Sediments Of Erhai Lake Research Articles

Composition, distribution, and source of organic carbon in surface sediments of Erhai Lake, China

Lake sediment is an important organic carbon (OC) sink. Nevertheless, few studies have been conducted on sediment organic carbon (SOC) in lakes, and the effects of environmental variables on SOC pools remain poorly understood. We combined physicochemical and spectroscopic analyses to investigate the composition, distribution, and source of OC in surface sediments of Erhai Lake, southwest China, and explored the relationships between environmental variables and its SOC pool. The SOC pool consists of relatively high proportions of labile organic carbon fractions, mainly from algal production, which are rapidly decomposed and exhibit high turnover rates. The relative content of humus carbon ranges from 13.5 % to 20.5 %, with fulvic acid carbon predominating (average 52.95 %), indicating weak humification and a relatively active humus carbon pool. The dissolved organic matter in water column and sediments of Erhai Lake is largely influenced by endogenous production, with a great contribution from phytoplankton. Surface sediments contained more protein-like components than overlying waters (80.0 % vs. 63.0 %), attributed mainly to abundant algal deposition and intense bacterial metabolism. Among environmental variables, sediment chlorophyll a showed the strongest relationship with the SOC pool, and was associated with rapid decomposition and promotion of the humification process, which supported the conclusion that algae had an important influence on the SOC pool. The SOC pool in the southern region of the lake is mainly contributed by algae, other microorganisms, and sewage, exhibiting a greater potential to release organic matters into the water column. The center and northern SOC pools show relatively stable characteristics and stronger OC sink capacity, mainly because of the input of terrestrial refractory organic matters from runoff. Our data shed light on the OC storage mechanisms in the surface sediments of Erhai Lake and provide theoretical bases for enhancing the OC sink of sediments in the lake.

Distribution of antibiotic resistance genes in the sediments of Erhai Lake, Yunnan-Kweichow Plateau, China: Their linear relations with nonpoint source pollution discharges from 26 tributaries

Erhai Lake, a typical plateau deep water lake, experienced long-term nonpoint source (NPS) pollution discharge from 26 tributaries, which significantly affected the abundance and spread of resistance genes. In this study, 25 antibiotic resistance genes (ARGs), classified into six types, and NPS pollution discharges were investigated throughout around the Erhai basin. FCA (mexF) and sulfonamide resistance genes (sul1, sul2 and sul3) were the most common. Although the absolute overall abundance of ARGs there was low so far, the individual gene like sulfonamide resistance gene was high. Regression analysis using an ordinary least squares model (OLS) showed that the discharge of NPS pollution into Erhai Lake would have an obvious effect on the distribution of ARGs. And the relations between them were linear. Concretely speaking, the total nitrogen (TN) pollution input from tributaries could significantly correlated with the increasing of ARG abundance, while the total phosphorus (TP) pollution input showed the opposite correlation, and ultimately affect the distribution of ARGs. Moreover, the effect of TP on ARG distribution was more significant than TN. This study provides a geographical profile of ARG distribution in a subtropical deep lake on Yunnan-Kweichow Plateau. The results are beneficial for predicting the distribution characteristics of ARGs and controlling their pollution in plateau lakes.

Comprehensive assessment of heavy metal pollution and ecological risk in lake sediment by combining total concentration and chemical partitioning.

