Covalently linked immunomagnetic separation/adenosine triphosphate technique (Cov-IMS/ATP) enables rapid, in-field detection and quantification of Escherichia coli and Enterococcus spp. in freshwater and marine environments.

AIMS: Developing a rapid method for detection of faecal pollution is among the critical goals set forth by the Environmental Protection Agency in its revision of water quality criteria. The purpose of this study is to devise and test covalently linked antibody-bead complexes for faecal indicator bacteria (FIB), specifically Escherichia coli or Enterococcus spp., in measuring water quality in freshwater and marine systems. METHODS AND RESULTS: Covalently linked complexes were 58-89% more robust than antibody-bead complexes used in previous studies. Freshwater and marine water samples analysed using covalently linked immunomagnetic separation/adenosine triphosphate quantification technique (Cov-IMS/ATP) and culture-based methods yielded good correlations for E. coli (R = 0·87) and Enterococcus spp. (R = 0·94), with method detection limits below EPA recreational water quality health standards for single standard exceedances (E. coli- 38 cells per 100 ml; Enterococcus spp. - 25 cells per 100 ml). Cov-IMS/ATP correctly classified 87% of E. coli and 94% of Enterococcus spp. samples based on these water quality standards. Cov-IMS/ATP was also used as a field method to rapidly distinguish differential loading of E. coli between two stream channels to their confluence. CONCLUSIONS: Cov-IMS/ATP is a robust, in-field detection method for determining water quality of both fresh and marine water systems as well as differential loading of FIB from two converging channels. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first work to present a viable rapid, in-field assay for measuring FIB concentrations in marine water environments. Cov-IMS/ATP is a potential alternative detection method, particularly in areas with limited laboratory support and resources, because of its increased economy and portability.

Faecal indicator bacteria enumeration in beach sand: a comparison study of extraction methods in medium to coarse sands.

AIMS: The absence of standardized methods for quantifying faecal indicator bacteria (FIB) in sand hinders comparison of results across studies. The purpose of the study was to compare methods for extraction of faecal bacteria from sands and recommend a standardized extraction technique. METHODS AND RESULTS: Twenty-two methods of extracting enterococci and Escherichia coli from sand were evaluated, including multiple permutations of hand shaking, mechanical shaking, blending, sonication, number of rinses, settling time, eluant-to-sand ratio, eluant composition, prefiltration and type of decantation. Tests were performed on sands from California, Florida and Lake Michigan. Most extraction parameters did not significantly affect bacterial enumeration. anova revealed significant effects of eluant composition and blending; with both sodium metaphosphate buffer and blending producing reduced counts. CONCLUSIONS: The simplest extraction method that produced the highest FIB recoveries consisted of 2 min of hand shaking in phosphate-buffered saline or deionized water, a 30-s settling time, one-rinse step and a 10 : 1 eluant volume to sand weight ratio. This result was consistent across the sand compositions tested in this study but could vary for other sand types. SIGNIFICANCE AND IMPACT OF THE STUDY: Method standardization will improve the understanding of how sands affect surface water quality.

Pilot- and bench-scale testing of faecal indicator bacteria survival in marine beach sand near point sources.

AIM: Factors affecting faecal indicator bacteria (FIB) and pathogen survival/persistence in sand remain largely unstudied. This work elucidates how biological and physical factors affect die-off in beach sand following sewage spills. METHODS AND RESULTS: Solar disinfection with mechanical mixing was pilot-tested as a disinfection procedure after a large sewage spill in Los Angeles. Effects of solar exposure, mechanical mixing, predation and/or competition, season, and moisture were tested at bench scale. First-order decay constants for Escherichia coli ranged between -0.23 and -1.02 per day, and for enterococci between -0.5 and -1.0 per day. Desiccation was a dominant factor for E. coli but not enterococci inactivation. Effects of season were investigated through a comparison of experimental results from winter, spring, and fall. CONCLUSIONS: Moisture was the dominant factor controlling E. coli inactivation kinetics. Initial microbial community and sand temperature were also important factors. Mechanical mixing, common in beach grooming, did not consistently reduce bacterial levels. SIGNIFICANCE AND IMPACT OF THE STUDY: Inactivation rates are mainly dependent on moisture and high sand temperature. Chlorination was an effective disinfection treatment in sand microcosms inoculated with raw influent.

The impact of sewage irrigation on the uptake of mercury in corn plants (Zea mays) from suburban Beijing.

