Dissipation of twelve organic micropollutants in three different soils: Effect of soil characteristics and microbial composition

Impact of the wastewater treatment technology and storage on micropollutant profiles during reclaimed water irrigation: A wide-scope HRMS screening in a water-soil-lettuce-leachate system

In recent decades, climate change and global warming have intensified water scarcity, while the growing global population demands have increased. Reclaimed water (RW) has become essential, offering a viable alternative for crop irrigation in line with circular economy principles. However, although RW reuse is crucial for addressing water shortages, the presence of micropollutants still poses a challenge. The potential for micropollutants to be taken up by crops and enter the food chain still raises significant scientific concern. This work studies RW treated by conventional activated sludge followed by sand filtration and chlorination (CAS+SFC-RW) and membrane-bioreactor-treated RW (MBR-RW) in terms of micropollutant concentrations, providing insights into the differences in micropollutant profiles between the two treatments. The results demonstrate that MBR-RW generally exhibits lower cumulative concentrations of target analytes. However, the study also indicates that the storage of RW for irrigation significantly affects the presence of micropollutants, contributing to their degradation, increase or persistence. Soil analysis revealed fewer detectable micropollutants in the topsoil (0-20 cm) compared to RW, likely attributed to attenuation processes, and more micropollutants (both with respect to concentration and number) compared to deeper soil layers. Carbamazepine, 10,11-epoxide-carbamazepine, and telmisartan were found to migrate to deeper soil levels. The analysis revealed 13 micropollutants in lettuce irrigated with CAS+SFC-RW and 8 with MBR-RW, with carbamazepine and sulfamethoxazole being the most abundant. These differences are likely driven by the physicochemical properties of the compounds and plant-specific factors. Leachates examination showed the potential for contaminants to leach through soil, posing a risk for groundwater contamination. The study showed that the presence of micropollutants in RW is not directly associated with their presence in soil or lettuce, underscoring the need for regulatory policies that address not only their presence in RW but their eventual fate within the agricultural and environmental context.

The fate and ecological risk of typical diamide insecticides in soil ecosystems under repeated application

Diamide insecticides are the third most widely used class of pesticides worldwide. However, the long-term impacts of repeated diamide applications on soil ecosystems remain unclear. This study investigated chlorantraniliprole (CLP) and cyantraniliprole (CYP) effects on soil ecosystems through simulated repeated exposures. Results showed both exhibited slow degradation in the soil, with repeated applications extending their persistence, particularly for CLP. Both significantly inhibited soil alkaline nitrogen and organic matter accumulation, while reducing urease and sucrase activities, with CLP exerting stronger inhibitory effects. Metagenomic analysis indicated that CLP and CYP notably reduced soil microbial diversity. Additionally, the two insecticides altered the soil microbial community structure and inhibited carbon-nitrogen metabolic pathways. Further analysis revealed that CLP treatment significantly decreased the relative abundances of Mesorhizobium and Marmoricola, whereas CYP treatment primarily reduced Clostridium_sensu_stricto_1. All of these genera exhibited significant positive correlations with key metabolic pathways in soil carbon and nitrogen cycling. Notably, the relative abundance of Sphingomonas increased significantly following CLP and CYP treatments, demonstrating potential degradation capabilities. Overall, both CLP and CYP posed ecological risks to soil ecosystems, with CLP exhibiting more severe impacts. These findings revealed the need for strengthened scientific management in actual production.

Influence of soil type on bacterial growth and tolerance to experimentally added human antibiotics

The human antibiotics cefuroxime (CXM) and azithromycin (AZI) are among the most commonly prescribed. A significant portion of both are excreted and has been detected in sewage treatment plant effluents. The increasing use of such effluents in crops for irrigation and as fertilisers poses a threat to soil microbiota because of the presence of antibiotics. The lack of studies on CXM and AZI in soils hinders our understanding of their potential toxic effects on soil bacterial communities and ecosystem services. This study significantly contributes to the literature by quantifying the toxicity of CXM and AZI at varying concentrations in 12 different crop soils and tracking their evolution over time. The study also examined whether antibiotic pressure led to the development of more tolerant bacterial communities. The results of this study are the values of the logarithm of the antibiotic concentration at which 50 % of bacterial growth is inhibited (Log IC50) and indicate that both antibiotics are toxic to soil bacteria. The direct toxicity of CXM (1 day after contamination) was higher (Log IC50: 0.9 = 7.9 mg kg-1) than that of AZI (Log IC50: 3.4 = 2362 mg kg-1). However, bacterial growth was less affected by CXM over time, whereas AZI remained toxic in some soils until day 42 (Log IC50: 3.2 = 1533 mg kg-1 and 3.4 = 2291 mg kg-1, respectively). The overall results indicate that selective pressure exerted by antibiotics generates antibiotic tolerance in soils, even at the lowest antibiotic concentration studied (7.8 mg kg-1). The general trend was to increase tolerance to higher antibiotic concentrations up to the highest concentration studied (2000 mg kg-1). However, the degree of tolerance developed was highly dependent on soil type. More studies should be conducted to quantitatively assess the toxic and tolerance-developing effects of antibiotics in soils. Such information will be valuable for identifying which antibiotics pose a threat to the soil microbiota and consequently to human health.

