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Concentrations and annual fluxes for selected water-quality constituents from the USGS National Stream Water Quality Accounting Network (NASQAN)

By Valerie J. Kelly, Richard P. Hooper, Brent T. Aulenbach, and Mary Janet

Summary Statistics--Mississippi Basin, Water Years 1996-2000

Lower Atchafalaya River at Melville, Louisiana (07381495)

Daily Mean Streamflow

Units                               N             Min     5th       25th     Median    75th      95th      Max

Cubic feet per second             1,827        55,000    72,000   118,000   193,000   312,000   436,000   637,000
Cubic meters per second           1,827         1,557     2,039     3,341     5,465     8,835    12,346    18,038

Field Parameters, Turbidity, and Suspended Sediment

Units in milligrams per liter, except where noted

Parameter                             N               Min      5th     25th    Median     75th     95th     Max

00010 Temperature (C)                74                 3.5     7.5     13.0      19.3     27.5     30.5     32.5
00076 Turbidity (NTU)                73                 5.8    13.0     30.0      45.0     65.0    120.0    260.0
00095 Conductance (uS/cm)            73               176.0   248.0    315.0     363.0    453.0    553.0    669.0
00300 Dissolved oxygen               74                 5.7     6.1      7.1       7.9      9.7     11.5     13.0
00400 pH (standard units)            75                 7.2     7.2      7.6       7.8      8.0      8.2      8.3
00452 CO3 (filtered)                 52                 0.0     0.0      0.0       0.0      0.0      0.0      0.0
00453 HCO3 (filtered)                54                48.0    67.0     89.0     109.5    133.0    168.0    174.0
39086 Alk (filtered, as CaCO3)       56                40.0    55.0     73.0      91.5    110.5    138.0    143.0
70331 % finer than 62 microns        71                35.8    45.0     73.0      93.0     97.6     99.2     99.8
80154 Suspended sediment             71                18.0    24.0     81.0     157.0    245.0    381.0    420.0

Nutrients and Organic Carbon, dissolved (filtered at 0.45 microns) and whole-water (unfiltered)

Units in milligrams per liter

Note: because of changes in reporting levels (RL), all censored data in this summary are converted to the highest RL reported for this station

                                          Percent
Parameter                       RL  N    Detections    Min      5th      25th    Median    75th     95th     Max

00608 NH3-N                   .020  74       59      < 0.020  < 0.020  < 0.020    0.022    0.034    0.066    0.370
00613 NO2-N                   .010  74       51      < 0.010  < 0.010  < 0.010    0.010    0.018    0.028    0.030
00623 Org+NH3-N (filtered)    .200  72       90      < 0.200  < 0.200    0.244    0.297    0.325    0.420    0.487
00625 Org+NH3-N (whole-water) .200  73       99      < 0.200    0.299    0.472    0.562    0.686    0.820    0.895
00631 NO2+NO3-N               .050  73      100        0.328    0.577    0.751    1.030    1.470    2.237    2.623
00665 Total P (whole-water)   .010  73      100        0.058    0.080    0.134    0.169    0.240    0.300    0.326
00666 Total P (filtered)      .020  73       97      < 0.020    0.022    0.043    0.060    0.072    0.106    0.122
00671 PO4-P                   .010  70      100        0.001    0.030    0.041    0.056    0.075    0.100    0.113
00681 DOC                     .300  67      100        2.200    3.400    3.900    4.400    5.100    6.993    8.813
00689 SOC                     .200  70      100        0.300    0.600    1.100    1.739    2.400    4.400    6.200

Major Ions, dissolved (filtered at 0.45 microns)

Units in milligrams per liter, except where noted

                                          Percent
Parameter                       RL  N    Detections    Min      5th      25th    Median    75th     95th     Max

00915 Calcium                 .020  74      100        14.61    21.58    27.73    34.57    40.00    46.37    49.19
00925 Magnesium               .010  73      100        4.392    6.499    7.980    10.82    13.00    16.45    18.00
00930 Sodium                  .200  74      100        11.00    12.00    15.41    19.64    27.00    39.39    44.28
00935 Potassium               .010  74      100        2.170    2.410    2.710    3.185    3.510    3.900    4.160
00940 Chloride                .010  72      100        12.42    14.00    18.19    22.48    29.60    38.53    49.87
00945 Sulfate                 .010  71      100        19.68    24.79    34.00    42.97    57.23    77.00    94.17
00950 Fluoride                .100  72       92      < 0.100  < 0.100    0.122    0.165    0.200    0.242    0.300
00955 Silica                  .010  74      100        1.263    4.291    5.700    6.164    6.787    7.805    8.787

Trace Elements, dissolved (filtered at 0.45 microns)

Units in micrograms per liter

Note: because of changes in reporting levels (RL), all censored data in this summary are converted to the highest RL reported for this station

