Linear alkylbenzene sulfonate (LAS) in water of Lake Dianchi--spatial and seasonal variation, and kinetics of biodegradation

Growth and physiological responses of submerged macrophytes to linear alkylbenzene sulfonate (LAS)

The potential toxic effects of linear alkylbenzene sulfonate (LAS), widely used in commercial detergents and cleaners, on submerged macrophytes remain unclear. We conducted a two-week exposure experiment to investigate LAS toxicity on five submerged macrophytes (four native and one exotic), focusing on their growth and physiological responses. The results showed that lower concentrations of LAS (< 5 mg/L) slightly stimulated the growth of submerged macrophytes, while higher doses inhibited it. Increasing LAS concentration resulted in decreased chlorophyll content, increased MDA content and POD activity, and initially increased SOD and CAT activities before declining. Moreover, Elodea nuttallii required a higher effective concentration for growth compared to native macrophytes. These findings suggest that different species of submerged macrophytes exhibited specific responses to LAS, with high doses (exceeding 5 ∼ 10 mg/L) inhibited plant growth and physiology. However, LAS may promote the dominance of surfactant-tolerant exotic submerged macrophytes in polluted aquatic environments.

Metabarcoding of zooplankton communities of Dianchi Lake based on the mitochondrial cytochrome oxidase subunit 1 gene

Freshwater lakes as an essential component of the ecosystem, provide ecological resources in addition to economic source for humans. Under recent climate change scenario, preserving the biodiversity of freshwater ecosystems is crucial. This study aimed to characterize the diversity of zooplankton communities in Dianchi Lake, located in Kunming Municipality, Yunnan Province, China, using Illumina high-throughput sequencing of the cytochrome oxidase subunit 1 (COI) gene marker. A total of 18 water samples were collected including 16 from the outer sea area of Dianchi Lake: 4 from the east (E1-4), 4 from the west (W1-4), 4 from the south (S1-4), and 4 from the north (N1-4), and: 2 from the Caohai area (C1-2) as research sites. All environmental parameters including pH, ammonium (NH4+), total nitrogen (TN), total phosphorus (TP), chlorophyll a content (CHLA) were found to be insignificant (p > 0.05), except for chemical oxygen demand (COD) and transparency (T), which were found to be significant (p < 0.05). Alpha diversity indices including ACE, Chao1, Shannon, and Simpson showed non-significant differences (p > 0.05), indicating no variation in the richness of zooplankton communities at different locations of Dianchi Lake. However, principal coordinate analysis (PCoA) showed that most of the samples from East, West, and South groups were close to each other, showing more similarities among them, while Caohai and North group samples were distant from each other, showing more differences with other groups. Rotifera, Arthropoda, and Chordata were the top three phyla, while Keratella, Macrothrix, and Brachionus were the dominant genera. Mantel test analysis showed that COD and transparency were important environmental factors that shaped the Rotifera community structure of Dianchi Lake. In conclusion, this study provides insights on conserving the diversity of zooplankton communities in Dianchi Lake, especially by controlling COD and maintaining water transparency, in order to preserve its ecological resources and economic significance.

Ecotoxicological impacts caused by high demand surfactants in Latin America and a technological and innovative perspective for their substitution

Nowadays, water pollution represents a great concern due to population growth, industrialization, and urbanization. Every day hazardous chemical products for humans and aquatic organisms are disposed of arbitrarily from homes and industries. Even though detergents are considered an essential market, there is evidence of environmental impacts caused by surfactants like nonylphenol ethoxylate (NPE) and linear alkylbenzene sulfonates (LAS). Regulations about maximum allowable concentrations in sewage, surface water, and drinking water are scarce or null, mostly in developing countries like Latin American countries. Therefore, this review explores these two common toxic surfactants (NPE and LAS) and proposes a technological, innovative, and ecological perspective on detergents. Also, it establishes a starting point for industries to minimize adverse effects on humans and environmental health caused by these compounds.

