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Soil layers affect the vertical movement of moisture and salt, eventually resulting in land cover and land use pattern changes. This study explored the ability of ground penetrating radar (GPR) to detect soil layers in the modern Yellow River Delta of China and assessed its accuracy. It was found that soil moisture and salt had a strong dampening effect on the electromagnetic wave signal which resulted in blurred GPR images of the soil profile below 1 m. The cultivated soil layers of different crop types, such as rice, wheat, corn and cotton, were accurately identified in GPR images. To estimate an individual soil layer thickness, the propagation velocity of the electromagnetic wave was calculated using soil mass moisture content, and the propagation time was confirmed by comparing the GPR image with the amplitude–time plot of the soil profile. The estimated thickness was 1.02 times the thickness determined in the field and the average estimation error was 0.04 m, which was 24.09% of the soil layer thickness determined in the field. The second derivative value of envelope amplitude energy with time (SDEA) was used to describe the amplitude change in the soil layers. The SDEA has negative logarithmic and power function relationships with soil mass moisture content and electrical conductivity, respectively. The present results provide a reference database for future quantitative soil investigation in the sedimentary plain area using GPR. [ABSTRACT FROM AUTHOR]

The mining of coal mines in western China needs to focus on protecting groundwater. A non-hydrophilic similar material for simulating the development and hydraulic conductivity of weakly cemented overlying strata fractures was developed. Fine sand, coarse sand, and gypsum are used as aggregates. Paraffin and Vaseline are used as binders. The non-hydrophilic material ratios of weakly cemented sandy mudstone and medium-grained sandstone were determined by orthogonal experiments, and used for similar simulation tests. The results show that the non-hydrophilicity of rock-like materials can be adjusted to prevent them from softening and collapsing under the action of water. Non-hydrophilic materials of higher strength and brittleness of rocks can be achieved by adjusting the content of paraffin, fine sand, and gypsum. The non-hydrophilic materials of soft and large particle rocks can be achieved by adjusting the content of paraffin, fine sand, and gypsum. After the coal seam in a similar simulation experiment was extracted, the large area of weakly cemented rock above it underwent overall settlement and fracture. Although this part was located within the failure zone, there was no macroscopic water-conducting cracks generated. The height of the water-conducting fracture zone was lower than the height of the fracture zone classified by the traditional 'three zone' theory, which is consistent with the on-site measurements. This indicates that the prepared non-hydrophilic material is reliable. The similarity simulation method based on non-hydrophilic materials can enrich the means for studying the fracture and permeability of weakly cemented overlying rocks in coal mines. [ABSTRACT FROM AUTHOR]

Weakly cemented medium-grained sandstone in Ordos mining area of China is widely distributed under phreatic water. The creep behavior of saturated rock is important for the stability of water-resisting strata. In this paper, creep mechanical properties of saturated medium-grained sandstone were studied by triaxial rheological test. The results showed that medium-grained sandstone only shows attenuation creep and stable creep under low stress level, and accelerated creep occurs when axial load reaches about 75% of instantaneous compressive strength. The rock samples exhibit volume dilatancy under most loading levels and finally shear fracture. The failure mechanism is the dislocation separation of mineral particles. Based on the energy dissipation theory, the damage evolution equation was modified and introduced into the Burgers model, which can accurately describe the rheological behavior of saturated medium-grained sandstone. The modified model was used to predict the crack initiation time under different deviatoric stresses, which can provide guidance for early warning of water-resisting rock stability. [ABSTRACT FROM AUTHOR]

China has a wetland area of 53.42 million hectares, the fourth largest in the world; it includes all types of wetlands defined by the Ramsar Convention and has a carbon sink capacity of more than 1.71 million metric tons per year. Inland wetlands in China are mainly distributed in 10 major catchments, among which the Yellow River, the Yangtze River, the rivers in the northwest, and the rivers in the northeast each have more than 8 million hectares of wetlands. There are 4220 species of plants and 4015 species of animals in China's wetland ecosystem. The wetland resources that have been developed and utilized include edible products, reeds for paper making, peat for fertilizer, fuel for power generation, and chemical, pharmaceutical, ceramic, and building materials. However, wetland areas in China have shrunk by about 54% since 1980. In recent years, China's central government has set great store by Chinese wetlands, and although 49.03% of wetland area is now officially protected, many issues have confounded the implementation of that protection. It is imperative that knowledge gained from scientific research be used to formulate a sound wetland protection and management plan that takes into consideration social, economic, and ecological issues in a way that facilitates the sustainable use of wetland resources and informs decision-makers of the paths that must be followed to achieve that goal. [ABSTRACT FROM AUTHOR]

