Daily Archives: September 13, 2013

Naegleria fowleri found in a Louisiana water supply

“Tests of a Louisiana parish’s water supply confirmed the presence of a rare brain-eating amoeba blamed for last month’s death of a 4-year-old boy.” Click here for news article….

Natural climate variability responsible for current annual-mean global temperature hiatus

Yu Kosaka, Shang-Ping Xie. Recent global-warming hiatus tied to equatorial Pacific surface cooling. Nature(2013)doi:10.1038/nature12534

Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming, but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970–2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA. Our results show that the current hiatus is part of natural climate variability, tied specifically to a La-Niña-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.

Click here for full paper (fee).

Removal of engineered nanoparticles by water treatment

Talia E. Abbott Chalew, Gaurav S. Ajmani, Haiou Huang, and Kellogg J. Schwab. Evaluating Nanoparticle Breakthrough during Drinking Water Treatment. Environ Health Perspect; DOI:10.1289/ehp.1306574

Background: Use of engineered nanoparticles (NPs) in consumer products is resulting in NPs entering drinking water sources. Subsequent NP breakthrough into treated drinking water is a potential exposure route and human health threat.

Objectives: This study investigated the breakthrough of common NPs, silver, titanium dioxide (TiO2), and zinc oxide (ZnO), into finished drinking water following conventional and advanced treatment.

Methods: NPs were spiked into five experimental waters: groundwater, surface water, synthetic freshwater, synthetic freshwater with natural organic matter, and tertiary wastewater effluent. Bench scale coagulation/flocculation/sedimentation simulated conventional treatment, and microfiltration (MF) and ultrafiltration (UF) simulated advanced treatment. Breakthrough of NPs into treated water was monitored by turbidity removal and inductively coupled plasma – mass spectrometry (ICP-MS).

Results: Conventional treatment resulted in 2-20%, 3-8%, and 48-99% of silver, TiO2, and ZnO NPs or their dissolved ions remaining in finished water, respectively. Breakthrough following MF was 1-45% for silver, 0-44% for TiO2, and 36-83% for ZnO. With UF, NP breakthrough was 0-2%, 0-4%, and 2-96% for silver, TiO2, and ZnO, respectively. Variability was dependent on NP stability with less breakthrough of aggregated NPs compared to stable NPs and dissolved NP ions.

Conclusions: Although a majority of aggregated or stable NPs were removed by simulated conventional and advanced treatment, NP metals were detectable in finished water. As environmental NP concentrations increase, we need to consider NPs as emerging drinking water contaminants, and determine appropriate drinking water treatment processes to fully remove NPs in an effort to reduce their potential harmful health outcomes.

Click here for full paper (Open Source).