Shallow Lake Sediments Research Articles

Occurrence, source apportionment, and ecological risk of potentially toxic elements in an urban shallow lake sediment

ABSTRACT This study evaluated the occurrence, spatial distribution, source, and ecological risk of potentially toxic elements (PTEs) in the sediment of an urban shallow lake in a mid-sized city. The ecological risk indices, enrichment factor (EF) and geoaccumulation index (Igeo) indicated high enrichment and contamination with Cd and moderate enrichment with Ni and Hg, while the potential risk index (RI) showed a moderate ecological risk. The mean contributions of individual PTE species to the total risk were in the following order: Cd > Hg > Ni > As > Cu > Pb > Cr > Zn. The sediment quality guideline (SQG) indices revealed that biological effects might occur occasionally due to the Cd and Ni contamination and a low or relatively insignificant risk of adverse biological effects from other PTEs. There were moderate to strong positive inter-metal relationships that suggested their common sources. The primary source responsible for elevated PTE concentrations was the traffic-related discharge. The main contributors to ecological risks were Cd and Ni. These findings highlight the importance of paying attention to the ecological environment of urban shallow lakes, which are particularly sensitive to their surroundings.

Source-Oriented Health Risks and Distribution of BTEXS in Urban Shallow Lake Sediment: Application of the Positive Matrix Factorization Model

Source-Oriented Health Risks and Distribution of BTEXS in Urban Shallow Lake Sediment: Application of the Positive Matrix Factorization Model

Shallow lake response to Holocene climate variation in south-central Minnesota, USA

Sedimentary deposits in lakes across the upper Midwest record the co-evolution of climate and biogeochemistry since the retreat of the Laurentide Ice Sheet at the end of the last glacial period. Here, we report on a Holocene lake sediment record from Chub Lake, a shallow (3 m depth) eutrophic lake system in south-central Minnesota. High-resolution elemental data from scanning XRF along with variations in organic matter, carbonate minerals, clastic material, biogenic silica, charcoal, and carbon isotopes reveal internally consistent patterns of hydroclimatic influence on this shallow lake system from 11,300 years BP to present. In particular, authigenic carbonate mineral formation and preservation in Chub Lake appears to be well suited as a moisture proxy beginning around 9700 BP up until ∼2300 BP, when a combination of more humid climates and basin-infilling change the hydrology of Chub Lake. This work emphasizes the importance of evaluating shallow lake sediment records both as important archives of climate proxies and case studies on how changing climates impact aquatic systems.

Fragmentation and separation of diatom valves in modern shallow lake sediments: a case study in Lake Kitaura, Japan

Fragmentation and separation of diatom valves in modern shallow lake sediments: a case study in Lake Kitaura, Japan

Integrated methodology for gas content assessment and prediction in shallow muddy lake sediments: acoustic mapping and correlation analysis

This paper provides a step-by-step description of integrated methodology for quantification and prediction of gas (methane, CH4) content dynamics in shallow aquatic sediments under changing spatial and temporal conditions. Presence of gas bubbles even in small concentrations significantly affects sediment compressibility, which in turn decreases sound speed in sediment. Our integrated methodology consists of two basic steps. In the first step, free gas content is evaluated by acoustic applications based on the sound speed inferred from the reflection coefficient from gassy bottom. The experimental bottom reflections are registered and compared to the simulated ones, using a geoacoustic inversion technique. The best match between the model and the experiment provides sediment sound speed estimate, which is converted into free gas content using a basic relation. In the second step, a multivariate linear regression is fitted for gas content and closed form expression of gas content dependence on the following predictors, which change spatially and temporally over the aquatic ecosystem, is obtained: 1) water depth, 2) short-leaving CH4 production rate peaks fueled by punctuated organic matter deposition; and 3) CH4 bubble dissolution rates.•Gas content and sound speed in the sediment are estimated via the geoacoustic inversion technique by matching the experimentally recorded and simulated bottom reflections•Only single source and receiver are required for the acoustic methodology•A multivariate linear regression is fitted for gas content to indicate its dependence on various predictors that change spatially and temporally over the lake

Distribution Patterns of Sediment Organic Carbon Stocks in Shallow Lakes and the Significance for Sustainable Lake Management: Chaohu Lake in Eastern China as a Case Study