Effect of soil-groundwater system on migration and transformation of organochlorine pesticides: A review

Soil is the place where human beings, plants, and animals depend on for their survival and the link between the various ecological layers. Groundwater is an important component of water resources and is one of the most important sources of water for irrigated agriculture, industry, mining and cities because of its stable quantity and quality. Soil and groundwater are important strategic resources highly valued by countries around the world. However, in recent years, the deterioration of the ecological environment of soil-groundwater caused by industrial, domestic, and agricultural pollution sources has continued to threaten human health and ecological security. Among them, organochlorine pesticides (OCPs), as typical organic pollutants, cause very serious pollution of soil and groundwater environment. However, most studies on the pollution of OCPs have focused on the aboveground or surface water environment, and little consideration has been given to the pollution and hazards of OCPs to the deep soil and groundwater environment, especially the effects of different environmental factors on the transport and transformation of OCPs in soil-groundwater. Moreover, in addition to the influence of a single factor on it, the interactions that arise between different factors cannot be ignored. This paper focuses on two major sources of OCPs in soil and groundwater environments, compiles and summarizes the effects of environmental factors such as pH, microbial communities and enzyme activities on the transport and transformation of OCPs in soil and groundwater systems, discusses the synergistic effects of individual environmental factors and others, and comprehensively analyses the effects of synergistic effects of various environmental factors on the transport and transformation of OCPs. In the context of ecological civilization construction, it provides the scientific basis and theoretical foundation for the prevention and treatment of OCPs-contaminated soil and groundwater, and puts forward new ideas and suggestions for the research and development of green, eco-friendly remediation and treatment technologies for OCPs-contaminated sites.

Coupled bio-solar photocatalytic treatment for reclamation of water polluted with pharmaceutical and pesticide residues: Impact on tomato irrigation

Reusing reclaimed water for crop irrigation can mitigate water scarcity in agriculture; however, contaminants such as pharmaceuticals and pesticides in wastewater pose risks. This study investigated the impact of a coupled bio-solar photocatalytic treatment on the reclamation of water polluted with seven pharmaceuticals and seven pesticides for irrigation of two tomato crop cycles. Pollutant residues were removed using natural sunlight and TiO2/Na2S2O8 in a pilot plant located in Murcia, Spain. Efficient removal (> 96 %) of all target pollutants was achieved in the effluent after coupled treatment. Reclaimed water was then used to irrigate the tomato crops, and several yield and quality parameters were analysed to evaluate the effects on the harvested tomatoes. No significant differences were observed in the total yield, number and mean fruit weight, size, pericarp firmness, external colour, and nutritional data between the crops irrigated with reclaimed, control, and polluted water. However, differences in the degree of ripeness were observed. None of the investigated pollutants was detected above the limit of quantification in tomato samples irrigated with reclaimed water, except for venlafaxine (0.028 µg kg-1) in the second crop cycle. When the crop was irrigated with polluted water, different pollutant residues were detected in soil (10) and tomato (4) samples. The results suggest that coupled bio-solar photocatalytic treatment is an effective method for reclaiming water polluted with pharmaceutical and pesticide residues, and the reclaimed water can be safely used for tomato irrigation without compromising crop yield and quality.

