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In this study, the sedimentary records, sources, and ecological risks of polycyclic aromatic hydrocarbons (PAHs) in Dianchi Lake were analyzed. The concentrations of ΣPAH16 in the sediments of Dianchi Lake ranged from 368 to 990 ng/g, with an average value of 572 ng/g, peaking in 1988. Economic development, rapid population growth, and rapid growth of coal consumption have a greater impact on the HMW (high molecular weight) PAHs than on the LMW (low molecular weight) PAHs in the sedimentary environment. The results of the diagnostic ratios and PCA (principal component analysis) model show that the main sources of PAHs were coal and biomass combustion, as well as the fossil fuel combustion in individual years. The risk assessment results showed that the PAH concentrations in the sediment were within a safe range. In the past 100 years of sediment pore water, other 2–3 ring LMW PAHs were within a safe range (except for Phe, which reached chronic toxic pollution levels in some years). With an increase in industrialization and urbanization, the burning of fossil fuels such as coal and petroleum has increased, and some of the 4–6 ring HMW PAHs have reached chronic toxicity or even acute toxicity in the sediment pore water. [ABSTRACT FROM AUTHOR]

An analysis of the correlation between polycyclic aromatic hydrocarbons (PAHs) and economic parameters demonstrates that the total population, gross domestic product, coal consumption, petroleum, temperature, and day consumption significantly affect PAH concentrations in Dianchi Lake, Yunnan province, China. An artificial neural network (ANN) model was developed to predict the trend in PAH concentrations in the sediments of Dianchi Lake over the next 10 years based on current indicators of economic development. The ANN model estimated the concentration of PAHs from 1980 to 2014. The model was evaluated using available observations for the historical trends; concentrations of PAHs in the sediments of Dianchi Lake are calculated to be at 2128.1 ng/g in 2025 and are expected to decline up to 1044.3 ng/g by 2030. These concentrations are considered relatively high because of their impacts on the health of people and aquatic organisms and the development of surrounding industries. We show the importance of the socioeconomic and climate factors in increasing the pollution levels. Our results could support the local government to formulate effective measures to reduce the pollution levels in the lake. [ABSTRACT FROM AUTHOR]

Highlights • Critical factors of SWAT were represented digitally and dynamically. • Lake sediment Phosphorus can be designated as an ideal indicative indicator for the watershed non-point source pollution. • Relationship between watershed and sediment P varied apparently among different basins, sediment depths and P states. Abstract An understanding of the quantitative relationship between watershed non-point source (NPS) pollution and lake nutrient enrichment is essential for the environmental management of water bodies. However, a lack of data availability and integration limit our understanding of this relationship. The most critical bottlenecks are the lack of adequate support for watershed-lake integrated data, a lack of data of the nutrient loading from watersheds into a lake as NPS, and the long-term time series data of lake nutrient concentrations. Since lake sediment is the ultimate destination of watershed nutrients, this study aimed to reveal the relationship between watershed phosphorus (P) concentrations that are transported into lakes and lake P concentrations by using inlet sediments as an indicator. Three typical sub-basins within Hongze Lake, China were selected as the study site, and 30-year dataset was calculated using the technology integration of remote sensing, sediment chemical analysis and SWAT model assessment. It can be concluded that, first, the Mineral-P (Min-P) accounted for nearly 65% of the watershed Total P (TP) loss, which varied over different basins and temporal periods. Second, the relationship between watershed P loss into lakes and sediment P concentrations represented obvious variation among different basins, sediment depths and P states. With respect to different basins, the highest correlation appeared in Basin 1, which had a R2 value of 0.65 for Min-P. With respect to different P states, the Inorganic-P (IP) showed a closer relationship between watershed and lake P than Organic-P (OP), and the correlation coefficient (r) was higher than 0.6 in Basin 1 and Basin 3 for IP. In addition, the calcium-phosphorus ratio (Ca-P), which is largely sourced from watershed rock detritus by eroded runoff, played the most critical role among different Min-P states in the relatively ideal relationship of IP. With respect to different sediment depths, a stratification phenomenon existed in Basin 2 and Basin 3, which differed at specific depths. In particular, the ideal relationship only existed within the 7 cm depth from the bottom in basin 2, and this value expands to 10 cm for basin 3. This diversity was influenced by the integration roles from external and endogenous sources. All the findings indicated that lake surface sediment can be used as a proxy to represent NPS P loading under specific conditions. The relationship between watershed P loss and lake sediment P concentration was largely decided by land use/cover change (LUCC), meteorological conditions, and lake resuspension. [ABSTRACT FROM AUTHOR]