Shallow lake sediments have huge potential for carbon storage, but they are vulnerable to various environmental changes and are highly susceptible to becoming a source of carbon emissions. Understanding the amount of sediment carbon storage can provide information about the potential of shallow lakes in mitigating climate change. In this study, sediment sampling was conducted at 12 study sites in Chaohu Lake, China, and sediment water content, grain size, bulk density, and sediments organic carbon (SOC) content were examined in five layers along the vertical direction, respectively, and the distribution and storage of SOC were estimated. The results showed that the surface sediments in the west lake area of Chaohu Lake would release 66,300 t of SOC to the overlying water body in the future. The sediments in the middle lake area and the east lake area will absorb another 15,900 t and 17,300 t of TOC from the water body in the future, respectively. Overall, the lake-wide sediments will release 33,100 t of SOC into the water body in the future. In addition, the results of the study also indicate that human activities are another major influence on the change in organic carbon stocks in lake sediments, and therefore, proactive measures for the restoration and protection of lake sediments are essential because increasing the SOC stocks in the sediments and maintaining the lakes in a sustainable manner can contribute to the crucial role they play in mitigating climate change.

Size matters: Aerobic methane oxidation in sediments of shallow thermokarst lakes

AbstractShallow thermokarst lakes are important sources of greenhouse gases (GHGs) such as methane (CH4) and carbon dioxide (CO2) resulting from continuous permafrost thawing due to global warming. Concentrations of GHGs dissolved in water typically increase with decreasing lake size due to coastal abrasion and organic matter delivery. We hypothesized that (i) CH4 oxidation depends on the natural oxygenation gradient in the lake water and sediments and increases with lake size because of stronger wind‐induced water mixing; (ii) CO2 production increases with decreasing lake size, following the dissolved organic matter gradient; and (iii) both processes are more intensive in the upper than deeper sediments due to the in situ gradients of oxygen (O2) and bioavailable carbon. We estimated aerobic CH4 oxidation potentials and CO2 production based on the injection of 13C‐labeled CH4 in the 0–10 cm and 10–20 cm sediment depths of small (~300 m2), medium (~3000 m2), and large (~106 m2) shallow thermokarst lakes in the West Siberian Lowland. The CO2 production was 1.4–3.5 times stronger in the upper sediments than in the 10–20 cm depth and increased from large (158 ± 18 nmol CO2 g−1 sediment d.w. h−1) to medium and small (192 ± 17 nmol CO2 g−1 h−1) lakes. Methane oxidation in the upper sediments was similar in all lakes, while at depth, large lakes had 14‐ and 74‐fold faster oxidation rates (5.1 ± 0.5 nmol CH4‐derived CO2 g−1 h−1) than small and medium lakes, respectively. This was attributed to the higher O2 concentration in large lakes due to the more intense wind‐induced water turbulence and mixing than in smaller lakes. From a global perspective, the CH4 oxidation potential confirms the key role of thermokarst lakes as an important hotspot for GHG emissions, which increase with the decreasing lake size.

The Effects and Mechanisms of pH and Dissolved Oxygen Conditions on the Release of Arsenic at the Sediment-Water Interface in Taihu Lake.

The pH and dissolved oxygen (DO) conditions are important environmental factors that control the migration of arsenic (As) at the sediment-water interface. This study investigates the distribution differences of reactive iron, manganese, and arsenic at the sediment-water interface under anaerobic and aerobic conditions at different pH levels. The strong buffering capacity of sediment to water pH results in a shift towards neutral pH values in the overlying water under different initial pH conditions. The level of DO becomes a key factor in the release of As from sediment, with lower DO environments exhibiting higher release quantities and rates of As compared to high DO environments. Under low DO conditions, the combined effects of ion exchange and anaerobic reduction lead to the most significant release of As, particularly under pH 9.5 conditions. The formation of amorphous ferrous sulfide compounds under low DO conditions is a significant factor contributing to increased arsenic concentration in the interstitial water. Therefore, the re-migration of endogenous arsenic in shallow lake sediments should consider the combined effects of multiple driving forces.

In situ effects of microplastics on the decomposition of aquatic macrophyte litter in eutrophic shallow lake sediments, China

