Modeling the biodegradation of multicomponent organic matter in an aquatic environment: 3. Analysis of lignin degradation mechanisms

Mechanisms of enzymatic degradation of a persistent organic substance are discussed in the case of lignin. The major groups of lignin-decomposing microorganisms and their enzymatic systems are described. The biochemical mechanisms of the action of main lignin-decomposing enzymes are analyzed. Typical sizes of enzyme molecules are estimated. The results of analysis are used to formulate the major regularities of lignin destruction, which are required for the construction of a kinetic model of this process.     

Physical mechanism and mathematical modeling of earthquake ionospheric precursors registered in total electron content

The physical mechanism by which the regions with increased or decreased total electron content, registered by measuring delays of GPS satellite signals before strong earthquakes, originate in the ionosphere has been proposed. Vertical plasma transfer in the ionospheric F ₂ region under the action of the zonal electric field is the main disturbance formation factor. This field should be eastward, generating the upward component of plasma electromagnetic drift, in the cases of increased total electron content at midlatitudes and deepened minimum of the F ₂ layer equatorial anomaly. Upward plasma drift increases electron density due to a decrease in the O⁺ ion loss rate at midlatitudes and decreases this density above the equator due to an enhancement of the fountain effect (plasma discharge into the equatorial anomaly crests). The pattern of the spatial distribution of the seismogenic electric field potential has been proposed. The eastward electric field can exist in the epicentral region only if positive and negative electric charges are located at the western and eastern boundaries of this region, respectively. The effectiveness of the proposed mechanism was studied by modeling the ionospheric response to the action of the electric field generated by such a charge configuration. The results of the numerical computations indicated that the total electron content before strong earthquakes at middle and low latitudes is in good agreement with the observations.     

Population dynamics of earthquakes and mathematical modeling

We present a mathematical model that describes temporal variations of earthquakes. This model is represented as $$dn(t)/dt = n(t)\left[ {\alpha - \beta n(t) - \int_{ - \infty }^t {n(s)h(t - s)ds} } \right].$$ Heren(t) shows the numberof earthquakes per unit time in a certain region. α and β are constants. The functionh(t) denotes the hysteresis effect of the earthquake occurrences and can take the following forms depending on the physical conditions of the crusts; (A)h(t)=0: the equation represents a logistic type increase or decrease and approaches a stationary state asymptotically. This describes aftershock series of large earthquakes and earthquake swarms of large scale such as the Wakayama and Matsushiro swarms in Japan; (B)h(t)=constant (β=0): frequencyn(t) increases initially and then decreases gradually and shows some kind of volcanic swarms; (C)h(t) = κ · {exp(?γ₁ t) ? exp(γ₂ t)}, (γ₂ > γ₁): this denotes time delay effects and the model shows periodic patterns of bursts or “rhythms” of earthquakes, which are observed in earthquake swarms. When external effects are taken into consideration, the model is further generalized and can describe various seismic patterns. These effects represent various influences of the circumstances like the earth tide and fluctuations of plate motions, etc. Whenh(t) takes type (A) and the external effect is random, the equation displays repetitive random patterns with bursts. Particularly interesting cases may be those whenh(t) is type (C) and the external force is periodic like the earth tide. Various nonperiodic as well as periodic patterns of earthquakes appear. These are the phenomena of “chaos” and “entrainment”, etc. and can be commonly observed. Varieties of actual earthquake patterns seem to be, at least partly, explained by the nonlinear coupling between the tidal forces and autonomous rhythms of earthquakes.     

Mathematical modeling of marine environment pollution processes by petroleum hydrocarbons and their degradation in Caspian Sea ecosystem

The available observational data on the pollution of tributaries and areas of the Caspian Sea by petroleum hydrocarbons and products are examined. The possible petroleum input from sources in the sea is assessed using up-to-date data of satellite observations of sea surface pollution by oil films. The hydroecological CNPSi-model is applied to studying water pollution processes by petroleum hydrocarbons in ten areas chosen in the Caspian Sea and the subsequent biodegradation of those pollutants. The model calculations of the within-year dynamics of petroleum hydrocarbon concentrations use mean annual observational data on within-year variations in water mediium characteristics (water temperature, light intensity, and transparency), as well as the morphometric parameters of sea areas (the area, mean depth, and water volumes). The characteristics of water exchange between the areas were evaluated using a hydrodynamic model. The model calculations were used to characterize the within-year variations in petroleum hydrocarbon concentrations, the biomasses of petroleum-oxidizing bacteria, the characteristics of their oxidation activity and bioproduction, and the internal fluxes of petroleum hydrocarbons (their input from various sources, horizontal and vertical transport, and biotransformation) in different sea areas. Calculation results were used to compile annual balances for the processes of input and consumption of petroleum hydrocarbons in the chosen and aggregated sea areas.     