Grain size and concentrations of organic carbon (Corg) and particulate metals (PMs) As, Cd, Cr, Cu, Hg, Pb, Zn, Al, Fe, and Mn of 373 surface sediment samples, salinities in 67 surface water samples, were analyzed in various environments, including the upper delta plain wetlands (UDPW), its adjacent shallow sea wetland (SSW) in the Liaodong Bay, and river channels that are running through the Liaohe Delta, to evaluate the spatial distribution, transportation environmental dynamics of metals, and the provenance of metal pollution and assess the filtration functions of wetlands. The concentrations of PMs for UDPW were generally higher by a factor of ~ 10–22% compared with its analogues in SSW, suggesting the accumulation of PMs within the UDPW indicates that the UDPW systems are efficiently physical and chemical traps for PMs of anthropogenic sources by retaining and storing pollutants flowing into the sea. However, there was sever sewage irrigation-induced Cd pollution with a geo-accumulation index of 0.62–3.11 in an area of ~ 86 km2 of the adjacent shallow sea wetland, where large amount wetlands were historically moved for agriculture in the UDPW. Remarkably, the distributions of PMs were controlled by salinity-induced desorption and re-adsorption mechanisms and significantly dispersed the contamination coverage by the three-dimensional hydrodynamic and sedimentation processes that dominated by inputs of freshwater and ocean dynamics including NE-SW tidal currents and NE-E longshore drifts in the SSW of the Liaodong Bay. A high agreement between the UDPW and the SSW datasets in principal component analysis essentially reflects that the characteristics of PM sources in the SSW were actually inherited from that in the UDPW, with a much closer relationship among metals, organic matter, and fine particulates in SSW than that of UDPW, which was judged by their correlation coefficient range of 0.406–0.919 in SSW against those of 0.042–0.654 in UDPW. [ABSTRACT FROM AUTHOR]

The heavy metal (Cr, Cu, Ni, Pb, and Zn) content and particle size of surface sediment samples taken from 123 sites in the Bohai Strait of China were analyzed. All five heavy metals showed a similar distribution in the Bohai Strait, with lower concentrations in the middle and higher concentrations at the sides of the strait. The amount of heavy metals was lowest in the Laotieshan Channel due to the rapid current in this channel. According to our calculated values of the pollution index (Pi), only 1.6 % of the sample sites were polluted by Cr and Cu. The calculated geo-accumulation index (Igeo) values showed that few of the sites were polluted by heavy metals. The level of Pb was controlled by both terrigenous inputs and clay adsorption, while the levels of the other heavy metals (Cr, Cu, Ni, and Zn) were mainly controlled by terrigenous inputs. • Heavy metals in 123 sediment samples from the Bohai Strait were analyzed. • Some sites in the strait are polluted, but the area studied is not polluted overall. • Heavy metals in the strait are mainly controlled by terrigenous inputs. • Heavy metals in the Laotieshan Channel are strongly affected by the ocean current. [ABSTRACT FROM AUTHOR]

Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO2 concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO2 and CH4 emissions at large spatial scales are limited. We investigated three-year emissions of soil CO2 and CH4 from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km2. One percent is Suaeda salsa, 24% is Phragmites australis, and 75% is rice. While S. salsa wetlands are under somewhat natural tidal influence, P. australis and rice are managed hydrologically for paper and food, respectively. Total C emissions from CO2 and CH4 from these wetland soils were 2.9 Tg C/year, ranging from 2.5 to 3.3 Tg C/year depending on the year assessed. Primary emissions were from CO2 (~98%). Photosynthetic uptake of CO2 would mitigate most of the soil CO2 emissions, but CH4 emissions would persist. Overall, CH4 fluxes were high when soil temperatures were >18°C and pore water salinity <18 PSU. CH4 emissions from rice habitat alone in the Liaohe Delta represent 0.2% of CH4 carbon emissions globally from rice. With such a large area and interannual sensitivity in soil GHG fluxes, management practices in the Delta and similar wetlands around the world have the potential not only to influence local C budgeting, but also to influence global biogeochemical cycling. [ABSTRACT FROM AUTHOR]

