Yellow River Delta National Nature Research Articles

Significant negative impact of human activities on carbon storage in the Yellow River Delta over the past three decades

With the increasing intensification of human activities, significant changes in land use and land cover (LULC) have posed a severe threat to the carbon storage capacity of wetland ecosystems. A deep understanding of this impact is crucial for protecting regional ecosystems and promoting sustainable development. This study utilized the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model and the human activity intensity (HAI) index to conduct detailed grid analysis and global analysis of carbon storage through creating fishnet system and explored the complex relationship between carbon storage and HAI in the Yellow River Delta (YRD), China. The results indicated that over the past 30 years, natural wetlands such as meadow wetlands and salt marshes in the study area had undergone significant degradation due to escalating human activities, while artificial wetlands and non-wetland areas expanded. Concurrently, the total regional carbon storage had declined by 2.08 Tg, representing a significant drop of 8.22 % in the YRD from 1990 to 2020. Among them, dry land, as the primary land type, served as the most crucial carbon pool. Additionally, the human activity intensity of land surface (HAILS) increased significantly, with a growth rate of 37.27 %. HAI mapping revealed a continuous expansion of areas with high HAI. In contrast, the Yellow River Delta National Nature Reserve (YRDNNR) maintained relatively low HAI. Correlation analysis further showed the significant negative correlation (p < 0.01) between carbon storage and HAI, with r values of grid analysis ranging from −0.1395 to −0.0344, while that for global analysis was −0.9643, respectively. This reflected the spatial heterogeneity and agglomeration effects of data analysis across different scales. This study provides valuable insights for achieving the “dual carbon” goals and supporting the conservation and management of wetland ecosystems.

Tracking annual dynamics of carbon storage of salt marsh plants in the Yellow River Delta national nature reserve of china based on sentinel-2 imagery during 2017–2022

Coastal salt marshes play a key role in coastal carbon sequestration. Understanding the spatial distribution and annual changes of carbon storage of salt marsh plants at a local scale is helpful for accurate protection and restoration. However, the annual carbon storage of salt marsh plants has not yet been obtained in the Yellow River Delta National Nature Reserve (YRDNNR), China. Here, we developed a fast and reliable method to produce an annual map of carbon storage of herbaceous salt marsh plants from 2017 to 2022 based on multi-year in situ data and 10-meter resolution Sentinel-2 images in YRDNNR. That is, a deep belief network based on conjugate gradient (CGDBN) pixel-level classification, a generative adversarial network with a constrained factor (GAN-CF) measured sample expansion and multiple linear regression (MLR) quantitative inversion algorithm is used. The results showed that: (1) The carbon storage of herbaceous salt marsh plants in the YRDNNR increased in 2017–2018 and 2019–2021, with an average carbon storage dynamic of 4.53–8.39 Mg/ha. (2) In 2021, the area of salt marsh vegetation increased significantly by 20 % compared to 2017. Although its area decreased sharply due to the removal of invasive species (S. alterniflora) in 2022, the carbon storage per unit area of salt marsh plants remained at 7.77 Mg/ha. (3) The carbon storage of salt marsh vegetation showed a gradient change along the community succession from land to sea. Estimating annual carbon storage of salt marsh plants could provide basic data for recognizing the ‘blue carbon’ contribution of coastal plants and managing the coastal salt marsh ecosystem in Yellow River Delta.

Soil Nutrient Distribution and Preferential Flow Transport Patterns in Robinia Pseudoacacia Communities of Degraded Wetlands

