scholarly journals Dissolved Inorganic Geogenic Phosphorus Load to a Groundwater-Fed Lake: Implications of Terrestrial Phosphorus Cycling by Groundwater

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2213 ◽  
Author(s):  
Catharina Simone Nisbeth ◽  
Jacob Kidmose ◽  
Kaarina Weckström ◽  
Kasper Reitzel ◽  
Bent Vad Odgaard ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Anthropogenic Sources ◽  
Small Island ◽  
Confined Aquifer ◽  
Phosphorus Load ◽  
Potential Significance ◽  
Sand Aquifer ◽  
Current Water ◽  
Water Ecosystems ◽  
P Cycle

The general perception has long been that lake eutrophication is driven by anthropogenic sources of phosphorus (P) and that P is immobile in the subsurface and in aquifers. Combined investigation of the current water and P budgets of a 70 ha lake (Nørresø, Fyn, Denmark) in a clayey till-dominated landscape and of the lake’s Holocene trophic history demonstrates a potential significance of geogenic (natural) groundwater-borne P. Nørresø receives water from nine streams, a groundwater-fed spring located on a small island, and precipitation. The lake loses water by evaporation and via a single outlet. Monthly measurements of stream, spring, and outlet discharge, and of tracers in the form of temperature, δ18O and δ2H of water, and water chemistry were conducted. The tracers indicated that the lake receives groundwater from an underlying regional confined glaciofluvial sand aquifer via the spring and one of the streams. In addition, the lake receives a direct groundwater input (estimated as the water balance residual) via the lake bed, as supported by the artesian conditions of underlying strata observed in piezometers installed along the lake shore and in wells tapping the regional confined aquifer. The groundwater in the regional confined aquifer was anoxic, ferrous, and contained 4–5 µmol/L dissolved inorganic orthophosphate (DIP). Altogether, the data indicated that groundwater contributes from 64% of the water-borne external DIP loading to the lake, and up to 90% if the DIP concentration of the spring, as representative for the average DIP of the regional confined aquifer, is assigned to the estimated groundwater input. In support, paleolimnological data retrieved from sediment cores indicated that Nørresø was never P-poor, even before the introduction of agriculture at 6000 years before present. Accordingly, groundwater-borne geogenic phosphorus can have an important influence on the trophic state of recipient surface water ecosystems, and groundwater-borne P can be a potentially important component of the terrestrial P cycle.

Substantial accumulation of mercury in the deepest parts of the ocean and implications for the environmental mercury cycle

2021 ◽  
Vol 118 (51) ◽  
pp. e2102629118
Author(s):  
Maodian Liu ◽  
Wenjie Xiao ◽  
Qianru Zhang ◽  
Shengliu Yuan ◽  
Peter A. Raymond ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Food Webs ◽  
Deep Sea ◽  
Anthropogenic Activities ◽  
Sediment Cores ◽  
Anthropogenic Sources ◽  
Biogeochemical Cycle ◽  
Vertical Profiles ◽  
Surface Ocean ◽  
Increasing Trends

Anthropogenic activities have led to widespread contamination with mercury (Hg), a potent neurotoxin that bioaccumulates through food webs. Recent models estimated that, presently, 200 to 600 t of Hg is sequestered annually in deep-sea sediments, approximately doubling since industrialization. However, most studies did not extend to the hadal zone (6,000- to 11,000-m depth), the deepest ocean realm. Here, we report on measurements of Hg and related parameters in sediment cores from four trench regions (1,560 to 10,840 m), showing that the world’s deepest ocean realm is accumulating Hg at remarkably high rates (depth-integrated minimum–maximum: 24 to 220 μg ⋅ m−2 ⋅ y−1) greater than the global deep-sea average by a factor of up to 400, with most Hg in these trenches being derived from the surface ocean. Furthermore, vertical profiles of Hg concentrations in trench cores show notable increasing trends from pre-1900 [average 51 ± 14 (1σ) ng ⋅ g−1] to post-1950 (81 ± 32 ng ⋅ g−1). This increase cannot be explained by changes in the delivery rate of organic carbon alone but also need increasing Hg delivery from anthropogenic sources. This evidence, along with recent findings on the high abundance of methylmercury in hadal biota [R. Sun et al., Nat. Commun. 11, 3389 (2020); J. D. Blum et al., Proc. Natl. Acad. Sci. U. S. A. 117, 29292–29298 (2020)], leads us to propose that hadal trenches are a large marine sink for Hg and may play an important role in the regulation of the global biogeochemical cycle of Hg.

