Groundwater Quality Mapping in Kenedy County Armando Barrera* Mentors: Dr. Lee W. Clapp and Dr. Hongbo Su

Department of Environmental Engineering Texas A&M University – Kingsville

Introduction Toxic substances such as uranium, radon, and arsenic, as well as more

common substances like sodium, potassium, and manganese, can be

found in the groundwater in the South Texas area. However, existing data

related to concentrations of uranium and other groundwater constituents in

the boundaries of the Kenedy County Groundwater Conservation District is

very limited (Figure 1).

Research Objectives • To map the concentrations of uranium, radon, and arsenic found in

groundwater wells in Kenedy County, Texas, and to interpolate the data

to estimate the concentrations in the surrounding areas.

• To establish correlations between these toxic elements and

concentrations of major elements like sodium, calcium, etc.

Methodology

Preliminary Results

Thirty-five wells in Kenedy Country were sampled and analyzed for Na, K, Mg, Ca, Sr, V, Mn, Fe, As, Se, Mo, F-, Br-, Cl-, NO3

-, SO42-, Rn, pH, alkalinity,

hardness, conductivity and temperature. The wells were then georeferenced

using ArcGIS mapping software. Using inverse distance weighted raster

interpolation, maps were constructed to display the estimated

concentrations of the surrounding areas around the measured wells.

The method of interpolation used was inverted distance weighted (IDW).

This method determines cell values using a set of value points. It

assumes that the variable being mapped decreases in influence the

further from its sample point. The variable used is concentration, which is

assigned a cell value. The interpolation then calculates theoretical cell

values surrounding the known values, thus creating the raster image.

Several maps were created showing the concentration distribution of

substances over the area of Kenedy County. Radioactive substances such

as uranium and radon were found in relatively higher concentrations in the

northern area. Arsenic and manganese were found in relatively higher

concentrations in the center area, and sodium and potassium were in

relatively higher concentrations in the southern area.

The raster interpolation is unable to calculated values outside of the data

value set locations, thus well locations where the concentrations was below

the measurable detection limit were assumed to have no concentration for

interpolation purposes.

More sample data from other wells in nearby areas are necessary to

provide better accuracy in the raster image interpolation.

Figure 2. Uranium

concentrations

Figure 3. Arsenic

concentrations

Figure 4. Alkalinity

concentrations

Figure 5. Sulfate

concentrations

Figure 6. Manganese

concentrations

Figure 7. Calcium

concentrations

Well # Latitude Longitude Na (ppm) Mg (ppm) K (ppm) Ca (ppm) Sr (ppm) hardness (ppm

as CaCO3) V (ppb) Mn (ppb) Fe (ppb) As (ppb) Se (ppb) Mo (ppb) Th (ppb) U (ppb) F- (ppm) Br- (ppm) Cl- (ppm) NO3- (ppm) SO4

2- (ppm) PO43- (ppm) Rn (pCi/L) pH Alk (mg/L CaCO3) HCO3- (ppm) CO3-2 (ppm) EC (μS/cm) Temp (oC) Scations Sanions % error

1 27.23756 -97.78803 289 8.59 9.50 28.9 2.81 107 5.92 4.00 313.92 1.69 < MDL 20.21 < MDL 28.87 0.580 <MDL 168 <MDL 227 <MDL 208 7.6 360 219 0.5 1545 29.6 14.97 16.70 10.9%

2 26.61444 -97.78706 522 3.32 4.76 12.5 2.34 45 < MDL 3.59 27.70 8.22 8.44 14.45 < MDL 0.56 2.45 <MDL 345 <MDL 325 <MDL 1710 8.1 233 141 0.8 2285 30.6 23.73 21.30 10.8%

3 26.92382 -97.79244 425 3.11 4.38 8.56 0.79 34 < MDL 1.22 88.18 7.28 < MDL 8.61 < MDL 0.26 1.24 <MDL 260 <MDL 255 <MDL 294 7.9 221 134 0.6 1870 30.2 19.28 17.15 11.7%

4 26.62554 -97.86985 540 1.82 2.87 6.49 1.33 24 0.07 0.76 < MDL 11.72 12.05 14.93 < MDL 0.76 2.15 <MDL 468 <MDL 156 <MDL 180 8.3 374 226 2.3 2387 31.3 24.04 24.04 0.0%

5 26.95336 -97.84195 716 10.30 9.47 39.5 1.69 141 < MDL 50.05 1362.89 14.13 7.35 12.61 < MDL 0.33 1.36 <MDL 336 <MDL 936 <MDL 93 8.3 108 65 0.7 3303 33.8 34.25 31.21 9.3%