Ecosystem response to antibiotics entering the aquatic environment

Awareness of antibiotics in wastewaters and aquatic ecosystems is growing as investigations into alternate pollutants increase and analytical techniques for detecting these chemicals improve. The presence of three antibiotics (ciprofloxacin, norfloxacin and cephalexin) was evaluated in both sewage effluent and environmental waters downstream from a sewage discharge. Bacteria cultured from the sewage bioreactor and receiving waters were tested for resistance against six antibiotics (ciprofloxacin, tetracycline, ampicillin, trimethoprim, erythromycin and trimethoprim/sulphamethoxazole) and effects of short term exposure (24 h) to antibiotics on bacterial denitrification rates were examined. Antibiotics were detected entering the sewage treatment plant with varying levels of removal during the treatment process. Antibiotics were also detected in effluent entering receiving waters and detectable 500 m from the source. Among the bacteria cultured from the sewage bioreactor, resistance was displayed against all six antibiotics tested and bacteria cultured from receiving waters were resistant against two of the antibiotics tested. Rates of denitrification were observed to decrease in response to some antibiotics and not to others, though this was only observed at concentrations exceeding those likely to be found in the environment. Findings from this preliminary research have indicated that antibiotics are entering our aquatic systems and pose a potential threat to ecosystem function and potentially human health.     

论有机氮磷在湖泊水环境中的作用和重要性

长期以来,国内外学者对湖泊中氮磷等营养物质及其循环开展了大量研究,在其污染过程、控制和管理等方面取得了许多重要进展。然而,现有研究主要集中在总氮、总磷和无机氮磷等方面,对有机氮磷的来源、循环及生物和生态学效应的研究相对缺乏。近期研究显示:有机氮磷是湖泊水体和沉积物中的重要组分,可以通过酶解和微生物活动转化成生物可利用性营养盐,在湖泊生态系统中起着十分重要的作用。本文简要分析了有机氮磷已有的研究进展,论述了有机氮磷在湖泊水环境研究中的重要性、研究难点、主要技术突破及存在的科学问题,指出有机氮磷研究将有助于加深目前对水生态系统和富营养化机理的认识,并对水质标准制定、环境质量评价、污染控制和生态修复具有十分重要的价值。研究表明:在各种无机氮磷研究的基础上,开展各种有机氮磷等营养组分的时空分布特征、在主要界面的迁移转化及其生物有效性研究,揭示有机氮磷与湖泊生命过程的耦合关系,完善氮磷循环理论,将是未来该领域的主要研究方向。     

The BEAM-project: prediction and assessment of mixture toxicities in the aquatic environment

Freshwater and marine ecosystems are exposed to various multi-component mixtures of pollutants. Nevertheless, most ecotoxicological research and chemicals regulation focus on hazard and exposure assessment of individual substances only, the problem of chemical mixtures in the environment is ignored to a large extent. In contrast, the assessment of combination effects has a long tradition in pharmacology, where mixtures of chemicals are specifically designed to develop new products, e.g. human and veterinary drugs or agricultural and non-agricultural pesticides. In this area, two concepts are frequently used and are thought to describe fundamental relationships between single substance and mixture effects: Independent Action (Response Addition) and Concentration Addition. The question, to what extent these concepts may also be applied in an ecotoxicological and regulatory context may be considered a research topic of major importance, as the concepts would allow to make use of already existing single substance toxicity data for the predictive assessment of mixture toxicities. Two critical knowledge gaps are identified: (a) There is a lack of environmental realism, as a huge part of our current knowledge about the applicability of the concepts is restricted to artificial situations with respect to mixture composition or biological effect assessment. (b) The knowledge on what exactly is needed for using the concepts as tools for the predictive mixture toxicity assessment is insufficient. Both gaps seriously hamper the necessary, scientifically sound consideration of mixture toxicities in a regulatory context.In this paper, the two concepts will be briefly introduced, the necessity of considering the toxicities of chemical mixtures in the environment will be demonstrated and the applicability of Independent Action and Concentration Addition as tools for the prediction and assessment of mixture toxicities will be discussed. An overview of the specific aims and approaches of the BEAM project to fill in the identified knowledge gaps is given and first results are outlined.     

