Abstract Low‐temperature hydrothermal manganese oxides occur throughout the global oceans. However, the hydrothermal replacement of a carbonate ooze by manganese oxides is described here for the first time. The 24 samples dredged from three locations around the Territory of American Samoa in the South Pacific Ocean include six samples with remnant carbonate and volcaniclastic sediments, which we refer to as “low Mn,” and 18 samples in which the mineralization is pervasive and has replaced most original sediment, termed “high Mn.” The 18 high‐Mn samples exhibit a mean Mn content of 51 wt.%. Higher Li and Mn contents and lower Fe contents in the high‐Mn samples indicate a hydrothermal origin and distinguish these samples from hydrogenetic ferromanganese crusts. Mn‐oxide layers are up to 90 mm thick, some with columns to 44 mm long and 10 mm wide, the magnitude of which has not been described previously. Samples are composed of birnessite and 10 Å phyllomanganate minerals. Textures of the thickest Mn layers indicate mineralization below the seabed from ascending fluids during multiple hydrothermal pulses. Mineralization took place by complete to partial replacement and cementation of foraminiferal sediments intermixed with volcaniclastic sediments in varying amounts. Our results highlight the production of carbonate sediment‐hosted hydrothermal Mn oxides from multiple hydrothermal sources within the Samoan volcanic chain. The potential extensive distribution on the regional scale of this newly described mineralization process and unique element enrichments raise questions about its broader distribution globally and potential importance to hydrothermal processes, element mass balance, and seabed mineral resources.

The fate of riverine sedimentary organic carbon and nitrogen, whether buried in the coast or exported to the deep sea, is of considerable interest because the relocated pool of carbon and nitrogen has a bearing on the phytoplankton evolution and climate change. To investigate sediment export fluxes to the East China Sea (ECS), six cruises were conducted between 2011 and 2013. 162 surface sediments were collected and analyzed for Be-7, Cs-137, and excess Pb-210 ((210)Pbex) to investigate the cross-shelf transport of sedimentary particles in a river-dominated margin, the ECS. Distribution of these radionuclides exhibited a clear seasonal variation corresponding to seasonal sediment transport. From the distributions of Be-7/(210)Pbex and Cs-137/(210)Pbex activity ratios, four pathways (I, II, III, and IV from north to south) can be identified, which existed in different seasons: section I for spring and summer, II for spring, III for all seasons, and IV for spring and summer. Using Pb-210 mass balance, the estimated cross-shelf transport particle fluxes (x10(6) ton yr(-1)) are: 1.5, 5.0, 28, and 0.32 for sections I, II, III, and IV, respectively, which in total account for 18% of the annual sediment discharge of Changjiang to the ECS in 2011. The cross-shelf (inner to outer) transport of particulate nitrogen and particulate organic carbon is estimated to be 2.8 x 10(11) g yr(-1) and 2.5x 10(12) g yr(-1), respectively, which is comparable to the Changjiang annual input POC. Quantification of the cross-shelf transport provides insights into particle dynamics in the coastal ocean, as well as insights into nutrients and pollutants as sinks in the marginal sea.

The mechanism(s) of sediment incorporation in lake and coastal sea ice and their subsequent transport is relevant to sediment dispersal to faraway distances including interior of the Artic Ocean, changes in the Albedo and radiation balance in the Arctic. The time scale and mechanism involved in the transfer of atmospherically delivered species from ocean/lake surface to sediment-laden sea ice is not well-known. A suite of ice-rafted sediment (IRS, 24 sampling sites) incorporated in ice samples from frozen Lake St. Clair in southeast Michigan was collected following major snowstorms (between Jan. 31 and March 2019) and the IRS and meltwater samples were analyzed for Be-7, Po-210 and Pb-210 using alpha and gamma spectrometry. The specific activities of Pb-210, Po-210 and Be-7 in IRS and meltwater varied up to three orders of magnitude, significantly elevated compared to Pb-210 data reported in the Arctic while atmospheric fallout in Detroit is similar to 6 times higher than that in the Arctic. From the measured activities during snowstorms, the fractions derived from bottom sediment and direct atmospheric fallout are quantified. The data obtained in this study indicates that the mechanisms responsible for enrichment of Pb-210 and Be-7 in ice-rafted sediments in Lake St. Clair is congruent with sea-ice in the Arctic. The enrichment factor for Pb-210 in IRS exceeds 100 and thus the atmospherically delivered particle-reactive species can be highly concentrated onto IRS and has relevance to other particle-reactive pollutants. These data suggest enrichment of these nuclides in ice-rafted sediments occur on a short time scale (< 1 day). We report the largest range of Pb-210 and Be-7 activities on ice-rafted sediment compared to any sedimentary system as well as in ice melt water.

