Acid and aluminum effects on freshwater zooplankton: an in situ Mesocosm study

An in situ mesocosm experiment was performed to evaluate the role of aluminum toxicity in determining zooplankton community responses to take acidification. Large plastic enclosures were suspended in East Twin Lake, Ohio, USA, and duplicates were either untreated controls (pH 8.8), acidified to pH 4.5 over a 23 day period, or acidified and also spiked with incremental additions of Al, to produce a final inorganic monomeric Al level of 180 microg/liter at pH 4.5. Zooplankton abundance and species richness declined in both acid treatments, relative to the control, as numerous acid-sensitive species were eliminated. All of the acid-sensitive species were also Al-sensitive, declining in abundance more rapidly in the acid plus Al treatment than in the acid-alone treatment. Only two small cladocerans (Bosmina longirostris and Chydorus sphaericus) were acid tolerant. Both were also tolerant of elevated Al levels.     

Changes in trace metal concentrations in lake water and biota during experimental acidification of Little Rock Lake, Wisconsin, USA

Little Rock Lake, a small (18 ha), low-alkalinity (25 microeq litre(-1), pH 6.1) seepage lake in northern Wisconsin, was divided into two basins by a flexible, inert barrier and, beginning in spring 1985, the north basin was acidified in three 2-year steps to pH 5.6, 5.1 and 4.7. The annual average pH of the reference basin remained near 6.1. As part of a comprehensive programme to determine the chemical and biological responses to acidification, minor metals (Al, Fe, Mn) and trace metals (Cd, Cu, Pb, Zn) in lake water (0.4 microm pore filtered samples), periphyton, zooplankton, and yellow perch (Perca flavescens) were measured. At pH 5.6, dissolved Mn and Fe increased in the acidified basin. At pH 5.1 and 4.7, dissolved Al, Fe, Mn, Cd and Zn were elevated in the acidified basin. At pH 4.7, dissolved Pb in the acidified basin became elevated over reference basin levels. Dissolved Cu remained similar in both basins down to pH 4.7. Cd burdens in periphyton collected on artificial substrates were lower in the treatment basin at pH 5.1 (1.8 microg g(-1) dry wt.) than in the reference basin at pH 6.1 (7.5 microg g(-1) dry wt.), but Al and Fe burdens in periphyton were similar in both basins. Likewise, Cd levels in muscle tissue of perch from the treatment basin at pH 4.7 were lower (26 ng g(-1) dry wt.) than in the reference basin at pH 6.1 (36 ng g(-1) dry wt.); Al and Fe burdens were similar in perch muscle tissue from both basins. Levels of Cd and Fe in zooplankton from the acidified basin at pH 4.7 were approximately equal to 2x higher than in animals from the reference basin. In both basins of the lake, Al and Cd levels in lake biota decreased with increasing trophic level, demonstrating that food chain biomagnification does not occur for these metals.     

Effects of acidic solutions on element dynamics in the monsoon evergreen broad-leaved forest at Dinghushan,China

BACKGROUND: Soil metal dynamics are affected by acid deposition. Little knowledge is available about the process in the lateritic soils under the monsoon forest in south China. METHODS: Samplings of Acmera acuminatissima, Cryptocarya concinna and Schima superba were grown from October, 2000 to July, 2002 in pots with a natural acid lateritic forest soil from Dinghushan. Pots were watered weekly with an acid solution (pH 3.05, 3.52, 4.00 or 4.40) or with tap water. Fe, Mn, Cu and Al were measured in soils, leachates and sapling leaves. RESULTS: Soil extractable Fe and leachate Al and Mn concentrations increased with a decreasing treatment pH. Soil reactive Al exhibited the opposite trend and decreased over time. The Ca/Al and Mg/ (Al+Mn) ratios did not decrease in the leaves of Schima superba, but decreased with a decreasing treatment pH for Cryptocaria concinna. Both ratios only decreased in the pH 3.05 treatment for Acmena CONCLUSIONS: Cu will not be toxic for plants since soil extractable Cu was not high and Fe will not be toxic either given that its root uptake was inhibited by Mn. Acid rains will lead to increased Mn and Al mobility in soil. Cryptocaria concinna will be the most sensible species to these changes (nutrient deficiency and direct Mn toxicity), while Schima superba should retain a good growth.     

