Influence of acidification and aluminum on the density and biomass of lotic benthic invertebrates

Experiments were carried out in plasticized wooden channels fed by a small creek in the Reserve des Laurentides, 80 km north of Quebec city. Channels were naturally colonized by invertebrates for 65 d before treatment. Treated channels were acidified in August with dilute H₂SO₄ only, or with acid plus a solution of Al sulfate (final concentration of 0.19 mg L^?1). The control channel received creek water only (pH 6.3 to 6.9). The addition of Al had no effect on invertebrate density and biomass. After 73 d of acidification, invertebrate densities were only one third the number found in the control channel. Invertebrate hiomass was not different within channels, although biomass was generally higher in the two acidified channels. Difference in densities between acidified and non-acidified channels was attributed to lack of colonization and not to an increase in drift. Microtendipes, a large and resistant larva of Chironomidae constituted a large fraction of the hiomass, largely outweighing numerous very small larvae. Effects on the density were attributed to the direct effect of low pH and not to indirect action through food limitations.     

Chemical response of soil leachate to alternative approaches to experimental acidification

Abstract

One approach to evaluating computer models which predict terrestrial‐aquatic ecosystem response to acid deposition is the experimental acidification of soils with subsequent comparisons among predicted and measured soil solution response. Using a soil microcosm experimental approach, comparisions between simulated acid rain (i.e. dilute H₂SO₄), dry NH₄NO₃, and prilled reduced S were made for suitability for large‐scale field experiments. Soil microcosms consisting of reconstructed soil profiles received a background simulated throughfall dosing over the six month treatment period. Results indicated that simulated throughfall, applied at twice the ambient rate, acidified soil leachates approximately 0.5 pH units over the treatment period. Along with the decline in leachate pH was an apparent release of base cations as well as Fe and Al. Over the length of the treatment period, very little of the prilled S dissolved and the simulated acid rain treatment did not have significant effects on leachate chemistry.     

Biological,chemical and physical responses of lakes to experimental acidification

Changes in physical, chemical and biological factors were observed during a 5-yr experimental acidification study in Lake 223 of the Experimental Lakes Area, and compared to a 2 yr pre-acidification period. Significant changes included increased transparency, rates of hypolimnion heating and rates of thermocline deepening; increased concentrations of Mn, Na, Zn, Al, and chlorophyll; decreased concentrations of suspended C, total dissolved N, Fe and chloride; increases in Chlorophyta but decreases in Chrysophyta; the disappearance of the opossum shrimpMysis relicta and the fathead minnowPimephales promelas; the appearance of epidemics of the filamentous algaMougeotea; decreased fitness and decline in numbers ofOrconectes virilis; and increased embryonic mortality of the lake troutSalvelinus namaycush. Sulfur budgets for two lakes experimentally acidified with sulfuric acid reveal that an average of 1/4 to 1/3 of added sulfate is sedimented, presumably as FeS, reducing the efficiency of acidification. The sedimentation occurs under both oxic and anoxic conditions. The utility of whole-ecosystem mass balance studies of S in ‘experimental’ and ‘observational’ mass balance studies is discussed.     

Controlled experimental acidification of lake sediments and resulting trace metal behavior

Severe stream water acidification occurs at higher altitudes (> 600 m a.s.l.) in the Western Harz mountains in Northern Germany. Since 1986 an interdisciplinary research team has followed the fate of pollutants in the 50 km² catchment of an important drinking water reservoir (Lake Söse). An acidification experiment has estimated the role of the remobilization of selected elements from the lake sediments via acidification. Aquaria were used to monitor the effects of a stepwise acidification (from the natural pH of 6.5 to 5.0, 4.0 and 3.0) of the water column over a reconstituted sediment layer. The sediment chemistry has been analyzed before and after the acidification by XRF. The water chemistry was sampled at time intervals and analyzed by ICP-MS. With a pH drop from 6.5 to 3.0, many elements increase in concentration in the water of the acidified basins. Enrichment factors were: Al (5000), Ba (10), Cd (220), Co (800), Cu (170), Ni (90), Pb (5000), and Zn (400). This corresponds fairly well with the field data. Al, Cd, Fe, Mn, and Pb exceed German drinking water limits at pH 4.0. The combined high concentrations (μg L^?1) of Al (1000–2600), Cd (2–4), Cu (4–7), Pb (30–60), and Zn (100–300) in the water column of the acidified streams are not only toxic for fish but also for many other aquatic organisms. Chemical changes in the sediment are not significant within the experimental setup.     

