Acid Rain Conditions Research Articles

Toxicity characterization of metals from various waste printed circuit boards

Abstract Toxicity characterization (TC) of printed circuit board (PCB) of various obsolete electrical and electronic equipment (EEE) was performed. The end-of-life EEE considered in the study include personal computer (PC), laptop, washing machine (WM), television (TV) and air conditioner (AC). The standardized procedures i.e. EP, TCLP, ASTM Method D-3987 and SPLP were employed for toxicity characterization of PCBs in terms of metal leachability against their total metallic contents. Further, the standard SPLP was modified (MSPLP) to imitate Indian acid rain conditions to comparatively assess metal leachability. Except Se, there was statistically significant (P Cu > Zn > Al > Ni > Cd > Se > As > Ba. Except Pb, Cu and Zn, the ASTM procedure at neutral pH showed insignificant metal leachability. Standard SPLP and the MSPLP showed similar effect of Indian and western acid rain conditions on metal leachability. Greater leachability of Pb and Ni simultaneously indicated possible risk to the environment upon e-waste disposal.

A Fringe Projection Based Approach for Corrosion Monitoring in Metals

Corrosion detection and monitoring is a relevant task in many different fields including automotive, naval, civil etc. In the case of artifacts, corrosion is a relevant topic because this process can introduce huge damages on really ancient objects so that preventive procedures and long term monitoring are required. In this specific field the monitoring task presents, in addition, some extra requirements. In fact, monitoring the surface condition without contact, without sampling the object and, possibly, without diminishing the fruition of the handwork is preferable. Optical techniques, in general, are successfully used in many fields where non-contact, high accuracy measurements are required. In particular, an approach based on fringe projection will be explored in this paper. This method mainly consists in projecting a given intensity pattern on the object and in observing the fringe modulation introduced by the object itself; modulation contains information about the contour of the object itself. In this study corrosion tests on bronze alloy were performed both under salt spray and acid rain condition. A sinusoidal fringe pattern was projected on the analyzed samples before starting the measurement and at each advancement step of the corrosion test. Fringe patterns were analyzed using two approaches. Fast Fourier Transform of the recorded patterns was studied to detect if formation of corrosion patina can be related to some variation in the frequency spectrum. Moreover, continuous wavelet analysis was performed to detect where corrosive patina forms.

Galena weathering under simulated acid rain conditions: electrochemical processes and environmental assessments.

Galena can be easily weathered under acid rain conditions and causes environmental issues. This process, in nature, is an electrochemical process. In situ electrochemical technology and surface analysis technology were combined to investigate this weathering process. The experimental results showed that galena weathering under simulated acid rain (SAR) could cause an initial increase in Pb2+ ions and result in the formation of a passive S0 film, and the terminal product was SO42-. Increased acidity stimulates galena weathering, and the promotion efficiency was 2208% as the pH of the SAR decreased from 5.2 to 4.2. The presence of pyrite is favourable for galena weathering, and the promotion efficiency was 150% when contained 25% (wt%) pyrite. Galena will release 1.7 g per m2 per year Pb2+ to solution when the pH of acid rain is 5.2, and the released Pb2+ will reach 95.7 g per m2 per year when the pH of acid rain is 4.2 plus the galvanic effect of pyrite.

Release of nutrients and heavy metals from biochar-amended soil under environmentally relevant conditions.