Sediment resuspension is closely related to the endogenetic release of nutrients in Lake Taihu. Thus, understanding the factors associated with sediment resuspension is important. In this study, a new technology, which integrates a hydrodynamic model and remote sensing techniques, was applied to derive the distribution of the erosion flux and obtain the spatially variable critical shear stress. Then, the spatially variable critical shear stress was used in the sediment simulations at Lake Taihu. Compared to the traditional model, based on uniform values of critical shear stress, the new method, using variable values of critical shear stress calibrated from the Geostationary Ocean Color Imager (GOCI) data, significantly improved the sediment simulations at Lake Taihu. Based on the erosion flux from August 6-8, 2013, the correlations between erosion and wind speed, wind fetch, mud depth, and water depth were analyzed for different subsections and spots in Lake Taihu. The potential sources of error were also addressed. Further improvement of the model is necessary. [ABSTRACT FROM AUTHOR]

Sediments have a significant influence on the cycling of nutrient elements in lake environments. In order to assess the distribution characteristics and estimate the bioavailability of phosphorus and nitrogen in Dianchi Lake, organic and inorganic phosphorus and nitrogen forms were analysed. The 210Pb radiometric dating method was employed to study temporal changes in the phosphorus and nitrogen pools in Dianchi Lake. The result show that the total phosphorus (TP) and total nitrogen (TN) were both at high concentrations, ranging from 697.5-3210.0 mg/kg and 1263.7-7155.2 mg/kg, respectively. Inorganic phosphorus (IP) and total organic nitrogen (TON) were the main constituents, at percentages of 59%-78% and 74%-95%, respectively, in the sediments. Spatially, there was a decreasing trend in phosphorus and nitrogen contents from the south and north to the lake centre, which is related to the distribution pattern of local economic production. The burial rates of the various phosphorus and nitrogen forms increased in same spatially and over time. Particularly in the past two decades, the burial rates doubled, with that TN reached to 1.287 mg/(cm2·yr) in 2014. As the most reactive forms, nitrate nitrogen (NO3-N) and ammonia nitrogen (NH4-N) were buried more rapidly in the south region, implying that the potential for releasing sedimentary nitrogen increased from north to south. Based on their concentrations and burial rates, the internal loads of phosphorus and nitrogen were analysed for the last century. A TP pool of 71 597.6 t and a TN pool of 81 191.7 t were estimated for Dianchi Lake. Bioavailable phosphorus and nitrogen pools were also estimated at 44 468.0 t and 5429.7 t, respectively, for the last century. [ABSTRACT FROM AUTHOR]

Increased organic carbon and nitrogen accumulation rates (OCAR and ONAR) in lake sediment significantly regulate the global carbon cycle. However, the reasons for and contributors to the increased OCAR and ONAR are unclear. Seven sediment cores, collected in July 2014 from Dianchi Lake, China, were used to evaluate the effects of autochthonous and allochthonous sources on OCAR and ONAR. The results indicate that OCAR and ONAR increased by factors of 4.33 and 7.34 over the past hundred years (1900–2000), particularly after algal blooms began to occur frequently (beginning in the 1980s). Dianchi stored 0.467 ± 0.0055 Tg (mean value ± standard deviation) organic carbon (OC) and 0.033 ± 0.0004 Tg organic nitrogen (ON) after 1986, which is almost equal to the total storage of OC and ON from 1900 to 1985 (OC, 0.468 ± 0.0022 Tg; ON, 0.032 ± 0.0002 Tg). OCAR and ONAR increases were due to increasing autochthonous production and allochthonous loading. Examination of the increased OCAR, which was estimated from a newly developed multi-source mixing model, suggests that > 90% of increased OCAR was caused by allochthonous sources (such as intensified cultivation, land-use cover change, etc.) in southern and eastern Dianchi and that > 70% of the increased OCAR was due to autochthonous sources in western and northern Dianchi Lake. The significant spatial and temporal variation in the contributors to increased OCAR indicates complicated migration and transformation of OC in inland lakes. Land use cover change around Dianchi and the occurrence of algal blooms regulate the contributions of allochthonous and autochthonous sources to the increased OC and ON. [ABSTRACT FROM AUTHOR]

