The Impact of Rainwater Quality Harvested from Asbestos Cement Roofs on Leaf Temperature in Solanum lycopersicum as a Plant Water Stress Indicator

Abstract

Rainwater harvesting (abbreviation: RWH) presents a valuable alternative water source for agriculture, particularly in regions facing water scarcity. However, contaminants leaching from roofing materials, such as asbestos cement (abbreviation: AC), may compromise water quality and affect plant physiological responses. This paper aimed to assess how simulated rainwater, reflecting the different levels of contamination (1, 2, 5, 10, and 20 mg/L), influences leaf temperature in tomato plants (Solanum lycopersicum), a known non-invasive indicator of plant water stress. The treatments were applied over a four-week period under controlled greenhouse conditions. Leaf temperature was monitored using infrared thermography. Results showed that higher treatment concentrations led to a significant increase in leaf temperature, indicating elevated water stress. These findings suggest that even low levels of contaminants originating from roofing materials can induce detectable physiological stress in plants. Monitoring leaf temperature offers a rapid and non-destructive method for assessing environmental water quality impacts on crops. The outcomes of this research have direct applicability in the safer design of RWH systems and in evaluating the suitability of collected rainwater for irrigation use.

1. Introduction

The increasing global scarcity of water poses a significant challenge to sustainable agricultural production [1,2], particularly in semi-arid and arid zones where climate change has amplified the unpredictability of natural precipitation patterns [3,4]. In such areas, traditional water supply systems, such as the utilization of surface and groundwater, are proving to be increasingly unreliable and unsustainable [5], due in part to overexploitation and the degradation of water quality [6,7]. Therefore, decentralized water management strategies that can easily adjust to local environments, are eco-friendly, and reduce the strain on public water systems are becoming more popular [8,9].

Rainwater harvesting (abbreviation: RWH) represents one of the most promising methods in this regard, aiming to collect, store, and reuse precipitation locally for domestic or agricultural purposes [10,11]. Rooftop rainwater harvesting (abbreviation: RRWH) is particularly widespread, as it requires minimal infrastructural investment, is cost-effective, and repurposes existing building structures for water collection [12,13]. Beyond its significance for water retention, this method also contributes to flood prevention and the mitigation of the urban heat island effect by decentralizing urban water cycles [14,15]. The decentralization of the water cycle contributes to the improvement in the urban microclimate by enhancing evaporation and evapotranspiration within the urban fabric [16]. These processes remove heat from the environment, thereby reducing surface and ambient temperatures [17]. Furthermore, retaining precipitation locally decreases runoff from impervious surfaces and mitigates their heat absorption effects, thus alleviating the urban heat island effect [18].

Globally, and especially in low- and middle-income countries, a significant proportion of rooftops are still covered with asbestos cement (abbreviation: AC) sheets [19,20]. These materials, widely used throughout the 20th century, became one of the most common roofing solutions due to their affordability, physical durability, and ease of installation [21,22]. It has been estimated that the number of asbestos-containing materials (abbreviation: ACM) produced ranges from 3000 to 5000 [22]. However, increasing attention has been drawn to the environmental health risks associated with AC, particularly those arising from its physical and chemical degradation over time [23,24,25]. Although the dangers of asbestos are well documented and its use is prohibited in over 50 countries, approximately 2 million tons are still utilized globally annually [26].

As roofing materials degrade over time, they become susceptible to surface deterioration and fracture, causing the release of contaminants, notably hazardous heavy metals like lead, chromium, nickel, and cadmium, into collected rainwater [27,28]. The presence of such contaminants in collected rainwater may have serious consequences [29]. Although heavy metals may be associated with asbestos-containing materials due to environmental deposition or material additives, the fibers themselves can also exert toxic effects [30]. Chrysotile has been reported to affect plant physiological processes such as seed germination, root elongation, and nutrient uptake, potentially through oxidative stress mechanisms or physical interference with root structures [31,32].

While the microbiological risks associated with rainwater use are relatively well documented, scientific research focusing on the agricultural utilization of rainwater collected specifically from anthropogenic urban surfaces remains scarce [33,34]. In particular, studies investigating the physiological effects of such water on plants are limited, highlighting a critical gap in understanding the implications of using urban runoff for irrigation purposes. This is concerning, given that in many rural and peri-urban areas, households directly use RRWH for irrigation without any prior water quality assessment or treatment [35,36,37]. Even at low concentrations, toxic elements in the water can induce physiological stress responses in plants, affect growth, reduce photosynthetic efficiency, and ultimately lead to yield losses and the deterioration of soil health over time [38,39,40].

