Acid Rain Conditions Research Articles

Simulated acid rain offset a warming-induced increase in soil respiration but did not impact the temperature sensitivity of soil respiration in a cropland

Investigating the effects of warming and simulated acid rain on soil respiration and its temperature sensitivity is crucial in predicting the potential responses of soil C cycles to future climate warming. A three-year field experiment with six treatments (CK, WA, CK-4.0, WA-4.0, CK-2.0 and WA-2.0) of warming (coded as WA) and three simulated acid rain levels (coded as CK, pH 4.0 and pH 2.0) was performed in an annual winter wheat–soybean cropland to study the comprehensive effects of warming and simulated acid rain on soil respiration and its temperature sensitivity. The results indicated that warming significantly (P < 0.001) increased soil respiration under no (CK) or low acid rain application (pH 4.0), while the warming effects on soil respiration were not significant under intensive acid rain conditions (pH 2.0). The annual mean soil respiration was 2.79 ± 0.02, 3.02 ± 0.01, 2.58 ± 0.07, 2.79 ± 0.03, 2.54 ± 0.04 and 2.50 ± 0.03 μmol m−2 s−1 in the CK, WA, CK-4.0, WA-4.0, CK-2.0 and WA-2.0 plots, respectively. Warming induced an 8.0% increase in soil respiration compared with the CK. Intensive simulated acid rain (pH 2.0) offset the warming effects on soil respiration. A total of 36.9–55.5% of the seasonal variation in soil respiration was explained by soil temperature, while the moisture effects on soil respiration were not significant (P > 0.05). Warming induced a significant (P < 0.001) decrease in the temperature sensitivity (Q10) of soil respiration. Simulated acid rain did not significantly (P > 0.05) impact the Q10 of soil respiration.

Study of Macro‐ and Mesodamage of Remolded Loess under Alternating Dry and Wet Conditions in an Acid Rain Environment

As a national development plan, ecological protection of the Yellow River Basin has attracted extensive social attention in recent years. Considering the influence of acid rain on the engineering characteristics of loess in this area, we investigated changes in the physical and mechanical characteristics of remolded loess under the combined action of acid rain and dry‐wet cycles by means of triaxial tests, nuclear magnetic resonance spectroscopy, and scanning electron microscopy. The results are as follows: in the acidic environment, the stress‐strain relationship of remolded loess undergoes stress hardening after dry‐wet cycling. The cohesion and internal friction angle of remolded loess are negatively correlated with the number of cycles. From the multiscale analysis of the dry‐wet cycle process under acid rain condition, the T2 spectrum of the test soil has three peaks at the micropore level. With the increasing number of cycles, the spectral area increases gradually, and the sample transitions from small pores to large‐ and medium‐size pores. At the microscopic level, the clay mineral particles among soil particles decrease in size, the contact mode between soil particles develops from stable to unstable, the particles are gradually rounded, and the fractal dimension decreases. Chemical erosion and physical erosion are special features of this experiment. Physical erosion causes particle erosion and pore growth, while chemical erosion includes reactions by feldspar. Together, physical and chemical reactions aggravate the soil deterioration process. These research results have laid a good experimental foundation for the ecological protection of the Yellow River Basin.

Changes in Selected Elements of Soils Under Simulated Acid Rain Conditions

Acid rain has been considered a major polluting agent harmful to both terrestrial and aquatic ecosystems. A study was carried out to examine the variations of different elements in Abbottabad soil, Pakistan. The acidification process increases the extraction of different elements from the soil. The extracted concentration of Mg increased in the CL soil after the addition of 1N HNO3 (1:5) by 46.7%, with 1N H2SO4 by 56.3%, and the mixture of both acids 68.1% than untreated CL soil. The average Na concentrations (mg kg-1) of soil suspension (1:5) were achieved among acids as HNO3 (17.2) &gt; HNO3 plus H2SO4 (15.4) &gt; H2SO4 (14.8) &gt; no treatment (8.5). The greater strength of acid released more amounts of an element from the soil. This study indicated a distinct alteration in the composition of soil by acidification practice.

