Wastewater compounds are frequently detected in urban shallow groundwater. Sources include sewage or reclaimed wastewater, but origins are often unknown. In a prior study, wastewater compounds were quantified in waters sampled from shallow groundwater wells in a small coastal California city. Here, we resampled those wells and expanded sample analyses to include sewage- or reclaimed water-specific indicators, i.e. pharmaceutical and personal care product chemicals or disinfection byproducts. Also, we developed a geographic information system (GIS)-based model of sanitary sewer exfiltration probability--combining a published pipe failure model accounting for sewer pipe size, age, materials of construction, with interpolated depths to groundwater--to determine if sewer system attributes relate to wastewater compounds in urban shallow groundwater. Across the wells, groundwater samples contained varying wastewater compounds, including acesulfame, sucralose, bisphenol A, 4-tert-octylphenol, estrone and perfluorobutanesulfonic acid (PFBS). Fecal indicator bacterial concentrations and toxicological bioactivities were less than known benchmarks. However, the reclaimed water in this study was positive for all bioactivity tested. Excluding one well intruded by seawater, the similarity of groundwater to sewage, based on multiple indicators, increased with increasing sanitary sewer exfiltration probability (modeled from infrastructure within ca. 300 m of each well). In the absence of direct exfiltration or defect measurements, sewer exfiltration probabilities modeled from the collection system's physical data can indicate potential locations where urban shallow groundwater is contaminated by sewage.

The effect of surface or lattice modification of nanoparticles (NPs) on terrestrial plants is poorly understood. We investigated the impact of different zinc oxide (ZnO) NPs on green pea (Pisum sativum L.), one of the highest consumed legumes globally. Pea plants were grown for 65 d in soil amended with commercially available bare ZnO NPs (10 nm), 2 wt% alumina doped (Al2O3@ZnO NPs, 15 nm), or 1 wt% aminopropyltriethoxysilane coated NPs (KH550@ZnO NP, 20 nm) at 250 and 1000 mg NP/kg soil inside a greenhouse. Bulk (ZnO) and ionic Zn (zinc chloride) were included as controls. Plant fresh and dry biomass, changes in leaf pigment concentrations, elements (Zn, Al, Si), and protein and carbohydrate profile of green pees were quantified upon harvest at 65 days. With the exception of the coated 1000 mg/kg NP treatment, fresh and dry weight were unaffected by Zn exposure. Although, all treated plants showed higher tissue Zn than controls, those exposed to Al2O3@ZnO NPs at 1000 mg/kg had greater Zn concentration in roots and seeds, compared to bulk Zn and the other NP treatments, keeping Al and Si uptake largely unaffected. Higher Zn accumulation in green pea seeds were resulted in coated ZnO at 250 mg/kg treatments. In leaves, Al2O3@ZnO NP at 250 mg/kg significantly increased Chl-a and carotenoid concentrations relative to the bulk, ionic, and the other NP treatments. The protein and carbohydrate profiles remained largely unaltered across all treatments with the exception of Al2O3@ZnO NPs at 1000 mg/kg where sucrose concentration of green peas increased significantly, which is likely a biomarker of stress. Importantly, these findings demonstrate that lattice and surface modification can significantly alter the fate and phytotoxic effects of ZnO NPs in food crops and seed nutritional quality. To the authors' knowledge, this is the first report of a life cycle study on comparative toxicity of bare, coated, and doped ZnO NPs on a soil-grown food crop.

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