The Yellow River Delta wetlands in the Yellow River Delta National Nature Reserve are facing serious degradation due to water scarcity and soil salinization. This study aims to investigate the mechanism of wetland degradation by analyzing the small-scale distribution of soil nutrients and preferential flow transport patterns in the Robinia Pseudoacacia community, which is a typical vegetation community in degraded wetlands. Soil physical and chemical properties based on field staining experiments were analyzed, and indoor solute penetration experiments were conducted to investigate the distribution of soil nutrients and hydrological characteristics. The results showed that the contents of soil organic carbon, organic matter, total nitrogen, and available phosphorus decreased with increasing soil depth, with higher contents in the preferential flow area than in the matrix flow area. Soil organic carbon, organic matter, total nitrogen, total phosphorus, and available phosphorus showed positive correlations with each other, while soil pH and conductivity exhibited negative correlations with the above nutrients. The efflux rate of the Acacia community exhibited a gradual decline as soil depth increased, and the relative concentration of the solution exhibited a non-monotonic pattern of decrease, increase, and subsequent decrease with increasing soil depth. The findings could provide valuable guidance for the restoration and management of degraded wetlands in the Yellow River Delta.

Land-Use Change, Habitat Connectivity, and Conservation Gaps: A Case Study of Shorebird Species in the Yellow River Delta of China Using the InVEST Model and Network Analysis

Coastal wetlands form a transition zone between terrestrial and marine environments and provide important ecosystem services. Land-use change in the coastal zone has a substantial effect on habitat connectivity and biodiversity. However, few studies have characterized the effects of land-use change on coastal habitat connectivity. We conducted remote sensing analysis, modeling with the Integrated Valuation of Ecosystem Services and Trade-offs model, geospatial analysis, and habitat connectivity analysis to evaluate historical spatiotemporal changes in the habitat quality and habitat connectivity of migratory shorebirds in the Yellow River Delta, which is an important stopover site along the East Asian–Australasian Flyway migratory route. Several high- and medium-quality areas have been converted to industrial mining and mariculture sites because of land reclamation. The probability of connectivity decreased by −66.7% between 1975 and 2020. Approximately 71.0%, 11.6%, and 5.8% of patches with high importance have been converted to non-habitat patches, habitat patches with medium importance, and habitat patches with low importance, respectively; approximately 58.9% and 11.7% of the patches with medium importance have been converted to non-habitat patches and habitat patches with low importance, respectively. The total priority conservation area was 389.4 km2, and 125.0 km2 (32.1%) of this area remains unprotected; these unprotected areas are mainly distributed in the northwestern and eastern parts of the Yellow River Delta. We recommend that the boundary of the Yellow River Delta National Nature Reserve be expanded to incorporate these unprotected areas.

A new method for quantifying the value of ecological environment damage caused by illegal fishing: A case study

Illegal fishing may trigger structural disruption of the food chain and even damage the entire marine ecosystem. This paper proposes a new method for quantifying the value of eco-environment damage caused by illegal fishing; as an example, we used an illegal fishing case of anchovies in the vicinity of the Yellow River Delta National Nature Reserve. Based on the data from the field investigation and literature, we estimated the number and age distribution of illegally harvested anchovies. Additionally, the potential number of the offspring was calculated according to the potential number and survival rate of anchovy eggs. Due to the unavailability of commercial anchovy fries, “alternative stock enhancement” was recommended to restore the damaged eco-environment. Notably, the alternative species should have similar economic value, status in the food chain, and living areas to anchovies. Eventually, we selected Liza haematocheilus as the alternative species and calculated the total eco-environment recovery cost.

Disentangling the relative influence of regeneration processes on marsh plant assembly with a stage-structured plant assembly model

In salt marshes, abiotic factors, interspecific competition or facilitation, and herbivory have been discussed extensively as important drivers of marsh plant distribution patterns. However, the relative importance of various regeneration processes across stress gradients received little attention, despite their importance in explaining plant community dynamics. In this study, we built a stage-structured plant assembly model to study how the influence of each regeneration process on plant assembly dynamics varies with environmental stress level, plant succession stage and initial seed availability, in a salt marsh in Yellow River Delta National Nature Reserve in China. We found plant assembly at higher saline conditions is mainly governed by stress tolerance regardless of the stage of succession and initial seed availability, as salinity stress can suppress biomass accumulation and propagule production of salt intolerant species. Under less saline conditions with high seed availability, juvenile competition plays the most important role throughout succession. When initial seed availability is low, dispersal is more important at the beginning, but juvenile competition is more important at later stage and determines the plant competition outcomes. Our findings imply seed availability is important in determining plant succession trajectories under less stressful conditions, and should be given more attention during restoration management in coastal marshes.