Total concentration and chemical partitioning of heavy metals are commonly used in environmental quality assessment; however, their comparability and comprehensive application are far less discussed. Herein, bioavailability, pollution and eco-risk of As, Cd, Cr, Cu, Ni, Pb and Zn in surface sediments of Erhai Lake were evaluated referring to multiple indices following the experimental methods of complete digestion, optimized Community Bureau of Reference (BCR) and 1.0M HCl extractions. Results of bioavailability for most metals were similar and comparable from BCR and HCl extractions. While bioavailable concentrations of Cd and Pb from HCl extraction were significantly (p<0.01) lower than those from BCR extraction, indicating BCR extraction is more efficient. Results of enrichment factor (EF) and concentration enrichment ratio (CER) suggested that Cd was the highest polluted element followed by As, Pb and Zn, whereas Cr, Cu and Ni were mainly natural in origin. Similar concentrations of anthropogenic As from EF and CER assessments indicated anthropogenic As mainly existed in bioavailable form. However, anthropogenic Cd, Pb and Zn existed in both bioavailable and residue forms, resulting in the underestimation of anthropogenic metals by the CER assessment. The sediment quality guidelines (SQGs), potential ecological risk index (Er) and risk assessment code (RAC) showed inconsistent eco-risks for each of the metals except Cd. Combining pollution level and chemical partitioning with SQGs, Er and RAC assessments, high eco-risk of Cd, moderate eco-risk of As and Pb, and low eco-risk of Cr, Cu, Ni and Zn were graded. Our study highlights the limitation of single index and the necessity of integrating multiple indices following total concentration and chemical partitioning in metal pollution and eco-risk assessments.

Study on the Release Potential of BPA and Steroid Estrogens in the Sediments of Erhai Lake, a Typical Plateau Lake of China.

On-site sampling analysis and laboratory-scale experiments were conducted to study the pollution status and release potential of EDCs in Erhai Lake. We found that nitrogen and phosphorus pollution in Erhai Lake sediment were both at a high level, as well as EDCs pollution. The concentrations of BPA, E2α, E1, E2β, EE2, and E3 were 36.84ng/g(DW), 13.04ng/g(DW), 128.97ng/g(DW), 52.57ng/g(DW), 18.48ng/g(DW) and 5.36ng/g(DW), respectively. The concentrations of E2α, E1, E2β and EE2 in the bottom water were higher than the surface water due to the impact of sediment release. The results of the 20days release test indicated that BPA release from the sediment had a greater correlation with the original concentration and the particle size of sediment, while the steroid EDCs had no obvious correlation with these two factors, probably due to the difference in hydrophobicity between them. Under hydraulic disturbance and aerobic conditions, the release process of EDCs was accompanied by a large amount of microbial degradation, and degradation amount > released amount. BPA was released quickly, 9.56% was released in 20days, but only 3.37% of steroid EDCs released. In comparison, the release process of steroids was longer and posed a greater threat to aquatic ecology.

Characteristics of Pore Water Dissolved Organic Nitrogen in the Sediment of Erhai Lake Basin, China

The distribution of Erhai Lake sediment pore water DON followed the pattern of middle (1.449 mg/L) > south (0.828 mg/L) > north (0.266 mg/L), with the highest concentrations being found in the least polluted areas. The sediment pore water DON mainly contained hydrophilic substances and substances derived from microbial sources. Most of these were integrated into humic acid-like substances (∼78%), which benefited for reducing sediment DON releasing risk. There were more chains in Erhai Lake sediment pore water DON, with a small number of aromatic substituents. The characteristics of DON components were suggested to be related to human activities.

Coupling characteristics and environmental significance of nitrogen, phosphorus and organic carbon in the sediments of Erhai Lake.

