Assessment of atmospheric metal pollution in the urban area of Mexico City, using Ficus benjamina as biomonitor.

Concentrations of vanadium, chromium, cobalt, nickel, copper, zinc, antimony, and lead were measured in Ficus benjamina leaves from the Mexico City urban area in order to assess their enrichment against background values. The instrumental analysis was performed using inductively coupled plasma mass spectrometry and the analytical method was tested using two certified reference materials from the National Institute of Standards and Technology (1547 Peach Leaves and 1573a Tomato Leaves). Enrichment factors were calculated, i.e., total to background concentration ratio, for each metal. Low enrichments of vanadium, cobalt, nickel, and copper (≈2), and mild enrichments of chromium and zinc (4.4, 4.5 respectively) were found in the entire area; oppositely, high enrichments were assessed for antimony (28.6) and lead (17.2). However, results indicate that metal concentrations strongly depend on the specific urban sub-area. Increments of metals were attributed to natural, vehicular, and industrial sources.

Ignitions explain more than temperature or precipitation in driving Santa Ana wind fires.

Autumn and winter Santa Ana wind (SAW)-driven wildfires play a substantial role in area burned and societal losses in southern California. Temperature during the event and antecedent precipitation in the week or month prior play a minor role in determining area burned. Burning is dependent on wind intensity and number of human-ignited fires. Over 75% of all SAW events generate no fires; rather, fires during a SAW event are dependent on a fire being ignited. Models explained 40 to 50% of area burned, with number of ignitions being the strongest variable. One hundred percent of SAW fires were human caused, and in the past decade, powerline failures have been the dominant cause. Future fire losses can be reduced by greater emphasis on maintenance of utility lines and attention to planning urban growth in ways that reduce the potential for powerline ignitions.

Hot and cold flavors of southern California's Santa Ana winds: their causes, trends, and links with wildfire.

Santa Ana winds (SAWs) are associated with anomalous temperatures in coastal Southern California (SoCal). As dry air flows over SoCal's coastal ranges on its way from the elevated Great Basin down to sea level, all SAWs warm adiabatically. Many but not all SAWs produce coastal heat events. The strongest regionally averaged SAWs tend to be cold. In fact, some of the hottest and coldest observed temperatures in coastal SoCal are linked to SAWs. We show that hot and cold SAWs are produced by distinct synoptic dynamics. High-amplitude anticyclonic flow around a blocking high pressure aloft anchored at the California coast produces hot SAWs. Cold SAWs result from anticyclonic Rossby wave breaking over the northwestern U.S. Hot SAWs are preceded by warming in the Great Basin and dry conditions across the Southwestern U.S. Precipitation over the Southwest, including SoCal, and snow accumulation in the Great Basin usually precede cold SAWs. Both SAW flavors, but especially the hot SAWs, yield low relative humidity at the coast. Although cold SAWs tend to be associated with the strongest winds, hot SAWs tend to last longer and preferentially favor wildfire growth. Historically, out of large (> 100 acres) SAW-spread wildfires, 90% were associated with hot SAWs, accounting for 95% of burned area. As health impacts of SAW-driven coastal fall, winter and spring heat waves and impacts of smoke from wildfires have been recently identified, our results have implications for designing early warning systems. The long-term warming trend in coastal temperatures associated with SAWs is focused on January-March, when hot and cold SAW frequency and temperature intensity have been increasing and decreasing, respectively, over our 71-year record. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00382-021-05802-z.

Spatial distribution of heavy metals in top soils around the industrial facilities of Cromatos de México, Tultitlan Mexico.

The environmental damage caused by industrial activities in Cromatos de México, (Tultitlán, México) has been evaluated in terms of heavy metal concentrations in topsoils of the surrounding area. The concentrations of lead, copper and zinc demonstrate a significant enrichment with respect to unpolluted levels. Their maximum enrichment factors are 37.7, 21.1 and 9.6 mg kg⁻¹, respectively; such increase is related to traffic emissions. Nickel concentrations show no significant difference in the analyzed samples. Total chromium concentrations show a significant decrease with distance from the industrial facilities, ranging from 15 to 1,837 mg kg⁻¹. The enrichment factors of chromium (total), with respect to the background values reach up to 40.8 mg kg⁻¹. In spite of this pronounced increase, only three analyzed samples show chromium (VI) concentrations over 0.5 mg kg⁻¹ (instrumental detection limit) and do not exceed the values recommended by the Mexican official norm. The current results show that the chromium present in the studied area does not represent serious health risks and environmental damage in the zone, nevertheless, it is necessary to consider that the oxidation of chromium (III) is determinate by changes in redox and/or pH conditions which would imply significant impacts upon its toxic risk. This study suggests that the waste material generated during the industrial activities of Cromatos de Mexico represents a relevant metal pollution source for the area even 30 years after the closure of the industrial facilities.

Santa Ana Winds of Southern California Impact PM2.5 With and Without Smoke From Wildfires.

Fine particulate matter (PM2.5) raises human health concerns since it can deeply penetrate the respiratory system and enter the bloodstream, thus potentially impacting vital organs. Strong winds transport and disperse PM2.5, which can travel over long distances. Smoke from wildfires is a major episodic and seasonal hazard in Southern California (SoCal), where the onset of Santa Ana winds (SAWs) in early fall before the first rains of winter is associated with the region's most damaging wildfires. However, SAWs also tend to improve visibility as they sweep haze particles from highly polluted areas far out to sea. Previous studies characterizing PM2.5 in the region are limited in time span and spatial extent, and have either addressed only a single event in time or short time series at a limited set of sites. Here we study the space-time relationship between daily levels of PM2.5 in SoCal and SAWs spanning 1999-2012 and also further identify the impact of wildfire smoke on this relationship. We used a rolling correlation approach to characterize the spatial-temporal variability of daily SAW and PM2.5. SAWs tend to lower PM2.5 levels, particularly along the coast and in urban areas, in the absence of wildfires upwind. On the other hand, SAWs markedly increase PM2.5 in zip codes downwind of wildfires. These empirical relationships can be used to identify windows of vulnerability for public health and orient preventive measures.

Heat, Disparities, and Health Outcomes in San Diego County's Diverse Climate Zones.

Climate variability and change are issues of growing public health importance. Numerous studies have documented risks of extreme heat on human health in different locations around the world. Strategies to prevent heat-related morbidity and reduce disparities are possible but require improved knowledge of health outcomes during hot days at a small-scale level as important within-city variability in local weather conditions, socio-demographic composition, and access to air conditioning (AC) may exist. We analyzed hospitalization data for three unique climate regions of San Diego County alongside temperature data spanning 14 years to quantify the health impact of ambient air temperature at varying exceedance threshold levels. Within San Diego, coastal residents were more sensitive to heat than inland residents. At the coast, we detected a health impact at lower temperatures compared to inland locations for multiple disease categories including heat illness, dehydration, acute renal failure, and respiratory disease. Within the milder coastal region where access to AC is not prevalent, heat-related morbidity was higher in the subset of zip codes where AC saturation is lowest. We detected a 14.6% increase (95% confidence interval [4.5%, 24.6%]) in hospitalizations during hot weather in comparison to colder days in coastal locations where AC is less common, while no significant impact was observed in areas with higher AC saturation. Disparities in AC ownership were associated with income, race/ethnicity, and homeownership. Given that heat waves are expected to increase with climate change, understanding health impacts of heat and the role of acclimation is critical for improving outcomes in the future.