Lab report

 

LAB REPORT

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INTRODUCTION

The rapid and accurate determination of heavy metals in environmental matrices such as soils and

sediments has led to the development and continuous improvement of various analytical methods concerning both (a) sample digestion and (b) the choice of most appropriate instrumental techniques to obtain exhaustive chemical information in the shortest time possible.

The determination of the total content and the leachable aliquot by aqua regia dissolution of eight heavy metals (Cd, Co, Cr,Cu, Mn, Ni, Pb, and Zn) in soils and sediments was developed by microwave digestion technique combined with inductively coupled plasma atomic emission spectrometry.

A complete digestion of soils and sediments was achieved by using an acid mixture of HF–HCl–HNO3(1:3:1); the microwave-irradiated closed vessel system used for the determination of aqua regia leachable quota, proved to be a viable alternative to the traditional reflux system.

The experimental study was conducted using five BCR standard reference materials (CRM 141R ‘Calcareous Loam Soil’, CRM 142 ‘Light Sandy Soil’, CRM 143 ‘Sewage Sludge Amended Soil’, CRM 277 ‘Estuarine Sediment’ and CRM 320 ‘River Sediment’) in two laboratories with different microwave ovens and ICP-OES.

Calculated recovery, repeatability, and reproducibility confirm the good performance of the procedures adopted. Microwave-assisted acid solubilisation [1–3] has proved to be the most suitable method for the diges tion of complex matrices such as soils and sediments containing oxides, clay, silicates and organic substances. This procedure allows shorter digestion times and good recoveries also for very volatile elements.

In addition, it reduces the risk of external contamination and requires smaller quantities of acids, thereby improving detection limits and the overall accuracy of the analytical method.Lab report

Consequences of these metals in the environment

Many metals are useful and important but at a higher concentration they become toxic. When these metals are in the environment they are excessively absorbed by roots and translocate to shoots leading to plant infestation, which when such plant is consumed by human is highly toxic and could cause damages.

Heavy metals, when excessively accumulated, are toxic to plants, since when they are in the soil, the excessively absorbed Heavy metals such as Zinc, Cadmium, lead, Manganese, are very difficult to remove from the environment because they are highly indestructible.

Lab report. Treating a site highly contaminated with heavy metals requires the use of viable and cost effective site remediation technology called bioremediation or the new technology called phytoremediation.

Remediation offers long term of contaminant removal, although the term for degradation varies with the level of metals contaminants, since high amount of metals contaminations requires long term degradation and cleans up (Wilson and Jones et al. 1993).

In biorestoration or bioremediation, microorganism (fungi and bacteria) are used to transform heavy metals such as lead, Zinc etc. to less toxic and less hazardous product (Garbis and Alkorta 1999 cited in Mejare and Bulow 2001).

Phytoremediation involves the use of plants to reduce pollutant such as heavy metals. This technology is more effective and an attractive approach of dealing with heavy contaminates. It helps to prevent destruction of landscape and also improves soil activity to maintain a healthy ecosystem (Salt et al. 1995).Lab report

Method/procedure

The same as the methods specified in the laboratory manual.

Results/raw data

Table 2.1: Raw result of the laboratory analysis

PARAMETER	As	Cd	Cu	Mn	Ni	Pb	Zn
BLANK 1 (mg/l)	0.011	0.000	0.014	0.056	0.005	1.685	0.021
BLANK 2 (mg/l)	0.012	0.001	0.012	0.061	0.009	1.417	0.026
Mean BLK (mg/l)	0.012	0.001	0.013	0.059	0.007	1.551	0.024
SOIL WYK 1(mg/l)	0.147	0.043	21.450	3.363	0.261	6.161	4.656
Corrected value(mg/l)	0.136	0.043	21.437	3.305	0.254	4.610	4.634
SOIL WYK 2(mg/l)	0.142	0.041	21.340	3.356	0.225	6.051	4.369
Corrected value(mg/l)	0.131	0.041	21.327	3.298	0.218	4.500	4.346
SOIL CWM 1(mg/l)	0.061	0.012	0.845	3.492	0.242	126.400	11.760
Corrected value(mg/l)	0.0495	0.012	0.832	3.434	0.235	124.849	11.737
SOIL CWM 2 (mg/l)	0.065	0.012	0.837	3.524	0.233	128.300	11.110
Corrected value(mg/l)	0.054	0.012	0.824	3.466	0.226	126.749	11.087
SOIL ALV 1(mg/l)	0.478	0.003	0.250	0.494	0.141	23.300	2.426
Corrected value(mg/l)	0.467	0.003	0.237	0.436	0.134	21.749	2.403
SOIL ALV 2 (mg/l)	0.475	0.004	0.241	0.506	0.138	23.760	2.406
Corrected value(mg/l)	0.464	0.004	0.228	0.448	0.131	22.209	2.383
SPIKE 1 (mg/l)	0.536	0.524	1.569	2.643	1.597	143.800	5.347
SPIKE 2 (mg/l)	0.531	0.518	1.552	2.628	1.573	143.200	5.312
mean spike (mg/l)	0.534	0.521	1.561	2.636	1.585	143.5	5.3295
Corrected value(mg/l)	0.522	0.521	1.548	2.577	1.578	141.949	5.306
LOD 1	0.020	0.000	0.015	0.058	0.005	1.608	0.024
LOD 2	0.023	0.001	0.015	0.064	0.007	1.315	0.028
LOD 3	0.001	0.001	0.018	0.064	0.005	1.357	0.03

