The full understanding of the effect of mineral waste-based fertilizer in soil is still unrelieved, because of the extreme complex chemical composition and plethora of their action pathways. The purposes of this paper is to quantify the input of PG into the soil ecosystem process, considering the direct effects of PG as a whole on soil environment using of a plethora of chemical, toxicological, and biological tests.
Materials and methods
Greenhouse experiment includes different PG doses (0, 1%, 3%, 7.5%, 15%, 25%, and 40%) and two-time collection points after treatments—7 and 28 days. For each treatment and each time collection point, we measure (i) soil pH, bioavailable (H20 and NH4COOH-extractable) element content (S, P, K, Na, Mg, Ca, Fe, Zn, Sr, Ba, F); (ii) soil enzyme activities—dehydrogenase, urease, acid phosphatase, FDA; (iii) soil CO2 respiration activity with and without glucose addition; (iv) Eisenia fetida, Sinapis alba, and Avena sativa responses. Finally, we combine the ordinary chemical, toxicology, and biological measuring of soil properties with state-of-the-art mathematical analysis, namely (i) support vector machines (used for prediction), (ii) mutual information test (variable importance tasks), (iii) t-SNE and LLE algorithms (used for unsupervised classification).
Results and discussion
The results show similarity between the 0%, 1%, and 3% PG treatments in all collection times based on the toxicological and biological properties. Beyond 7.5% PG, some biological test was significantly inhibited in response to trace element stress. Among all tested parameters, soil urease activities, soil respiration activities after glucose addition, S. alba root lengths, and E. fetida survival rates show sensitivity to PG addition. Furthermore, the machine learning algorithms revealed that only several elements (mobile and water-soluble forms of Ca, Ba, Sr, S, and Na; water-soluble F) could be responsible to elevated soil toxicity for those indicators. SVR models were able to predict soil biological and ecotoxicity properties, and increasing numbers of randomly selected training examples from 50 to 90% of initial experimental data significantly improved model performance.
Conclusions
At this study, we demonstrate benefits of unsupervised machine learning methods for investigating toxicity of man-made substances in soil that can be further applied to risk assessments of various toxins, which are of significant interest to environmental protection.
The study of interactions between humic substances (HSs) and soil filamentous fungi is the key to understanding the sustainable soil functioning. The present work aims to examine the decomposition of HSs by filamentous dark-pigmented fungus Alternaria alternatа under the laboratory conditions and to determine the effect of easily assimilable organic carbon on this process. Analyzing such polydisperse substances like HSs by a complex integrated methodology makes it possible to explore the data on their decomposition by microorganisms.
Materials and methods
To achieve the aforementioned goals, we used chromatographic and spectroscopic approaches: low-pressure size-exclusion and hydrophobic interaction chromatography accompanied by absorption and fluorescence spectroscopy. To determine the effect cometabolism conditions produced on HS decomposition, two types of carbon substrates were added to the nutrient media: easily assimilable organic carbon (standard 0.3% or reduced 0.03% sucrose content) and hardly assimilable organic carbon (HSs), as well as their combinations. Five HS samples of different organic matter origin have been inspected: potassium humates (HPs) and humic acids (HAs) from coal, peat, and lignosulfonate. Correlation matrix and principal component analysis (PCA) were calculated for comprehensive data analysis.
Results and discussion
Transformations of the investigated HSs under fungal cultivation lead to the increase in the low molecular weight fraction, rise of hydrophilic fraction, enlargement of absorbance ratio A250/A365, shortening of the emission wavelength of the humic-type fluorescence, and growth in the fluorescence quantum yield measured with excitation at 355 nm. A positive correlation was observed between the accumulation of fungal biomass and the degree of HS decomposition. PCA analysis confirms that the difference in the results of HS decomposition largely depends on the sucrose content and the nature of HSs. We divided all the HS samples into four groups according to the degree of HS decomposition: original HS solutions, HPs altered using fungal cultivation at 0.03% sucrose, HAs after fungal cultivation at 0.03% sucrose, and finally, HSs (both HPs and HAs) after fungal cultivation at 0.3% sucrose.
Conclusions
In the laboratory experiments, we showed that (1) the isolated HAs were more effectively degraded than the parent HPs, and this process was more pronounced at a reduced sucrose content, and (2) the decomposition of stable organic compounds (HSs) was activated by the easily assimilable carbon sources (especially 0.3% sucrose) being present. We assume that it is the easily assimilable organic carbon that most likely triggers the HS degradation working as the priming effect in natural environments.
Heavy metal contamination is a priority issue affecting millions of hectares of soil throughout the world. One of the most promising, environmentally friendly, and cost-effective approaches to restore polluted soils could be applying organic amendments. We investigated the remediation potential of three types of humic products with regard to their effect on the bioavailability of Pb and Zn, content of nutrients, and the ability to mitigate acute phytotoxicity in contaminated soil.