Gao, M.; Liu, S.; Zhao, G.; Yuan, H.; Wei, C.; Wu, Y., and Tang, J., 2014. Vulnerability of eco-hydrological environment in the Yellow River delta wetland. We investigated the relationship between groundwater head and oceanic tidal fluctuations in the Yellow River Delta wetland through on-site hydrological monitoring. Shallow groundwater heads were obviously affected by oceanic tide along the coastal zone. The ranges of the wetland zone can be readily assessed by measuring fluctuation amplitudes or lags. The results show that the influence radius is approximately 12 km to 18 km (when the correlation coefficient is 0.7 to 0.8) under the joint actions of oceanic tide and shallow groundwater seepage flow in clayey silt coastal wetland. A cross-sectional sketch of the coastal wetland model is developed based on monitoring data of groundwater and oceanic tidal fluctuations to study the vulnerability of the eco-hydrological environment in the Yellow River Delta wetland. The coastal wetland consists of three zones (the groundwater seepage zone, the tidal-induced transitional zone, and the tidal zone) with distinctly different hydraulic properties. Analytical solutions are used to estimate the vulnerability of the eco-hydrological environment in the wetland aquifer located in the NE part of the Yellow River Delta wetland, Shandong Province, China. Our results show that changes in the shallow groundwater quality of the wetland are significantly affected by natural factors, such as strong cutoff in the lower reaches, storm tides, and human engineering activities. The northern coastal wetland may be submerged without damp proof when the height of a storm tide reaches 2.4 m. The depth of shallow groundwater and the salinity gradient are key factors that contribute to the vulnerability of the ecological environment. The vulnerability of the eco-hydrological environment is derived from the joint actions of groundwater dynamics, hydrochemistry, and tidal-induced processes under sedimentary stress and water pressure. [ABSTRACT FROM AUTHOR]

China consumes more than 1/3 of global N fertilizers for rice with less than 1/5 of the world rice planting area. As a consequence, N efficiency is low and nitrate pollution risk is high. Developing efficient N management strategies and technologies for rice are therefore needed. Here, we developed an active canopy sensor-based precision N management strategy for rice in Northeast China. Four site-years of field N rate experiments were conducted in 2008 and 2009 in Sanjiang Plain, Heilongjiang, China. The GreenSeeker active sensor was used to collect rice canopy reflectance data at different growth stages. Three on-farm experiments were conducted in 2011 to evaluate the performance of the developed strategy. The results show that the crop sensor can be used to calculate rice yield potential without additional topdressing N application at stem elongation or booting stage. The GreenSeeker-based precision N management strategy has a regional optimum N rate of 90-110 kg N ha as initial total amount and 45 and 20 % as basal and tillering N application. It uses the crop sensor to estimate the topdressing N rate at stem elongation stage. GreenSeeker-based precision management and chlorophyll meter-based site-specific N management increased the partial factor productivity of farmers by 48 and 65 %, respectively, without significant change in grain yield. The crop sensor-based N management strategy can therefore improve N use efficiency of rice. It is more suitable for practical on-farm applications, and will contribute to the sustainable development of rice farming. [ABSTRACT FROM AUTHOR]