The toxicity of microplastics (MPs) to aquatic organisms has been extensively studied recently. However, few studies have investigated the effects of MPs in sediments on aquatic ecosystem functioning. In the present study, we conducted an in situ experiment to explore the concentration-dependent effects (0.025%, 0.25%, 2.5%) and size-dependent effects (150–300 μm and 500–1000 μm) of polypropylene microplastics (PP MPs) on Vallisneria natans litter decomposition dynamics, in particular, the process associated with macroinvertebrates, microorganisms, as well as microalgae and/or cyanobacteria. The results showed that exposure to high concentrations and large sizes of PP MPs can accelerate leaf litter biomass loss and nutrition release. Moreover, microbial respiration, microalgal and/or cyanobacteria chlorophyll-a were also significantly affected by PP MPs. However, PP MPs have no effect on the abundance of associated macroinvertebrate during the experiment, despite the collection of five macroinvertebrate taxa from two functional feeding groups (i.e., collectors and scrapers). Therefore, our experiment demonstrated that PP MPs may enhance leaf litter decomposition through effected microbial metabolic activity, microalgal and/or cyanobacteria biomass in the sedimentary lake. Overall, our findings highlight that PP MPs have the potential to interfere with the basic ecological functions such as plant litter decomposition in aquatic environments.

Mechanisms of high ammonium loading promoted phosphorus release from shallow lake sediments: A five-year large-scale experiment

The unprecedented global increase in the anthropogenic-derived nitrogen (N) input may have profound effects on phosphorus (P) dynamics and may potentially lead to enhanced eutrophication as demonstrated in short-term mesocosm experiments. However, the role of N-influenced P release is less well studied in large-scale ecosystems. To gain more insight into ecosystem effects, we conducted a five-year large-scale experiment in ten ponds (700–1000 m2 each) with two types of sediments and five targeted total N concentrations (TN) by adding NH4Cl fertilizer (0.5, 1, 5, 10, and 25 mg N L−1). The results showed that: (ⅰ) The sediment P release increased significantly when TN exceeded 10–25 mg N L−1. (ⅱ) The most pronounced sediment P release increase occurred in summer and from sediments rich in organic matter (OMSed). (ⅲ) TN, algal biomass, fish biomass, non-algal turbidity, sediment pH, and OMSed were the dominant factors explaining the sediment P release, as suggested by piecewise structural equation modeling. We propose several mechanisms that may have stimulated P release, i.e. high ammonium input causes a stoichiometric N:P imbalance and induce alkaline phosphatase production and dissolved P uptake by phytoplankton, leading to enhanced inorganic P diffusion gradient between sediment and water; higher pelagic fish production induced by the higher phytoplankton production may have led increased sediment P resuspension through disturbance; low oxygen level in the upper sediment caused by nitrification and organic decomposition of the settled phytoplankton and, finally, long-term N application-induced sediment acidification as a net effect of ammonium hydrolysis, nitrification, denitrification; The mechanisms revealed by this study shed new light on the complex processes underlying the N-stimulated sediment P release, with implications also for the strategies used for restoring eutrophicated lakes.

Application of High-Resolution Sub Bottom Profiling Data for the Interpretation of Shallow Lake Sediments

Application of High-Resolution Sub Bottom Profiling Data for the Interpretation of Shallow Lake Sediments

Interactions between distal epiclastic and bio‐chemogenic sedimentation at the foothills of a mafic alkaline volcano: The case of the Oligocene Doupovské Hory Volcanic Complex (Czech Republic)

AbstractLate Oligocene (ca 25 Ma) volcano‐sedimentary successions exposed on the western periphery of the Doupovské Hory Volcanic Complex reveal a complex sedimentation history influenced in various ways by decay of the alkali basalt volcanic edifice. Weathering of the volcanic rocks supplied abundant reactants that promoted carbonate precipitation in the peripheral palaeolakes—as evidenced by strongly non‐radiogenic 87Sr/86Sr values (0.7038–0.7041). On the other hand, the sediments of the initial shallow lake became deformed by the bulldozing effect of a debris avalanche. The debris flow and avalanche deposits filled up the original depression, modified the basin morphology and shifted the peripheral lacustrine setting further away from the volcano. At this stage, surface water influx from the surrounding granites conferred a more radiogenic character (87Sr/86Sr values 0.7046–0.7049) to the calcrete deposits. Fossil assemblages as well as limestone textures suggest significant seasonal water‐level fluctuations, possibly reflecting the alternating rainy and dry‐seasons of a prevalently humid Central‐European Late Oligocene climate. The seasonal drying out of the ponds resulted in significant 18O enrichments. Although the ca 0‰ δ13C values might suggest mixing of atmospheric and volcanic CO2 during carbonate precipitation, no active volcanic conduits of relevant age are known in the close vicinity. The lower δ13C values are likely a result of mantle degassing through rift faults, a phenomenon observed in the magmatically extinct Ohře Rift until present. This paper demonstrates that limestones derived from weathered alkaline basalts are characterised by highly non‐radiogenic Sr isotopic ratios (87Sr/86Sr ca 0.704), suggesting a magmatic origin for the Ca within these carbonates. Contrary to the notion of carbonatites being present when highly non‐radiogenic Sr isotopes are found, these results show that Sr isotopes in carbonates formed in alkali basalt‐sourced environments only reveal the source of the Sr (and Ca) ions, not necessarily the presence of carbonatite.

