Nanoplastics (NPs) are becoming emerging pollutants of global concern. Understanding the environmental behavior of NPs is crucial for their environmental and human risk assessment. In this study, the aggregation and stability of polystyrene (PS) NPs were investigated under different hydrochemical conditions such as pH, salt type (NaCl, CaCl₂, Na₂SO₄), ionic strength (IS), and natural organic matter (NOM). The critical coagulation concentrations of PS NPs were determined to be 158.7 mM NaCl, 12.2 mM CaCl₂, and 80.0 mM Na₂SO₄. Ca²⁺ was more effective in destabilizing PS NPs, compared to Na⁺, owing to its stronger charge screening effect. In the presence of monovalent ions, NOM reduced aggregation through steric repulsion, whereas in the case of divalent ions, NOM induced aggregation through cation bridging. Initial and long-term stability studies demonstrated that, in waters with high IS and NOM content, NOM was the most significant factor affecting NPs aggregation. PS NPs would be highly suspended in all freshwaters, and even in wastewater, whereas they would aggregate rapidly and deposit in seawater. Finally, a statistical model was established to evaluate the hydrodynamic diameter of NPs in different waters. The results indicated the stability of PS NPs in natural aquatic environments and their potential for long-term transport.

Private wells in Ireland and elsewhere have been shown to be prone to microbial contamination with the main suspected sources being practices associated with agriculture and domestic wastewater treatment systems (DWWTS). While the microbial quality of private well water is commonly assessed using faecal indicator bacteria, such as Escherichia coli, such organisms are not usually source-specific, and hence cannot definitively conclude the exact origin of the contamination. This research assessed a range of different chemical contamination fingerprinting techniques (ionic ratios, artificial sweeteners, caffeine, fluorescent whitening compounds, faecal sterol profiles and pharmaceuticals) as to their use to apportion contamination of private wells between human wastewater and animal husbandry wastes in rural areas of Ireland. A one-off sampling and analysis campaign of 212 private wells found that 15% were contaminated with E. coli. More extensive monitoring of 24 selected wells found 58% to be contaminated with E. coli on at least one occasion over a 14-month period. The application of fingerprinting techniques to these monitored wells found that the use of chloride/bromide and potassium/sodium ratios is a useful low-cost fingerprinting technique capable of identifying impacts from human wastewater and organic agricultural contamination, respectively. The artificial sweetener acesulfame was detected on several occasions in a number of monitored wells, indicating its conservative nature and potential use as a fingerprinting technique for human wastewater. However, neither fluorescent whitening compounds nor caffeine were detected in any wells, and faecal sterol profiles proved inconclusive, suggesting limited suitability for the conditions investigated.

Freshwater salinization is a rapidly emerging ecological issue and is correlated with significant declines in aquatic biodiversity. It remains unclear how changing salinity regimes affect the physiology of sensitive aquatic insects. We used the parthenogenetic mayfly, Neocloeon triangulifer, to ask how ionic exposure history alters physiological processes and responses to subsequent major ion exposures. Using radiotracers (²²Na, ³⁵SO₄, and ⁴⁵Ca), we observed that mayflies chronically reared in elevated sodium or sulfate (157 mg L⁻¹ Na or 667 mg L⁻¹ SO₄) had 2-fold (p < 0.0001) and 8-fold (p < 0.0001) lower ion uptake rates than mayflies reared in dilute control water (16 mg L⁻¹ Na and 23 mg L⁻¹ SO₄) and subsequently transferred to elevated salinities, respectively. These acclimatory ion transport changes provided protection in 96-h toxicity bioassays for sodium, but not sulfate. Interestingly, calcium uptake was uniformly much lower and minimally influenced by exposure history, but was poorly tolerated in the toxicity bioassays. With qRT-PCR, we observed that the expression of many ion transporter genes in mayflies was influenced by elevated salinity in an ion-specific manner (general upregulation in response to sulfate, downregulation in response to calcium). Elevated sodium exposure had minimal influence on the same genes. Finally, we provide novel light microscopic evidence of histomorphological changes within the epithelium of the Malpighian tubules (insect primary excretory system) that undergoes cellular degeneration and necrosis secondary to calcium toxicity. We conclude that physiological plasticity to salinity stress is ion-specific and provide evidence for ion-specific toxicity mechanisms in N. triangulifer.