Biotic community shifts explain the contrasting responses of microbial and root respiration to experimental soil acidification

Soil respiration is comprised primarily of root and microbial respiration, and accounts for nearly half of the total CO₂ efflux from terrestrial ecosystems. Soil acidification resulting from acid deposition significantly affects soil respiration. Yet, the mechanisms that underlie the effects of acidification on soil respiration and its two components remain unclear. We collected data on sources of soil CO₂ efflux (microbial and root respiration), above- and belowground biotic communities, and soil properties in a 4-year field experiment with seven levels of acid in a semi-arid Inner Mongolian grassland. Here, we show that soil acidification has contrasting effects on root and microbial respiration in a typical steppe grassland. Soil acidification increases root respiration mainly by an increase in root biomass and a shift to plant species with greater specific root respiration rates. The shift of plant community from perennial bunchgrasses to perennial rhizome grasses was in turn regulated by the decreases in soil base cations and N status. In contrast, soil acidification suppresses microbial respiration by reducing total microbial biomass and enzymatic activities, which appear to result from increases in soil H⁺ ions and decreases in soil base cations. Our results suggest that shifts in both plant and microbial communities dominate the responses of soil respiration and its components to soil acidification. These results also indicate that carbon cycling models concerned with future climate change should consider soil acidification as well as shifts in biotic communities.     

Effects of experimental acidification on macroinvertebrate drift diversity in a mountain stream

A small stream (Norris Brook) within the Hubbard Brook Experimental Forest was acidified to determine what effect elevated H⁺ stress may have on the ecology of a mountain stream. The experiment was designed to simulate a pH level (4.0) that can occur during initial snowmelt (acute period) and during longer term (chronic period) acidification. Daily macroinvertebrate drift samples were collected from treatment and reference areas of Norris Brook. Drift diversity at the generic level was calculated using Brillouin's formula and partitioned hierarchically following macroinvertebrate classifications based on taxonomy (orders) and feeding strategies (functional groups or guilds). The rate of movement of individuals and genera was significantly greater for those organisms leaving the acid-stressed area during the first five days than for those entering, whereas no difference between the rate of macroinvertebrates entering or leaving the acid-stressed area was apparent for either numbers or genera over the remaining 25-day study period. For the acute period (first five days), the increased macroinvertebrate drift leaving the acidified area was significantly more diverse at the levels of aquatic insect orders and functional groups but less diverse at the generic level than the drift entering. For the chronic period (25-day period) no significant differences were detected in either major taxa, functional group (with the exception of collectors), or generic diversity between the drift entering and leaving the treatment reach. Mayflies and probably chironomids leaving the acid-stressed area during the acute period were generically more diverse than those entering, whereas stoneflies drifting out of the acidified reach were generically less diverse than those drifting in. The overall change in the normal pattern of spatial and temporal variation in drift rate and diversity provides quantitative evidence that H⁺ stress significantly altered the structure and function of the macrobenthic community.     

Simulating acidification and recovery processes in experimental catchments with the ILWAS model

The Integrated Lake Watershed Acidification Study (ILWAS) model was used to simulate soil discharge chemistry at two neighboring experimental catchments. One catchment underwent deacidification because of the artificial application of deacidified precipitation whereas the other catchment received unaltered acidic precipitation. Simulated results reproduce the observed seasonal dynamics in the concentrations of base cations, NO ₃ ^? , Al, and H₄SiO ₄ ⁰ in soil discharges for both catchments. Simulated results also indicate that the export flux of base cations was decreased by 30% at the deacidification catchment in response to the decrease in acid deposition. However, simulated SO ₄ ^2? concentrations show decreases that are about 40% more rapid than were observed. Simulated organic acid concentrations were also substantially lower than those observed at the deacidification catchment, indicating that organic matter decomposition processes were not correctly simulated. Acid-base budgets for both 5 and 50-yr simulations indicate that acid displacement by base cations through ion exchange is the principal process delaying recovery of runoff alkalinity, whereas SO ₄ ^2? desorption has a minor role. Silicate weathering is the dominant acid-consuming process at both catchments. Criteria proposed here for assessing forecast reliability include reproducing seasonal dynamics in discharge chemistry, providing numerically accurate chemical concentrations when compared to monitoring data, and correctly predicting deacidification rate and extent. The ILWAS model generally meets these criteria, indicating that the model can produce a reliable forecast of the effects of acid deposition on the acid-base chemistry of surface waters given sufficient temporal data for confident optimization of the calibrated variables in the model.     