Surface sediments and sediment core had been collected from Erhai Lake, Southwest China to study the concentrations, toxicity risks, and sources of polycyclic aromatic hydrocarbons (PAHs). The average concentrations of Σ 16 PAHs, seven carcinogenic PAHs (carPAHs), and carcinogenic toxic equivalents (TEQcar) in the surface sediments and sediment core were 1634.50 ± 488.56 ng g−1 and 436.72 ± 128.17 ng g−1, 67.18–293.65 ng g−1 and 91.07–265.90 ng g−1, and 34.89 ± 13.17 ng g−1 and 36.99 ± 7.52 ng g−1, respectively. The Σ 16 PAHs and carPAHs concentrations in surface sediments were higher in the southern lake. The Σ 16 PAHs and TEQcar in the sediment core peaked in the 2010s and 1980s. The spatiotemporal variations in TEQcar and carPAHs were similar. Positive matrix factorization revealed that traffic emissions contributed 35.71 % of the TEQcar, whereas coal and biomass combustion contributed 12.89 % in the surface sediments. The contribution of gasoline and fossil fuel to TEQcar significantly increased from 19.2 % (1890s) to 66.5 % (1990s), that of benz[ a ]pyrene (coal combustion) decreased, and those of benz[ b ]fluoranthene and indeno[1,2,3- cd ]pyrene (petroleum combustion and traffic emissions) increased from 1.92 % to 3.93 % and from 1.54 % to 2.52 % in the sediment cores, respectively, owing to changes in energy consumption. • Spatio-temporal distributions of Σ 16 PAHs, carPAHs, and TEQ in Erhai Lake sediments were investigated. • Sources of PAHs concentrations and TEQcar were quantitatively apportioned via the PMF model. • TEQ BaP and TEQ DbahA increased over last four decades but decreased in recent years. • Energy consumption, especially fossil fuel combustion, greatly contributed TEQ. [ABSTRACT FROM AUTHOR]

Abstract: Human activities contribute highly to water eutrophication. In this study, the relationship between human activities and water eutrophication in Dianchi Lake in China was characterized using a combination of satellite imaging, sedimentary physicochemical and meteorological data analyses. The heavy eutrophic status and algal bloom in Dianchi Lake were first observed by satellite in 1977 and 1989, respectively. The C/N ratio, an indicator of organic sources in sediments, also showed that the planktonic organic source in the sediment significantly increased beginning in 1989. The land use cover in the Dianchi basin showed that both farm lands and forests, but particularly farmlands, were reduced during the period from 1974 to 2009. The urbanized land area increased from 1974 to 2009, particularly after 2000. The effects of human activities on water eutrophication were expressed by land use cover, population, gross domestic product (GDP; separated into primary, secondary and tertiary industries) and wastewater discharge. For land use cover, farm and urbanized lands were the main sources of water nutrients; forest contributed slightly to these nutrients. For GDP, primary (correlation coefficient=0.94, P<0.001) and tertiary (correlation coefficient=0.95, P<0.001) industries were highly correlated with total nitrogen. Secondary (correlation coefficient=0.95, P<0.001) and tertiary (correlation coefficient=0.96, P<0.001) industries were highly correlated with total phosphorus. The algal bloom area was significantly correlated with wastewater discharge (correlation coefficient=0.78, P<0.005) (except industrial wastewater), which was primarily led by the non-agricultural population, from 2000 to 2009. This study suggests that the protection of water environments requires a comprehensive protection policy in addition to a unilateral protection policy. [Copyright &y& Elsevier]