In response to these challenges, recent years have seen a growing emphasis on non-invasive measurement techniques that enable the rapid, accurate, and cost-effective detection of plant water status and stress responses under field conditions [41,42]. Among these, leaf temperature measurement has proven particularly valuable, as it closely correlates with stomatal conductance, transpiration rates, and overall plant water balance [43,44,45]. Changes in leaf temperature may sensitively reflect environmental variables, including water quality [46]. Infrared thermography allows for contactless, real-time monitoring of leaf temperature, enabling the detection of physiological changes that are not yet visible [47]. This contributes to the early identification of plant stress conditions and facilitates timely, targeted interventions [48].

Therefore, research into how different levels of contaminants, like those from old AC roofs, affect plant health is important for both scientific and practical reasons. Instead of directly harvesting rainwater, this paper applies predefined treatment solutions to isolate and analyze physiological responses under controlled conditions. Special attention is given to leaf surface temperature, which serves as a non-invasive, real-time proxy for plant water stress. The novelty of this research lies in its targeted simulation approach, wherein chemically characterized irrigation solutions mimic real-world contamination scenarios, allowing for the reproducible assessment of sub-lethal stress. By utilizing infrared thermography to detect early physiological disturbances before visible symptoms arise, this paper offers preliminary insights into the potential effects of water quality on plant health, acknowledging that further studies incorporating additional physiological parameters are necessary for a more comprehensive understanding. These findings have practical implications for water reuse safety standards, particularly in decentralized or peri-urban farming systems where reliance on non-conventional water sources is growing. These findings can help improve guidelines for irrigation water quality, which is important for maintaining crop health as environmental and infrastructure conditions change.

2. Materials and Methods

To evaluate the physiological impact of contaminated rainwater originating from AC roofing materials, a controlled greenhouse experiment was established using tomato plants (Solanum lycopersicum) as bioindicators. The paper focused on assessing how varying concentrations of asbestos-derived contaminants in irrigation water influence leaf temperature, a reliable indicator of plant water stress. The experimental setup, irrigation treatments, measurement techniques, and statistical analyses are detailed below.

2.1. Experimental Design and Growth Conditions

The analysis was conducted over a continuous four-week period during the active vegetative growth stage of tomato (Solanum lycopersicum L., cv. “Mobil”), a commonly used model species [49,50,51] in plant physiology due to its sensitivity to abiotic stress factors and well-characterized response profiles. The experiment commenced in March 2024, with its timeline and length designed to coincide with the typical vegetative and early reproductive stages of tomato plants, which facilitated physiologically significant observations. The four-week durations were selected to coincide with the active vegetative and early reproductive stages of tomato development, a period known to be physiologically responsive to abiotic stressors, including water quality. This timeframe was considered optimal for detecting early physiological effects without confounding from senescence or fruiting processes.

Seeds were germinated under controlled conditions in a sterile seed-starting mix composed of peat moss, perlite, and vermiculite. After emergence, seedlings were maintained under uniform conditions (25 ± 1 °C, 60–70% relative humidity, 16/8 h light/dark photoperiod) until they reached the four-leaf stage. Subsequently, seedlings were transplanted into individual 2 L plastic pots filled with a homogeneous, pre-sterilized growth substrate composed of peat-based commercial potting soil (Garri, TERRA-TŐZEG KFT., Budapest, Hungary). The experimental design excluded the application of fertilizer; furthermore, the absence of visual symptoms indicative of nutrient deficiency suggests that the pre-sterilized commercial substrate contained sufficient basal nutrients (N > 0.3 wt%, P₂O₅ > 0.1 wt%, K₂O > 0.1 wt%) to sustain uniform plant development during the experimental timeframe. Each pot was equipped with a saucer to prevent leachate loss and potential cross-contamination. Following transplantation, plants underwent a one-week acclimatization period during which they were irrigated with distilled water.

