Rainfall Acidity Research Articles

Risk mitigation by waste-based permeable reactive barriers for groundwater pollution control at e-waste recycling sites

Permeable reactive barriers (PRBs) have proved to be a promising passive treatment to control groundwater contamination and associated human health risks. This study explored the potential use of low-cost adsorbents as PRBs media and assessed their longevity and risk mitigation against leaching of acidic rainfall through an e-waste recycling site, of which Cu, Zn, and Pb were the major contaminants. Batch adsorption experiments suggested a higher adsorption capacity of inorganic industrial by-products [acid mine drainage sludge (AMDS) and coal fly ash (CFA)] and carbonaceous recycled products [food waste compost (FWC) and wood-derived biochar] compared to natural inorganic minerals (limestone and apatite). Continuous leaching tests of sand columns with 10wt% low-cost adsorbents were then conducted to mimic the field situation of acidic rainfall infiltration through e-waste-contaminated soils (collected from Qingyuan, China) by using synthetic precipitation leaching procedure (SPLP) solution. In general, Zn leached out first, followed by Cu, and finally delayed breakthrough of Pb. In the worst-case scenario (e.g., at initial concentrations equal to 50-fold of average SPLP result), the columns with limestone, apatite, AMDS, or biochar were effective for a relatively short period of about 20-40 pore volumes of leaching, after which Cu breakthrough caused non-cancer risk concern and later-stage Pb leaching considerably increased both non-cancer and lifetime cancer risk associated with portable use of contaminated water. In contrast, the columns with CFA or FWC successfully mitigated overall risks to an acceptable level for a prolonged period of 100-200 pore volumes. Therefore, with proper selection of low-cost adsorbents (or their mixture), waste-based PRBs is a technically feasible and economically viable solution to mitigate human health risk due to contaminated groundwater at e-waste recycling sites.

Heavy Metal Migration and Potential Environmental Risk Assessment During the Washing Process of MSW Incineration Fly Ash and Molten Slag

Based on the simulated moderate acid rainfall condition, MSW fly ash and molten slags were washed to investigate the effect of alkalinity on the migration and the speciation transformation of heavy metals in the approaching natural environment. All the samples were washed 150min at 25̊C with the 100ul/min flow speed, then the after-washing samples were placed at air atmosphere for 60 days to get dried after-washing fly ash and molten slag samples. The total concentration of heavy metals in raw fly ash was followed by Zn>Pb>Cu>Cr>Cd>As>Ni, After washing process, the order is still the same, and the content of heavy metals in fly ash were significantly increased due to soluble salt leaching, especially Cr, Cu, Ni, Zn. The potential ecological risk (PEI) analysis, using STI toxicity model, indicated that PEI index of fly ash after washing was 2.3 times than that before washing. Therefore, it will cause greater ecological risk for the open storage of fly ash. When the fly ash was converted into molten slag, the alkalinity in the range between 0.8 and 1.2 was benefical for reducing PEI index of molten slags. The ash molten slag can be directly used as roadbed material due to the good solidification effect of heavy metals.

ECOLOGICAL IMPACT OF WIND-DIESEL POWER PLANTS ON ECOSYSTEM AND POPULATION HEALTH

In electrification of the Eastern regions of Russia, an important part is assigned to the small-scale power distributed generation. In this regard, it is actual to construct wind-diesel power plants (WDPP), which impact on humans and environment is so far poorly studied. The results of a theoretical research of WDPP negative impact on health of the population and ecosystem of the territories of the East of Russia which were not covered by the centralized power supply have been given in the article. The assessment of indicators of atmospheric air pollution (specific and absolute values of the specified mass of annual emission of harmful substances, volumes of greenhouse gases emission, formation of acid rainfall, substances causing eutrophication) and physical pollution (noise, electromagnetic field) during use of WDPP of various rated capacity. Calculations have been done for 692 types of diesel engines and 97 models of wind power installations. The received results were compared with the level of environmental pollution during work of large thermal power plants. There have been given graphic dependences of the specified mass of the emitted harmful substances on power of the diesel engines, a noise level created by the wind power installations, on remoteness of settlements and power of the power installations, as well as a ratio of volume of harmful substances annual emission in the atmosphere during work of WDPP and the large thermal power plants. It has been shown that electrification of the Eastern regions of Russia on the basis of development of small-scale power distributed generation would have an ecological focus.