The distributary lobe of the modern Yellow River Delta formed after 1855 was 15 m in thickness before it was abandoned, where the compaction subsidence has reached as high as 2.28∼3.87 m in the past 30 years. The compaction ratio of clayey silty sand (25.8%) is 1.7 times greater than that of silty sand (15.2%). It means that the compaction process has basically terminated. On the other hand, the compaction subsidence of underlying sediment is quite limited and shows an insignificant difference. For example, for the underlying sediment of 20∼30 m in thickness, the subsidence varies between 0.2 and 0.28 m. The average compaction ratio of clayey silty sand is 0.91%, while that of silty sand is 1.19%, and the average compaction ratio of all sediment is 1%. There's a negative exponential function relationship between porosity and burial depth of the sediment, and the higher the clay content, the more difficult it is for pore water to drain. The superficial sediments contribute more to the compaction subsidence than the underlying strata. [ABSTRACT FROM PUBLISHER]

Samples of porewater and the edible tissue of mottled clams, Ruditapes variegatus, were collected simultaneously at each of 12 stations from Jiaozhou Bay near Qingdao, China, in June of 2003. Chemical analysis focused on trace metals and major elements. Porewater concentrations of Cd, Cr, Pb, and Zn were distributed in a bimodal fashion among the 12 stations, with mean concentrations at six of the stations being 8-32 times mean values at the other six stations. The concentrations of the same metals in clams were remarkably similar among stations, the coefficients of variation being only 12-37%. Calculations performed with the computer program PHREEQC indicated that Pb and Cr in porewater were present only in the +2 and +3 states, respectively, and because dissolved Cd and Zn exist only in the +2 state, the bimodal distribution of these four metals likely reflects secondary effects associated with their scavenging by Fe and/or Mn under oxidizing conditions and subsequent dissolution in the reducing environment of the porewaters. Consistent with this hypothesis is the fact that the distribution of high and low metal concentrations was closely correlated with the granularity of the sediment, with lower metal concentrations associated with relatively coarse sediment. Comparison of published biological concentration factors with the ratios of metal concentrations in the clams to porewater metal concentrations indicated that the porewaters were not the primary sources of the metals in the clams. Mixing processes in the bay likely account for the rather uniform concentrations of metals in clam tissue. [ABSTRACT FROM AUTHOR]

• Sedimentary environments were divided into six depositional units. • The biggest contributor to OC-AMAR was the negative covariance between ASR and OC. • Terrestrial organic matter has been decreasing since 6500 cal. a BP. • Climate may affect the dynamics of carbon burial by regulating terrestrial inputs. The ancient Yellow River Delta (YRD) on the west coast of the Bohai Bay is possibly a huge carbon sink due to the high runoff and sediment load of the Yellow River, which transfers huge amounts of particulate carbon from terrestrial sources to the Bohai Sea. In this study, a 30.76 m long core (BXZK11), drilled in 2016, has been analyzed for AMS 14C dating, grain size, foraminifera, organic carbon (OC), total nitrogen (TN), and stable carbon isotope ratios (δ13C) to provide insights into the historical changes of carbon burial in Late Quaternary sediments of the ancient YRD. The results show that the sedimentary environments are divided into six depositional units in core BXZK11. The biggest contributor to organic carbon apparent mass accumulation rate (OC AMAR) is the negative covariance between apparent sedimentation rate (ASR) and OC. The average of OC AMAR is 20.76 g/(m2 yr) during the Holocene. The rates are highest in delta front deposits and lowest in shallow sea environments. Compared with the modern YRD, BXZK11 exhibits rather low ASR and OC AMAR , indicative of the enormous variations of Yellow River sediment load into the sea and the significant difference of carbon sequestration capacity of YRD at different periods. C3 plants of the delta wetland gradually develop without C4 plant input as the delta transgresses after sea level stabilization. The sediments have been characterized by decreasing terrestrial organic matter (TOM) since 6500 cal. a BP, reflecting the decline of Yellow River freshwater discharge. Both the 8.2 ka event and the weak Asian monsoon summer event at 6265 cal. a BP correspond well with the low TOM in BXZK11. The implication is that climate may affect the dynamics of carbon burial by regulating terrestrial inputs. [ABSTRACT FROM AUTHOR]