Acid and aluminum effects on the survival of littoral macro-invertebrates during acute bioassays

Six common macro-invertebrates were exposed to soft water at pH 4.5, with or without 200 microg liter(-1) Al added. Survivals were determined at 6, 12, 24 and 48 h and compared with neutral pH, Al-free controls. The order of acid-sensitivity among the test animals, from greatest to least (with mean 24/48 h survivals in the pH 4.5, low Al treatment in parentheses), was: Caenis sp. (2%) > Hyalella azteca (12%) > Enallagma sp. (20%) > Gyraulus sp. (55%) > Chironomidae (94%) > Hydracarina (99%). Aluminum significantly reduced the survivals of Gyraulus, Hyalella and Chironomidae. The latter group experienced no significant mortality at pH 4.5 except when Al was present. In contrast, the Hydracarina were unaffected by both acid and acid plus Al exposure, and the survivals of Enallagma and Caenis at low pH were enhanced by Al. These differential responses to the treatments indicate that both acid and Al stress may control the structure of the littoral macroinvertebrate community in acid lakes.     

Effects of experimental acidification on mobilisation of metals from sediments of limed and non-limed lakes

In order to study the influence of pH on the mobilisation of metals from lake sediments, intact sediment cores with overlying water were sampled from one lime treated lake and one acidified lake. The overlying water of two cores from each lake was successively acidified to pH 4.2 over a period of 3 months. In the acid treated samples from the limed lake, the initial concentrations of Al, Cd, Mn, Pb and Zn in the overlying water were generally lower and the final concentrations were higher than in the acid treated samples from the acidified lake. The labile inorganic fraction of Al (Al(i)) was increasingly dominating as pH decreased. Redox potential and pH in the sediment indicated that the upper two centimetres were involved in the exchange reactions. The experiment showed that mobilisation of metals from sediments can occur and the results indicated that mobilisation could contribute to increased concentrations of metals in lake water during reacidification of formerly lime treated lakes.     

Mortality, growth, swimming activity and gill morphology of brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar) exposed to low pH with and without aluminum

Measurements were made of mortality, growth, swimming activity, and gill morphology of young-of-the-year brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar), exposed for 30 days to pH 5.6 +/- 0.5 (mean +/- 1 standard deviation) with and without addition of 107 +/- 57 microg liter(-1) exchangeable (labile monomeric) aluminum. The experiment was conducted in artificial stream channels adjacent to a natural stream and subject to daily and seasonal changes in temperature, light, and chemical conditions. There were no differences in survival or growth for brook trout in any treatment; Atlantic salmon survival and growth were significantly decreased in the acid + Al treatment. Scanning electron microscopy showed no damage to gills of either species in the acid treatments, but the acid + Al treatment caused slight swelling of brook trout gills near the filament tips and significant swelling and fusion of secondary lamellae of Atlantic salmon gills. The acid treatment increased swimming activity in brook trout, but both the acid and acid + Al treatments reduced activity in Atlantic salmon.     