Biochar is a potential amendment for improving soil fertility due to its richness of nutrients, P, K, Ca, and Mg. However, soil amended with metal-rich biochars may pose a risk of heavy metal release to the environment. Biochars derived from pig manure and sewage sludge (PM-biochar and SS-biochar) were investigated for their nutrient and heavy metal release in two soils (acidic and alkaline soil) under simulated landfill and acid rain conditions. Results showed that under both environmental conditions, adding PM-biochar into the soil increased K, P, and Mg release significantly by about 40-50 times, while only 2-4 times increase of the nutrients was observed in the SS-biochar-amended soil. The Ca release was higher in the SS-biochar-amended soil than in the PM-biochar-amended soil. Higher P, Ca, and Mg nutrient release was observed in alkaline soil than in acidic soil under the two environmental conditions though K release was not significant in both soils. A kinetic study in solution illustrated that the release of nutrients from biochar was initially via desorption and diffusion under environmental conditions and then through slow dissolution of insoluble species. More release of nutrients and heavy metals was observed in the biochar-amended soil under the landfill condition than under the acid rain condition. Although this release was limited under the acid rain condition, leaching of Fe and Mn exceeded the limitations of the groundwater standard value of China. Overall, biochar could be utilized as a prospective soil fertilizer by supplying nutrients such as P, K, Ca, and Mg, while the release of Fe and Mn should be paid more attention due to the risk of these metals impacting groundwater.

Pyrite oxidation under simulated acid rain weathering conditions.

We investigated the electrochemical corrosion behavior of pyrite in simulated acid rain with different acidities and at different temperatures. The cyclic voltammetry, polarization curve, and electrochemical impedance spectroscopy results showed that pyrite has the same electrochemical interaction mechanism under different simulated acid rain conditions, regardless of acidity or environmental temperature. Either stronger acid rain acidity or higher environmental temperature can accelerate pyrite corrosion. Compared with acid rain having a pH of 5.6 at 25°C, the prompt efficiency of pyrite weathering reached 104.29% as the acid rain pH decreased to 3.6, and it reached 125.31% as environmental temperature increased to 45°C. Increasing acidity dramatically decreases the charge transfer resistance, and increasing temperature dramatically decreases the passivation film resistance, when other conditions are held constant. Acid rain always causes lower acidity mine drainage, and stronger acidity or high environmental temperatures cause serious acid drainage. The natural parameters of latitude, elevation, and season have considerable influence on pyrite weathering, because temperature is an important influencing factor. These experimental results are of direct significance for the assessment and management of sulfide mineral acid drainage in regions receiving acid rain.

Wear behavior of straw fiber-reinforced polyvinyl chloride composites under simulated acid rain conditions

In order to investigate the effect of simulated acid rain (SAR) corrosion on the wear-resistance properties of straw fiber/polyvinyl chloride (SPVC) composites, four types of straw fibers (wheat straw (WS), rice straw (RS), corn straw (CS), and sorghum straw (SS) fibers) were utilized and incorporated into poly(vinyl chloride) (PVC). The results show that the SS fibers have high levels of cellulose, lignin and crystallinity, and it also exhibited high adhesion strength with PVC matrix, which endow the SS/PVC with high wear-resistance compared with other three SPVC composites. After SAR corrosion, SPVC composites exhibited severe degradation of the physical, mechanical, and thermal properties, and the fibers were easily pulled out from the matrix to form abrasive particles. The high-speed fiber debris in high-temperature and high-loading environments can be deemed a kind of “incompressible lumps” that will form a certain abrasive wear.

Leaching behavior of veterinary antibiotics in animal manure-applied soils.

Agricultural fields worldwide are being contaminated by the escalating application of veterinary antibiotics (VAs) via animal manure and biosolids applied as fertilizers or of wastewater for irrigation, resulting in soil degradation and damage to the health of terrestrial environments. This paper describes a series of column studies investigating the leaching behavior of five VAs, tetracycline (TC), sulfamethazine (SMZ), norfloxacin (NOR), erythromycin (ERY) and chloramphenicol (CAP), under different simulated rainfall conditions that could occur in agricultural environments. Our aim was to explore the effects of acid rain and torrential rain on the leaching of different VAs and to determine their leaching behaviors along the soil profile. The results showed that acid rain accelerated the accumulation of VAs from animal manure in surface soil while long rainfall durations promoted the downward migration of VAs in soil. Under acid rain conditions, a higher concentration of VAs remained in the animal manure. More VAs were eluted to deeper soil layers and the leachate under extreme rainfall conditions. The leachability of VAs was higher in sandy soil than in clay or loamy soil. SMZ and ERY posed a higher risk to deeper soil layers and groundwater, while NOR and TC tended to persist in surface soil, which can be explained by their different physicochemical properties in soil. Moreover, the general trends from two model assessments and soil column measurements appeared to be in agreement. SMZ had a high leachability, while NOR tended to accumulate in soils. This study provided vital insight into the persistence mechanisms of VAs in terrestrial environments and their potential risks to soils and groundwater.