Effects of human-induced eutrophication on macroinvertebrate spatiotemporal dynamics in Lake Dianchi, a large shallow plateau lake in China

The Yungui Plateau lakes, which are characterized by a highly endemic biodiversity, have been suffering severely from anthropogenic intervention in the recent decades. Studies on the response of these biodiversity to human-mediated effects are still limited. Here, we selected the typical Lake Dianchi to investigate the correlation between macroinvertebrate spatiotemporal dynamics and human-induced eutrophication across a 2-year span (2009-2010). A total of 26 taxa were recorded, and the assemblage pattern of the macroinvertebrate community was mainly controlled by the spatiotemporal (region, season, and year) density fluctuations of some pollution-tolerant species (Limnodrilus hoffmeisteri, Tubifex tubifex, Branchiura sowerbyi, and Chironomus plumosus). Taxon richness, total density, biomass, and the abundance of Oligochaeta and Chironomidae decreased from the north to the south of the lake but were much higher in 2009 than in 2010. Moreover, the high densities of total assemblages and oligochaete occurred during spring and/or autumn, whereas that of chironomids was only high during summer. The contributions of important factors varied in different seasons, but the community variations were mainly shaped by eutrophication-related factors (e.g., Chla, N, and P). Variance partitioning analyses showed that aquatic factors were able to explain more community variations than sediment (6.9-36.6 vs. 5.3-14.7%) across seasons, but their interactive effects were negligible. The results of this study will be beneficial for restoring and managing hypereutrophic lakes in the Yungui Plateau and imply the necessity of long-term monitoring in bioassessment projects involving intensively disturbed lakes.

Aquatic toxicity and loss of linear alkylbenzenesulfonates alone and in a neonicotinoid insecticide formulation in surface water

Substance losses of linear alkylbenzene sulfonates (LASs) in a neat surfactant mixture, in an insecticide formulation Mospilan 20 SG, and in solutions with different neonicotinoid active ingredients (AIs) was studied in distilled water and in surface water samples originated from River Danube. Analytical measurements were performed both by HPLC-UV and commercial ELISA methods. Loss rates of LASs were found different in these aqueous matrices, with decomposition rates higher for the neat surfactant mixture than for Mospilan 20 SG (nearly 2- and 9-fold in distilled water and in surface water from River Danube, respectively). Half-lives determined in surface water from River Danube were shown to be affected by the presence of neonicotinoid AIs thiacloprid > imidacloprid > acetamiprid (ACE), while clothianidin and thiamethoxam did not affect LAS decomposition. Aquatic toxicity of Mospilan 20 SG, along with that of its AI ACE and co-formulant LAS, as well as the mixture of ACE and LAS was also investigated in the 48-h acute immobilisation assay on the water flea (Daphnia magna) aquatic indicator organism. LAS appeared to be significantly (8-fold) more toxic in the D. magna test than ACE, and the toxicity of the formulated insecticide was found to be 1.3 and 19.6 times higher than explained by its AI and LAS content, respectively, indicating synergistic toxicity. The strongest synergy between ACE and LASs was observed, when the neat forms of the two substances were applied in combination at concentrations equivalent to those in Mospilan 20 SG.

Identification of surfactants and its correlation with physicochemical parameters at the confluence region of Vembanad Lake in India

