Extent of anthropogenic influence on groundwater quality and human health-related risks: an integrated assessment based on selected physicochemical characteristics

Figures & data

Figure 1. Maps showing the location of the metropolises and their underlying geologic formations.

Figure 2. A methodology flowchart depicting the study components and steps.

Table 1. Nitrate health risk parameters and their values for the various age groups (Ramalingam et al. 2022).

Parameter	Unit	Values for different age groups
		6 to 12 months	5 to 10 years	10 to 15 years	15 to 20 years	20 to 60 years	>60 years
Ingestion ratio (IR)	mL/day	0.8	1.35	1.9	2.2	2.94	2.6
Exposure duration (ED)	years	0.75	8	13	18	40	64
Frequency of exposure (EF)	days	365	365	365	365	365	365
Body weight (BW)	kg	11	25	35	55	76	65
Average age (AT)	days	274	2920	4745	6570	14,600	23,360
Reference dose (RfD)	mg/kg per day	1.6	1.6	1.6	1.6	1.6	1.6
Contact duration (TC)	h/d	0.4	0.4	0.4	0.4	0.4	0.4
Dermal absorption (Ki)	cm/h	0.001	0.001	0.001	0.001	0.001	0.001
Frequency of bathing (EV)	times/day	1	1	1	1	1	1
Skin surface area (SSA)	cm^2	4500	10,500	15,700	19,550	19,800	19,400
Conversion factor (CF)	–	0.001	0.001	0.001	0.001	0.001	0.001

Table 2. Physicochemical variables tested in groundwater resources from the urban clusters.

Sample ID	T (oC)	pH	EC (µS/cm)	NO3- (mg/L)	PO43-(mg/L)	Cl- (mg/L)	SO42-(mg/L)	HCO3- (mg/L)	Ca2+ (mg/L)	Mg2+ (mg/L)	Na+ (mg/L)	K+ (mg/L)
ABH01	26.00	4.80	412.00	1.10	0.90	63.00	6.00	25.00	63.00	25.00	8.00	3.00
ABH02	27.00	5.50	120.00	0.80	0.40	34.00	7.00	70.00	14.00	15.00	8.00	2.80
ABH03	24.00	5.60	240.00	2.30	0.80	55.00	12.00	40.00	28.00	17.00	5.00	3.20
ABH04	26.00	6.00	180.00	4.20	1.20	76.00	11.00	39.00	58.00	24.00	17.00	2.60
ABH05	24.00	5.90	17.00	0.80	0.00	80.00	13.00	52.00	48.00	18.00	10.00	1.20
ABH06	25.00	5.80	12.00	0.90	0.00	94.00	8.00	30.00	83.00	19.00	23.00	2.00
ABH07	23.00	6.10	41.50	0.50	0.70	149.00	8.00	32.00	53.00	25.00	4.00	3.00
ABH08	27.00	6.00	43.00	1.20	0.00	67.00	9.00	25.00	47.00	45.00	8.00	1.40
ABH09	27.00	5.80	60.00	0.60	0.00	82.00	10.00	180.00	60.00	51.00	12.00	1.00
ABH10	26.00	5.50	33.00	0.40	0.00	60.00	4.00	184.00	45.00	56.00	14.00	0.80
NBH01	26.00	7.50	108.40	0.18	0.06	70.50	4.20	6.00	6.20	4.40	12.00	5.00
NBH02	27.00	4.50	92.50	0.17	0.08	68.20	14.50	7.00	4.78	2.80	8.00	2.00
NBH03	25.00	6.20	35.20	1.20	0.80	39.00	2.83	3.00	4.20	0.83	12.00	3.00
NBH04	26.00	5.10	87.50	2.10	1.20	38.00	5.40	2.00	9.63	1.70	24.00	7.00
NBH05	28.00	7.30	30.50	1.00	1.30	42.00	4.27	4.00	1.72	0.73	6.00	5.00
NBH06	28.00	6.30	89.30	0.15	1.10	48.00	2.80	2.00	10.31	5.80	23.00	1.00
NBH07	25.00	4.70	64.10	0.04	0.20	18.30	23.00	1.00	11.91	1.30	5.20	2.00
NBH08	28.00	4.20	50.00	0.08	0.80	28.00	13.00	2.00	8.00	0.83	0.46	3.00
NBH09	27.00	7.30	66.00	0.03	0.03	20.15	10.00	5.00	17.00	0.72	12.00	0.93
NBH10	26.00	6.90	38.00	0.04	0.08	25.73	35.00	2.00	4.00	1.10	1.40	0.62
WHO (World Health Organization) (2017)	Ambient	6.5–8.5	1000.00	50.00	10.00	250.00	250.00	250.00	75.00	50.00	200.00	12.00
SON (Standard Organization of Nigeria) (2015)	Ambient	6.5–8.5	1000.00	50.00	NA	250.00	100.00	NA	NA	0.20	200.00	12.00

