Results 1 - 10 of 11
Results 1 - 10 of 11. Search took: 0.015 seconds
|Sort by: date | relevance|
[en] In large urban centers, the toxicity of metal mixtures may be enhanced by physicochemical factors and environmental variables, including pH. Rio Grande, a municipality located in the extreme south of Brazil, has soils with high levels of contamination due to urban and industrial activities and a high prevalence of acid rain events. Previous studies have shown that contact with elutriate of these soils can cause physiological and reproductive changes. Thus, the objective of the present study was to evaluate, through animal experimentation, the effects of a metal-contaminated soil, acidified by hydrofluoric acid at two different pH values (5.2 and 3.6), on the health of offspring of rats exposed during gestation and lactation. Female Wistar rats were gavaged daily for 42 days (gestation and breastfeeding) with soil elutriate contaminated with metals, using solvent with different pH values (6.0, 5.2, and 3.6). The following parameters were evaluated in their offspring: body and organ weight, length, appearance of developmental characteristics, and swimming. Experimental groups in which the progenitors were exposed to the solution at pH 3.6 exhibited a delayed increase in weight as well as motor deficit, with a decreased weight (onset) and length (beginning and end), while exposure in association with soil was an aggravating factor for the damages to the body. Exposure to the solution at pH 5.2 decreased the initial weight of the animals, impaired some parameters of weight development, and caused motor deficit on the 14th day. These novel findings reveal that the exposure of progenitors to environmental stressors can compromise the health of the offspring. Special attention should be given to populations living in areas with high prevalence of acid rain.
[en] In contrast to the term acid rain, alkaline precipitation or basic precipitation with pH value > 7 has been measured in many regions, and is considered to be an indicator of a regional atmospheric environment. Based on an observation network including 14 stations in northwestern China’s Gansu Province, the pH values in precipitation were measured during 2011–2015, and the spatial pattern and seasonal variation of precipitation acidity were investigated. In the Gansu Province, the precipitation is alkaline for most events, and precipitation with pH < 5.6 is very rare. The atmospheric environment of the study region is greatly influenced by the Asian dust sources in which the surface soil is alkaline, and the measured alkaline precipitation is related to the high dust loading. However, in some industrial cities like Jinchang and Lanzhou, the acidity in precipitation is usually stronger than the others. The seasonal variation of precipitation acidity is complex, which is jointly influenced by emission, transport and deposition. For extremely arid Northwest Gansu where deserts are located, the pH value is much high; for semi-arid and semi-humid East Gansu, the seasonal variation is not spatially coherent; for cold Southwest Gansu at high elevations, the precipitation acidity is relatively stable; for South Gansu in a humid climate, the large fluctuation is related to the complex moisture regimes of the monsoons.
[en] A pot experiment and a leaching experiment were conducted to investigate the effects of earthworms and pig manure on heavy metals (Cd, Pb, and Zn) immobility, in vitro bioaccessibility and leachability under simulated acid rain (SAR). Results showed manure significantly increased soil organic carbon (SOC), dissolved organic carbon (DOC), available phosphorus (AP), total N, total P and pH, and decreased CaCl2-extractable metals and total heavy metals in water and SAR leachate. The addition of earthworms significantly increased AP (from 0.38 to 1.7 mg kg−1), and a downward trend in CaCl2-extractable and total leaching loss of heavy metals were observed. The combined earthworm and manure treatment decreased CaCl2-extractable Zn, Cd, and Pb. For Na4P2O7-extractable metals, Cd and Pb were decreased with increasing manure application rate. Application of earthworm alone did not contribute to the remediation of heavy metal polluted soils. Considering the effects on heavy metal immobilization and cost, the application of 6% manure was an alternative approach for treating contaminated soils. These findings provide valuable information for risk management during immobilization of heavy metals in contaminated soils.
