The Analysis of the Seasonal,Spatial, and Compositional Distribution of Humic Substances in a Subtropical Shallow Lake

The spatial and temporal distribution of humic substances in aquatic ecosystems can have important effects on ecosystem productivity, negatively impacting primary productivity while positively impacting secondary productivity. In the present investigation, a large shallow lake ecosystem was studied to determine the spatial and seasonal variation of the composition and concentration of humic substances. Concentrations of total dissolved organic matter, humic acid, and fulvic acid were found to display significant spatial distributions (1.3…13.5 mg/L, DOM; 0.1…5.4 mg/L, HA). The distribution is described by using mapping techniques and the analysis of the spatial distribution of the lake. An analysis of the seasonal variations also indicated the dependence of the occurrence of these compounds on meteorological and hydrological conditions. To identify the potential sources of these organic materials, an analysis was made of the ratio of humic and fulvic acid fractions and total DOM. It was found that areas of high DOM concentration coincided with the areas of highest HA percentage of total DOM. Furthermore using the ratio of the normalised concentrations of HA, FA, and residual DOM (< 5000 g/mol) it was found that areas dominated by each are spatially distinct. This confirms the hypothesis that in these shallow lakes, photodegradation and bacterioplankton activity will create a residence time dependent zonation of each component of the total DOM.     

The Effects of Nutrients on Natural Organic Matter (NOM) Removal in Biological Activated Carbon (BAC) Filtration

Effective biodegradation of organic compounds is one of the major objectives while optimizing biological drinking water treatment processes. Enhancing the biological activated carbon (BAC) filter performance with nutrient addition was studied using chemically pre-treated and ozonated lake water. Three parallel pilot-scale biofilters were operated: one with phosphorus addition, one with a mixture of inorganic nutrients addition, and one as a reference. The addition of nutrients had no statistically significant influence on the natural organic matter (NOM) removal when monitored by total organic carbon (TOC), UV absorbance, and assimilable organic carbon (AOC). However, the addition of nutrients significantly increased the heterotrophic plate count (HPC) bacteria of the filter effluent, while the adenosine triphosphate (ATP) analysis of the attached bacteria did not show any increase in BAC filters. It seemed that in BAC filters the bacterial growth was limited by phosphorus, but the increased bacteria could not attach themselves during the relatively short acclimatization period.     

Origin of Dissolved Organic Carbon Studied by UV‐vis Spectroscopy

Dissolved organic carbon (DOC) distributions in water from Lake Ipê, MS, Brazil, were investigated. The samplings were performed monthly (surface, 1 m depth, and bottom) from June 1999 to June 2000. Absorbance at 285 nm and DOC concentrations in mg dm^—3, p(DOC), were highly correlated for the three depths. 77% of the surface, 85% for 1 m and bottom samples presented a variation between 20 dm³ g^—1 cm^—1 and 50 dm³ g^—1 cm^—1 of A(285 nm)/p(DOC), that characterizes the dissolved organic matter in lake water as essentially fulvic. The ratio A(254 nm)/p(DOC) was also sensitive for fulvic matter, and an A(250 nm)/A(365 nm) = 4 ratio was characteristic of strongly colored waters. The ratios A(436 nm)/p(DOC) for the three depths also showed a significant correlation. The predominance of fulvic acid is explained by environmental characteristics such as the tropical climate, temperatures above 18 °C, and the lake environment. It was demonstrated that the variation in the water carbon content due to different compartments in the lake can be monitored by UV‐vis spectroscopy ratios.     

Fluorescence as a Tool for Tracing the Organic Contamination from Pulp Mill Effluents in Surface Waters

Three‐dimensional fluorescence spectra of water samples from an eucalyptus bleached kraft pulp mill and from a river, upstream and downstream of the discharge of the effluent, revealed the existence of a peak at δ_exc = 280 nm and δ_em = 340 nm Δδ = 60 nm), characteristic of effluentπs organic matter. Humic substances were isolated from the effluent by sequential adsorption onto resins XAD‐8 and XAD‐4 in series. Their synchronous fluorescence spectra with Δδ = 60 nm do also exhibit an intense signal at δ_exc = 280 nm (≈ 300 nm in the humic acid fraction). The peak is absent in the spectra of humic substances isolated from a non‐polluted site of the river, but it is clearly seen in the spectra of the humic substances from a site downstream of the discharge of the effluent. Synchronous fluorescence spectra (Δδ = 60 nm) of water samples from the river and its lagoon were recorded and revealed to be an easy and fast way of tracing the organic contamination from the effluent.     