Deterioration of shear strength parameters of limestone joints under simulated acid rain condition

Deterioration of shear strength parameters of carbonate joints under the influence of acid rainwater is a serious concern in rock engineering. Considering this, limestone specimens with planar joints (i.e. joints having roughness coefficient <5) collected from the Lanjiberna limestone mine (in the state of Odisha, India) were investigated. Depreciation of shear strength parameters of the joints concerning short-term exposure to a simulated typical acid rain (i.e. pH 4 solution) condition was evaluated. A total of 24 direct shear tests were performed on natural limestone joints and their degraded equivalents. Both peak shear strength and peak friction angle of a degraded joint are found to be less than those of its natural counterpart. The drop in peak friction angle is found to be 8–10% and 14–19% due to submergence of the joints in pH 4 solution for 5 days and 10 days, respectively. It was ascertained that the deterioration of the asperity strength due to the short-term exposure of the planar joint surfaces to the pH 4 solution overrides the effect of insignificant macroscopic change of the surface roughness caused by solution induced micro-cavities and hence, controls the degradation of the shear strength parameters.

Melatonin-mediate acid rain stress tolerance mechanism through alteration of transcriptional factors and secondary metabolites gene expression in tomato.

Acid rain is a widespread environmental issue intensely affecting normal plant growth of crops. Melatonin is well known pleiotropic molecule which improves abiotic and biotic stress tolerance of plants through physiological and molecular mediation. However, the impact of exogenous melatonin on molecular activities under acid rain conditions in plants has never been studied. The objective of the study is to expose the possible role of exogenous melatonin on physiological and molecular changes against acid rain stress in tomato. Transcriptome profile through RNA-sequence analysis identified 1228, 1120 and 1537 differentially expressed genes (DEGs) in control plant (Ctr) vs simulated acid rain stressed plant (P25) comparison, control plant vs melatonin treatment in simulated acid rain stressed plant (P25M) comparison and P25 vs P25M comparison, respectively. Among them, 152 differentially expressed genes (DEGs) were commonly expressed and the expression of secondary metabolites related gene was noticeably observed in all comparison. Moreover, transcript families such as ERF, WRKY, MYB and bZIP related gene accounted more in all treatment comparison. The RNA-sequence and qPCR results indicated that exogenous melatonin is closely associated with acid rain stress moderator and might be involved in alteration of differentially expressed genes (DEGs), biosynthesis of plant secondary metabolites and transcriptional factor encoding genes expression which might have potential application against environmental hazardous conditions.

Different water environment coupled with ultraviolet radiation on ageing of asphalt binder

Asphalt pavement is inevitably exposed to sunlight and different water environment during the service life, and the environment changes have caused the asphalt to be aged under the more complex environment such as more severe ultraviolet (UV) radiations, acid rain, or deicing salt conditions, however, the ageing mechanism and impact of coupled water and UV radiation is still not clear. In order to evaluate the coupling impact of different water environment (salt, acid) and UV radiation on the rheological properties and microstructure of asphalt material, short-term aged Rolling Thin Film Oven (RTFO) samples were further aged in UV and various water environment to simulate the UV and acid rain or salt condition, the Dynamic Shear Rheological (DSR) test, Bending Beam Rheological (BBR) test, SARA (saturates, aromatics, resin, and asphaltene) four-component analysis test and Fourier Transform Infrared Spectrometer (FTIR) tests were carried out. The results show that the coupling of different water environments and UV radiation accelerated the ageing of asphalt, which leads to the decrease of saturated, aromatic and resin content, the increase of asphaltene, and the enhancement of absorption peaks of carbonyl and sulfoxide groups. The result also found that shorter wavelength UV radiation has a severer effect on asphalt ageing under the same UV radiation level. Highlights UV and different water environment on asphalt ageing were investigated. UV and water ageing reduced the low temperature cracking resistance. UV and water ageing reduced the light component of asphalt and increased the heavy component of asphaltene. Shorter wavelength of UV have a server impact on asphalt ageing.

Applying modified biochar with nZVI/nFe3O4 to immobilize Pb in contaminated soil.

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 8g/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.

Physiological and biochemical responses of tea seedlings (Camellia sinensis) to simulated acid rain conditions.

