Massachusetts Water Resources Authority

Transcription

1 Massachusetts Water Resources Authority Sediment Studies in Mass. Bay Wastewater Advisory Committee January 7, 2011 Frederick A. Laskey Executive Director

2 Benthic Nutrient Flux Study Study design Four stations in Boston Harbor, three stations in nearfield,one station in Stellwagen Basin Four surveys/year, May, July, August, October. Intact sediment cores obtained, and incubated at in-situ temperatures in Lab. 2

3 Incubated cores with burrows 10 cm 1 cm BH08A BH02 July

4 Organic Carbon and Chlorophyll a content of surface sediments % TOC Means for the pre- ( ) and postrelocation ( ) periods show no change. For TOC: May- Oct means and SD For Chl a: May, Oct means and SD Chl a (µg cm -2 ) n=7 n=9 n=6 n=9 n=7 n=9 n=6 n=9 MB01 MB02 MB03 MB05 Pre-relocation Post-relocation 2 0 n=5 n=9 n=5 n=9 n=5 n=9 n=5 n=9 MB01 MB02 MB03 MB05 4

5 Sediment Oxygen Demand Mass Bay a. Bay Average SOD mmol O 2 m -2 d MB01 MB02 MB03 MB05 NF Mean FF Mean

6 DIN Flux for Mass. Bay b. Bay Average DIN Flux mmol N m -2 d MB01 MB02 MB03 MB05 NF Mean FF Mean

7 Conclusions for 2009 Massachusetts Bay No indication of increased OM loading to nearfield No change in redox conditions No increase in SOD or nutrient fluxes No discernible change in denitrification, which remains the major component of remineralized N 7

8 Sediment contaminants Most contaminants of concern adhere to fine particulates. So contaminants build up in muddy, depositional areas of the sea floor Organic matter and SOD from effluent would build up in same areas Mass Bay sediments relatively clean, though some contamination exists. 8

9 Contaminants Monitoring since nearfield and 8 farfield stations Since 2003, contaminants sampled every third year. Half of stations sampled annually 2008: 13 NF, 4 FF Surface (0-2 cm) sediments GS, TOC, Clostridium, Organic contaminants and metals 9

10 Total Organic Carbon Total Organic Carbon 10 FF10 FF13 NF17 NF19 NF23 NF18 NF12 NF16 NF07 NF09 NF22 NF08 NF05 FF09 FF04 FF05 FF07 Transition Area 2 1 Range Mean Mean 2008 Station Mean 0 Nearfield (<2 km from outfall) Nearfield (>2 km from outfall) Farfield Concentration (%) Farfield Nearfield (<2 km) Nearfield (>2 km) Transition Mean(TOC (%))

11 Clostridium perfringens Clostridium perfringens (normalized to percent fines) Series1 Mean 2009 Station Mean Station Mean 0 FF12 FF10 FF13 NF24 NF17 NF19 NF23 NF14 NF13 NF18 NF15 NF12 NF16 NF07 NF10 NF21 NF20 NF04 NF09 NF22 Farfield NF08 NF05 NF02 FF11 FF01A FF14 11 Nearfield (>2 FF09 km) FF04 FF05 FF06 FF07 Transition Area Nearfield (<2 km from outfall) Nearfield (>2 km from outfall) Farfield Station by Sample Area Concentration (cfu/g dry/% fines) Nearfield (<2 km) Transition Mean(Normalized C. perfringens

12 PCB 25 Total PCB FF10 FF13 NF17 NF19 NF23 NF18 NF12 NF16 NF07 NF09 NF22 NF08 NF05 FF09 FF04 FF05 FF07 Transition Area Nearfield (<2 km from outfall) ER-L Range Mean Mean 2008 Station Mean 0 Nearfield (>2 km from outfall) Farfield Concentration (ng/kg dry) Farfield Nearfield (<2 km) Nearfield (>2 km) Transition Mean(Total_PCB (ng/kg dry))

13 PAH Total PAH FF10 FF13 NF17 NF19 NF23 NF18 NF12 NF16 NF07 NF09 NF22 NF08 NF05 FF09 FF04 FF05 FF07 Transition Area Nearfield (<2 km from outfall) ER-L Range Mean Mean 2008 Station Mean Nearfield (>2 km from outfall) Farfield Concentration (ng/kg dry) Farfield Nearfield (<2 km) Nearfield (>2 km) Transition Mean(Total_PAH (ng/kg dry))

14 Conclusions 2008 data generally consistent with long-term data. Clostridium clear signature of effluent discharge in nearby sediments No significant difference between baseline and post-diversion means for most chemicals, except Total DDT and total PCB Long-term data indicate no accumulation of toxic chemicals following effluent diversion 14

15 2009 Sediment Profile Imaging. 15

16 Sea-floor and sediment profile images Burrow openings 16

17 Nearfield Summary for 2009 Sediments similar to arpd for 2009 trended shallower than 2008 but still deeper than. arpd Post- deeper than. 17

18 Summary for Nearfield from 1995 to date Operation of outfall, starting in 2001, did not appear to effect benthic habitat quality. arpd Post- was always deeper than. Sediment characteristics remained similar through time. 18