Three hundred five surface sediment samples from the Bohai Bay in northeastern China were examined for grain size, organic carbon (Corg) concentration, and concentrations of heavy metals (Pb, Zn, Cu, As, Cr, Cd, and Hg). Average metal concentrations were 33 mg/kg (Cu), 27 mg/kg (Pb), 95 mg/kg (Zn), 75 mg/kg (Cr), 0.3 mg/kg (Cd), 13 mg/kg (As), and 72 μg/kg (Hg). In most cases, these concentrations were lower than the China Marine Sediment Quality criteria. Enrichment factors, however, suggested moderate to strong Cd and Hg contamination of the Bohai Bay. The fact that 68.6% of Pollution Load Index (PLI) values exceeded 2 demonstrated strong pollution of the Bohai Bay, Hg contributed the most to the PLI. Pollution in the surface sediment of the Bohai Bay, China was assessed. Metal concentrations generally met the China Marine Sediment Quality criteria. Metals Cd and Hg showed moderate to strong pollution in some stations. About 68.6% of the sites had strong pollution based on Pollution Load Index method. [ABSTRACT FROM AUTHOR]

Delta wetland sediments constitute a long-term natural carbon sink and play a critical role in the global carbon cycle. In this study, borehole core ZK3 (36.7-m long), drilled in 2012 in the Liaohe Delta wetland, was investigated to assess the rate of carbon sequestration and the factors influencing carbon burial since the Late Pleistocene. Here we report the results of integrated analyses of the core, including its sedimentary lithology, grain size, foraminiferal abundance, chemical elements, and accelerator mass spectrometry (AMS)14C and optically stimulated luminescence (OSL) dates. The sedimentary environment has evolved from a fluvial-deposit, limnetic-deposit, littoral-deposit, shallow sea–deposit, and finally to a delta-deposit environment since 40,000 cal yr BP. Environmentally induced differences in apparent mass accumulation rates (AMARs) of organic carbon (OC) have been significant; they have ranged between 3.73 and 30.77 g/(m2·yr). The fact that the highest rates were associated with the delta-deposit environment indicates that the rate of carbon sequestration was greater in the sediments of estuarine wetlands than sediments of the continental shelf. The chemical index of alteration (CIA) proxy responded to several cold events, and there was a positive correlation between the CIA and OC-AMAR. Climate may therefore have regulated the excursions of ecosystem productions and in turn impacted the dynamics of carbon burial. [ABSTRACT FROM AUTHOR]

Mangrove forests are ecologically and economically significant ecosystems in the (sub)tropics, and it is important to reconstruct their historical changes to understand the future of mangrove forests in the context of global warming. Although the Holocene climatic optimum (HCO) is regarded as an analogue of future climatic change, high-resolution studies of mangrove ecosystem changes during this period are rare. This study presents a high-resolution sedimentary record for the HCO (7800–6900 cal. yr BP) in the Maowei Sea, northern Beibu Gulf, China. Contributions of mangrove-derived organic matter in the sediments were quantified using an end-member mixing model and a Monte Carlo simulation. The model reveals there were high-frequency degradation events (11 times) of the mangrove forests during 7800–6900 cal. yr BP. Palaeo-environmental records (e.g., sea-level, stalagmite δ18O values, and sediment Ti contents) from near the study area demonstrate that an intensified Asian winter monsoon (AWM), rather than sea-level changes, was the key factor responsible for the high-frequency mangrove degradation events during the HCO in this region. The results indicate that the effects of the intensified winter monsoon on tropical ecosystems may be greater than previously thought, particularly in the context of anthropogenic warming scenarios. • Contributions of mangrove-derived organic matter (MOM) were quantified in a sediment core from tropical China. • Eleven mangrove degradation events during the Holocene Climatic Optimum were identified through MOM. • The intensified Asian winter monsoon was the primary factor of high-frequency mangrove degradations. [ABSTRACT FROM AUTHOR]

