Aberjona Watershed Research Articles

Use of physical, chemical, and biological indices to assess impacts of contaminants and physical habitat alteration in urban streams

Human activities in urban areas can lead to both chemical pollution and physical alteration of stream habitats. The evaluation of ecological impacts on urban streams can be problematic where both types of degradation occur. Effects of contaminants, for example, may be masked if stream channelization, loss of riparian vegetation, or other physical stressors exert comparable or larger influences. In the Aberjona watershed (near Boston, MA, USA), we used physical, chemical, and biological indices to discern the relative impacts of physical and chemical stressors. We used standard protocols for assessing the biological condition of low-gradient streams, sampling macroinvertebrate communities from several different habitat types (e.g., overhanging bank vegetation, undercut bank roots, and vegetation on rocks). We strengthened the linkage between chemical exposure and macroinvertebrate response by measuring metal concentrations not only in sediments from the stream bottom but also in the vegetative habitats where the macroinvertebrates were sampled. Linear regression analysis indicated that biological condition was significantly dependent (95% confidence level) on contaminants in vegetative habitats, but not on contaminants in sediments from the stream bottom. Biological condition was also significantly dependent on physical habitat quality; regression analysis on both contaminants and physical quality yielded the best regression model (r2 = 0.49). Similar biological impairment was observed at sites with severe contamination or physical impairment or with moderate chemical and physical impairment. These results have implications for the management of urban streams.

Population Dynamics of Two Toluene Degrading Bacterial Species in a Contaminated Stream.

Toluene uptake by a benthic biofilm community was previously shown to vary seasonally from 0.03 m hr?1 in winter to 0.2 m hr?1 in summer in a solvent-contaminated stream of the Aberjona watershed. We used quantitative PCR to estimate the population dynamics of previously isolated species of toluene-degrading Xanthobacter autotrophicus and Mycobacterium sp. in both toluene-contaminated and uncontaminated reaches of the stream, and to estimate their relative roles in overall biodegradation rate. Quantification using specific 16S rDNA primers forX. autotrophicus and Mycobacterium sp. showed that populations of both species were much larger in the toluene-contaminated than the toluene-free reach, in agreement with earlier culture-based investigations. A relatively brief bloom of X. autotrophicus occurred in the contaminated reach in the summer, while Mycobacterium sp. populations occurred at elevated densities for more than 5 months. Calculations showed that Mycobacterium, previously thought to be less important than Xanthobacter in annual toluene degradation based on single time-point CFU estimates, appears actually more important because of this longer persistence.

Bioaccumulation and Diminution of Arsenic and Lead in a Freshwater Food Web

This study provides strong evidence for biotic accumulation of two metals in a contaminated watershed and diminution of both metals from lower trophic levels to fish. Bioaccumulation of As and Pb in water and four food web components (particulates, two size fractions of zooplankton, and six species of fish) were measured on three dates in Upper Mystic Lake (UML), MA, which is located in the As-contaminated Aberjona Watershed. Arsenic and Pb levels in small and large plankton and fish biodiminished with increasing trophic level, but only As was elevated in lower trophic levels relative to uncontaminated food webs. Metal levels in water and biota differed by date and were lowest in the spring and, in most cases, highest in summer samples. Variation in metal accumulation in zooplankton across dates may be due to changes in metal concentrations in the aqueous and particulate phase over time. Metal burdens in fish with different feeding strategies were also compared. We found the highest As in planktivorous sp...

By-products of a former phenol manufacturing site in a small lake adjacent to a Superfund site in the Aberjona watershed.

Benzene, diphenyl sulfone (DPS), para-hydroxybiphenyl (PPP), ortho-hydroxybiphenyl (OPP), higher hydroxybiphenyls, and alkylated benzenes were found in a small lake receiving contaminated groundwater discharge from the Industri-Plex Superfund site (Woburn, MA) in the Aberjona watershed in eastern Massachusetts. All of these chemicals may derive from the former phenol manufacturing activities present at the Industri-Plex site during World War I. Concentrations up to 1660 microgram/l benzene, 450 micro/l DPS, 230 microgram/l PPP, and 100 microgram/l OPP were detected in the hypolimnion. Epilimnetic concentrations of the chemicals were significantly lower (normally < 5 microgram/l). DPS showed a distinct seasonal behavior: It was readily biodegradable during warm periods. No biodegradation was observed in the winter, leaving export to the Aberjona River as the major removal mechanism. Although benzene is known to be toxic and a human carcinogen, our results indicate that DPS, OPP, and PPP are not mutagenic in tests using human MCL-5 and h1A1v2 cell lines.