At the end of this period, plants were randomly assigned to one of six treatment groups, each consisting of ten biological replicates, resulting in a total of ten plants per treatment level. The control group received distilled water and five treatment groups received simulated contaminated rainwater with increasing concentrations of asbestos-related particulates (1, 2, 5, 10, and 20 mg/L). Treatments were applied consistently throughout the experimental period by top-watering each plant with 200 mL of the respective solution every 48 h, ensuring uniform hydration while avoiding leaf wetting. Environmental conditions were strictly monitored and maintained using automated climate control systems. Temperature was kept constant at 25 ± 2 °C during the photoperiod and 18 ± 2 °C during the dark phase, with 60–70% relative humidity and a 16/8 h light/dark photoperiod. Environmental parameters were continuously monitored and maintained within defined ranges, ensuring stable and reproducible growth conditions throughout the experiment. Plant health and development were monitored regularly, and no signs of nutrient deficiencies, pest infestation, or disease were observed during the course of the experiment, thereby ensuring that any physiological response could be attributed to the experimental treatments.

2.2. Preparation of Simulated Contaminated Rainwater

To simulate the potential contamination of harvested rainwater from AC roofing materials, aqueous solutions containing chrysotile-AC were prepared at defined concentrations of 1, 2, 5, 10, and 20 mg/L. These concentrations refer to the mass of ACM suspended in the solution, expressed as milligrams of dry chrysotile-AC per liter of distilled water. The asbestos source material was derived from aged, industrial-grade, non-friable AC panels that were mechanically ground to a fine powder under controlled conditions to mimic environmentally realistic particle release. All solutions were prepared in analytical-grade distilled water to minimize confounding from background electrolytes or organic compounds. The final solution thus consisted solely of chrysotile-AC particulate matter suspended in distilled water, without any added salts, nutrients, or surfactants. The solutions were stirred for 24 h at room temperature using magnetic stirrers to ensure the homogenous dispersion of particulate matter. After settling for 12 h, the supernatant was collected for use in irrigation to simulate the bioavailable fraction of leachates. The prepared solutions were stored in opaque, airtight polyethylene containers at 4 °C and shielded from light to prevent the photodegradation or precipitation of labile constituents. This approach ensured reproducible conditions across concentrations and minimized batch-to-batch variability during the experiment.

2.3. Irrigation Regimen

Irrigation treatments were applied in a uniform fashion to all experimental units utilizing a precise volumetric methodology. Each plant received 200 milliliters of its designated solution every 48 h for the duration of the investigation. Water was applied directly to the surface of the growth substrate to preclude foliar contact and prevent potential confounding due to surface absorption or leaf tissue irritation from contaminants. To ensure consistency and prevent unintended nutrient loss or cross-contamination, all pots were situated on individual catchment trays.

2.4. Leaf Temperature Measurement

Leaf surface temperature, a reliable physiological indicator of plant water status and stomatal regulation, was measured non-invasively using a handheld infrared thermometer (Bosch UniversalTemp, Robert Bosch GmbH, Gerlingen, Germany), with a measuring range of −30 °C to +500 °C. Physiological measurements were performed using a handheld infrared thermometer Bosch UniversalTemp infrared thermometer, with a measuring range of −30 °C to +500 °C. This method offers rapid, point-based surface temperature readings with high precision and repeatability. The infrared thermometer was additionally calibrated prior to each measurement session using an external blackbody calibration source to ensure instrument accuracy. All readings were taken between 09:00 and 11:00 to coincide with the steady-state phase of photosynthesis and before significant midday stomatal closure or thermal load could bias the results. The infrared thermometer was calibrated prior to each measurement session using an external blackbody calibration source to ensure instrument accuracy. For each plant, temperature measurements were collected from three fully developed, sun-exposed leaves located in the upper third of the canopy. The sensor was held perpendicular to the leaf surface at a consistent distance of approximately 30 cm, with the spot size-to-distance ratio ensuring the adequate targeting of the leaf lamina without any interference from the surrounding structures. Each reading represented the average of three quick successive scans over the same leaf area, and the mean value was recorded. Measurements were consistently taken for the same individual leaf of each plant, typically the youngest fully expanded leaf, to minimize intra-plant variability. All data were recorded under consistent environmental conditions, and repeated measurements were conducted at predefined intervals to ensure temporal resolution and statistical robustness.

3. Results

The thermographic measurements gathered during this research unequivocally demonstrate a direct relationship between the concentration of the simulated contaminated rainwater used for irrigation and the increase in leaf surface temperature. Leaf temperature, a well-established indicator of plant water stress, steadily climbed as the concentration of the chrysotile-based leachate rose, implying a physiologically significant stress response.