Ecological risk characteristics of sediment-bound heavy metals in large shallow lakes for aquatic organisms: The case of Taihu Lake, China

Heavy metal contamination in the surface sediments of large shallow lakes in China is becoming increasingly serious. However, more attention has been paid to the human health risk of heavy metals in the past, while little consideration has been given to aquatic organisms. Taking Taihu Lake as an example, we explored the spatial and temporal heterogeneity of the potential ecological risks of seven heavy metals (Cd, As, Cu, Pb, Cr, Ni, and Zn) to species at different taxonomic scales using an improved species sensitivity distribution (SSD) method. The results showed that all six heavy metals, except Cr, were exceeded to some extent compared to background levels, with Cd being the most severe exceedance. Based on the hazardous concentration for 5% of the species (HC5), Cd had the lowest HC5 value, implying the highest ecological risk of toxicity. Ni and Pb had the highest HC5 values and the lowest risk. Cu, Cr, As and Zn were at a relatively moderate levels. For the different groups of aquatic organisms, the ecological risk of most heavy metals was generally lower for vertebrates than for the whole species. The risk for invertebrates and algae was higher than that for all species. Zn and Cu had the highest potentially affected fractions (PAFs) for all classification cases, with mean PAFs of 30.25% and 47.2%, respectively. Spatially, the high ecological risk of sediment heavy metals was significantly related to the spatial characteristics of the type and intensity of human activities in the catchment. Administratively, the environmental quality standards for freshwater sediments proposed by America and Canada are insufficient to protected against the ecological risks of heavy metals in Taihu Lake. In the absence of such standards, China urgently needs to establish an approptiate system of environmental quality standards for heavy metals in lake sediments.

Effects of Fe(II) and organic carbon on nitrate reduction in surficial sediments of a large shallow freshwater lake

Nitrate-reducing ferrous [Fe(II)]-oxidizing (NRFO) has been reported from lake sediments as a natural reduction pathway. However, the effects of the contents of Fe(II) and sediment organic carbon (SOC) on the NRFO process still remain unclear. In this study, the influences of Fe(II) and organic carbon on nitrate reduction were analyzed quantitatively at two typical seasonal temperatures (25 °C representing summers and 5 °C for winters) by conducting a series of batch incubation experiments, using surficial sediments at the western zone of Lake Taihu (Eastern China). Results showed that Fe(II) greatly promoted NO3‾-N reduction by denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) processes at high-temperature (25 °C, representing summer season). As Fe (II) increased (e.g., Fe(II)/NO3‾ = 4), the promotion effect on NO3‾-N reduction was weakened, but on the other side, the DNRA process was enhanced. In comparison, the NO3‾-N reduction rate obviously decreased at low-temperature (5 °C, representing the winter season). NRFO in sediments mainly belongs to biological rather than abiotic processes. A relatively high SOC content apparently increased the rate of NO3‾-N reduction (r = 0.023–0.053 mM/d), particularly on the heterotrophic NRFO. It is interesting that the Fe(II) consistently remained active in the nitrate reduction processes no matter whether SOC was sufficient in the sediment, particularly at high-temperature. Overall, the combining effects of both Fe(II) and SOC in surficial sediments made a great contribution towards NO3‾-N reduction and N removal in a lake system. These results provide a better understanding and estimation of N transformation in sediments of the aquatic ecosystem under different environmental conditions.

Spatio-temporal dynamic diversity of bacterial alkaline phosphatase phoD gene and its environmental drivers in sediments during algal blooms: A case study of shallow Lake Taihu