                                          Percent
Parameter                       RL  N    Detections    Min      5th      25th    Median    75th     95th     Max

01000 Arsenic                  2.0  75       64      <   2.0  <   2.0  <   2.0      1.2      2.0      2.1      2.9
01005 Barium                   0.2  50       98      <   0.2     43.8     51.5     58.7     67.2     77.0     83.7
01010 Beryllium               10.0  54        0      <  10.0  <  10.0  <  10.0  <  10.0  <  10.0  <  10.0  <  10.0
01020 Boron                   16.0  70      100         20.6     25.8     33.2     40.1     54.2     71.6    118.8
01025 Cadmium                  1.0  54        0      <   1.0  <   1.0  <   1.0  <   1.0  <   1.0  <   1.0  <   1.0
01030 Chromium                 1.0  49       41      <   1.0  <   1.0  <   1.0  <   1.0      1.4      2.8      3.8
01035 Cobalt                   3.0  50        0      <   3.0  <   3.0  <   3.0  <   3.0  <   3.0  <   3.0  <   3.0
01040 Copper                   1.0  54       94      <   1.0  <   1.0      1.6      1.8      2.0      3.0      5.0
01046 Iron                    10.0  74       66      <  10.0  <  10.0  <  10.0     11.1     32.1     67.5    124.2
01049 Lead                     1.0  54        0      <   1.0  <   1.0  <   1.0  <   1.0  <   1.0  <   1.0  <   1.0
01056 Manganese                1.0  49       63      <   1.0  <   1.0  <   1.0      1.2      4.3     18.8     76.0
01060 Molybdenum              10.0  50       72      <  10.0  <  10.0  <  10.0      1.4      2.0      3.1     10.0
01065 Nickel                   1.0  54       93      <   1.0  <   1.0      1.4      1.6      2.0      3.0      4.0
01075 Silver                   1.0  50        0      <   1.0  <   1.0  <   1.0  <   1.0  <   1.0  <   1.0  <   1.0
01080 Strontium                0.5  71      100         98.4    122.8    148.2    175.9    220.0    280.6    292.2
01085 Vanadium                10.0  75        4      <  10.0  <  10.0  <  10.0  <  10.0  <  10.0  <  10.0     10.0
01090 Zinc                    10.0  54       76      <  10.0  <  10.0      1.0      1.7      3.8     10.6     13.0
01095 Antimony                 1.0  49        0      <   1.0  <   1.0  <   1.0  <   1.0  <   1.0  <   1.0  <   1.0
01106 Aluminum                 0.3  49       98      <   0.3      2.0      3.0      4.0      6.1     20.0     42.7
01130 Lithium                  6.0  71       85      <   6.0  <   6.0      5.0      5.6      8.1     13.7     17.0
01145 Selenium                 2.4  75        8      <   2.4  <   2.4  <   2.4  <   2.4  <   2.4      2.4      2.4
22703 Uranium                  1.0  49       47      <   1.0  <   1.0  <   1.0  <   1.0      1.2      2.0      2.0

Pesticides, dissolved (filtered at 0.7 microns)

Units in micrograms per liter, except where noted

Note: concentrations sometimes are estimated below the reporting level (RL); in this summary, all censored and estimated concentrations are converted to highest RL reported for this station; the percent detections described in the table include estimated concentrations, when appropriate

                                          Percent
Parameter                       RL  N    Detections    Min      5th      25th    Median    75th     95th     Max

