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Table 1.  Selected properties and constituents, Lorence Creek and Frio River tributary sites

[mg/L, milligrams per liter; --, no standard; μS/cm, microsiemens per centimeter at 25 degrees Celsius; <, less than; mg/L, micrograms per liter; ND, not detected; NA, not analyzed ]

Property or constituent

No. of detections at Lorence Creek site

Minimum concentration at Lorence Creek site

Maximum concentration at Lorence Creek site

Average concentration at Lorence Creek site Concentration at Frio River tributary site

Drinking water maximum allowable or recommended concentrations1

pH, lab (standard units) 8

7.3   

8.3      

7.8    

8        

6.5-8.5
Alkalinity, lab (mg/L) 8

31      

76         

50       

70        

--
Specific conductance, lab (mS/cm) 8

64      

100         

84       

113        

--
Suspended sediment (mg/L) 6

12       

437         

104       

200        

--
   

 

 

 

 

 
Nitrogen, ammonia, dissolved (mg/L) 8

.04  

.12    

.08   

<.02   

--
Nitrogen, ammonia plus organic, dissolved (mg/L) 8

.2    

.6      

.35   

.28   

--
Nitrogen, ammonia plus organic, total (mg/L) 8

.24  

2         

.71   

1.1   

--
Nitrogen, nitrite, dissolved (mg/L) 8

.01  

.05    

.02   

<.01   

1   

Nitrogen, nitrite plus nitrate, dissolved (mg/L) 8

.19  

.74    

.36   

.3     

10   

Phosphorus, dissolved (mg/L) 8

.05  

.15    

.09   

.06    

--
Phosphorus, total (mg/L) 8

.08  

.37    

.14   

.23    

--
Phosphorus, orthophosphate, dissolved (mg/L) 8

.05  

.17    

.1     

.06    

--
   

 

 

 

 

 
Calcium, dissolved (mg/L) 8

7.7    

15         

12        

19        

--
Magnesium, dissolved (mg/L) 8

.27   

.59    

.46    

.88   

--
Sodium, dissolved (mg/L) 8

.48   

1.3      

.92    

.64   

--
Potassium, dissolved (mg/L) 8

1.3     

3.8      

2.1      

5        

--
Chloride, dissolved (mg/L) 8

.82    

2.5      

1.4      

.95   

250   

Sulfate, dissolved (mg/L) 8

.67    

3.9      

2.5      

1.2     

250   

Fluoride, dissolved (mg/L) 0

<.10    

<.10     

<.10    

<.10   

2    

Silica, dissolved (mg/L) 8

1.3      

6.2       

2.5      

8.8     

--
   

 

 

 

 

 
Aluminum, dissolved (mg/L) 8

12         

39          

21         

8.8     

250-200
Antimony, dissolved (mg/L) 0

<1.0      

<1.0       

<1.0      

<1.0     

6   

Arsenic, dissolved (mg/L) 1

<1.0      

1          

1         

<1.0     

50   

Barium, dissolved (mg/L) 8

3.6      

7.4       

5.8      

9.6     

2,000   

Beryllium, dissolved (mg/L) 0

<1.0      

<1.0       

<1.0      

<1.0     

4    

Cadmium, dissolved (mg/L) 0

<1.0      

<1.0       

<1.0      

<1.0     

5    

Chromium, dissolved (mg/L) 2

<1.0      

1.5       

1.4      

<1.0     

100    

Cobalt, dissolved (mg/L) 0

<1.0      

<1.0       

<1.0      

<1.0     

--
Copper, dissolved (mg/L) 8

1         

4.3       

2.3       

1.1     

1,000   

Iron, dissolved (mg/L) 8

5         

15          

9.9       

8.8     

300   

Lead, dissolved (mg/L) 0

<1.0      

<1.0       

<1.0       

<1.0     

15   

Manganese, dissolved (mg/L) 8

1         

4.7       

2.1       

1        

50   

Molybdenum, dissolved (mg/L) 0

<1.0      

<1.0       

<1.0       

<1.0     

--
Nickel, dissolved (mg/L) 0

<1.0      

<1.0       

<1.0       

<1.0     

--
Selenium, dissolved (mg/L) 0

<1.0      

<1.0       

<1.0       

<1.0     

50   

Silver, dissolved (mg/L) 0

<1.0      

<1.0       

<1.0       

<1.0     

100   

Zinc, dissolved (mg/L) 8

3         

7.4       

5          

5.2     

5,000   

   

 

 

 

 

 

Alachlor (mg/L) 1

.011   

.011   

.011   

ND

2   

Atrazine (mg/L) 8

.01     

.24     

.09     

.007

3   

Azinphos-methyl (mg/L) 1

.042   

.042   

.042   

.054

--
Benfluralin (mg/L) 1

.0042

.0042

.0042

ND

--
Carbaryl (mg/L) 4

.044   

.19     

.1       

ND

--
Chlorpyrifos (mg/L) 6

.008   

.023   

.013   

ND

--
DCPA (mg/L) 3

.0009

.01     

.0043

ND

--
DDE (mg/L) 2

.0024

.0032

.0028

ND

--
Deethylatrazine (mg/L) 6

.0028

.029   

.0081

.001

--
Diazinon (mg/L) 7

.03     

.53     

.17     

ND

--
DNOC (mg/L) 1

.13     

.13     

.13     

ND

--
Malathion (mg/L) 3

.006   

.059   

.026   

ND

--
MCPA (mg/L) 2

.16     

.24     

.2       

ND

--
Metolachlor (mg/L) 2

.006   

.012   

.009   

ND

--
Metribuzin (mg/L) 1

.014   

.014   

.014   

ND

--
Prometon (mg/L) 2

.0045

.0069

.0057

ND

--
Propargite (mg/L) 1

.03     

.03     

.03     

ND

--
Simazine (μg/L) 4

.008   

.19     

.06     

ND

--
Trifluralin (mg/L) 1

.0042

.0042

.0042

ND

--
   

 

 

 

 

 
1,2,4-Trimethylbenzene (mg/L) 2

.018  

.023   

.025   

NA

--
Acetone (mg/L) 1

5.3       

5.3       

5.3       

NA

--
Benzene (mg/L) 1

.015   

.015   

.015   

NA

5   

Ethylbenzene (mg/L) 1

.01     

.01     

.01     

NA

700   

Methyl isobutyl ketone (mg/L) 1

.23     

.23     

.23     

NA

--
Xylenes (mg/L) 1

.013   

.013   

.013   

NA

10,000   

1 U.S. Environmental Protection Agency, 1999b.

2 50 mg/L is the recommended standard; 200 mg/L is an acceptable standard.

 

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