**1.2 In situ physico-chemical measurements, water sampling, and analysis**

In situ water measurements were done at each site. At each constructed wetland, the Physico-chemical measurements were done in a sequence of inflow, midflow, and outflow, and at each site, a total of three samples were collected, which amounts to the number of water samples 15, when collected from all the five sites. The parameters measured include pH, Conductivity, Dissolved Oxygen, and Redox Potential. Water measurements were done using ThermoScientific Orion Star A329 portable pH/ISE/

*The Evaluation of the Macrophyte Species in the Accumulation of Selected Elements… DOI: http://dx.doi.org/10.5772/intechopen.105708*


**Table 3.**

*Summary of descriptive statistics of summer* in situ *water measurements.*

Conductivity/RDO/DO Meter. The grab method was used to collect water from the study sites. Water samples collected in 500 ml water bottles were kept in a fridge onsite at a temperature of 5°C. Later in the lab, the water inside the bottles was filtered using 0.45 μm Millipore. The water samples were analyzed directly using ICP-OES after filtration. The concentration levels of these elements in water were compared to the international standards for drinking water and presented in **Table 3**.

#### **1.3 Sediment sampling, preparation, and analysis**

Sediment cores were extracted from the selected five sites mentioned above. PVC (Polyvinylchloride) pipe was inserted into the ground using a hammer and a plank. The sediment cores were pulled out using a long steel bar inserted into two holes made on the top sides of the pipe. The pulled-out cores were wrapped in refuse bags to prevent the sediments from falling out of the pipes. The pipes were taken to the laboratory and stored in the cold storage room at a temperature of 5°C before preparation and analysis. The pipe cores with sediment were cut vertically into two halves. Sediments inside the pipe were separated into three distinctive parts of 0–2, 2–10, and 10–30 cm, respectively using a plastic ruler.

A subsample of 20 g was extracted and preserved inside a plastic bag and freezedried for 3 days. The freeze-dried samples were milled using a mortar and pestle. The samples were further prepared and put inside the Spectroscout Geo + XRF Fluorescence small containers with a thin film inserted in the middle of the containers. The thin film served as the base of the container, and it was also polished before it was put into the Spectroscout Geo + XRF Analyzer Pro for analysis. The sediments were analyzed for the presence and concentration of Fe, S, Mg, Cr, Mn, Co, Ni, Cu, Zn, Mo, and Pb using the X-Ray Fluorescence.

#### **1.4 Plants sampling, preparation, and analysis**

Samples of Typha capensis, Schoenoplectus corymbosus, and Phragmites australis species were collected from the five sampling sites. In each sampled site, the plants' species were also sampled by using the sequence of inflow of the site, on the midflow, and also on the outflow of the constructed wetlands. Three samples of each of the plants were collected per site, and a total number of 45 samples were collected from all five sites in one season. The macrophyte species were uprooted using a spade. The plants were taken out of the sites and washed with local and rinsed with distilled water, for quantitative removal of soil and other foreign particles.


#### *Vegetation Dynamics, Changing Ecosystems and Human Responsibility*


*The Evaluation of the Macrophyte Species in the Accumulation of Selected Elements … DOI: http://dx.doi.org/10.5772/intechopen.105708*

> **Table 4.**

*Translocation and bioconcentration factors for autumn and summer seasons.*

The plants were taken to the laboratory where they were thoroughly washed and rinsed with tap and distilled water. They were then separated into leaves, rhizomes, and roots. The stems were not included in the study. The plant leaves, roots, and rhizomes were also chopped into pieces of +/ two cm and homogenized and a subsample of +/ 20 g was extracted from all the samples and freeze-dried for two three days to ensure that the plants are much dry for easy grinding. The homogenized plants'samples were milled using a Fritsch Pulverisette 6 Mill into pulverized powder before metals analysis.

#### **1.5 Statistical analysis**

Statistical analysis was done using the Statistica Analysis Package Version 10 computer package. Differences amongst the means were determined by analysis of variance. The Pearson correlation coefficients (r) were used to express the associations of quantitative variables. The basic descriptive statistics were performed to determine the Mean, P-value, Median, Minimum, Maximum, and standard deviation to indicate the relationship between the levels at which the elements were absorbed by the water and sediments as well as the level at which they were carried by the water and the relationship was again determined at p ≤ 0.05. The sample size (n = 15) makes statistical comparisons easier as it is not limited by the sample size.

## **2. Results**

#### **2.1 Zinc (Zn)**

The results for the Physico-chemical parameters are presented in **Table 4**. The average concentration for Zn accumulated by the plants in the autumn and summer seasons were in a range of 124.83 and 230.47 μg/g respectively, as shown in **Figure 6**. The result of the higher accumulation of Zn in summer could be that the new shoots

*The Evaluation of the Macrophyte Species in the Accumulation of Selected Elements… DOI: http://dx.doi.org/10.5772/intechopen.105708*

are sprouting and as a result, more Zn is taken up by the plants as compared to autumn when the plants shed their leaves.

#### **2.2 Nickel (Ni)**

When plant samples were analyzed for Ni content, the higher average concentration for Ni was measured in summer. The average concentration of Ni accumulated by the plants during the autumn and summer seasons were 36.36 and 49.55 μg/g, respectively as shown in **Figure 7**. Ni accumulation in the plants in the two seasons follows that of Zn.

#### **2.3 Iron (Fe)**

During the investigation period, it was observed that Fe was accumulated by the plants as FeO. A higher amount of Fe in the plants was accumulated in the summer season. The average concentration for Fe accumulated by the plants during the summer and autumn seasons was 25657.92 and 24807.34 μg/g, as shown in **Figure 8**. Unlike Zn, Fe accumulation in the two seasons did not differ much.

#### **2.4 Manganese (Mn)**

Plants accumulated Mn in the form of MnO. Mn was highly accumulated by the plants during the summer season and this also follows the trends of Zn and Ni. The average concentration for Mn accumulated by the plants were 5984.96 and 3950.78 μg/g in the summer and autumn seasons respectively as shown in **Figure 9**.

#### **2.5 Copper (Cu)**

In all the sampled plants, Cu was more highly accumulated by the plants in summer than in autumn in the same way as Zn, Ni, and Mn. The average

*Variation in the average Iron concentration accumulated by plant in summer and autumn.*

**Figure 9.** *Variation in the average Manganese concentration accumulated by plant in summer and autumn.*

concentration of Cu accumulated in the plants sampled during the summer and autumn months was 78.30 and 45.63 μg/g as shown in **Figure 10**.