The contents and forms of nitrogen (N), phosphorus (P), and organic carbon (C) were determined with 40cm (approximately 1600s) core sediments from Erhai Lake on the Yungui Plateau of China as the sample. The vertical distribution characteristics, coupling relationships and ecological indicator significance of C-N-P were studied and identified. The results showed that the total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) contents were in the ranges of 1436-8255mg·kg-1, 1287-5462mg·kg-1, and 870.26-1507.74mg·kg-1, respectively. In the Erhai Lake sediments, the main forms of TOC, organic nitrogen (ON) and organic phosphorus (OP) were humus, TN, and TP, respectively. The deposition of C, N, and P in the Erhai Lake sediments was divided into four periods. In the initial development period (from 40 to 23cm), C, N and P were deposited and released synchronously; the main form of N was nontransferable total nitrogen (NTN), and that of P was inorganic phosphorus (IP). In the ecological recovery period (from 22 to 14cm), C and N were deposited synchronously, and their deposition amounts were more than that of P. C, N and P were released synchronously. The main form of N was transferable total nitrogen (TTN), and that of P was IP. In the rapid economic growth period (from 13 to 0cm), C, N, and P were deposited and released synchronously; the main form of N was NTN, and that of P was OP. In comparison to the other periods, this period was a period of higher active soil organic carbon (ASOC). In the integrated management period (surface sediment), C and N were deposited and released synchronously, and their deposition amounts were greater than that of P. The main form of N was NTN, that of P was OP, and the ASOC content was high. When exogenous inputs were the main sources of C, N, and P, the deposition forms of P and N were mainly OP and NTN, respectively, and those of IP and TTN were calcium-bound P (Ca-P) and ion-exchange form N (IEF-N), respectively. When endogenous inputs were the main sources of C, N and P, the deposition forms of P and N were mainly IP and TTN, respectively, and those of IP and TTN were Fe/Al-P and weak acid extractable form (WAEF-N), respectively. The content ratio of Ca-P and Fe/Al-P, as well as that of IEF-N and WAEF-N, could reflect the changes in the contribution of endogenous and exogenous sources to the Erhai Lake sediments.

Metagenome sequencing to unveil the resistome in a deep subtropical lake on the Yunnan-Guizhou Plateau, China

Erhai Lake in the Yunnan-Guizhou Plateau, a typical subtropical deep lake, experienced long-time input of nutrients and pollutants, which provides beneficial conditions for evolution and spread of resistance genes. In this study, the profile of bacterial community, antibiotic and metal resistance genes in sediments of Erhai Lake were analyzed via high-thought sequencing of 16S rRNA and metagenomic DNA. Proteobacteria, Firmicutes, Nitrospirae, and Bacteroidetes were found to be the main composition of the bacterial community. Multidrug-, bacitracin-, macrolide-lincosamide-streptogramin (MLS)- and tetracycline resistance genes were the primary antibiotic resistance gene (ARG) types with high relative abundance, whereas Multi-metal-, and arsenic- resistance genes were the primary metal resistance gene (MRG) types. The effects of nitrogen and phosphorus on the abundance of ARGs and MRGs depended on the different types. Some specific ARG (fosmidomycin resistance genes) and MRG types (multi-metal resistance genes) also showed significant geographic distribution. Bacterial community was the main driver shaping the resistome. Nutrients also played an essential role in structuring the bacterial community and resistome in the sediments of Erhai Lake. This study sheds light on the distribution and fate of resistome under a high load of nitrogen and phosphorus in a deep lake.

Effects and Differences of the Release of Dissolved Organic and Inorganic Phosphorus in Different Sediments Covered by Different Materials of Erhai Lake

In this work, the effects of four covering materials on the release of total dissolved phosphorus (DTP), dissolved organic phosphorus (DOP), and soluble reactive P (SRP) in different sediments of Erhai Lake were simulated. The results showed that the max release of DTP was reduced in covering material, which attributed to the changes of pH, Eh and characteristics of dissolved organic matter (DOM) by the effect of covering material. The application of iron oxide material significant reduced the release of DTP in the northern and southern part of the lake, with decrease rate of 44.3% and 35.7%, respectively. by contrast, the application of aluminum oxide material significant reduced the release of DTP in the middle part sediment, with decrease rate of 29.6%. Furthermore, the release of SRP and DOP in different sediments has significant difference after added different material. In northern part of sediment, the release of SRP and DOP reduced by 35.6% and 36.2% after added iron oxide material. This is because iron oxide can reduce the pH and Eh but increase the availability of DOM in northern, and then benefits for inhibiting the release of SRP and DOP. In the middle, the release of sediment SRP and DOP reduced by 28.9% and 31.6% after added aluminum oxide material. This is because the aluminum oxide can facilitate the availability of DOM in middle, and then inhibits the release of SRP and DOP. In southern part of the lake, the release of sediment SRP and DOP reduced by 47.4% and 16.5% after added iron oxide material. This is largely attributed to the effect of iron oxide on the pH and Eh. Therefore, to control the release of P in the sediment from Lake Erhai, iron oxide material should be selected in the northern and southern parts, whereas aluminum oxide should be selected in the middle part of the lake.

