Oil spillage measures caused drastic reduction in total petroleum hydrocarbon levels in petroleum depot in Ibadan, Southwestern Nigeria

Figures & data

Figure 1. Map of study area showing sampling points.

Table 1. Reference dose and slope factor values of PAHs

	RfD (mg/kg/day)	SF(1/mg/kg/day)
Acenaphthene	0.06
Acenaphthylene	0.06
Anthracene	0.3
Benz[a]anthracene		0.73
Benzo[a]pyrene	0.0003	2.3
Benzo[e]pyrene	0.03
Benzo[ghi]perylene	0.03
Benzo[k]fluoranthene		0.073
Chrysene		0.0073
Dibenzo[a,h]pyrene		7.3
Fluoranthene	0.04
Indeno[1,2,3-cd]pyrene	0.03	0.73
Naphthalene	0.02
Pyrene	0.03

Source: American Standard Testing Method (ASTM) (2002, 2004).

Table 2. Physicochemical parameters of surface water within NNPC Apata depot

Sample points (m)	pH	Temp (^oC)	EC (µS/cm)	TDS (mg/L)	Acidity (mg/L)	Alkalinity (mg/L)	COD (mg/L)	Nitrate (mg/L)	Phosphate (mg/L)
PS	7.60 ± 0.01^a	26.40 ± 3.00^d	351 ± 7.00^b	174 ± 11.00 ^c	7.00 ± 0.01^d	0.80 ± 0.01^i	55.20 ± 7.00^a	5.89 ± 0.01^a	10.25 ± 0.07 ^c
DS 200	7.35 ± 0.03^b	26.60 ± 0.13 ^c	292 ± 3.00 ^f	146 ± 4.00 ^f	2.00 ± 0.02 ^f	0.80 ± 0.02^i	46.40 ± 10.00^d	3.26 ± 0.50 ^f	9.96 ± 0.10^d
DS 400	7.45 ± 0.02^b	27.00 ± 0.04^ab	326 ± 28.00^d	163 ± 15.10^d	21.00 ± 5.00^a	4.40 ± 0.03 ^h	27.50 ± 3.00^i	4.32 ± 0.03^d	10.58 ± 2.05^b
DS 600	7.40 ± 0.01^b	27.15 ± 0.08^ab	334 ± 10.00 ^c	166 ± 7.00^d	4.00 ± 0.97 ^f	11.40 ± 1.20^d	50.60 ± 15.00^b	1.72 ± 0.05 ^h	6.78 ± 1.25 ^g
DS 800	7.64 ± 0.03^a	27.10 ± 0.10^ab	342 ± 7.00^b	171 ± 20.00 ^c	6.00 ± 0.50^e	14.40 ± 3.20^b	40.30 ± 12.00 ^f	4.67 ± 1.23 ^c	10.76 ± 3.25^b
UPS 200	7.27 ± 0.12^bc	26.90 ± 2.50^b	303 ± 1.00^e	155 ± 8.00^e	16.00 ± 2.00^b	4.80 ± 0.10 ^g	36.20 ± 2.00 ^g	5.36 ± 0.02^b	12.03 ± 0.08^a
UPS 400	7.33 ± 0.05^b	27.20 ± 1.50^ab	407 ± 6.00^a	204 ± 7.00^a	12.00 ± 4.00 ^c	12.40 ± 6.00 ^c	30.60 ± 4.50 ^h	3.60 ± 0.80^e	10.50 ± 3.00^b
UPS 600	7.53 ± 0.06^ab	27.35 ± 0.08^a	399 ± 4.00 ^h	199 ± 3.00^b	8.00 ± 0.80^d	10.96 ± 2.50^e	48.00 ± 10.00 ^c	2.00 ± 0.05 ^g	8.00 ± 0.60 ^f
UPS 800	7.61 ± 0.02^a	27.50 ± 0.20^a	274 ± 2.28^i	128 ± 5.00 ^g	6.00 ± 1.00^e	6.25 ± 1.60 ^f	42.80 ± 8.00^e	4.50 ± 1.50 ^c	9.50 ± 2.00^e
C	7.10 ± 0.02^bc	27.00 ± 0.20^ab	253 ± 8.00 ^g	124 ± 5.00 ^g	12.00 ± 0.77 ^c	15.00 ± 5.00^a	20.10 ± 8.00 ^j	1.49 ± 0.67^i	5.35 ± 0.67 ^f
World Health Organization WHO (2011)	6.5–8.5	-	1000	600	4	-	200	50	< 5

*Mean values with the same superscript along the same column are not significantly (P > 0.05) different from each other.