Mobility of heavy metals in pine forest soils as influenced by experimental acidification

The mobility of Pb, Zn, Cd and Cu was examined at two adjacent experimental plots at åmli, southern Norway, B-1 and B-2. Both experiments were established on the same glacifluvial deposits, with forest consisting of uniform stands of Pinus sylvestris L. The forest in B-1 was planted between 1968 and 1970, while B-2 consisted of naturally regenerated trees. The experiments included plots supplied with artificial rain of varying acidity over a period of seven and eight years for B-1 and B-2, respectively, in addition to control plots. In experiment B-1, experimental acidification was carried out both in unlimed plots and in plots applied with three different levels of lime. The two experiments showed distinct differences with respect to effects of the acidification on mobilization of heavy metals from the O horizon. In experiment B-1, the amount of Zn and Cd decreased with decreasing pH in artificial rain, while Pb and Cu were not appreciably affected. The reduction in Zn and Cd concentrations ceased after termination of the acidification experiment. Liming reduced the leachability of Zn, but still appreciable amounts of Zn were obviously leached from the O horizon during the experiment. In experiment B-2 a high retention even of Zn and Cd was observed in the O horizon, probably due to microbial uptake and accumulation.     

Leaching of metals from a spruce forest soil as influenced by experimental acidification

Acidified (H₂SO₄+HNO₃, 3:1) throughfall waters (pH 3.16 and 3.40 as volume weighted means or control (untreated throughfall water, pH 3.72) were applied for 3.5 yr by an automatic irrigation device to lysimeters containing podzolized spruce forest soils of 0–5, 0–15 and 0–35 cm soil depth. The total volume of the leachates was measured together with their pH and total content of DOC, Na, K, Ca, Mg, Fe, Mn, Al, Cu, Zn, Cd and Pb and the initial amounts of metals and H in the soil. The main part of H⁺ added with the throughfall waters was retained within the soil. Concentrations and fluxes of Mg, Ca, Mn, Zn and Cd in the soil were significantly increased by addition of acidified throughfall waters; K was less affected. As a consequence of lowered flux of DOC in the A horizon as acid input increased, Fe, Al, Cu, and Pb fluxes also decreased. The mobility of these metals in the A horizon was shown to be regulated mainly by the formation of watersoluble organic compounds rather than directly by pH variations. Compared to the control, the additional annual loss of Mg from the soil profile in the most acid treatment was c. 10% of the currently exchangeable amount.     

Trends of mercury and methylmercury in deposition,run-off water and sediments in relation to experimental manipulations and acidification

In the covered catchment at Lake Gårdsjön, the reversibility of acidification and the effects on Hg output of a decreased deposition of Hg and MeHg have been investigated since 1991. A first indication of a decreased from the covered catchment, caused by the artificial removal of Hg and MeHg input, has been observed. This has occurred in parallel with an overall decrease in Hg deposition fluxes in SW Sweden during 1990 to 1993. In the sediments of two acidified lakes, Lake Gårdsjön (limed) and Lake Härsevatten (acid), Hg concentrations decrease by 60% in the top cm, from the maximum around 1000 ng g^–1 at 5 cm depth indicating a decreasing deposition during the last 10 years. This decrease has occurred in parallel with decreasing atmospheric S-levels and is most likely caused by decreasing European Hg emissions. Decreasing trends of MeHg in run-off from two catchments has also been observed while the Hg output has remained somewhat more stable.     

Effects of experimental acidification and alkalinization on soil and growth and health of Acer saccharum Marsh.