In-depth molecular characterization and biodegradability of water-extractable organic nitrogen in Erhai Lake sediment.

Dissolved organic nitrogen (DON) constitutes a significant fraction of the total dissolved nitrogen content of most aquatic systems and is thus a major nitrogen source for bacteria and phytoplankton. The present work applied Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to a compound-level analysis of the depth-dependent molecular composition of water-extractable organic nitrogen (WEON) in lake sediment. The study focused on Erhai Lake, China. It was found that a large portion (from 16.33 ± 7.87 to 39.54 ± 5.77%) of the WEON in the lake sediment was reactive under cultivation by algal or bacteria. The WEON in the mid-region of Erhai sediment particularly exhibited a lower bioavailability, having been less affected by the basin environment. The FT-ICR MS results revealed the presence of thousands of compounds in the Erhai Lake sediment samples collected at different depths, with the N-containing compounds accounting for 28.3-34.4% of all the compounds. The WEON molecular weight was also observed to increase with increasing sediment depth. A van Krevelen diagram showed that the lignin-type components were dominant (~ 56.2%) in the sediment WEON, contributing to its stabilization and reducing the risk of sediment nutrient release. The FT-ICR MS results further revealed 204 overlapping formulas of WEON for each core sediment sample, attributable to the presence of refractory components. It was observed that 78.4% of the formulas were within the lignin-like region, suggesting unique allochthonous DON sources. The aliphatic component proportion of all the unique formulas was also found to increase with increasing sediment depth. This indicates that, with the development and evolution of the Erhai Basin, the more labile WEON components were transformed into more stable lignin-like substrates, with a positive effect on the Lake Erhai ecosystem. Graphical abstract ᅟ.

Characteristics of Water Extractable Organic Nitrogen from Erhai Lake Sediment and Its Differences with Other Sources

The 47 samples from Erhai Lake surface sediments were collected in different seasons. The distribution and structure characteristics of sediment water extractable organic nitrogen(WEON) were investigated by using the combined techniques of UV-Vis absorption and three-dimensional excitation-emission matrix spectra(3DEEMs). The differences in DON of various sources(overlying water, pore water, inflow Rivers and wet deposition) were explored to analyze its effects on sediment. The results showed that:1the temporal distribution followed the pattern of summer > spring > autumn > winter, with the spatial WEON distribution of northern > southern > central. 2 The humic degree of Erhai sediment WEON was relatively high and mostly composed of fulvic acid, which mainly contained UV-like humic-like fluorescence peak A and high-excited tryptophan fluorescence peak B. This indicated that it was mainly affected by terrestrial input and microbial activity. 3 There were two fluorescent components(C1, C2) in the sediments and other sources of Erhai Lake. The component C1 was the endogenous visible ultraviolet peak formed by biodegradation, while the component C2 was the tryptophan peak. The bioavailability of wet deposition samples was comparatively high, greatly impacting Erhai Lake in heavy rainfall. The DON bioavailability in the inflow river was the lowest, which was prone to be accumulated in sediments. 4The DON component C1 and C2 in overlying water had significant negative correlation with Erhai sediment WEON contents(r=-0.79, P<0.01;r=-0.944, P<0.01). This suggested that the overlying water DON components could indirectly reflect the sediment WEON content of Erhai Lake, namely the higher the fluorescence components C1 and C2 in overlying water DON were, the lower the sediment WEON content was.