Environmental contaminants affect ecosystems worldwide and have deleterious effects on biota. Non-essential mercury (Hg) and lead (Pb) concentrations are well documented in some taxa and are described to cause multiple detrimental effects on human and wildlife. Additionally, essential selenium (Se) is known to be toxic at high concentrations but, at lower concentrations, Se can protect organisms against Hg toxicity. Crocodilians are known to bioaccumulate contaminants. However, the effects of these contaminants on physiological processes remain poorly studied. In the present study, we quantified Hg, Pb and Se concentrations in spectacled caimans (Caiman crocodilus) and investigated the effects of these contaminants on several physiological processes linked to osmoregulatory, hepatic, endocrine and renal functions measured through blood parameters in 23 individuals. Mercury was related to disruption of osmoregulation (sodium levels), hepatic function (alkaline phosphatase levels) and endocrine processes (corticosterone levels). Lead was related to disruption of hepatic functions (glucose and alanine aminotransferase levels). Selenium was not related to any parameters, but the Se:Hg molar ratio was positively related to the Na⁺ and corticosterone concentrations, suggesting a potential protective effect against Hg toxicity. Overall, our results suggest that Hg and Pb alter physiological mechanisms in wild caimans and highlight the need to thoroughly investigate the consequences of trace element contamination in crocodilians.

To evaluate the heavy metal contamination and groundwater quality in southern Saudi Arabia, 105 groundwater samples were analyzed for EC, pH, TDS, major ions (NO₃⁻, Cl⁻, HCO₃⁻, SO₄²⁻, F⁻, Ca²⁺, Mg²⁺, Na⁺, and K⁺), and heavy metals (Fe, Li, As, B, Al, Cr, Cu, Mo, Ni, Se, Sr, V, Zn, and Mn). Groundwater quality index (GWQI), degree of contamination (Cd), heavy metal pollution index (HPI), ecological risks of heavy metals (ERI), salinity hazard (EC), sodium adsorption ratio (SAR), sodium percentage (Na%), and Kelly's ratio (KR) were calculated and compared, and multivariate statistical techniques were applied. The results revealed that the major cations and anions followed the orders of Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and Cl⁻ > SO₄²⁻ > HCO₃⁻ > NO₃⁻ > F⁻, respectively. The maximum values of As, Mn, Cr, Ni, Se, and Zn were above the permissible limits for drinking water purposes. Pollution indices indicated that 20 to 52% of the groundwater samples were suitable for agricultural and domestic purposes. The unsuitable samples were distributed mostly in the western part along the Red Sea coast. Multivariate statistical analyses revealed that the dissolution of halite and gypsum (in sabkha deposits), carbonates, and the agricultural activities were the possible sources of the major cations and anions, and heavy metals in the study area.

Several industrial by-products may be used as amendments to reduce arsenic availability in contaminated areas, hence contributing to phytoremediation processes. This study was conducted aiming to evaluate red mud (RM) and a mixture containing 75% of RM + 25% of phosphogypsum (PG) (hereafter, RMPG) as amendments in arsenic-contaminated soils presenting distinct properties, like clay and organic matter content and chemical composition. Two contrasting soils were artificially contaminated with 150 mg dm³ of arsenic and after that cultivated with Urochloa brizantha. The experiment was carried out using a Typic Dystrudox (LV, 750 g kg⁻¹ clay) and a Typic Quartzipsamment (RQ, 70 g kg⁻¹ clay), with the following RM and RMPG rates: 0, 0.5, 1.0, and 2.0% (w/v). Also, limestone was tested as an additional amendment for comparison. Hydrogen potential (pH), electrical conductivity (EC), sodium, and arsenic concentrations were analyzed on leachates, and the dry matter production of Urochloa brizantha and arsenic concentration in plant root and shoot dry matter were also recorded. The amendments increased pH, EC, and sodium concentration and the addition of RMPG decreased the arsenic concentration on leachates. RMPG increased plant dry matter production and decreased arsenic concentration in the plant’s shoot. The plant resistance to arsenic contamination was influenced by soil properties, with arsenic toxicity being more evident in the sandy soil (RQ) compared with the clayey soil (LV). The mixture (RMPG) has shown to be an advantageous amendment since, besides decreasing arsenic availability, it also furnishes the nutrients calcium and sulfur from the PG.

Salinity harms crop productivity; thereby, the management of salt-affected soils is a prerequisite to obtaining optimum crop yields and achieving UN-SDGs. The application of bio-organic amendments is an eco-friendly and cost-effective technique for the management of salt-affected soils. Therefore, this study examined the effect of salt-tolerant Bacillus subtilis strain Y16 and biogas slurry (BGS) on growth, physiology, and yield of sunflower under salt-affected soil conditions. Three levels of soil salinity (original electrical conductivity (EC): 3 dS m⁻¹; induced EC: 6 dS m⁻¹ and 8 dS m⁻¹) were evaluated against three levels of BGS (0 kg ha⁻¹, 600 kg ha⁻¹, and 800 kg ha⁻¹) with and without bacterial inoculation. Soil salinity (EC = 8 dS m⁻¹) significantly (P < 0.05) increased Na⁺ contents (86%), which significantly (P < 0.05) reduced growth (17–56%), physiology (39–53%), and yield (58%) of sunflower. However, the combined application of BGS and B. subtilis alleviated salt stress and significantly (P < 0.05) improved sunflower growth (11–179%), physiology (10–84%), and yield (106%). The correlation analysis showed the superiority of B. subtilis for inducing salt-stress tolerance in sunflower as compared to BGS through homeostasis of K⁺/Na⁺ ratio. The tolerance indices and heat map analysis revealed an increased salt-stress tolerance in sunflower by the synergistic application of BGS and B. subtilis at original (3 dS m⁻¹) and induced (6 dS m⁻¹) soil salinity. Based on the results, we conclude that the combined application of B. subtilis and BGS enhanced growth and yield of sunflower by improving physiological processes and adjustment of K⁺/Na⁺ ratio in shoot under moderate salt-stress soil conditions.