U-Th series radionuclides are effective, naturally occurring tracers for studying groundwater transport mechanisms. Dissolution and sorption/desorption processes involving Fe-Mn oxyhydroxides play a major role in the mobility of select trace elements and radionuclides. For example, as radium is strongly bound to manganese oxides in most natural waters, the behavior of Mn in groundwater can be expected to affect Ra adsorption–desorption rates. In this study, the redox state of the aquifer in central Florida was examined to investigate the groundwater mobility of Ra and other trace elements. From a suite of 13 groundwater samples and complementary soil core samples, U/Th parent–daughter disequilibria were utilized to obtain sorption–desorption rate constants for radium. The large observed variability in 222Rn and 224Ra activities can be attributed to changes in fine-scale, phosphorite-bearing lithologies. The range of 223Ra/226Ra activity ratios is quite large (0.003–0.156) relative to the theoretical ratio of aged host rock, 0.046, indicating faster replenishment of 223Ra compared to 226Ra. The adsorption rate ranged from 0.03 to 2.4 min−1, corresponding to residence time of 0.4 to 33 min for Ra in groundwater. In contrast, the Ra desorption rate is slower, ranging from 0.5 to 21 × 10−4 min−1, which corresponds to a desorption time scale of 0.3–14 days. The retardation factor varied between (0.12 ± 0.03 and 7.0 ± 2.7) × 103. Within these samples, there was no significant correlation between the adsorption/desorption rate constants and the concentrations of redox-sensitive trace elements (i.e., Fe, Mn, or As), suggesting that redox processes alone do not control the adsorption–desorption constants. Furthermore, there is no apparent relationship between alkalinity and Ra adsorption-desorption rate constants, indicating that weathering processes alone do not control Ra sorption. The distribution coefficient varied between (0.16 and 9.3) × 103 L kg−1 (mean: 4.1 ± 4.0 × 103). This study provides insight into the adsorption–desorption kinetics of Ra within an aquifer controlled by fine-scale lithogenic and redox processes.

Exploration activities of hydrocarbon reservoirs have resulted in the release of naturally occurring radioactive material (NORM) into the environment, exposing them to workers and members of the public. Radium-226 and its progeny (222Rn, 210Pb and 210Po) in the 238U-series and 228Ra in the 232Th-series are key isotopes that are released into the environment. Excessive radiation derived from oil and natural gas activities can potentially result in adverse health effects and increased cancer risk; thus, this study is focused on the evaluation of radiation exposure in Southern Pennsylvania, where large-scale conventional drilling and newer technologies have been carried out for over a century. We collected and analyzed a suite of soil/sediment cores and grab samples; analyzed for 210Po, 210Pb, 226Ra and 228Ra; and evaluated the fraction of 226Ra derived from hydrocarbon exploration activities. The vertical variations of the activity ratios of 210Pb/226Ra and 210Po/210Pb for soil and sediment cores are plotted. The vertical variations enrichment factor for 226Ra are plotted showing the vertical variations on the extent of 226Ra enrichment. Using a modeling approach, an estimate of the production of 210Po and 210Pb from production well to houses are estimated. The measured activities of 238U- and 232Th series radionuclides (226Ra, 222Rn, 210Pb and 210Po, and 228Ra), indicate that the estimated radiation dose does not pose any radiation health hazard to the public in Southern Pennsylvania. However, the oil and gas workers may be at risk and should be considered for radiation monitoring when working with certain infrastructure.