Anthropogenic transformation of aquatic environment composition in the Lena river mouth area

Variations in the hydrological-hydrochemical state of the aqueous medium in Lena mouth area. The hydrological regime of the river and variations in qualitative water composition in the mouth area are described in detail. Anthropogenic load is estimated in terms of the inflow and the modulus of inflow of pollutants.     

邛海大型水生植物时空分布及其退化原因

根据2021年7和12月、2022年5和9月邛海水生植物调查结果,结合文献资料,分析了邛海水生植物种类组成、群落结构和空间分布状况以及退化原因,提出了邛海水生植物恢复的对策建议。邛海湖区有水生植物23种,主要分布在水深2 m内,在湖泊北岸成片分布,湖泊西岸和南岸呈斑块状分布,东岸零星分布,总面积约1.3 km²。水生植物分布面积由1990s前占湖面积的20%左右缩减到目前的不足5%,沉水植物群落结构简单化,浮叶植物和挺水植物分布范围扩张。1998年洪水从海河口倒灌,致使高枧湾水域沉水植被消失;近10年来湖泊运行水位抬升和透明度下降使得邛海水生植物分布面积进一步缩小、种群单一化。需要恢复邛海水位运行的自然节律,减少污染负荷输入改善水体透明度,辅之人工生态修复等措施,逐步恢复邛海水生态系统健康。     

Modeling the biodegradation of multicomponent organic matter in an aquatic environment: 2. Analysis of the structural organization of lignin

A model is developed to describe the degradation kinetics of an organic substance with chaotic structure of macromolecules. The model is based on the results of analysis of lignin structure and its degradation mechanisms described in previous papers of this series. Model postulates are formulated and their chemical substantiation is given. Degradation regimes corresponding to different molecular size distributions are studied. The decrease in organic carbon concentration at the asymptotic stage of the process is shown to obey the power law. Theoretical results were checked against some empirical data taken from the literature.     

The state of the aquatic environment and biota during operation of trout-breeding pond farms

The paper presents the results of studying chemical and biological quality characteristics of the aquatic environment in the area of operation of trout farms in Kondopoga Bay, Onega Lake. The concentrations of biochemically labile substances and phosphorus were found to increase near the ponds. The development dynamics of phytoplankton, zooplankton, and benthic organisms in the zone of pond farms. When the procedure of fish production is strictly followed, the effect of ponds on the aquatic environment and biota is minimal.     

Transformations of biogenic substances in Tatar Strait water (the Sea of Japan): Analysis of mathematical modeling results

The state of the marine environment (the temperature, light intensity, transparency, biogenic load) in Tatar Strait was assessed based on mean annual data from literary sources and with the use of GIS “Sakhalin Shelf.” The entire strait was divided into three regions (northern, southwestern, and southeastern), and water exchange between them for each month was estimated by using Bergen Oceanic Model. The information about the state of the marine environment and water exchange characteristics was used as input data for a hydroecological model, which enabled the assessment of annual variations of biogenic substance concentrations and biomasses of microorganisms (heterotrophic bacteria, three groups of phytoplankton, and two groups of zooplankton) in the strait regions chosen. The development conditions of microorganism biomasses within the year can be characterized by their activity indices (specific growth rates), the values of internal fluxes of biogenic substances, and calculated bioproductivity values. The calculated biogenic substance concentrations and phytoplankton bioproductivity values showed good agreement with the estimates for the Sea of Japan and Tatar Strait available from the literature.     