Chemical characteristics of rainwater in Sichuan basin, a case study of Ya'an.

Rainwater chemistry was investigated at a semi-rural site in Ya'an, Sichuan basin with rain samples collected from May 2013 to July 2014. The rainwater pH values ranged from 3.25 to 6.86, with an annual volume-weighted mean (VWM) of 4.38, and the acid rain frequency was 74%. Such severe acidification, 15% of the total events showed a pH below 4.0, attributed to the deficiency of Ca(2+), significant anthropogenic pollution contribution, and rainy pattern to this area. The annual VWM of total ions concentration was 477.19μeq/L. NH4 (+) was the most abundant ionic species, followed by SO4 (2-), NO3 (-), Ca(2+), Cl(-), Na(+), K(+), Mg(2+), and F(-) in a descending order. The total ionic concentrations presented a seasonal trend of lower values in autumn and summer but higher ones in winter and spring. Based on enrichment factor, correlation analysis and principle component analysis, three factors were identified: factor 1 (NH4 (+), SO4 (2-), NO3 (-), K(+), and Cl(-), 47.45% of the total variance) related to anthropogenic sources (coal/fuel combustion, biomass burning and agriculture), factor 2 (Ca(2+), Mg(2+), Na(+), and Cl(-), 34.01% of the total variance) associated with natural sources, and factor 3 (H(+), 11.78% of the total variance) related to free acidity. Back trajectory analysis indicates that the rainwater chemistry in Ya'an was mainly affected by regional air masses from Sichuan basin. Long-range transported air masses from southwest with heavy anthropogenic pollution increased the total ion concentration and acidity of rainwater. Considering its special topography, anthropogenic emissions from regional and long-range transport (especially from southwest) must be controlled effectively to improve the acid rain condition of non-urban areas in Sichuan basin.

Atmospheric wet deposition of trace metals in the Suwon region in Korea during farming periods

This study investigated the characteristic distributions of heavy metals in rainwater, and the relationship between the concentrations of heavy metals and other chemical properties of the rainwater was also evaluated. Chemical properties of the rainwater varied between different raining periods and years. The volume-weighted mean of rainwater pH ranged from 3.9 to 6.7, and the individual volume-weighted means followed the order Zn > Pb > Cu > Cr > Ni > Cd. There were positive correlations between the major ionic components, such as Ca, Mg, and K, and the heavy metal concentrations of rainwater. The trends of monthly heavy metal concentrations showed higher values in July during 2011-2013. The order of average enrichment factors (EFs) was Cd > Pb > Cu > Zn > Ni > Cr; all of these were relatively higher than the EFs of natural components such as Fe, Mg and Ca. The overall finding of this study indicated that the concentration of dissolved trace metals can increase under the condition of acid rain.

A morphological and electrochemical comparison of the corrosion process of aluminum alloys under simulated acid rain conditions

The corrosion behavior of aluminum 6060 and 6082 alloys was examined by scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic electrochemical impedance spectroscopy (DEIS) after exposure to simulated acid rain for 1, 5, 24 and 48 h. The electrochemical parameters obtained from DEIS were compared with the AFM and SEM studies. Results showed that DEIS is a sensitive technique detecting even very moderate changes in charge-transfer resistance (Rct); it exhibits a very good correlation with surface morphological changes in relation to exposure time. This research also demonstrated the importance of performing corrosion measurements after a longer time period.

