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Environmental Chemistry and Sanitation Engineering Division

Dr. Isaac O. A. Hodgson
(Chief Research Scientist/ Head of    Division)

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 Dr.Osmund D. Ansa-Asare
(Chief Research Scientist/Director)

 3

Dr. Kwadwo A. Asante
(Senior Research Scientist)

 

Dr. Anthony Y. Karikari
(Senior Research Scientist)

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Dr. Collins Tay
(Senior Research Scientist)

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Ms. Saada Mohammed
(Research Scientist)

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Mr. Humphrey F. Darko
(Senior Research Scientist)

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Mr. Michael Kumi
(Research Scientist)

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Mr. Samuel Obiri
(Senior Research Scientist)

 

The long-term objective of the Environmental Chemistry Division is to generate, process and disseminate water and wastewater quality information to end-users. Specific objectives are to:

  • perform quality and quantity assessments of industrial, agricultural and domestic discharges in both urban and rural areas and identify their impact on aquatic ecosystems;
  • collect, process and disseminate comprehensive high quality and reliable environmental data on surface and groundwater with regard to their chemical constituents; and
  • monitor pollution in coastal waters and lagoons in Ghana.

Currently, the major research programmes of the Division are:

  • Water quality monitoring;
  • Industrial wastewater studies;
  • Environmental impact studies; and
  • Development of strategies for water pollution control.

The following sections describe the research and development activities of the reporting year.

3.2.1    Polycyclic Aromatic Hydrocarbons in Irrigated Soil and Some Selected Irrigated Leafy Vegetables (Project Staff: Ms. Saada Mohammed – Research Scientist, Mr. Samuel Obiri – Research Scientist and Dr. Osmund D Ansa-Asare – Principal Research Scientist)

Wastewater use in urban agriculture is by far the most established application, and the one with the longest tradition. In most cases the irrigated lands are located in and around the urban areas where the wastewater is generated. Estimates on wastewater use worldwide indicate that about 20 million hectares of agricultural land is irrigated with untreated wastewater (World Bank Policy 2010). However, use of wastewater for irrigation could result in health and environmental problems, contaminating groundwater with nitrates and chemical pollutants, including heavy metals and polycyclic aromatic hydrocarbons (PAHs). Such pollutants may build up over time in the soil and be taken up by vegetables and food crops which are then eaten by man. PAHs are released to the environment mainly through anthropogenic activities such as production and combustion of petroleum, fossil fuels and other organic substances. They are formed mainly as a result of pyrolytic processes, especially the incomplete combustion of organic materials. PAHs generally occur as complex mixtures and are found throughout the environment in the air, water and soil (Gemma Falco 2003). PAHs are lipophillic and may accumulate in vegetation that could indirectly cause human exposure through food consumption. In most cases, diet is the main source of human exposure to these pollutants. Vegetables and in particular leafy vegetables, could act as an indicator of human exposure to PAHs (Tuteja, 2011). The main reason for concern about human exposure to these environmental pollutants is the evidence that various PAHs are carcinogenic, mutagenic as well as persistent (Gemma, 2003). It was against this background that the study was conducted to investigate the occurrence of PAHs in crops, irrigation water and soil for urban agriculture in the Greater Accra region of Ghana.

During the reporting period, random sampling techniques were adopted in selecting vegetable farms near the CSIR-INSTI. On each farm, the vegetables, soil, sediments and the urban waste water used to irrigate the farm were sampled for analysis. The samples were taken from four different sites (NC2, NC4A, NC4B and NC5) along the Nima Creek, which is in the Greater Accra region of Ghana where intensive urban agriculture is practised. However, with regard to water samples, NC4A and NC4B are referred to as NC4 because the same water source was used in irrigating both NC4A and NC4B. PAHs were extracted from the water, soil, sediment and vegetable samples, identified and quantified using the 6890B GC-MS with splitless injection.

 

At the site NC2, the dominant PAHs found were phenanthrene (Figure 12) which is a low molecular weight PAH and has three aromatic rings. The others are pyrene, benzo [a] anthracene, chrysene and benzo [a] pyrene which are high molecular weight PAHs, all of them have four aromatic rings while benzo [a] pyrene has five. The dominant PAHs at the site NC4A were phenantherene, pyrene and chrysene. Fluoranthene, pyrene and chrysene were found at site NC4B. With the exception of pheanantherene, which is a low molecular weight PAH and has a three aromatic ring, the rest are high molecular weight PAHs with four molecular rings. Sediments from NC5 contained nine out of the sixteen USEPA list of PAHs (Phenanthrene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene and dibenzo[a,h]anthracene) but in low concentrations from 0.031-0.304 µg/kg. The total concentrations of PAHs in the bulk soil from the NC2, NC4A, NC4B and NC5 were 0.392 µg/kg, 0.111 µg/kg, 0.102 µg/kg and 1.542 µg/kg, respectively (Figure 13). PAH adsorb strongly to the organic fraction of soils and do not penetrate deeply into most soils, therefore limiting both leaching to groundwater and availability for uptake by plants. The PAHs in the wastewater samples and Rose/Hibiscus leafy vegetable is shown in Figures 14 and 15.