Effect of Mineralogy on Durability and Strength of Hornfelsic Rocks under Acidic Rainfall in Urban Areas

In order to assess mineralogical composition influence on durability and strength of rocks, four samples of hornfelsic rocks were selected from southern and western parts of the city of Hamedan, west of Iran. These rock samples were subjected to mineralogical, physical and mechanical tests in the laboratory. Also, they were evaluated in 15 cycles of slake-durability testing in different pH of sulfuric acid solutions and XRD analysis. Based on the results, the type and amount of minerals, their density and hardness had an influence on the uniaxial compressive strength and the slake durability index of tested rocks. That means, presence of non-dissolved minerals such as graphite in studied rocks, decreases Unconfined Compressing Strength (UCS) but increases the slake durability index. The results of slake-durability test indicated that weight loss of the samples at initial cycles was found to be higher than the end cycles. Also, in these samples, initial minerals in the fresh samples were not exchanged by secondary minerals such as clay minerals. Therefore Hamedan hornfelsic rocks are approximately resistant when were put under accelerated chemical weathering and degradation in the laboratory and natural chemical weathering.

Interacting controls on innate sources of CO2 efflux from a calcareous arid zone soil under experimental acidification and wetting

More than half of global soil carbon is stored as carbonates, primarily in arid and semi-arid zones. Climate change models predict more frequent and severe rainfall events in some parts of the globe, many of which are dominated by calcareous soils. Such events trigger substantial increases in soil CO2 efflux. We hypothesised that the primary source of CO2 emissions from calcareous, arid zone soil during a single wetting event is abiotic and that soil acidification and wetting have a positive, potentially interacting, effect. We manipulated soil pH, soil moisture, and controlled soil respiration by gamma irradiating half of an 11 day incubation experiment. All manipulated experimental treatments had a rapid and enormous effect on CO2 emission. Respiration contributed ca. 5% of total CO2 efflux; the major source (carbonate buffering) varied depending on the extent of acidification and wetting. Maximum CO2 efflux occurred when pH was lowest and at intermediate matric potential. CO2 efflux was lowest at native pH when soil was air dry. Our data suggest that there may be an underestimate of soil-atmosphere carbon fluxes in arid ecosystems with calcareous soils. There is also a clear potential that these soils may become net carbon sources depending on changes in rainfall patterns, rainfall acidity, and future land management. Our findings have major implications for carbon cycling in arid zone soil and further study of carbon dynamics in these terrestrial systems at a landscape level will be required if we are to improve global climate and carbon cycling models.

Assessment of physical weathering effects on granitic ancient monuments, Hamedan, Iran

Ancient monuments are significant for the cultural identity of countries and they are also very important from economical point of view. There are a lot of environmental damages that affect building materials and monuments. Therefore, the preservation of the monuments has become a vital challenge. Gradual natural destructive factors including freezing and thawing, heating and cooling, salt weathering and acidic rainfall play an important role in destruction of monuments. In this study, for assessment of weathering effects on engineering properties of Hamedan granitic monuments, heating and cooling (up to 600 cycles), freezing and thawing (up to 300 cycles), and salt weathering (up to 50 cycles) tests have been performed. Also, in order to estimate the deterioration of the Ganjnameh inscriptions, four inscriptions were prepared and subjected to heating and cooling (up to 600 cycles), freezing and thawing (up to 300 cycles), magnesium sulfate salt weathering (up to 60 cycles), and acidic rain (up to 1 year time) tests. The results showed that when compared with that of salt weathering, the effects of heating–cooling and freezing–thawing weathering were negligible. Also, deterioration effect of magnesium sulfate on weight loss has been observed more remarkably than that of sodium sulfate. The deterioration effect of sodium sulfate on loss of engineering properties was evaluated more effectively than that of magnesium sulfate. Simulation of the Ganjnameh inscriptions behavior subjected to the weathering tests indicated that deterioration effect of sulfate solution was more effective than that of other weathering processes.