In the control group receiving only distilled water, the mean leaf surface temperature was observed to be 25.10 °C with a standard deviation of ±0.30 °C. This relatively low degree of variability and absolute temperature value are indicative of optimal transpiration and stomatal function under non-stress conditions. At a concentration of 1 mg/L, a marginal yet consistent elevation in temperature was recorded (25.25 ± 0.31 °C), which may already reflect the early indications of physiological sensitivity to even minimal levels of contamination. This upward trend became more distinct at 2 mg/L (25.76 ± 0.51 °C), where both the mean and variability increased, pointing toward emerging water stress effects that surpass baseline thermal fluctuations. To enhance the interpretability and visual clarity of these findings, the data are presented in Figure 1 to illustrate the distribution, spread, and outliers of leaf temperature within each treatment group, and as bar charts displaying mean values with standard deviations, to emphasize central tendencies and facilitate the direct visual comparison of treatment effects. This presents the average values of data collected throughout the entire experimental period. The measurements include all temporal repetitions and biological replicates, ensuring the statistical reliability of the results.

The physiological response of the plants was markedly altered from the 5 mg/L treatment onwards. At this concentration, the average leaf temperature increased by 1.7 °C compared to the control, reaching 26.82 ± 0.51 °C. This suggests moderate stomatal closure and diminished evaporative cooling. The thermal elevation was even more pronounced at 10 mg/L (27.63 ± 0.69 °C), accompanied by elevated intra-group variability and a substantial absolute temperature rise. These results indicate heterogeneity in stress tolerance or water uptake efficiency among the individual plants, potentially linked to threshold effects in toxicant accumulation or water potential regulation.

At the highest tested concentration of 20 mg/L, the mean leaf surface temperature reached 28.39 ± 0.58 °C—representing an elevation of more than 3.2 °C above the control group baseline. Figure 2 represents the differences in mean leaf temperature and associated standard deviations expressed as percentages relative to the control group across treatments. Figure 2 complements Figure 1 by presenting the regression line and corresponding R² value, demonstrating the percentage change in temperature relative to increasing dose concentrations expressed as percentage of control.

This substantial thermal increase is indicative of severe physiological stress, likely stemming from extensive stomatal closure as the plant attempts to minimize further uptake of contaminated water and mitigate internal ionic or oxidative imbalances. Such a response is consistent with established plant defense mechanisms under abiotic stress conditions, particularly when water quality deteriorates due to the presence of toxic or particulate contaminants such as those derived from AC-contacted leachates. Interestingly, despite being exposed to the most severe treatment level, this group demonstrated a slight reduction in intra-treatment variability (SD = ±0.58 °C) when compared to the 10 mg/L group (SD = ±0.69 °C). Significance testing revealed that the differences in standard deviations among treatment groups were statistically meaningful. The independent samples t-test showed a statistically significant difference between the groups (p < 0.05). This narrowing of temperature distribution may point toward the onset of a physiological saturation threshold, beyond which further increases in toxicant concentration do not proportionally escalate the stress response. Instead, it is plausible that the majority of plants in this group had already reached a critical limit of physiological plasticity, manifesting as uniformly high leaf temperatures. At this stage, transpirational cooling becomes minimal or absent, suggesting that stomatal aperture is broadly constrained, and water transport through the xylem may also be impaired.

Such uniformity in response under maximal stress conditions may reflect a convergence of defensive strategies at the expense of growth and photosynthetic productivity. Indeed, under extreme abiotic challenge, plants often shift from adaptive flexibility to survival-oriented rigidity, marked by restricted gas exchange, slowed metabolism, and the conservation of cellular integrity [52]. From an ecological and agronomic perspective, these findings are highly consequential. They imply that the irrigation of sensitive crop species with heavily contaminated harvested rainwater, even in sub-lethal concentrations, can induce stress responses that are not only physiologically costly but also difficult to reverse [53]. The reduced variability further suggests that once a critical threshold is surpassed, most individuals within a crop population experience similar levels of impairment, thereby increasing the risk of uniform yield loss or quality reduction [54,55]. This underscores the importance of regularly monitoring the chemical composition of non-conventional water sources used in agriculture, especially in systems that rely on rooftop runoff for irrigation during dry seasons.

The thermal signature observed in the 20 mg/L treatment is emblematic of advanced stress, and its consistency across replicate plants enhances confidence in the use of leaf surface temperature as a reliable, scalable indicator for diagnosing water quality-related stress. In future applications, such infrared thermometric approaches could be paired with early-warning systems or automated irrigation controls to pre-emptively adjust water inputs based on real-time plant feedback.

