The pollution of agricultural soil due to heavy metals is a serious environmental problem throughout the world due to their persistence and toxicity. The present study was carried out on agricultural soils of district Bathinda, Punjab where a total of 120 soil samples were collected from 40 different locations during pre-monsoon, monsoon, and post-monsoon season. The total mean concentration of heavy metals (arsenic (As), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), mercury (Hg), lead (Pb)) was estimated by ThermoScientific–iCAP Qc (Germany) inductively coupled plasma–mass spectrometry (ICP-MS). The concentration of heavy metals was of the order of Fe > Zn > Cr > Ni > Cu > Co > As > Pb > Hg > Cd, Fe > Zn > Cr > Ni > Cu > Co > As > Pb > Hg > Cd, and Fe > Zn > Cr > Ni > Cu > Co > Pb > As > Hg > Cd in pre-monsoon, monsoon, and post-monsoon seasons, respectively. The metals such as Fe, Zn, Cr, and Ni indicated higher concentrations at most of the sites, whereas Hg and Cd showed lower concentrations throughout the region. The total mean concentrations (mg/kg) of the metals were found to be lower than their natural background concentration values. Based on enrichment factor (EF), the soils were moderately contaminated at most of the sites with a few cases where the soil was minimally enriched with heavy metals. Other pollution indices such pollution load index (PLI) and degree of contamination (Cd) also indicated low to moderate level of soil contamination. Besides, risk assessment of heavy metals was also determined using potential ecological risk factor (Eᵢ) and ecological risk index (Rᵢ) which indicated low Eᵢ and Rᵢ in the region for most of the metals. Spatial distribution using interpolation technique, Inverse Distance Weighted (IDW) in ArcGIS 10.6.1 software, showed a significant spatial and seasonal variability of heavy metals throughout the region. Pearson’s correlation coefficient (r) between heavy metal variables was found to be significant at p < 0.05 significance level (As-Cr (r = 0.769), As-Fe (r = 0.760), As-Co (r = 0.883), As-Ni (r = 0.886), As-Cu (r = 0.859), As-Hg (r = 0.678) in pre-monsoon samples; As-Fe (r = 0.613), As-Co (r = 0.669), As-Ni (r = 0.619), As-Cu (r = 0.639) in monsoon samples and As-Cr (r = 0.631), As-Fe (r = 0.715), As-Co (r = 0.710), As-Cu (r = 0.690) in post-monsoon samples) indicated a strong relationship between different variables. Principal component analysis (PCA) technique also proved to be significant in studying the behavioral pattern of variables, where PCA biplots showed different behavior as revealed from some strong associations. Finally, continuous monitoring of the sites is suggested to avoid further contamination and degradation of soil quality, despite low contamination levels in the region.

Algae are widely distributed in the aquatic environment. In the analyzed algae from the Black Sea, metals like cadmium, iron, zinc, copper, lead, and thallium were present. From all of the analyzed elements in the algae, iron was present at the highest concentrations. The presented study confirmed that thallium is accumulated in relatively large quantities (1.60–2.12 μg g⁻¹) by all the studied algae. Cadmium and copper were accumulated at the same level (1.98 μg g⁻¹), which was lower in comparison to the average concentrations determined in the analyzed plant material. The average amounts of zinc were at 0.21 μg g⁻¹ for Ulva. High possibility of accumulation of metals by Ulva and Cystoseira allows to use them as a natural indicator of environmental cleanliness.

Aeromonas hydrophila, an opportunistic fish pathogen, which causes several major diseases including skin ulcer and haemorrhagic septicemia, contributes considerably to the lethality in aquaculture. Chemical and antibiotic treatment employed against A. hydrophila for disease management are expensive and consequently prompted the advent of drug resistance among the pathogens. To overcome these draw backs, alternative aquatic disease control methods using conventional plant-based medicines are focussed. Our present study aimed to augment the fish non-specific immune system with the implementation of methanolic crude extracts of Andrographis paniculata to Labeo rohita, for evaluating their efficacy against A. hydrophila. Histology of major organs of A. hydrophila-infected fish such as the gills and liver displayed severe tissue damage. A. paniculata extracts exhibited the strong antibacterial activity against A. hydrophila even at lower concentrations (50 μl). The extracts also altered the haematological profile of treated infected fishes by increasing the levels of haemoglobin and total erythrocyte-leucocyte counts, along with the phagocytic index. The extracts also had a significant impact on modifying the anatomy and swimming pattern of infected fish, post treatment with the extracts. Also, A. paniculata treated infected fishes in all the plant extract administration methods, viz. injection, oral feeding and diffusion, and reduced the cumulative mortality rate to less than 30%. Even lower concentrations of A. paniculata extracts (50 μl) resulted in maximum relative percentage survival of treated fishes. Therefore, our findings suggest that A. paniculata was effective against A. hydrophila infection in aquaculture, thereby maintaining a healthy status of these fishes in aquaculture.