太湖流域降雨和湖水酸根阴离子长期变化及其环境意义

为揭示太湖流域降雨和湖水酸根阴离子长期变化特征及环境意义,通过历史数据收集和采样分析,对太湖流域降雨和湖水中的SO₄^2-、NO₃^-变化特征和来源进行了研究.结果表明：自1990s以来太湖流域降雨中SO₄^2-呈显著下降趋势,年平均下降率为0.28 mg/（L·a）;NO₃^-浓度却呈显著上升趋势,年平均增长率为0.05 mg/（L·a）,降雨中氮污染呈现加重的趋势.与之相反,湖水中SO₄^2-呈显著上升趋势,年平均增长率为1.24 mg/（L·a）;NO₃^-浓度却呈显著下降趋势,年平均下降率为0.02 mg/（L·a）.30年以来,太湖水体SO₄^2-/NO₃^-比值不断升高,远高于降水SO₄^2-/NO₃^-比值.研究认为：流域SO₂排放引起的酸沉降是湖水SO₄^2-浓度增长的最重要原因,但氮氧化物排放并未引起湖水NO₃^-浓度升高,说明太湖流域对大气沉降的氮氧化物有滞留作用,而太湖水体是流域大气沉降硫酸盐的重要汇.综合治理太湖流域酸性物质排放对防止太湖水体酸化和治理富营养化都具有重要意义.     

The spatial distribution of sedimentary compounds and their environmental implications in surface sediments of Lake Khar Nuur (Mongolian Altai)

Lake sediments are valuable natural archives to reconstruct paleoclimate and paleoenvironmental changes which consist of inorganic and organic sediment compounds of allochthonous origin from the catchment and of autochthonous production in the lake. However, for robust paleo-reconstructions it is important to develop a better understanding about sedimentation processes, the origin of inorganic and organic sediment compounds and their distribution within the lake. In this context, modern process studies provide important insights, although environmental and anthropological changes can affect the spatial distribution of sediment compounds through time. Therefore, in this study the spatial distribution of grain size and geochemical proxies in 52 surface sediment samples from Lake Khar Nuur, a small high-altitude lake in the Mongolian Altai with a small and anthropogenically used hydrological catchment, is investigated. The results show a distinct sediment focussing in the two deep basins of the lake, which therefore act as accumulation zones. In those accumulation zones, total organic carbon (TOC), total nitrogen (N) and their isotopic composition (δ¹³C_TOC, δ¹⁵N) as well as n-alkanes indicate that organic sediment compounds are a mixture of both allochthonous and autochthonous origin. While the recent catchment vegetation consists of grasses/herbs and the shrub Betula nana (L.) with distinct differences in their n-alkane homologue patterns, those differences are not reflected in the sediment surface samples which rather indicates that grass-derived n-alkanes become preferentially incorporated in the lake. Extensive anthropogenic activity such as grazing and housing in the southern part of the catchment causes soil erosion which is well reflected by high TOC, N and sulphur (S) contents and ¹⁵N depleted δ¹⁵N values at the central southern shore, i.e. increased allochthonous sediment input by anthropogenically-induced soil erosion. Overall, the surface sediments of Lake Khar Nuur origin from allochthonous and autochthonous sources and are focussed in the accumulation zones of the lake, while their distribution is both environmentally and anthropogenically driven.     

