Trends in pH, calcium, and sulfate of rivers in Atlantic Canada (original) (raw)
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Changes in Freshwater Acidification Trends in Canada's Atlantic Provinces: 1983–1997
Water Air and Soil Pollution, 2002
Sixty-three lakes were sampled semi-annually for acid precipitation – related variables in Canada's Atlantic Provinces,Nova Scotia and Newfoundland from 1983 to 1997. A further 31 sites were sampled beginning in 1989 in Nova Scotia. We analyzedthe water chemistry data for trends in pH, acid neutralization capacity, sulfate and base cations using the whole data set for the original 63 sites and the most recent eight years' data for all sites. We also analyzed acid deposition at two CAPMoN precipitation chemistry sites located at the two extremes of thesampling region for trends. We found that hydrogen deposition decreased by 20% in Newfoundland and 30% in Nova Scotia, and sulfate decreased by 36 and 34%, respectively. Sulfate and basecations in lake waters showed decreases as expected, though lakeacidity and acid neutralization capacity did not show improvements. The conflicting trends in chemical variables suggest that though anthropogenically-induced weathering is diminishing in this region, conditions have not returned to `natural' background conditions.
Episodic acidification of freshwater systems in Canada ? Physical and geochemical processes
Water, Air, & Soil Pollution, 1994
The occurrence of episodic acidification in Canadian streams, lake waters and shallow groundwaters has been reviewed, and the contolling mechanisms identified. 'Episodes', which are periods of depressed alkalinity during hydrological events, have been studied mainly in southeastern Canada, and occur at all sites where there is sufficient time resolution of the observations, viz. Ontario, Quebec and Nova Scotia. An 'alkaline episode', where acidity decreases during an event, has been reported from one lake in the Canadian Artic. There is a bias towards the examination of episodes stimulated by snowmelt or rain-on-snow, since rainfall-stimulated episodes are poorly documented. Pre-event, rather than event, water dominates runoff during episodes. For this reason, biogeochemical reactions and the hydrological flowpaths in operation through the vadose and saturated zones are the principal controls on the chemical characteristics of episodes. Most episodes are dominated by base cation 'dilution' in circumneutral systems, and 'increase in strong acid anions' (particularly sulphate) in acidic systems. Episodes dominated by nitrification or organic acids or stimulated by sea salt input are rare or have not been decumented. Direct input of event water may dominate only during particular circumstances at snowmelt. Then, direct chemical inputs from lake ice and lake snow cover may be of importance in some systems.
Regional precipitation and surface water chemistry trends in southeastern Canada (1983–1991)
Canadian Journal of Fisheries and Aquatic Sciences, 1995
We analyzed for trends of acidification related variables from 1983 to 1992 in precipitation concentrations and deposition at six sites and surface water concentrations at 111 sites located from central Ontario to eastern Newfoundland. Precipitation showed significantly decreasing H+ and [Formula: see text] concentrations and deposition in central and eastern Ontario and at one of two sites in Québec (deposition only). For Ontario surface water sites, only increasing or stable [Formula: see text] trends were observed, and these had both concomitant increasing and decreasing trends for pH and (or) acid-neutralizing capacity (ANC). Despite a considerable number of lakes showing decreasing [Formula: see text] trends in Québec, pH and ANC also decreased. Québec was also the only region showing extensive evidence of increasing [Formula: see text]. The opposite situation was observed in Atlantic Canada lakes where despite increasing [Formula: see text], the dominant trend observed for pH ...
Revue des sciences de l'eau, 1998
Cet article représente une évaluation de l'état actuel et des tendances observées dans les écosystèmes lacustres, ainsi que de leur état futur probable lorsque les réductions d'émissions requises dans le cadre de l'Entente Canada-États-Unis sur la qualité de l'air auront été effectives. Outre une synthèse des faits saillants de ce dossier pour l'ensemble du Canada, le présent article s'appuie aussi sur l'ensemble des données physico-chimiques récentes (8874 échantillons) observées sur 2779 lacs de l'est canadien, ainsi que celles recueillies (1012 échantillons) sur 252 lacs de l'ouest canadien depuis 1985. Des données biologiques (poissons, benthos, zooplancton et oiseaux aquatiques) ont également été inventoriées pour identifier…
Effects of acidification on aquatic biota in Atlantic Canada
Environmental Reviews, 2011
Acidification of surface waters is a high-profile environmental issue in Atlantic Canada. Despite a reduction of emissions of acid-precursors (particularly SO 2) by more than 50% in major regions in North America, there has not yet been a significant recovery of surface waters in the region, likely because of the impoverished acid-neutralizing capacity (ANC) of watersheds. Nevertheless, any detection of a biological recovery in the region requires knowledge of acidification threshold values for indicator species, so that they can be used in an appropriate bio-monitoring program. Our review of information on the effects of acidification on aquatic organisms in Atlantic Canada suggests that the greatest changes in phytoplankton occur over a pH range of 4.7 to 5.6, just beyond the interval (pH 5.5 to 6.5) where bicarbonate (HCO À 3), a key source of both ANC and inorganic carbon for photosynthesis, becomes rapidly depleted and then lost. Similarly, the pH threshold of 5.5 appears to be critical to sensitive macrophytes. The pH tolerance is highly variable among invertebrate taxa, but the median tolerable pH for most sensitive species is between 5.2 and 6.1. Sensitive fish species are affected at pH levels as high as 6.0-6.5, but tolerant ones may do well even at pH <5.0. Amphibian species are relatively tolerant, surviving even to pH 3.5 