4. Discussion

This paper’s findings present compelling empirical evidence of a direct, dose-dependent correlation between the concentration of simulated AC roof leachate and the physiological stress responses exhibited by tomato plants, as indicated by their elevated leaf surface temperatures. The non-invasive thermal imaging data collected throughout the experimental period unambiguously demonstrate that heightened levels of contamination correspond with increased thermal signatures, which serve as a proxy for reduced stomatal conductance and diminished transpirational cooling. Control plants irrigated solely with distilled water maintained a stable leaf temperature profile (mean: 25.10 ± 0.30 °C), indicative of normal stomatal function and optimal hydration status. Even the lowest tested concentration (1 mg/L) led to a subtle but consistent rise in mean temperature, suggesting an early and sensitive physiological response to trace contaminants.

At a concentration of 5 mg/L, temperature elevations became more pronounced and significant for the plants. At 10 mg/L, the varying values indicated a disparity in the plants’ capacity to manage stress, potentially attributable to differences in their internal functions, nutrient absorption through their roots, or detoxification capabilities. The most pronounced temperature response was observed at 20 mg/L, with an average temperature of 28.39 ± 0.58 °C—exceeding normal levels by over 3 °C. Interestingly, variability decreased at this concentration, which may indicate the onset of a saturation threshold, where most plants exhibit maximal stomatal closure and uniformly reduced cooling capacity [56]. This convergence suggests a physiological tipping point, beyond which stress responses are uniform and indicative of advanced impairment [57].

From an agronomic perspective, the results highlight the potential risk posed by untreated or poorly characterized harvested rainwater, particularly when collected from aged AC roofs [58,59]. Even sub-lethal concentrations of contaminants can trigger significant physiological stress, compromising crop health and productivity [41]. The consistent increase in temperature across replicates and treatments further validates the utility of leaf surface temperature as a sensitive and scalable metric for plant stress monitoring [43].

Beyond thermal trends alone, these findings resonate with previous observations linking heavy metal and mineral particulate stress to disruptions in cellular water homeostasis and reactive oxygen species (abbreviation: ROS) accumulation [60,61,62]. It is plausible that certain ions leached from AC, such as Ca²⁺, Mg²⁺, or trace elements like Cr or Ni, interact with root membrane transporters or signaling cascades, mimicking the osmotic and oxidative features of classical salinity stress. This overlap reinforces the conceptual and methodological convergence between anthropogenic water contaminants and natural abiotic stressors, both of which activate conserved defense responses including ABA-mediated stomatal closure, ROS scavenging, and metabolic downregulation [63]. Moreover, the reduced thermal variability observed at the highest concentration suggests a form of “stress canalization,” whereby the range of physiological responses narrows under extreme conditions, likely due to the collapse of homeostatic flexibility [64,65]. This notion aligns with the broader theory of plant stress physiology, where early-stage adaptability gives way to fixed, resource-conserving states once damage or signal intensity surpasses a critical threshold [66]. Importantly, this study also underscores the relevance of infrastructural legacy materials in contemporary agricultural risk assessments. While asbestos is typically considered from a human toxicology standpoint, its indirect influence on food systems via leachate-mediated phytotoxicity remains underexplored [67]. The findings therefore encourage greater scrutiny of water storage materials and surface runoff sources in peri-urban or resource-limited agricultural settings, where RWH is increasingly promoted as a climate-adaptive practice. Finally, the integration of thermal data into digital phenotyping platforms offers a promising pathway toward real-time water quality surveillance and adaptive irrigation management [68]. As climate change accelerates hydrological variability and infrastructure ages globally, these insights may help mitigate hidden stresses that reduce yield potential or increase vulnerability to pathogens and secondary stressors [69,70].

