Electrode pH error,seasonal epilimnetic pCO2, and the recent acidification of the maine lakes

Based on laboratory experiments involving standard pH protocols, on statistical analysis of data from the Eastern Lake survey, and on independent field evidence (1985–86), recent (post 1975) electrometric pH measurements for Maine lakes are reevaluated for accuracy. A standard pH protocol used in Maine up until September 1985 can introduce bias of ca. ?0.3 to ?0.4 pH units for representative epilimnetic samples with low CO₂ concentrations (near atmospheric equilibrium). The bias arises out of the very long electrode equilibration times for such samples. A new protocol using these same Ross combination electrodes provides pH estimates accurate within 0.03 pH units for a wide range of northeastern environmental samples, and independent of sample DOC and conductance. The new pH measurements, when paired with the earliest colorimetric measurements from the same Maine lakes, indicate that epilimnetic pH's may have increased significantly (by 0.1 to 0.2 units) since the pioneering lake surveys of G. P. Cooper (1938–44). Earlier, often-cited, reports documenting historical pH reductions in Maine lakes are apparently vitiated by analytical error in many modern electrode pH measurements. The error also affects the calibration of paleo-ecological models of recent lake acidification in New England.     

The role of nitrogen in acidification of Tatra Mountains lakes

An overall level as well as seasonal changes of acidification of Tatra Mountains surface waters have been studied. Measurements carried out in the Tatra Mountains National Park were concentrated on two lakes: Dlugi Staw and Zielony Staw, situated in the crystalline, granitic part of the mountains. These lakes differ from each other in altitude (1784 m and 1632 m a.s.l. respectively) as well as in quantity and variety of flora and fauna living in and around them. The wet deposition of acidifying compounds of sulphur and nitrogen, and their seasonal variability in the area of the lakes were measured and compared with the critical loads of sulphur and nitrogen for these lakes and their catchments. Results showed that the critical loads of both sulphur and nitrogen in Dlugi Staw were exceeded all over the year and in Zielony Staw the acid deposition was roughly equal to critical load. A surprisingly high concentration of nitrogen compounds in acid deposition, well above the absorption ability of both the lakes and their catchments were ascertained. Nitrogen retention coefficients calculated for the lakes were as follows: Dlugi Staw — approximately 10%, Zielony Staw — approximately 50%. Seasonal variability in nitrate ions concentration in the lakes' waters reflected their prominent acidification caused by nitrogen compounds corresponding to stages 2 and 3 in the scale proposed recently by Stoddard (Stoddard, 1994).     

Natural acidification of lakes and rivers in Japan: The ecosystem of Lake Usoriko (ph 3.4–3.8)

Most of the acid lakes and rivers in Japan have been influenced by acid waters of volcanic origin. Acidophilic and acidotolerant organisms are observed in these natural acid lakes and rivers, each of which has its own ecosystem and history. Lake Usoriko (pH 3.4–3.8) is a lake which.has been acidified by strongly acid water containing sulfuric acid and hydrochloric acid. The ecosystem of Lake Usoriko consists of aquatic vascular plants, aquatic bryophytes (Drepanocladus fluitans, etc.), algae, fish (Tribolodon hakonensis), insects, Zooplankton, fungi and bacteria. The paleosediment distributed along Lake Usoriko's northern shore is partly silicified and it contains fossils of a moss (Drepanocladus fluitans) and diatoms such as Pinnularia braunii var. amphicephala which are also distributed in the present lake. ¹⁴C dating of the specimens in the paleosediment, shoots of D. fluitans and the wood and cones of Picea glehnii gave values in the range 11500–34000y B.P. This record shows how long Lake Usoriko has been an acid lake.     

A role for sediments in retarding the acidification of headwater lakes

Experiments conducted on selected minerals and headwater lake sediments showed that major acid neutralization reactions above pH 4.5 were reactions releasing Ca²⁺ and Mg²⁺ from the sediments. Analysis of the sediments and water from 97 headwater lakes in northern Ontario showed a predictable decrease in the exchangeable Ca⁺ Mg²⁺ of the sediments with decreasing lakewater pH. Estimates of the total potential buffering capacity for the sediments above PH 4.5 and for water in these headwater lakes were made, and it was found that, even when only the top 1 cm of sediment is considered, a substantial sediment buffering reserve is available.     

