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Between the fall of 1977 and December 1980, over 800 samples of precipitation were collected at 9 rural locations across Nova Scotia. Average pH was 4.61, and an average conductivity of 25 µS cm -1 confirmed the low ionic strength of rain and snow. Of all ions, chloride was the most abundant at 76 µeq L -1 (2.7 mg L -1 ). Oceanic origins were perceived as the source for chloride as well as for Na, Mg, 51 % of K, 21% of Ca, and 21% of SO 4 , and the sea collectively accounted for 66% of all ions inNova Scotian precipitation. In contrast, the dominating ions in New York, New Hampshire, Ontario and Norway were H + and SO 4 . In Nova Scotia, chloride concentrations in rain (mg L -1 ) are a function of distance D (km) from the coast and may be described by the equation Cl [mg L -1 ] = 4.5D -0.42 . It indicates that Cl concentrations are reduced by about 50% within 0.5 km of the coast, and 80% within 5 km. The continental North American chloride data examined are also consistent with the relationship. The shape of the chloride curve is similar to curves others have developed from rain and lake water chemistry observations in Holland and the United Kingdom, although those, and other European data, indicate that the marine influence is less pronounced in northeastern North America. The marine influence of precipitation chemistry on Nova Scotia has a maximum seasonal amplitude during the winter. RÉSUMÉ On a collecté, de l'automne 1977 à décembre 1980, plus de 800 échantillons de précipitation à 9 sites ruraux de Nouvelle-Écosse. Un pH moyen de 4,61 et une conductibilité moyenne de 25 µS cm -1 indiquent la faible teneur ionique de la pluie et de la neige. De tous les ions, le chlorure est le plus répandu, 76 µeq L -1 (2,7 mg L -1 ). On a constaté que le chlorure ainsi que le Na, le Mg, 51 % du K, 21 % du Ca et 21 % du SO 4 provenaient de source océanique et que collectivement avec l'océan ils étaient responsables de 66 % de tous les ions dans les précipitations de la province. Par contre, dans les états de New York et du New Hampshire, ainsi qu'en Ontario et en Norvège, les ions dominants étaient H + et SO 4 . En Nouvelle-Écosse, les concentrations de chlorure dans la pluie (mg L -1 ) sont fonction de *This paper is based on a presentation made at the Canadian Hydrology la distance des côtes D (km) et peuvent être décrites par l'équation Cl = 4,5D -0.42 qui indique que les concentrations de Cl sont réduites d'environ 50 % à moins de 0,5 km des côtes et de 80 % à moins de 5 km. Les données sur le chlorure, à l'échelle du continent nord-américain, font état du même rapport. La courbe du chlorure est semblable aux courbes développées par autres pour la pluie et les observations de la chimie des eaux lacustres en Hollande et au Royaume-Uni, bien que celles-ci et d'autres données européennes montrent que l'influence océanique est moins prononcée sur le nord-est de l'Amérique du Nord L'influence océanique de la chimie des précipitations sur la Nouvelle-Ecosse a une amplitude maximale saisonnière durant l'hiver.

In February, 1975, a [Formula: see text] year study of five highland lakes (Big, Cheticamp, Gisborne, Long, and Surge Lakes) in the Wreck Cove area of Nova Scotia was initiated to determine the limnological effects of construction of a hydroelectric project. Almost 600 lake-water samples were used to monitor water-quality changes resulting from tunnelling, dam construction, reservoir clear-cutting, slashing, and burning, and establishment of access roads.The impact on Surge Lake was much more pronounced than on the other four lakes. Evidence strongly suggests that the significant water-quality changes in Surge Lake can be attributed to clear-cutting operations and construction activities (of longer duration and higher intensities in the vicinity of Surge Lake area in comparison with other areas) resulting in accelerated soil erosion, nitrification, and soil leaching. Also, the Surge Lake watershed had steeper slopes, and different vegetative cover.Nitrate, ammonia nitrogen, total and ortho phosphorus, calcium, magnesium, sodium, potassium, chloride sulfate, total solids, conductance, pH, suspended solids, and turbidity increased significantly in the lower-most lake (Surge) but only moderately in the remaining lakes. The relative rates and amounts of revegetation of exposed soils were also considered key factors in influencing the magnitude of changes in water quality of these highland (elevation 400 m) lakes.

Investigations with three laboratory-model aeratedlagoons proved that incompletely mixed (or aerobic-anaerobic) aerated lagoons can be rationally designed by using the Wehner-Wilhelm equatiodor Thirumurthi chart, which graphically depicts that equation for applications in biological wastewater treatment. Whereas the biological factors (such as temperature and wastewater quality) are delineated by a first-order biochemical oxygen demand (BOD) removal coefficient (K), the physical-hydraulic regimes (such as mixing pattern and depth-width ratio of lagoon) are represented by a dispersion index. The key to the design is the standard BOD removal coefficient (KJ, which is evaluated to be 0.29/day for municipal wastewaterat a standard temperature (7) of 20°C and organic load (L) of 20g. m-'. day-I. When the actual T and L of a lagoon, however, are other than the standard values, appropriate corrections should be assigned to K,to obtain K. Two equations for such corrections are provided.Two companion papers of previous studies demonstrated the successful application of the same method for designing waste stabilization ponds and completely mixed (aerobic) aerated lagoons; the present study accomplishes the same for incompletely mixed lagoons. An example design is included; the technique, however, needs to be verified by investigating the actual, field lagoons.Les etudes effectuees avec trois modeles en laboratoire de lagunes aerees ont prouve que ces dernieres, etant melangees incompletement (soit des lagunes aerobies-anaerobies) peuvent Ctre c o n p e s de f a~o n praticable en utilisant la formule Wehner-Wilhelm ou la carte Thirumurthi qui represente clairement cette formule applicable au traitement des eaux residuaires biologiques. Bien que les facteurs biologiques (tels que la temperature et la qualitedes eaux residuaires) soient decrits par le coefficient (K) d'elimination du premier ordre de DBO, les caracttristiques hydrauliques (telles que la f a~o n de melanger et le rapport profondeur-largeur de lagune) sont representees par l'indice de dispersion. La cle de la conception est le coefficient (KJ d'elimination de DBO standard qui est evalue a 0.29Ijour pour les eaux residuaires municipales a une temperature normale (7) de 20°C et une charge organique (L) de 20 g. m-'.jour-I. Toutefois, lorsque le T et le L actuels d'une lagune sont autres que les valeurs ordinaires, K,devrait Ctre corrige de f a~o n a obtenir K. Deux formules sont fournies pour de telles corrections.Alors que deux communications complementaires d'etudes prealables ont demontre une bonne application de la mCme methode pour le calcul d'etangs de stabilisation de residus et des lagunes aerees (aerobies) completement melangies, le mCme objectif est reussi dans I'etude actuelle des lagunes etant melangees incompletement. Un modkle exemplaire est inch. Toutefois, la technique doit h e confirmee en examinant les lagunes actuelles de chantiers.