title: Effect of intensive catchment and in-lake restoration procedures on phosphorus concentrations in a eutrophic lake

authors: Özkundakci, Deniz

subjects: eutrophication

abstract: Lake Okaro is a small, warm monomictic lake in central North Island, New Zealand, which progressed from oligotrophic to eutrophic through the 1960s. Trends in phosphorus (P) concentrations in the lake are linked to multiple restoration efforts over a 5-year period (2003–2008). The restoration procedures include a 2.3 ha constructed wetland established in February 2006 and riparian margin protection to reduce external loading, as well as an Alum application in December 2003 and sediment capping using modified zeolite in September 2008 to reduce internal loading. The annual average total phosphorus (TP) concentration in the lake decreased by 41% from 2004–2005 to 2007–2008. Two predictive models based on external P loading data generally underestimated the measured TP concentrations in the water column due to internal P loading. The relatively rapid response of TP concentrations after reduction of the internal loading using modified zeolite suggests that this technique can effect a rapid decrease in lake water TP concentrations though the trophic state of Lake Okaro showed high resilience to the reduced P loading. It is concluded that the combined effect of all restoration procedures resulted in a relatively rapid decrease in TP concentrations in Lake Okaro, which may be prolonged by continued external load reduction.

text: Effect of intensive catchment and in-lake restoration procedures on phosphorus concentrations in a eutrophic lake Lake Okaro is a small, warm monomictic lake in central North Island, New Zealand, which progressed from oligotrophic to eutrophic through the 1960s. Trends in phosphorus (P) concentrations in the lake are linked to multiple restoration efforts over a 5-year period (2003–2008). The restoration procedures include a 2.3 ha constructed wetland established in February 2006 and riparian margin protection to reduce external loading, as well as an Alum application in December 2003 and sediment capping using modified zeolite in September 2008 to reduce internal loading. The annual average total phosphorus (TP) concentration in the lake decreased by 41% from 2004–2005 to 2007–2008. Two predictive models based on external P loading data generally underestimated the measured TP concentrations in the water column due to internal P loading. The relatively rapid response of TP concentrations after reduction of the internal loading using modified zeolite suggests that this technique can effect a rapid decrease in lake water TP concentrations though the trophic state of Lake Okaro showed high resilience to the reduced P loading. It is concluded that the combined effect of all restoration procedures resulted in a relatively rapid decrease in TP concentrations in Lake Okaro, which may be prolonged by continued external load reduction.

year: 2010

title: Thermal state of permafrost and active-layer monitoring in the antarctic: Advances during the international polar year 2007-2009

authors: Vieira, Goncalo

subjects: permafrost temperature

abstract: Results obtained during the International Polar Year (IPY) on the thermal state of permafrost and the active layer in the Antarctic are presented, forming part of ANTPAS ( Antarctic Permafrost and Soils ), which was one of the key projects developed by the International Permafrost Association and the Scientific Committee for Antarctic Research for the IPY. The number of boreholes for permafrost and active-layer monitoring was increased from 21 to 73 during the IPY, while CALM-S sites to monitor the active layer were increased from 18 to 28. Permafrost temperatures during the IPY were slightly below 0°C in the South Shetlands near sea-level, showing that this area is near the climatic boundary of permafrost and has the highest sensitivity to climate change in the region. Permafrost temperatures were much lower in continental Antarctica: from the coast to the interior and with increasing elevation they ranged between -13.3°C and -18.6°C in Northern Victoria Land, from -17.4°C to -22.5°C in the McMurdo Dry Valleys, and down to -23.6°C at high elevation on Mount Fleming (Ross Island). Other monitored regions in continental Antarctica also showed cold permafrost: Queen Maud Land exhibited values down to -17.8°C on nunataks, while in Novolazarevskaya (Schirmacher Oasis) at 80 m a.s.l. the permafrost temperature was -8.3°C. The coastal stations of Molodeznaya at Enderby Land showed permafrost temperatures of -9.8°C, Larsemann Hills - Progress Station in the Vestfold Hills region - recorded -8.5°C, and Russkaya in Marie Byrd Land, -10.4°C. This snapshot obtained during the IPY shows that the range of ground temperatures in the Antarctic is greater than in the Arctic.

