7 Regulatory Limits
We calculated regulatory limits based on freshwater quality standards listed from state and/or federal regulatory agencies. Some regulatory threshold values are static and do not depend on additional environmental parameters, while some threshold values depend on local conditions like hardness, temperature, or pH.
We discuss how various parameters are assessed against standards below.
7.1 Metals
7.1.1 Metals with Static Regulatory Threshold Values
The metals parameters in the downloadable table below have static thresholds assigned.
Static regulatory values are represented as solid horizontal lines in the chapters that follow. (to do: show graphic example of values above horizontal line here)
Show the code
# read in static reg values in wide format
<- read_xlsx("other/input/regulatory_limits/master_reg_limits.xlsx", sheet = "static_regulatory_values") %>%
static_metals_reg_vals filter(static_category == "static_metals",
%in% c("drinking_water","irrigation_water","stock_water")) %>%
standard_type remove_empty() %>%
select(parameter_baseline_name,standard_type,reg_value,reg_unit,agency,source) %>%
pivot_wider(names_from = standard_type, values_from = reg_value) %>%
rename(characteristic_name = parameter_baseline_name,
reg_agency = agency,
reg_agency_source = source)
# source formatted data
<- read.csv("other/output/analysis_format/baseline_export_format.csv")
dat
# join static regulatory values to parameter results, and identify when/where exceedences occur
<- left_join(dat,static_metals_reg_vals) %>%
static_metals_thresholds mutate(drinking_water_exceed = case_when(
>= result_measure_value ~ "Y")) |>
drinking_water mutate(stock_water_exceed = case_when(
>= result_measure_value ~ "Y")) |>
stock_water mutate(irrigation_water_exceed = case_when(
>= result_measure_value ~ "Y")) irrigation_water
7.1.2 Metals with Hardness-Dependent Regulatory Values
Some regulatory values for metals are not simple static values, and are instead hardness-dependent (i.e. toxicity depends on calcium (Ca) and magnesium (Mg) concentrations). The metals parameters in the downloadable table below have hardness-dependent thresholds assigned.
Show the code
# hardness-dependent criteria
# see page 29 of "Alaska Water Quality Criteria Manual for Toxic and other Deleterious Organic and Inorganic Substances" for parameters and formulas
# read in parameters which have hardness dependent criteria
<- read_excel("other/input/regulatory_limits/master_reg_limits.xlsx", skip = 1, sheet = "diss_metals_hard_parameters") %>%
diss_metals_hard_param remove_empty() %>%
select(-parameter_agency_name) %>%
filter(!is.na(characteristic_name),
!is.na(m_a))
# make downloadable list metals which have calculated parameters
<- "other/input/regulatory_limits/formatted_reg_vals/calculated_metals_list.csv"
dir write.csv(diss_metals_hard_param,dir, row.names = F)
embed_file(dir, text = "Download List of Metals with Hardness-Dependent Regulatory Threshold Values")
Hardness varies by site, by season, and with hydrologic conditions. We calculated hardness according to the following formula:
Hardness = 2.497(Total Calcium in mg/L) + 4.119(Total Magnesium in mg/L)
For sampling events with duplicate samples, we calculated average hardness. Note that some sampling events do not have calculated hardness values because total Ca and/or total Mg values were not available.