Carbon Dioxide Evasion in Tropical Alpine Streams

Carbon Dioxide Evasion in Tropical Alpine Streams

Import data

In this document we are going to calculate Evasion from the Vaisala Sensors and compare them to the eosFD flux measurements as well as see how they relate to other variables such as precipitation and temperature. First we import the data and for now we will filter so we are looking at non-injections

Create new time variables for ease of plotting

These new variables will help us plot each seperate day on a timescale of midnight -> midnight

df$day <- as.factor(substr(as.character(df$DateTime),1,10))
times <- substr(as.character(df$DateTime),12,16)
df$time <- strftime(df$DateTime, format="%H:%M")
df$time <- as.POSIXct(df$time, format="%H:%M")

todayStart <- as.POSIXct(paste0(Sys.Date(),"00:00:00"))
todayEnd <- as.POSIXct(paste0(Sys.Date(),"23:59:59"))

CO2 Change

Change in CO2

The first step in calculating flux from the stream is to calculate change in CO2 concentrations between two points within the stream. We will look at two pairs of sensors (1->3 & 3->4). Once we determine change in CO2 concentration, we will convert ppm to uMols and then account for stream metabolism (respiration and photosynthesis) to calculate flux. First, let’s visualize change in CO2 accross the pairs of sensors

So now that we know what the change in CO2 between stations, it’s time to account for stream metabolism. Stream metabolism includes Ecosystem Respiration (ER) and Gross Primary Production / phtosynthesis (GPP). Both of these processes include a 1:1 exchange of CO2 and DO molecules. Photosynthesis: Use CO2 and create O2 (1:1 ratio).

Respiration: Use O2, create CO2 (1:1 ratio).

Respiration can occur in the abscence of sunlight while photosynthesis cannot. At night, stream processes are respiration driven. During the day both respiration and photosynthesis occur. We can look at the changes in DO over the similar stretches of stream and time period. We did not have a DO sensor at station 3 but we did have one at station 2.

Dissolved Oxygen

Change in Dissolved Oxygen

Mass Conversion

Convert CO2 from concentration to mass

Now that we know the change in CO2 in terms of concentration [ppm], we can convert it to mass. Specifically, we will take this opportunity to convert to micromoles [umol], which we will eventually use to express evasion.

# Distances are 17,30,80

filt13$uMols_13 <- ((filt13$V1-filt13$V3)/ 37.6) *.0018*(1000000/44.01)*filt13$stn1_Q/1000 

filt34$uMols_34 <- ((filt34$V3-filt34$V4)/ 64) *.0018*(1000000/44.01)*filt34$stn3_Q/1000

Plotting data

Histograms of change in CO2

CO2 Change over time

This plot shows how