From the results generated from the raw data in table 2.1 the standards for the different metals was tabulated.

 

Table 2.2: Metals concentration

Standards (mls)	As(mg/l)	Cd(mg/l)	Cu(mg/l)	Mn(mg/l)	Ni(mg/l)	Pb(mg/l)	Zn(mg/l)
0	0	0	0	0	0	0	0
1	0.50	0.50	1.50	2.50	1.50	125	5.00
2	1.00	1.00	3.00	5.00	3.00	250	10.00
3	1.50	1.50	4.50	7.50	4.50	375	15.00
4	2.00	2.00	6.00	10.00	6.00	500	20.00

 

DATA ANALYSIS

The figures on the table below were arrived at using the steps below. Examples of each row are seen below.

Average of soil sample weighed=0.503+0.502/2=0.503g to kg=0.0005kg approx. 0.50

From table 5, the corrected concentration of each analyte was derived from subtracting the blank from the actual concentration and this conc. was used in calculating the concentration in mg/kg for the 3 different soil samples.

Conc. in mg/kg= corrected conc. (mg/l) *volume in litres (0.1L)

Mass (kg)

=0.136mg/l*0.1L =27.10mg/kg

0.0005

Table 2.3: Data analysis for soil WYK, CWM and ALV (1 and 2)

PARAMETERS	As	Cd	Cu	Mn	Ni	Pb	Zn
WY          WYK1Conc.(mg/kg)	27.10	8.50	4287.40	660.90	50.80	922.00	926.50
WYK 2 Conc.(mg/kg)	26.10	8.10	4265.40	659.50	43.60	900.00	869.10
CW           CWM1 Conc.(mg/kg)	9.90	2.30	166.40	686.70	47.00	24969.80	2347.30
CWM2 Conc.(mg/kg)	10.70	2.30	165.80	693.10	46.20	25349.80	2217.30
ALV 1 Conc.(mg/kg)	93.30	0.50	47.40	87.10	26.80	4349.80	480.50
ALV 2 Conc.(mg/kg)	92.70	0.70	45.60	89.50	26.20	4441.80	476.50

 

%SPIKE RECOVERY

In other to calculate the % spike recovery, a spike sample was prepared from the sample matrix which was treated the same way as the analyte.  The formula for the calculation is as follows:

%spike recovery= conc gotten (mg/l) *100

Expected conc. (mg/l)

 

Table 2.4: %spike recovery of different heavy metals

PARAMETERS	As	Cd	Cu	Mn	Ni	Pb	Zn
Corrected spike conc(mg/l)	0.52	0.52	1.55	2.58	1.58	141.94	5.31
Expected conc(mg/l)	0.50	0.50	1.50	2.50	1.50	125.00	5.00
%recovery	104.40	104.10	103.16	103.08	105.20	113.56	106.12

 

LIMIT OF DETECTION

In other to calculate LOD =3 σ=3*0.009741=0.029223

Table2.5: LOD (mg/l) of different heavy metals

PARAMETERS	As	Cd	Cu	Mn	Ni	Pb	Zn
A(mg/l)	0.020	0.000	0.015	0.058	0.005	1.608	0.024
B(mg/l)	0.020	0.001	0.015	0.064	0.007	1.315	0.028
C(mg/l)	0.001	0.001	0.018	0.064	0.005	1.357	0.030
MEAN (mg/l)	0.015	0.001	0.016	0.062	0.006	1.427	0.027
Standard dev.(mg/l).	0.009	0.004	0.001	0.003	0.001	0.129	0.002
LOD=3σ	0.029	0.001	0.004	0.008	0.003	0.388	0.007

 

DISCUSSION

Average concentration of each of the soil samples was arrived at by:

Conc in mg/kg (1) + conc in mg/kg (2)

The table 2.5 was generated from table 8 and table 7 for the purpose of the discussion………continued