Introduction
The federal legal framework through the “Clean Water Act and the Marine Protection, Research and Sanctuaries Act 103”, provides for biological evaluations to be conducted as a way to determine suitability of dredged material. The appraisals included ascertaining biological consequences of various dimensions and levels of bio build-up that resulted from the presence of chemical pollutants in the sediments. The site reconnaissance conducted several tests in order to determine contamination levels at the site.
Site reconnaissance and walk-over report findings
The map provided below represented an extract from a local site slated to be the subject of a mixed commercial and residential development. While the development is a viable economic project, environmental challenges affecting the selected site complicated the whole situation. A petrol station adjacent to the site in Eastney was discovered to have LUST attributable to corrosion of the old GI petrol storage tank which caused a steady drip leakage and seepage for more than 30 years.
An assessment was conducted on the site to determine presence of contamination indicators. Past industrial activities showed that there were gas works allies within a radius of 500 metres around the site. There were also relics in form of some abandoned buildings, old structures.
Upon further investigation, the assessment found out that there were no signs of subterranean fires or land fill gas. The reviews encompassed estimation of organic effects of the scope of bio-accumulation that resulted in presence of chemical impurities in the deposits (Price et al. 2003, p.31). Sediment extracts from the site that were tested had the possibility of providing quick low cost deducible options, however they had shortcoming of not accurately reflecting pollutant availability. Bioavailability of non-polar organic pollutants in dredged materials had consequences for geo-chemical features like soot concentration (Gustaffsson, et al 1997, p. 203; Brannon et al. 1998, p. 334).
The appraisal focus depended on addition of extractants that had an effect on changes of sediment composition and geo-chemistry that was known to cause changes in bioavailability of Polyaromatic Hydrocarbons (PAHs) from the sediments (Price, et al. 2003, p. 31). Soot improvement was used to alter sediment pollution bioavailability and to establish whether concomitant extractability was linked to bioavailability. Soot deposits from available facts demonstrated that availability of PAHs to exposed organisms was present. Soot absorbed non polar organic pollutants like PAHs could be more than absorbed into organic carbon.
Therefore, appraisals utilized adsorption testing, using various solvents and testing bioaccumulation of phenanthrene using two organisms to determine whether pollution and sedimentation was taking shape. Leaching tests were also conducted which were useful in risk assessment to quantify risk for ground water and surface water (Grathwohl 1990 p. 1687).
A General Overview of the Site
The site appeared quite different from other surroundings’ topography, available vegetation, soil type and the drainage systems. This was attributable to infill materials that were deposited as waste. Further observation showed that there were some patches of sparsely vegetated cover over the rest of the site. While some trees appeared mature and old, some appeared stunted with yellowing of leaves, premature leaf fall, dead branches and shedding of the bark.
Old trees were not regenerating their young offshoots which was an indication that there was stress. The vegetation and plants had poor spread of their roots, which had white nodules. Some of the vegetation on the site had undergone defoliation, yellowing and discoloration of their leaves. Some were experiencing wilting while others remained stunted. The leaves had yellow blotches caused by pollution.
Plant species spread was dominantly homogenous with rare diversity being registered. Herbaceous and perennial plants were missing in some regions. The soil PH was also tested and acid soil was reported to have a PH of 4.7, natural soil – PH 4.8, calcerous soil – PH, 4.9. The lake region had plant species that included orchids which thrived in high PH of 4.9, vernal sandwort that survived lead and other metals. Rushes were present in waterlogged areas while nettles thrived in areas with high nitrogen and phosphorus. There were also surface stains such as blue billy which resulted from gas works waste, black sulphide due to land fill gas deposits. There were oily patches emerging from chemicals, processing or transport industries.
Other odors were smelled that had the following characteristics: “bad eggs” smell indicated the presence of hydrogen and sulphide components (H2S), phenols from antiseptics, ethers from solvents and diesel or petrol. A test on the soil PH and distilled water slurry was found to be higher in some areas with bare patches of vegetations, stains and odors. Furthermore some organisms like worms were missing in some parts with bare patches.
Soil structure and compaction or waterlogging was also common. The depth of organic matter in the areas with bare patches on the surface of the soil was compared to areas with vegetations and depth of surface litter on land. There were obvious signs of contamination in form of discoloration, stains, mineral deposits, odor associated with stagnant water, green algae along the coastline. The water in the lake was cloudy suggesting that sediments existed together with clay particles. Besides, the streams leaving the site were all contaminated as compared to those entering suggesting that contamination was happening at the site.
Adsorption Testing (Materials and Methods)
Sediments were obtained from the lake adjacent to Fraser range lake using the grab sampler. The sediments were comprised of soil proportions as follows: 11% sand, 78% silt and 11% clay. The sediment had a total organic carbon content of 0.83%. The adsorption tests were also conducted in triplicate in 25 mili litres and 4 grams of centrifugal tubes or Oven Dry Weight (ODW) of deposits. It also consisted of low proportions of soot in form of diesel infiltrate. Tests were also done with 16 mili litres of condensed de-ionized PAH that encompassed phenanthrene at various concentrations. The phenanthrene solution comprised radio labeled sigma composed of 1% to 99% unlabelled phenanthrene. Sediment samples were condensed at 8000 rpm for a period of 30 minutes.