The present study describes the monitoring of some of the major classes of surfactants in water. The separation, identification, and the quantitative estimation of the compounds were achieved using LC-Q-ToF-MS. The analyses revealed the presence of variety of surfactants including linear alkylbenzene sulfonate (LAS), alcohol ethoxysulfates (AES), and alcohol ethoxylates (AE). Further, emphasis was given to AES as they are one of the most produced and consumed surfactants in the world. And as far as India is concerned, the present study is one of the most significant attempt regarding the identification and quantification of AES. The data obtained during the analysis revealed that the average concentration of AES C12Ex varied from 0.7 to 13.6 μg L^-1 while that of C14Ex ranged between 1.3 and 10.4 μg L^-1. The risk assessment revealed that higher chain AES are capable of posing medium level risk to the aquatic compartment. In addition, the study also included the physicochemical analysis of water from the selected area. Water was found to be acidic in nature and the salinity, TDS, and EC values were found to be high during the pre-monsoon season. The order of the levels of anionic constituents was of Cl^->SO₄^2-SO₄^2->F^->NO₃^2- ≅ PO₄^2- while that of cations were Na⁺ > Mg²⁺ > K⁺ > Ca²⁺. Results of correlation analysis showed that statistically negative correlation exists between AES homologs and pH while slight positive correlations were found between AES and other parameters including TDS and EC. The suitability of this water for domestic and agricultural purposes has been examined on the ground of basic quality indices such as the water quality index (WQI) and sodium adsorption ratio (SAR). The WQI measurements also revealed that the water quality of the region falls under the "very poor" category especially during the pre-monsoon season. The study could explore the cumulative share of these canals in the quality impairment of the receiving Vembanad Lake.

The relative risk and its distribution of endocrine disrupting chemicals, pharmaceuticals and personal care products to freshwater organisms in the Bohai Rim, China

In this study, the risks to aquatic organisms posed by 12 commonly detected pharmaceuticals and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs) that are extensively used in Bohai coastal region of China were examined. These were linear alkylbenzene sulfonate (LAS), nonylphenol (NP), diethylhexyl phthalate (DEHP), norfloxacin (NOR), sulfamethoxazole (SMX), erythromycin (ERY), bisphenol A (BPA), ofloxacin (OFL), carbamazepine (CBZ), naproxen (NPX), atenolol (ATL) and metoprolol (MET). Their relative risk was ranked based on the proximity between the medians of the reported effect concentrations and measured river or lake water concentrations. The surfactants (LAS) and endocrine disrupting chemicals NP (a breakdown product of the surfactant nonylphenol polyethoxylate) and DEHP (a plasticizer) were identified as posing the greatest risk from this range of chemicals. LAS had a hundred-fold higher risk than any of the pharmaceuticals. The highest risk ranked pharmaceuticals were all antibiotics. Zinc (Zn) and mercury (Hg) were added to the comparison as representative heavy metals. Zn posed a risk higher than all the organics. The risk posed by Hg was less than the surfactants but greater than the selected pharmaceuticals. Whereas LAS and DEHP could cause harmful effects to all the wildlife groups, NP and BPA posed the greatest risk to fish. Antibiotics showed the highest risk to algae. Spatial and temporal distributions of PPCPs and EDCs were conducted for risk identification, source analysis and seasonal change exploration. Municipal sewage effluent linked to urban areas was considered to be the major source of pharmaceuticals. With regard to seasonal influence the risk posed by LAS to the aquatic organisms was significantly affected by wet and dry seasonal change. The dilution effects were the common feature of LAS and ERY risks. The difference in LAS and ERY risk patterns along the rivers was mainly affected by the elimination process.

Comparison and Interpretation of Taxonomical Structure of Bacterial Communities in Two Types of Lakes on Yun-Gui plateau of China

Bacterial communities from freshwater lakes are shaped by various factors such as nutrients, pH value, temperature, etc. Their compositions and relative abundances would undergo changes to adapt the changing environments, and in turn could affect the environments of freshwater lakes. Analyses of the freshwater lake’s bacterial communities under different environments would be of pivotal importance to monitor the condition of waterbody. In this study, we have collected freshwater samples from two lakes on Yun-Gui plateau of China, Lake Dianchi and Lake Haixihai, and analyzed the bacterial community structures from these samples based on 16S rRNA sequencing. Results have shown that: Firstly, the bacterial community of these samples have very different taxonomical structures, not only between two lakes but also among the intra-groups for samples collected from Dianchi. Secondly, the differences between samples from two lakes are highly associated with the chemical-geographical properties of the two lakes. Thirdly, for samples of Dianchi and Haixihai, analytical results of physicochemical, taxonomical structure and relative abundance of community revealed that extreme physicochemical factors caused by human activities have strongly affected the bacterial ecosystem in Dianchi. These results have clearly indicated the importance of combining biological profiling and chemical-geographical properties for monitoring Chinese plateau freshwater bacterial ecosystem, which could provide clues for Chinese freshwater ecosystem remediation on plateau.