[en] A gas sensor is a device used to monitor and quantify the leakage or presence of harmful gases in the environment. The NO2 is mainly emitted from vehicle exhausts, industrial chimneys, and combustion of fossil fuels. It is among the harmful gases which are danger to human beings and is the cause of acid rain. Metal oxides (MOs) have been proven to be effective gas sensors, however, their high operating temperature hampers their practical use. Hence, MOs supported upon graphene-based materials tend to have low operating temperatures since graphene provides a large number of active sites for gas adsorption upon MO surface. It also facilitates charge transfer from MO surface to adsorbed gas molecules. On the other hand, graphene-based materials have high selectivity for NO2. Upon functionalization of graphene with –SO3H groups tend to reduce the response and recovery time of the sensor. Also sensing of NO2 by MO depends upon its p-type or n-type nature. The p-type MOs do not have a better response for NO2 than n-type sensors, however, upon compositing them with functionalized graphene, their response enhances and they show better selectivity towards NO2. Also, creating defects like oxygen vacancies tend to lower the operating temperature of MO-based gas sensors and makes them more selective towards NO2. In this minor review, MO-based sensors for room temperature sensing of NO2 have been discussed taking into account their response, recovery time, sensitivity and selectivity.
[en] Environmental regulations affect employment through productivity output and factor substitution. This paper employs a difference-in-differences (DID) method to investigate the effect of China’s Two Control Zones (TCZ) policy on the urban employment in 287 cities from 1994 to 2009. We apply the DID method to two time points: 1998 for policy issuance and 2000 for the policy implementation. From the results of analyses on full-sample cities, the TCZ policy did not contribute to increasing total urban employment. Moreover, a negative impact on employment resulted from sulfur dioxide and acid rain controls in secondary and tertiary industries, respectively. In the acid rain control zone, the TCZ policy increased the average wage of urban workers. Negative effects on employment were observed in larger cities. The policy triggered labor migration from larger to smaller cities, resulting in significant increases in primary and tertiary industry employment in smaller cities, although the effects on mid-size cities were insignificant. This study provides important empirical evidence and insight into the impact of the TCZ policy on urban employment.
[en] Acid rain alters nutrient cycling in tea plantations. However, the acquisition of Mg and Ca by plants and their nutrient interactions with Al, N, and P in response to acid rain are poorly understood. Experimental treatments simulating acid rain at various acidities (pH 4.5, 3.5, and 2.5) were performed within a red soil tea plantation in China. The available Mg, Al, Ca, N, and P were analyzed in the rhizosphere and bulk soils. Further, these elements were measured in absorptive, transportive, and storative roots in addition to twigs, tea, and mature leaves. Available soil Mg and Ca exhibited negative and positive rhizosphere effects, respectively, but the levels of both decreased due to acid rain treatment. In addition, average Mg and Ca concentrations generally decreased in plant tissues with increasing acidity. In contrast, average Al concentration increased across all plant tissues with increasing acidity treatment. Meanwhile, the ratios of Al/Mg and Al/Ca increased with increasing acidity but that of N/Al decreased in twigs and roots. Lastly, the ratios of N/Al, P/Ca, and N/P were all altered by acid treatment in tea and/or mature leaves. Taken together, these results indicated that elevated acidity increased the internal cycling of Al in plants but decreased Mg and Ca fluxes between soils and roots. Further, the response of interactions among the five measured elements to different acidities varied with tea plant tissue. Our findings may advance our understanding of plant adaptation to increasing soil acidification and atmospheric acid deposition around the world.
[en] Atmospheric precipitation is a very important link in the water cycle. The characteristics of major ions (n = 341) and stable isotopes (δ2H, δ18O; n = 157) were analysed in Hangzhou and Huzhou, which are economically prosperous cities in East China. The δ2H and δ18O values of precipitation ranged from − 109.70 to 21.30‰ and from − 14.87 to − 0.95‰, respectively. Compared with the local meteoric water line (LMWL) of China, the slope and intercept of the LMWL were much higher in Hangzhou and Huzhou, which is related to the effects of the humid climate and less secondary evaporation. The δ2H and δ18O values were highest in spring because of the influence of air masses from the northern Asian continent and other nearby sources. In contrast, the air masses from the South China Sea and the western Pacific Ocean in the summer had the lowest δ2H and δ18O. The dominant ions in precipitation indicate that Ca2+, HCO3−, SO42−, NH4+ and NO3− are the main ions of precipitation in Hangzhou and Huzhou, and the dilution of precipitation leads to lower concentrations of ions in spring and summer, similar to the values found in most Chinese cities. The increase in motor vehicle use resulted in a lower [SO42−]/[NO3−] ratio (1.64) of precipitation, indicating mixed acid rain in Hangzhou and Huzhou (HZS). Based on a combination of the correlation analysis, enrichment factors and source contributions, we determined that SO42− and NO3− were introduced mainly from anthropogenic activities such as coal combustion and vehicle exhaust, accounting for 89% and 99%, respectively. The strong correlation between Cl− and Na+, as well as Ca2+, Mg2+ and K+, indicates that these ions commonly have marine and crustal origins, respectively, and 40% of Mg2+ comes from a marine source.