Bacterial alkaline phosphatase encoded by the phoD gene is essential for phosphorus (P) cycling in ecosystems. Until now, knowledge of the phoD gene diversity in shallow lake sediments is still lacking. In this study, from early to late stage of cyanobacterial blooms, we investigated the dynamic changes of the abundance of phoD gene (hereafter phoD abundance) and phoD-harboring bacterial community composition (hereafter phoD-harboring BCC) in sediments from different ecological regions of Lake Taihu, the third-largest shallow freshwater lake in China, as well as explored their environmental driving factors. Results showed that phoD abundance in the sediments of Lake Taihu showed spatiotemporal heterogeneity. The highest abundance was found in macrophyte-dominated area (mean 3.25*106copies/g DW), where Haliangium and Aeromicrobium were identified as the major contributors. Due to the negative impact of Microcystis species, phoD abundance decreased significantly (by 40.28% on average) during cyanobacterial blooms in all other regions except the estuary area. The phoD abundance in sediment was positively correlated with total organic carbon (TOC) and total nitrogen (TN). However, the relationship between phoD abundance and alkaline phosphatase activity (APA) varied with time, showing positive correlation (R2 = 0.763, P < 0.01) in the early stage of cyanobacterial blooms, but not (R2 = −0.052, P = 0.838) in the later stage. The predominant phoD-harboring genera in sediments were Kribbella, Streptomyces and Lentzea, all of which belong to Actinobacteria. Non-metric multidimensional scaling (NMDS) analysis revealed that the spatial heterogeneity of phoD-harboring BCC in the sediments of Lake Taihu was significantly higher than the temporal heterogeneity. TP and sand were the principle environmental factors affecting the phoD-harboring BCC in the sediments of the estuary area, while DO, pH, organic phosphorus (Po) and diester phosphorus were the key driving factors for other lake regions. We concluded that the C, N, and P cycles in sediments might work in concert. This study extends the understanding of the phoD gene diversity in shallow lake sediments.

Day‐night variation of microbial organic matter use in sediments of a saline shallow lake

Abstract Knowledge of microbial functioning linked to dissolved organic matter (DOM) in hypersaline lakes is limited. This study aimed to understand this relationship in surface and subsurface sediments and how it is affected by daytime and night‐time variability. A sampling regime, including daytime and night‐time measurements, was designed to record aerobic respiration, extracellular enzyme activity (β‐glucosidase, leu‐aminopeptidase and phosphatase), prokaryotic cell density and viability, content of pigment and extracellular polymeric substances (EPS), and organic matter weight in the surface and subsurface sediments. The main physicochemical characteristics and optical properties of DOM in the surface and interstitial waters were determined. Larger differences were detected in biofilm microbial activity between surface and subsurface sediments than between day and night, as a result of higher prokaryotic cell density and higher availability of fresh DOM at the surface, possibly released from primary production. Redox conditions, pH and DOM quantity and quality were strongly correlated with enzyme activity and variability in respiration, and might determine (through modifying nitrogen (N) and phosphorus (P) availability) how microbes use organic compounds differently at the two sediment depths. Low prokaryotic viability indicated that the microbial community was stressed in both surface and subsurface sediments. By contrast, higher EPS and pigment content and lower metabolic efficiency at the surface layer indicated harsher conditions compared to the subsurface layer. Pigment presence and variation in daily oxygen levels in the subsurface layer indicate that the two sediment depths are interconnected. Results suggest that surface and subsurface microbes have a distinct role in hypersaline shallow lake sediment. Microorganisms in surface sediments form a structured mat with high EPS and carotenoids and enhanced carbon metabolism. The mat also serves as a protection shield from light radiation, salinity and desiccation. At the subsurface, the lower availability of fresh organic compounds and oxygen reduces microbial biomass and activity which is, in turn, more efficient and focused on N and P acquisition.

Hydrodynamic effects on the ability of bottom traps to capture nutrient-rich sediments in shallow eutrophic lakes

Hydrodynamics are the key factor influencing sediment resuspension, transport and nutrient release in large shallow lakes. However, the hydrodynamic responses of bottom traps during pollutant capture remain unclear. In this study, a large eutrophic shallow lake was selected to carry out a field test of deep traps at the lake bottom. Based on observations of the lake current around the trap, the sedimentation rate of the particles in the trap and the nutrient content of the captured sediments, combined with the numerical simulation of the waves outside the trap, the effects of lake currents and waves on the sediment deposition in the traps were studied, and the response of the nutrient content of the sediments captured in the deep traps to the changes in lake currents and waves was analyzed. The results showed that the strong hydrodynamic force significantly promoted sediment deposition in the trap and enhanced the ability of the trap to capture sediments with high nutrient contents. The influences of waves and lake currents on the bottom trap capture of polluted sediments varied among different periods. Waves played the leading role in winter and spring, accelerating sediment capture in the bottom traps near the southern shore of eastern Lake Chaohu during this period. In summer, the lake current was the main dynamic factor contributing to the rapid deposition of particulate matter and the capture of sediments with high nutrient contents in the bottom traps of western Lake Chaohu. The multiple stepwise linear regression model based on lake current and wave data explained 37.6 % of the sediment deposition in the trap, and the model built for a single bottom trap explained more than 80 % of the deposition. After correcting the sediment deposition thickness in the trap by considering the water content of the sediment, the quantitative relation yield better inversion results for the sediment deposition process, and different thicknesses in the bottom trap were linked to different sediment deposition periods. According to the hydrodynamic strength in 2020, the thickness of the highly contaminated sediments captured by traps CC1-CC5 was calculated to be 1.09–1.93 m, and the corresponding TN and TP were 26.66–68.53 kg and 6.84–19.89 kg, respectively. This study provides a scientific analysis and guidance for the evaluation of endogenous nutrients captured by lake bottom trap methods.

