Atmospheric Deposition (AD) • tbeploads

library(tbeploads)

Loading from atmospheric deposition (AD) for bay segments in the Tampa Bay watershed are calculated using rainfall data from weather stations in the watershed and atmospheric concentration data from the Verna Wellfield site. Rainfall data must be obtained using the util_getrain() function before calculating loads. For convenience, daily rainfall data from 2017 to 2023 at sites in the watershed are included with the package in the rain object.

head(rain)
#> # A tibble: 6 × 6
#>   station date        Year Month   Day rainfall
#>     <dbl> <date>     <int> <dbl> <int>    <dbl>
#> 1     228 2017-01-01  2017     1     1     0   
#> 2     228 2017-01-02  2017     1     2     0   
#> 3     228 2017-01-03  2017     1     3     0   
#> 4     228 2017-01-04  2017     1     4     0   
#> 5     228 2017-01-05  2017     1     5     0.02
#> 6     228 2017-01-06  2017     1     6     0

The Verna Wellfield data must also be obtained from https://nadp.slh.wisc.edu/sites/ntn-FL41/ as monthly observations. This file is also included with the package and can be found using system.file() as follows:

vernafl <- system.file('extdata/verna-raw.csv', package = 'tbeploads')
vernafl
#> [1] "/home/runner/work/_temp/Library/tbeploads/extdata/verna-raw.csv"

During load calculation, the Verna data are converted to total nitrogen and total phosphorus from ammonium and nitrate concentration data using the util_prepverna() function. Total nitrogen and phosphorus concentrations are estimated from ammonium and nitrate concentrations (mg/L) using the following relationships:

$TN = NH_4^+ * 0.78 + NO_3^- * 0.23$

$TP = 0.01262 * TN + 0.00110$

The first equation corrects for the % of ions in ammonium and nitrate that are N, and the second is a regression relationship between TBADS TN and TP, applied to Verna.

AD loads are estimated using the anlz_ad() function, where total hydrologic load by bay segment is calculated from the rain data and total nitrogen and phosphorus load is calculated by multiplying hydrologic load by the atmospheric deposition concentrations from the Verna data. Total hydrologic load for each bay segment is calculated using daily estimates of rainfall at NWIS NCDC sites in the watershed. This is done as a weighted mean of rainfall at the measured sites relative to grid locations in each bay segment. The weights are based on distance of the grid cells from the closest site as inverse distance squared. Total hydrologic load for a sub-watershed is then estimated by converting inches/month to m3/month using the area of each bay segment. The distance data and bay segment areas are contained in the file included with the package.

head(ad_distance)
#>   segment    seg_x   seg_y matchsit  distance     invdist2     area
#> 1       1 344902.2 3080488      520 26000.117 1.479277e-09 23407.05
#> 2       1 344902.2 3080488      940 39711.285 6.341210e-10 23407.05
#> 3       1 344902.2 3080488      945 44691.735 5.006631e-10 23407.05
#> 4       1 344902.2 3080488     1632 22105.640 2.046416e-09 23407.05
#> 5       1 344902.2 3080488     2806  8649.245 1.336730e-08 23407.05
#> 6       1 344902.2 3080488     3986 47920.032 4.354776e-10 23407.05

The total nitrogen and phosphorus loads are then estimated for each bay segment by multiplying the total hydrologic load by the total nitrogen and phosphorus concentrations in the Verna data. The loading calculations also include a wet/dry deposition conversion factor to account for differences in loading during the rainy and dry seasons.

Using anlz_ad() to estimate AD load is done as follows, where rain is the rain data and vernafl is the path to the Verna Wellfield data.

anlz_ad(rain, vernafl)
#> # A tibble: 672 × 7
#>     Year Month source segment        tn_load tp_load hy_load
#>    <int> <dbl> <chr>  <chr>            <dbl>   <dbl>   <dbl>
#>  1  2017     1 AD     Boca Ciega Bay   0.721  0.0140    1.98
#>  2  2017     2 AD     Boca Ciega Bay   0.945  0.0168    1.95
#>  3  2017     3 AD     Boca Ciega Bay   0.950  0.0181    2.48
#>  4  2017     4 AD     Boca Ciega Bay   3.05   0.0482    3.90
#>  5  2017     5 AD     Boca Ciega Bay   9.06   0.131     6.89
#>  6  2017     6 AD     Boca Ciega Bay   9.67   0.178    22.5 
#>  7  2017     7 AD     Boca Ciega Bay  10.8    0.189    26.2 
#>  8  2017     8 AD     Boca Ciega Bay   5.58   0.120    24.6 
#>  9  2017     9 AD     Boca Ciega Bay   2.14   0.0553   14.1 
#> 10  2017    10 AD     Boca Ciega Bay   2.03   0.0368    5.56
#> # ℹ 662 more rows

Results can be summarized by segment, baywide, monthly, or annually using the summ and summtime arguments. By default, loads are returned monthly for each segment. Note that Boca Ciega Bay and Boca Ciega Bay South results are returned separately. Only Boca Ciega Bay South is used when estimating total bay loads.