Precision of a fiel Method for determination of pH in dilute lakes

Replicate pH measurements in three dilute lakes made during extreme conditions indicate that pH can be measured in the field with a variance due to measurement error of 0.005 unit. Error of the field technique in measuring the pH of dilute solutions in the laboratory ranges from less than 0.01 unit in dilute strong-acid solutions to about 0.05 unit in air-saturated deionized water.     

Natural and anthropogenic components of soil acidification

The following 8 theses are theoretically founded and experimentally quantified. 1. Rocks contain only bases and no acid precursors. Therefore, with the exception of sulfide containing rocks, soils cannot acidify as a result of atmospheric rock weathering. 2. A consumption of protons in rocks and soils results in a decrease of their acid neutralizing capacity (ANC) and can result in the buildup of a base neutralizing capacity (BNC). Strong soil acidification leads to the formation of stronger acids from weaker acids in the solid phase; this may be connected with a decrease in the BNC. 3. Weak acids (carbonic acid) lead in geological times to the depletion of bases without a larger accumulation of labile cation acids. Strong acids (HNO₃, organic acids, H₂SO₄) can lead within a few decades to soil acidification, i.e. to leaching of nutrient cations and the accumulation of labile cation acids. 4. The acid input caused by the natural emission of SO₂ and NO_x can be buffered by silicate weathering even in soils low in silicates. 5. The cause of soil impoverishment and soil acidification is a decoupling of the ion cycle in the ecosystem. 6. Acid deposition in forest ecosystems which persists over decades leads to soil acidification. 7. Formation and deposition of strong acids with conservative anions (SO₄, NO₃) shifts soil chemistry into the Al or Al/Fe buffer range up to great soil depth. In such soils eluvial conditions prevail throughout the solum and even in upper part of the C horizon: in connection with the decomposition of clay minerals, Al and eventually Fe are being eluviated. The present soil classification does not include this soil forming process. 8. In the long run, soil acidification by acid deposition results in the retraction of the root system of acid tolerant tree species from the mineral soil, and in water acidification.     

Impact of acidification on the methylmercury cycle of remote seepage lakes

Concentrations of monomethylmercury [CH₃Hg] were measured in the water and seston of five nearly pristine Wisconsin lakes, which span a range of pH from about 4.6 to 7.2. Previous studies had established a clear inverse relationship between [CH₃Hg] in fish and the pH of lakes in this region. Here, we examined the pH dependency of [CH₃Hg] in lake water and explored the partitioning of CH₃Hg between water, seston, and fish as a function of pH. Results indicate that [CH₃Hg] in lake water tends to increase as pH decreases, but that seasonal and spatial variability of [CH₃Hg] in individual lakes confounds a simple analysis of the relationship. The partitioning of CH₃Hg was related only weakly, if at all, to pH. Average partitioning coefficients (log k_d=log (C_p/C_w)) were higher for yearling yellow perch (6.0 to 6.5) than for seston (5.5 to 6.0) but did not vary significantly between lakes. This suggests that acidification has a stronger effect on the supply of CH₃Hg to the ecosystem than on specific rates of uptake by the biota.     

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.     

Evaluating macroinvertebrate responses to recovery from acidification in small lakes in Ontario,Canada

The biomonitoring program of Environment Canada examines food chains in small Ontario lakes to interpret ecological responses of waterfowl and their foods to changing acid deposition. Macroinvertebrates and fish were sampled in three acid-sensitive regions: Muskoka (1991; N=20), Algoma (1992; N=20), and Sudbury (1994; N=22). Small lakes (<11 ha;=" important=" breeding=" habitat=" for=" waterfowl)=" were=" chosen=" to=" cover=" the=" range=" of=" ph=" in=" each=" region,=" and=" include=" those=" with=" and=" without=" fish.=" in=" all=" regions,=" macroinvertebrate=" taxonomic=" richness=" (particularly=" nekton=" and=" benthos)=" was=" greater=" in=" fishless=" lakes=" compared=" to=" lakes=" with=" fish.=" among=" fishless=" lakes,=" taxonomic=" richness=" (especially=" benthos)=" was=" positively=" correlated=" with=" ph,=" although=" regional=" differences=" were=" evident.=" previous=" studies=" near=" sudbury=" have=" shown=" that=" several=" benthic=" groups=" have=" distribution=" and=" abundance=" patterns=" with=" respect=" to=" ph=" (trichoptera,=" ephemeroptera,=" hirudinea,=" amphipoda,=" and=" gastropoda).=" those=" patterns=" continue=" near=" sudbury,=" and=" were=" also=" strongly=" apparent=" in=" algoma.=" in=" all=" regions,=" the=" number=" of=" acid-sensitive=" taxa=" per=" lake=" is=" related=" to=" ph,=" and=" should=" increase=" as=" lakes=" recover=" from=" acidification.=" however,=" predicting=" macroinvertebrate=" responses=" to=" recovery=" must=" consider=" concurrent=" effects=" of=" fish,=" as=" they=" are=" a=" dominant=" factor=" structuring=" these=">     