Materials and methods
Spodosol samples were spiked with Pb (550 mg kg?1) and Zn (880 mg kg?1). Then, two different commercial humic products (from peat and lignosulfonate) and natural humic acids (from brown oxidized coal) were added in two doses to reach an equal content of carbon: a 10% increment and a 30% increment of the initial total organic carbon in the soil. After 30 days, the content of metals and nutrients (S, K, Na, Ca, Mn, P) was determined by the sequential extraction (i?H2O, ii?NH4COOH pH 4.8, iii–CH3COOH). The effect of humic products on heavy metals bioavailability was evaluated using the calculated partition indexes. Seed germination and root elongation of Sinapis alba were also determined. Chemical and biochemical variables were aggregated by the principal component analysis.
Results and discussion
Humic products reduced the amount of bioavailable fractions of Pb and Zn in soils. The partition index, which quantitatively describes bioavailable fractions of the Zn and Pb in the soil, was 28–49% lower than in the spiked (Pb+Zn) control. The inhibition of root elongation and seed germination of mustard by Zn and Pb was significantly mitigated by humic products; in the soil test, the root length and seed germination were up to 36–87% higher than those of the Pb+Zn control and did not differ from those in the non-amended treatments. This effect may have been associated with the structural differences (H/C and O/C ratio) and content of nutrients (Na and K) in humic products.
Conclusions
Commercial humic products used in poor multi-contaminated soils can maintain plant growth by improving nutrient status due to heavy metals immobilization and can be a promising approach to remediate the soil contaminated with heavy metals at extremely high concentrations.
Analysis of methodological documents, Russian and foreign standards, and scientific publications has been performed to reveal best global practices and current trends in the improvement of laboratory phytotesting. It is proposed to increase the number of simultaneously used test cultures and the range of simultaneously controlled test functions at the first (screening) stage of phytotest to increase the information value of laboratory phytotests. Attention is focused on the assurance of the statistical reliability of test results. The advisability of creating universal regulations of Russian Federation for phytotesting methods to unify approaches to the ecological evaluation of soils. 相似文献
Studies on the occurrence and potential effects of nanomaterials (NMs) in the environment are analyzed. Mechanisms of action of some of the well-known nanotechnological products on test cultures are discussed. Attention is focused on the problems of determination of the ecotoxicity of NMs in soils in relation to their instability and variability in the environmental conditions. Our data indicate that the effect of the interactions between the nanoparticles should be taken into consideration in econanotoxicological studies. The formation of aggregates at high concentrations of nanoparticles and an increase in the content of free nanoparticles upon dilution largely explain the inverted dose-response ratio, or the U-shaped curve describing this relationship in the analysis of dispersed systems. Problems in the development of an assessment system for the effect of NMs on environments, including soils, are also discussed. Presently, there are no standards for assessing NMs, and approved Russian and international procedures for checking the sensitivity of standardized test organisms are used. However, the imperfection of the approaches to the analysis of NMs toxicity gives no ground for hampering the development of nanotechnologies for nature conservation purposes. 相似文献
An attempt to set up ecologically acceptable concentrations of toxic components contained in phosphogypsum was made for soils of different land uses. For this purpose, an experimental ecological evaluation of a standard soil mixture (model artificial soil ISO 11268-1) treated with phosphogypsum was performed. Both positive and negative effects of the phosphogypsum components were found. Thus, a significant increase in the biomass of lawn grasses was observed in the model soil with the phosphogypsum content of less than 3.3%. In the soil containing more than 6.8% phosphogypsum, the concentrations of Sr and F exceeded the maximum permissible values and adversely affected the living organisms. According to the basic ecological norms, the allowable content of phosphogypsum should be ≤2.0% for the soils of specially protected natural areas; ≤6.8% for agricultural and urban soils; and ≤9.6% for the soils of forest, water management, and transport lands. 相似文献
The methodological and organizational problems of the practical application of soil bioassay to monitor the state of soils
for environmental, agricultural, and sanitary-epidemiological purposes are analyzed. To improve the efficiency of the integral
valuation of soil toxicity, soil bioassay should be performed with a set of organisms (sensors) representing the major trophic
levels of the ecosystems, i.e., producers, consumers, and decomposers. 相似文献
The “triad” approach was suggested by Chapman [22] for assessing the risk of contamination of bottom deposits. We applied this approach for the analysis of urban soils under different loads from motor transport. On its basis, the results of chemical analysis (heavy metals, biogenic elements, and pH), bioindication parameters of the communities of microorganisms, and the results of toxicological investigations with the use of test-organisms were generalized to obtain an integral index of the soil status (IS). A comparison of IS values for test plots at different distances from a highway in the city of Kirov (58.3729–58.624722 N, 49.3743–49.628611 E) showed that the ecological status of the soils could be qualified as disturbed on the plots adjacent to the highway and as slightly disturbed at distances of 30–200 m from the highway. The IS calculated on the basis of data of three disciplines (chemistry, ecology, and toxicology) seems to be a more comprehensive characteristic for assessing the ecological status of urbanozems as compared to Zc indices of the chemical contamination of soils (suggested by Saet) or indices of the integral biological characteristics of soil quality. 相似文献
A number of structural and functional parameters of microbial communities have been applied for ecological monitoring of soils
located in nearby landfills. The difference in sensitivities to pollution between different microbial indices was shown. A
landfill impact zone in the direction of pollution migration was established using the total disturbance index of habitat
microbial communities. 相似文献