*PS- Point source, DS- Downstream, UPS- Up stream and C-Control.

*EC-Electrical conductivity, Temp- Temperature, TDS- Total Dissolve Solid, COD- Chemical Oxygen Demand.

Table 3. Concentration of aliphatic hydrocarbons in surface water samples (ng/L)

Aliphatic Congeners	PS	DS200	DS400	DS600	DS800	UPS200	UPS 400	UPS 600	UPS 800	C
C8	15.30 ± 3.12^d	58.50 ± 6.50^a	27.27 ± 11.71 ^c	12.87 ± 3.25^e	29.53 ± 2.52^b	6.77 ± 0.17 ^f	ND	ND	ND	0.06 ± 0.00 ^g
C9	7.03 ± 1.10^a	6.50 ± 0.30^b	4.83 ± 0.86 ^c	ND	1.00 ± 0.02^d	5.07 ± 0.72 ^c	ND	ND	ND	ND
C10	5.23 ± 0.68^b	9.33 ± 2.92^a	5.23 ± 2.64^b	4.60 ± 0.02 ^c	9.30 ± 1.40^a	1.83 ± 0.56^d	ND	ND	ND	0.13 ± 0.00^e
C11	1.73 ± 0.92 ^c	2.97 ± 0.32^a	2.33 ± 0.54^b	1.53 ± 0.40 ^c	3.13 ± 0.65^a	0.77 ± 0.13^d	ND	ND	ND	ND
C12	1.30 ± 0.81^d	1.67 ± 0.11 ^c	1.17 ± 0.01^d	0.73 ± 0.27^d	1.13 ± 0.91^d	5.40 ± 0.24^a	ND	3.25 ± 0.01^b	1.05 ± 0.03^e	0.01 ± 0.00 ^f
C13	16.00 ± 3.02^b	4.77 ± 0.41^d	2.87 ± 0.20 ^g	3.90 ± 1.15^e	5.43 ± 2.74 ^c	53.07 ± 2.57^a	3.20 ± 0.02 ^f	3.32 ± 0.04 ^f	1.50 ± 0.05 ^h	0.07 ± 0.02^i
C14	102.73 ± 9.37^a	38.03 ± 10.00^d	32.37 ± 3.55^e	41.57 ± 10.55 ^c	62.03 ± 12.52^b	30.20 ± 4.35 ^f	ND	ND	ND	0.29 ± 0.05 ^g
C15	57.10 ± 14.44^a	32.60 ± 11.08 ^c	20.30 ± 2.35^e	24.33 ± 7.47^d	56.77 ± 14.25^a	40.00 ± 8.07^b	ND	4.82 ± 0.06 ^f	2.00 ± 0.04 ^g	0.13 ± 0.01 ^h
C16	66.20 ± 26.95^b	38.40 ± 12.75 ^c	28.20 ± 4.60^e	32.83 ± 10.38^d	70.73 ± 10.57^a	11.30 ± 3.80 ^f	2.38 ± 0.05 ^g	2.08 ± 0.03 ^h	1.20 ± 0.02 ^g	0.15 ± 0.01 ^h
C17	20.07 ± 3.07 ^c	23.63 ± 4.79^b	11.10 ± 3.59^d	10.50 ± 3.50^e	20.30 ± 4.18 ^c	69.83 ± 16.89^a	2.57 ± 0.01 ^f	2.65 ± 0.10 ^f	1.10 ± 0.06 ^g	0.03 ± 0.02 ^h
C18	116.00 ± 26.98^b	78.80 ± 23.27 ^c	51.27 ± 14.75^e	58.20 ± 18.60^d	129.50 ± 18.92^a	7.70 ± 0.89 ^f	6.18 ± 0.03 ^g	4.01 ± 0.03 ^h	2.00 ± 0.05^i	0.25 ± 0.06 ^j