In this study, the influencing factors and sources of historical changes in polycyclic aromatic hydrocarbons (PAHs) in the sediment core of Fuxian Lake were analyzed. Before 1970, the Σ 16 PAH concentration fluctuated widely, with one or more maximum values. During 1971–2004, the Σ 16 PAH concentration showed a slow growth trend, while during 2005–2017, the concentration increased sharply, reaching a peak value of 821 ng g−1. dw in 2017. The results of a positive matrix factorization (PMF) model demonstrated that before 1970, PAHs were mainly derived from biomass burning in the Fuxian Lake sediment core, with an overall contribution of 40 %. During 1971–2004, the source of PAHs was mainly coal combustion, with an overall contribution of 34 %. During 2005–2017, PAHs primarily originated from traffic, with an overall contribution of 33 %. Population, coal, GDP, motor, and petroleum had a significant influence on low molecular weight (LMW) PAHs in 1980–2004 and 2005–2017. Motor, coal, population, and GDP had a greater impact on high molecular weight (HMW) PAHs. Before 1970 and in 1971–2004, meteorological factors had little effect on PAHs in the sediment core in Fuxian Lake. During 2005–2017, day and rainfall were significantly negatively correlated with HMW PAHs, while temperature and wind were not correlated with PAH concentrations. During 2005–2017, total organic carbon (TOC) and total nitrogen (TN) had greater adsorption effects on HMW PAHs than on LMW PAHs. Before 1970 and in 1971–2004, the adsorption effects of TOC and TN on 3–4-ring PAHs were greater than those of 2-ring and 5–6-ring PAHs. Total phosphorus (TP) had no adsorption effect on PAHs in the entire sedimentary column. [Display omitted] • Coal combustion and vehicle emissions have been the main sources of PAHs since 1970s. • The contributions of coal and motor to HMW PAHs have gradually increased. • The decrease in day and rainfall will reduce the removal of HMW PAHs. • The adsorption effects of TOC, TN and TP on HMW PAHs are greater than on LMW PAHs. [ABSTRACT FROM AUTHOR]

• PCA-MLR, PMF, and Unmix receptor models were successfully identified PAHs sources in sediment core. • PAHs reached its peak around 2000 in a remote lake of Tibet Plateau. • Biomass and coal combustion are important soueces of PAHs in sediments. • Temporal trends of factor contributions were consistent with different ring number PAHs. Receptor models are a useful tool for identifying sources of polycyclic aromatic hydrocarbons (PAHs) in multiple environmental media. In this study, three different receptor models (including the principal component analysis-multiple linear regression (PCA-MLR), positive matrix factorization (PMF), and Unmix models) were used to apportion the sources of 16 priority PAHs in a sediment core of Lake Dagze Co. The ∑PAHs (sum of all 16 measured PAHs) concentrations ranged from 51.89 to 132.82 ng/g with an average of 80.39 ng/g. The ∑PAHs were dominated by 2-3 ring PAHs, accounting for 80.12% on average, thereby indicating that they mainly originated from biomass and coal combustion and/or from long-range atmospheric transportation. The three models produced consistent source apportionment results. The greatest contributor to ∑PAHs was biomass combustion, followed by coal combustion, vehicle emissions, and petrogenic sources. Moreover, the temporal variation of the common sources was well-correlated among models. The multi-method comparison and evaluation results showed that all three models were useful tools for source apportionment of PAHs, with the PMF model providing better results than the PCA-MLR and Unmix models. The temporal trends of factor contributions were verified by PAHs with different ring numbers. Significant correlations were found between the simulated concentrations of each source factor and the PAHs with different ring numbers (P <0.01), except for the petrogenic source identified by the Unmix model (P >0.05). This study can provide useful information for further investigation of source apportionment of PAHs in the sediment cores. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • PAHs concentration in sediments was the highest (C 3 , 1.88E-03–2.64E-03 mol/m3). • PAHs transport from air to water and then to sediment. • Lowest PAH concentration was found under SSP3 (2025–2035) in future projections. This study analyzed the fate and transfer of PAHs through multiple media in Dianchi Lake and the sediment records of polycyclic aromatic hydrocarbons (PAHs) in sediments. The model simulation results showed the simulated concentrations to be in good agreement with the measured values. The concentration and total amount of PAHs were the highest in the sediment, which is an important sink for PAHs in lake systems. The main transport direction of the PAHs in the three phases was from the atmosphere to the water to the sediment. Advection and emission inputs were the primary input pathways for PAHs in the atmosphere, and advection output was the main removal path. The main input sources pathways for PAHs in sediments was the sedimentation of particulate matter in water, with diffusion and degradation being the primary methods of removal. Advection and atmospheric dry and wet deposition were the main sources of PAHs in water, with particulate deposition being the primary removal process. The range of PAHs was 336–3520 ng/g in sediments in Dianchi Lake, with an average of 1569 ng/g, peaking in 2012. Among the predicted future PAH concentrations in the sediments under the five shared socioeconomic pathways (SSPs), the lowest PAH concentration was found under SSP3 from 2025 to 2035, whereas the lowest PAH concentration was found under SSP4 from 2035 to 2050. In the sustainable path of SSP1, although the concentration of PAH pollutants showed an increasing trend in the short term, the increase in PAHs concentration in sediments slowed in the long run. [ABSTRACT FROM AUTHOR]