Weathering signals in Lake Baikal and its tributaries

2020 ◽  
Author(s):  
Tim Jesper Suhrhoff ◽  
Jörg Rickli ◽  
Marcus Christl ◽  
Elena G. Vologina ◽  
Eugene V. Sklyarov ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Lake Baikal ◽  
Sediment Cores ◽  
Isotope Ratios ◽  
Anthropogenic Sources ◽  
Glacial Cycles ◽  
Chem Geol ◽  
Temperature And Precipitation ◽  
Spatial Differences ◽  
Induced Changes

<p>Lake Baikal is the world’s largest (by volume), deepest, and oldest (30-40 Ma) lake. In the catchment, climate varies from arid to semi-arid to arctic-boreal with extreme seasonal and spatial differences in temperature and precipitation<sup>1</sup>. Elevation ranges from 450-3000m, resulting in a large range of geomorphic settings. The catchment has also been affected by periodic Quaternary glaciations<sup>2</sup>. Although the geology of the catchment is diverse and contains igneous, metamorphic and sedimentary rocks of Archean to Cenozoic ages, the most prominent lithologies are granitoids and gneisses with only minor carbonate contributions<sup>1</sup>. Continuous lake sediment cores are available recording the Quaternary glacial cycles, and even dating back into the Miocene. Lake Baikal is therefore a promising site to study variation of silicate rock weathering in both space and time.</p><p>In preparation for paleo-studies, we constrain the present-day budget of the lake with respect to radiogenic weathering tracers (Nd, Pb, and Sr) and meteoric <sup>10</sup>Be/<sup>9</sup>Be isotope ratios.  Nd, Sr, Pb, and their radiogenic isotope systems show different behaviors in Lake Baikal. Sr concentrations in the lake are similar to riverine inputs, reflecting conservative behavior of Sr and resulting in a uniform isotopic composition that is slightly higher than the average of riverine inputs (possibly due to loess inputs<sup>3</sup>). Pb concentrations are higher in the lake than in the major tributaries. The isotopic composition of both lake and rivers point to anthropogenic sources of Pb. In contrast, Nd concentrations in the lake are much lower than in the rivers. Nd isotopic compositions are similar in the central and southern basin but less radiogenic in the northern basin. Both <sup>10</sup>Be and <sup>9</sup>Be concentrations are much lower in Lake Baikal than in its tributaries, possibly indicating removal due to pH induced changes in dissolved-particulate partitioning<sup>4</sup>. This may also explain the contrast in Nd concentrations between rivers and the lake. <sup>10</sup>Be/<sup>9</sup>Be ratios in the lake are slightly elevated compared to riverine  inputs, suggesting a potential role for dust and/or precipitation as a source for <sup>10</sup>Be<sup>5</sup>. We will also compare silicate weathering fluxes derived from meteoric Be isotope ratios with those derived from major element concentrations and riverine discharges.</p><p>Taken together, these results highlight the importance of assessing modern processes at sediment core locations prior to interpreting variation in the past, and the benefits of using a suite of weathering proxies rather than relying on one: while Sr isotopes at any core location record changes to the chemistry of the whole lake (and the processes in its catchment), Be and Nd isotopes are likely biased to the inputs of the nearest rivers.</p><ol><li>Zakharova et al. Chem. Geol. <strong>214</strong>, 223–248 (2005).</li> <li>Karabanov et al. Quat. Res. <strong>50</strong>, 46–55 (1998).</li> <li>Yokoo et al. Chem. Geol. <strong>204</strong>, 45–62 (2004).</li> <li>You et al. Chem. Geol. <strong>77</strong>, 105–118 (1989).</li> <li>Aldahan et al. Geophys. Res. Lett. <strong>26</strong>, 2885–2888 (1999).</li> </ol>

scholarly journals Discrimination of Heavy Metal Sources in the Sefidrud Delta Coastal Lagoons, Caspian Sea, N Iran: A Statistical Approach