C19	10.43 ± 1.60^d	14.43 ± 1.21^b	6.40 ± 0.14^e	6.27 ± 3.64^e	13.20 ± 0.37 ^c	105.00 ± 11.86^a	ND	ND	ND	0.02 ± 0.00 ^f
C20	315.73 ± 28.42^a	48.63 ± 13.06^e	83.43 ± 10.94 ^c	66.60 ± 20.60^d	188.53 ± 14.64^b	10.57 ± 0.72 ^f	3.81 ± 0.01 ^g	3.98 ± 0.04 ^g	1.65 ± 0.05 ^h	0.28 ± 0.08^i
C21	6.13 ± 2.55^e	19.87 ± 0.71^b	6.07 ± 0.39^e	11.47 ± 3.48^d	17.63 ± 2.46 ^c	55.93 ± 16. 49^a	7.34 ± 0.02	5.37 ± 0.02	3.25 ± 0.06	0.03 ± 0.00 ^f
C22	114.20 ± 14.63^b	69.03 ± 10.87 ^c	41.53 ± 10.01^e	48.83 ± 5.88^d	144.87 ± 44.40^a	12.17 ± 0.15 ^f	4.90 ± 0.04 ^g	5.23 ± 0.08 ^g	2.10 ± 0.01 h	0.21 ± 0.06^i
C23	17.13 ± 4.82^d	26.20 ± 6.62^b	11.03 ± 2.34 ^f	14.10 ± 2.08^e	23.13 ± 2.96 ^c	40.10 ± 5.02^a	2.65 ± 0.02 ^h	3.20 ± 0.04 ^g	1.50 ± 0.02^i	0.04 ± 0.02 ^j
C24	73.17 ± 20.64^b	54.70 ± 10.62 ^c	30.80 ± 4.85^e	36.97 ± 6.75^d	78.43 ± 19.58^a	22.43 ± 0.10 ^f	3.57 ± 0.03 ^g	3.17 ± 0.02 ^h	1.60 ± 0.03^i	0.20 ± 0.09 ^j
C25	38.13 ± 10.99^d	55.97 ± 10.75^a	21.50 ± 4.43 ^f	28.73 ± 4.05^e	48.80 ± 12.37^b	48.43 ± 10.49 ^c	5.86 ± 0.01 ^g	4.76 ± 0.08 ^h	2.20 ± 0.04^i	0.03 ± 0.01 ^j
C26	77.87 ± 20.00 ^c	80.47 ± 19.43^b	39.90 ± 2.31^e	62.40 ± 10.51^d	104.03 ± 20.22^a	15.63 ± 0.24 ^f	3.06 ± 0.02 ^g	2.76 ± 0.02 ^h	1.20 ± 0.03^i	0.18 ± 0.07 ^j
C27	38.13 ± 5.93^d	68.93 ± 27.25^a	14.90 ± 0.30 ^f	39.20 ± 5.69 ^c	27.57 ± 3.92^e	42.17 ± 22.83^b	ND	ND	ND	0.11 ± 0.04 ^g
C28	73.50 ± 20.61 ^c	78.57 ± 17.53^b	34.73 ± 6.27^e	57.43 ± 7.68^d	78.37 ± 10.91^a	18.20 ± 0.90 ^f	3.44 ± 0.05 ^g	3.33 ± 0.02 ^g	1.40 ± 0.01 ^h	0.15 ± 0.05^i
C29	26.97 ± 2.21^e	73.20 ± 19.30^a	17.17 ± 2.09 ^f	33.53 ± 10.67 ^c	40.47 ± 11.85^b	30.53 ± 4.33^d	5.56 ± 0.06 ^g	3.56 ± 0.01 ^h	1.70 ± 0.02^i	0.08 ± 0.06 ^j