Along the margins of the Great Lakes of North America, lake level fluctuations and flood events threaten coastal environments and infrastructure. However, little is known about coastal processes over centennial (or longer) timescales along these Great Lakes. In order to document overwash from Lake Erie that predates historical records, sediment cores MG19-3 and MG21-2 were extracted from Magee Marsh Wildlife Area on Lake Erie's southwestern shore. Both cores were subjected to loss-on-ignition and x-ray fluorescence analysis; for core MG21-2, microfossils were analyzed, and chronology was established by C-14 and Pb-210(xs) dating, while grain size was analyzed for core MG19-3. Cores consist of uniform clayey silt at the base overlain successively by a layer of sandy silt with sparse pebbles and shells, a thin layer of dark clay and silt, and a layer of coarse sand, pebbles, and shells. The uppermost sediments are organic-rich silt and peaty material. Sand layers contain low organic content, elevated carbonate content, and unique geochemical signatures relative to adjacent sediment depths. The sand layer signatures demonstrate that at least two intervals of overwash from Lake Erie occurred between 1430 CE (similar to 520 cal yr BP) and 1867 CE, attributed to separate processes of normal wave action and storm surge impact. These findings reveal that Magee Marsh serves as a repository to capture and preserve overwash deposits from Lake Erie. Future work investigating other Great Lakes coastal sites will enable regional correlation and insight into the periodicity and long-term impacts of these extreme events.

Disequilibria between the long-lived parents and short-lived particle-reactive daughters have been extensively used over the past six decades as tracers and chronometers in aquatic systems. In particular, the particle-reactive progeny of 226Ra (210Pb, half-life, T1/2, = 22.3 years and 210Po, T1/2 = 138.4 days) have been widely utilized to quantify oceanic biogeochemical processes (e.g. elemental export fluxes, residence time and scavenging rate of particulate and dissolved 210Po and 210Pb, settling velocity of particles and remineralization rates of biogenic particulate matter) as well as analogs for stable Pb, key micronutrients (e.g., Cu, Zn, Fe) and lithogenic elements (e.g., Al, Th, Ti). Vertical profiles of 210Po and 210Pb from the deep-ocean water column have been published for over six decades that show disequilibrium between 210Po and 210Pb with 210Po/210Pb activity ratio (AR) of >1.1 and/or < 0.9 in discrete deep-water layers, although secular equilibrium with AR of 1.0 ± 0.1 is expected. To understand this discrepancy, a critical and in-depth review of 210Po-210Pb-226Ra published data was conducted, scrutinizing the sample size, methodology, reagent blanks, statistical analysis, and data reduction. For each of the published data sets for water depths >1000 m, the total water column inventories and the average activities of dissolved, particulate and/or total 210Po, 210Pb, and 226Ra, were calculated. The total water-column-based average 210Po activities follow the pattern: Pacific Ocean > Indian Ocean > Antarctica > Atlantic Ocean > Arctic Ocean. The (210Po/210Pb) AR in small particles (1–51 μm) shows the following trend: N. Atlantic > E. Pacific > Arctic whereas the AR in large particles shows the following trend: E. Pacific > N. Atlantic > Artic. The fractionation factors calculated using inventories of 210Po and 210Pb, exhibit the following pattern: Pacific Ocean > Indian Ocean > Antarctica > Atlantic Ocean > Arctic Ocean. The inventory-based distribution coefficients (Kd) of 210Po and 210Pb are comparable, as opposed to consistently higher Kd for 210Po reported in the literature. From deep water and whole column inventories of 210Pb and 226Ra, disequilibrium was found ubiquitously, with a highly varying residence time of 210Pb. Average surface water concentrations of 210Pb in the global oceans were found to correlate with latitude and show an overall decrease in concentration from mid-latitudes to poles, similar to 210Pb fallout.