Tea (Camellia sinensis), widely planted in the south of China, and often exposed to acid rain. However, research concerning the impacts of acid rain on physiology and biochemistry of tea plants is still scarce. In this study, we investigated the influence of simulated acid rain (SAR) on plant height, root length, photosynthetic pigment, Fv/Fm, proline, malondialdehyde, antioxidant enzyme activity, total nitrogen, caffeine, catechins, and free amino acids. Our results showed that SAR at pH 4.5 did not hinder plant development because growth characteristics, photosynthesis, and ascorbate peroxidase and catalase activities did not decrease at this pH compared to those at the other investigated pH values. However, at pH 3.5 and pH 2.5, the activities of antioxidase and concentrations of malondialdehyde and proline increased significantly in response to the decrease of photosynthetic pigments and Fv/Fm. In addition, the increase in acidity increased total nitrogen, certain amino acid content (theanine, cysteine), and decreased catechin and caffeine contents, resulting in an imbalance of the carbon and nitrogen metabolisms. Our results indicated that SAR at pH 3.5 and pH 2.5 could restrict photosynthesis and the antioxidant defense system, causing metabolic disorders and ultimately affecting plant development and growth, but SAR at pH 4.5 had no toxic effects on tea seedlings when no other stress factors are involved.

Crop-litter type determines the structure and function of litter-decomposing microbial communities under acid rain conditions

Acid rain has been one of the major environmental problems in industrial countries. While it may affect the litter decomposition, a highly important microbial-driven biogeochemical process, knowledge about the impact of acid rain on litter-decomposing microbial communities and their functions remains unclear. Therefore, this experiment was conducted to investigate how acid rain treatments would alter microbial communities and their functions during litter decomposition of three major commodity crops (maize, rice, and soybean) for six months from June to December 2018. We used litterbag method to determine litter decomposition,while the phospholipid fatty acid (PLFA) and fluorometric methods were used to reveal changes in the litter-adhering microbial community parameters and activities of enzymes involved in the litter decomposition and nutrient release (including carbon [C], nitrogen [N], and phosphorus [P]), respectively. Our results showed that microbial community composition and functions were significantly different among litter types, but not significantly altered by acid rain treatments during the experimental period. The enzyme activities significantly correlated with each other, thus suggesting that microbial requirements for C, N, and P were coupled together during litter decomposition. Moreover, the enzyme activities, at large, did not correlate to microbial community composition, thus indicating the asymmetric relationship between microbial community structure and functions. Our results imply that crop litter type and substrate availability determined the microbial community composition and functions, while litter-inhabiting microbial communities demonstrated substantial resilience under acid rain pressure throughout the experimental period. These results also predict that litter (crop residues) decomposition may not be altered by acid rains in the subtropical agroecosystem, due to relatively high resilience of litter-decomposing microbial communities.

Investigation of Protective Performance of a Mg-Rich Primer Containing Aluminum Tri-Polyphosphate on AZ91D Magnesium Alloy in Simulated Acid Rain

Mg-rich primer (MRP) containing aluminum tri-polyphosphate functions via a galvanic mechanism to protect AZ91D alloy from corrosion in the 3 wt % NaCl solution. However, its protective performance can be strongly affected by the testing environment. Therefore, it is important to investigate the performance of the primer on magnesium alloys in an acid rain environment. In the present study, the protective performance of MRP with or without aluminum tri-polyphosphate was investigated via open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) in the simulated acid rain. Compared to the primer without aluminum tri-polyphosphate, the MRP containing aluminum tri-polyphosphate pigments exhibited better protective performance in the simulated acid rain condition. In the initial stage, the acidic condition prompted the aluminum tri-polyphosphate pigments to release phosphates and H+ to form magnesium phosphates on Mg particles, retarding their consumption rate. The Mg-rich primer with aluminum tri-polyphosphate can provide cathodic protection to AZ91D alloy for about 49 days in the simulated acid rain solution. Simultaneously, the corrosion products of Mg particles, magnesium oxides and phosphates, precipitated on the Mg particles and improved the stability of the primer. In addition, a protective film, consisting of magnesium oxides and phosphates, formed on the AZ91D substrate. Consequently, all these factors contributed to the long cathodic protection and improved corrosion resistance of MRP containing aluminum tri-polyphosphate in the simulated acid rain.