• Coupled variable density flow and reactive processes in coast groundwater system were investigated. • Model results revealed well the main controlling factors to hydrochemical changes under the impact of pumping activity. • The aquifer matrix in pumping region and saline/fresh water transition may undergo irreversible changes. Intensive pumping activities threaten the coast groundwater environment and have a negative impact on aquifer systems. A comprehensive understanding of these effects is important for the management of coastal groundwater resources. However, this is challenging, particularly for coastal saline groundwater systems due to complex water–rock interactions. In this study, a coupled variable–density flow and hydrochemical reaction model was used to examine the effects of pumping activities on the groundwater environment on the southern coast of Laizhou Bay, China, which is a typical muddy coast. The model successfully captured the hydrodynamic and hydrochemical changes, and the water–rock interactions, during three different exploitation stages: (1) evaporation and water–rock interactions were the primary controls on groundwater evolution during the weakly pumped stage (before 1995); (2) the groundwater level began to decrease and saltwater intrusion was aggravated during the small pumping stage (1995–2005); and (3) significant hydrodynamic and hydrochemical changes occurred at the saline/freshwater transition and pumping zones during a period of intensive pumping (after 2005). Our findings revealed that water–rock interactions are the primary drivers of hydrochemical evolution at the saline/freshwater transition and seaward saline groundwater zone, whereas hydrodynamic changes are the main drivers in the pumping and deep saline–brine water zones. Furthermore, we discussed the effects of hydrodynamic variations and water–rock interactions on the aquifer matrix and identified that irreversible changes occurred mainly in the pumping zone and saline/freshwater transition. In conclusion, our study highlights the importance of considering both hydrodynamic and hydrogeochemical factors when managing coastal groundwater resources. By developing a better understanding of these complex interactions, we can minimize the negative impacts of pumping activities and preserve the long-term sustainability of coastal groundwater resources. [ABSTRACT FROM AUTHOR]

• Analogy of surface and fossil pollen reveal the transgression process in Liaodong Bay. • The Holocene coastal vegetation is a meadow with a fluctuation forest in the hills. • Salt marsh wetlands along the estuary of Daliaohe River formed ca. 1470 cal yr BP. • The vegetation changes mainly driven by the East Asia monsoon and sea level change. To reconstruct the Holocene vegetation history from Liaohe Delta in northeast (NE) China, a high-resolution palynological study on a well-dated sediment core ZK2 was conducted. The pollen record of ZK2 suggests that during the early Holocene, the regional vegetation in the plain was meadow-dominated by Artemisia. And forest with cool-temperate conifers and temperate broad-leaved trees were present in the nearby hills, which is coincident with the gradual climate warming and delta transgression. From mid-Holocene to early late Holocene, meadow vegetation with Artemisia was relatively stable, while the forest vegetation with broadleaved trees reached the maximum expansion in the nearby hills. The large expansion of broadleaved trees indicates warm and humid regional environmental conditions and this is coincidental with the relatively high regional sea-level stand during this period. Since ca. 1470 cal yr BP, with the continuous delta progradation, a large coastal region was colonized by Suaeda spp., which suggests that the formation of unique red beach wetlands along the coastal region of the Liaohe Delta. By analysis of pollen dispersal and transportation mechanism in surface sediments of Liaodong Bay, it is indicated that the percentage changes of arboreal pollen dominated by Pinus and Quercus and the non-arboreal pollen dominated by Amaranthaceae and Artemisia in core ZK2 may as an index refers to the local sea level oscillation and paleoclimate change. Then by comparison with previous multi-proxy records together with the surface sediment record from Liaodong Bay, it is suggested that the Holocene vegetation changes of the Liaohe Delta are mainly driven by the intensity changes of East Asia monsoon and regional sea-level oscillation. [ABSTRACT FROM AUTHOR]