Sediment selection
The selection process relied on sediment extraction and soxhlet extraction techniques. Sediment or deposit trials were analyzed at a concentration of 10 ODW using the similar concentration ratios that were either marked or unmarked with phenanthrene. Tests were done for 24 hours and were observed under room temperature of 24 degrees centigrade. Furthermore, a typical solvent combination that comprised three quarters of methylene chloride and one quarter of acetone solution of 15 mili litres was added to each 5 grams of the sample. Furthermore, six more sonication methods were utilized to the sediment samples.
Solvent selection
The selection relied on and identified solvent responses to changes in sediment phenanthrene solutions as a function of soot concentration. An example of samples from the lake deposits were analyzed with marked as phenanthrene of 9.9 ODW and radio marked as phenanthrene of 0.1 ODW. The samples stayed for 5 days in order to age. The soot was added to one of the extracted lake deposit concentrations of 0.1 ODW.
Biological exposure tests
Burrowing organisms like lumbriculus variegates were obtained from biological lab supplies through aquatic research organisms (Hampton, N.H). The burrowing species were kept in tap water for five days. Another organism lumbriculus tentarus was fed on tetramin fish food going by recommendations by EPA (USEPA, 1999). Soot concentrations at 0.1, 0.25 and 0.5 were tested. Within a five day aging period exposures were conducted in 22 mili litre glass scintillation with 7 grams of deposits from the site. Air flow and Water levels were examined under usual temperature that ranged within 21-24 degrees. The organisms that were used for experimentation were taken back after 1 week and put in a tap water volume of 1mili litre to remove sediment from intestinal tract.
Leaching tests
The leaching tests were instrumental in risk assessment to be able to quantify the risk for ground water and surface water contamination. It provided information on the potential impact of contaminants. Leaching tests were used in appraising the risks of potential pollutants. Percolation tests used were preferred because they were able to replicate the flow of water through solid material that was almost close to natural conditions. The contamination levels determined provided information on the best strategies for treatment.
Results
The tests conducted on the site showed that bioavailability and extractability of phenanthrene sediment extracts had changes in pollutant concentrations particularly in sediment bioavailability. The results showed that site was highly contaminated. The earth organisms such as lumbriculus and chironomus were used in the experiment and indicated that quantity of phenanthrene recovered by extractants were highly polluted deposits.
Many of the solvents that were used to establish usefulness for assessment of changes were conducted in bioavailability phenanthrene. Amongst the selected solvents for assessment were solvents tested against phenanthrene together with two earth organisms in deposits with soot concentration of below 0.5% The results showed that sedimentation and bioaccumulation of phenanthrene by lumbriculus and chironomus had an effect on soot concentration which increased. The discovery indicated that reproduction of organisms used in solvent extraction of sediments was appropriate in chosen extractants that were tried with polluted sediments from the field with various poisonous levels.
Recommendations
The site was discovered to be highly concentrated with contaminants suggesting that any further development on the traction of land would lead to further damage. The intended development project needed to be postponed till decontamination measures on site were complete. More developments would entrench ecosystem stress on organisms and other stakeholders in the ecosystem.
Conclusion
The report findings have assessed the effect of organic contamination on the proposed land for development. The assessments have endeavored to appraise adsorption, biological exposure tests and leaching tests. All the tests have demonstrated that the area is organically contaminated affecting underground, surface and physical vegetation. Any further development on the site would strain more eco-systems. Bioavailability of contaminants in the proposed development would be halted till environmental cleanup of the site is conducted. A further risk impact assessment is required to determine the level of reduced contamination.
References
Brannon, JM, Dans, W, McFarland, VA, & Hayes, C 1998, ‘Organic Matter Quality and Partitioning of PCB’, Bulletin of Environmental Contamination and Toxicology, vol. 61. no. 3, pp. 333-338.
Grathwohl, P 1990, ‘Influence of Organic Matter from Soils and Sediments from Various ongoing on the Absorption of Some Chlorinated Aliphatic Hydro-Carbon: Implications on Koc Correlations’, Environmental Science and Technology, vol. 24, pp. 1687-1693.
Gustafsson, O, Haghseta, F, Chan, C, MacFarlane, J, & Gaschwend, PM 1997, ‘Quantification of the Dilute Sedimentary Soot Phase: Implication for PAH Specification and Bioavailability,’ Environmental Science and Technology, vol. 31, pp. 203-209.
Price C, Inouye, L, Brannon, J, McFarland, V, & Hayes C 2003, ‘Development of Sediment Extracts for Rapid Assessment of Organic Contaminant Bioavailability’, ERDC/Technical Notes Collection EEDP, vol. 2. no. 31, pp. 1-10.