NA = not available

Table 3. Descriptive statistics of the analysed water quality parameters.

Sample ID	T (oC)	pH	EC (µS/cm)	NO3- (mg/L)	PO43-(mg/L)	Cl- (mg/L)	SO42-(mg/L)	HCO3- (mg/L)	Ca2+ (mg/L)	Mg2+ (mg/L)	Na+ (mg/L)	K+ (mg/L)
(a) Descriptive statistics for Awka urban cluster
Minimum	23.00	4.80	12.00	0.40	0.00	34.00	4.00	25.00	14.00	15.00	4.00	0.80
Maximum	27.00	6.10	412.00	4.20	1.20	149.00	13.00	184.00	83.00	56.00	23.00	3.20
Mean	25.50	5.70	115.85	1.28	0.40	76.00	8.80	67.70	49.90	29.50	10.90	2.10
(b) Descriptive statistics for Nnewi urban cluster
Minimum	25.00	4.20	30.50	0.03	0.03	18.30	2.80	1.00	1.72	0.72	0.46	0.62
Maximum	28.00	7.50	108.40	2.10	1.30	70.50	35.00	7.00	17.00	5.80	24.00	7.00
Mean	26.60	6.00	66.15	0.50	0.57	39.79	11.50	3.40	7.78	2.02	10.41	2.96
(c) SON and WHO acceptable limits
WHO (World Health Organization) (2017)	Ambient	6.5–8.5	1000.00	50.00	10.00	250.00	250.00	250.00	75.00	50.00	200.00	12.00
SON (Standard Organization of Nigeria) (2015)	Ambient	6.5–8.5	1000.00	50.00	NA	250.00	100.00	NA	NA	0.20	200.00	12.00

T = temperature; EC = electrical conductivity; NA = not available; WHO = World Health Organisation; SON = Standard Organisation of Nigeria

Table 4. Results of the WNPI, NPI and WPI assessments of the groundwater quality of the urban clusters.