Reproductive status, blood chemistry, gill histology and growth of perch (Perca fluviatilis) in three acidic lakes

Perch (Perca fluviatilis L.) were sampled soon after spawning in three small acidic lakes (pH 4.3-6.1, Al(lab) 5-106 microg litre(-1), Ca2+ 0.01-0.08 mmol litre(-1)) and in one circumneutral lake (pH 5.9-6.4, Al(lab) 4-12 microg litre(-1), Ca2+ 0.06-0.07 mmol litre(-1)) in southern Finland. Due to the delayed spawning of perch in the acidic lakes, sampling in those lakes was performed later than in the reference lake. In spite of that, the gonadosomatic index (GSI) of males in all the acidic lakes was significantly greater than in the reference lake. Of the two lakes with similar low water pH, the effects on reproduction were more prominent in the lake with higher water Al content. The plasma Ca2+ concentrations of females in the acidic lakes were significantly smaller than in the females of the reference lake. The low female:male plasma Ca2+ ratio (1.0-1.32) depicted delay of spawning. Stress in perch in acidic water was also seen in elevated blood haematocrit values, especially in females. On the other hand, a low plasma Cl- level, a common response to acidic water in salmonids, was not detected in perch in the most acidic lakes. The amount of Al accumulated in the gill epithelium was highest in the most acidified lake with high Al concentration, but was also pronounced in a lake with low pH and low Al concentration.     

Effects of acidification on the availability of toxic metals and calcium to wild birds and mammals

The effects of acidification on wildlife inhabiting aquatic or semi-aquatic environments are reviewed, with particular reference to the possibility for increased dietary exposure to Hg, Cd, Pb and/or Al, and decreased availability of essential dietary minerals such as Ca. It is concluded that: (1) piscivores risk increased exposure to dietary methyl-Hg in acidified habitats, and Hg concentrations in prey may reach levels known to cause reproductive impairment in birds and mammals; (2) piscivores do not risk increased exposure to dietary Cd, Pb or Al because these metals are either not increased in fish due to acidification, or increase are trivial from a toxicological perspective; (3) insectivores and omnivores may, under certain conditions, experience increased exposure to toxic metals in some acidified environments. Exposure levels are likely to be sufficiently low, however, that significant risks to health or reproduction are unlikely. More importantly, these wildlife species may experience a drastic decrease in the availability of dietary Ca due to the pH-related extinction of high-Ca aquatic invertebrate taxa (molluscs, crustaceans). Decreased availability of dietary Ca is known to adversely affect egg laying and eggshell integrity in birds, and the growth of hatchling birds and neonatal mammals. Acidification-related changes in the dietary availability of other essential elements, such as Mg, Se and P, have not been established and require further investigation; (4) herbivores may risk increased exposure to Al and Pb, and perhaps Cd, in acidified environments because certain macrophytes can accumulate high concentrations of these metals under acidic conditions. The relative importance of pH in determining the metal concentrations of major browse species, and the toxicological consequences for herbivores wildlife, is not well established and requires further study. A decreased availability of dietary Ca is also likely for herbivores inhabiting acidified environments.     

Influence of pH and aluminum on developing brook trout in a low calcium water

Eyed embryos of brook trout (Salvelinus fontinalis) were exposed to nominal pHs of 4.5, 5.5 and 7.5 with and without aluminum (300 microg liter(-1)) in extremely soft water (hardness <9mg liter (-1)) at 12 degrees C. Embryo mortality exceeded 80% at pH 4.5, averaged 15 to 18% in the pH 5.5 treatments and was less than 2% in the pH 7.5 treatments. Aluminum significantly reduced embryo mortality (85.3% vs 99.5%) at pH 4.5 but did not affect mortality at pH 5.5 or pH 7.5. Percent hatch and poor hatch were pH dependent and were not significantly influenced by aluminum. Brook trout larvae cumulative mortalities were 100% within 30 days at pH 4.5, with or without aluminum; 69% after 60 days at pH 5.5; 100% in 15 days at pH 5.5 with aluminum and 20% after 60 days at pH 7.5 with or without aluminum. Fish that survived the pH 5.5 treatment showed decreased growth and behavioral impairments compared to the controls (pH 7.5 without aluminum).     