The hydrochemistry properties of precipitation in karst tourism city (Guilin), Southwest China

A comprehensive study on the chemical compositions of rainwater was carried out from January 2008 to November 2011 in Guilin, China. The 396 samples were analyzed for pH and electrical conductivity, and 44 among of 396 samples were analyzed for major ions. The result shows that pH value ranges from 3.44 to 7.16, and the occurrences of acid rain may increase with natural factors and human activities. The order of the main ion concentration in precipitation is SO4 2− > Ca2+ > NH4 + > NO3 − > Cl− > Na+ > F− > Mg2+ > K+ (weighted average). The correlation of the main cations, neutralization factors (NF), enrichment factor, and ionic ratio shows that acid rain can be mitigated slightly by the neutralization effect of a large amount of alkali ions. The SO4 2−, NO3 −, NH4 +, and a fraction of Ca2+ may originate from emissions of human activities, and the K+, Mg2+, and a majority of Ca2+ may originate from weathering of soil and rock. Mg2+ may transport long distance from large cities in the surrounding area. Among them, hyper-accumulation of NO3 − is produced by lots of vehicle and festival emissions. The hydrochloride may increase rainfall acidity, which refers to the temporary acidity. In addition to the input of pH value and acid ions, the input of alkali ions should be considered in the future evaluation of acid deposition in cites.

Terrestrial acidification during the end-Permian biosphere crisis?

Excessive acid rainfall associated with emplacement of the Siberian Traps magmatic province is increasingly accepted as a major contributing factor to the end-Permian biosphere crisis. However, direct proxy evidence of terrestrial acidification is so far not available. In this paper, we seek to determine the probability that relative proportions of extractable monophenolic components from soil-derived organic matter in marine sediments provide a molecular proxy for estimating soil acidity. Intermittently low and high ratios of vanillic acid to vanillin detected in latest Permian and earliest Triassic deposits of the southern Alps, Italy, support concepts of pulses of severe acidification (pH <4) during the main phase of the biosphere crisis.

Leaching of Lead from Geopolymer Prepared by Waste Acid Residue

The waste acid residue is limestone neutralized slag in the preparation of acid with pyrometallurgical exhaust in lead production enterprises. There are many hazardous heavy metals in the slag, such as lead, mercury, cadmium, arsenic, etc. It is difficult to remove them from the waste acid residue. The leakage of the heavy metals will gradually get into the groundwater and the soil, contaminate the surrounding environment. However, the waste acid residue can be used to prepare geopolymer in order to solidify the toxic elements. The present experiment aimed to investigate the leakage rate of lead from the geopolymer made by the waste acid residue. The samples were lixiviated by a mixture of sulfuric and nitric acid, with the mass ratio of sulphuric acid/ nitric acid 2:1. The ratio of liquid to solid was 10:1. And the geopolymer was oscillated for 18hours on the turnover oscillation. The leaching of lead under influence of acidic rainfall and then entering into the environment was simulated. The lead in the supernatant of leaching solution under different conditions was analyzed. And the result showed that lead can be well solidified in the geopolymer made by the waste acid residue.

Immobilization of Cd, Zn, and Pb from Soil Treated by Limestone with Variation of pH Using a Column Test

Decades of mining in South Korea have resulted in the contamination of large amounts of soil by metals. The most feasible approach to site restoration requires the use of a stabilization agent to reduce metal mobility. This study examined the leaching characteristics of limestone used as a stabilization agent when subjected to solutions of differing pH. In a laboratory-scale column test, solutions with pH values of 3.5, 4.6, and 5.6, representing acidic to nonacidic rainfall, were applied to soil mixed with limestone. Test results indicate that metal components can be released with the addition of acidic solutions, even if the soil is highly alkaline. Cd and Zn, in particular, exhibited abrupt or continuous leaching when exposed to acid solutions, indicating the potential for contamination of water systems as metal-laden soils are exposed to the slightly acidic rainfall typical of South Korea. Treatment using stabilization agents such as limestone may reduce leaching of metals from the contaminated soil. Stabilizing metal-contaminated farmland is an economical and feasible way to reduce pollutants around abandoned metal mines.