• Surface pollen concentration is proportional to content of silt and clay. • Both Pinus and fern spores showed a gradual increase toward the deeper waters. • Yellow River input dominated the pollen provenance in the Bohai Sea. • Circulation are the main driving forces for pollen-spore transport. • Fluctuations of fossil Pinus and herbs revealed the sea level and climate changes. To elucidate the mechanisms responsible for pollen and spore transportation and deposition in the Bohai Sea, fully covered seafloor-surface sediment samples were collected for palynological and grain size analysis. The results reveal that the pollen and spore concentrations were higher in the head of Liaodong Bay and in the muddy area of the Bohai Sea. The Yellow River was the main source of pollen and spores in the Bohai Sea. The sediments with relatively high pollen concentrations consisted mainly of clay and fine silt, whereas sediment with lower pollen concentrations was mostly fine sand. In addition, the percentages of Pinu s pollen and pteridophyte spores increased with increasing sea water depth, while other arboreal (excluding Pinus) and herbaceous pollen generally decreased with increasing distance from the shore. The relationship between the pollen taxa and the water depth of the sampling points shows that the fluvial water plays a predominant role in pollen transmission within 20 m of water depth, while the wind is the main driving force for pollen transmission when the water depth exceeds 20 m. Although Pinus pollen and pteridophyte spores were over-represented, there was good correlation between marine pollen signals and terrestrial vegetation. Apart from the influence of rivers and wind on pollen and spore deposition, the tidal currents and circulation were also main force responsible for transporting sediment and determining the differentiation of pollen and spores in the Bohai Sea. The comparison of pollen and spore percentages between surface sediment and fossil records from sedimentary cores made it possible to identify changes in pollen sources and transport mechanisms. Meanwhile, the percentage fluctuations of fossil Pinus and herbaceous pollen revealed concomitant changes of the sea level and climate. These findings are of paramount importance to the interpretation of Quaternary marine pollen data from the Bohai Sea, China. [ABSTRACT FROM AUTHOR]

To better understand the provenance and transport paths of modern pollen and spores in the Bohai Sea, we analyzed 104 surface alluvial samples from its sixteen inflowing rivers and 56 modern surface pollen samples from around Bohai Sea in the East Asia Surface Pollen Database. Our results revealed that the pollen assemblages of the inflowing rivers were dominated by non-arboreal pollen types, which accounted for an average of 60% of the pollen and were represented primarily by Chenopodiaceae; the percentages of arboreal pollen reached an average of 23%; fern spores accounted for the lowest percentage of the spores and pollen. The characteristics of the pollen assemblages in the alluvium of the inflowing rivers, especially large rivers, reflected the vegetation of upstream sampling points rather than the characteristics of the vegetation around the sampling points. The vegetation types represented by the pollen and spores in the short-source rivers or seasonal rivers were beyond the range of the drainage basin, especially the trees and ferns, and differences of the watershed vegetation of the inflowing rivers led to different pollen assemblages in the alluvium in the study area. The Yellow River is the main source of modern surface pollen in the Bohai Sea. Unlike the pollen of the inflowing rivers, the pollen assemblages in the Bohai Sea were dominated by arboreal pollen, especially Pinus. The fern spores were dominated by Selaginella , but non-arboreal pollen accounted for relatively low percentages of the pollen. • The alluvial samples from its 16 inflowing rivers around Bohai Sea were firstly studied. • The pollen assemblages in the alluvium reflected different areas in different rivers. • The Yellow River is the main source of modern surface pollen in the Bohai Sea. [ABSTRACT FROM AUTHOR]

