The Effects of Small Dam Removal on the Distribution of Sedimentary Contaminants

With increasing concern over degradation of aquatic resources, issues of liability, and maintenance costs, removal of small dams has become increasing popular. Although the benefits of removal seem to outweigh the drawbacks, there is a relative paucity of studies documenting the extent and magnitude of biological and chemical changes associated with dam removal, especially those evaluating potential changes in contaminant inventories. In August and November of 2000, a run-of-the-river dam on Manatawny Creek (southeast Pennsylvania) was removed in a two-stage process. To assess the effects of dam removal on the contaminant redistribution within the creek, sedimentary concentrations of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and trace metals (Cd, Cr, Cu, Ni, Pb, Zn) were evaluated prior to and several months after removal. Pre- and post-removal analyses revealed elevated and spatially variable concentrations of total PAHs (ranging from approximately 200 to 81,000 ng(g dry weight) and low to moderate concentrations of trace metals and PCBs. The concentrations of these sedimentary contaminants pre- versus post-removal were not significantly different. Additionally, though the impoundment received storm water run-off and associated contaminants from the adjacent city of Pottstown, the total inventory of fine-grain sediments in the impoundment prior to removal was very low. The removal of the low-level Manatawny Creek dam did not significantly redistribute contaminants downstream. However, each dam removal should be assessed on a case by case basis where the potential of sedimentary contaminant redistribution upon dam removal exists.     

Altitude profiles of total chlorinated paraffins in humus and spruce needles from the Alps (MONARPOP)

Chlorinated paraffins (CPs) are toxic, bioaccumulative, persistent, and ubiquitously present in the environment. CPs were analyzed in humus and needle samples, which were taken within the Monitoring Network in the Alpine Region for Persistent and other Organic Pollutants (MONARPOP) at sampling sites of 7 different altitude profiles in the Alps. Gas chromatography combined with electron ionization tandem mass spectrometry (EI-MS/MS) was used for the determination of total CPs (sum of short, medium and long chain CPs). CPs were found in all samples; the concentrations varied between 7 and 199 ng g⁻¹ dry weight (dw) and within 26 and 460 ng g⁻¹ dw in humus and needle samples, respectively. A clear vertical tendency within the individual altitude profiles could not be ascertained. Within all altitude profiles, elevated concentrations were observed in humus samples taken between 700 and 900 m and between 1300 and 1500 m. In the needle samples no similar correlation could be observed due to higher variation of the data.     

Determining the Chernobyl impact on sediments of a pre-Alpine lake with a very comprehensive set of data

Man-made and natural radionuclides in Lake Wallersee were determined in the pre-Alpine environment at the northern slope of the Alps, which was heavily affected by the Chernobyl fallout in May 1986. The objective of this study was to get knowledge of location and quantity of man-made radionuclide input (especially (137)Cs) generated in the Chernobyl accident to lake sediments. Eleven sediment cores were sampled and activity depth profiles of (137)Cs and (210)Pb were determined with 5mm depth-resolution. The Chernobyl fallout produced an extreme (137)Cs peak in the sediment cores providing an excellent time marker. The chronological interpretation of deeper sediment layers was done by radiochemical analysis of (90)Sr and (239+240)Pu, which were released during atmospheric weapons' tests in the 1950s and 1960s. This allowed a complete chronological analysis of the sediment cores with a very compact set of data.     

Identification of carbonaceous geosorbents for PAHs by organic petrography in river floodplain soils

Organic petrographic analysis was applied to provide direct information on carbonaceous geosorbents for PAHs in river floodplain soils. The anthropogenic OM group (primarily coal and coal-derived particles) displayed large volume amounts for all the soil samples. Distinct PAH concentrations with similar PAH distribution patterns were determined in grain size and density fractions for each sample. Two-ring PAHs had stronger correlation to organic carbon (OC) than black carbon (BC) contents, while heavier PAHs showed correlation to BC, rather than OC. In this study, we combined grain size and density separation, PAH determinations, TOC and BC measurements, and organic petrographic identification, and concluded that two-ring PAHs in soils were associated to coal particles. Other heavier PAHs could be more controlled by black carbon (BC), which were mostly coal-derived particles from former coal mining and coal industrial activity.     

Colloid facilitated transport of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) to the groundwater at Ma Da Area, Vietnam

PCDD/Fs are hydrophobic organic substances and strongly sorbing to soil particles. Once adsorbed to soil particles they are believed to be virtually immobile. However, research in the last decades confirmed that strong sorbing contaminants may reach the groundwater via colloid-facilitated transport. This pathway has not been investigated before in Vietnam. Ma Da area, 100 km north of Ho Chi Minh City, was repeatedly sprayed during the Vietnam War (1962–1971) with herbicides like Agent Orange containing, beside others, the teratogenic contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). 11 surface soil samples and 12 water samples were collected in Ma Da area for analysis of PCDD/Fs in solids. Soil TCDD concentrations ranged from 1–41 ppt with a mean of 8.8 ppt and a mean I-TEQ of 9.7 ppt. Two surface water samples showed colloid bound TCDD (7 and 19 ppt). Groundwater samples showed elevated colloid bound PCDD concentrations (mean 770 ng/kg), mainly octachlorodibenzo-p-dioxin. Groundwater colloids separated by filtration did not show any TCDD. The results support that TCDD/Fs can be relocated from the top soil to the groundwater by colloidal pathway. They did not provide evidence that the dioxins bound to groundwater colloids are leftovers from the Second Indochinese War. However, this study reinforces that the colloidal transport pathway has to be included investigating the relocation of strong sorbing organic contaminants.     

Polybrominated diphenyl ether in sewage sludge in Germany

Sewage sludge samples from 11 municipal waste water treatment plants in Germany were collected from March 2002 to June 2003. Total Tri- to HpBDE concentrations (sum of significant congeners BDE 28, 47, 99, 153, 154 and 183) ranged from 12.5 to 288 (median 108) and DeBDE (BDE 209) concentrations from 97.1 to 2217 (median 256) ng/gd.m. BDE 209 dominated the congener profile. A significant change of the Tri- to HpBDE congener profile (% of total BDE 28, 47, 99, 153, 154, 183 without 209) in sludge from different stages of the waste water treatment process (primary sludge, secondary excess sludge and (dewatered) digested sludge), indicating a degradation of DeBDE to these congeners, was not observed.