Experimental application of eight acidifying, neutral, or alkalizer compounds (range: –16 to 16 kmol ha^–1 of acid‐neutralizing capacity [ANC]) was realized in two northern hardwood stands having significantly different soil base saturation (BS) (a “poor” and a “rich” site) to assess responses of soil physico‐chemical properties, and nutrition, growth, and health of sugar maple (Acer saccharum Marsh.) trees in the short (3 y) and longer term (10 y). The treatments influenced the main indicators of acidity in the forest floor (soil exchangeable‐Ca saturation [S_Ca], BS, exchangeable‐acidity saturation [S_H+Al], and the S_Ca/S_H+Al ratio) at both sites, their values increasing (decreasing for S_H+Al) along the ANC treatment gradient in both the short and longer term, except for pH. Base saturation of the upper 15 cm of the mineral B horizons of soils was influenced at the two sites 10 y after treatment application. Although ANC treatments affected nutrient concentrations of tree foliage in the short term, their effect was no longer detectable after 10 y at the two sites. Growth, however, was strongly related to ANC treatments after 10 y, but only at the poor site. From 1990 to 2000, the basal‐area growth rate of trees at the poor site was (mean ± SE) –0.62 ± 0.28 cm² y^–2 tree^–1 for the most negative ANC treatment to +0.90 ± 0.20 cm² y^–2 tree^–1 for the most positive ANC treatment. A climatic‐stress episode occurring in 1995/96 appeared to accentuate the growth decline of trees subjected to the most negative ANC treatment at the poor site. The experimental results support the hypothesis that atmospheric acid deposition load can cause forest soil base‐cation depletion, acidification, and predispose sugar maple to health and growth decline in the longer term in base‐cation‐poor soils, and that the phenomenon may be reversible by adding alkalizers.     

Zooplankton responses to acidification: A review of laboratory bioassays

This literature review summarizes laboratory bioassays of the effects of acidification on 32 zooplankton taxa. Low pH adversely affected survival, longevity, reproduction, Na flux, heart rate, growth rate, feeding or filtering rate, and respiration rate. The organisms most studied have been daphnids, specifically Daphnia magna and D. pulex. Recommendations for further research include analyses of sublethal effects on zooplankters other than daphnids, comparative studies of different taxa acclimated and tested under similar conditions, studies of the effects of acclimation conditions and genetic differences between zooplankton populations on acid sensitivity, and laboratory bioassays conducted under realistic conditions and supplemented with field data.     

Sulfur constituents of sediments and their relationship to lake acidification

Sulfate is a major component of acid precipitation in the Northeastern United States. Transformations and fluxes of S may be important indices of the effect of acidification on limnetic systems. Sulfur constiuents and respiration rates were compared in sediments among Oneida, Deer and South Lakes in New York which exhibit a range of buffering capacity and pH from high to low, respectively. Total S in Deer and South was higher near their major inlets. Sulfide was highest in Oneida sediment, which had a lower redox potential (Eh). Ester sulfate was a major portion of the S in the three lakes. Oxygen consumption was highest in Oneida and lowest in South sediments. The low ester sulfate and an elevated C/N ratio of South sediment may indicate that acidification inhibits decomposition     

Aluminium impact on respiration of lotic mayflies at low pH

Three species of stream-living mayfly nymphs were exposed to total inorganic (labile) monomeric aluminium levels of 0, 0.5, and 2.0 mg L^?1 at pH 4.0 and 4.8 for 10 days. Oxygen consumption rate of the nymphs was measured, using a closed-cylinder technique and micro-Winkler titration. The animals showed significant increases in respiration with raised Al concentrations. The mayfly species Ephemera danica, which is restricted to the less heavily acidified region of South Sweden, was most affected by Al. The response of the two Heptagenia species to elevated Al was less pronounced. The effect of pH, however, seemed less important. Two possible reasons for the respiration increase at high Al levels are: (1) A “chemical impact route”, consisting of a compensatory mechanism due to decreased O₂ transport efficiency, because of impaired osmoregulation and ion transport; and/or (2) a “mechanical impact route” with Al hydroxide precipitation and mucus formation on the gills, causing lowered respiration efficiency. This stress of the increased respiration rate costs energy. Thus less will be available for growth and reproduction. A model of the proposed impact routes is presented.     

附着生物对沉水植物伊乐藻生长的研究

以沉水植物伊乐藻（Elodea nuttalii（Plant.）ST.John.）为研究对象,室内利用原位湖水进行培养,通过测定伊乐藻的生物量、叶绿素质量分数、光合作用速率等指标,研究了附着生物量的增加对沉水植物伊乐藻的影响。结果表明,随着附着生物处理量的增加,伊乐藻的生物量、叶绿素质量分数以及光合作用速率随之下降,50d后,各处理的生物量与对照相比分别减少了约5%-15%,叶绿素质量分数以及光合作用速率下降了20%-43%、10%-36%。同时也分析了丝状藻对沉水植物伊乐藻的遮阴作用,初步推测附着生物对沉水植物伊乐藻的影响可能是由于附着生物的遮荫作用。研究的结果为揭示富营养化湖泊沉水植被衰退的机理提供了理论依据。     

