Today, it is well known that small airborne particles are very harmful to human health. For the first time in Hawaii we have conducted an environmental pilot study of fine magnetic particles on the island of Oahu, Haw...Today, it is well known that small airborne particles are very harmful to human health. For the first time in Hawaii we have conducted an environmental pilot study of fine magnetic particles on the island of Oahu, Hawaii, of particulate matter (PM) PM = 60, PM = 10, and PM = 2.5. In order to do a rock magnetic characterization we have performed low field susceptibility vs. temperature [k-T] experiments to determine the Curie points of small particles collected from exhaust pipes, as well as from brake pads of four different types of car engines using gasoline octane ratings of 87, 89, and 92. The Curie point determinations are very well defined and range from 292<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">°</span>C through 393<span style="white-space:normal;"><span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">°</span></span>C and up to 660<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">°</span>C. In addition, we have conducted magnetic granulometry experiments on raw tobacco, burnt tobacco ashes, as well as on automotive engine exhaust, and brake pads in question. The results of the experiments show ferro and ferrimagnetic hysteresis loops with magnetic grain sizes ranging from superparamagnetic-multidomain [SP-MD], multidomain [MD] and pseudo-single domain [PSD] shown on the modified Day et al., diagram of <a href="#ref3">Dunlop (2002)</a>. Thus far, the results we have obtained from this pilot study are in agreement with other studies conducted from cigarette ashes from Bulgaria. Our results could be correlated to the traffic-related PM in Rome, Italy where the SP fraction mainly occurs as coating of MD particles originated by localized stress in the oxidized outer shell surrounding the un-oxidized core of magnetite-like grains. All these magnetic particles have been reported to be very harmful to our human bodies (i.e. brain, lungs, heart展开更多
In order to further understand the full vector excursional details of the geomagnetic field, a paleomagnetic and rock magnetic study of four sites has been conducted at the type locality of Pringle Falls, Oregon where...In order to further understand the full vector excursional details of the geomagnetic field, a paleomagnetic and rock magnetic study of four sites has been conducted at the type locality of Pringle Falls, Oregon where 827 samples were drilled and spaced along a distance of 5 km, for their detailed directional and relative paleointensity studies. The profiles have registered a high-reso- lution (>10 cm/kyr) paleomagnetic record of the excursion (ca. 211+/13 ka) as recorded by diatomaceous lacustrine sediments. Remanence as well as induced magnetization experiments to investigate the reproducibility of the signal throughout the profiles have been conducted. In addition, low-field susceptibility vs. temperature analysis was performed indicating that the main magnetic carrier is pure magnetite (Curie point 575 ℃). The magnetic grain size also has indicated Single Domain-Multi-Domain (SD-MD) magnetite. The demagnetization was done by alternating field (a.f.) experiments, and the mean directions were determined by principal component analyses. In addition, induced magnetic tests were done, such as magnetic susceptibility (x) analyses, saturation IRM, anhysteretic remanent magnetization (ARM70) as well as the normalization of J17.5 mT/ARM70 to attempt to obtain relative paleointensity records of these sediments in question. The results of the induced rock magnetic tests such as the normalization studies indicate a direct correlation between the decrease of the relative paleointensity variations (i.e. lows) with respect to the directional changes. The detailed behavior of the paleosignal is highly consistent, since they are rapidly deposited sediments providing a detailed representation of the paleofield. The dissected VGP paths in 3 different phases are highly internally consistent and are defined by clockwise and anticlockwise loops traveling from the high northern latitudes over eastern North America and the North Atlantic to South America and then to high southern latitudes. They then return to the high northern la展开更多
The Mauna Loa volcano of the Big Island of Hawaii offers the “ad-hoc” lava flows that have recorded the geomagnetic short-term behavior (<em>i.e.</em> excursions) at two key localities such as the younge...The Mauna Loa volcano of the Big Island of Hawaii offers the “ad-hoc” lava flows that have recorded the geomagnetic short-term behavior (<em>i.e.</em> excursions) at two key localities such as the younger Kahuku volcanic series (ca. ~41 ka) where 29 flows are exposed for detailed paleomagnetic sampling making up 102 meters of section where the uppermost flow sampled lies directly under the Pahala ash. The second sampling site is the Ninole volcanic series where 25 flows spanning 56 meters of section were also sampled from the northeast and southwest sides of the Kilohana Ridge. The most recent age estimate indicates that the Kahuku flows can correlate well with the transitional/excursional directional results obtained from both volcanic and deep-sea sediments of the global record of the Laschamp (ca. ~41 ka calendar years B.P) excursion and the Ninole flows which are associated to the also global Pringle Fall excursion (ca. 211 ± 13 ka) recorded at the type section.展开更多
A novel determination of the absolute paleointensity (P.I) of 28 flows that recorded Cryptochron C2r.2r-1 (ca. 2.46 ± 0.13 Ma) using the modified Thellier-Coe method was undertaken to understand the geomagnetic e...A novel determination of the absolute paleointensity (P.I) of 28 flows that recorded Cryptochron C2r.2r-1 (ca. 2.46 ± 0.13 Ma) using the modified Thellier-Coe method was undertaken to understand the geomagnetic evolution of the paleofield during an excursion with </span><span style="font-family:"">the</span><span style="font-family:""> existence of less than 10</span><span style="font-family:""> </span><span style="font-family:"">Kyrs. The successful PI determinations along the 120-meter sequential erupted flows indicate that within the truly transitional/excursional portion of the record there is a conspicuous decrease of the PI values ranging from 20 μT to low values of about 5</span><span style="font-family:""> </span><span style="font-family:"">μT. These values are comparable to lows similar to polarity transitions of the geomagnetic field. At the base of the sequence</span><span style="font-family:"">,</span><span style="font-family:""> the record shows oscillations of the paleofied ranging from 120 μT and as low as ~10</span><span style="font-family:""> </span><span style="font-family:"">μT with very variable changes of the non-transitional/excursional paleofield.展开更多
