# Approach for Substituting Mingo IMPROVE Carbon Data

Inter

- RPO Data Analysis/Monitoring Workgroup

Chuck McDade & Warren White
UC Davis, 9/28/05

# What periods and modules exhibited compromised data at

Mingo?

• Mid 2002 through 4/13/05 (end will be confirmed after we have received April/May 2005 data)

• Apparently affects C module only (carbon), due to inlet blockage**Mingo Organic Carbon (OC)**

6000 8000 10000 12000 14000**O C** **2 4** **h a** **v e** **r a** **g e** **, n** **g /** **m 3** 



### Mingo organic carbon concentrations began diminishing during the third quarter of 2002 and remained low t hroughout the period of reported data. 0 2000 4000 6000

1/1/00 1/1/01 1/1/02 1/1/03 1/1/04**O C** **2 4** **h a** **v e** **r a** **g e** **, n** **g /** **m 3** 

# What data analysis approach might compensate for lost data?

• We propose extrapolating from measured years to lost years, using the hydrogen measurement from the A module to estimate carbon.

• The A module (mass and elements) was visibly clogged with mud, but the data through the period do not exhibit abnormalities. We consider the A module data to be valid.

# Determining Organic Mass from

Hydrogen

• We routinely estimate organics from hydrogen as one of our QC checks.

• We assume that:

– All sulfur is fully neutralized

– Hydrogen associated with nitrates and water volatilizes in
vacuum during the hydrogen analysis



# • We subtract 0.25*S from hydrogen, because 0.25 is the mass ratio of H to S in ammonium sulfate**Mingo SO4/S**

3 4 5 6SO4/SRatio



### Using hydrogen to substitute for carbon requires subtracting out the hydrogen associated w ith sulfur . 2001 is a good choice for a baseline period because the SO4/S ratio is relatively stable and is similar in behavior to the period after mid

- 2002, wh en we w ill be substituting. This plot also demonstrates that the A module did not suf fer inlet blockage. 0 1 2

1/1/00 1/1/01 1/1/02 1/1/03 1/1/04SO4/SRatio**Mingo OC v s. org_H, 2001 data only** 

y = 8.0247x
R 2 = 0.7935

4000 6000 8000 10000 12000**O C** **, n** **g /** **m 3** 



### During 2001, the ratio of OC to hydrogen associated w ith organics (org_H) is around 8. org_H equals measured hydrogen minus 0.25*S, wh ere 0.25 is the mass ratio of H to S in ammonium sulfate. So, w e can use 8*org_H as a surrogate for OC; w e wi ll call the surrogate OCH.

0 2000

0 200 400 600 800 1000 1200

**org_H, ng/m3 Mingo Measured OC & Surrogate OCH from Hy**  **drogen**

2000 4000 6000 8000 10000 12000 1400024haverage,ng/m3



### OCH mimics OC quite w ell up until mid

- 2002. OCH even succeeds in identifying the high concentration spikes in 2000 and 2001. OCH failed wi th negative values in July 2002 w hen the SO4/S ratio w as not w ell controlled (see slide 6), but seems reasonable during other periods. -4000 -2000 0

1/1/00 1/1/01 1/1/02 1/1/03 1/1/04

OC OCH**Mingo OCH/OC Ratio**

4 5 6 7 8 9 10 11 12 13 14 15 16**O C** **H /** **O C** **R a** **t i** **o**



### The OCH/OC ratio began to increase from 1 during August 2002, suggesting that inlet blockage began during that month. W e propose that substitution of OCH for OC begin in August 2002. -2 -1 0 1 2 3 4

1/1/00 1/1/01 1/1/02 1/1/03 1/1/04**Mingo OC and Substituted OCH beginning 8/1/02**

4000 6000 8000 10000 12000 1400024haverage,ng/m3



### This plot illustrates the data record that w e recommend for organic carbon, w ith measured OC used through July 2002 and OCH substituted beginning in August 2002.