Human activity has fundamentally altered the global phosphorus (P) cycle. Yet our understanding of when and how humans influenced the P cycle has been limited by the scarcity of long-term P sequestration records, particularly outside Europe and North America. Lake sediments provide a unique archive of past P burial rates and allow the human-mediated disruption of the global P cycle to be examined. We compiled the first global-scale and continentally resolved reconstruction of lake-wide Holocene P burial rates using 108 lakes from around the world. In Europe, lake P burial rates started to increase noticeably after ∼4000 calendar years before 1950 CE (cal BP), whereas the increase occurred later in China (∼2000 cal BP) and in North America (∼550 cal BP), which is most likely related to different histories of population growth, land-use and associated soil erosion intensities. Anthropogenic soil erosion explains ∼86% of the observed changes in global lake P burial rates in pre-industrial times. We also provide the first long-term estimates of the global lake P sink over the Holocene (∼2686 Tg P). We estimate that the global mean lake sediment P sequestration since 1850 CE (100 cal BP) is ∼1.54 Tg P yr−1, representing approximately a six-fold increase above the mean pre-industrial value (∼0.24 Tg P yr−1; 11,500 to 100 cal BP) and around a ten-fold increase above the Early-Middle Holocene low-disturbance baseline of 0.16 Tg P yr−1. This study suggests that human activities have been affecting the global P cycle for millennia, with substantial alteration after industrial times (1850 CE). • We estimated Holocene phosphorus (P) burial rates in sediments of 108 global lakes. • Global lake P burial rates increased notably in the Late Holocene. • Human-induced soil erosion caused early increases in lake sediment P burial rates. • We observed different patterns of lake P burial rates among continents since the Late Holocene. • We provide the first estimates of long-term, global P sequestration in lake sediments throughout the Holocene. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) have received worldwide attention due to their potential teratogenic, persistent, and carcinogenic characteristics. In this study, the PAHs concentrations in two dated sediment cores taken from central Tibetan Plateau (TP) were analyzed to study the deposition history, potential sources, ecological risks, and influencing factors. Total concentration of PAHs (∑PAHs) ranged from 50.0 to 195 ng g−1 and 51.9–133 ng g−1 in sediments of Pung Co (PC) and Dagze Co (DZC), respectively. 2–3-ring PAHs were dominant in the two lake sediments, accounting for an average of 77.5% and 80.1%, respectively. The historical trends of ∑PAHs in the two lakes allowed to distinguish three periods, namely, relative stability before the 1950s, a gradual increase between the 1950s and the 1990s, and then a decline to the present-day. In addition, the trend in the concentration level of each PAH composition was consistent with ∑PAHs before the 1990s, while they exhibited different trends since the 1990s, which may be the result of a combination of anthropogenic activities and climate change in recent years, whereas before the 1990s the PAH profile was mainly influenced by atmospheric deposition. The results of source apportionment examined according to diagnostic ratios and positive matrix factorization were consistent and revealed that PAHs were primarily derived from biomass and coal combustion. Significant correlations between PAHs and organic carbon (OC) indicate that OC might be a key factor influencing the concentration of PAHs in sediments. The ecological risk assessment demonstrated that PAHs in TP sediments occurred at a low risk level. Results of this study could be helpful to develop a deeper insight into the deposition history of PAHs in remote lakes of the TP region and explore the response of these variations to climate change and human activities. • Sediment cores in remote lakes from the Tibetan Plateau were analyzed for PAHs. • 2–3-ring PAHs were predominant in the sediments. • Biomass and coal combustion were the main sources of PAHs. • OC was a key factor influencing the concentrations of PAHs in sediments. • Climate change and anthropogenic activities have influenced PAH composition since the 1990s. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) in sediment pore water plays a key role in lake water quality, complexation of the contaminants, biogeochemical cycles, and even climate. To better understand the vertical dynamics and characteristics of DOM among pore water profiles, we investigated concentrations, chemical structures, and benthic fluxes of DOM in plateau lake sediments via stoichiometric analysis, ultraviolet–visible (UV–vis) absorption, three-dimensional fluorescence matrix spectroscopy (EEMs), and parallel factor model (PARAFAC). The results revealed that dissolved organic carbon (DOC), concurrent with chromophoric DOM (CDOM) and fluorescent DOM (FDOM), tended to accumulate in the anaerobic deeper layers. These trends also demonstrated a good agreement with the ammonium nitrogen (NH 4 +-N) concentration, implying that the pathway of DOM dynamics was closely related to the redox state. The EEMs-PARAFAC model revealed that DOM in pore water mostly consisted of two terrestrial humic-like components (average contribution:> 60%) followed by microbial and tryptophan-like components, respectively. Terrestrial humic-like components were relatively stable, and their abundance was positively correlated with the FDOM level (p < 0.05). The changes of aromatic, molecular weight, and humification degree of DOM were possibly driven by microbial activities at different depths. Moreover, benthic flux estimations indicated that DOM and the total dissolved nitrogen (TDN) in inland sediments were potential sources for the overlying water and possibly affected the quality and ecological safety of lake water bodies. [ABSTRACT FROM AUTHOR]