Carbon Budget and Molecular Structure of Natural Organic Matter in Bank Infiltrated Groundwater

Managed aquifer recharge (MAR) provides means to remove natural organic matter (NOM) from surface waters. Recent studies have explored the degree of NOM removal in groundwater. In this study, we further elaborate the NOM removal at a lakeside natural bank infiltration site that functions as a surrogate for MAR. Our objective was to quantify the carbon budget in the aquifer based on concentration measurements of dissolved (in)organic carbon, and the molecular changes in NOM using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). According to the carbon budget, only 25% of the dissolved carbon entering the aquifer was organic, and it predominantly originated from lake water. Of the inorganic majority, on average 40% was produced in the vadose zone above the groundwater table, 31% in the lake bank, 22% in the aquifer as a result of degrading organic matter of lake water, and 7% in the lake. Seasonal concentration variations suggested that the lake bank was the main carbon source in the summer, increasing the carbon concentration of infiltrating lake water, that is, 3.0 mg/L to 7.9 mg/L. FT-ICR MS results showed 4960 to 5330 individual compounds in lake and groundwater. NOM removal in the aquifer was selective: the relative abundance of oxygen-containing species decreased from 75 to 31%, while the relative abundance of sulfur-containing species increased from 15 to 57%. The average molecular weights of both species remained unchanged. The study highlighted the role of lake bank processes and sulfur-containing species in groundwater quality.     

Spectroscopic investigation of humic substances in a tropical lake during a complete hydrological cycle

Fluorescence and UV‐VIS techniques were employed for the investigation of natural organic matter (NOM) of a tropical lake. The relationships of absorbance/dissolved organic carbon (A/DOC), fluorescence intensity/dissolved organic carbon (FI/DOC), fluorescence ratio (FR), and peak wavelength with the highest intensity (PW) were used to distinguish the pedogenic or aquagenic origin of NOM. The values of FR, PW and A₂₈₅/DOC of high waters (HW) or flooded period samples and of low waters (LW) period samples of the dry season, except for September 2002, confirm the predominance of pedogenic material. The spectra of water were similar to the standard fulvic acid (FA), and the spectra of FA from the lake were similar to the nearby soils, indicative of pedogenic predominance. The results confirm that the dissolved NOM of Patos Lagoon – MS (Brazil), in all sampling periods, predominantly consisted of humic substances (FA) of pedogenic origin.     

A ∼300-year record of environmental changes in Lake Issyk-Kul,Central Asia,inferred from lipid biomarkers in sediments

We measured lipid biomarkers (n-alkanes [n-ALKs] and n-alkanoic acids [n-FAs]) and other components of organic matter (total organic carbon [TOC] and total nitrogen [TN]) in a sediment core from Lake Issyk-Kul, Central Asia, to infer environmental changes in and around the lake during the last ∼300 years. Stratigraphic shifts in lipid biomarkers, TOC and TN, indicate three distinct environmental stages in the lake over the past three centuries: (1) Stage I (1670s–1790s, 51–36 cm sediment depth) corresponds to a period of stable hydrology in the lake, reflected by relatively constant concentrations of n-ALKs and n-FAs and values of related indexes. The interval was a period of relatively low trophic state. Natural factors were the main controls on environmental changes in and around the lake. (2) Stage II (1800s–1970s, 35–15 cm sediment depth) was a period when human activities began to exert influence on the environment in and around the lake. Enhanced agricultural exploitation and greater regional rainfall resulted in delivery to the lake of more land-derived lipids. Logging activity around the lake altered the vegetation, as revealed by shifts in C₂₇/C₃₃ ratios and the average chain length (ACL₂₇₋₃₃). A significant decline in lake level caused by excessive water consumption impacted aquatic macrophytes, as revealed by a reduction in macrophyte indicators. Lower nutrient concentrations were inferred for this period. (3) Stage III (1980s–present, 14–0 cm sediment depth) corresponds to a period of accelerating eutrophication. Before year 2000, lake level declined steadily as a result of low rainfall (drought) and high evaporation, which exerted a strong influence on the lake condition. In addition, anthropogenic activities contributed to lake eutrophication. After 2000, the lake experienced a dramatic increase in trophic state, characterized by high algal productivity, as indicated by greater TN, short-chain n-ALKs and short-chain n-FAs. The change was probably caused by flourishing tourism around the lake. In summary, environmental changes in and around Lake Issyk-Kul during the past ∼300 years were originally driven largely by natural factors such as shifts in regional precipitation amount. Human activities (e.g. logging, agriculture, water extraction, and more recently, tourism) took on increasingly important roles during the last two centuries, affecting watershed vegetation, the lake primary producer community and lake trophic status. Changes recorded in the lake sediments over the last ∼300 years are in good agreement with historical records.     