C30	40.07 ± 13.68 ^c	44.73 ± 4.35^b	29.53 ± 7.00^e	38.67 ± 6.91^d	48.87 ± 10.81^a	22.23 ± 4.83 ^f	3.01 ± 0.04 ^g	2.80 ± 0.04 ^g	1.20 ± 0.03 ^h	0.10 ± 0.01^i
C31	39.23 ± 4.49 ^c	31.87 ± 3.30^d	16.03 ± 4.08 ^f	39.77 ± 4.89^b	49.23 ± 12.59^a	23.93 ± 1.14^e	5.38 ± 0.02 ^g	2.74 ± 0.02 ^h	1.30 ± 0.04^i	0.11 ± 0.00 ^j
C32	41.37 ± 17.67^b	39.43 ± 3.59 ^c	18.23 ± 3.49^e	32.93 ± 10.49^d	49.47 ± 15.47^a	10.83 ± 2.52 ^f	3.47 ± 0.01 ^g	ND	ND	0.10 ± 0.02 ^h
C33	33.33 ± 5.57 ^c	31.70 ± 0.26^d	9.17 ± 1.36 ^f	34.73 ± 7.00^b	54.33 ± 14.60^a	19.83 ± 3.65^e	4.30 ± 0.05 ^g	ND	ND	0.08 ± 0.04 ^h
C34	32.37 ± 3.98^b	31.37 ± 9.29 ^c	11.10 ± 0.71^e	24.53 ± 3.33^d	51.37 ± 15.97^a	10.20 ± 1.41 ^f	3.06 ± 0.01 ^g	ND	ND	0.09 ± 0.03 ^h
C35	21.77 ± 6.66^a	21.77 ± 3.37^b	8.30 ± 1.20^e	16.53 ± 5.51 ^c	21.77 ± 6.29^a	12.80 ± 3.00^d	ND	ND	ND	0.04 ± 0.01 ^f
C36	19.40 ± 2.82 ^c	20.33 ± 3.94^b	10.63 ± 2.24^e	18.20 ± 3.57^d	28.07 ± 5.01^a	6.63 ± 0.79 ^f	ND	ND	ND	0.06 ± 0.02 ^g
C37	10.73 ± 0.33 ^c	12.60 ± 2.91^a	6.53 ± 1.23^e	11.73 ± 2.98^b	11.87 ± 2.04^b	6.87 ± 1.20^d	ND	ND	ND	0.03 ± 0.01 ^f
C38	10.50 ± 3.84^d	11.27 ± 3.75^b	6.23 ± 2.71^e	10.80 ± 3.27 ^c	17.47 ± 3.89^a	3.67 ± 0.38 ^f	ND	ND	ND	0.02 ± 0.01 ^g
C39	4.90 ± 1.49 ^c	2.60 ± 1.26^d	2.53 ± 0.39^d	6.00 ± 1.22^b	8.07 ± 2.95^a	2.20 ± 0.35^e	ND	ND	ND	0.01 ± 0.01 ^f
C40	4.50 ± 2.79 ^c	1.73 ± 0.50 ^f	2.17 ± 0.75^e	3.57 ± 1.09^d	6.77 ± 2.77^b	300.50 ± 3.81^a	4.56 ± 0.20 ^c	ND	ND	0.01 ± 0.00 ^g
Total(ng/L) Aliphatic	1458.27 ± 286.2	1134.6 ± 246.2	614.87 ± 119.1	834.07 ± 186.6	1500.5 ± 255.4	1052.79 ± 117.8	78.30 ± 0.7	61.03 ± 0.7	27.45 ± 0.6	3.11 ± 0.9
Mean	44.19 ± 8. 7	25.23 ± 7.5	18.63 ± 3.6	26.06 ± 5.8	45.45 ± 7.7	31.90 ± 3.6	4.12 ± 0.04	3.59 ± 0.04	1.62 ± 0.03	0.12 ± 0.03

