Coastal areas are facing increasing heavy metal pollution as a result of various anthropogenic activities, posing a serious threat to ecosystems. Modeling and understanding the sorption behavior of heavy metals in soils are essential for assessing their mobility and risk in the coastal landscapes. The aim of this study was to examine the adsorption behavior of Pb²⁺, Ni²⁺, and Zn²⁺ by common soil types of the Lower Don and the Taganrog Bay coast in Russia to better understand their potential environmental implications. The soil capacities for heavy metal adsorption and retention were determined using isothermal models. The maximum adsorption capacity and the binding strength parameter for the heavy metals were calculated, revealing significant differences among the soils. Haplic Chernozem emerged with superior values, while Gleyic Solonchak Sulfidic and Umbric Fluvisol trailed the lowest. All soils exhibited a greater adsorption capacity and binding strength for Pb compared to the other metals. The influence of soil characteristics on sorption and retention was also examined. The Pseudo-second-order model provided a more accurate description of the adsorption kinetics of heavy metals by the studied soils. The co-presence of metals in the system affected their sorption by the soils due to competition: soils adsorbed fewer metals but retained them more strongly. These findings are important for developing effective strategies to reduce heavy metal pollution in coastal ecosystems.

An important goal in environmental research for industrial activity and sites is the investigation and development of effective adsorbents for chemical pollutants that are widespread, inexpensive, unharmful to the environment, and have the required adsorption selectivity. Organoclays are adsorption materials that can be obtained by modifying clays and clay minerals with various organic compounds through intercalation and surface grafting. Organoclays have important practical applications as adsorbents of a wide range of organic pollutants and some inorganic contaminants. The traditional raw materials for the synthesis of organoclays are phyllosilicates with the expanding structural cell of the smectite group, such as montmorillonite. Moreover, other phyllosilicates and inosilicates are used to synthesize organoclay to a limited extent. The purpose of this review was to analyze the possibility of using minerals of other groups with different abilities to expand the structure and structural charge for the adsorption of chemical environmental pollutants. The structural characteristics of various groups of phyllosilicates and chain minerals that affect their ability to modify organic surfactants and the adsorption properties of prepared organoclays were reviewed.

Concentrations and depth distribution of the total content and forms of trace elements in fluvisols with different technogenic load were studied. Alluvial soddy saturated soil of the Oka river (Moscow region) was studied as soils with a low technogenic load. Increased concentrations of metals in the background fluvisol are observed in the riverbed floodplain, which indicates their entry during floods. In the fluvisol near the industrial center, the concentration of trace elements may not exceed hygiene standards due to their intensive removal from the landscape. Agricultural use can cause uniform depth distribution of total and mobile forms of the elements. Thus, the concentrations, depth distribution and speciation of trace elements in fluvisols with different technogenic loads depend not only on the scale of this load but also on the soil properties and the ratio of the processes of element input to and removal from the soils.

Phyto- and bioremediation are perspective methods for soil recultivation. In spite of resistance of plant-hyperaccumulators and degrading microorganisms to some contaminants, there are soil toxicity limits for their growth and activity. Therefore, simple and express methods are needed to estimate the soil phytotoxicity. This article is devoted to description of an express-phytotest evaluated by germination rate of white clover (Trifolium repens) (PhCG) for estimating phytotoxicity of contaminated soils. This phytotest was developed on the example of grey forest soil contaminated with diesel fuel or copper(II) and approbated during our long-year experiments on adsorptive bioremediation of petroleum-contaminated soils. The sensitivity of the phytotest values PhCG to these contaminants is much higher compared to those phytotests evaluated by germination of larger seeds: cress (Lepidium sativum), and wheat (Triticum vulgare). A significant increase of PhCG in those soils by 10% was already recorded at 50–100 mg of available Cu2+ kg−1 and 1–5 g total petroleum hydrocarbons kg−1, depending on the hydrocarbon composition. The sensitivity of the standard phytotests evaluated by root length of wheat seedlings or by plant (T. vulgare or T. repens) biomass is higher than that of PhCG determination. However, bio- and phytoremediation are mostly applied for heavily contaminated soils. Therefore, use of the simple and cheap express phytotest for choosing optimal conditions of the soil remediation and following the process is quite justified. Besides, measuring an additional parameter—root length of the white clover seedlings may significantly increase the sensitivity of the express phytotest for lower contaminated soils.

Humic substances with or without chemical modification can serve as environmentally benign and inexpensive adsorbents of potentially toxic trace elements (PTTEs) in the environment. The present study investigated the absorption of Pb, Zn, Cu and Ni by natural and potassium persulfate (K2S2O8) modified humic acids (HAs) isolated from a lowland peat through batch experiments. The adsorption of the studied PTTEs on the natural HA was satisfactorily described by the Langmuir isotherm model with maximum monolayer adsorption capacities of 318.2, 286.5, 225.0 and 136.8 mmol/kg for Pb, Cu, Zn and Ni, respectively. A thorough characterization of the natural and modified HA using(13)C nuclear magnetic resonance spectroscopy demonstrated that the chemical modification of natural HA with K(2)S(2)O(8)led to an increase in the content of carboxyl groups, and ketone and quinoid fragments in the HA structure. Consequently, the modified HA absorbed 16.3, 14.2, 10.6 and 6.9% more Pb, Ni, Zn and Cu, respectively, than the original natural HA. The isotherm data modeling together with adsorbent characterization suggested that the adsorption of PTTEs was controlled mainly by chemisorption mechanisms where inner-sphere complexations of metal ions with HA functional groups took place.

The article presents the results of a study of the effect of the carbon sorbent of granular activated carbon on the physical properties of soils under conditions of copper pollution. The use of activated carbon has a positive effect on accelerating the process of restoring the physical properties of the soil, due to the high pore space and the specific surface of the sorbent. The structural state improves, and the waterholding ability increases.

The parameters of Cu2+, Pb2+ and Zn2+ adsorption by chernozems of the south of Russia and their particle-size fractions were studied. The adsorption capacity of chernozems for Cu2+, Pb2+, and Zn2+ depending on the particle-size distribution decreased in the following sequence: clay loamy ordinary chernozem ~ clay loamy southern chernozem > loamy southern chernozem > loamy sandy southern chernozem. According to the parameters of the adsorption by the different particle-size fractions (Cmax and k), the heavy metal cations form a sequence analogous to that obtained for the entire soils: Cu2+ ≥ Pb2+ > Zn2+. The parameters of the heavy metal adsorption by similar particle-size fractions separated from different soils decreased in the following order: clay loamy chernozem > loamy chernozem > loamy sandy chernozem. The ratio between the content of exchangeable cations displaced from the soil adsorbing complex (SAC) into the solution and the content of adsorbed HMs decreased with the increasing concentration of adsorbed HMs. These values could be higher (for Cu2+ and Pb2+), equal, or lower than 1 (for Zn2+) and depend on the properties of HMs. At the first case, this was due to the dissolution of readily soluble salts at low HM concentrations in the SAC. In the latter case, this was related to the adsorption of associated forms HMs and the formation of new phases localized on the surface of soil particles at high HM concentrations in the SAC.