Episodic acidification during snowmelt of high elevation lakes in the Sierra Nevada mountains of California

Atmospheric loads to dilute lakes in the Sierra Nevada mountains of California are very low, and fall almost entirely as snow. When acidic anions preferentially elute from melting snow, these low loads may nontheless be enough to acidify low ANC lakes. Two of the ten lakes included in the Sierra Episodes Study are discussed here: High Lake, the only lake in the study to become acidic during snowmelt; and Treasure Lake, typical of the remainder of the lakes. All lakes exhibited increases in NO₃ ^? concentrations during early snowmelt; these were accompanied by increases in base cations, primarily Ca²⁺. In the first few days of snowmelt, NO₃ ^? concentrations at High Lake increased more rapidly than concentrations of base cations, resulting in ANC values below zero. Export of both NO₃ ^? and SO₄ ^2? from the watersheds exceeded the inputs from the snowpack, suggesting that other sources (e.g., watershed minerals, stored inputs from the previous summer, transformations of other inputs) of these anions are important.     

Composition of the benthos in relation to pH in the LaCloche lakes

In the LaCloche Mountains of Ontario, 11 lakes spanning the pH range 4.8 to 6.7 were sampled for benthic organisms. Sixty sediment cores were collected from each lake, organisms >0.5 mm were separated and 25 taxa were identified. The number of taxa present was correlated negatively with [H⁺]: Y=23.2?4.27 × 10⁵ ×, r²=0.61, p<0.005. The density of all organisms was not correlated with lake pH. Six taxa: gastropods, pelecypods, daphnids, ephemeropterans, amphipods and ceratopogonids, either were reduced in abundance or absent from the more acid lakes. Bosminids and acari were more abundant in lakes of pH 5.0 to 5.5. The densities of the remaining taxa, notably chironomids and oligochaetes, appeared to be independent of pH over the range 4.4 to 6.7. These results are discussed in relation to the hypotheses which have been advanced to explain the differences observed in benthos distribution between lakes in Europe and in North America.     

Relationship between fish populations and pH for lakes in Southermost Norway

Fish status in terms of ‘good, ‘sparse’, ‘lost’, ‘never had fish’, has previously been reported for several thousands of lakes in southermost Norway. In more than a thousand of these lakes pH and conductivity have also been measured. These data have been used to establish a relationship between pH and fish status (brown trout). It is estimated that a uniform pH increase of 0.2 units will result in status changes from category ‘lost’ to ‘sparse’ in 12% of the lakes (27% of the lakes which have lost the fish population). Altogether 21 % of the lakes are predicted to change to a better category. We have used a fixed pH shift in order to make the approach applicable. This is a rather drastic simplification since the lakes will respond very differently to a reduction in S deposition depending on the original acidity and a number of other factors. The limitations of the approach and an alternative method used by Chester (1982) are discussed in detail.     

Chrysophyte scales in lake sediments provide evidence of recent acidification in two Quebec (Canada) lakes

Several lake surveys have indicated that many lakes in Quebec are sensitive to acidification, but no historical data are available to provide conclusive evidence of lake acidification. Paleolimnological studies can provide such evidence. Chrysophycean algal microfossils were analyzed from the sediments of Lake Bonneville and Lake Truite Rouge in Quebec. The chrysophyte flora in the study lakes was stable until 40 yr ago, but since then the taxa characteristic of acidic or slightly acidic waters increased in abundance. The study provides evidence of recent lake acidification in Quebec.     

Trace element concentrations in fish from three Adirondack lakes with different pH values

Concentrations of 29 elements were detected in the axial muscle, and 44 elements were detected in the gut contents of white suckers (Catostomus commersoni) and yellow perch (Perca favescens) from three lakes located in the New York State Adirondack Preserve. The study lakes were acidic Darts Lake, variable pH Lake Rondaxe, and circumneutral Moss Lake. For the majority of the elements, there were no clear differences in the muscle concentrations among fish inhabiting the three types of lakes. Two notable exceptions were Hg and Pb. With some exceptions, the highest muscle tissue Pb concentrations were found in fish from the acidic lake. For both species, the Hg was higher in the muscle than in the gut regardless of lake acidity. Other elements potentially toxic to humans (As, Cd, Ga, Pb, Se, and TI) were not accumulated in the muscle relative to the gut.     