	(a) NPI & WNPI values		(b) Pollution load of the analyzed parameters (PLi) and the final WPI values
Sample ID	NPI	WNPI	PLi (pH)	PLi (EC)	PLi (NO3)	PLi (PO4)	PLi (Cl)	PLi (SO4)	PLi (HCO3)	PLi (Ca)	PLi (Mg)	PLi (Na)	PLi (K)	WPI
ABH01	−0.945	0.362	4.400	0.412	0.022	0.090	0.252	0.024	0.100	0.840	0.500	0.040	0.250	0.630
ABH02	−0.960	0.289	3.000	0.120	0.016	0.040	0.136	0.028	0.280	0.187	0.300	0.040	0.233	0.398
ABH03	−0.885	0.393	2.800	0.240	0.046	0.080	0.220	0.048	0.160	0.373	0.340	0.025	0.267	0.418
ABH04	−0.790	0.421	2.000	0.180	0.084	0.120	0.304	0.044	0.156	0.773	0.480	0.085	0.217	0.404
ABH05	−0.960	0.116	2.200	0.017	0.016	0.000	0.320	0.052	0.208	0.640	0.360	0.050	0.100	0.396
ABH06	−0.955	0.185	2.400	0.012	0.018	0.000	0.376	0.032	0.120	1.107	0.380	0.115	0.167	0.473
ABH07	−0.975	0.330	1.800	0.042	0.010	0.070	0.596	0.032	0.128	0.707	0.500	0.020	0.250	0.378
ABH08	−0.940	0.141	2.000	0.043	0.024	0.000	0.268	0.036	0.100	0.627	0.900	0.040	0.117	0.415
ABH09	−0.970	0.095	2.400	0.060	0.012	0.000	0.328	0.040	0.720	0.800	1.020	0.060	0.083	0.552
ABH10	−0.980	0.075	3.000	0.033	0.008	0.000	0.240	0.016	0.736	0.600	1.120	0.070	0.067	0.589
NBH01	−0.991	0.426	0.333	0.108	0.004	0.006	0.282	0.017	0.024	0.083	0.088	0.060	0.417	0.129
NBH02	−0.992	0.178	5.000	0.093	0.003	0.008	0.273	0.058	0.028	0.064	0.056	0.040	0.167	0.526
NBH03	−0.940	0.354	1.600	0.035	0.024	0.080	0.156	0.011	0.012	0.056	0.017	0.060	0.250	0.209
NBH04	−0.895	0.745	3.800	0.088	0.042	0.120	0.152	0.022	0.008	0.128	0.034	0.120	0.583	0.463
NBH05	−0.950	0.567	0.200	0.031	0.020	0.130	0.168	0.017	0.016	0.023	0.015	0.030	0.417	0.097
NBH06	−0.993	0.196	1.400	0.089	0.003	0.110	0.192	0.011	0.008	0.137	0.116	0.115	0.083	0.206
NBH07	−0.998	0.187	4.600	0.064	0.001	0.020	0.073	0.092	0.004	0.159	0.026	0.026	0.167	0.476
NBH08	−0.996	0.332	5.600	0.050	0.002	0.080	0.112	0.052	0.008	0.107	0.017	0.002	0.250	0.571
NBH09	−0.999	0.081	0.200	0.066	0.001	0.003	0.081	0.040	0.020	0.227	0.014	0.060	0.078	0.072
NBH10	−0.998	0.060	0.200	0.038	0.001	0.008	0.103	0.140	0.008	0.053	0.022	0.007	0.052	0.057

ABH identifies groundwater from Awka whereas NBH identifies groundwater from Nnewi

Figure 3. Q-mode hierarchical dendrograms for classifying the water samples based on (a) NPI, (b) WNPI and (c) WPI. Samples 1–10, respectively, represent ABH1–ABH10, whereas samples 11–20 represent NBH1–NBH10, respectively.

Figure 4. Trends observed from the distribution of the water quality indices – WNPI, NPI and WPI. Samples 1–10, respectively, represent ABH1–ABH10, whereas samples 11–20 represent NBH1–NBH10, respectively.

Table 5. Result of the nitrate oral exposure health risk computation for the six age groups in the urban clusters.