A prioritization metric and modelling framework for fragmented saltmarsh patches restoration

Saltmarsh is a coastal ecosystem providing crucial ecosystem services, and its continued degradation and fragmentation has drawn increasing attention. However, how to effectively restore the connectivity between fragmented saltmarsh patches remains an open challenge. In this study, we developed a metric and modelling framework that prioritised saltmarsh patches for restoration. To demonstrate our approach, we simulated spatially explicit restoration schedules for Suaeda salsa patches at the Yellow River Delta National Nature Reserve, China, using three strategies: increasing-patch-area, increasing-number-of-patches and a benchmark unrestrictive prioritization strategy. We prioritised patches for restoration based on a number of widely used graph-theoretic landscape connectivity and metapopulation capacity metrics. Our simulation results suggested the rank connectivity-importance of extant patches was correlated within the group of graph-theoretic connectivity metrics or metapopulation capacity metrics, but unrelated across group. The unrestrictive prioritization strategy clearly outperformed the strategies of increasing-patch-area and increasing-number-of-patches which returned comparable connectivity restoration outcomes. For the more effective unrestrictive prioritization strategy, there were substantial differences in the simulated priority patches between metrics that considered stepping stone effects and those did not. While the former resulted in corridor-building priority patches that led to a more connected landscape throughout the region, the latter led to local clustering. We recommend use of the total probability of connectivity (PC) among the metrics we tested due to similarity of results to other metrics and its simulation efficiency. The proposed framework is readily applicable to prioritise areas for connectivity conservation and restoration in any monospecific ecosystem at the regional scale.

Habitat changes in the most important stopover sites for the endangered red-crowned crane in China: a large-scale study.

The red-crowned crane (Grus japonensis) is an endangered bird species that has been listed as one of the Class I National Key Protected Wild Animals of China. This study analyzed the habitat changes in the two most important stopover sites for red-crowned crane (Liao River Estuary and Yellow River Delta National Nature Reserves) from 2000 to 2015. The results showed that the landscape patterns of the important stopover sites of red-crowned crane changed obviously and the potential suitable habitat area (tidal flats and marshland) for the red-crowned crane decreased by 183.3 km2, while the area of human activities (including aquaculture waterbodies, farmland and artificial facilities) increased by 140.3 km2. Landscape fragmentation intensified, which could has negative impacts on the survival of the red-crowned crane during migration. A comparative study confirmed that the reduction in marshlands and increasing landscape fragmentation caused by human activities were the main threats in the Liao River Estuary National Nature Reserve, while human activities and natural factors (such as channel flow, rainfall, and sediment discharge) were the jointly driving factors for the reduction in suitable habitats for red-crowned cranes in the Yellow River Delta National Nature Reserve. We suggest there are some loopholes in the management of the two nature reserves, which need to be strengthened urgently in China.

Wetland Ecosystem Service Dynamics in the Yellow River Estuary under Natural and Anthropogenic Stress in the Past 35 Years

Assessing long-term dynamics of ecosystem service is critical for sustainable restoration and management of estuarine wetlands. We analyzed ecosystem services dynamics from 1980 to 2015 and their natural and anthropogenic drivers in the Yellow River Delta National Nature Reserve, which consists of the old and current Yellow River estuaries. Our results showed that biodiversity conservation, carbon storage, and water purification services in the old Yellow River estuary were improved gradually, but water yield decreased during the study period. Ecosystem services in the current Yellow River estuary changed sharply during 1980–1990, but fluctuated since 1990. The warming climate in the past 35 years negatively affected water yield and enhanced carbon storage in the old Yellow River estuary. Marshland was critical for improving ecosystem services in the old Yellow River estuary, and medium cover grassland provided suitable habitats for water birds in the current Yellow River estuary. Furthermore, the release of freshwater from the Yellow River into estuarine wetlands enhanced the provision of ecosystem services. In comparison with biodiversity conservation, water purification, and carbon storage services, water supply service responded differently to ecological restoration. Better tradeoffs should be identified to ensure effective provision of desired ecosystem services during ecological restoration.