Pharmaceutical and Trace Metal Interaction within the Water-Soil-Plant Continuum: Implications for Human and Soil Health

Unplanned water reuse for crop irrigation may pose a global health risk due to the entry of contaminants into the food chain, undesirable effects on crop quality, and impact on soil health. In this study, we evaluate the impact derived from the co-occurrence of pharmaceuticals (Phs), trace metals (TMs), and one metalloid within the water-soil-plant continuum through bioassay experiments with Lactuca sativa L. Results indicate that the co-occurrence of Phs and TMs has synergistic or antagonistic effects, depending on target contaminants and environmental compartments. Complex formations between drugs and TMs may be responsible for enhanced sorption onto the soil of several Phs and TMs. Concerning plant uptake, the co-occurrence of Phs and TMs exerts antagonistic and synergistic effects on carbamazepine and diazepam, respectively. With the exception of Cd, drugs exert an antagonistic effect on TMs, negatively affecting their uptake and translocation. Drug contents in lettuce edible parts do not pose any threat to human health, but Cd levels exceed the maximum limits set for leafy vegetable foodstuffs. Under Ph-TM conditions, lettuce biomass decreases, and a nutrient imbalance is observed. Soil enzyme activity is stimulated under Ph-TM conditions (β-galactosidase) and Ph and Ph-TM conditions (urease and arylsulfatase), or it is not affected (phosphatase).

Identifying organic micropollutants' transformation products from the soil dissipation experiment by non-targeted high-resolution mass spectrometry approach: Can we gain more than transformation product identity?

Risk assessment of environmental hazards originating from xenobiotics extensively used worldwide (e.g., pharmaceuticals, bisphenols, or preservatives) requires a combined study of their effects, mobility, dissipation mechanisms, and subsequent transformation product identification and evaluation. We have developed an efficient accelerated solvent extraction method for a broad range of micropollutants of variable physical-chemical properties in soils to enable more accurate hazard characterisation. Micropollutant recoveries from freeze-dried soils were 60-120%, with the exception of atorvastatin, fexofenadine, and telmisartan, which had reduced recoveries (40-66%). The observed matrix effect ranged from -26% to 17% and was corrected by the matrix matching standard for quantitative analysis. The method allows sensitive and reliable determination of a wide range of analytes in soil samples and, consequently, qualitative analysis of transformation products (TP) with variable physicochemical properties. We identified TPs of five compounds (venlafaxine, telmisartan, valsartan, atorvastatin, and sertraline) by applying suspect and non-targeted data analyses. To our knowledge, the transformation product of atorvastatin was reported for the first time. All others were found in soil or other matrices. Valsartan (formed valsartan acid) and atorvastatin (transformed probably by oxidative decarboxylation of beta, delta dihydroxy heptanoic acid chain to propionic acid) were modified to a relatively large extent. All other compounds identified were only hydroxylated (sertraline and telmisartan) or demethylated (venlafaxine). We estimated the stability and presence of the identified TPs based on the constructed time trends and the ratio between TP formation and degradation rates. We demonstrated how valuable a non-targeted approach can be for complex evaluation of the fate and effect of soil pollutants.

Contamination of water, soil, and plants by micropollutants from reclaimed wastewater and sludge from a wastewater treatment plant

Several studies have shown that plants can absorb various micropollutants. The behavior of micropollutants from wastewater treatment plant resources was comprehensively investigated in raised beds in which either a mixture of vegetables or maize was grown. The beds were either irrigated with treated wastewater or enriched with sewage sludge or composted sewage sludge. Over the year, samples of wastewater, water drained from the beds, soils and plants were analyzed. Of the seventy-five analyzed substances, fifty-four, thirty-three and twenty-seven were quantified in wastewater, sewage sludge, and composted sludge, respectively. Alarmingly, approximately 20 % of the compounds from wastewater were also detected in the solutions leached from the beds irrigated with wastewater (e.g., gabapentin, tramadol, sertraline, carbamazepine, its metabolites, and benzotriazoles). In addition, a gradual increase in the content of four substances (telmisartan, venlafaxine, carbamazepine, citalopram) was recorded in these beds. The compounds from both biosolids used for soil enrichment tended to remain in the soils (e.g., telmisartan, venlafaxine, sertraline, its metabolite, citalopram, and its metabolite). Only four compounds (sertraline and three benzotriazoles) leached from these beds. Uptake of some chemicals (e.g., gabapentin, tramadol, carbamazepine and its metabolite, and venlafaxine and its metabolite) and their accumulation in plant tissues was observed mainly in vegetables grown on beds irrigated with wastewater. However, daily consumption values for edible plant parts and individual compounds did not indicate a direct threat to human health. Results of this innovative study show possible risks associated with the use of these resources in agriculture. Of particular concern is the possible micropollutants percolation towards groundwater, including those for which high sorption and thus low mobility in the soil environment is expected, such as sertraline. Soil and crop contamination cannot be neglected either.