	(a) Chronic daily intake (CDI) values						(b) Hazard quotient (HQ) and hazard index (HI) values
Sample ID	CDI (6–12 months)	CDI (5–10 years)	CDI (10–15 years)	CDI (15–20 years)	CDI (20–60 years)	CDI (> 60 years)	HQ (6–12 months)	HQ (5–10 years)	HQ (10–15 years)	HQ (15–20 years)	HQ (20–60 years)	HQ (> 60 years)	HI (oral)
ABH01	0.080	0.059	0.060	0.044	0.043	0.044	0.050	0.037	0.037	0.028	0.027	0.028	0.206
ABH02	0.058	0.043	0.043	0.032	0.031	0.032	0.036	0.027	0.027	0.020	0.019	0.020	0.150
ABH03	0.167	0.124	0.125	0.092	0.089	0.092	0.104	0.078	0.078	0.058	0.056	0.058	0.431
ABH04	0.305	0.227	0.228	0.168	0.162	0.168	0.191	0.142	0.143	0.105	0.102	0.105	0.787
ABH05	0.058	0.043	0.043	0.032	0.031	0.032	0.036	0.027	0.027	0.020	0.019	0.020	0.150
ABH06	0.065	0.049	0.049	0.036	0.035	0.036	0.041	0.030	0.031	0.023	0.022	0.023	0.169
ABH07	0.036	0.027	0.027	0.020	0.019	0.020	0.023	0.017	0.017	0.013	0.012	0.013	0.094
ABH08	0.087	0.065	0.065	0.048	0.046	0.048	0.054	0.041	0.041	0.030	0.029	0.030	0.225
ABH09	0.044	0.032	0.033	0.024	0.023	0.024	0.027	0.020	0.020	0.015	0.015	0.015	0.112
ABH10	0.029	0.022	0.022	0.016	0.015	0.016	0.018	0.014	0.014	0.010	0.010	0.010	0.075
NBH01	0.013	0.010	0.010	0.007	0.007	0.007	0.008	0.006	0.006	0.005	0.004	0.005	0.034
NBH02	0.012	0.009	0.009	0.007	0.007	0.007	0.008	0.006	0.006	0.004	0.004	0.004	0.032
NBH03	0.087	0.065	0.065	0.048	0.046	0.048	0.054	0.041	0.041	0.030	0.029	0.030	0.225
NBH04	0.153	0.113	0.114	0.084	0.081	0.084	0.095	0.071	0.071	0.053	0.051	0.053	0.393
NBH05	0.073	0.054	0.054	0.040	0.039	0.040	0.045	0.034	0.034	0.025	0.024	0.025	0.187
NBH06	0.011	0.008	0.008	0.006	0.006	0.006	0.007	0.005	0.005	0.004	0.004	0.004	0.028
NBH07	0.003	0.002	0.002	0.002	0.002	0.002	0.002	0.001	0.001	0.001	0.001	0.001	0.007
NBH08	0.006	0.004	0.004	0.003	0.003	0.003	0.004	0.003	0.003	0.002	0.002	0.002	0.015
NBH09	0.002	0.002	0.002	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.006
NBH10	0.003	0.002	0.002	0.002	0.002	0.002	0.002	0.001	0.001	0.001	0.001	0.001	0.007

Table 6. Result of the nitrate dermal contact exposure health risk computation for the six age groups in the urban clusters.