Hydrological connectivity dynamics and conservation priorities for surface-water patches in the Yellow River Delta National Nature Reserve, China

Hydrological connectivity is important for the long-term persistence of water-dependent organism inhabiting floodplain and coastal wetlands, as surface-water patches not only create temporary habitats for them, but also provide dispersal opportunities. Improving understanding of how hydrological connectivity varies with respect to surface-water dynamics is an important step to maintain biodiversity in dynamic coastal environments. Using a series of available remote sensing images, we extracted surface-water patches across a 12-year (2006–2017) and assessed the corresponding hydrological connectivity using the landscape connectivity metrics. Furthermore, we identified important surface-water patches serve as connectivity providers in surface-water networks. Particularly, the threshold distance, needed for analysis of hydrological connectivity, was determined by “Distance- Landscape Connectivity Metrics” curves. We focused on China's Yellow River Delta (YRD), a globally significant floodplain and coastal wetland. Results showed that hydrological connectivity, fluctuating in a range of 0.0726 to 0.0908 during 2006-2017, varied with the number and spatial distribution of water patches. Our study highlight that water patches in Dawenliu Restoration (DR) could serve as ideal high-priority targets for specific management aimed at maintaining or improving hydrological connectivity. We also found that the suitable threshold distance for analyzing hydrological connectivity of the Yellow River Delta National Natural Reserve (YRDNR) is 500 m.

Nest site selection and its implications for conservation of the endangered Oriental Stork Ciconia boyciana in Yellow River Delta, China

SummaryAvian nest site selection is crucial to breeding birds especially for large endangered waterbirds. We investigated the population dynamics, nests and breeding habitat selection, offspring numbers and reproductive success rate of Oriental Stork Ciconia boyciana from February to June 2017 in Yellow River Delta National Nature Reserve (YRD NNR), Shandong, China. We measured the characteristic variables of 32 control plots by random selection and 62 nest plots, including 40 nests on power poles, 14 nests on artificial poles and eight nests on pylon poles. We used conditional logistic regression and model-averaging to quantify data and model characteristic variables affecting nest site selection. Our results showed that human disturbance was the main negative factor affecting Oriental Stork’s selection of power pole nests. Meanwhile, distance from highways was the most important variable for the selection of artificial nests. Distance from sightseeing sites was the main explanatory variable that contributed to the selection of pylon nests. Based on our findings, we recommend promoting conservation of this species by reducing human disturbance, such as forbidding use of car horns in nest site areas and providing enough suitable nest sites.

Water accessibility assessment of freshwater wetlands in the Yellow River Delta National Nature Reserve, China

Water accessibility assessment (WAA) is very important to the ecological restoration of freshwater wetlands and water resources management due to an intensive human disturbance. This paper develops a quantitative methodology for WAA in the Yellow River Delta National Nature Reserve (YRDNNR), from which an assessment of water accessibility is made on the freshwater wetlands. The assessment uses a Water accessibility index (WAI) model by employing GIS network analysis and spatial statistical analysis. Five indicators for the model cover both natural and anthropogenic factors, including distance from freshwater resources, average elevation, road density, ditch density, and number of culverts at the grid scale. The values of the WAI model are between 0.26 and 0.82. The WAI has a significant and positive spatial autocorrelation. There are totally 12 freshwater marsh patches exist in the YRDNNR. The highest WAI value in the freshwater marsh patch occurs near the estuary area of the Yellow River, while the lowest WAI value lies farthest from the Yellow River. There are two freshwater restored wetlands that have lower WAI values, from which a scientific restoration strategy is presented to remove the paddy field, roads and other facilities between two wetlands and the Yellow River Course. The results of the WAI model have been validated by matching the ratio of water body area within patches and consulting with local administrators, which indicates a satisfied WAI assessment effectiveness. The proposed WAI can help administrators to guide wetland ecological restoration and to plan for freshwater resources management.

