A G Manuel Leiva

Ozone weekend effect in Santiago, Chile

The study examined weekday-weekend differences in ozone, NO(x) (NO and NO(2)) and VOC concentrations in Santiago, Chile, from 1999 to 2007. The results provide evidence for the occurrence of an atmospheric phenomenon that produces higher ozone concentrations during weekends despite lower concentrations of ozone precursors. This phenomenon is known as the weekend effect (WE). The overall ozone decrease since the spring of 2004 was a consequence of the implementation of several urban pollution control measures. Although these measures caused a decline in the number of days that exceed the national standard from two-thirds to one-third of summer days, the WE, which became statistically significant beginning in September 2004, could not be eliminated. Furthermore, VOC/NO(x) ratios decreased during the same period (2004), especially in the most industrialized area of Santiago. Similarly, under these regimes, the VOC/NO(x) ratios were higher on Sundays than on weekdays and caused higher ozone concentrations on Sundays.

Environmental assessment of mercury pollution in urban tailings from gold mining

It is well-known that small-scale artisanal mining is a source of mercury emissions into the environment, mainly from the use of rudimentary technologies that use mercury amalgamation in the extraction process. Mines near Andacollo, which is located in the Coquimbo region of Chile, use primitive methods to mine gold and copper. In this study, we determined the mercury content of gold mining wastes from Andacollo. At each site, we randomly sampled the soil at the surface and at a depth of 2 m following the ISO 10381 guidelines. Mercury analysis was performed with a direct mercury analyzer. At least one site was contaminated at a mercury concentration of 13.6±1.4 mg kg(-1), which was above the international recommendations that were set by the Canadian Council of Ministers of the Environments soil quality guidelines (CA-SQG) and the Dutch guidelines (NL-RIVM). At least four of the fourteen sites in this study were within the control and tolerance levels of these recommendations. Better characterization of these sites is required to establish whether they represent a risk to the local community. Based on the US-EPA recommendations, which have a higher tolerance limit, none of the fourteen sites should pose a risk to humans.

Uncertainty estimation of anions and cations measured by ion chromatography in fine urban ambient particles (PM 2.5 )

The present work presents a measurement uncertainty evaluation according to Guide to the Expression of Uncertainty in Measurement (GUM) of the concentration of the cations K+ and Li+ and anions NO3−2 and SO4−2 in fine airborne particulate matter, refers to particles less than 2.5 μm in diameter (PM2.5), as measured by ion chromatography (US-EPA 300 method). The GUM method is not typically used to report uncertainty. In general, the analytical results only report the measurement’s standard deviation under repetition as an uncertainty; thus, not all sources of uncertainty are considered. In this work, the major sources of uncertainty regarding the measurements were identified as contributions to linear least square regression lines, repeatability, precision, and trueness. The expanded uncertainty was approximately 20% for anions and cations. The largest contribution to uncertainty was found to be repeatability.

Trends and threshold exceedances analysis of airborne pollen concentrations in Metropolitan Santiago Chile

Pollen is one of the primary causes of allergic rhinoconjunctivitis in urban centers. In the present study, the concentrations of 39 different pollens in the Santiago de Chile metropolitan area over the period 2009–2013 are characterized. The pollen was monitored daily using Burkard volumetric equipment. The contribution of each type of pollen and the corresponding time trends are evaluated. The concentrations of the pollens are compared with the established threshold levels for the protection of human health. The results show that the total amount of pollen grains originating from trees, grasses, weeds and indeterminate sources throughout the period of the study was 258,496 grains m-3, with an annual average of 51,699 ± 3,906 grains m-3 year-1. The primary source of pollen is Platanus orientalis, which produces 61.8% of the analyzed pollen. Grass pollen is the third primary component of the analyzed pollen, with a contribution of 5.82%. Among the weeds, the presence of Urticacea (3.74%) is remarkable. The pollination pattern of the trees is monophasic, and the grasses have a biphasic pattern. The trends indicate that the total pollen and tree pollen do not present a time trend that is statistically significant throughout the period of the study, whereas the grass pollen and weed pollen concentrations in the environment present a statistically significant decreasing trend. The cause of this decrease is unclear. The pollen load has doubled over the past decade. When the observed concentrations of the pollens were compared with the corresponding threshold levels, the results indicated that over the period of the study, the pollen concentrations were at moderate, high and very high levels for an average of 293 days per year. Systematic counts of the pollen grains are an essential method for diagnosing and treating patients with pollinosis and for developing forestation and urban planning strategies.

Uncertainty of ozone measurements with the primary standard reference photometer (SRP45)

A comparison of the ozone primary reference standard photometer serial number 45 (SRP45) against the National Institute of Standards and Technology (NIST) instruments, serial number 0 (SRP0) and 2 (SRP2), has been performed in order to establish the traceability and comparability of ozone measurements made by the Chilean atmospheric science community. A complete uncertainty budget was developed for SRP45, using a GUM approach. The results of the comparisons allow us to conclude that SRP45, SRP0 and SRP2 are comparable according to international criteria over an ozone mole fraction range of 0 nmol mol(-1) to at least 500 nmol mol(-1). The official result for the validation of SRP45 is x(ozone)(SRP45)=[0.013+0.99806x(ozone)(SRP2)] nmol mol(-1) with an expanded uncertainty of [Formula in text] from 0 to 500 nmol mol(-1).

Trend and recovery of the total ozone column in South America and Antarctica

South America is one of the most vulnerable areas to stratospheric ozone depletion; consequently, an increased amount of UV radiation reaches the Earth’s surface in this region. In this study, we analyzed the long-term trend in the total ozone column (TOC) over the southern part of the South American continent from 1980 to 2009. The database used was obtained by combining several satellite measurements of the TOC on a 1° (latitude) × 1.25° (longitude) grid. Analysis of the long-term trend was performed by applying the Theil-Sen estimator and the Mann–Kendall significance test to the deseasonalized time series. The long-term trend was also analyzed over several highly populated urban zones in the study area. Finally, multiple linear regression (MLR) modeling was used to identify and quantify the drivers of interannual variability in the TOC over the study area with a pixel-by-pixel approach. The results showed a decrease in the TOC ranging from −0.3 to −4% dec−1 from 1980 to 2009. On a decadal timescale, there is significant variability in this trend, and a decrease of more than −10% dec−1 was found at high latitudes (1980–1989). However, the trends obtained over much of the study area were not statistically significant. Considering the period from 1980 to 1995, we found a decrease in the TOC of −2.0 ± 0.6% dec−1 at latitudes below 40° S and −6.9 ± 2.0% dec−1 at latitudes above 40° S, for a 99.9% confidence level over most of the study area. Analysis of the period from 1996 to 2009 showed a statistically significant increase of 2.3 ± 0.1% dec−1 at high latitudes (> 60° S), confirming the initial TOC recovery in the Antarctic. Despite evidence for initial recovery of the TOC in some parts of the study area between 1996 and 2009, the long-term increase from September to November is not yet statistically significant. In addition, large parts of the study area and most of the urban areas continue to show a decreasing trend in the TOC. The MLR results show that at high latitudes, the main driver of interannual variability in the TOC is the total effective amount of halogens, followed by the eddy heat flux.