	(a) Dermally absorbed dose (DAD) values						(b) Hazard quotient (HQ) and hazard index (HI) values
Sample ID	DAD (6–12 months)	DAD (5–10 years)	DAD (10–15 years)	DAD (15–20 years)	DAD (20–60 years)	DAD (>60 years)	HQ (6–12 months)	HQ (5–10 years)	HQ (10–15 years)	HQ (15–20 years)	HQ (20–60 years)	HQ (>60 years)	HI (dermal)
ABH01	4.93E-07	5.06E-07	5.41E-07	4.28E-07	3.14E-07	3.60E-07	3.08E-07	3.16E-07	3.38E-07	2.68E-07	1.96E-07	2.25E-07	1.65E-06
ABH02	3.58E-07	3.68E-07	3.93E-07	3.12E-07	2.28E-07	2.62E-07	2.24E-07	2.30E-07	2.46E-07	1.95E-07	1.43E-07	1.64E-07	1.20E-06
ABH03	1.03E-06	1.06E-06	1.13E-06	8.96E-07	6.57E-07	7.52E-07	6.44E-07	6.62E-07	7.07E-07	5.60E-07	4.10E-07	4.70E-07	3.45E-06
ABH04	1.88E-06	1.93E-06	2.06E-06	1.64E-06	1.20E-06	1.37E-06	1.18E-06	1.21E-06	1.29E-06	1.02E-06	7.49E-07	8.59E-07	6.30E-06
ABH05	3.58E-07	3.68E-07	3.93E-07	3.12E-07	2.28E-07	2.62E-07	2.24E-07	2.30E-07	2.46E-07	1.95E-07	1.43E-07	1.64E-07	1.20E-06
ABH06	4.03E-07	4.14E-07	4.42E-07	3.51E-07	2.57E-07	2.94E-07	2.52E-07	2.59E-07	2.77E-07	2.19E-07	1.61E-07	1.84E-07	1.35E-06
ABH07	2.24E-07	2.30E-07	2.46E-07	1.95E-07	1.43E-07	1.64E-07	1.40E-07	1.44E-07	1.54E-07	1.22E-07	8.92E-08	1.02E-07	7.51E-07
ABH08	5.37E-07	5.52E-07	5.90E-07	4.67E-07	3.43E-07	3.92E-07	3.36E-07	3.45E-07	3.69E-07	2.92E-07	2.14E-07	2.45E-07	1.80E-06
ABH09	2.69E-07	2.76E-07	2.95E-07	2.34E-07	1.71E-07	1.96E-07	1.68E-07	1.73E-07	1.84E-07	1.46E-07	1.07E-07	1.23E-07	9.01E-07
ABH10	1.79E-07	1.84E-07	1.97E-07	1.56E-07	1.14E-07	1.31E-07	1.12E-07	1.15E-07	1.23E-07	9.74E-08	7.14E-08	8.18E-08	6.00E-07
NBH01	8.06E-08	8.28E-08	8.85E-08	7.01E-08	5.14E-08	5.89E-08	5.04E-08	5.18E-08	5.53E-08	4.38E-08	3.21E-08	3.68E-08	2.70E-07
NBH02	7.61E-08	7.82E-08	8.36E-08	6.62E-08	4.85E-08	5.56E-08	4.76E-08	4.89E-08	5.22E-08	4.14E-08	3.03E-08	3.48E-08	2.55E-07
NBH03	5.37E-07	5.52E-07	5.90E-07	4.67E-07	3.43E-07	3.92E-07	3.36E-07	3.45E-07	3.69E-07	2.92E-07	2.14E-07	2.45E-07	1.80E-06
NBH04	9.41E-07	9.67E-07	1.03E-06	8.18E-07	6.00E-07	6.87E-07	5.88E-07	6.04E-07	6.45E-07	5.11E-07	3.75E-07	4.29E-07	3.15E-06
NBH05	4.48E-07	4.60E-07	4.92E-07	3.90E-07	2.86E-07	3.27E-07	2.80E-07	2.88E-07	3.07E-07	2.43E-07	1.78E-07	2.04E-07	1.50E-06
NBH06	6.72E-08	6.90E-08	7.37E-08	5.84E-08	4.28E-08	4.91E-08	4.20E-08	4.32E-08	4.61E-08	3.65E-08	2.68E-08	3.07E-08	2.25E-07
NBH07	1.79E-08	1.84E-08	1.97E-08	1.56E-08	1.14E-08	1.31E-08	1.12E-08	1.15E-08	1.23E-08	9.74E-09	7.14E-09	8.18E-09	6.00E-08
NBH08	3.58E-08	3.68E-08	3.93E-08	3.12E-08	2.28E-08	2.62E-08	2.24E-08	2.30E-08	2.46E-08	1.95E-08	1.43E-08	1.64E-08	1.20E-07
NBH09	1.34E-08	1.38E-08	1.47E-08	1.17E-08	8.57E-09	9.81E-09	8.40E-09	8.63E-09	9.22E-09	7.30E-09	5.35E-09	6.13E-09	4.50E-08
NBH10	1.79E-08	1.84E-08	1.97E-08	1.56E-08	1.14E-08	1.31E-08	1.12E-08	1.15E-08	1.23E-08	9.74E-09	7.14E-09	8.18E-09	6.00E-08

Table 7. Total hazard index (THI) for the six age groups and the cumulative THI values for the urban clusters.