Molecular characterization of lake sediment WEON by Fourier transform ion cyclotron resonance mass spectrometry and its environmental implications

The compositional properties of water-extractable organic nitrogen (WEON) affect its behavior in lake ecosystems. This work is the first comprehensive study using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for the characterization of the molecular composition of WEON in lake sediment. In sediments of Erhai Lake in China, this study found complex WEON species, with N-containing compounds in the northern, central, and southern regions contributing 34.47%, 42.44%, and 40.6%, respectively, of total compounds. Additionally, a van Krevelen diagram revealed that lignin components were dominant in sediment WEON structures (68% of the total), suggesting terrestrial sources. Furthermore, this study applied ESI-FT-ICR-MS to the examination of the environmental processes of lake sediment WEON on a molecular level. The results indicated that sediment depth impacted WEON composition and geochemical processes. Compared with other ecosystems, the double bond equivalent (DBE) value was apparently lower in Erhai sediment, indicating the presence of relatively fewer and smaller aromatic compounds. In addition, the presence of a large number of N-containing species and abundant oxidized nitrogen functional compounds that were likely to biodegrade may have further increased the potential releasing risk of WEON from Erhai sediment under certain environmental conditions.

Spatial distribution, contamination and ecological risk assessment of heavy metals in surface sediments of Erhai Lake, a large eutrophic plateau lake in southwest China

The concentrations of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) and major metals (Al, Fe and Ti) in 42 surface sediment (0–2cm) samples from Erhai Lake, a large eutrophic plateau lake in southwest China, were analyzed. The heavy metal contamination was studied by comparing the multivariate statistical analysis and enrichment factor (EF) results, and the potential eco-risks were comparatively discussed by combining the sediment quality guidelines (SQGs), potential ecological risk index (Er and RI) and EF indices. The heavy metal concentrations displayed obvious spatial diversity in the surface sediments due to human contamination and variations in sediment texture, such as grain size and organic matter content. Principal component analysis (PCA) indicates that Cr, Cu and Ni were mainly lithogenic in origin and that the As, Cd, Hg, Pb and Zn levels were influenced by anthropogenic contamination. The EFs show that Cu, in addition to As, Cd, Hg, Pb and Zn, was also influenced by anthropogenic contamination. The contamination levels of the metals were zero to minor for Cu, Pb and Zn and moderate to significant for As, Cd and Hg on a whole lake basis. The different origins assigned to Cu by the PCA and EF results suggest that the PCA is less effective at differentiating pollutants when the pollution level is low. Anthropogenic As in the surface sediments was derived primarily from agricultural sources, and the other anthropogenic metals were mainly from atmospheric deposition and secondarily from industrial discharges. The mean concentrations of As and Cd are above the threshold effect concentrations (TECs) of the SQGs, suggesting adverse effects of the metals are likely to occur, which is in agreement with the Er assessment. The mean concentration of Hg is lower than the TEC; however, it may also pose adverse effects to the organisms because of its high contamination level (mean EF=6.7) and toxicity, which is supported by the Er value. The RI values (average 431) indicate that the heavy metals may pose very high eco-risks, with higher contributions from As, Cd and Hg. Generally, As, Cd and Hg are suggested to be the most concerning metals with respect to environmental monitoring and management in Erhai Lake due to their high contamination levels and potential eco-risks.

Sources appointment and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in sediments of Erhai Lake, a low-latitude and high-altitude lake in southwest China.

