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Organic Carbon/Elemental Carbon Analyzer (OC/EC)

The OC/EC analyzer measures carbonaceous aerosol components using thermal and optical methods.

AeroViz.rawDataReader.script.OCEC.Reader 

Reader(path: Path | str, reset: bool | str = False, qc: bool | str = True, **kwargs)

Bases: AbstractReader

OC/EC (Organic Carbon/Elemental Carbon) Analyzer Data Reader

A specialized reader for OC/EC analyzer data files, which measure carbonaceous aerosol composition using thermal and optical methods.

See full documentation at docs/source/instruments/OCEC.md for detailed information on supported formats and QC procedures.

Attributes

nam class-attribute instance-attribute 

nam = 'OCEC'

OUTPUT_COLUMNS class-attribute instance-attribute 

OUTPUT_COLUMNS = ['Thermal_OC', 'Thermal_EC', 'Optical_OC', 'Optical_EC', 'TC', 'OC1', 'OC2', 'OC3', 'OC4', 'PC']

MIN_VALUE class-attribute instance-attribute 

MIN_VALUE = -5

MAX_VALUE class-attribute instance-attribute 

MAX_VALUE = 100

MDL class-attribute instance-attribute 

MDL = {'Thermal_OC': 0.3, 'Optical_OC': 0.3, 'Thermal_EC': 0.015, 'Optical_EC': 0.015}

Functions

_raw_reader 

_raw_reader(file)

Read and parse raw OC/EC data files.

Parameters:

Name Type Description Default
file Path or str

Path to the OC/EC data file.

 required

Returns:

Type Description
DataFrame

Processed OC/EC data with datetime index and carbon fraction columns.

_QC 

_QC(_df)

Perform quality control on OC/EC data.

QC Rules Applied
  1. Invalid Carbon : Carbon value outside valid range (-5-100 ugC/m3)
  2. Below MDL : Value below method detection limit
  3. Spike : Sudden value change (vectorized spike detection)
  4. Missing OC : Thermal_OC or Optical_OC is missing

Data Format

  • File format: CSV file
  • Sampling frequency: 1 hour
  • File naming pattern: *LCRes.csv
  • Data structure:
    • Header: 3 rows of metadata
    • Time column: Start Date/Time
    • Carbon fraction measurements
    • Sample volume information

Measurement Parameters

The OC/EC analyzer provides measurements of:

Parameter Unit Description
Thermal_OC μgC/m³ Thermal organic carbon
Thermal_EC μgC/m³ Thermal elemental carbon
Optical_OC μgC/m³ Optical organic carbon
Optical_EC μgC/m³ Optical elemental carbon
OC1-4 μgC/m³ Carbon fractions by temperature
PC μgC/m³ Pyrolyzed carbon
TC μgC/m³ Total carbon

Data Processing

Data Reading

  • Processes CSV files with varying header structures
  • Handles 12/24 hour time formats
  • Standardizes column names
  • Rounds timestamps to nearest hour
  • Converts raw measurements to concentration units

Quality Control

The OCEC reader uses the declarative QCFlagBuilder system with the following rules:

+-----------------------------------------------------------------------+
|                         QC Thresholds                                 |
+-----------------------------------------------------------------------+
| MIN_VALUE = -5       μgC/m³                                           |
| MAX_VALUE = 100      μgC/m³                                           |
| MDL (Minimum Detection Limits):                                       |
|   - Thermal_OC: 0.3 μgC/m³                                            |
|   - Optical_OC: 0.3 μgC/m³                                            |
|   - Thermal_EC: 0.015 μgC/m³                                          |
|   - Optical_EC: 0.015 μgC/m³                                          |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
|                            _QC() Pipeline                             |
+-----------------------------------------------------------------------+
|                                                                       |
|  +---------------------------+    +---------------------------+       |
|  | Rule: Invalid Carbon      |    | Rule: Below MDL           |       |
|  +---------------------------+    +---------------------------+       |
|  | Value <= -5 OR            |    | Value < MDL for           |       |
|  | Value > 100 μgC/m³        |    | respective column         |       |
|  +---------------------------+    +---------------------------+       |
|           |                                |                          |
|           v                                v                          |
|  +---------------------------+    +---------------------------+       |
|  | Rule: Spike               |    | Rule: Missing OC          |       |
|  +---------------------------+    +---------------------------+       |
|  | Sudden value change       |    | Thermal_OC is NaN         |       |
|  | (vectorized detection)    |    | (primary measurement)     |       |
|  +---------------------------+    +---------------------------+       |
|                                                                       |
+-----------------------------------------------------------------------+

QC Rules Applied

Rule Condition Description
Invalid Carbon Value ≤ -5 OR > 100 μgC/m³ Carbon value outside valid range
Below MDL Value < MDL Measurement below minimum detection limit
Spike Sudden value change Unreasonable sudden change detected
Missing OC Thermal_OC or Optical_OC is NaN Primary OC measurement is missing

Minimum Detection Limits

Parameter MDL (μgC/m³)
Thermal_OC 0.3
Optical_OC 0.3
Thermal_EC 0.015
Optical_EC 0.015

Output Data

The processed data contains:

Column Unit Description
Thermal_OC μgC/m³ Thermal organic carbon
Thermal_EC μgC/m³ Thermal elemental carbon
Optical_OC μgC/m³ Optical organic carbon
Optical_EC μgC/m³ Optical elemental carbon
TC μgC/m³ Total carbon

QC_Flag Handling

  • The intermediate file (_read_ocec_qc.pkl/csv) contains the QC_Flag column
  • The final output has invalid data set to NaN and QC_Flag column removed

Notes

  • Provides critical information about combustion sources
  • Helps identify secondary organic aerosol formation
  • Combines thermal and optical analysis methods
  • Standardizes output across different instrument formats