Wastewater Flow and Pathogen Transport from At-Grade Line Sources to Shallow Groundwater.

On-site wastewater treatment systems are commonly used in sparsely populated areas where capital-intensive centralized wastewater treatment facilities are not feasible. The primary objective of this work was to investigate vadose zone and groundwater transport of a bromide (Br) tracer and naturally occurring applied to the soil surface in secondarily treated wastewater at a public rest stop in central Alberta, Canada, with seasonally fluctuating water table (between 0.2 and 1.5 m) over a 1-yr period. A transect within the wastewater application field was instrumented with 10 nests of three monitoring wells ( = 30). We found that travel times for Br and were most likely related to vadose zone thickness under wastewater application lines, with Br and initially detected in monitoring wells within 4 d at locations where the vadose zone was 0.2 to 0.4 m thick. When the vadose zone thickness increased to ≥0.9 m, however, levels in the monitoring wells decreased dramatically despite continued high surface application of . The observed travel times were consistent with those calculated assuming piston flow. Therefore, the risk of groundwater contamination from wastewater at this site is greatest during times when high wastewater applications (high facility use) and shallow water table conditions coincide. We recommend that detailed knowledge of vadose zone and groundwater hydrology be used to guide the design of on-site wastewater treatment systems and also to assess the probability of human exposure to and other pathogens that are transported to groundwater.

Arsenic Metabolites, Including N-Acetyl-4-hydroxy-m-arsanilic Acid, in Chicken Litter from a Roxarsone-Feeding Study Involving 1600 Chickens.

The poultry industry has used organoarsenicals, such as 3-nitro-4-hydroxyphenylarsonic acid (Roxarsone, ROX), to prevent disease and to promote growth. Although previous studies have analyzed arsenic species in chicken litter after composting or after application to agricultural lands, it is not clear what arsenic species were excreted by chickens before biotransformation of arsenic species during composting. We describe here the identification and quantitation of arsenic species in chicken litter repeatedly collected on days 14, 24, 28, 30, and 35 of a Roxarsone-feeding study involving 1600 chickens of two strains. High performance liquid chromatography separation with simultaneous detection by both inductively coupled plasma mass spectrometry and electrospray ionization tandem mass spectrometry provided complementary information necessary for the identification and quantitation of arsenic species. A new metabolite, N-acetyl-4-hydroxy-m-arsanilic acid (N-AHAA), was identified, and it accounted for 3-12% of total arsenic. Speciation analyses of litter samples collected from ROX-fed chickens on days 14, 24, 28, 30, and 35 showed the presence of N-AHAA, 3-amino-4-hydroxyphenylarsonic acid (3-AHPAA), inorganic arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMA(V)), dimethylarsinic acid (DMA(V)), and ROX. 3-AHPAA accounted for 3-19% of the total arsenic. Inorganic arsenicals (the sum of As(III) and As(V)) comprised 2-6% (mean 3.5%) of total arsenic. Our results on the detection of inorganic arsenicals, methylarsenicals, 3-AHPAA, and N-AHAA in the chicken litter support recent findings that ROX is actually metabolized by the chicken or its gut microbiome. The presence of the toxic metabolites in chicken litter is environmentally relevant as chicken litter is commonly used as fertilizer.

Arsenic fractionation and mineralogical characterization of sediments in the Cold Lake area of Alberta, Canada.

Elevated arsenic (As >0.01 mg L(-1)) in some domestic well water in the Cold Lake area of Alberta, Canada is of great concern for public health. To determine possible sources of groundwater As, sediments (n=135) collected from five different locations (up to ~300 m depth) in the area were characterized. Total As concentrations in the sediments varied from ~1 to 35 mg kg(-1). Sediments derived from shale contained high As (~13 mg kg(-1); n=14), particularly the shale of Lea Park formation where maximum average As was ~32 mg kg(-1) (n=2). Unoxidized sediments of Grand Centre (24.9 ± 4.2 mg kg(-1) As) and Bonnyville (19.9 ± 1.8 mg kg(-1) As) formations also contained high As. Sequential extraction procedure (SEP) revealed the dominance of exchangeable and specifically adsorbed As (6 to 46% of total As) in the sediments of varying As concentrations (0.8 to 35.4 mg kg(-1) As). The high As sediments (>7 mg kg(-1) As) also contained significant amount of sulfide bound As (11 to 34% of total As), while low As (<7 mg kg(-1) As) sediments had crystalline oxide minerals bound As (25 to 75% of total As) as major phases. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the presence of pyrite, and µ-XRD analysis signaled the presence of arsenopyrite in sediments containing ~20 mg kg(-1) As. X-ray absorption near edge structure (XANES) spectroscopy analysis suggested dominance of arsenite (AsIII; ~60 to 90% of total As) in all the sediments. These findings may help to devise strategies to investigate mechanisms of As release into the groundwater.

A modified sequential extraction method for arsenic fractionation in sediments.

A modified sequential extraction method was developed to characterize arsenic (As) associated with different solid constituents in surficial deposits (sediments), which are unconsolidated glacial deposits overlying bedrock. Current sequential extraction methods produce a significant amount of unresolved As in the residual fraction, but our proposed scheme can fractionate >90% of the As present in sediments. Sediment samples containing different As concentrations (3-35 µg g(-1)) were used to assess the developed method. The pooled amount of As recovered from all the fractions using the developed method was similar (83-122%) to the total As extracted by acid digestion. The concentrations of As in different fractions using the developed scheme were comparable (89-106%) to the As fractions obtained by other existing methods. The developed method was also evaluated for the sequential extraction of other metals such as copper (Cu), cobalt (Co), chromium (Cr) and strontium (Sr) in the sediment samples. The pooled concentrations of these four individual metals from all the fractions were similar (96-104%) to their total concentrations extracted by acid digestion. During method development, we used extractants that did not contain chloride to eliminate formation of polyatomic ions of argon chloride ((40)Ar(35)Cl) that interfered with (75)As when analyzed using inductively coupled plasma mass spectrometer (ICP-MS). The results suggest that the developed method can reliably be employed for complete As and other metals' fractionation in sediments using ICP-MS.