Aging effect on the leaching behavior of heavy metals (Cu, Zn, and Cd) in red paddy soil.

Aging effect can influence the fractions distribution and mobility of metals after they are added into soil. In this study, incubation and soil column experiments under simulated acid rain condition were conducted to evaluate aging effect on the leaching characteristic of Cu, Zn, and Cd in artificial polluted red paddy soil. Our results showed that aging effect reduced metal contents in exchangeable and HoAc soluble fractions. Power function was the most excellent to describe the variation of exchangeable fraction, while pseudo first- and second-order functions were more successful to describe the leaching characteristic of metals from soil columns. The leaching amount of the metals from the polluted soil only accounted for a small part of their total content in soil, and the leachability of Cu was the weakest. Both the exchangeable and HoAc soluble fraction were available as indicators to evaluate the leachability of metals in red paddy soil. The shorter time the soil was contaminated, the more amounts of metals released from the soil. The reduction of exchangeable fraction caused by aging effect was the main reason for the decrease of metal mobility in soil.

Numerical Simulation on U(VI) in Uranium Tailing Impoundment Affected by Acid Rain

As acid rain getting more and more serious, increasing attention is given to environmental effect assessment of uranium tailings under the condition of acid rain. In the paper, influence of acid rain to partitioning coefficient (Kd) of U(VI) in soil was studied, and migration of radionuclide uranium in soil was simulated by computer. The static experiment results showed that the Kd value of U(VI) in soil reaches minimum value when pH is 2.0. When 2.0<pH<3.5, the Kd showed a rising tendency;The Kd in soil reaches maximum value when pH is 3.5. And when 3.5<pH<8.0, the Kd showed a decreasing tendency. This paper has taken a large uranium tailings impoundment in South China as an example studied by VisualModflow. After setting up models of groundwater movement and radionuclide migration in the study area, migration tendency of radionuclide U(VI) was simulated and pollution of radionuclide to environment was predicted. The results of simulation show that the migration of uranium speed to be the slowest when pH = 2.0, and the figure to be the fastest when pH = 3.5. Furthermore, maximum speed is about 1.24 times of minimum speed.

Investigation of corrosion behavior of 6060 and 6082 aluminum alloys under simulated acid rain conditions

Instantaneous impedance changes of 6060 and 6082 type aluminum alloys in pure water, and simulated acid rain poured into the pure water was investigated by dynamic electrochemical impedance spectroscopy (DEIS). In this way, the influence of aluminum content on the corrosion behavior of 6060 and 6082 type aluminum alloys immersed in simulated acid rain was determined. The corrosion rate of the alloy decreased with increasing Al content, which may be related to the distribution of the Al‐rich phase. The surface morphology of studied alloys was also examined with scanning electron microscopy.