Effect of graphenene nanoplatelets on microstructure and properties of cement mortar under simulated acid rain

The mortar loses strength under acid rain conditions, causing cracking, weight loss and damage to the structure. This paper studies the effects of graphenene nanoplatelets(GNP) mortar under simulated acid rain conditions. A control sample without GNP and the addition of GNP were ranging from 0.2% to 0.6% by weight of ordinary Portland cement were prepared. In different corrosion days, the mechanical properties of the GNP cement mortar were measured, scanning electron microscopy also applied. Results showed that the mechanical properties of cement mortar added with graphene are improved. Compared with the control sample, the compressive strength and flexural strength of specimens containing 0.2wt% GNP are increased by 10% and 8%, respectively. Adding GNP can improve the acid resistance and durability of cement mortar.

Effects of simulated acid rain on soil respiration and its component in a mixed coniferous-broadleaved forest of the three gorges reservoir area in Southwest China

BackgroundSoil respiration in forest ecosystems is an important part of the forest carbon (C) cycle. Studying the variation patterns of soil respiration under acid rain conditions is critically important for understanding forest C balance and performing rational forest management and operations.MethodsA split-plot design field experiment was performed in a mixed coniferous-broadleaved forest in the Three Gorges Reservoir Area of Jinyun Mountain, Chongqing from January 2016–January 2018. There were 4 main blocks; each was split into untrenched (UT) and trenched (T) treatments. Treatments with four gradient pH levels of 4.5 (control), 4.0, 3.25 and 2.5 were randomly assigned to the untrenched and trenched treatments. The soil CO2 fluxes, soil temperature, and soil moisture content were evaluated under simulated acid rain. Additionally, the effects of soil properties (soil pH, organic C, C:N ratio, microbial biomass, and enzyme activity) on soil respiration were analysed.ResultsThe soil CO2 fluxes exhibited seasonal variation trends. The annual mean soil respiration rates of the UTCK (control), UT4.0, UT3.25, and UT2.5 treatments in untrenched plots were 1.91, 1.91, 1.77, and 1.74 μmol∙m− 2∙s− 1 in 2016 and 1.91, 1.81, 1.55 and 1.37 μmol∙m− 2∙s− 1 in 2017, respectively. The annual mean heterotrophic respiration rates of the TCK (control), T4.0, T3.25, and T2.5 treatments in the trenched plots were 1.39, 1.32, 1.19 and 1.14 μmol∙m− 2∙s− 1 in 2016 and 1.28, 1.18, 1.02 and 0.83 μmol∙m− 2∙s− 1 in 2017, respectively. Acid rain had a significant cumulative effect on soil respiration and heterotrophic respiration (P < 0.01). In 2016, soil respiration was similar in the UTCK versus the UT4.0 treatment but significantly inhibited under higher acidity. In 2017, soil respiration and heterotrophic respiration were significantly decreased by simulated acid rain. The treatments increased the temperature sensitivity of soil respiration but did not significantly affect the soil temperature or moisture content (P > 0.05); moreover, they significantly increased the soil organic C content and C:N ratio, lowered the hydrolysable N and total P concentrations, and lowered the soil pH and fine root biomass at a later experimental stage. Urease and sucrase activities were significantly reduced in the higher-acidity treatments. Soil respiration rate was significantly positively correlated with the soil pH, fine root biomass, and urease and sucrase activity and significantly negatively correlated with the soil organic C and C:N ratio.ConclusionsAcid rain had a significant cumulative and inhibitory effect on soil respiration and heterotrophic respiration, while soil temperature and moisture had a limited effect on soil respiration under simulated acid rain. The variation in soil properties (e.g., soil organic C, C:N ratio, and fine root biomass) caused by acid rain inhibited the microbial utilization of substrates, which was the main cause of the respiration differences.

Enhancement of wear and corrosion resistance of polyvinyl chloride/sorghum straw-based composites in cyclic sea water and acid rain conditions

Plant fiber reinforced polymer composites are experiencing rapid growth in terms of applications where they may be subject to corrosion and wear. The present work explores the possibility of reinforcing polyvinyl chloride (PVC)/sorghum straw (SS) composites with micro-silica (MS) and poly(acrylonitrile-styrene-acrylate) (ASA) for developing a new corrosion and wear-resistant material. Sea water (salinity 3.5%, temperature 55 °C) and acid rain (pH 2.5, temperature 55 °C) were utilized to simulate extreme cyclic corrosion conditions. The results revealed that the wear and corrosion resistance of the PVC/SS composites was significantly enhanced by the addition of 6 wt% MS (particle size 2.6 μm) and 34% ASA, which was attributed to that the MS and ASA could render the PVC matrix with the improved toughness, strength, and heat resistance.