Sixteen polycyclic aromatic hydrocarbons (PAHs) in a sediment core from Dianchi Lake, southwest China, were analysed. The influence of changes in China's energy structure for 2–6 ringed PAHs was investigated to assess sources and the impact of socioeconomic development on temporal changes in concentrations. The concentration of the ΣPAH 16 ranged from 746 to 2293 ng g−1. Prior to the 1960s relatively low concentrations of the ΣPAH 16 and a larger proportion of 2–3-ring PAHs indicated that biomass combustion was the main source of PAHs. A rapid increase in the concentrations of 2–3 ring PAHs between 1975 and 2004 was attributed to population growth and coal consumption. A declining trend since 2004 was interpreted as being due to local changes in household energy usage. Increased concentrations of 4-ring PAH between 1975–2005 and 5–6-ring PAHs between the 1980s to 2004 showed correlations with increased coal consumption and the number of motor vehicles, respectively. These were caused by rapid urbanization and industrialization in the Dianchi watershed following the implementation of the Reform and Open Policy in 1978. A subsequent decline in the concentrations of 4-ring and 5–6-ring PAHs may have been due to decreased coal consumption and improvements in emission standards, respectively. Source apportionment by a PMF model revealed that coal combustion (29.2%), vehicle emissions (24.2%), petrogenic sources (21.8%), and biomass combustion (24.9%) were the sources of PAHs in the lake sediment core, and that coal combustion was the most important regional source of PAHs pollution. Image 1 • Sixteen PAHs from Dianchi lake sediment, a plateau lake in China, were studied. • Sediment record of PAHs reflect trends in GDP and total energy consumption. • Sediment records of different PAH rings can reflect the changes of energy structure. • Coal and biomass combustion, vehicle emissions and petrogenic were the PAHs sources. • Time trend of factor contributions are consistent with economic parameters. [ABSTRACT FROM AUTHOR]