*4.1.3 Trace elements concentrations*

Some of the trace elements (Cu & Zn) show wide variability in concentration varying from 13.4 mg/l, 0.003 to 0.088 mg/l respectively (**Table 2**). The spider graphs (**Figures 2** and **3**) of the Light Ion Lithophile Elements (LILE) (Ba, Rb, Sr) normalized to chondrite values show enrichment (1–10 X chondrite values) while Nd to Yb are impoverished (0.001 to <1 X chondrite). These elements display variations in concentration over the study period.

### *4.1.4 Rare earth elements concentrations*

The REE concentrations displayed in the spidergraph (**Figure 4**) show slight variability during the study period and are rarely depended on the seasons (**Table 3**). The concentration variations for La, Ca, Pr, Nd, and Sm is 0.01 to 0.5 ppb, 0.06 to 1.09 ppb, < 0.01 to 0.12 ppb, and < 0.02 to 0.08 ppb respectively. However, Gd-Lu concentration range between ≤0.01 and with few deviations >0.01 ppb which is not dependent on season. The sum average concentration for the REE (La to Lu) is 0.54 ppb and varies between <0.01 and 1.09 ppb. The REE are impoverished relative to chondrite values (< 1 X chondrite). There are significant variations (0.03 to 0.18 X chondrite) for La-Sm in the LREE concentration relative to HREE (Gd to Lu). An important characteristic of the variations is the relative similarities in the geochemical spectra indicating similar source.

### *4.1.5 Anion concentrations*

The major anions of the lake water are HCO3 − , Cl− , SO4, and NO3 with average concentration of 141.4 mg/l, 5.65 mg/l, 0.845 mg/l. The minor anions are F, Br and PO4 with average concentration of 0.24 mg/l, 0.017 mg/l, 0.03 mg/l respectively. Generally, the highest (193.675 mg/l) and the lowest (186.5 mg/l) sum of the major anions concentrations are observed during the dry and wet seasons respectively.

A comparative hydrochemical concentration of the anions of chloride (Cl− ) and sulphate (So4 −2) in the present study with Patterson [9] values (**Table 1**) showed Cl and SO4 have increased from 2.5 mg/l to 5.67 mg/l and < 0.33 mg/l to 1.03 mg/l respectively.

**Figure 2.**

*Spidergraph of incompatible trace element concentrations of Pidong crater Lake normalized to chondrite.*

#### **Figure 3.**

*Spidergraph of incompatible trace element concentrations of Pidong crater Lake normalized to upper crust abundance.*

#### **Figure 4.**

*Spidergraph of REE of Pidong crater Lake, Bwonpe volcanic spring, wells and river Bwonpe normalized to chondrite.*

#### **4.2 Oxygen, hydrogen and carbon isotopes**

The Pidong Crater Lake isotope composition of oxygen-18 and deuterium are −4.90/00 and − 250/00 respectively and that of the rainfall within the upper River Ndai basin are δ 18O (−4.750/00) and δ<sup>2</sup> H (−310/00) (**Table 4**). The plot of the δ 18O versus δ<sup>2</sup> H falls close to Standard Meteoric Water Line (**Figure 5**). The hydrocarbon age of the lake water is 230 ± 30Bp (**Figure 6**).

#### **4.3 Lake color change activities**

The Pidong Crater Lake intermittently display color changes from its natural bluish color to brown-yellowish color (**Figure 7**). The lake color change activities were observed in November 2014, October 2015 and September 2016. During


#### *Hydrogeochemistry of the Pidong Crater Lake, Jos Plateau Volcanic Province, Nigeria… DOI: http://dx.doi.org/10.5772/intechopen.99720*

