.01% dosage but by 26% at 0.1% dosage, explained with the great promotion of secondary roots rather than of primary roots. Such effects were likely explained by low molecular weight organic acids and nanoparticles contained in the biochar DOM. This study highlights the importance of biochar DOM and crop genotype when evaluating the effect of biochar on plants. The use of low dosage of biochar DOM could help farmers to adopt biochar technology as a solution for agricultural sustainability.

Cadmium biosorption and mechanism investigation using a novel Bacillus subtilis KC6 isolated from pyrite mine

Cadmium (Cd)-remediation by microorganisms has been frequently used due to environmental friendliness, low cost and easy operation. However, the mechanisms of bio-remediation were not clear enough. Hence, a strain KC6, identified as Bacillus subtilis, was isolated from the metal contaminated soil around an open-air pyrite mine. KC6 had high resistance to Cd (about 100 mg L−1) and was able to produce siderophores (0.66 A/Ar) and solubilize phosphate (21.98 mg L−1). Besides, in the optimum experiment, Bacillus subtilis KC6 showed the greatest ability to remove Cd with pH 7 and 35 °C, and the revolution had little effect on Bacillus subtilis KC6 adsorbing Cd. Moreover, Bacillus subtilis KC6 had higher Cd sorption ability under 10 and 40 mg/L Cd treatment about 86.33%, 65.33%, respectively. Through Scanning Electron Microscope - Energy Dispersive Spectrometer (SEM-EDS), Fourier transform infrared spectra (FTIR) and element mapping analyses, Cd in solution was bonded onto cell walls of KC6 by increasing functional groups. Besides, under Cd stress, low molecular weight organic acids (malic acid, oxalic acid, citric acid and succinic acid) produced by strain KC6 increased significantly compared to non-Cd treatment. The various functional groups and exudates could help KC6 to chelate Cd to Cd-ligands complexes so that Cd could be bonded onto cell wall and transport into cellular organs and cytoplasm.

Fluorescent dissolved organic matter facilitates the phytoavailability of copper in the coastal wetlands influenced by artificial topography

Dissolved organic matter (DOM) is a crucial driver in ecosystem services and a central part of the carbon transport and biological cycle in land-sea interaction. DOM exhibits characteristic environmental behavior in the coastal zone, but its sustainability is affected by expanding artificial topography (AT) construction. It requires combining analyses on AT-induced response of field fluorescent DOM (fDOM) and its quenching pattern under metal-complexation. Herein, we conducted systemic investigations into the spatiotemporal dynamics of fDOM compositions with further in-lab verification to study its Cu-binding capacity. We detected three humid-like fDOM components sensitive to AT. The total fDOM intensity was positively correlated with low molecular weight organic acid (LMWOA) extractable Cu and the Cu pools in above-ground biomass. The enriched fDOM serves as an ecological engineer by increasing the Cu mobility, confirmed by an in-lab fluorescence titration. The application of LMWOA greatly enhanced the intensity of one fDOM component, elevated its conditional stability constant, and decreased its quenched proportion, implying that LMWOA might extract part of Cu from fDOM complexation. The present work provides an “fDOM-LMWOA pump” explanation to suggest that fDOM is a novel ecological regulator on vegetation growth under the AT-induced matter accumulation.