04024 Propachlor              .050  73        1      < 0.050  < 0.050  < 0.050  < 0.050  < 0.050  < 0.050    0.050
04028 Butylate                .050  73        4      < 0.050  < 0.050  < 0.050  < 0.050  < 0.050  < 0.050    0.050
04035 Simazine                .010  74       99      < 0.010    0.012    0.016    0.027    0.057    0.191    0.248
04037 Prometon                .050  74       76      < 0.050  < 0.050    0.007    0.010    0.017    0.050    0.050
04040 Desethyl atrazine       .050  74       99      < 0.050    0.011    0.020    0.042    0.079    0.193    0.425
04041 Cyanazine               .200  74       95      < 0.200  < 0.200    0.018    0.038    0.107    0.462    0.940
04095 Fonofos                 .003  70        0      < 0.003  < 0.003  < 0.003  < 0.003  < 0.003  < 0.003  < 0.003
34253 alpha-HCH               .002  70        0      < 0.002  < 0.002  < 0.002  < 0.002  < 0.002  < 0.002  < 0.002
34653 p,p DDE                 .006  70        4      < 0.006  < 0.006  < 0.006  < 0.006  < 0.006  < 0.006    0.006
38933 Chlorpyrifos            .004  70        9      < 0.004  < 0.004  < 0.004  < 0.004  < 0.004    0.008    0.010
39341 gamma-HCH               .004  70        0      < 0.004  < 0.004  < 0.004  < 0.004  < 0.004  < 0.004  < 0.004
39381 Dieldrin                .001  70        4      < 0.001  < 0.001  < 0.001  < 0.001  < 0.001  < 0.001    0.010
39415 Metolachlor             .050  74       99      < 0.050    0.027    0.046    0.157    0.427    1.200    1.950
39532 Malathion               .010  70       19      < 0.010  < 0.010  < 0.010  < 0.010  < 0.010    0.014    0.037
39542 Parathion               .004  70        0      < 0.004  < 0.004  < 0.004  < 0.004  < 0.004  < 0.004  < 0.004
39572 Diazinon                .002  70       49      < 0.002  < 0.002  < 0.002  < 0.002    0.005    0.008    0.024
39632 Atrazine                .001  74      100        0.032    0.058    0.117    0.329    1.040    2.130    4.100
46342 Alachlor                .050  74       69      < 0.050  < 0.050  < 0.050    0.010    0.027    0.052    0.104
49260 Acetochlor              .050  73       68      < 0.050  < 0.050  < 0.050    0.015    0.059    0.317    0.500
82630 Metribuzin              .050  74       43      < 0.050  < 0.050  < 0.050  < 0.050    0.020    0.050    0.073
82660 Diethylanaline          .003  70        0      < 0.003  < 0.003  < 0.003  < 0.003  < 0.003  < 0.003  < 0.003
82661 Trifluralin             .002  70       30      < 0.002  < 0.002  < 0.002  < 0.002    0.002    0.005    0.014
82663 Ethalfluralin           .004  70        0      < 0.004  < 0.004  < 0.004  < 0.004  < 0.004  < 0.004  < 0.004
82664 Phorate                 .002  70        0      < 0.002  < 0.002  < 0.002  < 0.002  < 0.002  < 0.002  < 0.002
82665 Terbacil                .007  70        0      < 0.007  < 0.007  < 0.007  < 0.007  < 0.007  < 0.007  < 0.007
82666 Linuron                 .002  70        3      < 0.002  < 0.002  < 0.002  < 0.002  < 0.002  < 0.002    0.005
82667 Methyl parathion        .006  70        4      < 0.006  < 0.006  < 0.006  < 0.006  < 0.006  < 0.006    0.006
82668 EPTC                    .002  70        4      < 0.002  < 0.002  < 0.002  < 0.002  < 0.002  < 0.002    0.006
82669 Pebulate                .004  70        0      < 0.004  < 0.004  < 0.004  < 0.004  < 0.004  < 0.004  < 0.004
82670 Tebuthiuron             .020  70       84      < 0.020  < 0.020    0.009    0.010    0.012    0.018    0.020
82671 Molinate                .004  70       30      < 0.004  < 0.004  < 0.004  < 0.004    0.005    0.054    0.109
82672 Ethoprop                .003  70        0      < 0.003  < 0.003  < 0.003  < 0.003  < 0.003  < 0.003  < 0.003
82673 Benfluralin             .002  70        1      < 0.002  < 0.002  < 0.002  < 0.002  < 0.002  < 0.002    0.004
82674 Carbofuran              .020  70       36      < 0.020  < 0.020  < 0.020  < 0.020    0.009    0.036    0.055
82675 Terbufos                .013  70        0      < 0.013  < 0.013  < 0.013  < 0.013  < 0.013  < 0.013  < 0.013
82676 Pronamide               .003  70        0      < 0.003  < 0.003  < 0.003  < 0.003  < 0.003  < 0.003  < 0.003
82677 Disulfoton              .017  70        0      < 0.017  < 0.017  < 0.017  < 0.017  < 0.017  < 0.017  < 0.017
82678 Triallate               .001  70        0      < 0.001  < 0.001  < 0.001  < 0.001  < 0.001  < 0.001  < 0.001
82679 Propanil                .004  70        3      < 0.004  < 0.004  < 0.004  < 0.004  < 0.004  < 0.004    0.009
82680 Carbaryl                .003  70        7      < 0.003  < 0.003  < 0.003  < 0.003  < 0.003    0.005    0.049
82681 Thiobencarb             .002  70        4      < 0.002  < 0.002  < 0.002  < 0.002  < 0.002  < 0.002    0.008
82682 Dachthal (DCPA)         .002  69        1      < 0.002  < 0.002  < 0.002  < 0.002  < 0.002  < 0.002    0.002
82683 Pendimethalin           .008  70       10      < 0.008  < 0.008  < 0.008  < 0.008  < 0.008    0.008    0.011
82684 Napropamide             .003  70        0      < 0.003  < 0.003  < 0.003  < 0.003  < 0.003  < 0.003  < 0.003
82685 Propargite              .013  69        0      < 0.013  < 0.013  < 0.013  < 0.013  < 0.013  < 0.013  < 0.013
82686 Azinphos methyl         .001  70        0      < 0.001  < 0.001  < 0.001  < 0.001  < 0.001  < 0.001  < 0.001
82687 Permethrin              .005  70        0      < 0.005  < 0.005  < 0.005  < 0.005  < 0.005  < 0.005  < 0.005
91063 Diazinon-d10 (%)        .100  70      100        71.50    80.19    90.99    101.0    108.0    116.4    120.0
91064 Terbuthylazin (%)       .100  51      100        91.90    94.19    104.3    108.8    117.2    129.6    140.0
91065 HCH alpha-D6 (%)        .100  70      100        70.20    82.52    92.08    97.06    101.6    112.0    119.1