At the end of the study, accumulation of lower molecular weight PAHs were found to be greater than the higher molecular PAHs in all the samples. The PAH concentrations in leafy vegetable plant parts were not strongly related to soil PAH levels but may be probably the result of atmospheric deposition. The leafy parts of the vegetables were found to be more contaminated with PAHs as compared to the stem and root parts. This may be due to their greater surface area, which is responsible to trap higher concentration of PAHs. The stem part was the least contaminated. The most dominant PAHs in the samples are the lower molecular weight PAHs; Naphthalene, Acenaphthylene, Fluorene, Phenanthrene, Anthracene, Fluoranthene and Pyrene which are not carcinogenic. The total PAHs concentration in the water and soil samples ranged from 3.89-11.40 ?g kg-1 and 0.102-1.54 ?g kg-1, respectively. For the leafy vegetables such as Rose/Hibiscus, Chinese cabbage, Lettuce and Garden egg leaves, the total PAHs concentration ranged from 0.496-16.2 ?g kg-1, 0.402-3.16 ?g kg-1, 4.27-5.42 ?g kg-1 and 0.037-9.29 ?g kg-1, respectively. The concentrations of the PAHs were within permissible limits and hence not poisonous. However, since PAHs are persistent and bioaccumulative, they might have long term health implications.

 

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Figure12: Chromatogram of sediment sample at NC2

Figure 13: PAHs in sediment sample along the Nima Creek

 

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Figure 14: PAHs in the wastewater samples

Figure 15: PAHs in the Rose/Hibiscus leafy vegetable

3.2.2    Water Compliance Monitoring Program at AngloGold Ashanti, Obuasi

(Project Staff: Dr. K. A. Asante – Senior Research Scientist, Mr. A. Y. Karikari – Research Scientist, Mr. Mark O. Akrong – Research Scientist and Dr. O. D. Ansa-Asare – Principal Research Scientist)

The study, as part of AngloGold Ashanti (AGA), Obuasi Mine’s efforts to adhere to compliance and regulatory requirements of the Environmental Protection Agency (EPA), was undertaken to:

monitor and present data analysis of the water quality status of Pond 3 and other surface water, ground water and oil and grease monitoring locations; and provide the Environmental Department of AngloGold Ashanti, Obuasi Mine with a reliable monitoring report to address environmental compliance. 

In the reporting year, a total of 62 samples, consisting of groundwater, surface water and oil and grease samples, were collected from the compliance points (COP) (15 samples), surveillance points (SP) (7 samples), control points (CP) (7 samples); Pond 3 water (20 samples) and QA/QC & travel blanks (13 samples). In addition, 20 sediment samples were taken from ten points in Pond 3. These samples were analysed physico-chemically and bacteriologically.

The physico-chemical quality for the surface water samples largely conformed to the water quality guidelines albeit turbidity (7 SPs and 2 CPs) and but ammonia (6 SPs, 1 COP and 1 CP) exceeded. About 41.7 % and 58.3 % of the samples exceeded the dissolved Mn and Hg guideline values, respectively. Manganese is normally found in soils but its presence in some surface water samples was not directly related to the activities of AGA. The presence of Hg could be due to illegal mining activities in the area as AGA does not use Hg in its operations. Mercury was detected in most samples but the levels were not alarming. For total metal concentration, about 41.7 % of the samples (all SPs) exceeded the water quality guideline value for Mn. For the groundwater samples, SE1D (COP) exceeded the water quality guidelines in 7 physico-chemical parameters and the water quality guideline value for turbidity was exceeded in all but one sample. Five COP sites also exceeded the sulphate guideline value. For total metal concentrations, Fe was exceeded at all the sampling sites and 42.9 % of the samples exceeded the guideline value for Mn. Pond 3 water samples (all SP) met the EPA effluent quality guidelines except conductivity and TDS. Pond 3 water samples contained elevated concentrations of SO4, NH3 and total hardness. However, these parameters have no EPA guidelines. Dissolved and total metal concentrations in Pond 3 were generally low and below the EPA guideline values. For bacterial contamination, 40% and 70% of all COP sites of the boreholes were devoid of total and faecal coliform, respectively. Nine (64.3%) of the boreholes had E. coli counts which conformed to the water quality guideline value of zero (0) E. coli count per 100 ml. For the surface water, only PROD and all COP sites had total coliform and faecal coliform counts, respectively conforming to the water quality guideline of 0 cfu/100ml. E. coli counts were detected in 35% of all the samples at Pond 3.

The bacteria contamination at some of the sampling sites in the groundwater, surface water and Pond 3 was generally higher in the 2nd quarter, 3rd quarter and 4th quarter sampling regimes than those recorded during the 1st quarter (Figures 16 – 18). Iron was the metal with the highest concentration in the sediment samples throughout the whole study, followed by Cu, Ni and Mn. Furthermore, Cu, Cr and Ni exceeded the TEC and TEL limits. In the first quarter, Sb was generally low and none of the sites exceeded the TEC and TEL limits for As.