Insights into Heavy Metals Leakage in Chelator-Induced Phytoextraction of Pb- and Tl-Contaminated Soil.

Chelators including DTPA (diethylene triamine pentaacetic acid) and oxalic acid were selected for inducing phytoextraction of heavy metals (HMs) from Pb-, Tl-, and Pb-Tl- contaminated soil, in which heavy metals leakage was highly remarkable. Results showed that compared with the control group without chelating agent under planting conditions, the extraction efficiency (i.e., uptake coefficient) of Pb, Tl increased by 86%, 43% from Pb-Tl- contaminated soil in the presence of oxalic acid, and there was no significant change in heavy metal leakage under rainfall conditions. It was the best phytoremediation scheme in this work. Under rainfall conditions, the HMs concentration in the leachate showed a linear decreasing trend. Acid rain promoted the leakage of heavy metals, and the average leached amount of Tl increased by 1.47 times under acid rain conditions. However, for Pb, DTPA was the main influencing factor, followed by acid rain.

Mechanism of uranium release from uranium mill tailings under long-term exposure to simulated acid rain: Geochemical evidence and environmental implication

To date, there is not sufficient knowledge to fully understand the occurrence, transport and fate of residual uranium (U) from uranium mill tailings (UMT). Herein this study investigated different U release behaviors from natural UMT (without grinding) under four simulated acid rain (pH = 2.0–5.0) compared with controlled scenario (pH = 6.0) for 25 weeks. The results showed that the most notable U release was observed from UMTpH2.0, followed by UMTpH3.0 whereas a nonlinear relationship between pH and U release was observed from UMTpH4.0–6.0. The divergence of U release behaviors was attributed to the presence of minerals such as calcite and clinochlore. Autunite, a secondary mineral formed after leaching, might regulate U release in UMTpH3.0–6.0. Fick theory model revealed the shift of U release mechanism from surface dissolution to diffusion transport for UMTpH2.0, UMTpH3.0 and UMTpH5.0 at varied stage, whereas UMTpH4.0 and UMTpH6.0 displayed univocal dissolution and diffusion mechanism, respectively. This study highlights the necessity of performing long-term leaching tests to detect the “shift event” of leaching kinetics and to better understand the mechanism of U release influenced by mineralogy of the natural UMT under simulated acid rain conditions, which is conducive to developing UMT management strategies to minimize the risk of U release and exposure.

Exogenous Melatonin Improves Fruit Quality Features, Health Promoting Antioxidant Compounds and Yield Traits in Tomato Fruits under Acid Rain Stress.

Acid rain is a serious worldwide environmental problem which reduces the growth and yield of crops. Melatonin, as a pleiotropic molecule has been known to improve stress tolerance by limiting the oxidative damage of plants exposed to adverse environments. However, the role of exogenous melatonin particularly on the yield and antioxidant compounds in tomato fruits under abiotic stress condition remains inexpressible. This observation aims to identify the influence of melatonin treatment under simulated acid rain (SAR) condition on fruit qualities, phenolics, flavonoids, and carotenoids concentration in fruits, and yield of tomatoes. Our study results showed that the fruits of SAR-stressed plants had higher quality traits and antioxidant bioactive compounds by increasing antioxidant activities against SAR-induced oxidative stress compared with fruits of control plants. Nonetheless, these improvements to antioxidant activities in fruits under SAR-condition remained unable to prevent the reduction of the yield. However, SAR-stressed plants treated by melatonin exhibited upgradation on the fruit quality traits, antioxidant compounds and yield attributes through accelerating oxidant-scavenging antioxidant actions in fruits compared with fruits of SAR-stressed plants. Meanwhile, our results suggest that exogenous melatonin plays an important role in improvement of bioactive compounds and yield traits in tomato fruits through regulating antioxidant system.