Patterns of plankton species,pH and associated water chemistry in Nova Scotia lakes

In order to assess the patterns of distribution of plankton species in relation to acidity, water chemistry, and physical characteristics, twenty lakes in Nova Scotia were selected for examination, with pH ranging from 3.5 to 7.6. Correlation and multiple regression analyses revealed associations between plankton and chemical variables. Patterns of plankton abundance and diversity were noted with respect to both pH and nutrient status, with occasionally conflicting effects of these two factors. Phytoplankton abundance was most closely associated with nutrient status, while zooplankton abundance was related to measures of primary production. pH tended to affect plankton diversity more than abundance or standing crop. Several lakes were outliers from overall patterns, with several possible explanations. Cluster and factor analyses were used to identify associations of plankton species, and to relate these associations to lake characteristics. Certain species were noted with relatively wide distribution, but which never occurred at low pH (<4.6). These were Chroococcus limneticus, Asterionella formosa, Cyclotella meneghiniana, Pinnularia braunii, and Surirella robusta for phytoplankton, and Polyphemus pediculus, Diaptomus oregonensis, and Tropocyclops prasinus for zooplankton.     

不同pH条件下腐植酸对土壤中砷形态转化的影响

为了探索在不同pH条件下腐植酸对土壤中砷形态转化及生物毒性的影响,应用油菜盆栽试验,检测砷加入土壤后15 d、45 d、90d土壤中AE-As(水溶态、可交换态和碳酸盐结合态)Fe,Mn-As(铁/锰氧化物结合态),O,S-As(有机物及硫化物结合态),Res-As(残渣态)的含量及油菜生物量.结果表明,外源水溶态砷加入土壤后均迅速向相对稳定的形态转化,15 d时A3H1(pH9.5,腐殖酸用量为0g/kg)和A3H4(pH9.5,腐殖酸用量20 g/kg)处理的AE-As含量分别为13.40 mg/kg、9.23 mg/kg,转化率分别为78.7％、82.51％;在90 d时,A3H4处理的AE-As、Fe,Mn-As含量分别为6.28 mg/kg、1.23 mg/kg,仅为处理A3H1处理的53.9％和10.7％,O,S-As、Res-As含量分别为20.24 mg/kg、41.21 mg/kg,是处理A3H1的165％和127％.说明腐植酸更有利于土壤中AE-As向其他相对稳定的形态转化,主要体现在O,S-As的增加,腐植酸对碱性土壤中砷向较稳定形态转化的促进作用更加显著,而且与腐植酸的施用量呈正相关.外源砷在碱性条件下对植物的毒害更大,腐植酸用量在10 g/kg土时就可以有效降低砷的毒害.     

Trace element accumulation in the tissues of fish from lakes with different pH values

Two species of fish, omnivorous Catostomus commersoni (white suckers) and carnivorous Perca flavescens (yellow perch) were collected from three natural lakes with different pH ranges (circumneutral, pH 6.5 to 6.8; variable, pH 5.8 to 6.7; and acidic, pH 4.9 to 5.4). The lakes are located in the North Branch of the Big Moose River drainage system in the New York State Adirondack Park Preserve. Concentrations of potentially toxic elements (Al, Cd, Cu, Ph, and Se) were measured by electrothermal atomic absorption spectrophotometry in water, sediment and fish (bone, gill, kidney, liver and muscle) from each lake. The results showed that concentrations of Pb and Cd were significantly higher (P < 0.05) in some of the tissues of the fish collected from the acidic lake. Also, the yellow perch from the acidic take had significantly higher (P<0.05) Se concentrations in their muscle and livers than fish from the other lakes. The concentrations of Al were elevated in the gill tissues of both fish species from the acidic lake relative to fish from the other lakes. Possible mechanisms contributing to these differences in tissue concentration are discussed.     

Diatom-based pH reconstruction studies of acid lakes in Europe and North America: A synthesis

The analysis of diatom assemblages in lake sediments is being increasingly used to reconstruct past trends in the pH of acid lakes. This paper briefly reviews the data that are now available for Europe and North America and concludes that the evidence is consistent with the acid deposition hypothesis for recent lake acidification.