Modeling and evaluating land-use/land-cover change for urban planning and sustainability: A case study of Dongying city, China

This study analyzed the land-use/land-cover change (LUCC) of Dongying city and the corresponding variation in ecosystem services. Dongying city was chosen as the study area for its typicality. Dongying city owns the Yellow River delta national nature reserve that has rich animal and plant resources and is also the core city of the Yellow River Delta High-efficient Eco-Economic Zone (YRDHEZ). The local government is subjected to considerable stress during urbanization because of the need to consider ecosystem protection and economic development at the same time. It is necessary to study the LUCC caused by urbanization and to quantify the damage caused to ecosystem services, which may provide useful scientific references for policy making and a sustainable development method. In this study, we investigated LUCC during 1995–2015 and generated LUCC maps for 1995, 2004 and 2015. The areas of grassland, farmland, water and bare land were reduced by 21.43%, 38.72%, 7.36% and 22.54%, respectively, while the area of built-up land was increased by 347.34%. In addition, a simulation LUCC map for 2025 was also obtained. The result indicated that the area of built-up land will continue to increase in 2025. Landscape metrics at a class level were calculated to quantify land-use changes with the help of FRAGSTATS 4.2 software. The result showed a sharp increase in built-up land in Dongying city. We also calculated the ecosystem service values (ESVs) according to the LUCC maps of 1995, 2004, 2015 and 2025. A continuous decrease in ESVs between 1995 and 2025 was found. The results revealed that land use of Dongying city changed dramatically according to urbanization. As other types of landscape changed into built-up land during rapid urbanization, LUCC strongly affected ecosystem services.

Maintenance of salt barrens inhibited landward invasion ofSpartinaspecies in salt marshes

AbstractSpartinaspp. (cordgrasses) often dominates intertidal mudflats and/or low marshes. The landward invasion of these species was typically thought to be restrained by low tidal inundation frequencies and interspecific competition. We noticed that the reported soil salinity levels in some salt marshes were much higher than those at the mean higher high water level, which might inhibit the landward invasion of cordgrass. To test this possibility, we transplantedSpartina alternifloraacross an elevational gradient in an invaded salt marsh in the Yellow River Delta National Nature Reserve, where a salt accumulation zone (i.e., salt barren) was previously observed. We found thatS. alterniflorawas significantly inhibited by the salt barren in high marsh regions, although it performed better at upland and low marsh regions. A common garden experiment further elucidated thatS. alternifloraperformed best at low salinity levels and that this species is less sensitive to inundation frequency. Our results indicated that the salt barren inhibited the landward invasion ofS. alterniflorain salt marshes and provided a natural barrier to protect the upland from invasion. Though field observations suggest thatS. alternifloracould propagate along tidal channels, which provide low‐salinity corridors for the dispersal of propagules, natural salt barrens can inhibit the landward invasion ofSpartinain salt marshes. However, artificial disturbances that break the salt barren band in salt marshes (e.g., artificial ditches) might accelerate the invasion ofSpartinaspp. This new finding should alert salt marsh managers to pay attention to artificial ditches and/or other human activities when attempting to controlSpartinainvasion.