The ecology of acidification and recovery: changes in herbivore-algal food web linkages across a stream pH gradient

We examined the effects of acidification on herbivore-algal food web linkages in headwater streams. We determined the structure and abundance of consumer and benthic algal assemblages, and gauged herbivory, in 10 streams along a pH gradient (mean annual pH 4.6-6.4). Biofilm taxonomic composition changed with pH but total abundance did not vary systematically across the gradient. Mayflies and chironomids dominated under circumneutral conditions but declined with increasing acidity and their consumption of algae was strongly reduced. Contrary to expectations, several putative shredder species consumed algae, maintaining the herbivore-algal linkage where specialist grazers could not persist. These shifts in functioning could render the communities of acidified streams resistant to reinvasion when acidity ameliorates and water chemistry is restored to a pre-acidification condition. This hypothesis is discussed in the light of recent trends in the chemistry and biology of the UK Acid Waters Monitoring Network sites.     

Pilot-plant study of wastewater sludge decontamination using a ferrous sulfate bioleaching process.

The objective of this research was to investigate the performance of the ferrous sulfate bioleaching (FSBL) process in a pilot plant for decontamination and stabilization of wastewater sludge. Batch and continuous experiments, conducted with two 4-m3 bioreactors using indigenous iron-oxidizing bacteria (20% v/v of inoculum) with addition of 4.0 g ferrous sulfate heptahydrate per liter of sludge initially acidified to pH 4.0, were sufficient for effective heavy metal (cadmium, copper, manganese, zinc, and lead) removal yields. The average metal removal yields during the FSBL process were as follows: cadmium (69 to 75%), copper (68 to 70%), manganese (72 to 73%), zinc (65 to 66%), and lead (16%). The FSBL process was also found to be effective in removing both fecal and total coliforms (abatement > 5 to 6 log units). The nutrients content (nitrogen, phosphorus, and magnesium) were also preserved in decontaminated sludge.     

Simulated Effects of Acidic Solutions on Element Dynamics in Monsoon Evergreen Broad-leaved Forest at Dinghushan,China - Part 1: Dynamics of K,Na, Ca,Mg and P (7 pp)

Background, Aim and Scope Acid deposition has become a concern in south China in recent years. This phenomenon has increased to a dramatic extent with the large use of cars and coal- fueled power plants. As a consequence, soils are becoming acidified and their element dynamics will change. A decrease in the nutrient availability will lead to slower plant growth and maybe to a change in the forest type with current species being replaced by new ones with less nutrient requirements. Because of these reasons, it is important to understand how the dynamics of elements will change and what mechanism is part of the process. This knowledge is important for modeling the acidification process and either finding ways to counter it or to predict its consequences. The primary purpose of this study was to provide information about how the dynamics of K, Na, Ca, Mg and P are affected by acid deposition in a typical forest in southern China. Materials and Methods: Experimental soils and saplings were collected directly from the monsoon evergreen broad-leaved forest in Dinghushan. All saplings were transplanted individually into ceramic pots in August 2000 and placed in an open area near their origin site. Pot soils were treated weekly from October, 2000 to July, 2002 with an acidic solution at pH 3.05, pH 3.52, pH 4.00 or pH 4.40, or with tap water as a control. The concentrations of SO42-, NO3-, K+, Na+, Ca2+, Mg2+ and available P and the pH were measured in soil and leachate samples taken at different times. The sapling leaves were collected and their element concentrations were measured at the end of the experiment. Results: Concentrations of soil exchangeable Ca and Mg decreased quickly over time, although only Ca showed changes with the acidic solution treatment and soil exchangeable K was stable because of soil weathering. Leaching of K, Mg and Ca was dependent upon the treatment acidity. Soil available P decreased slowly without any correlation with the acidity of the treatment. All the NO3- added by the treatment was taken up by the plants, but the SO42- added accumulated in the soil. Discussion: Amongst the plant species, Schima superba was little affected by the treatment, the leaf P content was affected in Acmena acuminatissima plants and Cryptocarya concinna was the most susceptible species to soil acidification, with a marked decrease of the leaf K, Ca and Mg concentrations when the treatment acidity increased. Conclusions: Simulated acid deposition affected the dynamics of K, Ca and Mg in the monsoon evergreen broad-leaved forest. The dynamics of Ca in the soil and of K, Mg and Ca in the soil leachates were affected by the acidic solution treatment. If such a soil acidification occurs, Cryptocarya concinna will be amongst the first affected species, but Schima superba will be able to sustain a good growth and mineral nutrition. Recommendations and Perspectives: Acid deposition will lead to imbalance the nutrient elements in the evergreen broad-leaved forest because of accelerated leaching losses of soil exchangeable Ca and Mg. Measures should be developed to slow down soil acidification or nutrient decrease.     