Effects of engineered application of Eichhornia crassipes on the benthic macroinvertebrate diversity in Lake Dianchi, an ultra-eutrophic lake in China

An ecological engineering project with confined growth of 1.5 km(2) of Eichhornia crassipes was implemented to remove pollutants in Lake Dianchi. To assess the ecological effects of this project on benthic macroinvertebrate assemblages, a 1-year investigation at the areas inside and outside E. crassipes mats was conducted from May 2013 to May 2014. All the 10 sampling sites in the areas were grouped into two statistically significant clusters mainly corresponding to inside and outside E. crassipes mat areas (EMAs), by clustering analysis. E. crassipes reduced the densities of pollution indicator taxa (e.g., Oligochaeta and Chironomidae larvae); thus, the total densities of benthic macroinvertebrates at the area inside EMAs (mean 328.2 ind./m(2)) were slightly lower than that at the area outside EMAs (mean 505.6 ind./m(2)). Four functional feeding groups including 38 species of benthic macroinvertebrates were collected at the area inside EMAs, while only three functional feeding groups containing 17 species were collected at the area outside EMAs. The biodiversity indices (Shannon-Weiner, Margalef, Simpson, and Peilou indices) and K-dominance curves also showed higher diversity of benthic macroinvertebrates at the area inside EMAs than at the area outside EMAs. These results suggested that a certain scale of engineering application of E. crassipes was beneficial to benthic macroinvertebrate communities in the ultra-eutrophic Lake Dianchi and it could be used as a pioneer species in ultra-eutrophic lake for pollutant removal.

Evaluation of the potential of anoxic biodegradation of intracellular and dissolved microcystins in lake sediments

The kinetics of the anoxic biodegradation of intracellular and dissolved microcystin (MCs) and the effects of soluble organic materials on the process were investigated via a series of well-controlled microcosm experiments. The potential for the removal of intracellular and dissolved MCs from lake sediment differed. The dissolved MCs could be degraded to below the detection limit at 20 °C within one to 3 days after a lag phase of 2-6 days under anoxic conditions. The levels of intracellular MCs were also significantly reduced in the sun-dried cyanobacterial samples but not rapidly reduced in fresh cyanobacterial samples until the cells were ruptured. The addition of soluble organic matter enhanced the anoxic biodegradation of MCs. These results indicate that the application of anoxic biodegradation via lake sediments is an effective method to remove dissolved and intracellular MCs and that this process exhibits significant bioremediation potential for the further treatment of cyanobacteria.

Effects of linear alkylbenzene sulfonate on the growth and toxin production of Microcystis aeruginosa isolated from Lake Dianchi

The exogenous organic pollutant linear alkylbenzene sulfonate (LAS) pollution and Microcystis bloom are two common phenomena in eutrophic lakes, but the effects of LAS alone on Microcystis remain unclear. In the present study, we investigated the effects of LAS on the growth, photochemical efficiency, and microcystin production of Microcystis aeruginosa in the laboratory. Results showed that low LAS (≤10 mg/L) concentrations improved the growth of M. aeruginosa (12 days of exposure). High LAS (20 mg/L) concentrations inhibited the growth of M. aeruginosa on the first 8 days of exposure; afterward, growth progressed. After 12 days of exposure, the concentrations of chlorophyll a in algal cells were not significantly affected by any of LAS concentrations (0.05 to 20 mg/L) in the present study; by contrast, carotenoid and protein concentrations were significantly inhibited when LAS concentrations reached as high as 20 mg/L. After 6 and 12 days of exposure, low LAS (≤10 mg/L) concentrations enhanced the maximal photochemical efficiency (Fv/Fm) and the maximal electron transport rate (ETRmax) of M. aeruginosa. Furthermore, LAS increased the microcystin production of M. aeruginosa. Extracellular and intracellular microcystin contents were significantly increased after M. aeruginosa was exposed to high LAS concentrations. Our results indicated that LAS in eutrophic lakes may increase the risk of Microcystis bloom and microcystin production.