By-Products of a Former Phenol Manufacturing Site in a Small Lake Adjacent to a Superfund Site in the Aberjona Watershed

By-Products of a Former Phenol Manufacturing Site in a Small Lake Adjacent to a Superfund Site in the Aberjona Watershed

Microbial Mobilization of Arsenic from Sediments of the Aberjona Watershed

Arsenic mobilization from aquatic sediments is an issue of concern, as water-borne arsenic can migrate into pristine areas, endangering aquatic organisms and people. Such mobilization in the Aberjona Watershed has distributed nearly 20 t of arsenic throughout river and lake sediments. To gain an understanding of possible biological mechanisms contributing to this transport, mobilization of solid-phase arsenic was investigated in upper Aberjona sediment microcosms. Microcosms catalyzed rapid dissolution of arsenic from iron arsenate, a solid-phase surrogate for sedimentary arsenic, mobilizing 20−28% of the arsenic present. Sterilization prevented this transformation. Reduction of arsenate to arsenite accompanied iron arsenate dis solution, suggesting that reduction was driving dissolution. Sediment-conditioned, filter-sterilized medium showed no arsenic-transforming activity. A native enrichment culture of sulfate-reducing bacteria possessed one-fifth of the microcosm activity, while strain MIT-13, a native arsenate-reducing microorganism, showed much greater activity, dissolving 38% of the arsenic present. Furthermore, strain MIT-13 mobilized arsenic from presterilized, unamended upper Aberjona sediments. These observations indicate that a direct microbial arsenic-mobilizing activity exists in the sedi ments, show that strain MIT-13 is a strong arsenic-transforming agent native to the sediments, and suggest that dissimilatory arsenic reduction may contribute to arsenic flux from anoxic sediments in the most arsenic-contaminated region of the Aberjona Watershed.

History of Toxic Metal Discharge to Surface Waters of the Aberjona Watershed

A history of waterborne export of toxic metals from the industrial/residential Aberjona Watershed, north of Boston, MA, has been reconstructed from an analysis of sediment cores from the Upper Mystic Lake, together with historical records of industrial activity on the watershed. The lake sediments exhibit complex profiles of arsenic, cadmium, chromium, copper, lead, and zinc. These profiles are interpretable in terms of historical industrial activities on the watershed and transport via the Aberjona River to the Upper Mystic Lake. High concentrations (in excess of 1000 mg/kg arsenic and chromium) occur in two zones, at depths between 25 and 35 cm and between 50 and 70 cm in the sediments of this lake. The deeper zone corresponds to the early 1900s, a period of intense industrial activity during which chemical and leather industries are known to have made direct discharges of metals to surface waters. Sharp decreases in metals concentrations subsequently occurred as industry declined, and concurrently, muc...

Movement and distribution of arsenic in the Aberjona watershed.

The distribution and movement of arsenic was investigated on the Aberjona watershed in eastern Massachusetts for the purpose of identifying where and by what processes present and past human exposures to this element could have occurred. It was found that although most of the arsenic was originally released in the headwaters of the watershed, extensive migration had occurred, and the potential for human exposure existed far from designated hazardous waste sites. Both surface water and groundwater were found to be important transport pathways; arsenic moved between these two media at several locations in the watershed, with hydrology and concomitant redox, sorption, and alkylation processes determining the observed patterns of arsenic movement. These findings demonstrate that risk assessments or remedial investigations restricted to designated sites or properties in a watershed may yield both an inaccurate picture of the overall risks presented by a chemical and a less-than-optimum focus for remedial efforts. Since total recovery of the arsenic on this watershed is probably not feasible, cost-effective management will also depend on an adequate understanding of arsenic biogeochemistry and hydrologic transport processes at the watershed scale. Because the Aberjona Watershed is typical of many urban, industrialized areas, these results suggest that the whole watershed often defines the appropriate unit for investigation of chemical contamination in the environment.

Movement and Distribution of Arsenic in the Aberjona Watershed

Movement and Distribution of Arsenic in the Aberjona Watershed

Speciation and Fate of Arsenic in Three Lakes of the Aberjona Watershed

The speciation of arsenic in the environment is controlled by reduction, methylation, and oxidation processes and is therefore influenced by redox conditions. However, in the lakes studied, speciation was found to be far from thermodynamic equilibrium. A Superfund site is a major source of As to the watershed, with the Aberjona River being the main conduit for As found in the Mystic Lakes. Total As concentrations in the water column decrease downstream, from >100 nM in the Hall's Brook Storage Area (HBSA), where As(III) enters via reducing ground-water, to <20 nM in the Lower Mystic Lake (LML); the sediments of all the lakes are sinks for As.