# Spatial Variation of Water Chemistry in Aries River Catchment, Western Romania
## 3 Results  
### Water Quality Assessment  
The monitoring study was conducted in the rainy season (November 2018), which is more susceptible to indicate the actual values of the studied physico-chemical indicators, compared to the warm season, when due to the drought, the concentrations are higher. This season was not characterized by high precipitation amounts; therefore, the dissolution of the physico-chemical compounds and the low concentrations of the chemicals due to the washing by precipitations should be avoided. The total number of sampling sites was set to 30 points, randomly chosen, in order to analyze a number of 27 physico-chemical parameters. The obtained results, along with their statistical data, are presented in Tables 3 and 4. The pH of the water samples (7.2-8.7) was within the normal limits except for three sample points: A3 (9.0), A7 (2.8) and A13 (5.2), which were indicating a strong variation of the water character. The slightly alkaline pH values are explained by the dissolution of carbonate minerals [29], while the strong acid character can be attributed to the drainage of the acid mine wastewaters near two mining areas. Acid mine drainage is an important source of surface water pollution worldwide. [PERSON] et al. (2009) reported the effects of the mine drainage into a hydrographic river catchment, in an area characterized by the abundance of sulfide ores, in Portugal [45]. Generally, tailings coming from mineral extraction areas are considered major sources of heavy metals and other chemical compounds (cyanide, sulfuric acid, ammonium nitrate). These chemicals are used during the separation processes of sterile from the ore and excavating machines. However, the natural geological units could also be the source of high amounts of toxic metals (e.g., Cd from sphalerite, Zn from sphalerite and As from oxidation of sulfide minerals pyrite) [46]. The analyzed surface water samples showed a low spatial variation of heavy metals (such as Cd, Mn, Ni and As). However, important differences were observed in the cases of the Fe, Cr, Co, Zn, Sr, Ba, and Al variability. It was observed that the metal concentrations varied in different sampling locations (Figure 3). Samples A9-A13 were characterized by the highest concentrations of As, Fe, Mn and Pb, exceeding the thresholds up to four times. The waters were sampled next to the tailing impoundments and connected to Rosia Montana and Rosia Poieni mining areas, indicating a significant impact on the chemical composition of the Aries River catchment over time. In the proximity of ValeaSesii tailing impoundment, A12 has the highest As, Fe and Mn concentrations, exceeding the thresholds. All samples were contaminated with Pb, with values ranging between 0.041 and 0.227, except for A19, which has a significant concentration of Pb as well, but below the threshold. Cr, Co and Zn concentrations were below the limits established by the Romanian and European Regulations regarding the quality of water resources [34,35]. The highest Cr concentration was 0.087 mg/L (A14) nearby Baia de Aries (a former mine that stopped its activity in 2004). There are no available data of environmental quality remediation attempts in that area. The Cu and Zn concentrations have a low degree of variation: Cu was in the range of 0.088-0.108 mg/L, and Zn ranged between 0.010 and 0.240 mg/L. Pb (0.041-0.227 mg/L) was identified in samples connected to the tailing impoundments (A7, A9-A15). Ni, Co and Cd concentrations had a very low spatial variation, indicating no anthropogenic interference in the water chemistry main processes. Ni ranged from 0.038 to 0.081 mg/L, Co from 0.050 mg/L to 0.069 mg/L, with the highest value in A11, while Cd concentrations ranged between 0.020 mg/L and 0.031 mg/L (A17). In all studied samples, Ba and Al were within the normal limits, Ba ranged between 0.028 mg/L and 0.054 mg/L (A11) and Al between 0.033 mg/L and 0.230 mg/L (A20). Sr had the maximum value of 0.405 mg/L in A14, nearby Baia de Aries.