scholarly journals Recent environmental changes in the Yunnan–Guizhou Plateau inferred from organic geochemical records from the sediments of Fuxian Lake

Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Haibo He ◽  
Zaihua Liu ◽  
Dongli Li ◽  
Hongbo Zheng ◽  
Jianxin Zhao ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Anthropogenic Impacts ◽  
Anthropogenic Activities ◽  
Sediment Cores ◽  
High Amplitude ◽  
Average Chain Length ◽  
Past Century ◽  
The Past ◽  
The 1950S ◽  
Guizhou Plateau

During the past century, many lacustrine environments have changed substantially at the ecosystem level as a result of anthropogenic activities. In this study, the distributions of n-alkane homologues, carbon isotopes (δ13Corg), organic carbon, and the C/N atomic ratio in two sediment cores from Fuxian Lake (Yunnan, southwest China) are used to elucidate the anthropogenic impacts on this deep, oligotrophic, freshwater lake. The carbon preference index (CPI) of long-chain components, average chain length (ACL), proportion of aquatic macrophytes (Paq), and terrigenous/aquatic ratios (TAR) show different temporal patterns that reflect variations in biological production. Notably, the n-alkane homologues are shown to be more sensitive to environmental changes than δ13Corg and the C/N ratio. Prior to the 1950s, minor variations in the sedimentary geochemical record were likely caused by climate changes, and they represent a natural stage of lake evolution. The onset of cultural eutrophication in Fuxian Lake occurred in the 1950s, when the n-alkane proxies collectively exhibited high-amplitude fluctuations but overall decreasing trends that coincided with population growth and related increases in land-use pressure. In the 21st century, Fuxian Lake has become even more eutrophic in response to human activities, as indicated by sharp increases in C/N ratio, Paq, δ13Corg, ACL, CPI, and TAR. Our findings provide robust molecular sedimentary evidence confirming that the environmental evolution of lakes in the Yunnan–Guizhou Plateau over the past century was closely associated with enhanced anthropogenic activities.

Environmental changes in Lake Taihu during the past century as recorded in sediment cores

Hydrobiologia ◽  
2007 ◽  
Vol 581 (1) ◽  
pp. 117-123 ◽  
Author(s):  
Bin Xue ◽  
Shuchun Yao ◽  
Weilan Xia
Keyword(s):  
Environmental Changes ◽  
Lake Taihu ◽  
Sediment Cores ◽  
Past Century ◽  
The Past

PALEOLIMNOLOGY OF THE MAYA LOWLANDS

2002 ◽  
Vol 13 (1) ◽  
pp. 141-157 ◽  
Author(s):  
Mark Brenner ◽  
Michael F. Rosenmeier ◽  
David A. Hodell ◽  
Jason H. Curtis
Keyword(s):  
Late Holocene ◽  
Environmental Changes ◽  
Anthropogenic Activities ◽  
Yucatan Peninsula ◽  
Sediment Cores ◽  
Maya Lowlands ◽  
Holocene Climate ◽  
The Past ◽  
Yucatán Peninsula ◽  
Paleoclimate Records

Since the late 1950s, scientists have used sediment cores from lakes on the Yucatan Peninsula to explore the complex interactions among climate, environment, and ancient Maya culture. Early paleolimnological studies generally assumed that late Holocene climate was invariable. Consequently, paleolimnologically inferred environmental changes that occurred during the past 3,000 years or so—for example, forest decline and soil erosion—were attributed wholly to anthropogenic activities such as land clearance for agriculture and construction. Recent high-resolution, proxy-based paleoclimate records from continental and insular sites around the Caribbean Sea contradict the assumption of late Holocene climate stability. Instead, these core data suggest that regional drying began about 3,000 years ago and that the past three millennia were characterized by variable moisture availability. Paleoclimate inferences from Lakes Chichancanab and Punta Laguna, northern Yucatan Peninsula, indicate that drought events over the past 2,600 years were cyclical. These dry events, thought to have been driven by solar forcing, appear to have occurred approximately every two centuries (about 208 years). The driest period of the late Holocene occurred between A.D. 800 and 1000, coincident with the Classic Maya Collapse. We review the history of paleolimnological studies in the Maya Lowlands, discuss the difficulty of differentiating climatic signals from anthropogenic signals in late Holocene lake sediment profiles, and assess current understanding of past climate changes in the region based on regional lacustrine sediment studies.

scholarly journals The site Vavilino 1 on the right bank of the Derkul River in Western Kazakhstan (materials of 2018)

2019 ◽  
Vol 8 (3) ◽  
pp. 166-173
Author(s):  
Talgat Basarbaevich Mamirov
Keyword(s):  
Anthropogenic Activities ◽  
Past Century ◽  
Stone Age ◽  
Cultural Layer ◽  
Stone Artifacts ◽  
The Past ◽  
Western Kazakhstan ◽  
The Right ◽  
Bone Remains ◽  
Excavation Area