Study of techniques of identifying the earthquake precursory anomalies in terms of mathematical modeling

IntroductionGenerallyspeaking,thedataofprecursorymonitoringwhichmightbeassociatedwiththepreparationofthefutureearthquakes,couldberepresentedbyatimeseries.There,however,wouldbenotonlyanomalouschangesassociatedwiththeearthquakeoccurrences,butalsosomechangeswhichwouldberelatedtosourcesotherthantheearthquakepreparation,eitherknownorunknowntotheinvestigatorsandbecalledas(thechangesfromnon-earthquakeeffects(,inthetimeseries,inpractice,tillnow.ItistosaythatthetimeseriesF(t)showingthetemporalchangesof…     

Biomass development and production created by microorganisms of lower trophic levels in the caspian sea ecosystem: Analysis of mathematical modeling results

The biohydrochemical features of the Caspian Sea ecosystem were estimated for its ten water areas with the use of a mathematical model describing the transformation of compounds of organogenic elements (C, Si, N, and P) and taking into account the morphometric characteristics of the water areas and long-term mean monthly values of the major characteristics of the aquatic environment. Variations in the estimated concentrations of mineral and aggregated biogenic substance fractions, microorganism biomasses (heterotrophic bacteria, three phytoplankton groups and two zooplankton groups) in different water areas of the sea were analyzed. The formation conditions of microorganism biomasses in different water areas are characterized by the analysis of their bioproductivity estimates based on evaluated internal biogenic substance fluxes.     

Analysis of observed and model mt fields based on three-dimensional mathematical modeling: Case study of the Verkhnee Penzhino-Korf profile

We propose a system for the analysis of magnetotelluric (MT) data, which makes use of the invariant characteristics of the impedance tensor such as the maximum and minimum induction curves and the phase tensor. We examine the coefficients of the appearance and normalization of principal values of the impedance tensor. By the case study for Koryakiya, it is shown that the three-dimensional (3D) mathematical modeling and the Wiese-Parkinson vectors allow one to correct the results of one-dimensional (1D) and two-dimensional (2D) inversion of MT curves. Comparison between model and observed data based on the 1D inversion of MTS curves provides a pictorial view of the distortions of MT curves and their sensitivity to the parameters of a geological cross section.     

Fully coupled mathematical modeling of turbidity currents over erodible bed

Turbidity currents may feature active sediment transport and rapid bed deformation, such as those responsible for the erosion of many submarine canyons. Yet previous mathematical models are built upon simplified governing equations and involve steady flow and weak sediment transport assumptions, which are not in complete accordance with rigorous conservation laws. It so far remains unknown if these could have considerable impacts on the evolution of turbidity currents. Here a fully coupled modeling study is presented to gain new insights into the evolution of turbidity currents. The recent analysis of the multiple time scales of subaerial sediment-laden flows over erodible bed [Cao Z, Li Y, Yue Z. Multiple time scales of alluvial rivers carrying suspended sediment and their implications for mathematical modeling. Adv Water Resour 2007;30(4):715–29] is extended to subaqueous turbidity currents to complement the fully coupled modeling. Results from numerical simulations show the ability of the present coupled model to reproduce self-accelerating turbidity currents. Comparison among the fully and partially coupled and decoupled models along with the analysis of the relative time scale of bed deformation explicitly demonstrate that fully coupled modeling is essential for refined resolution of those turbidity currents featuring active sediment transport and rapid bed deformation, and existing models based on simplified conservation laws need to be reformulated.     

Comparison of complexing ability of fulvic and humic acids in the aquatic environment with iron and zinc ions

Complex formation reactions with the interaction of fulvic and humic acids with zinc and iron ions in a model aqueous system. The complexing ability of humic acids was experimentally proved to be much higher than that of fulvic acids. The complexing ability of fulvic acids is found to decrease over time. The dependence of the complexing ability of heavy metals on the types of ion and humic substances and the proportions of components in the solution is examined. The obtained experimental results on the occurrence forms of heavy metals were compared with their theoretical estimates calculated for natural water bodies.     

Modeling the biodegradation of multicomponent organic matter in an aquatic environment: 1. Methodology

A methodology of modeling organic matter degradation is described. It includes the identification of a class of disordered biopolymers embracing a considerable part of stable organic matter in the aquatic environment; the choice of a reference representative of the class, which is proposed to be lignin—a widespread product of wood degradation and processing; the construction of a three-level hierarchical scheme of degradation modeling, whose top level contains the formulation of the purpose of modeling, which is to find the law of the decrease in organic matter concentration over time, the middle level includes the development of a mathematical model, and the bottom level includes the analysis of the mechanisms of the processes. The general formulation of the problem at the hierarchical levels is developed from top to bottom, while the modeling process is realized from bottom to top.