On the potential high acid deposition in northeastern China

AbstractThere is an acid deposition conundrum in China: contrary to conventional wisdom, extremely high ambient sulfate concentrations in northeastern China are not always accompanied by correspondingly high acidities. To investigate this discrepancy, data from two independent sets of in situ field measurements were analyzed along with Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) satellite observations and Model for Ozone and Related chemical Tracers (MOZART) chemical transport model calculations. The field measurements included soluble aerosol ion concentrations and pH and particulate data from 11 cities, as well as pH measurement data from 74 sites in China. This study explores the basis for and the impacts of the large discrepancy in northeastern China between the major acidity precursors (SO2 and NOx) and measured acidity levels as indicated by pH values. There are extremely high SO2 emissions and ambient concentrations in northeastern China, while the corresponding acidity is unusually low (high pH) in this region. This is inconsistent with the usual situation where high‐acidity precursor pollutants result in low pH (high acidity) values and acid rain conditions. In other regions, such as southern China and the United States, high SO2 concentrations are typically well correlated with high acidities. Using measured soluble particle measurements (including both positively and negatively charged ions), it is seen that there are high values of alkaline ions in northeastern China that play an important role in neutralizing acidity in this region. This result strongly suggests that the high alkaline concentrations, especially Ca2+, increase warm season pH values by about 0.5 in northern China, partially explaining the inconsistency between sulfate concentrations and acidity. This has a very important implication for acid rain mitigation—especially in northeastern China. However, there are additional issues pertaining to the precursor‐acidity relationship that need further investigation. Why is it that the reduction in acidity due to the alkaline ions is only significant in summer? During winter, the measured alkaline ions play a much smaller role in explaining the discrepancy. The measured alkaline ions in this study were mostly obtained from particles in the PM2.5 range. However, the size of calcium particles is typically much larger—extending well beyond 2.5 µm—and so a significant amount of calcium may be underestimated by PM2.5 measurements alone. The under‐sampling of calcium particles is further exacerbated in that the sampling protocol excluded particle (and soluble ion and pH) measurements during dust storms. This all leads to the need for an improved understanding of pollutant‐ion‐particulate interactions in China, and their role in explaining the counter‐intuitive conclusion that dust mitigation strategies in China could have the unintended consequence of exacerbating acid rain conditions.

Antioxidant response of soybean seedlings to joint stress of lanthanum and acid rain

Excess of rare earth elements in soil can be a serious environmental stress on plants, in particular when acid rain coexists. To understand how such a stress affects plants, we studied antioxidant response of soybean leaves and roots exposed to lanthanum (0.06, 0.18, and 0.85 mmol L(-1)) under acid rain conditions (pH 4.5 and 3.0). We found that low concentration of La3+ (0.06 mmol L(-1)) did not affect the activity of antioxidant enzymes (catalase and peroxidase) whereas high concentration of La3+ (≥0.18 mmol L(-1)) did. Compared to treatment with acid rain (pH 4.5 and pH 3.0) or La3+ alone, joint stress of La3+ and acid rain affected more severely the activity of catalase and peroxidase, and induced more H2O2 accumulation and lipid peroxidation. When treated with high level of La3+ (0.85 mmol L(-1)) alone or with acid rain (pH 4.5 and 3.0), roots were more affected than leaves regarding the inhibition of antioxidant enzymes, physiological function, and growth. The severity of oxidative damage and inhibition of growth caused by the joint stress associated positively with La3+ concentration and soil acidity. These results will help us understand plant response to joint stress, recognize the adverse environmental impact of rare earth elements in acidic soil, and develop measures to eliminate damage caused by such joint stress.

Corrosion Behavior of 35CrMn and Q235 Steel in Simulated Acid Rain Conditions

Effects of pH value, chloride ion concentration and alternation of wetting and drying time in acid rain on the corrosion of 35CrMn and Q235 steel were investigated through the measurement of polarization curves, electrochemical impedance spectroscopy, x-ray diffraction, and quantum mechanical calculations. The corrosion rate of 35CrMn and Q235 steel increased with decreasing pH values of the simulated acid rain, whereas the corrosion potential of 35CrMn and Q235 steel became more negative. The impedance became higher and the corrosion rate decreased with increasing test time. The dissolution rate of samples increased with chloride ion concentration. Results suggested that the corrosion rate of 35CrMn steel was obviously lower than that of Q235 steel for a more compact rust, α-FeOOH. Quantum chemical calculations further revealed that the increase in corrosion rate of the steel resulted from pitting corrosion caused by the corrosive chloride ion.