The paper is devoted to preliminary data from a study of the Vavilino 1 site in Western Kazakhstan. The monument was first opened by N.M. Malov in 1986, later he picked artifacts from the surface in 1988. In 1991 N.L. Morgunova carried out excavations on the site, which showed the importance of this monument study to understand the Neolithic Volga-Ural interfluve. The monument is located on the right bank of the Derkul River and is currently classified as an emergency. In 2018, employees of the Institute of Archeology named after A.Kh. Margulan in the framework of the Stone Age study in Western Kazakhstan started to work on the monuments of Yeshkitau, Derkul 1 and Vavilino 1. At the Vavilino 1 site a small excavation area - 16 square meters was made, more than a thousand stone artifacts were received; fragments of ceramics and bone remains of animals were poorly diagnosed. Excavations have shown the presence of a 15-20 cm thick cultural layer belonging to the Neolithic time. The upper layer of the monument with a capacity of up to 30 cm was destroyed by anthropogenic activities in the past century. The material from the cultural layer is not numerous; tip scrapers, fragments of plates with retouching, geometrical microliths, prismatic nucleus for plates, etc. are typologically distinguished.

scholarly journals Transboundary Basins Need More Attention: Anthropogenic Impacts on Land Cover Changes in Aras River Basin, Monitoring and Prediction

2020 ◽  
Vol 12 (20) ◽  
pp. 3329
Author(s):  
Sajad Khoshnoodmotlagh ◽  
Jochem Verrelst ◽  
Alireza Daneshi ◽  
Mohsen Mirzaei ◽  
Hossein Azadi ◽  
...  
Keyword(s):  
Land Cover ◽  
River Basin ◽  
Urban Areas ◽  
Anthropogenic Impacts ◽  
Anthropogenic Activities ◽  
Kappa Index ◽  
The Caspian Sea ◽  
The Past ◽  
Agricultural Areas ◽  
Aras River

Changes in land cover (LC) can alter the basin hydrology by affecting the evaporation, infiltration, and surface and subsurface flow processes, and ultimately affect river water quantity and quality. This study aimed to monitor and predict the LC composition of a major, transboundary basin contributing to the Caspian Sea, the Aras River Basin (ARB). To this end, four LC maps of ARB corresponding to the years 1984, 2000, 2010, and 2017 were generated using Landsat satellite imagery from Armenia and the Nakhchivan Autonomous Republic. The LC gains and losses, net changes, exchanges, and the spatial trend of changes over 33 years (1984–2017) were investigated. The most important drivers of these changes and the most accurate LC transformation scenarios were identified, and a land change modeler (LCM) was applied to predict the LC change for the years 2027 and 2037. Validation results showed that LCM, with a Kappa index higher than 81%, is appropriate for predicting LC changes in the study area. The LC changes observed in the past indicate significant anthropogenic impacts on the basin, mainly by constructing new reservoir dams and expanding agriculture and urban areas, which are the major water-consuming sectors. Results show that over the past 33 years, agricultural areas have grown by more than 57% from 1984 to 2017 in the study area. Results also indicate that the given similar anthropogenic activities will keep on continuing in the ARB, and agricultural areas will increase by 2% from 2017 to 2027, and by another 1% from 2027 to 2037. Results of this study can support transboundary decision-making processes to analyze potential adverse impacts following past policies with neighboring countries that share the same water resources.

When to Send Your Telescope Aloft

2019 ◽  
Vol 50 (3) ◽  
pp. 265-305
Author(s):  
David H. DeVorkin
Keyword(s):  
Research Agenda ◽  
New Technology ◽  
Past Century ◽  
Specific Question ◽  
Large Space ◽  
The Past ◽  
Making Choices ◽  
The 1950S ◽  
Department Chairman

How have astronomers and physicists responded to the challenge of getting “beyond the atmosphere” in the past century or so, and how did they go about making choices in how they did so? This case study examines a particularly poignant example of how an astronomer’s practice changed in the 1950s when that astronomer, Princeton theoretical astrophysicist Martin Schwarzschild, made a commitment to utilize newly improved balloon technology to answer a specific question arising from his own research agenda. Here we follow Schwarzschild’s efforts, which led initially to success, and then examine how, bolstered by his department Chairman, Lyman Spitzer, he built upon that success to generalize the new technology to try to provide a capability that might address a wider range of questions, and, aiding Spitzer’s plan, provide a stepping stone to an eventual Large Space Telescope. How he fared in making this decision reveals the challenges facing academic astronomers in the 1950s who attempted to send their telescopes aloft. It also reveals the complexities of taking on such projects, complexities that were unknown to the average mainstream astronomer.

scholarly journals Sedimentation rates in the Lake Qattinah using 210Pb and 137Cs as geochronometer

2014 ◽  
Vol 41 (1) ◽  
pp. 81-86 ◽  
Author(s):  
Eskander Alhajji ◽  
Iyas Ismail ◽  
Mohammad Al-Masri ◽  
Nouman Salman ◽  
Mohammad Al-Haleem ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Past Century ◽  
Sedimentation Rates ◽  
Accumulation Rates ◽  
210Pb And 137Cs ◽  
The Past ◽  
Activity Concentrations ◽  
210Pb Activity ◽  
Constant Rate ◽  
210Pb Method