[en] In this work, reuse probability of heavy metal-contaminated sediment for land application was discussed using a 100-day column leaching assessment under the situation of simulated acid rain. For comparison, NaCl-modified zeolite and biochar were firstly studied for their adsorption capacity for Cu, Cd, and Pb in aqueous solution, and then their stabilizing effects on the three metals in sediment-soil mixture. Characteristic results indicated that NaCl-modified zeolite had properties more conducive to metal adsorption than biochar, including higher BET surface area and more negative surface charges. Adsorption capacities of NaCl-modified zeolite fitted by Langmuir isotherm model were 24.83, 35.57, and 133.16 mg g−1 for Cu, Cd, and Pb, respectively. Leaching results demonstrated that metal concentrations in the leachates of soil receiving zeolite- or biochar-modified sediment reduced significantly after 100 days compared with that of soil receiving bare sediment. Moreover, the NaCl-modified zeolite presented a better performance in stabilizing the three metals than biochar from the BCR sequential extraction result. Therefore, stabilization of the dredged contaminated sediment by modified zeolite ensures an environmentally friendly reuse of the sediment on land and makes the sediment treatment operation-able and cost-effective.
[en] Shallow groundwater in the Nethen well field, NW Germany, is affected by acidification, accompanied by elevated ferrous iron and sulphate concentrations. The acidity results in the mobilization of aluminum to groundwater which is subsequently re-precipitated in deeper, less acidic layers. This, in turn, caused the clogging of a water well by aluminum hydroxide phosphate. Analyses of the regional geological framework and both groundwater and sediment samples revealed that acid sulphate soils, although not uncommon in the region, and acid rain are not the cause of the acidification. The unconfined aquifer contains pyrite, which is exposed to oxygen during the partial dewatering of the aquifer during pumping, especially in the cone of depression. Nitrate, stemming from agricultural activities, may contribute to the pyrite oxidation but dewatering is the main cause. Both the oxidation of pyrite and the subsequent acid release influence the mobilization of trace elements.
[en] Non-renewable energy sources have detrimental environmental effects, which directly and indirectly affect the biosphere as environmental deposits from their use for energy generation exceed a threshold. This study performs a streamlined life cycle assessment (LCA) of a coal-fired plant in South Africa. The cradle-to-grave LCA focuses on the coal cycle to determine hotspots with high environmental impacts in the process. Four impact categories were considered in this study: global warming potential, photochemical ozone creation potential, eutrophication potential, and acidification potential. Coal transportation, coal pulverization, water use, and ash management were identified as hotspots in the coal cycle. The coal process has 95% potential for global warming, 4% potential for eutrophication, 1% potential for acidification, and a negligible percentage for photochemical ozone creation. Susceptibility to climate change, eutrophication, acid rain, soil degradation, and water contamination among others are major concerns of the coal cycle. Outsourcing coal from nearby mines with train as medium of transportation reduces environmental impact. Similarly, the use of mitigation technologies like flue gas desulphurization, carbon capture storage, or selective catalytic reduction will reduce the concentration of the flue gas emitted. Ultimately, substituting the coal process with renewable energy sources will ensure environmental sustainability in South Africa. This study will serve as a good resource for further studies on LCA of coal power plants not only in other African countries but in other developing countries with similar situation.