The current study focuses on the vertical profile of different geochemical fractions of phosphorus-loosely bound(Lo–P),aluminium bound(Al–P),iron bound(Fe–P),calcium bound(Ca–P),and organic bound phosphorus(O–P)along with ecological risk assessment of sediment cores from Chilika Lake,eastcoast of India.The percentage contribution of the different fractions to the sedimentary phosphorus in the sediment column of the whole lake are on the order:O–P(33.2%)>Ca–P(20.3%)>Fe–P(18%)>Al–P(6.7%)>Lo–P(0.35%).The Phosphorus Pollution Index(PPI)revealed the contamination of lake sediment with phosphorus.The principal component and cluster analyses highlighted the anthropogenic contribution of phosphorus.The negative loading of Ca–P with Ca points towards its origin from marine shells.The discriminate analysis showed that the variables like Ca–P,bio-available phosphorus(BAP),and pH were able to effectively discriminate the sectors in a significant manner. 相似文献
We refine the tephrostratigraphy and cryptotephrostratigraphy of the Middle Pleistocene deep-sea sediments in the C9001C cores and reconstruct the age model of the cores to provide a standard stratigraphy for the NW Pacific Ocean area. In the lower half of the cores (corresponding to marine isotopic stages [MISs] 9–18), we newly identify nine concentrations (spikes) of glass shards (numbered G17–G25 from top to bottom) below sixteen previously reported spikes (numbered G1–G16) in the upper half of the cores (MISs 1–9). We correlated two spikes (both cryptotephras) with known widespread tephras: G18 with Naruohama-IV (MIS 10d; 357 ka) and G19 with Kasamori 5 (MIS 12b–c; 434–458 ka). Although the two cryptotephra spikes cannot be distinguished by the major- and trace-element compositions of glass shards, these correlations are based upon their stratigraphic occurrence within separate glacial periods (MISs 10 and 12) as indicated by the δ18O stratigraphy of the C9001C sequence. Based on the stratigraphic positions of the Naruohama-IV and Kasamori 5 tephras, we assign the sediment units corresponding to MISs 10, 11, and 12, and revise the previous assignment of core segments corresponding to MISs 7, 8, and 9. The resulting tephra-based age model is consistent with the last occurrence of Proboscia curvirostris, but it is inconsistent with the first occurrence of Emiliania huxleyi. According to the new age model, the sedimentation rate during MISs 18–2 has ranged from 0.21 m/ky (during MIS 17) to 0.74 m/ky (during MISs 8 and 9), however, the sedimentation rate was never as high as the rate of 1.1 m/ky indicated by an earlier age model. 相似文献
In Southwest China, five Nature Reserves(NRs)(Mangkang, Baimaxueshan, Yunling, Habaxueshan, and Yunlongtianchi) play a key role in protecting the endemic and endangered Yunnan snub-nosed monkey(YSM)(Rhinopithecus bieti). However, increasing human activities threaten its habitats and corridors. We used a GIS-based Niche Model to delineate potential core habitats(PCHs) of the YSMs and a Linkage Mapper corridor simulation tool to restore potential connectivity corridors(PCCs), and defined five scenarios. A normalized importance value index(NIVI) was established to identify the protection priority areas(PPAs) for the YSMs for five scenarios. The results indicated that locations of the habitats and corridors were different in the five scenarios, thereby influencing the distribution of the PPAs and protection network of the YSMs. The NIVI value of Baimaxueshan nature reserve was 1 in the five scenarios, which implied the maximum importance. There were only 7 PCHs and 16 PCCs(with the longest average length of 223.13 km) which were mainly located around 5 NRs in scenario III. The protection network of the YSMs was composed of 16 PCHs, 18 PCCs, and 5 NRs. Under each scenario, most of the PCHs and the PCCs were located in the south of the study area. The five NRs only covered 2 PPAs of the YSMs. We suggest that the southern part of the study area needs to be strictly protected and human activities should be limited. The area of the five NRs should be expanded to maximize protection of the YSMs in the future. 相似文献
In Southwest China, five Nature Reserves (NRs) (Mangkang, Baimaxueshan, Yunling, Habaxueshan, and Yunlongtianchi) play a key role in protecting the endemic and endangered Yunnan snub-nosed monkey (YSM) (Rhinopithecus bieti). However, increasing human activities threaten its habitats and corridors. We used a GIS-based Niche Model to delineate potential core habitats (PCHs) of the YSMs and a Linkage Mapper corridor simulation tool to restore potential connectivity corridors (PCCs), and defined five scenarios. A normalized importance value index (NIVI) was established to identify the protection priority areas (PPAs) for the YSMs for five scenarios. The results indicated that locations of the habitats and corridors were different in the five scenarios, thereby influencing the distribution of the PPAs and protection network of the YSMs. The NIVI value of Baimaxueshan nature reserve was 1 in the five scenarios, which implied the maximum importance. There were only 7 PCHs and 16 PCCs (with the longest average length of 223.13 km) which were mainly located around 5 NRs in scenario III. The protection network of the YSMs was composed of 16 PCHs, 18 PCCs, and 5 NRs. Under each scenario, most of the PCHs and the PCCs were located in the south of the study area. The five NRs only covered 2 PPAs of the YSMs. We suggest that the southern part of the study area needs to be strictly protected and human activities should be limited. The area of the five NRs should be expanded to maximize protection of the YSMs in the future.
Holocene δ18O records from various archives (ice cores, cave stalagmites, and peat sediments) from the Xinjiang region of northwestern China, in arid central Asia (ACA), are all derived ultimately from local precipitation δ18O (δ18Op). Nevertheless, they have been proposed as indicators of different climatic parameters, such as wetness and temperature changes. This article summarizes previously reported records of moisture sources for the Xinjiang region and the results of modern observations conducted at an ice core site and a peat site in the Altai Mountains. The findings are used to propose that the overall positive trends in Holocene δ18O records from the various archives from the Xinjiang region primarily reflect the Holocene's long-term warming trend. It is concluded that more site-specific modern observations are needed to further elucidate the environmental significance of Holocene δ18O records from this region, especially for the separation of different seasonal temperature signals present within δ18O records. 相似文献