6 27.20687 -97.78480 280 7.67 9.94 21.6 2.53 85 7.79 2.65 < MDL 2.84 < MDL 13.61 < MDL 129.9 0.579 1.61 143 <MDL 151 <MDL 1700 7.7 295 179 0.5 1357 30.4 14.14 13.10 7.7%

7 27.06216 -97.88212 281 2.99 7.33 9.86 0.72 37 < MDL 1.02 < MDL 10.17 < MDL 3.02 < MDL 0.36 0.660 2.24 164 <MDL 127 <MDL 152 8.1 255 154 0.9 1299 29.7 13.15 12.41 5.8%

8 27.07502 -97.81909 319 5.03 7.79 24.0 3.85 81 < MDL 1.30 < MDL 21.63 < MDL 4.80 < MDL 1.06 0.978 3.02 244 0.633 175 <MDL 69 7.8 220 134 0.5 1616 29.7 15.69 14.97 4.7%

9 27.23247 -97.80215 372 10.4 9.82 36.1 3.26 133 0.51 6.13 22.73 3.61 6.19 23.20 < MDL 39.52 0.656 2.39 241 <MDL 324 <MDL 6680 7.7 231 141 0.4 1926 31.2 19.09 18.21 4.7%

10 27.22073 -97.79216 392 8.02 8.29 27.6 2.27 102 12.24 2.18 < MDL 8.63 22.90 17.59 < MDL 23.04 0.520 <MDL 247 1.76 337 <MDL 228 7.9 229 139 0.6 2101 30.5 19.30 18.58 3.8%

11 27.26441 -97.75673 385 9.82 8.63 42.0 2.72 145 < MDL 10.31 1543.78 4.22 5.75 23.08 < MDL 3.57 0.720 <MDL 241 <MDL 335 <MDL 3501 7.5 289 176 0.3 1972 27.9 19.93 19.59 1.7%

12 27.01698 -97.79378 324 2.53 4.72 8.85 1.87 32 < MDL 1.12 < MDL 10.25 5.42 4.42 < MDL 0.20 0.773 <MDL 239 <MDL 155 <MDL 760 8.3 227 137 1.4 1610 30.4 14.86 14.56 2.1%

13 26.61031 -97.76588 519 3.40 4.93 16.0 2.90 54 < MDL 1.80 33.24 3.50 4.94 9.18 < MDL 0.12 1.93 <MDL 390 <MDL 408 <MDL 835 8.3 188 113 1.2 2562 31.9 23.78 23.35 1.8%

14 27.26018 -97.80245 297 7.42 8.65 26.3 2.18 96 2.16 3.44 9.65 2.98 6.23 19.25 < MDL 47.46 0.634 <MDL 169 0.645 223 <MDL 362 7.7 281 171 0.4 1572 28.9 15.06 15.06 0.0%

15 27.21695 -97.69534 377 7.91 8.13 34.1 4.09 118 < MDL 4.13 < MDL 6.56 6.50 21.36 < MDL 0.34 0.581 <MDL 279 <MDL 294 <MDL 123 7.9 268 163 0.6 2012 30.9 18.96 19.37 2.1%

16 27.21515 -97.76961 287 5.88 9.96 20.6 2.22 76 16.61 2.25 < MDL 9.26 15.86 15.73 < MDL 95.68 0.516 <MDL 163 <MDL 175 <MDL 217 7.9 289 176 0.7 1479 27.7 14.25 14.04 1.5%

17 26.64690 -97.98510 473 4.41 3.63 13.0 1.93 51 < MDL 2.48 < MDL 12.36 11.40 15.36 < MDL 0.63 1.09 <MDL 490 <MDL 198 <MDL 124 8.2 197 119 1.0 2467 30.2 21.68 21.95 1.3%

18 26.63368 -97.68127 1369 53.5 13.6 198 9.96 714 < MDL 60.46 1228.22 4.97 < MDL 133.93 < MDL 0.47 1.11 <MDL 299 <MDL 2865 <MDL 152 8.1 87 53 0.4 6860 30.6 74.22 69.91 6.0%

19 27.23137 -97.79391 423 10.3 9.32 35.9 3.66 132 6.80 1.02 < MDL 7.46 15.46 19.00 < MDL 36.46 0.598 <MDL 321 1.34 396 <MDL 55 8.4 169 102 1.3 2337 20.3 21.28 20.70 2.7%