text: Thermal state of permafrost and active-layer monitoring in the antarctic: Advances during the international polar year 2007-2009 Results obtained during the International Polar Year (IPY) on the thermal state of permafrost and the active layer in the Antarctic are presented, forming part of ANTPAS ( Antarctic Permafrost and Soils ), which was one of the key projects developed by the International Permafrost Association and the Scientific Committee for Antarctic Research for the IPY. The number of boreholes for permafrost and active-layer monitoring was increased from 21 to 73 during the IPY, while CALM-S sites to monitor the active layer were increased from 18 to 28. Permafrost temperatures during the IPY were slightly below 0°C in the South Shetlands near sea-level, showing that this area is near the climatic boundary of permafrost and has the highest sensitivity to climate change in the region. Permafrost temperatures were much lower in continental Antarctica: from the coast to the interior and with increasing elevation they ranged between -13.3°C and -18.6°C in Northern Victoria Land, from -17.4°C to -22.5°C in the McMurdo Dry Valleys, and down to -23.6°C at high elevation on Mount Fleming (Ross Island). Other monitored regions in continental Antarctica also showed cold permafrost: Queen Maud Land exhibited values down to -17.8°C on nunataks, while in Novolazarevskaya (Schirmacher Oasis) at 80 m a.s.l. the permafrost temperature was -8.3°C. The coastal stations of Molodeznaya at Enderby Land showed permafrost temperatures of -9.8°C, Larsemann Hills - Progress Station in the Vestfold Hills region - recorded -8.5°C, and Russkaya in Marie Byrd Land, -10.4°C. This snapshot obtained during the IPY shows that the range of ground temperatures in the Antarctic is greater than in the Arctic.

year: 2010

title: Environmental aspects of storm runoff discharge from a timber port, Tauranga, New Zealand

authors: Tian, Fengming

subjects: storm runoff water

abstract: An investigation was undertaken into storm runoff water quantity and quality, contaminant input to the receiving tidal waters from the Mt. Maunganui wharf, accumulation of potentially toxic resin acids in adjacent sediments, and the dilution of the wharf runoff in the receiving tidal waters, in order to assess the possible adverse environmental impact associated with the log operation at the Port of Tauranga Ltd.
Based upon field data and rainfall records, about a half of the annual precipitation over the log handling areas is converted to surface runoff (117,000 m³a⁻¹). Annual runoff volume per hectare of wharf surface is estimated as 7,500 m³ha⁻¹a⁻¹ for the sealed area and 3,700 m³ha⁻¹a⁻¹ for the gravelled area.
The optical quality of the wharf runoff is degraded due to addition of bark and soil particles. The black disk visual clarity (0.01-0.02 m) was only 0.5-1.0% of that in the receiving tidal waters. The wharf runoff appears very dark gray to yellowish brown in apparent colour (10YR1/3 to 10YR5/6 Munsell colour chart) and has a soluble yellow substance concentration of about 25 m⁻¹. Power relationships between the traditionally used parameters, for example, suspended solids and turbidity, were identified. The wharf surface pavement types had a significant influence on visual clarity, but little influence on yellow substance concentration.
The potentially toxic resin acids in the wharf runoff have been determined with SIM GC-MS. The average total resin acid level (1,030 ppb) is comparable to that of 1,000 ppb reported at which acute toxicity is likely to be exhibited. A relationship of resin acids against volatile suspended solids was established. Tests undertaken suggest that conventional treatment methods of natural sedimentation and flocculation-sedimentation are able to remove the resin acids effectively.
The levels of biological oxygen demand (BOD), total phosphorus and nitrogen in the wharf runoff are considerably higher than those of common urban runoff. However, the wharf runoff contributes little nitrate nitrogen and oil and grease to the receiving environment.
About 87,500 kg of suspended solids, 43,000 kg of volatile suspended solids, 14,200 kg of BOD, 500 kg of phosphorus, and 103 kg of resin acids are discharged to the Tauranga Harbour annually from runoff from the Mt. Maunganui wharf.
Analyses show that the impact on adjacent sediments from the storm runoff is limited to a distance of about 100 m from the discharge points and the resin acid levels in the sediments within this distance are not significantly higher compared to that of the storm runoff. The net resin acid accumulation rate in the shipping channel (Stella Passage) beside the log handling areas was estimated to be in the range of 300 to 370 ppb per year.
Based on field investigation and numerical simulations, the findings on dispersion and dilution of the wharf runoff in the receiving tidal waters are as follows: (i) the sea water around Stella Passage experiences an obvious natural salinity stratification, the extent of which depends greatly on the weather conditions; (ii) the wind drag stress and the pressure gradient caused by the addition of runoff had the greatest influence on the plume dynamics during the flood tide. The plumes basically remain within the top 2-3 m of the water column under different winds; (iii) the plume is unlikely to advect to the Whareroa Marae under strong (30-40 knots) easterly or northeasterly winds for a storm with a 5-year return period. However, there is an obvious influence on the Whareroa Marae under 30- 40 knot northerly winds; and (iv) the short duration and restricted region of the low dilution pulse of effluent around slack water may explain why there has been no reports of acute toxic events.
Sealing the gravel covered wharf area, improving the sweeping efficiency, and extending the present outfalls to the sea floor might be potential options for mitigating the environmental impact associated with discharge of the wharf runoff.