This study comprehensively assesses spatial distribution, pollution levels, and potential sources of heavy metal(loid)s in surface sediments across multiple river systems along the coastal area of the East China Sea. Copper in Qiantang River and Xiangshan Bay showed higher concentations and exceeded the threshold effect value, while the higher content of Lead was mainly found in the Saijiang River, Oujiang River, and Minjiang River. Heavy metal(loid)s in the alluvium of Qiantang River, Jiaojiang River, and Yangtze River showed low to moderate pollution levels, with Cd posing the highest ecological risk, followed by Hg. Meanwhile, Qiantang River, Jiaojiang River, Yangtze River, and Oujiang River exhibited considerable to moderate ecological risks and low toxic risk. PMF model analysis results reveal that concentrations of Cr, Ni, and As were closely related with natural geogenic input (36.56 %), while industrial and traffic activities (48.77 %) were primary source of Cu, Pb, Zn, and Hg, and main source of Cd was agricultural emissions (14.67 %)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Studies of heavy metal pollution are essential for the protection of coastal environments. In this study, positive matrix factorization (PMF) and a GeoDetector model were used to evaluate the sources of heavy metal contamination and associated ecological risks along the Yancheng Coastal Wetland. The distribution of heavy metals was shown to be greatly affected by clay content, except for Cr in shoal. Components from 6.5 to 9φ have the strongest ability to absorb heavy metals, where the effects of Cd and Zn sequestration in the wetlands were most apparent. The abilities of various wetland environments to sequester heavy metals were shown to be Spartina alterniflora wetland > woodland > Phragmites australis wetland > aquaculture pond > shoal > paddy > meadow > dry land. The sources of the heavy metals included parent soil material (59%), agriculture (15%), and industrial pollutants (26%). According to the single-factor pollution index, there was no evidence of pollution except Cr and Pb. In general, the heavy metal pollution was insignificant. The order of pollution loading index was shoal > paddy field > dry land > Spartina Alterniflora wetland > aquaculture ponds > woodland > meadow > Phragmites australis wetland. The ecological harm of heavy metal exposure was slight except for Cd and Hg, where vehicle emissions appeared to be the main cause of heavy metal pollution., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Understanding pollen transport pathways and dispersal mechanism from the land to sea is a prerequisite for marine palynological study. Palynological analysis of 164 surface sediment samples in Liaodong Bay, and 39 analogous surface alluvium samples from its five inflowing rivers, identifies the distribution patterns, pathways and possible sources of pollen and spores. The results show that pollen and spore assemblages in surface sediments are well correlated to regional vegetation distribution, and the variations of pollen assemblage in different parts of Liaodong Bay reflected local vegetation changes along the coast. High pollen concentrations are mainly distributed in the estuaries of inflowing rivers, coastal waters and sea muddy areas. The pollen assemblage characteristics of alluvial samples are similar to those from coastal waters with water depths <8.5 m. Samples from the alluvium and surface sediments of coastal waters were dominated by herbaceous pollen taxa including Artemisia, Amaranthaceae, Poaceae, Cyperaceae and Typha. Herbaceous pollen percentages and concentrations decreased as the water depth increased, indicating that pollen and spores in the coastal waters of Liaodong Bay are mainly carried by the inflowing rivers. However, pollen assemblages for samples with water depth >8.5 m are significantly different from those of the alluvium. In samples taken below a depth of 8.5 m, the arboreal pollen is dominated by airborne Pinus, and there is a high number of the waterborne Selaginella fern spores, both of which are sourced from a wider region. In the Liaodong Bay, both wind and ocean current transportation determines the pollen distribution patterns in deeper waters, while fluvial and longshore current transportation determines the pollen assemblages found in shallow waters. The dispersal characteristics of pollen assemblages between the land and the sea in Liaodong Bay provide a theoretical basis for the interpretation of fossil pollen assemblages and past sea level changes., Competing Interests: Declaration of competing interest There is no conflict of interest exit in the submission of this manuscript, and this manuscript is approved by all authors for publication. I would like to declare on behalf of my co-authors that the work described was original research that has not been published previously, and not under consideration for other publications elsewhere., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn), grain sizes, and concentrations of organic carbon (Corg) were measured in 323 river sediment samples from the Pearl River Delta (PRD). Results showed that the heavy metal concentrations in the sediments ranged from 1.6-93 mg/kg for As, 0.04-9.3 mg/kg for Cd, 2-315 mg/kg for Cr, 1.1-352 mg/kg for Cu, 0.01-0.67 mg/kg for Hg, 11-221 mg/kg for Pb, and 11-1234 mg/kg for Zn. The highest values of As, Cr, Cu, Hg, Pb, and Zn appeared in the Beijiang River, whereas Cd was high in the Xijiang River. The overall sediment quality in the area with respect to metal concentrations generally met the primary standard criteria of China (Marine Sediment Quality), except for Cd and Cu. The spatial distributions of the heavy metals were influenced by both grain sizes and Corg concentrations. The Igeo geo-accumulation index indicated that there was no significant Cr, Cu, Hg, or Zn pollution, slight to moderate pollution by As and Pb, and moderate Cd pollution in the study area. Spatial distributions of an eco-toxicological index based on probable effect levels indicated that there was a 21% probability that the combination of the seven metals was exerting a toxic stress in the PRD river sediments., (Copyright © 2018 Elsevier Ltd. All rights reserved.)