Determination of Metal Concentrations in Water

Determination of Metal Concentrations in Water, Sediments and Plant Tissue Samples from Ponds and Reservoirs, in Order to Assess the Level of Environmental Risk Related to Environmental Pollution
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Introduction
The subject of penetration of toxic and heavy metals into marine life is attracting a lot of attention from scholars and practitioners who study aquatic life. This owes to the reality that scholars such as Akpor et al. (2014) and Tabinda et al. (2013) made publications on the penetration of toxic metals into large water masses. It is notable however that the penetration of heavy metals into aquatic life is not limited to large water masses. For instance, Salem et al. (2014) and Salem et al. (2014) argue that surface runoff resulting from heavy downpours can flow into ponds. The runoff contains wastes that could contain heavy metals from industries. What are heavy metals? Akpor et al., (2014) define heavy metals as elements possessing an atomic density, which is greater than 6 g/cm3. Clearly, it is important to examine the existence of such elements in ponds and reservoirs. Consequently, this paper discusses the determination of metal concentrations in water, sediments, and plant tissue samples from ponds and reservoirs in order to assess the level of environmental risk related to environmental pollution in Harpurhey Northern Manchester.
Field and Laboratory Methods
Harpurhey Northern Manchester is approximately three miles to the north of Manchester city centre. This was the study area because data was collected exclusively from this section of Manchester City. In order to collect data from the entire section under study, different groups collected data from different sections. Simply put, nine groups collected data from different sections of the study area. Additionally, the study section was divided into five major sites to prevent the data collectors from collection information from one section of the study area. These sites were labelled as site one, site two, site three, site four and site five. Each of the groups was assigned specific sites of data collection. It is crucial to highlight that some sites had more of groups collecting data than others because the sites varied in terms of size and the number of ponds and reservoirs.
Materials
The following materials were used to conduct the study.
Gloves and safety glasses
White plastic trays
Four x aluminium foil beakers
Buchner apparatus
4x30ml universal tubes
Deionised water bottles
Three different plant samples
Marker pen
Scalpel and scissors
25ml volumetric flask
Whatman grade 3 (6um) filter paper
4 x 50ml flasks
Two point weighing balance
Sediment sample and water samples
Methods
In order to collect dry sediment, a small section of a sediment core were cut, put into a labelled foil beaker, and exposed to a temperature of 80 degrees Celsius for 1 hour. Superficial sediment was washed off and dried with a dry towel. Dry plant tissue was collected and exposed to a temperature of 80 degrees Celsius before acid digestion was completed in a fume cupboard (which was completed using the following procedure). A 2g subsample was weighed into a 50ml flask before 5ml of nitric acid (HNO3) was added to the subsample. A marble was placed on top of the flask, which was set (the flask) on a hot plate at 850C to digest. The samples were watched at all times as they evaporated to dryness. After the acid evaporated, the flask was removed from the hot plate and allowed to cool. 10 ml of water was used to re-suspend the residue.
It is also critical that subsamples of plant tissue for Cold Acid Digest were collected using the following procedure. One gram of dried plant tissue (of each type) was put into 50 ml labelled flasks. 5ml of sixty-five per cent nitric acid was added to the flask before it was set on a tray to digest (for forty-five minutes). The sample was watched continuously to check whether the sample proved recalcitrant. Warming on the hotplate was used to speed the digestion process.
The digested samples were filtered using a Buchner funnel and a filter paper under reduced air pressure. The filtrate was decanted into a labelled 25-30ml universal tube and set for metal concentration tests using the ICPS procedure. Results were collated and analysed using MS-Excel and SPSS.
Results and Discussion
The Statistical Package for Social Sciences (SPSS) and Microsoft Excel were used to explore the nature of the data collected. Specifically, they were used to analyse descriptive statistics. The means, medians, standard deviations, and quartiles for metal concentrations in plants were obtained as shown in Figure 1 and Table 1 below. The results indicate that potassium has the highest measures of central tendency while cadmium has the lowest measures of central tendency in plants. Analogously, plants in ponds from Harpurhey Northern Manchester recorded cadmium as the lowest concentration of metal. Figure 2 and Table 3 below indicates the interquartile range for the different sites and breeds.


Figure  SEQ Figure \* ARABIC 1



Figure  SEQ Figure \* ARABIC 2 Figure  SEQ Figure \* ARABIC 3


Table  SEQ Table \* ARABIC 1
However, the concentration of metals in sediments from Harpurhey Northern Manchester was different from the concentration of plants. As evidence, Figure 4 below indicates that calcium recorded the highest concentration of sediments from ponds and reservoirs in Harpurhey Northern Manchester. Similarly, cadmium recorded the lowest concentration of sediments from ponds and reservoirs in Harpurhey Northern Manchester. This is shown in Figure 4 below. Clearly, the results of the amount of metal concentration indicate that dangerous elements such as cadmium, arsenic, vanadium, and nickel were in low concentrations. Authors such as Nziku and Namkinga (2013), Saeed and Shaker (2008), Kumar et al., (2008), Kenšová, et al., (2012) and Kenšová et al., (2009) obtained similar results. It is also notable that non-toxic metal elements such as Aluminium, Zinc, Calcium, Potassium, magnesium, manganese, and iron had high concentrations in both plants and sediments. Scholars such as Ciszewski et al., (2013), Peltier et al., (2003), Vácha et al, (2011), and Arunakumara et al., (2007).


Figure  SEQ Figure \* ARABIC 4
The Kruskal Wallis non-parametric tests was used to examine whether the concentration of metals in plants and sediments differ significantly. This owes reality that the data was non-normal implying a non-parametric test is appropriate for testing significant differences between variables (Braun 2012). Peck et al., (2012), further highlights that non-parametric tests are applicable when the researcher identifies an abnormal deviation of observations from the mean. Simply put, the median is better than the mean in such cases, and the Kruskal Wallis test uses the median to test for a significant difference. For the case under study, the researcher used the following hypotheses.
H0: There is no significance difference in the metal concentrations in plants and sediments in ponds and reservoirs from Harpurhey Northern Manchester.
H1: There is a significance difference in the metal concentrations in plants and sediments in ponds and reservoirs from Harpurhey Northern Manchester.
The results of the analysis are shown in Table 2 below




Table  SEQ Table \* ARABIC 2
From the results above, there are cases where the P-value is less than 0.05 and cases where the P-value is more than 0.05. Therefore, we reject or fail to reject the null hypothesis as indicated in Table 2 above. Rejecting the null hypothesis implies that that there is a significant difference in the metal concentrati...