超声辐射浸渍法制备Fe-Ni-Mn/Al_2O_3催化剂及性能研究

以Al2O3为载体,分别采用超声辐射浸渍法和普通浸渍方法制备Fe-Ni-Mn/Al2O3催化剂。采用BET、XRD和SEM对催化剂的理化性质和孔结构进行了分析,以模拟酸性绿B废水为研究对象考察催化剂的催化性能。实验结果表明,浸渍溶液pH值和焙烧温度显著影响催化剂的性能。与普通浸渍法相比,超声浸渍法制备的Fe-Ni-Mn/Al2O3催化剂对酸性绿B脱色反应表现出较高的催化活性。     

超声辐射浸渍法制备Fe-Ni-Mn/Al2O3催化剂及性能研究

以Al2O3为载体,分别采用超声辐射浸渍法和普通浸渍方法制备Fe-Ni-Mn/Al2O3催化剂。采用BET、XRD和SEM对催化剂的理化性质和孔结构进行了分析,以模拟酸性绿B废水为研究对象考察催化剂的催化性能。实验结果表明,浸渍溶液pH值和焙烧温度显著影响催化剂的性能。与普通浸渍法相比,超声浸渍法制备的Fe-Ni-Mn/Al2O3催化剂对酸性绿B脱色反应表现出较高的催化活性。     

Aluminum binding to ion exchange sites in acid-sensitive versus acid-tolerant cladocerans

Two acid-sensitive cladocerans, Daphnia galeata mendotae and D. retrocurva, and one acid-tolerant one, Bosmina longirostris, were exposed for 24 h to pH 5.0 and 200 microg liter(-1) total Al. The entire procedure was replicated on three dates in summer 1989. Mortality rates were determined, and the extent of Al binding to ion exchange sites determined using hematoxylin staining. Both daphnids consistently experienced near 100% mortalities, while mortalities for B. longirostris were always near zero. The daphnids showed marked Al binding at the maxillary glands, the site of ion exchange, while B. longirostris showed no noticeable Al binding.     

Response of phytoplankton communities to acidification and recovery in Killarney Park and the Experimental Lakes Area,Ontario

It has been widely speculated that controls of SO2 emissions would stimulate recovery of acidified freshwater lakes in Canada, the United States and Europe. Phytoplankton communities from 22 lakes near Killarney Park Ontario, covering a pH range from 4.5-7.7, were studied from 1998-2000 and compared to data from experimentally acidified (pH decreased 6.7 to 4.5) and recovered (pH increased to 6.0) Lake 302 South at the Experimental Lakes Area (ELA), northwestern Ontario to assess recovery from acidification. Based on historical data, pH levels have rebounded to above 6.0 in several lakes in the Killarney area that were previously acidified to pH 5.0-5.5. Phytoplankton biomass was not correlated to pH, but there was a highly significant relationship between species richness and pH. Recovery trajectories were observed in a subset of 6 lakes, combining species diversity data from the present study with historical data. Correspondence analysis indicated that several of the lakes that experienced increased pH have shifted towards phytoplankton assemblages typical of circumneutral environments.     