Scarcity of freshwater resources for agricultural purposes is a crucial problem in arid and semi-arid regions. The aim of this study was to evaluate the effects of Moringa seed powder on wastewater quality parameters and examine the responses of Leucaena leucocephala seedlings irrigated with Moringa-treated wastewater. Moringa seed powder was used for different wastewater types (gray, primary-, and tertiary-treated wastewater). Wastewaters were treated with Moringa seed powder using the following concentrations: 0.2, 0.4, and 0.8 g/L. The analyses of wastewaters before and after treatment with Moringa seed powder were conducted, and its impact on seed germination and seedling growth of Leucaena leucocephala was investigated using Moringa-treated wastewater. Our results revealed that Moringa seed powder decreased pH and increased electrical conductivity, phosphate, nitrate, and ionic abundance of calcium, magnesium, sodium, and potassium in the treated wastewater as Moringa seed powder concentration increases. Both germination rate index and percentages were not significantly different for treated wastewater as compared to control. However, the treatment showed the highest percentage at 0.8 g (95%) using M. oleifera compared to 0.2 g (86.3%) with M. peregrina. On the other hand, seedling characteristics of Leucaena leucocephala improved for both treatments. Shoot heights and root lengths were the highest at concentrations 0.2 g (10.48 and 7.28 cm, respectively) and 0.8 g (10.51 and 7.22 cm, respectively) for both M. peregrina and M. oleifera. Finally, Moringa seed powder improved the plant productivity using M. oleifera, while slight decline in plant height with M. peregrine was shown compared to control.

Sustainable management of groundwater resources requires detailed basin-wide water assessments. Semi-urbanized areas surrounding metropolitan cities in the western part of India were assessed for their suitability for domestic, irrigation, and industrial purposes. These study areas reflect rapid urban growth with residential complexes, combined with agricultural, horticultural, and industrial uses. Therefore, 68 representative groundwater samples were collected during the pre-monsoon (PRM) and post-monsoon (POM) seasons of 2015 and analyzed for major ions. According to the World Health Organization (WHO) drinking standards, parameters like EC, TDS, TH, HCO₃, Ca, and Mg were found to exceed the desirable maximum limits, and the B and F content exceeded the permissible limits. The drinking suitability was studied using the modified water quality index (MWQI). The irrigation suitability was assessed using indices such as sodium adsorption ratio (SAR), percent sodium (%Na), and permeability index (PI). The industrial suitability was evaluated based on Langelier saturation index (LSI), saturation index (SI), Ryznar stability index (RSI), etc. MWQI results corroborate that 52.94 and 70% samples fall in no pollution category, and 47% and 30% samples were identified to be in the moderate category of pollution in the PRM season and POM season, respectively. The spatial variation maps of LSI, SI, RSI, Puckorius scaling index (PSI) and Larson–Skold index (LaI) show that the majority of the samples in the PRM season have low to insignificant scaling and corrosive potentials as compared to POM samples. The study results provide reliable information for water reserve managers to prepare the sustainable and more accurate basin management plans.

The current was conducted to evaluate the ameliorating effect of Chlorella vulgaris (CV) extract against sodium nitrite-induced hepatotoxicity in rats. Forty-five rats were allocated randomly into 5 groups (n = 9). Group I (GI), control group: orally gavaged with normal saline daily. Group II (GII): orally gavaged with CV extract (70 mg/kg BW) for 3 months. Group III (GIII): orally gavaged with sodium nitrite (80 mg/kg BW) for 3 months. Group IV (GIV): received sodium nitrite as GIII and CV extract as GII simultaneously for 3 months. Group V (GV): received CV extract as GII and then, sodium nitrite as in GIII from the end of first month until the end of the experiment. Sodium nitrite significantly increased the activities of serum alanine aminotransferase, aspartate aminotransferase, and serum concentrations of tumor interleukin 1-β and necrosis factor α. In addition, it increased concentrations of malondialdehyde and nitric oxide and expression level of caspase-3 in the hepatic tissue. However, it decreased activities of hepatic glutathione peroxidase, catalase, and superoxide dismutase and induced degenerative and necrotic changes in hepatic tissues. In contrast, CV extract administration modulated sodium nitrite-induced inflammation, oxidative stress, and alteration in hepatic tissue function and architecture. This study indicated that CV extract modulated sodium nitrite-induced hepatic toxicity through decreasing oxidative stress and inflammation and enhancing antioxidant enzyme activities in hepatic tissue of rats.