Sixteen polycyclic aromatic hydrocarbons (PAHs) were analyzed from the surficial sediments in Erhai Lake, a plateau lake in China. The results showed that except for acenaphthylene (Ace) Ace and Dibenz(a,h)anthracene (DBA), the central region contained individual PAHs at concentrations lower than those in other lake regions. Total concentration of the PAHs (ΣPAHs) in the sediments from Erhai Lake ranged from 32.42 to 558.53 mg/kg with a mean value of 256.70 mg/kg. The maximum value of ΣPAHs was observed in the north region of the lake and more than 10-fold higher than the minimum values. Moreover, high molecular weight (HMW) PAHs, especially 5-ring PAHs, accounted for higher ratios up to 76 % relative to other PAHs compound in almost all sampling sites. Molecular diagnostic ratios including anthtacene (Ant)/(Ant + phenanthrene (Phe)), fluoranthene (Flt)/(Flt + pyrene (Pyr)), benz(a)anthracene (BaA)/(BaA + chrysene (Chr)), and indeno(1,2,3-cd)pyrene (IPY)/(IPY + benz(g,h,i)perylene (BPE)) were recorded at all sampling sites and indicated that the origin of PAHs in Erhai Lake was predominately pyrolytic. Furthermore, principal component analysis with component dominating by HMW PAHs showed that combustion origins were the primary contamination sources of PAHs in the sediments of Erhai Lake. Finally, ecological risk assessment indicated that the sediments from Erhai Lake are exposed to potential low risk for ΣPAHs, and the ecological risk decreases in the order of northern region > southern region > central region.

Historical accumulation and environmental risk of nitrogen and phosphorus in sediments of Erhai Lake, Southwest China

The release of endogenous nutrients from sediments significantly affects water quality and accelerates eutrophication. In general, lakes from the Yungui Plateau of China are characterized by high sediment nutrient contents and relatively good water quality. Thus, the risk of nutrient release from sediments may be enhanced under certain environmental conditions, and this enhanced risk would become a general concern during eutrophication. Knowledge about historical nutrient accumulation and effect of environmental parameters on nutrient dynamics at the sediment–water interface in the lakes from this region is important to understand the eutrophication processes for these lakes. Hence, this study reconstructs the historical accumulation of nutrient and the effects of environmental parameters on possible release risk of nutrient at the sediment interface for Erhai Lake in the Yungui Plateau region. This study also analyzes historical changes in environmental conditions to predict the future release of nutrient from sediment. In the past decades, the burial fluxes (BFs) of nitrogen (N) in the sediments have continuously increased, whereas those of phosphorus (P) have not or only slightly increased, except in highly polluted areas. These situations may be attributed to the long-term fertilization practices of farmers in the watershed, where the application of N fertilizers is much higher than that of P fertilizers. The mentioned phenomena can also be ascribed to the different biogeochemical behaviors of N and P. Nutrient pollution started in the 1970s and worsened from the 1990s. Before the 1970s, nutrients were relatively low and stable. Thereafter, N in the entire area and P in seriously polluted areas (northern area) dramatically increased because of natural and anthropogenic processes, such as excessive artificial N and P fertilization. After the early 1990s, the BFs of nutrients were steady but high because of the degradation of aquatic vegetation and the implementation of pollution control policies. The burial efficiencies (BEs) of TN range between 44% and 85%, with a mean value of 71%. Combined with the high increase rate of BFs during the past decade, this relative low BE indicates that the release of sediment N into overlying water has increased yearly. The BEs of TP range between 98% and 102%, with a mean value of 99%, and the increase rate of historical BFs is small. This result suggests that the sediment generally serves as a sink for P. In addition, the diffusion fluxes of nutrients is an important factor because their forms and environmental conditions (dissolved oxygen (DO), pH, etc.) influence water quality. However, the risk of nutrient release from sediment source might increase if these environmental conditions change (i.e., decreased DO and increased pH).