To further contextualize these results, comparisons with similar studies examining heavy metal-induced osmotic and oxidative stresses in plants reveal parallel physiological adaptations, thereby reinforcing the robustness of our findings within a broader environmental stress framework [61,71]. Although chrysotile is not a heavy metal, the degradation of asbestos-containing cement products can lead to the release of secondary contaminants, including heavy metals and particulate matter, thereby imposing a dual nature of stress on plants [72]. Consequently, both direct physical interference from chrysotile fibers and chemical toxicity from associated heavy metals may contribute to the observed physiological responses, suggesting a complex interaction of osmotic and oxidative stressors [73,74]. Previous research has demonstrated that exposure to comparable concentrations of heavy metals triggers enhanced antioxidant enzyme activities and modulates stomatal conductance, effects consistent with the thermal and physiological patterns observed here [60,75]. Such integrative analyses not only substantiate the mechanistic interpretations proposed but also highlight the multifaceted nature of plant responses to complex pollutant mixtures, warranting interdisciplinary approaches for comprehensive risk assessment. Moreover, incorporating data from related investigations on phytotoxicity induced by urban runoff and legacy contaminants would enrich the discussion on the implications for agricultural productivity and ecosystem resilience [76]. Considering the potential presence of chrysotile fibers in harvested rainwater, future research and practical applications should carefully evaluate the risks and benefits associated with its use, particularly in agricultural and domestic settings. The safe utilization of such water requires the development and implementation of effective treatment technologies aimed at removing asbestos fibers and any associated contaminants. Advanced filtration methods, such as membrane filtration, coagulation–flocculation processes, and adsorption techniques, have shown promise in mitigating asbestos-related pollution in water sources. Moreover, routine monitoring of water quality, coupled with public awareness campaigns, is essential to prevent inadvertent exposure and environmental contamination. Recommendations include establishing regulatory guidelines for acceptable chrysotile concentrations in harvested rainwater and promoting integrated water management strategies that prioritize both resource conservation and health protection.

5. Conclusions

This investigation presents compelling evidence that leaf surface temperature, as measured through non-invasive thermographic imaging, serves as a reliable and highly sensitive biomarker of water quality-induced stress in tomato plants. The findings reveal that even minor levels of contamination, specifically those emanating from AC leachates, can elicit measurable and biologically meaningful alterations in plant water relations. Such responses, detectable at concentrations as low as 1 mg/L, suggest that tomato plants possess a finely calibrated physiological mechanism capable of perceiving and reacting to the ionic or particulate burdens present in irrigation water. The initial response, characterized by early stomatal regulation and slight thermal elevation, signals the onset of adaptive stress management strategies, even prior to the manifestation of visible symptoms. As contaminant concentration escalated, the plant responses displayed a nonlinear trajectory, becoming increasingly pronounced. This disproportionate intensification suggests that higher ionic loads exert compounding effects on plant function, potentially overwhelming detoxification pathways or water transport mechanisms. Particularly noteworthy was the convergence of thermal responses observed at the highest tested concentration, where most individuals within the treatment group exhibited similarly elevated leaf temperatures. This uniformity indicates a physiological saturation threshold beyond which further increases in contamination no longer elicit proportionally greater responses, but instead reflect a constrained, survival-oriented state with minimal variability among plants. Such homogeneity is characteristic of an advanced stress condition, where the plant’s adaptive flexibility is markedly reduced, and defense mechanisms dominate over growth or productivity. This paper highlights the potential of thermographic imaging as a non-invasive and scalable approach for monitoring plant health in response to abiotic stressors. Measurements of leaf surface temperature offer a rapid and cost-effective technique that can be deployed in both experimental and field settings, enabling the early identification of water quality issues before visible symptoms emerge. Amidst the context of increasing climate variability and the growing reliance on alternative irrigation sources, such as harvested rainwater, this research advocates for enhanced quality control and pre-treatment of non-conventional water inputs. Furthermore, the integration of thermographic data into precision agriculture platforms holds significant promise for improving crop resilience, reducing yield variability, and promoting sustainable water use in agricultural systems.

This paper provides significant new insights into plant physiological responses to complex, industrial-derived contaminants—specifically those originating from AC leachates. By utilizing non-invasive leaf surface temperature measurements via infrared thermometry, this research identifies a highly sensitive indicator capable of detecting plant stress at contaminant concentrations as low as 1 mg/L. Such early responses underscore the remarkable sensitivity of plants to subtle physicochemical perturbations in their environment. Crucially, the findings highlight that AC leachates, often overlooked in conventional water quality assessments, can exert biologically meaningful effects on crop function even at minimal levels. The results emphasize the need for heightened scrutiny of irrigation sources, particularly when utilizing non-traditional inputs such as harvested rainwater or water stored in containers associated with construction materials. By demonstrating that thermal profiling can serve as an early warning signal for hidden contaminants, this research contributes a novel methodological perspective to the field of environmental plant physiology. Moreover, it underlines that the source and composition of waterborne pollutants are critical factors in safeguarding plant health and ensuring food safety. As such, these findings not only introduce a valuable biomarker for abiotic stress detection but also offer a cautionary perspective on water reuse practices in agriculture.