Engineered nanomaterials (ENMs) increasingly used in commercial products can accumulate in biosolids. Land application of biosolids potentially leads to consequent exposure of ENMs to soils. This article examines the impact of ENM-amended biosolids on biological carbon dioxide production in soils. ENMs, including nano-silver (Ag), zinc oxide (ZnO), titanium dioxide (TiO2), and cerium oxide (CeO2), were applied to soils with dosages of 1 and 1,000 mg/kg, simulating the normal and high concentration exposure scenarios, respectively. Under dark conditions, 1,000 mg/kg of nano-Ag and ZnO exhibited inhibitory effects on aerobic carbon conversion in both a 28-day basal respiration test and a modified 24-h substrate-induced respiration (SIR) test. At 1 and 1,000 mg/kg levels, nano-TiO2 was found to be inert to carbon conversion in both respiration tests. Nano-CeO2 at 1,000 mg/kg exhibited an increased basal respiration rate (48% higher than in the control soil), but having a minimum inhibitory effect in the SIR test. Single particle-inductively coupled plasma–mass spectrometry was used to determine the presence of nano-sized particles in water extracted from soils after 28 days of respiration test. Soils treated with nano-TiO2, CeO2, and Ag released<1% of nanoparticles into the extracted water, while the majority of ENMs were still retained in the soil. Nano- and micron-sized particles containing zinc were not detected even in soils treated with 1,000 mg/kg of nano-ZnO. The findings of this article will inform scientific and regulatory communities about the potential effects of ENMs on microbial respiration in biosolid-amended soils.
Each year vehicular accidents cause gasoline and diesel spills on Arizona roadways. ADOT currently uses Micro-Blaze®, a commercially available microbial solution, as a supplement to natural degradation of vehicular petroleum spills in soils. With an emphasis on minimizing or eliminating environmental and public health hazard, ADOT is interested in determining cost-effective methods to address spills involving petroleum products from roadway vehicular accidents. This study investigated whether Micro-Blaze, Hydro Clean®, Miracle-Gro®, or water accelerated the degradation process significantly over natural processes and if it will help to determine their effectiveness in accelerating the remediation of petroleum products (diesel No. 2 and unleaded gasoline) on predominant Arizona soil types from roadway vehicular accidents. The soil types evaluated were aridisols from Burro Creek, alfisols from Show Low, and entisols from Mesa. All three soil types contaminated with gasoline showed a reduction in BTEX levels to below ADEQ’s SRLs within 21 days, even in the absence of added microorganisms or nutrients. In none of the sample treatments was the diesel (total petroleum hydrocarbon) concentration below either residential or non-residential SRLs by day 83. The results are discussed referencing ADEQ’s SRL in effect for 2006; ADEQ changed SRLs in 2007. When compared to the new 2007 levels, BTEX are below SRL and there is no longer an ADEQ SRL for total petroleum hydrocarbon.
Potential health implications of deficient sanitation infrastructure and reduced surface water flows due to climate change are examined in the case study of the Republic of Macedonia. Changes in surface water flows and wastewater discharges over the period 1955-2013 were analyzed to assess potential future surface water contamination trends. Simple model predictions indicated a decline in surface water hydrology over the last half century, which caused the surface waters in Macedonia to be frequently dominated by >50% of untreated sewage discharges. The surface water quality deterioration is further supported by an increasing trend in modeled biochemical oxygen demand trends, which correspond well with the scarce and intermittent water quality data that are available. Facilitated by the climate change trends, the increasing number of severe weather events is already triggering flooding of the sewage-dominated rivers into urban and non-urban areas. If efforts to develop a comprehensive sewage collection and treatment infrastructure are not implemented, such events have the potential to increase public health risks and cause epidemics, as in the 2015 case of a tularemia outbreak.