Serviceability analysis of wood–plastic composites impregnated with paraffin-based Pickering emulsions in simulated sea water–acid rain conditions

In order to enhance the serviceability of sorghum straw/polyvinyl chloride composites in simulated sea water–acid rain conditions, paraffin-based Pickering emulsions stabilized by attapulgite particles were prepared as an anti-corrosion coating of the composites, and a worst-case simulated sea water and acid rain corrosion scenario was employed. The results showed that Pickering coating can have superior leaching resistance in the sea water-acid rain conditions. The coated composites had higher water-resistance and hardness than non-coated composites. The presence of Pickering coating resists the degradation effects of simulated corrosion through better water-resistance and hardness, as well as better mechanical and wear properties of the composites. Prior to the corrosion, the thermal stability of the composites was slightly reduced due to the presence of paraffin, while after 12 d corrosion, Pickering emulsions endowed the coated composites with higher thermal stability than non-coated composites.

Wear Behavior of Alkali-Treated Sorghum Straw Fiber Reinforced Polyvinyl Chloride Composites in Corrosive Water Conditions

The application of wood-plastic composites is growing rapidly in the fields of corrosion and aging. The present study investigated the effect of alkali-treated (with NaOH concentrations of 0.5, 2.5, 4.5, and 6.5%) sorghum straw (SS) fiber on the wear resistance of polyvinyl chloride (PVC) composites under simulated seawater and acid rain conditions. The results showed that the wear resistance of the SS/PVC composites was noticeably improved by the addition of the alkali-treated SS fiber. SS fiber treated with 4.5% NaOH showed low polarity and hydrophilicity with high crystallinity and improved mechanical properties, which endowed the SS/PVC composites with high interfacial bonding and wear resistance. Exposure to simulated seawater and acid rain resulted in the deterioration of physical (including water repellency and hardness), mechanical, thermal, and wear-resistance properties of the composites; the wear mechanism of the SS/PVC composites after corrosion for 12 days was mainly abrasive wear.

Mechanical properties and durability of concrete specimens containing nano silica in sulfuric acid rain condition

During acid rain concrete begins to lose its mechanical strength that lead to cracking, weight losing and finally, destruction of structures. Since the control of acid rain and its effects on the environment is inevitable, many researchers have carried out different studies on this issue and have offered solutions to eliminate or control acid rain’s effects. One of these new methods is to use nanoparticles as cementitious or additive materials. In recent years, several studies have been focused on the nano silica, with the goal of increasing strength and durability of concrete.In this paper, the influence of nano silica on performance of cementitious materials in acid rain condition has been studied. Four concrete mixtures were prepared containing 0–6% of nano silica. Mechanical properties and durability of concrete, such as weight losing, compressive strength, electrical resistance and water absorption in acid rain condition with various pH values will be discussed.The results show that nano silica has positive effects on mechanical properties and durability of concrete specimens. In addition, by increasing the pH value of acid rain, mechanical properties and durability of concrete specimens are improved.

Tracking and erosion resistance of LSR and HTV silicon rubber samples under acid rain conditions

Assessment of the material degradation in laboratory similar to field conditions is still a challenge. In the present work an attempt is made to study the effect of environment conditions in service life of polymeric insulators on tracking and erosion resistance. Evaluation of tracking and erosion resistance of Silicone Rubber insulating samples of high temperature vulcanized (HTV) rubber and liquid silicone rubber (LSR) are carried out under AC and positive polarity DC voltage. The samples are treated under normal contaminants as per IEC 60587 and acidic contaminant solution simulating acid rain. The conditions of pollution/ contamination severity level are taken into consideration by maintaining the conductivity approximately 2.5 mS/cm for both solution to observe the effect of acidity alone on the samples, the acidity level is varied to understand the material behavior under acidic case with AC and DC stress application. A new experimental arrangement is set up based on IEC 60587 and ASTM D-2303 standards. The constant voltage method is employed to find the relative tracking performance of silicone rubber samples for different chemical composition. Physico-chemical analysis involving SEM, EDAX and FTIR is carried out on treated samples to understand the surface morphology and chemical changes. A comparative analysis is carried out for the acid rain solution and the standard solution of NH 4 Cl. Further leakage current performance and analysis is carried under both AC and DC stress.