Concentration of mercury in water

INTRODUCTION

This survey reveals the properties of mercury, its effect an environment, main aspects of danger of the mercury-contaminated water, determination of an acceptable level of risk, description of the environmental behavior, fate and toxicity of mercury and their compounds.

Discovery of mercury

Quicksilver is one of the seven metals of antiquity. The ancient Greeks and Romans used mercury to clean gold. Many centuries alchemists believed that mercury is the main component of all metals, and if hardness is returned to the liquid mercury using sulfur or arsenic, it will transform into gold. IN 1735 Swedish chemist Georg Brandt has described isolation of mercury in its pure form to represent the element as the alchemists. However, mercury’s belonging to the metals has been proven by works of Lomonosov and Brown, who in 1759 were able to freeze mercury and research its metal properties

Use of mercury

it was often exploited in medicine, as a laxative, diuretic, antiseptic and dental amalgam for teeth. However, nowadays it is not used in medicine anymore, because of its high toxicity.

Now Mercury used in agriculture (seed protectants and herbicides), in the manufacture of scientific instruments mercury and in electrical appliances and in industrial instruments. In addition to this, it has been applied as a catalyst for the synthesis of acetic acid in metallurgy and for amalgamation of gold and silver in the manufacture of explosives. but now, the industrial usage of mercury is decreasing, because of environmental legislation in many countries.

Mercury concentration in environment

Mercury is rare element on the Earth with concentration 0,03 - 0,08 mg/kg in the soil, 0,00021 - 1,0 mg/kg in bedrock, 0,1 mg/l in ocean waters. The higher concentration of this metal can be found in sedimentary rocks and shale: 10 - 1000 µg/kg.

In natural environment, there are about 20 mercury minerals. The highest concentration of Hg is contained in cinnabar HgS. In rare cases, the subject of production of virgin mercury are metacinnabar and faded ore. Deposits are forming secondary mercury minerals in zones of oxidation of mercury.

Concentration of mercury in water

Concentration of mercury in aquatic and other systems depends on geological, geochemical, climatic, hydrological and human factors. The rising pollution of environment causes increasing level of mercury concentration in aquatic ecosystems. In mesopelagic chains the annual increase of mercury concentration is equal to 3,5 - 4,8%; in epipelagic chains – 1,1 - 1,9%.

Results of researches allow to consider that in non-polluted and fresh water concentration is 0,1 - 15 ng/l, for methylmercury 0,01 - 0,5 ng/l, and for polluted water systems with high level of the organic matters it is 25 ng/l.

2.4 Where can mercury be found?

Mercury is present in most of the sulphide minerals. There is its particularly high content set in faded ores.

Also, mercury minerals are found in the ore bodies of hydrothermal deposits, which were formed from hot water solutions saturated with gases coming from the depths of the Earth.. Cinnabar deposits and is currently situated in hot springs of North America and Kamchatka.

Mercury deposits are characterized by specific traits that distinguish them from other mineral deposits. These primarily include the distribution of mercury mineralization to brittle or porous species. However, as an exception, mercury mineralization occurs in clay and rocks. Recently, the field of this type have been found in the Caucasus.

Дата добавления: 2015-11-14