*Mean with the same superscript along the same row are not significantly (P > 0.005) different from each other. ND—Not detected

Table 4. PAH concentrations in surface water samples of NNPC Apata Depot (ng/L)

PAH Congeners	PS	DS200	DS400	DS600	DS800	UPS200	UPS 400	UPS 600	UPS 800	C
Napthalene	0.53 ± 0.02^b	0.90 ± 0.01^a	0.80 ± 0.06^a	0.27 ± 0.06 ^c	0.47 ± 0.01^b	0.30 ± 0.04 ^c	ND	ND	ND	ND
1-Methyl Napthalene	1.27 ± 1.00^d	2.03 ± 0.52 ^c	5.27 ± 1.87^a	3.17 ± 0.71^b	0.17 ± 0.01^e	0.27 ± 0.05^e	ND	ND	ND	ND
2-Methyl Napthalene	1.40 ± 0.48 ^c	2.53 ± 0.20^b	4.20 ± 0.13^a	2.47 ± 0.75^b	0.13 ± 0.05^d	0.17 ± 0.01^d	ND	ND	ND	ND
Acenapthylene	1.17 ± 0.68^b	1.20 ± 0.91^b	2.47 ± 0.67^a	0.97 ± 0.50 ^c	0.60 ± 0.03 ^c	0.43 ± 0.17^d	ND	0.04 ± 0.01	ND	ND
Acenepthene	1.93 ± 0.35^e	2.97 ± 0.76^d	6.17 ± 1.83^a	3.53 ± 0.51^b	3.27 ± 0.40 ^c	0.67 ± 0.03	0.80 ± 0.04 ^f	0.81 ± 0.05 ^f	0.25 ± 0.05 ^g	ND
Flourene	5.70 ± 1.70 ^c	5.07 ± 1.69^d	15.23 ± 0.56^a	8.67 ± 0.71^b	4.50 ± 0.94^e	1.83 ± 0.90 ^f	ND	0.01 ± 0.01 ^g	ND	ND
Phenanthrene	14.33 ± 3.54^d	18.03 ± 3.75 ^c	38.07 ± 3.30^a	33.43 ± 3.40^b	11.20 ± 1.27^e	5.23 ± 0.58 ^f	0.03 ± 0.01 ^h	0.24 ± 0.02 ^g	0.02 ± 0.01 ^h	ND
Anthracene	6.83 ± 2.32 ^c	6.27 ± 1.30^d	15.20 ± 4.70^a	9.57 ± 1.79^b	3.60 ± 0.46^e	2.10 ± 0.89 ^f	ND	ND	ND	ND
Pyrene	2.60 ± 0.12^a	0.77 ± 0.12 ^c	1.17 ± 0.23^b	0.14 ± 0.06^d	0.50 ± 0.12 ^c	0.27 ± 0.05^d	5.21 ± 0.20	ND	ND	ND
Fluoranthene	4.93 ± 1.37^b	3.23 ± 0.49 ^c	6.27 ± 0.59^a	3.10 ± 0.64 ^c	2.47 ± 0.04^d	1.10 ± 0.42^e	ND	ND	ND	ND
Benzo(a) anthracene	2.50 ± 0.33^b	1.97 ± 0.24 ^c	4.13 ± 0.60^a	0.20 ± 0.02 ^f	0.23 ± 0.01 ^f	1.03 ± 0.16^d	0.40 ± 0.02^e	ND	ND	ND
Chrysene	1.90 ± 0.29 ^c	2.17 ± 0.67 ^c	15.53 ± 3.12^a	1.10 ± 0.06^d	0.87 ± 0.10^d	4.23 ± 0.02^b	ND	ND	ND	ND
Benzo(k) flouranthene	ND	ND	ND	ND	ND	ND	0.20 ± 0.01	ND	ND	ND
Benzo(b) flouranthene	0.63 ± 0.05^b	4.93 ± 0.70^a	ND	0.23 ± 0.01 ^c	0.30 ± 0.01 ^c	0.13 ± 0.03 ^c	ND	ND	ND	ND
Benzo(a) pyrene	6.00 ± 1.39^b	5.50 ± 0.27 ^c	15.00 ± 1.54^a	0.63 ± 0.15^e	0.47 ± 0.07^e	2.97 ± 0.38^d	ND	ND	ND	ND
Benzo(g,h,i) perylene	ND	1.20 ± 0.08^b	2.17 ± 0.75^a	ND	0.03 ± 0.01^d	0.90 ± 0.06 ^c	ND	ND	ND	ND
Dibenzo(a,h) anthracene	0.03 ± 0.01^b	1.07 ± 0.76^a	0.86 ± 0.16^a	0.07 ± 0.02^b	ND	0.03 ± 0.01^b	ND	ND	ND	ND
Indeno(1,2,3-cd)pyrene	0.57 ± 0.21 ^c	1.70 ± 0.94^b	3.27 ± 0.14^a	0.71 ± 0.05 ^c	ND	1.43 ± 0.15^b	ND	ND	ND	ND
Total (ng/L) PAHs	52.33 ± 13.60	61.53 ± 13.43	135.79 ± 20.32	68.25 ± 8.00	28.80 ± 3.00	23.10 ± 3.91	6.64 ± 0.28	1.10 ± 0.09	0.27 ± 0.06	ND
Mean	3.27 ± 0.85	3.85 ± 0.79	8.49 ± 1.27	4.27 ± 0.50	1.92 ± 0.20	1.36 ± 0.23	1.33 ± 0.06	0.28 ± 0.02	0.14 ± 0.03	ND
CPAHs	11.63 ± 2.28	18.54 ± 3.66	40.96 ± 6.31	2.94 ± 0.31	1.90 ± 0.20	10.72 ± 0.81	0.60 ± 0.03	ND	ND	ND

*Mean with the same superscript along the same row are not significantly (P > 0.05) different from each other. CPAHs: Carcinogenic polycyclic aromatic hydrocarbons. ND- Not detected.