석조문화재 보수물질로의 적용을 위한 무기질 바인더 안정성 연구

석조문화재 보수물질로서의 적용을 위해 무기질 바인더를 시험하였다. 순수 무기질 바인더와 첨가제를 배합한 3종을 시편으로 제작하였고 거창화강석에 무기질 바인더 시편들을 부착시켜 무기질 바인더가 암석에 미치는 영향을 분석하였다. 무기질 바인더와 반응시킬 pH 4.0과 pH 5.6 수용액을 국내 강우의 산성도와 함유이온을 토대로 제조하였다. pH 8.0 약알칼리수와 pH 6.85 탈이온수를 준비하여 산성수의 대조군으로 적용하였다. 물반응 후 무기질 바인더 시편의 무게 감소는 시편의 종류에 따라서는 컸지만 물의 산성도와 상관성은 적었다. 순수 무기질 시편의 압축강도가 가장 컸으나 물반응 후 감소율이 가장 크다. 큰 흡수율은(<TEX>$6.72-12.44kg/m^2{\cdot}t^{1/2}$</TEX>) 무기질 바인더로부터 용출된 이온 함량과 상관성이 크다. 모든 액성의 수용액이 무기질 바인더와 반응 후 pH 9.0-10.0로 변화하였으며, 수용액에서는 무기질 바인더에서 용해된 <TEX>$Mg^{2+}$</TEX>와 <TEX>$K^+$</TEX>이 다량 검출되었다. 용해된 이온들은 수용액 내 음이온들과 결합하여 높은 용해도를 지닌 <TEX>$MgSO_4{\cdot}nH_2O$</TEX> 및 <TEX>$KNO_3$</TEX>와 같은 백색염을 형성하였다. 암석강화제와 발수제를 처리한 무기질 바인더 시편에서는 이온량이 급격하게 감소하였다. Inorganic binders were studied in order to apply a conservation material for stone monument. A pure inorganic binder and 3 species of inorganic binder which contain additives on the basis of a pure inorganic binder were selected as test samples. Through the application of inorganic binders on Geochang granite investigate their influences on stone. pH 4.0 and 5.6 acid solution, respectively were manufactured on the basis of the acidity of domestic rainfall. Alkaline water with pH 8.0 and deionized water with pH 6.85 were prepared as control group. Changes in weights of inorganic binders were not definite according to the acidity of water while weight losses in inorganic binder type were greater after reaction with the water. The compressive strengths of pure inorganic binder was largest before the test but its decrease rate were larger after reaction with the water. Water absorption rate of inorganic binders are 6.72 to <TEX>$12.44kg/m^2{\cdot}t^{1/2}$</TEX> after reaction with the water. Such high absorption was considered that it forced water to move deep into inorganic binder and made the components of inorganic binder dissolve. Acidities of the water of pH 4.0, 5.6, 6.85 and 8.0, respectively were changed to pH 9.0-10.0 after reaction with the inorganic binders. Ion concentrations in the water changed after reaction with the inorganic binders and <TEX>$Mg^{2+}$</TEX>, and <TEX>$K^+$</TEX> significantly increased, dissolved from the binder. The high concentration of ions detected showed that the binder reacted with water and formed white salts with high solubility such as <TEX>$MgSO_4{\cdot}nH_2O$</TEX>, <TEX>$KNO_3$</TEX>. Ion concentrations significantly decreased from the binder after treatment with consolidant and water repellent.

A study of deterioration of reinforced concrete beams under various forms of simulated acid rain attack in the laboratory

This paper studies the behaviour of deteriorated reinforced concrete (RC) beams attacked by various forms of simulated acid rain. An artificial rainfall simulator was firstly designed and evaluated. Eleven RC beams (120 mmx200 mmx1800 mm) were then constructed in the laboratory. Among them, one was acting as a reference beam and the others were subjected to three accelerated corrosion methods, including immersion, wetting-drying, and artificial rainfall methods, to simulate the attack of real acid rain. Acid solutions with pH levels of 1.5 and 2.5 were considered. Next, ultrasonic, scanning electron microscopy (SEM), dynamic, and three-point bending tests were performed to investigate the mechanical properties of concrete and flexural behaviour of the RC beams. It can be concluded that the designed artificial simulator can be effectively used to simulate the real acid rainfall. Both the immersion and wetting-drying methods magnify the effects of the real acid rainfall on the RC beams.