This paper presents the method of generation of ultra-flat broadband optical frequency comb using an Amplitude modulator (AM) and two Single Drive Mach-Zehnder modulators (SD-MZM) in cascade. Modulating signal of 30 GHz frequency is fed to the modulators with the carrier signal of 193.1THz. The modulated signal from the AM is directly fed to one SD-MZM. The AM output is also frequency shifted by 5GHz and fed to another SD-MZM. Both the SD-MZMs are designed with an extinction ratio of 30 dB and a symmetry factor of 0.955. This results in the production of 103 spectral lines with power ripple between each spectral tone to be less than 1 dB. While comparing with previous techniques, this simple cascaded configuration gives 103 ultra-flat spectral tones with a frequency repetition rate of 12 GHz. Each carrier generated from this method can act as a source for Wavelength Division Multiplexing - Passive Optical Networks (WDM-PON). This resolves the need for the broadband capability for the next generation network.

California faces increasing economic and societal risks from extreme precipitation and flooding associated with atmospheric rivers (ARs) under projected twenty-first century climate warming. Lake sediments can retain signals of past extreme precipitation events, allowing reconstructions beyond the period of instrumental records. Here, we calibrate AR-related extreme precipitation from the last century to proxy data from lake sediments collected in the latitudinal zone of the highest frequency landfall for modern ARs in California. Excursions in erosional proxy data (Ti/Al) are positively and significantly correlated (rmedian = 0.45, pmedian = 0.04) with modern records of integrated vapor transport (IVT, kg m−1 s−1), a key metric of AR intensity, using correlations that incorporate age-model uncertainty. Despite the land-use change near the study site, the data suggest intense and long-lasting AR storms are identifiable in this sedimentary record. These results allow conservative inferences concerning past extreme hydrology at this site.

A suite of road sediment and soil samples from a post-industrial city (Detroit, MI) were collected and analyzed for atmospherically-delivered 210Pb, 210Po, 7Be along with 226Ra and 137Cs in the bulk and size-fractionated solid samples. From the measured atmospheric depositional fluxes of 7Be, 210Po, and 210Pb, the initial 210Po/210Pb activity ratio was quantified. In all samples, there is disequilibrium between 210Po and 210Pb, with a 210Po/210Pb activity ratio (AR) of <1.0, which is reported for the first time. Using the measured 210Po/210Pb AR, the average ‘apparent age’ of road sediment was found to be 146 ± 62 days. Using numerical modeling, it is predicted that the (210Po/210Pb) excess activity ratio will reach a ‘dynamic equilibrium’ value of ~0.59 over a period of >1 year. Results from a subset of samples that were sequentially extracted for exchangeable, carbonate, Fe-Mn oxide, organic and residual phases indicate the Fe-Mn oxide fraction was found to contain the largest fraction of 7Be and 210Pb; however, the largest fraction of 210Pb was associated with the residual phase and is attributed to complexation of 210Pb with recalcitrant organic matter. This study shows that the natural tagging of 7Be and 210Po-210Pb pair via precipitation provides insights on the time scale of their mobility and adds a new dimension of time information on the pollutant-laden road sediment.

Burgeoning data rates are demanding a shift towards millimeter wave frequencies to combat the pressure on the congested spectrum that is in existence today. This paper elucidates how to generate a 160 GHz millimeter wave signal with a series parallel combination of polarization modulators (PoIMs) using a frequency 16 tupling technique based on polarization property. A 160 GHz optical signal is produced by adjusting the phases between the PoIM stages and selecting the right modulation index. Only marginal deviations in the optimally determined phase shift values cause minimal changes in sideband suppression ratios, according to research. At each level of the simulation, the outcomes are mathematically verified. The optical sideband suppression ratio (OSSR) and the radio frequency spurious suppression ratio (RFSSR) have been determined to be 65 and 51.4 dBm, respectively.