Microplastics (MP) are transported from land-based sources from rivers to marine waters. However, there is currently little knowledge about MP fate from land sources to marine waters. Traffic is estimated to be one of the largest sources of MP; hence, stormwater is expected to be an important transportation route of MP to marine waters. The aim of this study was to investigate the effect of the size and density of tyre wear particles in road run-off on their fate in the Göta River in Sweden using hydrodynamic modelling. The model of the stretch of Göta River, Sweden’s largest river, passing through Gothenburg (Sweden’s second largest city) and out to the sea, was set up using MIKE 3 FM software. Literature data were used to define the MP characteristics: concentrations in stormwater, prevalent particle sizes, density of MP commonly occurring in road run-off and settling velocities. Results show that higher concentrations of MP are found on the south side of the river, compared with the north side, due to higher annual average daily traffic loads along the south side of the river. The mixing processes in the river and the MP concentrations were generally influenced by the vertical water density gradient caused by saline water from the Kattegat strait. While most MP with higher density and larger size settle in the river, smaller MP with density close to 1.0 g/cm³ do not settle in the river and therefore reach the Kattegat strait and the marine environments. Further research is needed to describe the fate and transport of microplastics in the stormwater system, including treatment facilities, i.e. biofouling, aggregation, degradation and/or further fragmentation and settling.

Lead (Pb) pollution in soil has become one of the most serious environmental problems, and it is more urgent in areas where acid rain is prevalent. Curing agents to solidify heavy metals in soil are efficiently applied to remediate Pb-contaminated soil. In this study, we prepared biochar, biochar loaded with nano-zero-valent iron (BC-nZVI), and biochar loaded with nano-ferroferric oxide (BC-nFe₃O₄), and investigated the Pb-immobilizing efficiency in contaminated soil in the condition of acid rain by them. The results showed that 8 g/kg is the best added dosage of curing agents for immobilizing Pb, which of the immobilizing efficiency of Pb were 19% (biochar), 42% (BC-nZVI), and 23% (BC-nFe₃O₄), respectively. Besides, the curing agents had positive effects on immobilizing Pb under acid rain condition, which could significantly reduce the content of acid extractable Pb, especially BC-nZVI (1.5%). And the immobilization efficiency of modified biochar was better than biochar, especially BC-nZVI (66%). BC-nZVI showed a more ideal effect on decreasing the leaching amount of Pb in the condition of acid rain. The results highlighted that biochar-loaded nano-iron-based materials, especially BC-nZVI, was promising and environmentally friendly materials for remediating Pb-contaminated soils, which provided scientific reference and theoretical basis for the treatment of Pb-contaminated soils around industrial sites particularly in acid rain area.

Restrictive requirements for maximum concentrations of metals introduced into the environment lead to search for effective methods of their removal. Chemical precipitation using hydroxides or sulfides is one of the most commonly used methods for removing metals from water and wastewater. The process is simple and inexpensive. However, during metal hydroxide precipitation, large amounts of solids are formed. As a result, metal hydroxide is getting amphoteric and it can go back into the solution. On the other hand, use of sulfides is characterized by lower solubility compared with that of metal hydroxides, so a higher degree of metal reduction can be achieved in a shorter time. Disadvantages of that process are very low solubility of metal sulfides, highly sensitive process to the dosing of the precipitation agent, and the risks of emission of toxic hydrogen sulfide. All these restrictions forced to search for new and effective precipitants. Potassium/sodium thiocarbonate (STC) and 2,4,6-trimercaptotiazine (TMT) are widely used. Dithiocarbamate (DTC) compounds are also used, e.g., sodium dimethyldithiocarbamate (SDTC), and ligands for permanent metal binding, e.g., 1,3-benzenediamidoethanethiol (BDETH₂), 2,6-pyridinediamidoethanethiol (PyDET), a pyridine-based thiol ligand (DTPY) or ligands with open chains containing many sulfur atoms, using of a tetrahedral bonding arrangement around a central metal atom. The possibility of improving the efficiency of metal precipitation is obtained by using a higher dose of precipitating agent. However, toxic byproducts are often produced. It is required that the precipitation agents not only effectively remove metal ions from the solution but also effectively bind with dyes or metal complexes.

