3. Experimental

2.4. Reagents and standards

272 Water Quality

standard 2: 10 mg L−<sup>1</sup>

2.5. Parameters of performance

tion factors R > 0.999) for most elements.

conc.sample is the concentration (μg L−<sup>1</sup>

the signal intensities recorded for the sample and blank, respectively:

Ultrapure deionized water (18.2 MΩ cm−<sup>1</sup>

PerkinElmer (atomic spectroscopy standard), was used.

) from a Milli‐Q analytical reagent‐grade water

. To deter-

purification system (Millipore) and ultrapure HNO3 60% were used. All the plastic lab ware employed for sampling was either new or cleaned by soaking 24 h first in 10% HNO3 then in ultrapure water. A 10 mg L−<sup>1</sup> solution of Mg, Cd, Cu, In, Ba, Ce, Pb, and U (in 1% HNO3, PerkinElmer Atomic Spectroscopy Standard–Setup/Stab/Masscal Solution) was used as external standard. The calibration solutions for quantitative measurements were prepared from a multi‐element standard purchased from PerkinElmer (standard ICP‐MS containing 29 ele-

mine the rare metals in the water samples, a multi‐element standard (multi‐element calibration

A method for determining the concentrations of heavy metals in water by ICP‐MS was developed and validated. The performance parameters were within specifications of SR EN ISO 17294‐2: water quality—application of inductively coupled plasma mass spectrometry (ICP‐ MS). Limit of detection recorded by the validated method for the elements under study provides the minimum limit of quantification required for quantitative determinations of the concentrations of these elements in the investigated waters, very good linearity (with correla-

The minimum detection limit is the lowest concentration or quantity of analyte which can be measured with reasonable statistical certainty. To determine the limit of detection 3SD, a method developed by PerkinElmer (Estimating Instrument Detection Limits, Elan version 3.4., and Software Guide) was used. Ultrapure water of 18.2 MΩ cm−<sup>1</sup> was aspired, and signal intensities for blank were recorded. The limit of detection was calculated by Eq. (1) where SDblank is the standard deviation for the signal recorded on the blank for the element studied,

The limit of quantitation (LOQ) is the lowest concentration that can be quantitatively determined with an acceptable level of repeatability and accuracy. It is generally considered to be approximately ten times the minimum detection limit (LOD). The analytical quality control included daily analysis of standards and triplicate analysis of samples and blanks. The accuracy and precision of the analytical technique were evaluated by analyzing a certified standard reference material. Precision of the instrument was determined by introducing the same quantity of one sample ten times, and then, the relative standard deviation (RSD) was calculated. RSD values ranged from 0.4 to 6.4% confirming the high precision of the method. Accuracy expresses the correlation between the arithmetic mean of the measured values and

: Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Sc, Tb, Th, Tm, Y, Yb),

) of the analyte in the sample, and Isample and Iblank are

LOD ¼ 3 � SDblank � concsample=ðIsample−IblankÞ: (1)

ments, matrix: 5% HNO3, PerkinElmer Life and Analytical Sciences), of 10 mg L<sup>−</sup><sup>1</sup>

### 3.1. Element concentrations in surface waters

Quantitative determination of the elements content in studied surface waters showed an increase, from 2009 to 2011, of Al and Mn concentrations in three sampling areas (Area 2, Area 4, and Area 5); an increase of Zn and Pb to Area 7; of Fe, Ti, Zn, and Pb concentrations to Area 2; of Cu and Pb to the Area 5; and of Fe and Cu to Area 6 (Table 2). High values were also registered for Zn and As in all sampling areas, during 2011 campaign, but below the permissible minimum level [14]. Increased concentrations of Cu, Zn, As, and Pb were observed in samples of surface water collected in 2010 compared with those collected in 2009 and 2011. These concentrations can be correlated with the registered rainfalls that were much higher in 2010. Seasonal changes in the concentrations of the analytes of interest observed in surface waters result from the dilution effect that occurred during rainfall. The content of heavy metals from the sampled river waters reduces due to the mixing with large volumes of uncontaminated water draining from the slopes. When the river flow decreases, the reverse phenomenon occurs. The contaminant concentrations increase both due to the evaporation and of the bacterial activity of sulfides oxidation once with the increase of temperatures.


Table 2. Comparative situation of metal concentrations in water sampled during the monitoring campaign.

### 3.1.1. Metals in water: seasonal influence

Water quality is affected by the weather conditions. This was revealed by studying the seasonal influence on the content of metals in water samples taken from the same areas in different calendar periods. A variation of heavy metal concentrations was observed in samples of water, sediment, and soil, depending on the season and certain times of year.