2021 ◽  
Author(s):  
Behrouz Rafiei ◽  
Fatemeh Ahmadi-Ghomi ◽  
Asghar Seif ◽  
Ali Shakibaazad ◽  
Sonia Shamshiri ◽  
...  
Keyword(s):  
Caspian Sea ◽  
Coastal Lagoons ◽  
Sediment Cores ◽  
Contamination Factor ◽  
Pollution Load Index ◽  
Anthropogenic Sources ◽  
The Caspian Sea ◽  
Test Technique ◽  
Significant Difference ◽  
Accumulation Index

Abstract Amirkola (more than 500 years in age), Kiashahr and Zibakenar (a few decades in age) lagoons are located on the Sefidrud Delta, the southern coast of the Caspian Sea. Evaluating the pollution degree caused by heavy metals (including Cu, Cr, Co, Ni, Pb, Zn and V), 106 sediment samples and three sediment cores were taken from studied lagoons. Three indices, including geo-accumulation index (Igeo), contamination factor (CF), and pollution load index (PLI), were employed to determine the contamination degree in the lagoons. Based on contamination indices, the Kiashahr and Zibakenar lagoons show significant to moderate contamination with Co, Cu, Pb, Zn and V. Nonparametric statistical analysis (Two-step cluster analysis, analysis of variance, and T-test technique) was used to discriminate the pollution sources. Statistical methods indicated the unique interpretation of contaminants sources. There is a significant difference in metal concentrations between Amirkola and two younger lagoons. Despite the same geogenic origin of sediments in the Sefidrud Delta and lagoons deposits, Co, Zn, and Pb show anthropogenic sources in the newly-formed Kiashahr and Zibakenar lagoons.

Visual Evoked-Response Correlates of Speechreading Performance in Normal-Hearing Adults

1983 ◽  
Vol 26 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Vincent J. Samar ◽  
Donald G. Sims
Keyword(s):  
Multiple Correlation Coefficient ◽  
Evoked Response ◽  
Multiple Correlation ◽  
Potential Significance ◽  
Visual Evoked Response ◽  
Latency Measure ◽  
Two Measures ◽  
Components Analysis ◽  
The Relationship ◽  
Visual Evoked

The relationship between the latency of the negative peak occurring at approximately 130 msec in the visual evoked-response (VER) and speechreading scores was investigated. A significant product-moment correlation of -.58 was obtained between the two measures, which confirmed the fundamental effect but was significantly weaker than that previously reported in the literature (-.90). Principal components analysis of the visual evoked-response waveforms revealed a previously undiscovered early VER component, statistically independent of the latency measure, which in combination with two other components predicted speechreading with a multiple correlation coefficient of S4. The potential significance of this new component for the study of individual differences in speechreading ability is discussed.

Pemetaan Pulau Kecil Gelasa Kabupaten Bangka Tengah

2019 ◽  
Vol 2 (1) ◽  
pp. 11-14
Author(s):  
Wahyu Adi
Keyword(s):  
Coral Reefs ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Image Interpretation ◽  
Vegetation Coverage ◽  
Small Island ◽  
Shallow Waters ◽  
Small Islands ◽  
Seagrass Beds ◽  
Cover Density