酸雨胁迫下樟树林降水中无机阴离子变化特征

对城市大气降水及城市樟树林穿透水、树干茎流、地表径流中的SO₄^2-、NO₃^-、Cl^-、NO₂^-、 F^-、Br^-、PO₄^3-7种水溶性无机阴离子进行了定位测定,Br^-、PO₄^3-未检出;主要的阴离子为SO₄^2-、NO₃^-,二者占总阴离子含量比例最大,占到75.6%-89.0%,且在水文学各分量中变异系数均值都很稳定,变动幅度在0.40-0.47;在各分量中SO₄^2-、NO₃^-、Cl^-、NO₂^-、F^-含量变化较大:大气降水、树干茎流中均为SO₄^2- > NO₃^- > Cl^- > F^- > NO₂^-,穿透水为SO₄^2- > NO₃^- > Cl^- > NO₂^- > F^-,地表径流为NO₃^- > SO₄^2- > Cl^- > F^- > NO₂^-;穿透水SO₄^2-、NO₃^-、Cl^-、F^-、NO₂^-淋溶系数分别为3.83、2.61、4.18、4.32、16.06,树干茎流SO₄^2-、NO₃^-、Cl^-、F^-、NO₂^-淋溶系数分别为7.52、3.55、4.29、2.76、3.10,地表径流SO₄^2-、NO₃^-、Cl^-、F^-、NO₂^-淋溶系数分别为2.60、4.74、5.00、3.01、3.56,表明阴离子在樟树林水文学过程中均表现出不同程度的富集效应;大气降水中PH均值为4.77,SO₄^2-/NO₃^-当量比值为1.1,属于硫酸-硝酸混合型酸雨;大气降水SO₄^2-、NO₃^-、Cl^-、F^-与穿透水中SO₄^2-、NO₃^-、Cl^-、F^-对应呈显著性正相关(<em>P</em> < 0.01),大气降水NO₃^-与树干茎流NO₃^-呈显著性正相关(<em>P</em> < 0.01),地表径流中SO₄^2-、Cl^-与穿透水、树干茎流中SO₄^2-、Cl^-对应呈显著性正相关(<em>P</em> < 0.01),说明樟树林能够吸附大气中的酸性物,让酸性养分于自身系统内部吸收、迁移、络合,从而起到净化大气的效用;穿透水pH与地表径流NO₃^-、NO₂^-呈显著性负相关(<em>P</em> < 0.01),与地表径流SO₄^2-呈显著性正相关(<em>P</em> < 0.05),表明NO₃^-、NO₂^-有助于促进地表水的酸化,而SO₄^2-有利于缓解地表水的酸化;穿透水pH均值5.62,对酸雨起到中和作用,树干茎流pH均值4.61,有被酸化趋势,地表径流pH均值7.19,接近中性.;Changes in 7 water-soluble ions including SO₄^2-、NO₃^-、Cl^-、NO₂^-、 F^-、Br^-、PO₄^3- of rainwater were investigated in Camphor forest ecosystems in Changsha city, Hunan Province of China. Water samples were taken as rainfall above the forest canopy, throughfall, stemflow and surface runoff in the forests. The result showed that Br^- and PO₄^3- were not detected in all water samples. Both SO₄^2- and NO₃^- were the major inorganic anions in waters under Camphor forests, which accounted for 75.6-89.0% of the total anion contents in the forest ecosystems. The contents of anion decreased in an order: SO₄^2- > NO₃^- > Cl^- > F^- > NO₂^- in rainfall and stemflow; SO₄^2- > NO₃^- > Cl^- > NO₂^- > F^- in throughfall and NO₃^- > SO₄^2- > Cl^- > F^- > NO₂^- in surface runoff. The leaching coefficients were 3.8, 2.6, 4.2, 4.3 16.1; 7.5, 3.6, 4.3, 2.8 3.1; and 2.6, 4.7, 5.0, 3.0 3.6 for SO₄^2-, NO₃^-, Cl^-, F^-, NO₂^- in throughfall, stemflow and surface runoff, respectively. The pH value averaged 4.77 in rainwater and the ratio of SO₄^2-/NO₃^- was 1.1 in the study area, which indicated that the rainwater was a sulfuric-nitric mixed acid rain. A significant positive correlation was found between rainfall and throughfall for all anions, except for NO₂^-. The NO₃^- in rainfall was significantly and positively related to that in stemflow. There were a positive relationship of SO₄^2- and Cl^- between throughfall and stemflow and surface runoff. The pH was 5.62, 4.61 and 7.19 in throughfall, stemflow and surface rounff, respectively.Our results demonstrated that Camphor forest ecosystems had a relative high ability to purify acid rainfall through adsorbing, uptaking, leaching and neutralizing processes.

