Sturgeon Lake Sediment Sampling. Study Proposal. Introduction

Transcription

1 Sturgeon Lake Sediment Sampling Study Proposal Introduction Lake sediments are an essential part of the aquatic environment. Sediments accumulate and transform fine materials, organic matter, and the remains of aquatic vegetation and organisms. It is also the habitat of many aquatic organisms including benthic macroinvertebrates. Physicochemical processes at the water sediment interface can considerably influence water quality in water bodies. Through the history of its existence Sturgeon Lake has accumulated a substantial amount of sediments on its bottom. As a result of human activities over the last two centuries, considerable quantities of nutrients, metals and artificial organic contaminants have accumulated in the lake bottom sediments. Further development around the lake and in its watershed will continue to exert anthropogenic pressure on the lake ecosystem, increasing contaminant concentrations in both water and sediments, and exacerbating existing issues. Currently excessive growth of aquatic vegetation in Sturgeon Lake has been recognized as a problem for boaters and other recreational lake users. Lake sediments along with other nutrient sources supply a considerable amount of phosphorous and nitrogen, promoting excessive aquatic plant growth. The proliferation of macrophytes and weeds in the shallow portions of the lake is especially noticeable. Removing the allochthonous sources of nutrients alone, will not improve these conditions in the near future. To restore the lake to healthy and balanced conditions, the local authorities will also need to address the internal source of nutrients found in lake sediments. Another issue with the Sturgeon Lake sediments (at least in the southern portion of the lake) is that there are multiple reports from the past that demonstrate contamination of the lake sediments by PCBs and heavy metals. The Ministry of the Environment (MOE) studies in 1975, 1976, 1986, 1994, 1998 and as well as an Environment Canada study in 1993 have all revealed contaminated sediments in the southern portion of the lake and in the Scugog River downstream of Lindsay. In the framework of the Environment Canada study there were 15 sediment samples collected in the nearshore areas. PCBs were detected in 14 out of 15 samples. At the same time it is necessary to note that the above-mentioned studies were concentrated only in the southern portion of the lake and did not provide information on sediment quality in the northern parts of the lake, near Fenelon Falls and Bobcaygeon in particular. It is widely recognized that artificial organic and inorganic pollutants are a substantial threat to the health of aquatic ecosystems. Many of these pollutants are extremely toxic and dangerous to aquatic life, and some of them can pose similar health risks for humans,

2 especially if these contaminants make their way into drinking water. A number of compounds being investigated are very persistent, such as organochlorinated pesticides (OCP), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and heavy metals, which may have been released into the environment years ago but are still dangerous for biota and humans. Sediments can accumulate these chemical compounds and may serve as a contaminant reservoir and a source of pollution as a result of re-suspension following a number of human activities. Contaminated sediments can significantly impact the benthic environment and, as a result of bioaccumulation by benthic organisms, some contaminants can work their way up the food chain (process of biomagnification). Therefore, it is essentially necessary to carry out long-term permanent monitoring of these dangerous compounds in Sturgeon Lake sediments. It can help to evaluate trends in their concentrations over long periods, compare sediment quality to the provincial and federal standards, and develop measures, where applicable, for restoration and improvement of the lake ecosystem. There is increasing pressure from the general public, various volunteer organizations (KLSA, KPOW etc.) concerning the necessity of sampling and consecutive chemical analysis of sediments from Sturgeon Lake as part of the Sturgeon Lake Management Plan (SLMP) development. At the same time it is also necessary to keep in mind that such a study requires substantial funds, considerable amount of Kawartha Conservation staff time and significant support from provincial and federal ministries and agencies. Taking into consideration all above-mentioned and understanding the importance of a sediment study for the successful Sturgeon Lake Management Plan development, Kawartha Conservation, supported by the SLMP Community Advisory Panel, has come to the decision to undertake a comprehensive lake-wide sediment sampling on Sturgeon Lake in 2011 and 2012 in partnership with the MOE. The MOE has agreed to provide funding in 2011 and then in 2012 for the laboratory analysis of seven sediment samples each year. We recognize that a substantial number of sediment studies in Sturgeon Lake were previously accomplished during s. The most recent sediment study in the Scugog River downstream of Sinister Creek was completed by the MOE in 2009 (report in preparation). Nevertheless, it is almost eighteen years since the lake-wide study was accomplished by Environment Canada. A new comprehensive survey of the lake sediments is needed in order to maintain long-term monitoring and to obtain new updated sediment quality data for the benefit of all agencies involved in the management of the lake. Study Outline Sediment samples will be collected from a number of sampling sites across the lake representing different portions of the lake and providing the possibility for comparison between sites. Furthermore, it can help to reveal background concentrations of some chemicals in the lake sediments. It is currently proposed to collect samples from 14 locations. Where possible, two layers (0-10 cm and cm) of sediments will be analyzed separately. Sample substrate within each subsection will be thoroughly homogenized. Samples will be collected according to the