0 2000

1/1/00 1/1/01 1/1/02 1/1/03 1/1/04

OC OCH**Mingo EC/OC Ratio**

0.3 0.4 0.5 0.6 0.7**E C** **/ O** **C R** **a t** **i o** 



### Now w e need to identify a substitute for elemental carbon (EC), w hich is also compromised by the inlet blockage. W e can estimate the EC/OC ratio using measured data for the period that w e consider valid, from 2000 through July 2002. 0 0.1 0.2

1/1/00 1/1/01 1/1/02 1/1/03 1/1/04**Mingo EC v s. OC, data through 7/02 only** 

y = 0.1921x
R 2 = 0.7101

1000 1500 2000 2500**E C** **, n** **g /** **m 3** 



### The EC/OC ratio through July 2002 is around 0.2. W e get this same ratio if w e use all data, through 2004. 0 500

0 2000 4000 6000 8000 10000 12000 14000

**OC, ng/m3 Mingo Measured EC & Surrogate 0.2xOCH from Hy**  **drogen**

0 500 1000 1500 2000 250024haverage,ng/m3



### Here w e take the next step and substitute 0.2*OCH for EC. As w ith OC, our substitution mimics EC quite w ell up until mid

- 2002, and even succeeds in identifying the high concentration spikes in 2000 and 2001. Again, w e recommend substituting beginning in August 2002. -1000 -500 0

1/1/00 1/1/01 1/1/02 1/1/03 1/1/04

### RMS **Precision**

**OC EC** 

Reported data vs. substituted data, 2001 21% 24%

One measure of the reliability of the substituted data is to compare its agreement w ith measured data (w hen both are available in 2001) against the precision determined from identical collocated samplers. The variability among reported versus substituted data is only slightly greater than that among identical collocated samplers.

Collocated IMPROVE samplers 13% 22%**Mingo EC & Substituted 0.2xOCH beginning 8/1/02**

1000 1500 2000 250024haverage,ng/m3



### This plot illustrates the data record that w e recommend for elemental carbon, w ith measured EC used through July 2002 and 0.2*OCH substituted beginning in August 2002. 0 500

1/1/00 1/1/01 1/1/02 1/1/03 1/1/04

EC OCHx0.2

# What caused the decrease in carbon concentrations?

• Blocked inlets were discovered at Swanquarter, NC, in March 2005, caked with mud from insects.

• Other sites were inspected, and blocked inlets were found at Mingo, replaced on 4/13/05.

• Blocked inlets were returned to UC Davis for inspection and testing.

# Blocked Inlet, Swanquarter, NC

# Inlet Tests at UC Davis

• Extremely blocked inlets (98 to 100% blocked) were compared against clean inlets and less blocked inlets in side

- by

- side tests in Davis.

• Tests revealed that an inlet must be >98% blocked (by visual inspection) to affect fine mass significantly.

• The Mingo A Module inlet showed substantial blockage in these tests, yet the 2002

- 2004 A module data do not appear to be unusual.

# Inlet Tests at UC Davis

2.0 2.5 3.0 3.5**M a** **s s** **C o** **n c** **e n** **t r** **a t** **i o** **n (** **g /** **m 3** **)**



### 98-100% cl ogged 85-95 % cl ogged



## 0.0 0.5 1.0 1.5

MI NG A MI NG C SW AN A MIN GB SW AN B SI KE B HE GL C Cl ea n Cl ea n Cl ea n Cl ea n Cl ea n**M a** **s s** **C o** **n c** **e n** **t r** **a t** **i o** **n (** 

# Why didn’t we see the problem

earlier?

• UCD’s historical data quality assurance approach examined each quarter of data separately. Subtle changes over time were not evident.

• New approach supplements existing checks by examining time series of concentrations and comparing current levels against those observed in prior years.

• Flowrates were normal; Mingo did not fail any of our standard quantitative tests.

# Old Approach: Time Series

**Su lf**  **ur**

5000 6000 Σ S3 Σ SO 4r

0 1000 2000 3000 4000 5000

12/2 12/14 12/26 1/7 1/19 1/31 2/12 2/24

## Su **lf ur** 

y = 1.03x - 173.31 R 2 

### = 0.92

4000 5000 6000 

# Old Approach: Regression

y = 0.95x R 2 

### = 0.92



## y **= 1.**  **04x -**  **190. 90** 
**R 2**  

## = **0 .9**  **7**

0 1000 2000 3000 4000

0 1000 2000 3000 4000 5000 6000 **S3 S** **O 4** **=**

# New Approach: Long

- Term Time Series

# How can we prevent recurrences?

• New inlet design, easier to clean and less likely to clog.

• Disassembly and cleaning at annual maintenance.

• Weekly inspection by site operators.

• Awareness of the problem when encountering unusual data.

# New Style Inlet