to 4.0. Aquatic birds breed in the region at pH values greater than 5.5. Résumé : L'acidification des eaux de surface constitue une préoccupation environnementale de premier ordre dans le Canada Atlantique. En dépit d'une réduction des émissions des précurseurs (surtout le SO 2) de plus de 50 % dans la plupart des régions de l'Amérique du Nord, on n'observe toujours pas de récupération significative des eaux de surface dans la région, vraisemblablement dû à un appauvrissement de la capacité à neutraliser les acides (CNA) des bassins versants. Tout de même, toute détection de recouvrement biologique dans la région nécessite une connaissance des valeurs d'acidification critiques chez des espèces indicatrices, de sorte qu'elles puissent être utilisées dans un programme approprié de suivi biologique. Cette revue de l'information sur les effets de l'acidification sur les organismes aquatiques du Canada Atlantique suggère que les plus grands changements du phytoplancton surviennent à un pH allant de 4,7 à 5,6, juste au-delà de l'intervalle de pH (5,5 à 6,5) où le bicarbonate (HCO À 3), une source clé d'ANC aussi bien que de carbone inorganique pour la photosynthèse, devient rapidement épuisé avant d'être perdu. De la même façon, le seuil de pH de 5,5 semble critique pour les macrophytes sensibles. La tolérance au pH varie fortement chez les taxons d'invertébrés, mais la médiane du pH tolérable pour les organismes les plus sensibles va de 5,2 à 6,1. Les espèces de poissons sensibles sont affectées à des pH aussi élevés que 6,0-6,5, mais celles qui sont tolérantes peuvent performer même à des pH < 5,0. Les espèces d'amphibiens sont relativement tolérantes, survivant même à des pH de 3,5 à 4,0. Les oiseaux aquatiques se reproduisent dans les régions où les valeurs de pH sont supérieures à 5,5.
Past and future changes to acidified eastern Canadian lakes: A geochemical modeling approach
Applied Geochemistry, 2007
As SO 2 emissions are being reduced in North America, it has become important to know how rapidly the surface water chemistry of aquatic systems will recover. The authors applied the model of acidification of groundwater in catchments (MAGIC) to 410 acid-sensitive lakes located in a 3000 km east-west gradient in eastern Canada. The goal was to estimate the water chemistry from pre-acidification times, under worst case conditions (mid 1970s) and what it should be in the year 2030 after proposed acid emission reduction levels agreed-to or planned by Canada and the United States are in place. In eastern Canada, large decreases in pH and ANC are shown between pre-acidification and 1975, the year of greatest historical deposition. Current-day conditions are much improved from 1975. Under the most likely future acid deposition reduction scenarios, an improvement of pH and ANC is shown in all the regions from current-day levels, but not to pre-acidification levels. Dissolved Ca levels were considerably higher at the height of acidification than under pristine conditions, but will return to pre-acidification levels at most of the sites by the year 2030. The results also show that under proposed control programs, a large number of sites in eastern Canada will not return to ANC values >40 leq L À1 , thought to be suitable for healthy aquatic communities. Crown
Acidification of Lower St. Lawrence Estuary Bottom Waters
Atmosphere-Ocean, 2011
Accumulation of metabolic CO 2 can acidify marine waters above and beyond the ongoing acidification of the ocean by anthropogenic CO 2 . The impact of respiration on carbonate chemistry and pH is most acute in hypoxic and anoxic basins, where metabolic CO 2 accumulates to high concentrations. The bottom waters of the Lower St. Lawrence Estuary (LSLE), where persistently severe hypoxia has developed over the last 80 years, is one such case. We have reconstructed the evolution of pH in the bottom waters from historical and recent data, and from first principles relating the stoichiometry of CO 2 produced to oxygen consumed during microbial degradation of organic matter. Based on the value of the atmospheric partial pressure of CO 2 that best reproduces the preformed dissolved inorganic carbon concentration in the bottom waters, we estimate the average ventilation age of the bottom waters to be 16 ± 3 years. The pH of the bottom waters has decreased by 0.2 to 0.3 over the last 75 years, which is four to six times greater than can be attributed to the uptake of anthropogenic CO 2 . The pH decrease is accompanied by a decline in the saturation state with respect to both calcite and aragonite. As of 2007, bottom waters in the LSLE are slightly supersaturated with respect to calcite (Ω c ≈ 1.06 ± 0.04) but are strongly undersaturated with respect to aragonite (Ω a ≈ 0.67 ± 0.03).
Limnology in northeastern Ontario: from acidification to multiple stressors
Canadian Journal of Fisheries and Aquatic Sciences
Thousands of lakes around Sudbury, in northeastern Ontario, Canada, were badly damaged by acid deposition and many were also metal-contaminated. Large reductions in atmospheric sulphur and metal emissions have led to widespread chemical improvements in these lakes, and recovery has been documented for various biota. These findings were very important in establishing the necessity and value of sulphur emission controls during the international debates about the effects of acid deposition and the need for cleaner air. Studies of northeastern Ontario lakes are continuing to advance our understanding of chemical and biological recovery processes; however, that knowledge is still incomplete. It has become apparent that the recovery of lakes from acidification is closely linked with the responses to, and interactions with, other large-scale environmental stressors like climate change and calcium declines. Developing a better understanding of lake recovery processes and their future outcomes within such a multiple stressor context will be difficult. It will demand the merging of various approaches, including monitoring, experimentation, paleolimnology, and modelling, and will require effective collaboration among different research and monitoring sites and various agencies and institutions engaged in environmental science.