Corrosion of Concrete Using Portland Composite Cement and Rice Husk Ash under Simulated Acid Rain Environment

Cement production, which results in higher CO2 levels, has a negative impact on environment. This phenomenon has caused the emergence of a new type of environmentally friendly cement, such as Portland Composite Cement (PCC). On the other hand, rainfall becomes high acidity level. This will be an issue in the construction of concrete, which causes concrete deterioration if value of pH is below 6. The purpose of this study is to investigate corrosion caused by acid rainfall when used PCC cement mixed with RHA. RHA replacement level of 5%, by weight of cement was used in this study. The compressive strength design was 30 MPa. The simulated acid rain solution was prepared by mixing solution of H2SO4 and HNO3 to reach value pH of 4. The deterioration was measured by the number of corrosion product using SEM test. The results indicate a decrease in the number of component corrosion that occurs by using ASP.

Corrosion Inhibition of Bronze and Its Patina Exposed to Acid Rain

The aim of this study was to investigate the efficiency of 1-H benzimidazole as a corrosion inhibitor in protection of cultural artifacts made of bronze. For that purpose1-H benzimidazole was studied on bare and patinated Cu-6Sn bronze, exposed to urban environments. Dissolution of bare and patinated bronze was investigated by potentiodynamic techniques and electrochemical impedance spectroscopy. The microstructure of the bronze surface exposed to the inhibitor was examined by SEM/EDS. 1-H benzimidazole showed a very good protective effect in sulfate/carbonate media which simulate urban acid rainfall. Benzimidazole protected the Cu-6Sn bronze covered by electrochemical patina by stabilizing the patina layer and by slowing down dissolution of bronze substrate.

Likelihood and objective Bayesian modeling of acidity and major ions in rainfall using a bivariate pseudo-Gamma distribution

Modeling the acidity in rainfall at certain locations is a complex task because of different environmental conditions for different rainfall regimes and the large variability in the covariates involved. In this paper, concentration of acidity and major ions in the rainfall in UK is analyzed by assuming a bivariate pseudo-Gamma distribution. The model parameters are estimated by using the maximum likelihood method and the goodness of fit is checked. Furthermore, the non-informative Jeffreys prior for the distribution parameters is derived and a hybrid Gibbs sampling strategy is proposed to sample the corresponding posterior for conducting an objective Bayesian analysis. Finally, related quantities such as the deposition flux density are derived where the general pattern of the observed data appears to follow the fitted densities closely.

Experimental Study on Flexural Strength of Reinforced Concrete Beam Exposed to Acid Deposition in the Laboratory

In this study, the flexural behavior of the reinforced concrete beams attacked by acid rain environment is investigated. The objective is to discover the deterioration mechanism of the concrete beams servicing in the acid rain environment. An artificial rainfall device was designed. Eleven reinforced concrete beams, 120mm×200mm in cross-section were prepared in the laboratory. Three accelerating corrosion methods, which inclusive of immersion method, dry-wet cycle method, and artificial rainfall method, were applied to simulate the action of the real acid rain respectively. The acid solutions with pH level 1.5 and 2.5 were prepared by the mixture of sulfate and nitric acid solution respectively. One of the beams was tested in the natural condition to serve as reference; the remaining ten beams were tested after being exposed to the simulated acid environments for certain periods. Ultrasonic technology was applied to evaluate the damage depth and the compressive strength of the concrete. Dynamic test was applied to estimate the integrity of the beam. Three-point bending tests were performed to investigate the load carrying capacity of the beams. Mechanical properties of concrete and load carrying capacity of the beams exposed to different accelerated corrosion methods are obtained and compared. It is illustrated that the designed artificial device is efficient to simulate the real acid rainfall. It is shown that the strength of concrete, frequency and ultimate load of the beams, have a direct relationship to the damage degree of the beams.

Diagnóstico de Lluvia Ácida y Condiciones Meteorológicas Asociadas en el Barrio La Candelaria – Bogotá D.C.