Artificial acidification of a non-acidic and an acidic headwater stream in Maine, USA

Two headwater streams with low DOC and different pHs (4.5-4.8 and 5-6.5) were acidified with H2SO4 to pH 4.1 and 4.5, respectively, for 24-h periods. Neutralization of the added acid occurred by protonation of ANC (HCO3-dominated in the higher pH stream), desorption of Ca (< 15 microeq litre(-1)) and Mg (<6 microeq litre(-1)), and desorption and dissolution of AL (<250 microg litre(-1)) from the stream bed. The concentrations of dissolved organic carbon (DOC) remained constant within the experimental reaches. The concentrations of Na, K an H4SiO4 also remained constant, indicating no detectable increase in the rate of chemical weathering in the stream bed. After acid addition was stopped, concentrations of Ca, Mg and Al decreased to below background, indicating reversible ion exchange as the principal mechanism for the mobility of Ca and Mg and to a lesser extent for Al. Repeated acidifications indicated that significant regeneration of cations on the exchange surfaces of the stream substrate occurs rapidly.     

Biochemical responses of the mycorrhizae in Pinus massoniana to combined effects of Al, Ca and low pH

Biochemical responses of Pinus massoniana, with and without the inoculation mycorrhizal fungus Pisolithus tinctorius at the root, to artificial acid rain (pH 2.0) and various Ca/Al ratios were investigated. Some enzymes associated with the nutritive metabolism, such as acid phosphatase, alkaline phosphatase, nitrate reductase, mannitol dehydrogenase and trehalase, in the roots, stems and leaves of plant were obviously inhibited by the artificial acid rain and Al. After treatment with pH 2.0 + Ca/Al (0/1 or 1/10) artificial acid rain, the protein content in the organs was decreased. However, the activities of superoxide dismutase (SOD) and peroxidase (POD) and glutathione (GSH) concentrations were induced. It demonstrated that acid rain and Al could induce oxygen radicals in plant. Compared with the treatments with lower pH or Al, respectively, the combination of lower pH and Al concentration was more toxic to P. massoniana. Al toxicity could be ameliorated by the addition of Ca and the amelioration was the most when the ratio was 1/1 among the various Ca/Al ratio. Infection with mycorrhizal fungus P. tinctorius at the root of P. massoniana increased the ability of the plant to resist the toxicity of artificial acid rain and Al stress.     

褐煤对废水中酸性红B的吸附去除

选用褐煤作为廉价吸附剂,脱除模拟废水中染料酸性红B。研究了褐煤对废水中酸性红B的吸附动力学、等温吸附模式,考察了pH、褐煤投加量以及离子强度(NaCl)对吸附效果的影响。结果表明,吸附动力学较好地符合准二级速率方程(R2=1.000),并且以化学吸附为主;吸附等温式满足Langmuir方程(R2=0.986),最大单分子层吸附量为42 mg/g;废水中染料的去除率随溶液pH的减小而明显增加,在pH=1时,去除效果最好,证实吸附过程存在静电吸引及化学键合;在一定条件下,溶液中酸性红B的去除率随褐煤投加量增加而增加;吸附效果随溶液中离子强度(NaCl)的增加而增强。说明褐煤可以作为一种廉价吸附材料,用于处理含染料废水。     

Deacidification effect of the litter layer on forest soil during snowmelt runoff--laboratory experiment and its basic formularization for simulation modeling

The forest soil ecosystem can buffer and neutralize acidic airborne pollutants to some extent, but extensive acidification degrades the soil ecosystem. Several investigations have shown that surface flows often show particularly low pH values in rivers and lakes during snowmelt and that this acidification phenomenon takes place in a short time frame. Acid water from snowmelt first makes contact with the litter layer in the soil ecosystem. Therefore, a laboratory experiment was performed to study the impact of forest litter on the chemical composition of the water solution. The experiment presented in this paper confirmed that deacidification with a little leachate of organic matter is caused by cation exchange not only in upper mineral soil but also in the litter layer and that leachate of labile Al is restrained in the presence of litter. An attempt was made to incorporate these factors into the biogeochemical module of the model (ILWAS) to accurately estimate damage by acidification.