Evapotranspiration is resilient in the face of land cover and climate change in a humid temperate catchment

In temperate humid catchments, evapotranspiration returns more than half of the annual precipitation to the atmosphere, thereby determining the balance available to recharge groundwaters and support stream flow and lake levels. Changes in evapotranspiration rates and, therefore, catchment hydrology could be driven by changes in land use or climate. Here, we examine the catchment water balance over the past 50 years for a catchment in southwest Michigan covered by cropland, grassland, forest, and wetlands. Over the study period, about 27% of the catchment has been abandoned from row‐crop agriculture to perennial vegetation and about 20% of the catchment has reverted to deciduous forest, and the climate has warmed by 1.14 °C. Despite these changes in land use, the precipitation and stream discharge, and by inference catchment‐scale evapotranspiration, have been stable over the study period. The remarkably stable rates of evapotranspirative water loss from the catchment across a period of significant land cover change suggest that rainfed annual crops and perennial vegetation do not differ greatly in evapotranspiration rates, and this is supported by measurements of evapotranspiration from various vegetation types based on soil water monitoring in the same catchment. Compensating changes in the other meteorological drivers of evaporative water demand besides air temperature—wind speed, atmospheric humidity, and net radiation—are also possible but cannot be evaluated due to insufficient local data across the 50‐year period. Regardless of the explanation, this study shows that the water balance of this landscape has been resilient in the face of both land cover and climate change over the past 50 years.     

Evaluation of lake restoration in Sweden

A large portion of the water resources in Sweden have been afflicted by acidification and eutrophication. Governmental grants have been allocated for external and internal restoration measures for nutrient reductions, and are at the moment given for liming operations in acidified lakes. Objective and results of the Swedish lake restoration programme during the last 20 years are discussed and evaluated. Presented at the International Conference on Lake Restoration in Zürich, 3–4 November 1986     

呼伦湖东露天矿剖面有机碳的总量及其稳定碳同位素和古环境演化

湖泊沉积物中有机碳的总量（TOC）取决于湖泊的初始生产力及有机质沉积后的保存能力,而有机碳的稳定同位素（δ~(13)C）值则反映了不同来源有机质的组成以及流域古植被状况。本文通过对内蒙呼伦湖东露天煤矿剖面TOC及δ~(13)C值的垂直分布的研究,结合剖面的沉积特征及孢粉、硅藻分析结果,讨论了呼伦湖地区末次冰期以来古气候古环境演化过程。结果表明有机碳的总量及其稳定碳同位素可作为分析古气候环境的一种有效的代用指标。     

近1800年来云南洱海流域气候变化与人类活动的湖泊沉积记录

对云南洱海湖泊岩芯沉积物进行了多环境指标（年代学、色素、硅藻、有机碳稳定同位素、磁化率、化学元素）的分析,建立了近１８００年来云南洱海流域气候与环境变化的序列,气候演化具有暖干、冷湿交替的组合呈些特征气候阶段如中世纪温暖期、小冰期气候特征在洱海源泊沉积记录中均有反映,洱海湖泊上沉积记录的气候暖干－冷湿交替变化规律,反映了西南委风影响下的气候演化特征,湖泊沉积记录中包含丰富的人类以的信息,磁化率,元     

Preparation and evaluation of polyaluminum chloride sulfate (PACS) as a coagulant to remove natural organic matter from water

A series of polyaluminum chloride sulfate (PACS) coagulants, which have different SO₄^2–/Al³⁺ and OH/Al (γ) mole ratio, has been successfully developed using AlCl₃·6H₂O, Al₂(SO₄)₃·18H₂O and Na₂CO₃ as raw materials. The coagulation performance of PACS for removing natural organic matter (NOM) from surface water was evaluated, and the effect of SO₄^2–/Al³⁺ mole ratio and γ value in coagulants PACS on DOC and UV₂₅₄ removal was determined. Furthermore, the influence of pH and dosage of the selected PACS with a SO₄^2–/Al³⁺ ratio of 0.0664 and a γ value of 2.0, which achieved the best coagulation performance for the removal of DOC and UV₂₅₄ of all PACS coagulants, on the removal of DOC and UV₂₅₄ and residual aluminum concentration in treated water was investigated. The results were compared with the ones of polyaluminum chloride (PAC) with γ value of 2.0. The experimental data show that the performance of PACS as a coagulant was highly dependent on SO₄^2–/Al³⁺ mole ratio and γ value. Both for the selected PACS and for PAC, the best DOC and UV₂₅₄ removal results were obtained in the range of pH from 5.0 to 8.2 and at the coagulation dose of 5.0 mg/L as Al. Under the optimum coagulation conditions, the selected PACS gave higher DOC and UV₂₅₄ removal efficiencies, and lower residual aluminum concentrations in the treated water than PAC. The maximum removal of DOC and UV₂₅₄ for PACS was approximately 88.0% and 93.0%, respectively. At the optimum coagulant dose and pH 6.5, the concentration of residual aluminum in treated water by both selected PACS and PAC can comply with the regulated limits. The major mechanisms of NOM removal by PACS and PAC coagulation involve complexation‐charge‐neutralization‐precipitation.     