Large-scale utilization of water hyacinth for nutrient removal in Lake Dianchi in China: the effects on the water quality, macrozoobenthos and zooplankton

An ecological engineering project using water hyacinth for nutrient removal was performed in Baishan Bay of a large shallow eutrophic lake, Lake Dianchi in China. In the present study, a systematic survey of water quality, macrozoobenthos and zooplankton inside (IWH), around (AWH) and far away (FWH) water hyacinth mats was conducted in Baishan Bay from August to October 2010. The results showed that the water quality significantly improved at AWH area. Concentrations of nitrogen and phosphorus were lower and transparency was higher at AWH area than those in IWH and FWH areas. Total densities, dominant species densities, and biodiversity indexes of macrozoobenthos and cladocerans as well as copepods did not differ (P>0.05) among each other in all three areas. It was significantly (P<0.05) different for those of rotifers at IWH area compared to those in AWH and FWH areas. The results might suggest a tremendous potential for the utilization of water hyacinth in the eutrophic lake like Lake Dianchi for nutrients removal.

Responses and toxin bioaccumulation in duckweed (Lemna minor) under microcystin-LR, linear alkybenzene sulfonate and their joint stress

Microcystin-LR (MCLR) and linear alkylbenzene sulfonate (LAS) are commonly found in eutrophic lakes due to toxic cyanobacterial blooms and exogenous organic compounds pollution. However, the ecotoxicological risk of their combination in the aquatic environment is unknown. This study investigated the effects of MCLR, LAS and their mixture on duckweed (Lemna minor) growth and physiological responses. MCLR accumulation in duckweed, with or without LAS, was also examined. Growth of duckweed and chlorophyll-a contents were significantly reduced after 8d exposure to high concentrations of MCLR (≥ 3 μg/ml), LAS (≥ 20 μg/ml) and their mixture (≥ 3+10 μg/ml). After 2d of exposure, superoxide dismutase activity and glutathione content in duckweed increased with increasing concentrations of MCLR, LAS and their mixture, with a significant difference observable after 8d of exposure. When MCLR and LAS concentrations were lower (≤ 0.1+1 μg/ml), the interaction of them is synergistic, but when the concentrations were higher, the synergy was weak. MC accumulation was much higher at 2d than at 8d when duckweed was exposed to lower concentrations of MCLR (≤ 3 μg/ml) or MCLR-LAS (≤ 3+10 μg/ml). Furthermore, LAS significantly enhanced the accumulation of MCLR in duckweed, even with LAS concentrations as low as 0.3 μg/ml (environmental concentration), indicating that greater negative ecological risks and higher MCLR phytoremediation potentials of duckweed might occur in MCLR-LAS-concomitant water.

Bioaccumulation of microcystins in two freshwater gastropods from a cyanobacteria-bloom plateau lake, Lake Dianchi

To investigate the bioaccumulation patterns of microcystins (MCs) in organs of two gastropods, samples were collected in Lake Dianchi monthly from May to October, 2008, when cyanobacteria typically bloom. The average MCs concentrations for Radix swinhoei (pulmonate) and Margarya melanioides (prosobranch) tended to be similar for the different organs: the highest values in the hepatopancreas (9.33 by 3.74 μg/g DW), followed by digestive tracts (1.66 by 3.03 μg/g DW), gonads (0.45 by 1.34 μg/g DW) and muscles (0.22 by 0.40 μg/g DW). Pulmonate had higher value than prosobranch because of the stronger bioaccumulation ability in hepatopancreas. The levels in organs of R. swinhoei were correlated with environmentally dissolved MCs, but influenced by intracellular MCs for M. melanioides. The estimated MCs concentrations in edible parts of M. melanioides were beyond the WHO's provisional tolerable daily intake (0.04 μg/kg), suggesting the risk of consumption of M. melanioides from the lake.