Random Sampling
North Carolina Random Ambient Monitoring System
Scale 1:100,000
Results for 2007-2010
Two Types of Monitoring: 1. Physical/Chemical Meters (dissolved oxygen, pH …) Water samples (turbidity, bacteria …)
2.
Biological Benthic Macroinvertebrates Fish Community Fish Tissue Phytoplankton
Two Approaches to Monitoring: 1. Targeted Ambient Monitoring System (AMS) Coalition Monitoring, Biological What are the conditions at a location…?
2.
Random, Statistical, Probabilistic What are the characteristics of a large group?
Targeted Monitoring Sites selected for reasons (AMS, Coalition,
Biological): o Upstream/downstream of a discharger o Water supply o Watershed – long term trends
Hundreds of sites monitored, but a limited
number of parameters sampled
Random Monitoring Sites chosen randomly (e.g. RAMS) Assess a “population” Infer characteristics of the population from the
sample Make statistical statements about a population For RAMS there are 60 sites monitored and hundreds of parameters sampled
RAMS Population = All freshwater streams on the 1:100,000 map
States shall assess “All waters”
Random Selection Each sampling unit of the population has an
equal chance of being selected.
Why 60 Sites? Precision (margin of error) is dependent on: o Number of sites sampled (sample size) o The proportion (e.g. % results > standard)
Proportion 20 %
25 ± 13 %
Sample Size 50 100 ±9% ±7%
50 %
± 17 %
± 12 %
Precision (±)
±8%
400 ±3% ±4%
USEPA http://www.epa.gov/nheerl/arm/surdesignfaqs.htm#samplesize50
RAMS Monitoring (60 sites) • • • • •
29 sites during 2007-2008 31 sites during 2009-2010 Monthly sampling-physical/chemical parameters Low-level mercury and 237 organic compounds Benthos and fish sampled once
• RAMS sampling is ongoing
Through RAMS we are: Assessing “all waters” including small streams Identifying compounds that meet/exceed standards Assessing low-level mercury Assessing organic compounds (pesticides, etc.) Determining proportion of sites meet standards
RAMS Site Locations
RAMS Results are Compared to
NC Water Quality Standards 02B .0208 – Standards for Toxic Substances and Temperature 02B .0211 – Fresh Surface Water Quality Standards for Class C Waters
40 Compounds – NC Standards Aldrin
Endosulfan
PCB
*Arsenic
Endrin
*pH
Benzene
*Fluoride
Phenol
Beryllium
Heptachlor
Selenium
Carbon tetrachloride
Hexachlorobutadiene
*Temperature, Water
Chlordane
*Iron
*Tetrachloroethylene
*Chloride
*Lead, Total
*Trichloroethene
*Chromium, Total
Lindane
*Toluene
*Copper
*Mercury, Total
Toxaphene
Cyanide
Methoxychlor
*Turbidity
DDT 4,4
Mirex
Vinyl Chloride
Demeton
*Nickel, Total
*Zinc
Dieldrin
PAH
*Dissolved oxygen
Parathion
* Detected 17 out of 40
Summarizing Results 1. Statewide approach 2. Individual Station approach
Statewide: data from all 60 Sites Number of results for each parameter Number of results exceeding standard Calculate proportion (%) exceeding standard
Statewide
Minimum sample size 1320+ Compound
Results > Standard
Temperature
10% results > 12 ng/L
• Very low detection rate (
Scale 1:100,000
Results for 2007-2010
Two Types of Monitoring: 1. Physical/Chemical Meters (dissolved oxygen, pH …) Water samples (turbidity, bacteria …)
2.
Biological Benthic Macroinvertebrates Fish Community Fish Tissue Phytoplankton
Two Approaches to Monitoring: 1. Targeted Ambient Monitoring System (AMS) Coalition Monitoring, Biological What are the conditions at a location…?
2.
Random, Statistical, Probabilistic What are the characteristics of a large group?
Targeted Monitoring Sites selected for reasons (AMS, Coalition,
Biological): o Upstream/downstream of a discharger o Water supply o Watershed – long term trends
Hundreds of sites monitored, but a limited
number of parameters sampled
Random Monitoring Sites chosen randomly (e.g. RAMS) Assess a “population” Infer characteristics of the population from the
sample Make statistical statements about a population For RAMS there are 60 sites monitored and hundreds of parameters sampled
RAMS Population = All freshwater streams on the 1:100,000 map
States shall assess “All waters”
Random Selection Each sampling unit of the population has an
equal chance of being selected.
Why 60 Sites? Precision (margin of error) is dependent on: o Number of sites sampled (sample size) o The proportion (e.g. % results > standard)
Proportion 20 %
25 ± 13 %
Sample Size 50 100 ±9% ±7%
50 %
± 17 %
± 12 %
Precision (±)
±8%
400 ±3% ±4%
USEPA http://www.epa.gov/nheerl/arm/surdesignfaqs.htm#samplesize50
RAMS Monitoring (60 sites) • • • • •
29 sites during 2007-2008 31 sites during 2009-2010 Monthly sampling-physical/chemical parameters Low-level mercury and 237 organic compounds Benthos and fish sampled once
• RAMS sampling is ongoing
Through RAMS we are: Assessing “all waters” including small streams Identifying compounds that meet/exceed standards Assessing low-level mercury Assessing organic compounds (pesticides, etc.) Determining proportion of sites meet standards
RAMS Site Locations
RAMS Results are Compared to
NC Water Quality Standards 02B .0208 – Standards for Toxic Substances and Temperature 02B .0211 – Fresh Surface Water Quality Standards for Class C Waters
40 Compounds – NC Standards Aldrin
Endosulfan
PCB
*Arsenic
Endrin
*pH
Benzene
*Fluoride
Phenol
Beryllium
Heptachlor
Selenium
Carbon tetrachloride
Hexachlorobutadiene
*Temperature, Water
Chlordane
*Iron
*Tetrachloroethylene
*Chloride
*Lead, Total
*Trichloroethene
*Chromium, Total
Lindane
*Toluene
*Copper
*Mercury, Total
Toxaphene
Cyanide
Methoxychlor
*Turbidity
DDT 4,4
Mirex
Vinyl Chloride
Demeton
*Nickel, Total
*Zinc
Dieldrin
PAH
*Dissolved oxygen
Parathion
* Detected 17 out of 40
Summarizing Results 1. Statewide approach 2. Individual Station approach
Statewide: data from all 60 Sites Number of results for each parameter Number of results exceeding standard Calculate proportion (%) exceeding standard
Statewide
Minimum sample size 1320+ Compound
Results > Standard
Temperature
10% results > 12 ng/L
• Very low detection rate (