Changes in aluminum pools of andisols due to soil acidification

Abstract

Aluminum concentrations in soil solutions are not only controlled by inorganic clay minerals but also by organically bound aluminum. The objective of this study was to determine which pools contribute to Al dissolution. Soil samples were taken at various distances from tree trunks and at various depths at the Rolling Land Laboratory (RLL), Hachioji, Tokyo. Selective dissolution techniques were used to analyze the changes in pools of solid-phase aluminum. Soil pH values around Hinoki cypresses were in the aluminum buffer range. Exchangeable aluminum contents in soils under Hinoki cypresses were 104 mmol_c kg-^?1 on the average. This value was similar to that of the cation exchange capacity (CEC) of Andisols at RLL at a soil pH of 4. The relationship between the soil pH and exchangeable, organically bound, and amorphous aluminum pools showed that dissolved aluminum ions in the soil solution were primarily derived from the amorphous Al pool. Dissolved aluminum ions were substituted with base cations of soils, resulting in the increase of the content of exchangeable Al and/or the formation of complexes with organic matter which increased the proportion of organically bound Al pools. Increase in the proportion of organically bound Al pools indicated the importance of complexation with soil organic matter for controlling the aluminum concentration in the soil solution.     

Linking laboratory and field responses of fish populations to acidification

To increase understanding of mechanisms by which fish populations respond to water chemistry changes resulting from acidification, it is necessary to link the results of laboratory studies of the effects of pH, Al, and Ca on the survival, growth, and reproduction of individual fish to responses of fish populations in the field. Our framework for achieving this goal is based on the types of data commonly available from both laboratory and field studies. One of the models (PHALCA) in this framework estimates the number of fish surviving as a function of time, given pH, Al, and Ca levels. A second model (FISHEGGS) evaluates the reduction in reproductive potential of a fish population attributable to the effects of pH, Al, and Ca on the survival of young-of-the-year and older fish and on fecundity. Preliminary results from these two models are presented, and the entire framework will be applied and tested over the next year using data for brook trout and lakes in the Adirondacks. The framework and models are a complementary alternative to the statistical analysis of survey data on water chemistry and on presence or absence of a fish species.     

基于固着藻类反应器的生态沟渠构建

为使池塘循环水养殖系统中人工湿地出水更加满足养殖水质要求,在长×宽×深为150 m×0.5 m×0.6 m的养殖池塘排水沟内借助固着藻类反应器原理设计构建了生态沟渠,研究了生态沟渠对人工湿地出水溶氧恢复状况及深度净化效果。研究结果显示,人工湿地出水溶氧经过生态沟渠后显著提高至4.41～7.91 mg/L,pH值显著提高（P﹤0.05）。在150?m长度范围内,生态沟渠水中溶氧量随着沟渠长度的增加呈线性增加的趋势（P﹤0.05）。生态沟渠对人工湿地出水中NH4+-N、IMn和PO43--P等具有进一步去除效果,去除率分别达19.46%、13.38%和31.09%,对总大肠菌群的去除率范围在12.5%～78.13%。上述结果表明基于固着藻类反应器的生态沟渠能使人工湿地出水溶氧低的状况得到改善,N、P等物质得到进一步去除,可以作为与人工湿地配套的水回用系统。     

Critical limits of acidification to invertebrates in different regions of Europe

The International Cooperative Programme on Assessment and Monitoring of Acidification of Rivers and Lakes (ICP-Water) started in 1987. The main aim of the programme is to establish degree and geographical extent of acidification of surface waters and evaluate dose/response relationships to aquatic biota attributable to acidic deposition. The sample frequency in each locality is from a few — to a large number every year. Samples of invertebrates are taken from 108 localities. One time samples as well as regularly seasonal samples over years exist in the database. The acidity score (Raddum index) is determined for the different sites and regions, and compared with the corresponding chemical data. The analysis show a strong relationship between water quality and fauna. Sensitive species/taxa are associated with high ANC and pH, while tolerant species/taxa are associated with low pH and ANC. The diversity of the fauna in less acidified areas varies from region to region depending on the native water quality and the adaptions of the fauna. In areas with strongly oligotrophic water, low in ionic strength, the sensitive fauna tolerate lower ANC and pH than in areas with originally high ionic strength and high pH. The critical load of ANC, 20 μeq/1, developed for the oligotrophic water in Norway, should therefore be increased in watersheds with high ionic strength. In Central Europe the data indicate a critical level of ANC ≈50 μeq/1.