Suspended Sediment Chemistry

Units in parts per million (ppm) or parts per hundred (%)

Values censored higher than the reporting level (RL) indicate samples with insufficient sediment mass to quantify concentration above the RL

                                          Percent
Parameter                    RL       N  Detections    Min      5th      25th    Median    75th     95th     Max

29816 Antimony (ppm)        0.10     50     100       0.50     0.60     0.80     1.00      1.50     7.20     27.30
29818 Arsenic (ppm)         0.10     50     100       5.30     6.40     8.40    10.95     12.30    15.70     16.00
29820 Barium (ppm)          1.00     50     100      270.0    480.0    530.0    570.0     610.0    630.0     640.0
29822 Beryllium (ppm)       0.10     50     100       1.00     1.10     1.50     1.60      1.70     2.00      2.10
29826 Cadmium (ppm)         0.10     50      94    <  0.10  <  0.10     0.30     0.40      0.50     1.00      1.30
29829 Chromium (ppm)        1.00     50      98    <  1.00    45.00    57.00    63.50     69.00    78.00     260.0
29832 Copper (ppm)          1.00     50     100       9.00    12.00    16.00    22.00     25.00    32.00     38.00
29836 Lead (ppm)            1.00     50     100      11.00    17.00    20.00    22.50     26.00    45.00     74.00
29839 Manganese (ppm)       10.0     50     100      380.0    530.0    860.0     1100      1600     2200      3100
29841 Mercury (ppm)         0.01     47      94    <  0.01  <  0.01     0.03     0.05      0.06     0.12      1.10
29843 Molybdenum (ppm)      5.00     50       6    <  2.00  <  5.00  <  5.00  <  5.00   < 25.00    25.00     25.00
29845 Nickel (ppm)          1.00     50      98    <  1.00    26.00    34.00    37.00     43.00    59.00     68.00
29847 Selenium (ppm)        0.10     50     100       0.20     0.30     0.40     0.65      0.80     1.40      1.60
29850 Silver (ppm)          0.50     50       2    <  0.50  <  0.50  <  0.50  <  0.50   <  2.50  <  2.50      2.50
29853 Vanadium (ppm)        1.00     50     100      43.00    56.00    74.00    88.00     100.0    110.0     120.0
29855 Zinc (ppm)            1.00     50     100      50.00    70.00    90.00    110.0     130.0    160.0     210.0
30221 Aluminum (%)          0.10     50     100       4.00     4.60     5.40     6.00      6.40     7.10      7.50
30244 Total carbon (%)      0.10     49      98    <  0.10     0.80     1.20     1.90      2.30     3.30      4.00
30269 Iron (%)              0.10     50     100       1.50     2.00     2.50     2.95      3.30     3.70      3.90
30292 Phosphorus (%)        0.01     50     100       0.05     0.05     0.08     0.10      0.12     0.14      0.14
30308 Sulfur (%)            0.10     45      89    <  0.10  <  0.10     0.10     0.20      0.50     1.20      1.40
30317 Titanium (%)          0.01     50     100       0.20     0.20     0.30     0.31      0.38     0.40      0.40
35031 Cobalt (ppm)          1.00     50     100       7.00     8.00    11.00    13.00     14.00    15.00     16.00
35040 Strontium (ppm)       0.01     50     100      110.0    110.0    130.0    140.0     160.0    290.0     350.0
35046 Uranium (ppm)         50.0     50       0    < 50.00  < 50.00  < 50.00  < 50.00   < 250.0  < 250.0   < 250.0
35050 Lithium (ppm)         1.00     50     100      19.00    23.00    33.00    38.50     42.00    47.00     48.00
49955 Thallium (ppm)        50.0     50       0    < 50.00  < 50.00  < 50.00  < 50.00   < 250.0  < 250.0   < 250.0
50279 Sediment (mg/L)       1.00     50     100      18.00    26.00    73.00    159.5     243.0    398.0     455.0
50465 Organic carbon (%)    0.10     46      96    <  0.10     0.10     1.10     1.40      1.90     2.20      3.10

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