Assessing the Impacts of E. coli Laden Streambed Sediment on E. coli Loads over a Range of Flows and Sediment Characteristics

Understanding sediment Escherichia coli levels (i.e., pathogen indicators) and their contribution to the water column during resuspension is critical for predicting in‐stream E. coli levels and the potential risk to human health. The U.S. Environmental Protection Agency's current water quality testing strategies, however, rely on water borne E. coli concentrations to assess stream E. coli levels and identify impaired waters. In this work, we conducted a scenario analysis using a range of flows, sediment/water bacteria fractions, and particle sizes to which E. coli attach to assess the impact of E. coli in streambed sediments on water column E. coli levels. We used simple sediment transport theory to calculate the potential total E. coli concentrations in a stream with and without the resuspension process. Results clearly indicate that inclusion of resuspending sediment attached E. coli is necessary for watershed assessments and data on sediment attached E. coli concentrations is much needed. When neglecting the streambed sediment E. coli concentrations, the model predicted average E. coli loads of 10⁷ Colony Forming Units (CFU)/s; however, when streambed sediment E. coli concentrations were included in the model, the predictions ranged from 10¹⁰ to 10¹⁴ CFU/s. To evaluate the predictions, E. coli data in the streambed sediment and the water column were monitored in Squaw Creek, Iowa. Comparisons between measured and predicted E. coli loads yielded an R²‐value of 0.85.     

Contribution of point sources and non-point sources to nutrient and carbon loads and their influence on the trophic status of the Ganga River at Varanasi,India

To determine the possible contributions of point and non-point sources to carbon and nutrient loading in the Ganga River, we analyzed N, P, and organic carbon (OC) in the atmospheric deposits, surface runoff, and in the river along a 37-km stretch from 2013 to 2015. We also assessed the trophic status of the river as influenced by such sources of nutrient input. Although the river N, P, and productivity showed a declining trend with increasing discharge, runoff DOC and dissolved reactive phosphorus (DRP) increased by 88.05 and 122.7% between the Adpr and Rjht sites, indicating contributions from atmospheric deposition (AD) coupled with land use where agriculture appeared to be the major contributor. Point source input led to increased river concentrations of NO₃ ^?, NH₄ ⁺, DRP, and DOC by 10.5, 115.9, 115.2, and 67.3%, respectively. Increases in N, P, and productivity along the gradient were significantly negatively correlated with river discharge (p < 0.001), while river DOC and dissolved silica showed positive relationships. The results revealed large differences in point and non-point sources of carbon and nutrient input into the Ganga River, although these variations were strongly influenced by the seasonality in surface runoff and river discharge. Despite these variations, N and P concentrations were sufficient to enhance phytoplankton growth along the study stretch. Allochthonous input together with enhanced autotrophy would accelerate heterotrophic growth, degrading the river more rapidly in the near future. This study suggests the need for large-scale inter-regional time series data on the point and non-point source partitioning and associated food web dynamics of this major river system.     

Uptake and accumulation of potentially toxic metals (Zn, Cu and Pb) in soils and plants of Durgapur industrial belt

Uptake and accumulation of metals in crops may cause possible health risks through food chain. A field survey was conducted to investigate the accumulation of potentially toxic metals contamination in soil and plants irrigated with complexed industrial effluents. Concentration of Zn, Cu and Pb was 205-255,101-130,118-177 microg g(-1) in rhizosphere soils and 116-223, 57-102 and 63-95 microg g(-1) d. wt. in root and 95-186, 44-75 and 27-58 microg g(-1) d. wt. in shoot, respectively. The trend in Cu and Pb was in the order: soil > root > shoot > seed while in Zn it was soil > root > seed > shoot. Roots accumulated a larger fraction of soil Cu (70%) > Zn (67%) > Pb (54%). Bioaccumulation coefficient of soil to root ranged from 51-98 for Zn, 54-85 for Cu and 43-63 for Pb.Analysis of variance showed marginal change in bioaccumulation coefficient, noticed between plants (p > 0.05) while it varied significantly (p < 0.01) between tissues and metals. It increased from root to seed/fruit (root > shoot > seed/fruit) while decreased between metals from Zn to Pb (Zn > Cu > Pb). Out of the three, two Cu and Pb accumulated to phyotoxic levels while Zn was within threshold limit of phytotoxicity.     

Cyanobacterial flora and the physico-chemical environment of six tropical fresh water lakes of Udaipur, India

The cyanobacteria and physico-chemical environments of sic tropical fresh water lakes of Udaipur,India were investigated.These lakes receive varying nutrient inputs from different sourcesi.Altogether 51 species of cyanobacteria were recorded.Species composition varied between lakes and between seasons.Lake VI(Beghdara),which receives nutrients from natural sources only,differed considerably from the others in water chemistry and composition of dominated species.Lake Ⅱ(Swaroop Sagar),eutrophied due to sewage inputs,was species poor.Non-diazotrophs,represented by 27 species,dominated during summer.With few exceptions,N2-fixing species,bothe heterocystous and unicellular diazotrophs (represented by 24 species),were dominant during winter.Microcystis aeruginosa,Phormidium sp.and Anabaena flos-aque were ther dominant taxa of lakes characterized by sewage eutrophication.The study shows that both species diversity and community composition were affected by water chemistry.