Characterization in terms of Cr, Pb, and Cu concentrations in water samples taken from the accumulation of fresh water of Tarnita (Area 8), Somes Cald (Area 2), and Somes Rece (Area 6) in early 2010 showed that the highest concentrations of these elements (Area 7) were registered in June and the lowest in January. This could be explained by the fact that the pollution originates in the driving effect of heavy metals by precipitation water that "wash" the adjacent area before reaching the lake. In the summer months, it is normal that the effect is more pronounced than in the cold winter months when the ground is frozen and therefore less exposed to erosion. The occurrence in July of higher concentration levels for some metals (e.g., Co, Cu, As) could be explained by the elevated temperatures recorded in this month that led to partial oxidation and solubilization of the sulfides, including biotransformation processes. Moreover, the intense evaporation enabled the crystallization of minerals containing large amounts of constituents of the elements Co, Cu and As. These minerals may contain soluble salts, which dissolve when rainfall is recorded in higher amounts. Table 3 shows the minimum and maximum values of the concentrations of elements in waters depending on the areas and sampling periods.

surface water collected in 2010 compared with those collected in 2009 and 2011. These concentrations can be correlated with the registered rainfalls that were much higher in 2010. Seasonal changes in the concentrations of the analytes of interest observed in surface waters result from the dilution effect that occurred during rainfall. The content of heavy metals from the sampled river waters reduces due to the mixing with large volumes of uncontaminated water draining from the slopes. When the river flow decreases, the reverse phenomenon occurs. The contaminant concentrations increase both due to the evaporation and of the bacterial activity of

Sampling area/concentration (µg L−<sup>1</sup>

2009 2010 2011 2009 2010 2011 2009 2010 2011 2009 2010 2011

Area 7 Area 2 Area 5 Area 6

Al 2.74 4.47 18.16 4.84 5.86 15.58 9.81 9.88 17.86 3.98 8.16 12.89 Mn 0.24 8.39 5.68 0.72 1.58 12.41 1.31 2.036 4.41 1.23 4.29 6.81 Fe 6.36 28.15 24.20 7.48 24.43 62.86 51.22 45.99 31.12 29.70 35.75 39.28 Ni 0.38 0.33 0.49 0.38 0.76 0.70 0.50 0.29 0.58 0.56 0.29 0.61 Ti 13.24 12.54 15.63 14.56 17.29 28.94 15.61 11.89 11.09 30.02 16.97 10.15 V 0.12 0.12 0.07 0.05 0.01 0.24 0.072 0.10 0.096 0.17 0.06 0.09 Co 0.03 0.63 0.43 0.03 1.37 0.613 0.032 0.56 0.398 0.07 0.53 0.52 Cu 0.69 0.59 0.71 1.42 0.71 1.348 0.588 0.50 0.727 0.59 0.54 0.68 Zn 0.23 0.16 13.08 0.19 0.14 1.26 0.202 0.13 0.532 0.87 0.14 1.57 As 0.61 0.43 1.24 0.54 0.44 2.186 0.500 0.47 1.167 0.85 0.49 1.11 Pb 0.08 0.02 0.061 0.08 0.01 0.071 0.018 0.02 0.163 0.04 0.02 0.04

)

Water quality is affected by the weather conditions. This was revealed by studying the seasonal influence on the content of metals in water samples taken from the same areas in different calendar periods. A variation of heavy metal concentrations was observed in samples

Table 2. Comparative situation of metal concentrations in water sampled during the monitoring campaign.

Characterization in terms of Cr, Pb, and Cu concentrations in water samples taken from the accumulation of fresh water of Tarnita (Area 8), Somes Cald (Area 2), and Somes Rece (Area 6) in early 2010 showed that the highest concentrations of these elements (Area 7) were registered in June and the lowest in January. This could be explained by the fact that the pollution originates in the driving effect of heavy metals by precipitation water that "wash" the adjacent area before reaching the lake. In the summer months, it is normal that the effect is more pronounced than in the cold winter months when the ground is frozen and therefore less exposed to erosion. The occurrence in July of higher concentration levels for some metals (e.g., Co, Cu, As) could be explained by the elevated temperatures recorded in this month that

of water, sediment, and soil, depending on the season and certain times of year.

sulfides oxidation once with the increase of temperatures.

3.1.1. Metals in water: seasonal influence

Elements

274 Water Quality


Table 3. The registered minimum and maximum values of the metal concentrations in waters by sampling area.

Determination of rare earths from various types of environmental samples is particularly important because it can serve to establish a sample fingerprint, and thus, the results could be used in determining the origin of the concerned sample and to identify sources of pollution [15, 16]. Mass spectrometry with inductively coupled plasma offers the possibility to measure the rare earths with an excellent accuracy, which cannot be achieved by any another method [17, 18]. In this context, systematic observations correlated with the climatic conditions were performed in this work for a prolonged period. Thus, by comparing the data on a sampling site, in different periods, higher concentrations of La, Ce, and Pr were observed in September.

Analyzing data obtained in the 3 years of monitoring (2009, 2010, and 2011) for the same sampling month, a constancy of the rare metal concentrations was revealed, except for Sc, which recorded a significant decrease in 2009 (Table 4). Determination of trace amounts of rare earth elements dissolved in water was correlated with their concentration in the soil; concentrations of rare metals can originate from the soils adjacent to waters that once washed by rainfalls reach these waters. Quality of surface water and sediments, in terms of chemical species concentrations of the metals, was discussed based on the results obtained for the surface water and sediment analyzed samples taken from locations.


Table 4. Comparative situation of the rare metal concentrations during the monitoring campaign.
