B. M. Dolgonosov

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

A vast body of literature data is used to analyze the modern concepts of the structural organization of lignin; consider the statistics of relationships and functional groups; identify the dominating relationships and groups; assess the masses and sizes of macromolecules and specific features of molecular-mass distribution; describe the characteristics of the fractal structure of macromolecules. The results are used to formulate the major structural regularities which are of importance for the development of lignin degradation model in the aquatic environment.

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.

Model of Fluctuations in Bacteriological Indices of Water Quality

The bacteriological indices of water quality, including coliforms, sulfite-reducing clostridia, total microbial count, coliphages, and fecal streptococci were analyzed. A model describing fluctuations in microorganism population in the aquatic environment is proposed. A stochastic differential equation was obtained and used to derive a lognormal distribution of organism population. The model was applied to describe time series of bacteriological indices of the Moskva River Water Source. Satisfactory agreement was obtained between theoretical distributions and empirical data in a wide range of index values embracing one to three orders of variations in microorganism population. A forecast procedure was developed and applied to calculate the exceedance probabilities of different levels of bacterial pollution of the water source. Time periods with higher bacterial pollution were identified.

Modeling variations in salt composition components of river water

The balance of a component contained in river water is considered taking into account its input with lateral inflow and decay in the aquatic environment. Random changes in lateral inflow causes fluctuations in the parameters of component input and decay. A stochastic equation of component balance is derived and used as the basis for the construction of an equation for the probability density of component concentration. The solution of this equation shows that the probability density follows lognormal law. This theoretical result is applicable to the analysis of time series of water salt composition components, including pH, alkalinity, chlorides, ammonia, iron, and aluminum. The applicability of the lognormal law is proved and distribution parameters are evaluated. The distributions of three components (pH, alkalinity, and chlorides) are found to split into two lognormal branches, describing high and low component concentrations. In the case of pH and alkalinity, this splitting is due to seasonal effects, while in the case of chlorides, it is caused by the difference between concentrations in the surface runoff at the early and final stages of snow melting and rainfalls. The application of the statistical distributions for probabilistic forecasting of extreme component concentrations is considered. The exceedance probability of standard limits of the components is considered. The use of exceedance probability in hydrochemical standardization is demonstrated.

A Nonlinear Stochastic Model Describing the Formation of Daily and Mean Monthly Water Flow in River Basins

The dynamics of runoff from a watershed is considered based on the momentum balance equation. A nonlinear runoff equation is obtained under some assumptions. The stochastic character of the process is allowed for by the introduction of two noises, which account for fluctuations in precipitation and the heterogeneity of watershed characteristics, respectively. Transition to a probabilistic description yields a new class of probability distributions of river runoff. The distributions of this class are controlled by the most fluctuating process: either by atmospheric precipitation, in which case the probability of high water flow decreases exponentially, or by the variability in the watershed structure, which yields the probability decreasing in accordance with a power law. The exponent in this law is related to the flow resistance law for water flowing over slope and channel parts of the watershed. Analysis of the obtained results showed the theoretical and empirical distributions for the Moskva and Volga rivers to be in satisfactory agreement.

Statistical distributions of phytoplankton concentration in river water

Daily time series of phytoplankton concentration are theoretically analyzed with the use of population dynamics equation with fluctuations in the growth factor and environmental carrying capacity taken into account. The statistical distributions of phytoplankton cell concentration are shown to obey different laws, depending on the season of the year: lognormal in the winter and logarithmic in the vegetation period. The probability of extremely high concentration numbers is described by the normal law. The verification of the obtained relationships against a body of empirical data confirmed the theoretical forecasts. The obtained results make it possible to predict the probabilities of various phytoplankton concentration values within a wide range, including the domain of large values, which are of greatest hazard in terms of water quality, water treatment processes, and aquatic ecosystem well-being.

Erratum to: “Modeling the Biodegradation of Multicomponent Organic Matter in an Aquatic Environment: 4. Degradation Kinetics Model”

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.

Seasonal variations of the distribution of river water quality

The probability distributions of different values of water quality indices have been shown theoretically to follow a two-parameter lognormal law with season-dependent parameters. The obtained distribution law was checked against data of many-year water quality monitoring in the Moskva R. (at Rublevo Settl.). The distributions of several hydrochemical and microbiological indices have been studied. The seasonal dependence of parameters have been shown to cause the splitting of water quality index distributions predominantly into two lognormal branches, one corresponding to low-water seasons and the other corresponding to floods. Exceptions are water turbidity and color index: the former splits into three lognormal branches (corresponding to periods of winter low-water period, summer period with moderate rains, floods, and high rain floods), while the color index has only one branch, embracing all seasons.

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.

Modeling the Succession of Diatomic Complex under Growing Industrial Load on an Aquatic Ecosystem

Analysis of paleolimnological data on a part of Lake Imandra (Kola Peninsula), polluted by wastewaters discharged from a copper-nickel plant, is used to calculate the vertical profile of toxicity of bottom sediments and determine the response of dominant species of diatomic complex to the growing toxicity. The species are aggregated by the similar responses to the load. The dependence between the population sizes of diatom groups and toxicity is established. The diatom complex is shown to change its structure twice—at the toxicity exceeding the background level by factors of 1.2 and 3.2, respectively. A model is developed to describe variations in the species composition of the community under growing toxicity; the model is shown to be applicable to the analysis of paleolimnological data. General analysis of the model is given, and typical scenarios of variation in the number of species under growing toxic load are described.