Кадмій у водних екосистемах: вміст, форми знаходження та токсичність для риб

Abstract

В огляді проаналізовано вміст та форми знаходження кадмію в природних водах, особливості його накопичення та токсичності для риб. Відмічено, що метал може існувати у водних екосистемах у різних формах. Відзначено, що значною мірою впливає на токсичність забруднювача присутність у воді зважених та розчинених органічних речовин. Показано, що токсична дія сполук металу обумовлюється не тільки концентрацією та формами знаходження у водному середовищі, але й фізико-хімічними показниками води та фізіологічним станом організму риб, які суттєво впливають на біодоступність та швидкість акумуляції металу.

Metals are among the most hazardous pollutants of the aquatic environment, as their technogenic migration exceeds natural levels. The significant danger posed by these toxicants to aquatic ecosystems stems from the fact that, unlike other chemicals of anthropogenic origin, metals do not decompose in natural conditions. Instead, they only change their physicochemical form within the environment. This is particularly characteristic of aquatic environments, where metal ions accumulate through leaching from soil surfaces, entering water via wastewater and industrial waste. Metals, both essential (indispensable) and non-essential (toxic), become dangerous at elevated concentrations due to their ability to bioaccumulate, undergo biomagnification, and exhibit high biological activity in aquatic organisms. The accumulation of heavy metals in the bodies of aquatic animals can negatively affect protein, lipid, and carbohydrate metabolism, as well as enzyme function and membrane permeability. These disturbances can lead to weakened health, and problems with growth and development. Cadmium is a typical toxicant. It belongs to the group of transitional, diffuse elements and is found as isomorphic impurities in many minerals. The content of cadmium in the Earth's crust, soil, and natural waters ranges from 10^-5 to 10^-6%. Within the Earth's crust, cadmium is transported by groundwater along with other chalcophile elements. Its migration in the environment depends on the chemical form of its compounds and the pH of the environment. In alkaline soils, cadmium is less mobile than in acidic soils. This review analyzes the content and forms of cadmium in natural waters, as well as its accumulation and toxicity to fish. It is noted that cadmium can exist in aquatic ecosystems in various forms. Additionally, the toxicity of cadmium is significantly influenced by the presence of suspended particles and dissolved organic compounds in water. It has been shown that the toxic effects of metal compounds depend not only on their concentration and chemical form but also on the physicochemical parameters of water and the physiological state of the fish. These factors substantially affect the bioavailability and rate of metal accumulation.