El presente proyecto se desarrolló con el fin de establecer la realidad sobre la acidez de la lluvia en el barrio La Candelaria y para estudiar, además, la relación de este fenómeno con las condiciones atmosféricas predominantes en este sector de Bogotá. Al inicio del estudio fue necesario diseñar e instalar una red de estaciones de muestreo en sitios estratégicos de la localidad, seleccionados de acuerdo con criterios específicos. Para la toma y manejo de las muestras se siguieron protocolos, previamente elaborados, donde se determinaron los momentos de recolección de las muestras de lluvia (en la mañana y al finalizar la tarde) y la metodología para los análisis de laboratorio. En todos los casos el valor del pH de la muestra se tomó in-situ; los análisis de nitratos y sulfatos, en cambio, se realizaron en el laboratorio de Ingeniería Ambiental de la Universidad de la Salle. El proceso de recolección y análisis de muestras estuvo acompañado del monitoreo permanente de las condiciones atmosféricas reinantes en la localidad. Como resultado de la investigación se pudo establecer el nivel de acidez de la lluvia y su distribución espacio temporal en la localidad de La Candelaria. Se pudo determinar, además, la estrecha relación que existe entre las condiciones climatológicas y la acidez de la precipitación en esta franja de la ciudad.

High-resolution monitoring of nitrate variations in a typical subterranean karst stream, Chongqing, China

Globally, it is possible that up to 25% of the world’s population depends on karst water supplies. In karst areas, a high degree of groundwater and surface water linkage often results in the direct recharge of groundwater with polluted run-off following rainfall. In order to reveal the hydrochemical variations after rainfall, especially real-time variation of pollutants, high-resolution auto-monitoring techniques were used at the outlet of Qingmuguan subterranean stream (QSS), which is influenced by agricultural activities. In addition to rainfall, high-resolution measurements of pH, water level, electrical conductivity (Ec) and NO3 − concentration were recorded in the monsoon season and fertilizer application period using a data logger with time intervals of 15 min. In the six observed rainfall events, the pH value was mainly controlled by acidic rainfall inputs. The pH showed sharp decline after the rainfall event, and then increased. The Ec was impacted by the rainfall chemistry, dilution effect of rainfall and agricultural wastewater. NO3 − derived from agricultural activities was less impacted by rain chemistry; and its variations were mainly affected by the dilution effect of rainfall and agricultural wastewater. Under the influences of the R1 rainfall, the rapid changes of Ec and NO3 − were opposite in direction. As the rain continued, both the Ec and NO3 − rapidly changed in synchronization within the shortest period of 5 h and the longest of 27 h because of the impact of the agricultural wastewater. The groundwater quality changed due to the influx of agricultural wastewater over the entire monitoring period. According to the National Groundwater Quality Standard, People’s Republic of China (GB/T14848-9), the groundwater quality of the QSS moved through the following grades during the monitoring period: Grade III → Grade IV → Grade V → Grade IV → Grade V → Grade IV → Grade V → Grade IV → Grade III. Traditional sampling methods did not reveal accurate hydrochemistry changes of the QSS, and even generated misleading results. Consequently, the high-resolution auto-monitoring technique is necessary for the future protection and sustainable use of karst aquifer in Southwest China.

Assessment of granitic rocks degradability susceptive to acid solutions in urban area

Granitic rocks have been used in wide range of studies. When using these rocks, the most important aspect to be considered is their weathering potential, especially in acidic and wet environments. In these conditions, acid rainfall that is generated from atmospheric pollutions can accelerate the weathering trend of these rocks. The aim of this article is to assess the relationship between the weathering processes and environmental conditions. For this purpose, four types of Alvand granitic rocks were collected. Then, using optical microscopy and X-ray diffractometry the textural and mineral compositions of the rocks were studied. As the second step, the physical properties of these rocks were determined. To assess the effect of pH on the degradability of rocks, three solutions with different pH were prepared by adding sulfuric acid. Finally, slake durability test for each type in sulfuric acid with pH 2.5, 4, and 5.5 up to 15 cycles was performed. The results indicated that these rocks posses a very high durability and their use as building stones are recommended. In spite of these facts, long-term effects such as the weathering process can cause serious problems to ancient buildings as in the inscription of Darius.