The catalytic oxidation of volatile organic compounds (VOCs) has been studied in a series of bimetal (Fe-Co)-incorporated ZSM-5 zeolites. The bimetal incorporation was varied. The first sample was prepared by an in situ hydrothermal synthesis method (named IHT) in which both metals were added simultaneously during gel formation. The second sample was made by preparing Fe-ZSM-5 in situ and then impregnated with Co (named FIC), while the third sample was the reverse of the second sample (Co-ZSM-5 impregnated with Fe; named CIF). The objective was to find a method that yields a catalyst with high activity towards complete removal and oxidation of VOCs and is stable. All three synthesized catalysts were thoroughly characterized by modern instrumental methods, such as X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared analysis, inductively coupled plasma optical emission spectroscopy, N₂ adsorption-desorption analysis, and BET surface area. From the results, it is clear that the IHT sample has the best characteristics for the removal of VOCs and is more stable.

Water is one of the receptors media more affected by the environmental impacts, especially caused by mining sulfides exploitation. Acid mine drainage (AMD) is the main problem associated with these mining operations, producing extremely high impacts, and in many cases irreversible, still remaining nowadays. Diatoms, are the taxonomic algal group most used in environmental studies, to assess the water quality of rivers. From a monitoring perspective, the diagnosis of AMD contamination through the use of diatoms has proved to be an effective ecological tool to assess the impact and select the preventive and corrective measures more adequate to treat these impacted sites. In the present work, the existing relationships between biological and physicochemical indicators of acid mine drainage processes (AMD) in all the reservoirs affected by AMD in the Iberian Pyrite Belt (IPB) were studied through the use of fuzzy logic and data mining techniques that in contrast to the classic statistical treatments. The fuzzy rules show the relationship between biological and physical-chemical indicators, demonstrating the presence of a perfect correlation in all cases; thus, the numbers of species and pH have the same behavior, and inverse to that presented by the percentage of Pinnularia and the metallic charge and sulfates. These techniques improve the work considerably and make easier the knowledge of the involved processes, allowing a better discrimination of the diatoms responses to the stimuli caused by the hydrochemical changes imposed by the processes affecting water quality.

Anabaena flos-aquae, a typical species of cyanobacterial bloom, was employed as a useful biosorbent for uranium removal. Batch experiments were conducted to examine the effects of different parameters on the uranium uptake amount of Anabaena flos-aquae. The maximum adsorption capacity of 196.4 mg/g was obtained under the optimized experimental conditions. The calculations of kinetic and thermodynamic results proved the adsorption process was endothermic, chemisorption, and spontaneous. The adsorption of uranium onto Anabaena flos-aquae was better defined by the Langmuir model, which indicated the process was a monolayer sorption. In addition, the characterization of the biosorbent before and after uranium sorption implied that the dominant functional groups participated in the uranium adsorption process were hydroxyl, amino, and carboxyl. In conclusion, the environmentally friendly and biocompatible characteristics of Anabaena flos-aquae suggest that it can be a promising biosorbent for uranium removal.

Microcystis is a frequent cyanobacterium bloom-forming with cosmopolitan distribution which can produce a hepatotoxin group called microcystins (MCs). These MCs are resistant to the traditional processes employed in the water treatment plants and they are often detected after conventional treatments. Because of this, the bio-removal studies have obtained a great interest in the last decades. In this work, a bacterial strain namely LG1 with the ability to remove microcystin-LR (MC-LR) under laboratory conditions was isolated from Rio de la Plata River and it was identified as Achromobacter spp. This ubiquitous bacterium was able to remove 79.5% MC-LR in 7 days with average removal time of 3.33 ± 0.08, 3.06 ± 0.05, and 2.77 ± 0.05 days at 28, 32, and 36 ± 1 °C, being higher at high temperature (36 °C) with an activation energy = 16.79 ± 1.99 kJ mol⁻¹. LG1 grew better at higher temperature (from 28 to 36 ± 1 °C) increasing the specific growth rate (μ) and reducing 2-fold the lag phase duration (LPD) without significant differences (p > 0.05) between maximum population density (MPD). In addition, LG1 showed a lysis activity on two M. aeruginosa native strains in 7 days measured as chlorophyll a (Chl-a) concentration. The lysis activity increased around 2-fold when increasing the temperature from 28 to 36 ± 1 °C. This is the first report of an indigenous bacterium belonging to the genus Achromobacter spp. isolated from the Rio de la Plata River with the capacity to remove MC-LR and lysis activity on M. aeruginosa.