Geochemical speciation and ecological risk assessment of heavy metals in surface soils collected from the Yellow River Delta National Nature Reserve, China

ABSTRACTIn this study, a comprehensive assessment of soil heavy metal (HMs) pollution in the Yellow River Delta National Nature Reserve (YRDNNR) was conducted. Spatial distributions, chemical fractions, and sources of eight HMs (Cu, Zn, Pb, Cr, Cd, Fe, Mn, and Ni) in 46 soil samples in the studied region were analyzed. In addition, the potential risks of the HMs were evaluated. The results showed that the mean concentrations of Cu, Zn, Pb, Cr, Cd, Fe, Mn, and Ni were 19.4, 65.2, 38.4, 55.9, 0.078, 41546.5, 510.3, and 27.5 mg kg−1, respectively. It indicates that the concentrations of most HMs, with exception of Pb and Fe, in samples were similar to the background value of soil in China. Principal component analysis results showed that the HMs originated mainly from natural sources, but Pb pollution in the studied area was significantly caused by anthropogenic activities. In addition, Ecological risk assessment statistical analysis indicates that the HM contamination level in YRDNNR ranged from low to moderately polluted, however, the environmental risk due to Mn and Pb contamination was high.

High genetic diversity and absence of phylogeographic structure in breeding populations of vulnerable Saundersilarus saundersi (Charadriiformes: Laridae) in Bohai Bay, China

Genetic diversity is an important consideration in developing effective conservation strategies for threatened species. The Saunders’s Gull (Saundersilarus saundersi) is a globally vulnerable species, which breeds in coastal wetlands in eastern China and western South Korea. Approximately 85% of the world population breeds at three sites along Bohai Bay in eastern China: Nanxiaohe in Liaohekou National Nature Reserve of Liaoning Province, and Yiqianer and Dawenliu in Yellow River Delta National Nature Reserve of Shandong Province. We examined mitochondrial and nuclear markers to detect genetic diversity and phylogeographic structure of the three Bohai Bay subpopulations. Unexpectedly high genetic diversity was observed in both mitochondrial and nuclear markers for every subpopulation. There was no evidence of phylogeographic structure among the three breeding subpopulations, indicating high levels of gene flow in the recent past, possibly continuing into the present day. These results reveal high levels of genetic diversity and evolutionary potential among the current populations of S. saundersi in Bohai Bay. If timely conservation measures are implemented, this gull species would has excellent prospects for long-term survival.

Sources apportionment of PM2.5 in a background site in the North China Plain

To better understand the sources and potential source regions of PM2.5, a field study was conducted from January 2011 to November 2011 at a background site, the Yellow River Delta National Nature Reserve (YRDNNR) in the North China Plain. Positive matrix factorisation (PMF) analysis and a potential source contribution function (PSCF) model were used to assess the data, which showed that YRDNNR experienced serious air pollution. Concentrations of PM2.5 at YRDNNR were 71.2, 92.7, 97.1 and 62.5μgm−3 in spring, summer, autumn and winter, respectively, with 66.0% of the daily samples exhibiting higher concentrations of PM2.5 than the national air quality standard. PM2.5 mass closure showed remarkable seasonal variations. Sulphate, nitrate and ammonium were the dominant fractions of PM2.5 in summer (58.0%), whereas PM2.5 was characterized by a high load of organic aerosols (40.2%) in winter. PMF analysis indicated that secondary sulphate and nitrate (54.3%), biomass burning (15.8%), industry (10.7%), crustal matter (8.3%), vehicles (5.2%) and copper smelting (4.9%) were important sources of PM2.5 at YRDNNR on an annual average. The source of secondary sulphate and nitrate was probably industrial coal combustion. PSCF analysis indicated a significant regional impact on PM2.5 at YRDNNR all year round. Local emission may be non-negligible at YRDNNR in summer. The results of the present study provide a scientific basis for the development of PM2.5 control strategies on a regional scale.

Reed Parrotbill nest predation by tidal mudflat crabs: Evidence for an ecological trap?