Table 5. Total petroleum hydrocarbon concentrations in surface water samples (ng/L)

Sampling points (m)	Total Aliphatic	Total PAHs	TPH	Mean
UPS 800	27.45 ± 0.59^i	0.27 ± 0.06^i	27.72 ± 0.65	0.58 ± 0.01
UPS 600	61.03 ± 0.66 ^h	1.10 ± 0.09 ^h	62.13 ± 0.75	1.29 ± 0.02
UPS 400	78.30 ± 0.70 ^g	6.64 ± 0.28 ^g	84.94 ± 0.98	1.77 ± 0.02
UPS 200	1052.79 ± 286.18 c	23.10 ± 3.91 f	1075.89 ± 290.09	22.41 ± 6.04
PS	1458.27 ± 117.81^b	52.33 ± 13.60^d	1510.6 ± 131.41	31.47 ± 2.74
DS 200	1134.6 ± 246.18^d	61.53 ± 13.43 ^c	1196.1 ± 259.61	24.91 ± 5.40
DS 400	614.87 ± 119.13 ^f	135.79 ± 20.32^a	750.66 ± 139.45	15.64 ± 2.90
DS 600	834.07 ± 186.56^e	68.25 ± 8.00^b	902.32 ± 194.56	18.80 ± 4.05
DS 800	1500.5 ± 255.42^a	28.80 ± 3.00 ^e	1528 ± 258.42	31.85 ± 5.38
C	3.11	ND	3.11	0.10 ± 0.03

Concentrations with different superscripts along the same row are significantly (P < 0.05) different from each other. ND- Not detected.

Table 6. Carcinogenic risk for adults and children (benzo (a) pyrene and indeno (1, 2, 3 cd) pyrene)

	Exposure patterns (Ingestion)	PS		DS200		DS400		DS600		DS800		UPS 200
		Adult	Children	Adult	Children	Adult	Children	Adult	Children	Adult	Children	Adult	Children
Benzo(a)pyrene	CDI(mg/kg/day)	4.43 E-8	2.18 E-7	8.21 E-8	4.03 E-8	2.24 E-7	1.10 E-6	9.40 E-9	4.62 E-8	7.02 E-9	3.45 E-8	8.96 E-8	4.40 E-7
	HQ	1.48 E-4	7.27 E-4	2.74 E-4	1.34 E-3	7.46 E-4	3.67 E-3	3.13 E-5	1.54 E-4	2.34 E-5	1.15 E-4	2.99 E-4	1.47 E-3
	CR	1.02 E-7	5.01 E-7	1.89 E-7	9.27 E-7	5.15 E-7	2.53 E-6	2.16 E-8	1.06 E-7	1.61 E-8	7.94 E-8	2.06 E-7	1.01 E-6
Indeno[1,2,3-cd] pyrene	CDI(mg/kg/day)	2.13 E-8	1.05 E-7	2.54 E-8	1.25 E-7	4.88 E-8	2.40 E-7	1.06 E-8	5.21 E-8	-	-	8.51 E-9	4.18 E-8
	HQ	7.12 E-7	3.50 E-6	8.46 E-7	4.16 E-6	1.63 E-6	8.00 E-6	3.53 E-7	1.74 E-6	-	-	2.84 E-7	1.39 E-6
	CR	1.55 E-8	7.65 E-8	1.85 E-8	9.13 E-8	3.56 E-8	1.75 E-7	7.74 E-9	3.80 E-8	-	-	6.21 E-9	3.05 E-8
	ƩHQ = HI	1.49 E-4 7.31 E-4 2.75 E-4 1.34 E-3 4.48 E − 4 3.68 E-3 3.17 E-5 1.56 E-4 2.34 E-5 1.15 E-4 2.99 E-4 1.47 E-3

American Standard Testing Method (ASTM). (2002). Standard guide for risk- based corrective action applied at petroleum release sites” E1739-95. ASTM Website (www.astm.org).

 Google Scholar

American Standard Testing Method (ASTM). (2004). Standard guide for risk- based corrective action” applied at petroleum release sites” E2081-00. ASTM Website (www.astm.org).

 Google Scholar

World Health Organization WHO. (2011). Guidelines for drinking-water quality [Internet]. (4th ed.). http://www.who.int/water_sanitation_health/publications/2011/dwq_guidelines/en/

 Google Scholar