Based on high-resolution analysis to a 280-cm long sediment core obtained from the muddy area in the central Yellow Sea, we examined the provenance of muddy sediments and discussed the changing marine sedimentary envi...Based on high-resolution analysis to a 280-cm long sediment core obtained from the muddy area in the central Yellow Sea, we examined the provenance of muddy sediments and discussed the changing marine sedimentary environment since the middle Holocene. The results indicated that fine-grained sediments in the muddy area were mainly derived from the Huanghe(Yellow River) and Changjiang(Yangtze River) with considerable stepwise variations during the past 6.6 kyr. The Yellow Sea Warm Current was initiated at 6 kyr when the sea level was high together with the enhanced East Asian Winter Monsoon. These in combination established the framework of shelf circulation in the Yellow Sea that began to trap the river-derived fine-grained sediments. From 4.9 kyr to 2.8 kyr, both the Kushiro Current and East Asian Monsoon were significantly weakened, reducing the delivery of Changjiang sediments to the muddy area. As a result, the sediments were mainly originated from the Huanghe. From 2.8 kyr to 1.5 kyr the continuously weakened East Asian Winter Monsoon and enhanced Yellow Sea Warm Current entrapped more fine-grain sediments. Whereas the enhanced East Asian Winter Monsoon and the human caused increase in sediment load of the Huanghe since 1.5 kyr, and direct delivery of Huanghe sediments to the Yellow Sea during 1128–1855 AD might dominated the sedimentation in the study area. The stepwise variations of the sediment provenance and composition of the Central Yellow Sea muddy sediments are of importance to understanding the formation of muddy deposit in the central Yellow Sea and the associated variations of marine environment since the middle Holocene.展开更多
Nutrient loadings from upstream watersheds can have significant impacts on the water quality of receiving water bodies.Usually,a major river is selected as the target for water quality studies,and the impact of minor ...Nutrient loadings from upstream watersheds can have significant impacts on the water quality of receiving water bodies.Usually,a major river is selected as the target for water quality studies,and the impact of minor rivers tends to be ignored.It is very important to evaluate whether the impact of small rivers on the downstream water quality is negligible.River water sampling and discharge modeling using SWAT were used to analyze the contribution of small rivers to water quality in a receiving lake.From this analysis,it was determined that the inflowing total nitrogen(TN)and total phosphorus(TP)concentrations from all target rivers exceeded the lake water environmental standards set by the Ministry of the Environment.The contribution of suspended sediment(SS)and TN loads from small rivers did not vary markedly compared with their relative discharge contributions to the lake,at approximately 20%.However,the impact on TP loads to the lake from small rivers was 9.1%higher than their relative flow contributions,accounting for 28.2% of the TP loading.Thus,there is a potential to underestimate the impact of ungauged small rivers if only the major river is selected to evaluate the downstream lake water quality.展开更多
基金financially supported by National Natural Science Foundation of China (Nos.41525021 and U1606401)。
文摘Based on high-resolution analysis to a 280-cm long sediment core obtained from the muddy area in the central Yellow Sea, we examined the provenance of muddy sediments and discussed the changing marine sedimentary environment since the middle Holocene. The results indicated that fine-grained sediments in the muddy area were mainly derived from the Huanghe(Yellow River) and Changjiang(Yangtze River) with considerable stepwise variations during the past 6.6 kyr. The Yellow Sea Warm Current was initiated at 6 kyr when the sea level was high together with the enhanced East Asian Winter Monsoon. These in combination established the framework of shelf circulation in the Yellow Sea that began to trap the river-derived fine-grained sediments. From 4.9 kyr to 2.8 kyr, both the Kushiro Current and East Asian Monsoon were significantly weakened, reducing the delivery of Changjiang sediments to the muddy area. As a result, the sediments were mainly originated from the Huanghe. From 2.8 kyr to 1.5 kyr the continuously weakened East Asian Winter Monsoon and enhanced Yellow Sea Warm Current entrapped more fine-grain sediments. Whereas the enhanced East Asian Winter Monsoon and the human caused increase in sediment load of the Huanghe since 1.5 kyr, and direct delivery of Huanghe sediments to the Yellow Sea during 1128–1855 AD might dominated the sedimentation in the study area. The stepwise variations of the sediment provenance and composition of the Central Yellow Sea muddy sediments are of importance to understanding the formation of muddy deposit in the central Yellow Sea and the associated variations of marine environment since the middle Holocene.
基金supported by the Fundamental Research Funds for the Central Universities,China(lzujbky-2021-ey12)the National Natural Science Foundation of China(42072211)+1 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2019QZKK0602)the National Non-Profit Fundamental Research Grant of China(IGCEA 2008)。
基金This study was partially supported by two grants-in-aid for scientific research:KAKENHI:24780234 and 25281054.
文摘Nutrient loadings from upstream watersheds can have significant impacts on the water quality of receiving water bodies.Usually,a major river is selected as the target for water quality studies,and the impact of minor rivers tends to be ignored.It is very important to evaluate whether the impact of small rivers on the downstream water quality is negligible.River water sampling and discharge modeling using SWAT were used to analyze the contribution of small rivers to water quality in a receiving lake.From this analysis,it was determined that the inflowing total nitrogen(TN)and total phosphorus(TP)concentrations from all target rivers exceeded the lake water environmental standards set by the Ministry of the Environment.The contribution of suspended sediment(SS)and TN loads from small rivers did not vary markedly compared with their relative discharge contributions to the lake,at approximately 20%.However,the impact on TP loads to the lake from small rivers was 9.1%higher than their relative flow contributions,accounting for 28.2% of the TP loading.Thus,there is a potential to underestimate the impact of ungauged small rivers if only the major river is selected to evaluate the downstream lake water quality.