Inhalation and/or ingestion of toxic heavy metals enriched in road dust have toxic effects on humans. From inhalation and ingestion of dust, release of readily bioavailable elements sorbed on to dust, could lead to health issues such as lung or skin cancer, kidney dysfunction, hypertension, dermal lesions, peripheral neuropathy, and vascular disease. On 49 road dust and soil samples collected in the Metro Detroit area, we analyzed a suite of trace metals in <63 μm and size-separated fractions to quantify the extent of metal enrichment and contamination status. We evaluated Enrichment Factor (EF), Pollution Index (PI), Geoaccumulation Index (GI), and Pollution Load Index (PLI). The average Chromium (Cr) concentration of 198 ppm is the highest reported for any global city in literature while in ∼80% samples, Barium (Ba), Cr, Lead (Pb), and Zinc (Zn) concentrations exceeded the USEPA limit. The EF for Barium (Ba) was found to be ≥9 in all samples, and for the rest of other elements was >1.5. The PI values for Cr, Ba, Zinc (Zn), Lead (Pb), and Selenium (Se) indicate elevated levels and for Ba, Cr, and Zn up to a moderate level. PLI values in >50% of road dusts were ≥3, indicating many sites are ‘heavily polluted’. The PLI value in Detroit road dust is higher than those reported for some other global cities including Shanghai. Observed strong correlations between Cr-Zn and Cadmium (Cd)-Silver (Ag) likely indicate a common metal source. Cluster analysis of data for Cd, Arsenic (As), Pb, and Zn appears to be distinct between different proximally related clusters, while Nickel (Ni) and Ba are potentially more distinct between property type clusters. In general, metal concentrations of industrial samples are more commonly distinct with over half of metals (≥6 of 11) differing from residential and/or soil samples. Three generalized “groups” were identified from the combination of hierarchical cluster and PCA analyses followed by varimax rotation: Group 1 characterized by Cr, Cd, Ni, Ag, Zn, and Copper (Cu); Group 2 characterized by Pb, As, Mercury (Hg), and minor Ba; and Group 3 characterized by Se. This is the first study to report all four metrics of metal pollution along with rigorous statistical analysis.

Abstract: Dye sensitized solar cell (DSSC) are new type of solar cell, has aroused worldwide attention which arises from its merits of low cost, ease of fabrication and environmental friendliness, etc. The development history, basic structure and working principle of the DSSC are introduced briefly, and the classification and development of DSSC are stated in detail. Dye sensitizers are divided into two major categories organic dyes and metal-organic compounds, and organic dyes can roughly be classified into several parts. A new form of solar cell is being investigated using a dye-sensitized solar cell (DSSC) using an inorganic semiconductor, due to the anticipated less costing solution to standard solid-state equipment. The formulation of effective solar cell contains countless semiconducting materials. This was an initiative of the researchers to study the fabricated of the natural dye sensitized solar cells for sol-gel dipping coated zinc oxide nanorod and also more voluminous in surface. Moreover, the corresponding assumptions and measures on how to improve the energy efficiency of the DSSCs are proposed, and finally the trends and promising prospects are presented. Keywords: ZnO Nanorods, Dye Sensitized Solar Cells (DSSC), Organic Solar Cell, Dip Coating Method

Climate change is transforming the Arctic Ocean in unprecedented ways which can be most directly observed in the systematic decline in seasonal ice coverage. From the collection and analysis of particulate and dissolved activities of Po-210 and Pb-210 from four deepwater superstations, as a part of the US Arctic GEOTRACES cruise during 2015, and in conjunction with previously published data, the temporal and spatial variations in their activities, inventories and residence times are evaluated. The results show that the partitioning of particulate and dissolved phases has changed significantly in the 8 years between 2007 and 2015, while the total Po-210 and Pb-210 activities have remained relatively unchanged. Observed total Po-210/Pb-210 activity ratio was less than unity in all deepwater stations, implying disequilibria in the entire water column. From the distribution of total Po-210 and Pb-210 in the upper 500 m of all major Arctic Basins, the derived scavenging efficiencies decrease as per the following sequence: Makarov Basin > Gakkel Bridge > Canada Basin Nansen Basin similar to Amundsen Basin > Alpha Ridge, which is the reverse order of the calculated residence times of Po-210(T). The scavenging intensities differ between the fully ice-covered, partially ice-covered, and no ice-covered stations, as observed from the differences in the average activities of Po-210 and Pb-210. The average settling velocity of particulate matter based on the Pb-210 activity is similar to the published values based on Th-230, indicating removal mechanism(s) of Th and Pb is (are) similar.