Influence of IHSS Standard and Reference Materials on Copper and Mercury Toxicity to Vibrio fischeri

The reduction in light emission of the marine bacterium Vibrio fischeri used in the standard Microtox^® bioassay was measured for the metals copper and mercury. The concentration at which the light emission was reduced by 50% (EC₅₀) was determined to be (3.43 ± 0.83) μmol/L for Cu²⁺ and (0.66 ± 0.01) μmol/L for Hg²⁺. The reduction of the toxicity of these metals by humic and fulvic acids were studied using IHSS Standard and Reference Materials. Copper toxicity was reduced 17...20% by the soil and peat fulvic acids and 9...20% by the aquatic fulvic acids. While there appeared to be little difference in the reduction of Cu toxicity by fulvic acids from soils, peats, or aquatic systems, Hg toxicity was reduced 3.6...7.3% by the soils and peats, while aquatic fulvic acids reduced Hg toxicity 14...16%. Soil fulvic acids appear to have significantly less capacity to reduce Hg toxicity than Cu toxicity. Humic acids had much higher reductions of Cu toxicity (44...124%) compared to the fulvic acids, with little difference between aquatic and soil or peat humic acids, 44...124% and 67...100%, respectively. However, humic and fulvic acids, regardless of origin, had approximately the same effect on Hg toxicity with 3.5...16% reduction by fulvic acids and 8...20% reduction by humic acids. Unlike the fulvic acids, no clear trend was observed relative to origin of the humic acids. There was no correlation between percent reduction of Cu or Hg toxicity by the organic compounds and copper binding capacity (CuBC), C/N ratio, or carboxyl content of the materials. Examination of natural organic matter (NOM) isolated by reverse osmosis techniques from three water sources had reductions of both Cu and Hg toxicity that were most similar to the Suwannee River and Nordic fulvic acids.     

Präzipitation von Aluminium und Phosphat in Gewässern unter dem Einfluss von Versauerung

Precipitation of Aluminium and Phosphate Affected by Acidification Acidified waters often show elevated concentrations of Al (with up to 6 mg L^–1 being not unusual). A pH increase resulting e.g. from mixing with non‐acidified water or from biological activities may be linked with Al precipitation. Up to now, this phenomenon was described for acid mine drainages. This investigation focuses on a whitish precipitate naturally formed in a brook of an atmospherically acidified catchment in the Ore Mountains, Germany. Based on infrared spectra the precipitate was identified as an Al‐hydroxosulfate with crystal water. A simulation of natural conditions in the laboratory showed that Al precipitated only if sulfate or phosphate ions were added to the solution. In the case of sulfate being added, the infrared spectrum of the precipitate was similar to the natural precipitate. ²⁷Al NMR spectroscopy revealed tetrahedrally coordinated Al in some precipitates which evidences the participation of the tridecameric [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺ cation beside other polymeric Al cations. Precipitation experiments subjected to the given conditions showed that the phosphate elimination from solution with Al was much higher than with Fe. With Al and Fe added together, the P elimination rate was likewise high, and phosphate was bound onto Al in the precipitate. This was demonstrated by SEM‐EDX spectroscopy. Based on these results we present a possible reaction mechanism. The precipitation of Al together with P allows a significant retention of both elements in sediments because in contrast to Fe, Al immobilizes phosphate even under anoxic conditions.