Nutrient Criteria for New Hampshire’s Estuaries Background Information Phil Trowbridge NH DES /...
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Transcript of Nutrient Criteria for New Hampshire’s Estuaries Background Information Phil Trowbridge NH DES /...
Nutrient Criteria for New Hampshire’s
EstuariesBackground Information
Phil TrowbridgeNH DES / NHEP
September 30, 2005
Existing “Nutrient Criteria” for NH
• Dissolved oxygen: 5 mg/L (instantaneous)75% sat (24 hr average)RSA 485-A:8
• Nutrients: “Class B waters shall contain no phosphorus or nitrogen in such concentrations that would impair any existing or designated uses, unless naturally occurring.”
Admin Rule: Env-Ws 1703.14
• Chlorophyll-a: 20 ug/L (>10% of samples)DES-WMB Policy # 009
Goal for the Nutrient Criteria Process
• To improve these criteria and/or add other criteria so that DES can accurately assess cultural eutrophication in NH’s estuaries.
Regulatory Implications
• Assessments: Criteria will be used to determine violations of water quality standards (“impairments”).
• TMDLs: For most impairments, a Total Maximum Daily Load study will be done.
• Regulations: Results of TMDLs become discharge limits in point source NPDES permits and other sources.
• This process has already begun using the existing criteria.
Nutrients in NH’s Estuaries
• Long-Term Water Quality Trends in Great Bay
• Current Conditions from 2004 Probabilistic Survey
• NH nutrient concentrations relative to other systems in the Northeast
Seasonal Mean Dissolved Inorganic Nitrogen at Low Tide at Adams Point
0
0.1
0.2
0.3
0.4
0.5
1970 1975 1980 1985 1990 1995 2000 2005
Year
DIN
(m
g/L
) Winter
Spring
Summer
Fall
Seasonal Mean Orthophosphate at Low Tide at Adams Point
0
0.01
0.02
0.03
0.04
0.05
0.06
1970 1975 1980 1985 1990 1995 2000 2005
Year
PO
4 (m
g/L
)
Winter
Spring
Summer
Fall
Seasonal Mean Chlorophyll-aat Low Tide at Adams Point
02468
101214
1970 1975 1980 1985 1990 1995 2000 2005
Year
Ch
la (
ug
/L)
Winter
Spring
Summer
Fall
Current Conditions in NH’s estuaries
Nutrient and Eutrophication Parameters from NCA 2004
Parameter N Median RangeTN (mg/L) 35 0.36 (0.0161-1.14)TP (mg/L) 40 0.07 (0.025-0.248)SiO2 (mg/L) 41 0.62 (0.166-5.639)Kd (1/m) 17 -1.31 (-5.753- -0.366)TN:TP ratio 34 5.89 (2.875-16.09)
* Samples taken during summer season
Nitrogen in Northeast Estuaries
Average Total Nitrogen in Estuarine Waters (2003) Source: NCA and LISS
0
0.2
0.4
0.6
0.8
1
1.2
1.4
ME NH MA RI LIS NJ DE
TN
(m
g/L
)
Phosphorus in Northeast Estuaries
Ave Total Phosphorus in Estuarine Waters (2003)Source: NCA and LISS
0
0.02
0.04
0.06
0.08
0.1
0.12
ME NH MA RI LIS NJ DE
TP
(m
g/L
)
Summary
• New Hampshire’s existing nutrient criteria are minimal and not specific to estuarine environments.
• Impairments for DO and chlorophyll-a criteria already exist.
• Winter DIN concentrations have increased in Great Bay.
• Average TN and TP concentrations are similar to RI and Long Island Sound.