Understanding the relationships between nesting habitat quality and predation risk is essential for developing appropriate conservation management for threatened species. This is particularly relevant where anthropogenic pressures could decouple the environmental cues used by birds to assess nesting habitat quality from increased predation risk. In this study, we conducted a series of surveys and nest experiments to examine the nest predation rates of Reed Parrotbill (Paradoxornis heudei) a passerine bird between inland and tidal reed‐bed wetland habitats, at Yellow River Delta National Nature Reserve, Eastern China during 2008, and 2010–2012. We found significant differences in the habitat structural characteristics between the two adjacent wetland habitats that are critical for Reed Parrotbill nest‐site selection. Experimental trials using recently constructed and abandoned Reed Parrotbill nests as ‘artificial nests, quail eggs and predator‐exclusion measures, revealed that tidal mudflat crab (Helice tientsinensis) was the primary cause of Reed Parrotbill egg predation in tidal reed‐bed habitat. Annual predation rates of real nests from inland reed‐bed habitat varied from 35% to 68%, and predation rates of artificial nests were much lower than those from real nests. Pitfall sampling revealed that the abundance of tidal mudflat crabs was significantly higher in tidal reed‐bed habitat. Our data suggested that Reed Parrotbills breeding in tidal reed‐bed habitats may be highly vulnerable due to extremely high rates of nest predation (up to 100%), caused primarily by the high density of tidal mudflat crabs. The incongruence between nest‐site habitat preference and nest survival indicated an ecological trap scenario, which requires further studies on its proximate and ultimate causes as well as the development of effective conservation management for the Reed Parrotbill.

Airborne particulate polycyclic aromatic hydrocarbon (PAH) pollution in a background site in the North China Plain: Concentration, size distribution, toxicity and sources

The size-fractionated characteristics of particulate polycyclic aromatic hydrocarbons (PAHs) were studied from January 2011 to October 2011 using a Micro-orifice Uniform Deposit Impactor (MOUDI) at the Yellow River Delta National Nature Reserve (YRDNNR), a background site located in the North China Plain. The average annual concentration of total PAHs in the YRDNNR (18.95±16.51ng/m3) was lower than that in the urban areas of China; however, it was much higher than that in other rural or remote sites in developed countries. The dominant PAHs, which were found in each season, were fluorene (5.93%–26.80%), phenanthrene (8.17%–26.52%), fluoranthene (15.23%–27.12%) and pyrene (9.23%–16.31%). A bimodal distribution was found for 3-ring PAHs with peaks at approximately 1.0–1.8μm and 3.2–5.6μm; however, 4–6 ring PAHs followed a nearly unimodal distribution, with the highest peak in the 1.0–1.8μm range. The mass median diameter (MMD) values for the total PAHs averaged 1.404, 1.467, 1.218 and 0.931μm in spring, summer, autumn and winter, respectively. The toxicity analysis indicated that the carcinogenic potency of particulate PAHs existed primarily in the <1.8μm size range. Diagnostic ratios and PCA analysis indicated that the PAHs in aerosol particles were mainly derived from coal combustion. In addition, back-trajectory calculations demonstrated that atmospheric PAHs were produced primarily by local anthropogenic sources.

Sources and distribution of aliphatic and polycyclic aromatic hydrocarbons in Yellow River Delta Nature Reserve, China

Sediment samples collected from the Core Area, Experimental Area and Buffer Area of Yellow River Delta National Nature Reserve (YRDNNR), China, were analyzed by GC-MS in order to determine the degree of hydrocarbon contamination, and identify the sources of aliphatic hydrocarbons and PAHs. The total petroleum hydrocarbon contents of sediments were relatively low or moderate compared to world-wide locations reported to be chronically contaminated by oil. On the whole, the degree of petroleum contamination in the Core Area and Buffer Area in YRDNNR is weaker than that of the Experimental Area. The potential ecosystem risk assessment indicated that PAHs will not cause immediate adverse biological effects in the YRDNNR. Besides oil-related hydrocarbon inputs in this region, aliphatic hydrocarbon analysis showed the presence of hydrocarbons of terrestrial origin at some sampling sites, characterized by high CPI values. Based on PAH ratios and principal component analysis, pyrolytic input may be a major source of PAHs in YRDNNR sediment, while petrogenic inputs were more apparent at some sites in the Experimental Area due to oil exploration in the Shengli Oilfield. (C) 2011 Elsevier Ltd. All rights reserved.