Composition, source characteristic and indication of eutrophication of dissolved organic matter in the sediments of Erhai Lake

Composition and source characteristics of dissolved organic matter (DOM) in the surface sediments of Erhai Lake were studied by using fluorescence spectroscopy and UV–Vis absorbance. Moreover, the influence factors and the indication significance for eutrophication are also discussed. The results are as follows: (1) The DOC content of Erhai Lake sediments ranges from 0.17 to 0.77 g kg−1, which is higher in dry season than that in wet season. Its DOC content of the sediment from the northern part is higher than that from the southern, and that is the smallest in the central. Moreover, DOM in Erhai Lake sediments comprise of protein- and humic-like substances. The average contents of protein-, fulvic acid-like substances and soluble microbial byproduct-like materials in the wet season are higher than those in the dry season by 25.92, 11.82 and 2.96 %, respectively; while the content of humic-like substance in the wet season is lower than that in the dry season by 6.94 %. As to the spatial distribution, the contents of protein- and fulvic acid-like substances are the highest in the central of Erhai Lake sediments, and that of the humic-like substance is the highest in the southern part. In addition, the humification degree of DOM in the dry season is higher than that in the wet season. (2) The DOM in Erhai Lake sediments mainly originated from terrestrial sources, of which the terrestrial pollutant has a main impact in the dry season, and the terrestrial pollutant input and biogenetic derivation play an equally important part in the wet season. Terrestrial pollutant and aquatic plants are the important factors that influence the DOM composition of Erhai Lake sediments. (3) The characteristic parameter (P(III+V,n)/P(I+II,n)) (the content ratio of humic-like substance to protein-like substances) of the DOM composition of Erhai Lake sediments is positively correlated with the contents of the different nitrogen (N) forms in the sediments (R2 = 0.68–0.83, P < 0.01). The contents of N forms in sediments and its source characteristic can be reflected by the P(III+V,n)/P(I+II,n) value. So the P(III+V,n)/P(I+II,n) value can be taken as the indirect indicator of the contents of N forms in sediments. Moreover, the composition characteristic of DOM in sediments can reflect the contents of N forms to some extent, that is, the risk of N release from Erhai Lake sediments can be indicated to some extent.

Distribution and Forms of Phosphorus in the Buffer Zone Sediments of Erhai Lake

Spatial distribution of phosphorus in the buffer zone sediments of 16 rivers around Erhai Lake was investigated in July 2013 and different rivers are classified by hierarchical cluster. The average contents of TP, IP, Ca-P and Fe/Al-P were 822.18mg/kg, 602.42mg/kg, 396.79mg/kg and 150.64mg/kg. IP is the dominant mineral form in surface sediments. The order of the average contents of TP and IP conjects to be: West&gt;South&gt;North, West&gt;North&gt;South, respectively. The spatial distribution of TP, Ca-P and Fe/Al-P in the sediments shows a significant positive correlation with that of IP. All 16 investigated rivers are divided into five types according to the hierarchical cluster analysis: Shuangyuanxi River is one type, Zhonghexi River and Mocanxi River are one type, Boluojiang River and Baihexi River are one type, Yangxi River is one type and the other rivers are one type.

Identification of pyrite using 57Fe Mössbauer spectroscopy in core sediments from Erhai Lake, SW China combined with a series of acidic pre-treatments

A method has been developed for analyzing pyrite quantitatively in the sediments of Erhai Lake in southwest China using 57 Fe Mossbauer spectroscopy combined with a series of acidic pre -treatment s. Following a washing with an alkaline solution (0.1N Na OH), t he sediment samples were successively treated using HCl, HF, and then HCl (65 °C). The residue s thus prepared w ere analyzed for pyrite using 57 Fe Mossbauer spectrometry. The presence of pyrite was also confirmed in the acidic residues of the sediment s using sulfur K -edge X -ray absorption near edge structure . This method can be used to measure pyrite in aquatic sediments, especially when the con cent ration of pyrite is very low and the particles of pyrite are small or the crystallinity is low, and even in amorphous status . In addition, v ertical variation s of pyrite cont ent s are positively correlat ed with organic matter and negative ly correlat ed with hematite, superfine paramagnetic ferric iron and sedimen ta tion rate in the cored sediment from the Erhai L ake . All these geochemical indicators may also reflect environmental change s in sedimenta ry conditions and diagenesis.