文摘Today, it is well known that small airborne particles are very harmful to human health. For the first time in Hawaii we have conducted an environmental pilot study of fine magnetic particles on the island of Oahu, Hawaii, of particulate matter (PM) PM = 60, PM = 10, and PM = 2.5. In order to do a rock magnetic characterization we have performed low field susceptibility vs. temperature [k-T] experiments to determine the Curie points of small particles collected from exhaust pipes, as well as from brake pads of four different types of car engines using gasoline octane ratings of 87, 89, and 92. The Curie point determinations are very well defined and range from 292<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">°</span>C through 393<span style="white-space:normal;"><span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">°</span></span>C and up to 660<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">°</span>C. In addition, we have conducted magnetic granulometry experiments on raw tobacco, burnt tobacco ashes, as well as on automotive engine exhaust, and brake pads in question. The results of the experiments show ferro and ferrimagnetic hysteresis loops with magnetic grain sizes ranging from superparamagnetic-multidomain [SP-MD], multidomain [MD] and pseudo-single domain [PSD] shown on the modified Day et al., diagram of <a href="#ref3">Dunlop (2002)</a>. Thus far, the results we have obtained from this pilot study are in agreement with other studies conducted from cigarette ashes from Bulgaria. Our results could be correlated to the traffic-related PM in Rome, Italy where the SP fraction mainly occurs as coating of MD particles originated by localized stress in the oxidized outer shell surrounding the un-oxidized core of magnetite-like grains. All these magnetic particles have been reported to be very harmful to our human bodies (i.e. brain, lungs, heart
文摘In order to further understand the full vector excursional details of the geomagnetic field, a paleomagnetic and rock magnetic study of four sites has been conducted at the type locality of Pringle Falls, Oregon where 827 samples were drilled and spaced along a distance of 5 km, for their detailed directional and relative paleointensity studies. The profiles have registered a high-reso- lution (>10 cm/kyr) paleomagnetic record of the excursion (ca. 211+/13 ka) as recorded by diatomaceous lacustrine sediments. Remanence as well as induced magnetization experiments to investigate the reproducibility of the signal throughout the profiles have been conducted. In addition, low-field susceptibility vs. temperature analysis was performed indicating that the main magnetic carrier is pure magnetite (Curie point 575 ℃). The magnetic grain size also has indicated Single Domain-Multi-Domain (SD-MD) magnetite. The demagnetization was done by alternating field (a.f.) experiments, and the mean directions were determined by principal component analyses. In addition, induced magnetic tests were done, such as magnetic susceptibility (x) analyses, saturation IRM, anhysteretic remanent magnetization (ARM70) as well as the normalization of J17.5 mT/ARM70 to attempt to obtain relative paleointensity records of these sediments in question. The results of the induced rock magnetic tests such as the normalization studies indicate a direct correlation between the decrease of the relative paleointensity variations (i.e. lows) with respect to the directional changes. The detailed behavior of the paleosignal is highly consistent, since they are rapidly deposited sediments providing a detailed representation of the paleofield. The dissected VGP paths in 3 different phases are highly internally consistent and are defined by clockwise and anticlockwise loops traveling from the high northern latitudes over eastern North America and the North Atlantic to South America and then to high southern latitudes. They then return to the high northern la
文摘The Mauna Loa volcano of the Big Island of Hawaii offers the “ad-hoc” lava flows that have recorded the geomagnetic short-term behavior (<em>i.e.</em> excursions) at two key localities such as the younger Kahuku volcanic series (ca. ~41 ka) where 29 flows are exposed for detailed paleomagnetic sampling making up 102 meters of section where the uppermost flow sampled lies directly under the Pahala ash. The second sampling site is the Ninole volcanic series where 25 flows spanning 56 meters of section were also sampled from the northeast and southwest sides of the Kilohana Ridge. The most recent age estimate indicates that the Kahuku flows can correlate well with the transitional/excursional directional results obtained from both volcanic and deep-sea sediments of the global record of the Laschamp (ca. ~41 ka calendar years B.P) excursion and the Ninole flows which are associated to the also global Pringle Fall excursion (ca. 211 ± 13 ka) recorded at the type section.
文摘A novel determination of the absolute paleointensity (P.I) of 28 flows that recorded Cryptochron C2r.2r-1 (ca. 2.46 ± 0.13 Ma) using the modified Thellier-Coe method was undertaken to understand the geomagnetic evolution of the paleofield during an excursion with </span><span style="font-family:"">the</span><span style="font-family:""> existence of less than 10</span><span style="font-family:""> </span><span style="font-family:"">Kyrs. The successful PI determinations along the 120-meter sequential erupted flows indicate that within the truly transitional/excursional portion of the record there is a conspicuous decrease of the PI values ranging from 20 μT to low values of about 5</span><span style="font-family:""> </span><span style="font-family:"">μT. These values are comparable to lows similar to polarity transitions of the geomagnetic field. At the base of the sequence</span><span style="font-family:"">,</span><span style="font-family:""> the record shows oscillations of the paleofied ranging from 120 μT and as low as ~10</span><span style="font-family:""> </span><span style="font-family:"">μT with very variable changes of the non-transitional/excursional paleofield.