Pulau Kecil Gelasa merupakan daerah yang belum banyak diteliti. Pemetaan ekosistem di pulau kecil dilakukan dengan bantuan citra Advanced Land Observing Satellite (ALOS). Penelitian terdahulu diketahui bahwa ALOS memiliki kemampuan memetakan terumbu karang dan padang lamun di perairan dangkal serta mampu memetakan kerapatan penutupan vegetasi. Metode interpretasi citra menggunakan alogaritma indeks vegetasi pada citra ALOS yaitu NDVI (Normalized Difference Vegetation Index), serta pendekatan Lyzengga untuk mengkoreksi kolom perairan. Hasil penelitian didapatkan luasan Padang Lamun di perairan dangkal 41,99 Ha, luasan Terumbu Karang 125,57 Ha. Hasil NDVI di daratan/ pulau kecil Gelasa untuk Vegetasi Rapat seluas 47,62 Ha; luasan penutupan Vegetasi Sedang 105,86 Ha; dan penutupan Vegetasi Jarang adalah 34,24 Ha.   Small Island Gelasa rarely studied. Mapping ecosystems on small islands with the image of Advanced Land Observing Satellite (ALOS). Previous research has found that ALOS has the ability to map coral reefs and seagrass beds in shallow water, and is able to map vegetation cover density. The method of image interpretation uses the vegetation index algorithm in the ALOS image, NDVI (Normalized Difference Vegetation Index), and the Lyzengga approach to correct the water column. The results of the study were obtained in the area of Seagrass Padang in the shallow waters of 41.99 ha, the area of coral reefs was 125.57 ha. NDVI results on land / small islands Gelasa for dense vegetation of 47.62 ha; area of Medium Vegetation coverage 105.86 Ha; and the coverage of Rare Vegetation is 34.24 Ha.

Future climate change and its impacts over small island states

2002 ◽  
Vol 19 ◽  
pp. 179-192 ◽  
Author(s):  
M Lal ◽  
H Harasawa ◽  
K Takahashi
Keyword(s):  
Climate Change ◽  
Future Climate ◽  
Future Climate Change ◽  
Small Island ◽  
Island States ◽  
Small Island States

Habitat fragmentation causes collapse of kelp recruitment

2020 ◽  
Vol 648 ◽  
pp. 111-123
Author(s):  
C Layton ◽  
MJ Cameron ◽  
M Tatsumi ◽  
V Shelamoff ◽  
JT Wright ◽  
...  
Keyword(s):  
Habitat Fragmentation ◽  
Patch Size ◽  
Life Stage ◽  
Extended Period ◽  
Anthropogenic Disturbances ◽  
Anthropogenic Sources ◽  
Kelp Forests ◽  
Natural Disturbances ◽  
Short Term ◽  
Turf Algae

Kelp forests in many regions are experiencing disturbance from anthropogenic sources such as ocean warming, pollution, and overgrazing. Unlike natural disturbances such as storms, anthropogenic disturbances often manifest as press perturbations that cause persistent alterations to the environment. One consequence is that some kelp forests are becoming increasingly sparse and fragmented. We manipulated patch size of the kelp Ecklonia radiata over 24 mo to simulate persistent habitat fragmentation and assessed how this influenced the demography of macro- and microscopic juvenile kelp within the patches. At the beginning of the experiment, patch formation resulted in short-term increases in E. radiata recruitment in patches <1 m2. However, recruitment collapsed in those same patches over the extended period, with no recruits observed after 15 mo. Experimental transplants of microscopic and macroscopic juvenile sporophytes into the patches failed to identify the life stage impacted by the reductions in patch size, indicating that the effects may be subtle and require extended periods to manifest, and/or that another life stage is responsible. Abiotic measurements within the patches indicated that kelp were less able to engineer the sub-canopy environment in smaller patches. In particular, reduced shading of the sub-canopy in smaller patches was associated with proliferation of sediments and turf algae, which potentially contributed to the collapse of recruitment. We demonstrate the consequences of short- and longer-term degradation of E. radiata habitats and conclude that habitat fragmentation can lead to severe disruptions to kelp demography.

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