Abstract The constant rate of supply (CRS) of excess 210Pb model was successfully applied to assess 210Pb data of two sediment cores from the lake Qattinah, Syria. Gamma spectrometry was used to determine 137Cs and 210Pb activity concentrations. The bottom of the cores was 210Pb-dated to years 1907 and 1893. The accumulation rates were determined using 210Pb method and found to vary similarly in both cores from 0.10 ± 0.01 to 3.78 ± 0.57 kg m−2 y−1 during the past century. 137Cs was used as an in-dependent chronometer. The two distinct peaks observed on the 137Cs record of both cores, corresponding to 1965 and 1986, have allowed a successful validation of the CRS model.

scholarly journals Seabirds: studies with parasitofauna and potential indicator for environmental anthropogenic impacts

2020 ◽  
Vol 41 (4) ◽  
pp. 1439
Author(s):  
Andressa Maria Rorato Nascimento de Matos ◽  
Camila Domit ◽  
Ana Paula Frederico Rodrigues Loureiro Bracarense
Keyword(s):  
Environmental Changes ◽  
Anthropogenic Impacts ◽  
Anthropogenic Activities ◽  
Marine Ecosystem ◽  
Population Monitoring ◽  
Public Health Importance ◽  
Seabird Species ◽  
Intrinsic Factors ◽  
Coastal Marine ◽  
Anthropogenic Threats

The aim of this review was to present the main anthropogenic threats to seabirds, a taxonomic group described as environmental sentinels, and the dynamics between parasites and hosts and their relationship with the health of the marine ecosystem. Coastal marine environments support various anthropogenic activities, exposing seabirds to multiple and synergistic environmental changes. These activities are considered negative to the maintenance of several seabird species, such as exposure to constant aquatic contaminants and fishing. In addition, parasitic and infectious diseases (viral, bacterial, and fungal) may also play an important role in maintaining some seabird populations. Some pathogenic organisms have public health importance and/or may indicate environmental quality. Host-parasite interaction may be positive, negative, or absent depending on some environmental factors potentially associated with degradation, as well as intrinsic factors of host or parasite. In addition, investigating aspects of seabird mortality also contributes to the constant population monitoring and understanding of the interaction between animals, humans, and the environment. Thus, seabirds and their parasitofauna can provide important ecological and health information, including those related to environmental health, supporting strategies for reducing degradation and maintaining marine ecosystems.

scholarly journals Anthropogenic impacts on mosquito populations in North America over the past century

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Ilia Rochlin ◽  
Ary Faraji ◽  
Dominick V. Ninivaggi ◽  
Christopher M. Barker ◽  
A. Marm Kilpatrick
Keyword(s):  
North America ◽  
Anthropogenic Impacts ◽  
Past Century ◽  
The Past

Contribution of Deforestation to Severe Flooding in Southeast Parts of the Caspian Sea: A Case Study with NDVI Analysis

2020 ◽  
Vol 07 (01n02) ◽  
pp. 2050008 ◽  
Author(s):  
Farahnaz Fazel-Rastgar
Keyword(s):  
Rural Areas ◽  
Caspian Sea ◽  
Vegetation Index ◽  
Environmental Changes ◽  
Discharge Rate ◽  
Past Century ◽  
The Caspian Sea ◽  
The Past ◽  
Color Composite ◽  
Severe Flooding

Iran has been faced with increase in flooding cases during the past 60 years. The human activities have been considered as a devastating factor in the environmental change causing the occurrence of severe flooding cases during past decades. On August 11, 2001, a relatively severe rainfall in the south east of Caspian Sea led to the occurrence of a severe deadly flooding in Golestan province and some parts in northern Khorasan province have been unprecedented in Iran over the past century. The destructive extent of flooding in the urban and rural areas reached about 5,000 km2. Here, the synoptic surface and upper levels of the weather charts have been analyzed along with the monitoring of half hourly METEOSAT7 images to show the convective clouds development over the area of the study. The total precipitation in this area during the flooding period was reported between 2.5 and 153 mm with the maximum estimation over the center of the storm around less than 250[Formula: see text]mm. Using satellite imagery in 1979 and 2000, vegetation changes and environmental changes have been investigated and shown extensive decline in vegetation. The image processing and Normalized Difference Vegetation Index (NDVI) calculation of the color composite 433 of LANDSAT5 and the color composite 211 of TERRA (MODIS sensor) images between 1998 and 2001 have been revealed significant deforestation around 248,131,534.3[Formula: see text][Formula: see text] over the study, particularly over the rivers’ neighborhood. Also, by assumption of the same precipitation for 1998 and 2001, the discharge rate in flood case of 2001 has been intensified 1.3 times (at 13 percent) larger than that of 1998. This shows the direct impact of the deforestation and land use changes over the study area during 1998–2001.

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