High resolution gamma spectrometry is one of the most widely used techniques in the measurements of envi-ronmental level Pb-210 in sediment from coastal and freshwater environments and such measurements are needed to establish Pb-210 chronology for the past 100-150 years. Precise measurement of( 210)Pb in sediment and soil requires appropriate self-absorption correction for its low-energy (46.5 keV) gamma radiation due to differences in the matrix between the sample and standard used to calibrate the instrument. Here we report a method that involves precise determination of( 210)Pb activity in sediment sample by calibrating the HPGe well detector with RGU-1-IAEA Certified Reference Material for well-defined geometries. A comparison of the Pb-210 activity ob-tained from gamma-ray spectrometry with that obtained from alpha spectrometry via Po-210, using( 209)Po as yield tracer, indicates good agreement. We propose an empirical relation between the absolute efficiencies and packing densities of sample in a well-defined geometry (cylindrical counting vial) by affecting the count rate of Pb-210 and its progenitor, Ra-226 (via Pb-214 and Bi-214). The effects of self-attenuation of 46.5 keV (Pb-210), for naturally-occurring high-density minerals (apatite, titanite, monazite, and cerite) are evaluated. Specific activity of Pb-210 on apatite measured by alpha and gamma spectrometry are compared. This study is relevant and useful for precise measurements of gamma-emitting environmental radionuclides such as Pb-210, Be-7, Cs-137 as well as Ra-226.

Hearing loss affects around 360 million people worldwide. According to the WHO, there are 328 million people and 32 million children who are deaf. Deaf and dumb individuals account for over 9.1 billion persons on the planet. Only 700 schools in India teach sign language, and many people are unaware that sign language exists. Despite the fact that technology has made human existence easier, there are still those people who are finding it difficult. We offer a new electronic device in this idea that will make communication easier for them. The wearable electronic device aids persons with speech, hearing, and visual impairments. This wearable electronic aid will be used by people with the aforementioned difficulties who do not know sign language to communicate with others.

Cesium-137, a unique geochemical tracer, behaves as a particle-reactive species in freshwater that is useful as a geochronometer, and soluble in seawater that is used as a water mass tracer, as evidenced by higher solid -solution partition coefficient, Kd, in freshwater and much lower Kd values in seawater. A suite of sediment cores were collected from the Southern Yellow Sea and coastal regions of Croatia in 2014 and analyzed for vertical profiles of excess 210Pb (210Pbex), 239+240Pu, and 137Cs. A set of laboratory experiments were also con-ducted to investigate the partitioning of 137Cs between a suite of solid material comprised of commonly occurring minerals in the environment and solution under different contact times, pH, and salinity. The partition coefficient showed that for illite Kd sharply increased during the first two hours and then slowly increased after 4 h. Overall, the salinity significantly affects the 137Cs behavior in aqueous environments. The Kd values of 137Cs were higher (6.5 x 103-1.1 x 104 mL g-1) when the salinity was below 0.5 psu but drastically decreased to 9.0 x 102 mL g-1 when salinity was 3.6 psu and then slowly decreased to 2.7 x 102 mL g-1 with the salinity of 27.5 psu. Combining with the previously published results, it is observed that higher suspended particle (SPM) concen-tration could enhance the Kd values of 137Cs when SPM was below 12 mg L-1. Our results show that post -depositional mobility of 137Cs in the marine environment, except for river-dominated coastal areas, result in the 137Cs chronology is not suitable to validate the 210Pbex-based chronology. The penetration depths of 137Cs were found to be much deeper than it was expected based on the 137Cs and 239+240Pu peak and 210Pb chronology. Chitin showed a higher affinity for 137Cs than clay particles (e.g., smectite and illite). The desorption experiment showed that the NH4+ could leach 5.6% of sorbed 137Cs, accounting for 79% of the total exchangeable fraction while 2.8% of the total 137Cs was bound to organic matter. These observations support the field observation degradation of organic matter in anoxic marine sediment could enhance the mobility of 137Cs.