Aquatic sediments accumulate heavy metals that are discharged into the environment. This study investigates possible water quality changes due to release of heavy metals such as Cd, Ni, Zn and Pb into the water column during dredging of anoxic sediments in the Old Harbour of Montreal. An environmental impact assessment of the sediment removal requires estimating the speciation of heavy metals in the water column with and without the solid phase. Chemical equilibria in the St. Lawrence River water are calculated using the program EQUILIB from the software FACT. Results show that the water is oversaturated with respect to CaMg(CO3)2 and Fe(OH)3. It is speculated that (ZnO)(Fe2O3) and (NiO)(Fe2O3) control the solubility of Zn and Ni in the water. The speciation of heavy metals in pore water of anoxic sediments is calculated, taking into account that the corresponding sulfides are solid phases and control their solubility. The impact of various scenarios on the area of concern is reviewed from an ecotoxicological perspective. Dredging might change the redox and acid-base conditions in the water column. Dredging can lead to an increase in the concentration of heavy metals in the water column and a change of metal speciation, but its impact will be less visible if the sediments contain high levels of calcium acting as a buffer.
Обобщены данные аналитического изучения цветного металла ямной культурно исторической области двух ареалов западного (Северное Причерноморье) и восточного (Южный Урал и Среднее Притоболье) методами спектрального, атомно эмиссионного, микрорентгеноспектрального, металлографического анализов. Приведенные материалы показали существование двух различных моделей металлопроизводства ямных племен, объясняющихся направленностью векторов историко металлургических контактов, наличием доступной рудной базы, сохранением традиционных технологий или же выработкой инновационных методов обработки мышьяковой бронзы. Черты определенного технологического сходства между уральской и причерноморской металлообработкой прослежены лишь на ранней стадии развития северопричерноморского центра металлопроизводства. Металлопроизводство ямных племен Северного Причерноморья в последующем демонстрирует иные технологические традиции получения орудий и украшений из низколегированной мышьяковой бронзы, поступающей из западных сырьевых источников. Уральские мастера использовали приемы литья крупных орудий из местной каргалинской окисленной меди в открытые и составные закрытые формы с высокотемпературными режимами термообработки. The paper summarizes data from the analytical studies of non ferrous metal in two areas of the Yamnaya (Pitgrave) culture, i. e. the western area (the North Pontic region) and the eastern area (the Southern Urals and the Middle Tobol basin). Methods of spectral, atomic emission, electron microprobe and metallographic analyses were employed. The materials described demonstrate existence of two different metal production models used by the Yamnaya population. The difference in the models is stipulated by different directions of historical and metallurgical contacts, availability of accessible ore deposits, maintenance of traditional technologies or development of innovation methods of arsenical bronze production. Certain technological similarities between the Urals and the North Pontic metalworking were identified only for the early development stage of the North Pontic center of metal production. In the subsequent period metal production of the Yamnaya population groups which lived in the North Pontic region demonstrates other technological traditions of producing tools and jewelry from low alloyed arsenical bronze that came from western raw material sources. The Urals craftsmen employed techniques of casting heavy tools from local Kargaly oxidized copper in open and composite closed moulds with high temperature modes of heat treatment.
Industrial channels were used extensively during the two previous centuries and have become heavily contaminated. This study investigates possible water quality changes in the Lachine Canal (Montreal) due to the release of heavy metals (Cd, Ni, Zn and Pb) into the water column during resuspension of anoxic sediments subjected to potential remediation. This release can be initiated by dredging activities for sediment removal. Equilibrium in the water from the Lachine Canal has been calculated using the program EQUILIB from the software FACT. The speciation of heavy metals in the water column was calculated with and without a solid phase before and after possible dredging. Speciation of heavy metals in pore water of anoxic sediments has been calculated, taking into account that corresponding sulfides are the solid phases controlling their solubility. The concentration of heavy metals under anoxic conditions considered could decrease by 8 orders of magnitude. The impact of various scenarios in the area of concern was reviewed from an ecotoxicological perspective. Dredging can possibly change the redox and acid–base conditions in the water column. The impact of dredging will be less if sediments contain calcium. Dredging can lead to an increase in the concentration of heavy metals in the water column and a change of metal speciation.
The study investigates the change in the water column quality in a situation where submarine communication cables cross the water bodies. In spite of precautions in technological achievements it is possible that these cables can be subjected to potential corrosion processes. This study was performed for a particular area of the St. Lawrence River. The impact of cables buried in sediments on lead speciation in the water column was shown under different conditions (anaerobic and aerobic, at different partial pressures of CO2, presence of organic acids). Equilibrium in the water was calculated taking into account gas, water and solid phases. Programs Equilibrium and EPH from FACT were utilized in this study to calculate Eh-pH diagrams and the equilibrium in water. The main form of lead was found to be PbOH+ (3.34×10-9 M/kg), the concentration of the free lead ion was two orders of magnitude lower (2.5×10-11 M/kg). The calculations, in which solid phases where considered, demonstrated that the water was oversaturated with respect to dolomite and iron(III) hydroxide. It was speculated that under these conditions dolomite could form a protective layer around the cable, which can delay the corrosion. Under anoxic conditions cerussite and lead sulfide precipitated. When PCO2 increased, the concentration of the free ion of lead increased.
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