The Dniester is the main water artery of the Republic of Moldova. The presence of copper and iron in the waters of the river researchers are noted constantly, therefore it becomes clear practical and scientific interest in the processes of mass transfer of metal species of the studied metals. The work was carried out in 2017-2021 on the segment of the lower Dniester, in the area of the influx of large tributes of Raut and Ichel. During the work, hydrological, mathematical and statistical aspects were taken into account. From the water samples, using the membrane filtering method were extracted the dissolved-colloid (DCF<0.45 μm) and particulate (PF > 0.45 μm) forms of metal species. The copper and iron content was determined by the atomic absorption method on the IL-551 spectrophotometer, also other important hydrochemical (pH, water temperature, oxidability, О2) and ecochemical (Eh, rH2) parameters were also defined in water samples. The nature of dissolved-colloidal forms of metal species changed depending on the object of the study, the Dniester control section. In Raut, you can assume dominance of mineral-organic forms of iron and copper. Ichel can be characterized by the predominance of organic forms of metal species. On the studied segment of the lower Dniester, with the help of indirect methods, has been revealed a change in the nature of the forms of metal species from mineral-organic forms in the upstream cross section of Dniester, to organic coexistent metal forms in the outlet of Dniester. In the outlet cross section of Dniester (Vadul-lui-Voda), according to our data, the chemical channel of self-purification of natural water was established with the participation of free The Dniester is the main water artery of the Republic of Moldova. The presence of copper and iron in the waters of the river researchers are noted constantly, therefore it becomes clear practical and scientific interest in the processes of mass transfer of metal species of the studied metals. The work was carried out in 2017-2021 on the segment of the lower Dniester, in the area of the influx of large tributes of Raut and Ichel. During the work, hydrological, mathematical and statistical aspects were taken into account. From the water samples, using the membrane filtering method were extracted the dissolved-colloid (DCF<0.45 μm) and particulate (PF > 0.45 μm) forms of metal species. The copper and iron content was determined by the atomic absorption method on the IL-551 spectrophotometer, also other important hydrochemical (pH, water temperature, oxidability, О2) and ecochemical (Eh, rH2) parameters were also defined in water samples. The nature of dissolved-colloidal forms of metal species changed depending on the object of the study, the Dniester control section. In Raut, you can assume dominance of mineral-organic forms of iron and copper. Ichel can be characterized by the predominance of organic forms of metal species. On the studied segment of the lower Dniester, with the help of indirect methods, has been revealed a change in the nature of the forms of metal species from mineral-organic forms in the upstream cross section of Dniester, to organic coexistent metal forms in the outlet of Dniester. In the outlet cross section of Dniester (Vadul-lui-Voda), according to our data, the chemical channel of self-purification of natural water was established with the participation of free