Influence of Bacau City’s Antropic Activities on the Heavy Metals Concentration Measured on Bistrita and Siret River Sides

ALEXANDRA-DANA CHITIMUS, FLORIN-MARIAN NEDEFF*, ION SANDU, CRISTIAN RADU, EMILIAN MOSNEGUTU*, IOAN GABRIEL SANDU Vasile Alecsandri University of Bacau, Faculty of Engineering, 157 Calea Marasesti, 600115, Bacau, Romania Alexandru Ioan Cuza University of Iasi, Arheoinvest Interdisciplinary Platform, Scientific Investigation Laboratory, 11 Carol I Blvd., 700506, Iasi, Romania Romanian Inventors Forum, 3 Sf. Petru Movila St., Bloc L11, III/3, 700089, Iasi, Romania Romanian Waters National Administration of Siret Basin, 1 Cuza Voda Str., 600274, Bacau, Romania Gheorghe Asachi Technical University of Iasi, Materials Science and Engineering Faculty, 53A D. Mangeron Blvd., 700050, Iasi, Romania

Naturally, heavy metals are held in the soil in relatively low concentrations but may occur in high concentrations with toxic potential, as a result of anthropogenic and especially uncontrolled activities. In this alternative, of their excess, heavy metals can cause disturbances in soil, plants and water and subsequently in the upper links of the food chain [1][2][3][4][5][6][7][8][9][10][11].
Heavy metal soil pollution has a cumulative character, which means that the pollutants accumulate slowly, being the result of permanent and long-term exposure of the soil to the action of these pollutants, without decomposing and without being able to remove them, whence and their permanent character. Once polluted, soils can only regenerate very hard and thus reduce their fertility [2,5,8,.
Research aimed to determine the influence of industrial activities carried out in Bacau city on the contents of heavy metals on the banks of Bistrita and Siret River. This influence was determined by analyzing the concentrations of heavy metals Siret Riverin Bridge Holt area, Siret Rivercanal UHE and Siret River-downstream confluence Bistrita/Siret, in locations along the Bistrita and Siret River.

Experimental part
For the selection of sampling points we had in view the areas where pollution sources are located. For every sampling section, sediments must be samples from representative places, so that we could have exact knowledge of the pollution sources as well as of the hydrological and and geomorphologic characteristics of the area. The sampling points must represent areas in which the sediment layer is thick and its granulosity is lower than 63μm, consisting of clay and slime [2].
Sections targeted for the sample-taking programme are presented in Figure 1. Sediments were sampled Siret River -Bridge Holt area (S1), Siret Rivercanal UHE (S2) and Siret River-downstream confluence Bistrita/Siret (S3), in locations along the Bistrita and Siret River, and experiments were conducted so as to test four heavy metals, namely Cd, Ni, Cr and Hg [2].

Results and discussions
For the soil-water interface level of 0 cm the established maximum limit for cadmium in the soil is exceeded in sampling point Siret River -Bridge Holt with 236.25 %.
For the sampling point Siret River -Bridge Holt, the established maximum limit for cadmium in the soil is exceeded with 101.12 % for the soil-water interface level of 100 cm, and for the soil-water interface level of 50 cm the exceeding rate of the established maximum limit for cadmium in the soil is 171.25 %.
The established maximum level for cadmium (0.8 mg/kg d.m.), in the soil was not exceeded in sampling points Siret Rivercanal UHE and Siret River-downstream confluence Bistrita/Siret (the value obtained was between 0.279 ÷ 0.46 mg/kg d.m.).
The established maximum level for nickel (35 mg/kg d.m.), in the soil was not exceeded in sampling point Siret River -Bridge Holt (the maximal value obtained was for the minimum soil-water interface level of 0 cm -23.95 mg/kg d.m., fig. 4).
Nickel concentrations in the soil for sampling point Siret Rivercanal UHE exceeds established levels with 110.57 % for the soil-water interface level of 0 cm, and for the soil-water interface level of 50 cm the nickel concentration in the soil exceeded permitted limits with 107.22 %.
For a soil-water interface level of 100 cm the maximum established limit for nickel in the soil is exceeded with 107.57 %.
The established maximum level for nickel, in the soil is exceeded in sampling point Siret River-downstream confluence Bistrita/Siret for all three level so: -minimum level water-soil interface (0 cm) with 130.22 %; -medium level water-soil interface (50 cm) with 138.62 %; -maximum level water-soil interface (100 cm) with 137.22 %. The established maximum level for chromium (100 mg/kg d.m.), in the soil was not exceeded in sampling point Siret River -Bridge Holt (the maximal value obtained was for the minimum soil-water interface level of 0 cm -57.11 mg/kg d.m., fig. 5). The established maximum limit for chromium in the soil in the sampling point Siret Rivercanal UHE is exceeded with 154.2 % for the soil-water interface level of 0 cm.
For sampling point Siret Rivercanal UHE, the established maximum limit for chromium in exceeded with 133.4 % for the medium level soil-water interface and with 152.3 % for the maximal level soil-water interface.
The established maximum level for chromium, in the soil is exceeded in sampling point Siret River-downstream confluence Bistrita/Siret for all three level and the higher value was registerd for the minimum level soil-water interface (154.7 mg/kg d.m.): The established maximum level for mercury, in the soil is not exceeded in al three sampling points, so the value obtained was ( fig. 6

Conclusions
The exceeding of limits of heavy metals (cadmium, nickel, chromium and mercury) in the soil is the result of urban wastewater discharged in Bistrita river by means of water treatment stations, industrial platforms form Bacau city, the inappropriate storage of municipal waste.
The higher value of concentration of heavy metal in the soil, was registered for cadmium, for the sampling point Siret River -Bridge Holt, minimum level soil-water interface -1.89 mg/kg d.m.
The established maximum limit for cadmium, nickel, chromium and mercury in the soil is not exceeded in the sampling points: -Siret Rivercanal UHE and Siret River-downstream confluence Bistrita/Siret-for all three levels (for cadmium); -Siret River -Bridge Holt -for all three levels (for nickel and chromium); -the established maximum level for mercury, in the soil is not exceeded in al three sampling points.