The impact of sewage irrigation on the uptake and translocation of mercury (Hg) in corn plants (Zea mays) was investigated. Corn plants were harvested the same day from two nearby fields in suburban Beijing, one irrigated historically with sewage effluent, and one irrigated solely with groundwater. Hg content was analyzed in the soil, roots and stems, while percent moisture and soil organic content were analyzed in the soil samples. The concentration of Hg in the soil and roots, and the soil organic content were not significantly different between the two fields, despite the historic practice of sewage irrigation. Hg content in roots was positively correlated with soil Hg concentration (r=0.95, n=6). The transfer coefficients between roots and stems were significantly higher in the control site (control: 2.06, sewage-irrigated: 0.44, p<0.05), indicating that the barrier effect of the roots was not consistent between the two fields.

Controls on arsenic speciation and solid-phase partitioning in the sediments of a two-basin lake.

Arsenic (As) regeneration from sediments of Spy Pond, a two-basin lake near Boston, MA, continues to result in seasonally elevated As levels despite the several decades that have elapsed since the pond's historical contamination by a pulse input of As. Solid-phase speciation and partitioning of As in the sediments appear to be primary determinants of both potential As regeneration rate and, conversely, the rate at which long-term burial of the pond's As burden will occur. Although iron (Fe) chemistry often controls As speciation in lakes, a higher rate of As regeneration in the south basin, accompanied by the absence of a correlation between regenerated As and Fe in this basin, suggest that additional factors operate to control As cycling in this lake. Solid-phase As speciation was remarkably similar between sediments of the two basins of this lake, about 40% of sedimentary As in upper sediments being in relatively labile (ionically bound and strongly adsorbed) fractions and a larger fraction of As being associated with recalcitrant minerals, likely sulfides. Extraction, X-ray fluorescence, and acid-volatile sulfide data collectively suggest that sedimentary As cycling in both basins is largely controlled by the formation of sulfide minerals. An accounting of the size of sulfur (S) pools supports this conclusion, showing that sufficient S exists in the north basin to control both Fe and As, while the south basin has lower S levels resulting in seasonal accumulation of Fe in the porewater.

Developmental effects of pcbs on the hard clam (Mercenaria mercenaria).

Development of hard clam (Mercenaria mercenaria) larvae was examined as a potential biomarker of exposure to polychlorinated biphenyls (PCBs). Clams from clean sites in Massachusetts Bay were thermally induced to spawn in the laboratory using seawater, and the gametes were collected and pooled by sex prior to fertilization. The larvae were cultured in seawater amended with Aroclor 1254, at concentration ranges bracketing environmentally relevant levels. A dose-response relationship was observed for larval development in the presence of Aroclor 1254; at higher doses, fewer larvae developed to the normal straight-hinge, or D-shaped stage, relative to the controls, while the number of abnormally shaped larvae increased.

Capping efficiency for metal-contaminated marine sediment under conditions of submarine groundwater discharge.

Theoretical estimations and laboratory studies suggest that capping can effectively retard contaminant transport from sediments under undisturbed conditions. However, contaminated near-shore areas, commonly selected as capping sites, are frequently subjected to submarine groundwater discharge (SGD). Column experiments were set up in the laboratory to simulate metal transport through sediment and capping material in the presence and absence of SGD. In the absence of SGD, capping enhanced Mo flux and initial Mn flux while having no effect in retarding Fe flux, presumably due to altered redox conditions. This effect was more pronounced in the presence of SGD (4.7 x 10(-4) m/h specific discharge). Capping enhanced Cd flux and initial fluxes of Ni, Cu, and Zn under conditions of simulated SGD, which may be caused by co-transport with Mn and Fe and oxidation of sulfide. Capping retarded Cr and Pb fluxes and steady-state Ni, Cu, Zn, and Fe fluxes in the presence of simulated SGD. However, capping efficiency decreased relative to that with no SGD. Elevated Mn concentration was detected at the capping surface with simulated SGD. Results indicate that advective flow may lead to significantly higher metal fluxes than those under undisturbed conditions.

Evaluation of environmental effects on metal transport from capped contaminated sediment under conditions of submarine groundwater discharge.

Previous studies conducted in our laboratories have shown that submarine groundwater discharge (SGD) can significantly increase metal fluxes from capped contaminated sediment to the overlying water. Five columns were set up in the laboratory to evaluate the effects of environmental factors such as groundwater pH, sediment depth, and groundwater flow rate on metal transport from capped contaminated sediment under conditions of SGD. Acidified groundwater discharge was shown to enhance the mobility of all tested metals except Mo. Although much of the released metal was adsorbed by the capping material, significant increases of initial or steady-state fluxes to the overlying water were observed for Ni, Cu, Zn, Cd, Pb, and Mn. Additional sediment depth enhanced steady-state fluxes for all tested metals except Mo, Cd, and Pb. Increased SGD rates did not significantly change the average metal concentration in the outflow to the overlying water for most metals; however, all metal releases were higher due to the greater flow at increased SGD rates. The residence time and the redox conditions may be important in evaluating environmental effects on capping efficiency.