3 established sampling methodology using Ekman tall grab sampler or K-B Corer if available. In case if K-B Corer is available, samples from two or three sites will be sectioned every 5 cm to provide a better temporal sequence in sediment contamination. As well, samples for the benthic macro-invertebrate community assemblage will be collected with Ekman sampler and identified at family level. Preliminary sampling locations are presented in Table 1 and on Figure 1. Stations are located across the entire lake to represent all parts of the lake that are under different natural and anthropogenic influences as well as various types of sediments. Station SD7 downstream of Fenelon Falls should provide clean unaffected sediments that will serve as a reference sample. It is believed that 14 sampling locations should provide enough data to characterize current sediment quality in the lake as well as for the further deeper scientific analysis. Table 1. Sturgeon Lake Sediment Sampling Stations Station ID Station Name & Location Location Description 2011 SD1 Kenrei Park subdivision Southwest of Green Island, near shore SD2 Pickerel Point Between buoys CP28 and CP30 SD3 Snug Harbor traverse, east shore North from buoy CP17 SD4 Snug Harbor traverse, middle In the middle of the lake SD5 Snug Harbor traverse, west shore South of Southview Estates, near shore SD6 Pleasant Point Near entrance into residential canal SD7 Downstream of Fenelon Falls Between buoys N5 and N7, closer to the west shore SD8* Ball Point West of Ball Point peninsula, near shore 2012 SD1-12 Kennedy Bay Near entrance into Kennedy Bay SD2-12 Sturgeon Point West of buoy C396, close to the shore SD3-12 Sandy Point Near entrance into residential canal SD4-12 Thurstonia East from public dock SD5-12 Verulam Park Near Verulam Park, north shore SD6-12 Emily Creek mouth Emily Creek mouth, north from causeway SD7-12 Muskrat Island Southwest from buoy C388 SD8-12* Kenstone Beach Near Kenstone Beach, east of buoy C380 * Possible additional locations It is proposed to analyze sediment samples for the following chemical parameters and/or contaminants: 1) Trace metals including mercury; 2) Total Petroleum Hydrocarbons (CCME method); 3) Organochlorinated pesticides (OCP) including total PCBs; 4) Polycyclic Aromatic Hydrocarbons (PAHs); 5) Total phosphorus (TP), total organic nitrogen (TKN), and total organic carbon (TOC); 6) Particle size.

4 The chemical parameters selected for laboratory analysis represents both nutrients and metals and some of the most widespread toxic contaminants found in natural waters and sediments. The majority of these parameters are included in the Canadian Environmental Protection Agency s (CEPA) Priority Toxic Substances Lists. In order to evaluate the quality of the sediment samples collected, the analytical results will be compared to the Guidelines for the Protection and Management of Aquatic Sediment Quality in Ontario elaborated by the Ontario Ministry of the Environment (MOE) and dated August 1993, and to the Canadian Sediment Quality Guidelines for the Protection of Aquatic Life (CSeQGs) contained in the Canadian Council of the Ministries of the Environment (CCME) Summary of Existing Canadian Environmental Quality Guidelines (CEQGs), dated December 2004, where the Provincial Sediment Quality Guidelines are not available. Approximate cost of analysis for the package of all above parameters will be around $500 per sample. Analyses for TPH, OC pesticides and PAHs are the most expensive and take the largest portion of this sum. Expected Results The study results will provide new updated sediment quality data for the benefit of all agencies involved in the management of the lake. It will allow to establish and maintain longterm monitoring of contaminated sediments in Sturgeon Lake. Comparison of new data with that of Environment Canada survey 18 years ago can provide opportunity to detect trends and forecast future fate of the contaminants. The study data and conclusions based on their analysis will be communicated to all interested agencies (MOE, EC, TSW, DFO, MNR) for their use in the routine lake management. The study results will be also integrated into the Sturgeon Lake Watershed Characterization Report and the Sturgeon Lake Management Plan.

5 Figure 1. Map of Sediment Sampling Stations on Sturgeon Lake