20 27.16066 -97.79455 310 4.23 7.40 16.3 1.89 58 < MDL 2.00 51.92 6.73 < MDL 20.86 < MDL 20.30 0.855 <MDL 207 <MDL 159 <MDL 178 8.0 269 163 0.8 1670 29.2 14.84 14.56 1.9%

21 27.26016 -97.78007 306 6.43 7.45 30.5 1.59 103 < MDL 3.06 3.41 7.99 < MDL 22.27 < MDL 28.98 0.690 <MDL 196 <MDL 234 <MDL 328 7.8 251 153 0.5 1748 29.1 15.55 15.46 0.6%

22 26.64687 -97.74464 626 12.9 8.96 56.0 3.60 193 < MDL 26.57 140.45 3.76 7.50 40.86 < MDL 0.15 1.56 <MDL 397 <MDL 832 <MDL 55 8.4 126 76 0.9 3465 29.5 31.32 31.11 0.7%

23 26.65027 -97.66633 691 24.1 9.05 69.8 2.99 273 < MDL 83.51 1385.78 4.00 7.55 36.28 < MDL < MDL 1.46 <MDL 434 <MDL 1069 <MDL 246 8.8 94 56 1.8 3885 28.4 35.80 36.45 1.8%

24 26.63992 -97.75612 530 10.7 7.71 42.3 2.19 150 < MDL 27.55 1082.22 7.39 8.99 32.28 < MDL 0.17 1.98 <MDL 380 <MDL 689 <MDL 154 8.5 154 93 1.4 3123 31.6 26.28 28.24 7.2%

25 26.97695 -97.77642 NM 3.145 NM 9.07 NM 36 NM 0.01 NM 0.01 < MDL 0.01 NM 0.92 NM NM 215 NM 187 NM < MDL NM 242 NM NM NM NM NM NM NM

26 27.04147 -97.77598 NM 140 NM 355.5 NM 1463 NM 0.22 NM 0.02 < MDL < MDL NM 3.10 NM NM 1750 NM 691 NM < MDL NM 337 NM NM NM NM NM NM NM

27 27.04458 -97.89624 NM 3.545 NM 19.65 NM 64 NM < MDL NM 0.01 < MDL < MDL NM < MDL NM NM 289 NM 212 NM < MDL NM 195 NM NM NM NM NM NM NM

28 26.97695 -97.77642 NM 2.435 NM 12.8 NM 42 NM < MDL NM <MDL < MDL 0.01 NM 0.35 NM NM 293 NM 238 NM < MDL NM 228 NM NM NM NM NM NM NM

29 26.96975 -97.71971 NM 8.425 NM 29.2 NM 108 NM < MDL NM 0.01 < MDL 0.01 NM < MDL NM NM 512 NM 325 NM < MDL NM 165 NM NM NM NM NM NM NM

30 27.0216 -97.71869 NM 1.12 NM 8.625 NM 26 NM < MDL NM 0.01 < MDL 0.01 NM < MDL NM NM 259 NM 124 NM < MDL NM 218 NM NM NM NM NM NM NM

31 26.99896 -97.75985 NM 5.39 NM 26.55 NM 88 NM 0.02 NM < MDL < MDL 0.01 NM < MDL NM NM 565 NM 112 NM < MDL NM 220 NM NM NM NM NM NM NM

32 26.95339 -97.84195 NM 8.745 NM 42.7 NM 143 NM 0.04 NM 0.01 < MDL 0.01 NM < MDL NM NM 335 NM 887 NM < MDL NM 112 NM NM NM NM NM NM NM

33 26.92385 -97.79262 NM 2.765 NM 11.35 NM 40 NM < MDL NM 0.01 < MDL 0.01 NM < MDL NM NM 281 NM 251 NM < MDL NM 215 NM NM NM NM NM NM NM

34 27.06213 -97.88202 NM 2.79 NM 12.45 NM 43 NM < MDL NM 0.01 < MDL < MDL NM 0.49 NM NM 157 NM 111 NM < MDL NM 246 NM NM NM NM NM NM NM

35 27.0749 -97.81918 NM 4.57 NM 30.8 NM 95.5 NM < MDL NM 0.02 < MDL < MDL NM 0.80 NM NM 246 NM 160 NM < MDL NM 208 NM NM NM NM NM NM NM

Collected Well Data

Raster Interpolation Maps

Figure 10. Molybdenum

concentrations

Figure 9. Selenium

concentrations

Figure 8. Magnesium

concentrations

Figure 1: (a) Boundaries of the Kenedy County Groundwater Conservations District,

and (b) location of wells with groundwater data currently in the USGS National

Uranium Resource Evaluation (NURE) database.