text: Environmental aspects of storm runoff discharge from a timber port, Tauranga, New Zealand An investigation was undertaken into storm runoff water quantity and quality, contaminant input to the receiving tidal waters from the Mt. Maunganui wharf, accumulation of potentially toxic resin acids in adjacent sediments, and the dilution of the wharf runoff in the receiving tidal waters, in order to assess the possible adverse environmental impact associated with the log operation at the Port of Tauranga Ltd.
Based upon field data and rainfall records, about a half of the annual precipitation over the log handling areas is converted to surface runoff (117,000 m³a⁻¹). Annual runoff volume per hectare of wharf surface is estimated as 7,500 m³ha⁻¹a⁻¹ for the sealed area and 3,700 m³ha⁻¹a⁻¹ for the gravelled area.
The optical quality of the wharf runoff is degraded due to addition of bark and soil particles. The black disk visual clarity (0.01-0.02 m) was only 0.5-1.0% of that in the receiving tidal waters. The wharf runoff appears very dark gray to yellowish brown in apparent colour (10YR1/3 to 10YR5/6 Munsell colour chart) and has a soluble yellow substance concentration of about 25 m⁻¹. Power relationships between the traditionally used parameters, for example, suspended solids and turbidity, were identified. The wharf surface pavement types had a significant influence on visual clarity, but little influence on yellow substance concentration.
The potentially toxic resin acids in the wharf runoff have been determined with SIM GC-MS. The average total resin acid level (1,030 ppb) is comparable to that of 1,000 ppb reported at which acute toxicity is likely to be exhibited. A relationship of resin acids against volatile suspended solids was established. Tests undertaken suggest that conventional treatment methods of natural sedimentation and flocculation-sedimentation are able to remove the resin acids effectively.
The levels of biological oxygen demand (BOD), total phosphorus and nitrogen in the wharf runoff are considerably higher than those of common urban runoff. However, the wharf runoff contributes little nitrate nitrogen and oil and grease to the receiving environment.
About 87,500 kg of suspended solids, 43,000 kg of volatile suspended solids, 14,200 kg of BOD, 500 kg of phosphorus, and 103 kg of resin acids are discharged to the Tauranga Harbour annually from runoff from the Mt. Maunganui wharf.
Analyses show that the impact on adjacent sediments from the storm runoff is limited to a distance of about 100 m from the discharge points and the resin acid levels in the sediments within this distance are not significantly higher compared to that of the storm runoff. The net resin acid accumulation rate in the shipping channel (Stella Passage) beside the log handling areas was estimated to be in the range of 300 to 370 ppb per year.
Based on field investigation and numerical simulations, the findings on dispersion and dilution of the wharf runoff in the receiving tidal waters are as follows: (i) the sea water around Stella Passage experiences an obvious natural salinity stratification, the extent of which depends greatly on the weather conditions; (ii) the wind drag stress and the pressure gradient caused by the addition of runoff had the greatest influence on the plume dynamics during the flood tide. The plumes basically remain within the top 2-3 m of the water column under different winds; (iii) the plume is unlikely to advect to the Whareroa Marae under strong (30-40 knots) easterly or northeasterly winds for a storm with a 5-year return period. However, there is an obvious influence on the Whareroa Marae under 30- 40 knot northerly winds; and (iv) the short duration and restricted region of the low dilution pulse of effluent around slack water may explain why there has been no reports of acute toxic events.
Sealing the gravel covered wharf area, improving the sweeping efficiency, and extending the present outfalls to the sea floor might be potential options for mitigating the environmental impact associated with discharge of the wharf runoff.

year: 1997