Influence of SiC, SiO2 and graphite on corrosive wear of bronze composites subjected to acid rain

Abstract Sintered aluminum bronze friction materials have been successfully used in clutches and breaks for heavy-duty applications, due to their good wear resistance, cold workability, fatigue resistance and corrosion resistance. The aim of the present work is the preparation and investigation of bronze-based composites for components subjected to motion in aqueous environments. Three of bronze-based composites with different amounts of slide additive (graphite) and friction additives (SiC, SiO2) were prepared by powder metallurgy. The microstructure profiles of the obtained composite materials were characterized by uniform distribution of SiC, SiO2 and graphite particles within the bronze matrix. The porosity decreased with increase in the number of pressing and sintering processes. High Vickers hardness values were registered for samples with higher reinforcement contents. A combination of electrochemical and gravimetric techniques was used in this study to assess corrosive wear rates of these materials under neutralized as well as acid rain conditions. Increasing both slide and friction additives improved the corrosion resistance of these bronze composites. Samples with 1.5% graphite, 3% SiO2 and 3% SiC had the highest corrosive wear resistance in neutralized as well as in acid rain due to the high amount of anti-friction and slide additives, in addition to low porosity.

Report: Potential environmental impact of exempt site materials — a case study of bituminous road planings and waste soils

The use of waste materials for ecological benefit, agricultural improvement or as part of construction works are often exempt from waste management control in order to maximize the reuse of material that would otherwise be disposed of to landfill. It is important, however, to determine whether there is potential for such waste to cause environmental harm in the context of the basis for granting exemptions under the relevant framework objective to ensure that waste is recovered or disposed of without risk to water, air, soil, plants or animals. The potential for environmental harm was investigated by leaching studies on two wastes commonly found at exempt sites: bituminous road planings and waste soils. For bituminous road planings, the organic components of the waste were identified by their solubility in organic solvents but these components would have low environmental impact in terms of bioavailability. Leaching studies of the heavy metals copper, lead and zinc, into the environment, under specific conditions and particularly those modelling acid rain and landfill leachate conditions showed that, except for copper, the amounts leached fell within Waste Acceptance Criteria compliance limits for defining waste as inert waste. The fact that the amount of copper leached was greater than the Waste Acceptance Criteria level suggests that either additional testing of wastes regarded as exempt should be carried out to ensure that they are in analytical compliance or that legislation should allow for the potential benefits of reuse to supersede deviations from analytical compliance.

Kinetics of soil cadmium desorption under simulated acid rain

Soil acidification can result in the release of heavy metals stabilized by soil components into soil solution, and therefore it causes ecological risk. The kinetics of Cd desorption from two Chinese soils (ultisol and oxisol) distributed in the acid rain sensitive areas of southern China, were studied using a flow-stirred method under simulated acid rain conditions. Cd desorption was well described by the first-order kinetic equation. Percentages of Cd desorbed were 80–99% in ultisol and 25–28% in oxisol, respectively. Cd desorption, regarded as a heterogeneous diffusion in soils, could be also fitted by the Elovich equation. The desorption process could be divided into a fast reaction and a slow reaction, which were corresponded to the exchangeable and the specific sorbed Cd, respectively. The obtained results are essential to understand the process of heavy metal release under acid deposition conditions and to evaluate the ecological risk of acid deposition in those acid rain sensitive areas of China.

Canopy leaching of subtropical mixed forests under acid rain

Leaching of major ions from acid precipitation in a subtropical forest was examined based on an experiment in four sample sites in Shaoshan City, Hunan Province, China, from January 2001 to June 2002. Results clearly show that when rain passed through the canopy, pH increased and the evidence of ion uptake was presented for SO42−, NO3−, Mg2+ and NH4+ ions, especially of NH4+ and NO3−. The percentages of dissolved SO42−, Ca2+ and Mg2+ show a decreasing trend with increasing rainfall. Percentages of leaching Ca2+, K+ and Cl− ions show an increasing trend as a function of increased pH values. The forest canopy in Shaoshan City has a strong effect on the uptake of SO42− and NO3− ions under acid rain conditions. The decreasing order of ions leaching in the forest canopy is as follows: K+ > Ca2+ > Cl− > Mg2+ > SO42− > NO3− > NH4+ > Na+.