Ecological risk assessment of glyphosate and its possible effect on bacterial community in surface sediments of a typical shallow Lake, northern China

Glyphosate is a widely used herbicide worldwide and its prevalent presence in aquatic ecosystems poses a threat to living organisms. This study evaluated potential ecological risk of glyphosate to sediment-dwelling organisms and assessed the probable effect of glyphosate on structure and predicated function of sediment-attached bacterial communities from a large shallow lake in northern China based on 16S rRNA high-throughput sequencing. Results suggested that glyphosate showed a medium to high concentration (up to 8.63 mg/kg) and chronic risk to sediment-dwelling organisms (10% samples exhibiting medium to high risk quotient), especially in sites nearby farmland and residential areas in August. Bacterial community identification based on 16S rRNA sequence indicated some species of dominant phylum Proteobacteria and Campilobacterota (e.g., Steroidobacteraceae, Thiobacillus, Gallionellaceae, Sulfurimonadaceae) were stimulated while some species of dominant phylum Actinobacteriota, Acidobacteriota and Firmicutes (e.g., Nocardioidaceae, Microtrichales, Vicinamibacteraceae, Paenisporosarcina) were inhibited by glyphosate accumulation. The stimulating species were related to sulfur-oxidizing, sulfate-, iron-, or nitrate-reducing bacteria; The inhibiting species were related to plant bacterial endophytes, polyphosphate-accumulating organisms (PAOs) and denitrifers. Correspondingly, promoted bacterial metabolic functions of “sulfite respiration”, “nitrogen respiration”, “aromatic compound degradation” and “nitrification” but suppressed “cellulolysis”, “manganese oxidation”, “anoxygenic photoautotrophy S oxidizing” and “nitrate denitrification” were predicated on functional annotation of prokaryotic taxa. Although these results could only partly suggest the impacts of glyphosate on the bacterial communities due to the lack of actual results from control experiments, the identified Steroidobacteraceae could be thought as a bioindicator in the future mechanism study for the ecological effect and bioremediation of glyphosate. This work intends to arise the concern about the depletion of biodiversity and bacterial metabolic functions with contribution of glyphosate in part in eutrophic lakes.

Plant Pigments and Organic Matter in the Bottom Sediments of Large Shallow Lakes in Northwestern Russia

Plant Pigments and Organic Matter in the Bottom Sediments of Large Shallow Lakes in Northwestern Russia

Optimizing spatial interpolation method and sampling number for predicting cadmium distribution in the largest shallow lake of North China

Cadmium (Cd) pollution has been widely recognized in lake ecosystems. Although the accurate prediction of the spatial distributions of Cd in lakes is important for controlling Cd pollution, the traditional monitoring methods of setting discrete and limited sampling points cannot actually reflect the continuous spatial distribution characteristics of Cd. In this study, we set up 93 sampling points in Baiyangdian Lake (BYDL), and collected surface water, overlying water and sediment samples from each sampling point. Cd contents were measured to predict their spatial distributions in different environmental components by three interpolation methods, inverse distance weighted (IDW), radial basis function (RBF) and ordinary kriging (OK), and the effects of different sampling numbers on the interpolation accuracy were also assessed to optimize the interpolation method and sampling number. The results showed that the interpolation accuracy of IDW decreased with increasing power values. The best basis function for RBF was IMQ, and the best semivariogram models for OK were the spherical model and stable model. The best interpolation method for the waters and sediments was RBF-IMQ compared with OK and IDW. Within the sampling number range of 50–93, the interpolation accuracy for Cd in surface water increased with the increase in sampling number. Comparatively, the interpolation accuracy was the highest for overlying water and sediments when the sampling number was 60. The findings of this work provide a combined sampling and spatial interpolation method for monitoring the spatial distribution and pollution levels of Cd in the waters and sediments of shallow lakes.