Sample ID	THI (6–12 months)	THI (5–10 years)	THI (10–15 years)	THI (15–20 years)	THI (20–60 years)	THI (>60 years)	Cumulative THI
ABH01	0.050	0.037	0.037	0.028	0.027	0.028	0.206
ABH02	0.036	0.027	0.027	0.020	0.019	0.020	0.150
ABH03	0.104	0.078	0.078	0.058	0.056	0.058	0.431
ABH04	0.191	0.142	0.143	0.105	0.102	0.105	0.787
ABH05	0.036	0.027	0.027	0.020	0.019	0.020	0.150
ABH06	0.041	0.030	0.031	0.023	0.022	0.023	0.169
ABH07	0.023	0.017	0.017	0.013	0.012	0.013	0.094
ABH08	0.054	0.041	0.041	0.030	0.029	0.030	0.225
ABH09	0.027	0.020	0.020	0.015	0.015	0.015	0.112
ABH10	0.018	0.014	0.014	0.010	0.010	0.010	0.075
NBH01	0.008	0.006	0.006	0.005	0.004	0.005	0.034
NBH02	0.008	0.006	0.006	0.004	0.004	0.004	0.032
NBH03	0.054	0.041	0.041	0.030	0.029	0.030	0.225
NBH04	0.095	0.071	0.071	0.053	0.051	0.053	0.393
NBH05	0.045	0.034	0.034	0.025	0.024	0.025	0.187
NBH06	0.007	0.005	0.005	0.004	0.004	0.004	0.028
NBH07	0.002	0.001	0.001	0.001	0.001	0.001	0.007
NBH08	0.004	0.003	0.003	0.002	0.002	0.002	0.015
NBH09	0.001	0.001	0.001	0.001	0.001	0.001	0.006
NBH10	0.002	0.001	0.001	0.001	0.001	0.001	0.007

Figure 5. Chadha plot showing the predominant water types in the study area.

Figure 6. Plots showing the geogenic implication of the relationships between (a) Ca²⁺/Na⁺ versus HCO₃^-/Na⁺ and (b) Ca²⁺/Na⁺ versus Mg²⁺/Na⁺.

Figure 7. Plots showing the anthropogenic implications of the relationships between (a) NO₃^- versus K⁺, (b) NO₃^- versus Cl^-, (c) NO₃^-/Cl^- versus Cl^- and (d) SO₄^2-/Ca²⁺ versus NO₃^-/Ca²⁺.

Figure 8. 3D image showing the graphical distribution of the principal components.

Table 8. Main extractions from the principal component analysis.

(a) Component matrix					(b) Component score coefficient matrix
Parameter	PC 1	PC 2	PC 3	PC 4	Parameter	PC 1	PC 2	PC 3	PC 4
T	−0.378	−0.090	0.522	0.632	T	−0.115	−0.034	0.339	0.480
pH	−0.107	−0.074	0.491	-0.545	pH	−0.033	−0.028	0.320	−0.414
EC	0.031	0.506	−0.492	0.399	EC	0.009	0.193	−0.320	0.303
NO3^-	0.179	0.748	−0.213	0.018	NO3^-	0.054	0.285	−0.138	0.014
PO4^3-	−0.388	0.779	−0.071	0.105	PO4^3-	−0.118	0.297	−0.046	0.079
Cl^-	0.702	0.217	−0.092	−0.474	Cl^-	0.214	0.083	−0.060	−0.360
SO4^2-	−0.202	-0.625	-0.559	−0.051	SO4^2-	−0.062	−0.238	−0.364	−0.039
HCO3^-	0.768	−0.151	0.211	0.347	HCO3^-	0.234	−0.058	0.137	0.263
Ca^2+	0.884	0.184	−0.143	−0.045	Ca^2+	0.269	0.070	−0.093	−0.034
Mg^2+	0.907	−0.023	0.085	0.262	Mg^2+	0.276	−0.009	0.055	0.199
Na^+	0.201	0.471	0.582	−0.047	Na^+	0.061	0.180	0.378	−0.036
K^+	−0.421	0.687	0.005	−0.176	K^+	−0.128	0.262	0.003	−0.133
Eigenvalue	3.283	2.625	1.538	1.317
% of variance	27.357	21.874	12.818	10.975
Cumulative %	27.357	49.231	62.049	73.024

Significant component loadings are in bold

Figure 9. R-mode hierarchical dendrogram for evaluating the possible influencers of water contamination.

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Data availability statement

All the data used in this article are provided herein.