Analytical Method Of Phenolic Endocrine Disrupting Chemicals And Their Pollution Characteristics In Dianchi Lake Catchment

Endocrine disrupting chemicals (EDCs) are defined as exogenous agents that interfere with the production, secretion, transportation, metabolism, binding, action, or elimination of natural hormones in the body. These compounds are responsible for the maintenance of homeostasis and the regulation of developmental processes. EDCs may disturb the function of endocrine system of human and wildlife and consequently cause adverse effects on development, reproduction and immune system of organism. Pollution characteristics of the widely used phenolic EDCs in aquatic environments have attracted a great deal of scientific and public attention. Because of the complexity of the environmental matrix, it is very difficult to monitor and analyze the trace phenolic EDCs in natural environment. Therefore, it is of crucial importance to develop an analytical method for the accurate determination of phenolic EDCs in the complex media.In consideration of the urgency and hysteresis of study on EDCs in Dianchi Lake, phenolic EDCs are selected as target compounds and their pollution characteristics in Dianchi Lake catchment are studied on the basis of the improved analysis method. Research areas have been extended to the whole Dianchi Lake catchment including the national water quality monitoring sections, eight sediment cores in Dianchi Lake, twenty-two rivers around Dianchi Lake, as well as eight sewage treatment plants (STPs) in the main urban area of Kunming City; research contents have been deepened to contamination level, distribution characteristic, seasonal distribution, historical trend, elimination, pollution load, migration and so on. This paper integratedly clarified the pollution characteristic of phenolic EDCs in Dianchi Lake catchment, for the purpose of providing more comprehensive fundamental data for risk assessment and contamination control of phenolic EDCs in aquatic environment.(1) An efficient and reliable method was improved for the analysis of six typical phenolic EDCs such as nonylphenol-diethoxylate (NP2EO), nonylphenol-mono-ethoxylate (NP1EO),4-nonylphenol (4-NP), bisphenol A (BPA),4-cumylphenol (4-CP) and4-tert-octylphenol (4-t-OP) in multiple environmental media (water, sediment, STPs influent, effluent and sludge). The proposed method was consisted of sample collection, microwave-assisted extraction (MAE), automated gel permeation chromatography (GPC), solid phase extraction (SPE), derivatization and gas chromatography-mass spectrometry (GC-MS) analysis. It provided a reliable technological approach to comprehensively study the pollution characteristic of phenolic EDCs in aquatic environment. The results showed that phenolic EDCs were derivatized with N, O-bis (trimethylsilyl)trifluoroacetamide (BSTFA) at70℃for50min; water samples (pH=4.5) were extracted by using Sep-Pak C-18cartridges, and the extracts were eluted by10mL of dichloromethane; sediment or sludge samples were extracted by using MAE with25mL of methanol at110℃for20min, respectively. The cleanup of extracts was carried out by GPC with cyclohexane/ethyl acetate (1:1, v/v) as mobile phase, and the target compounds were eluted in the fraction from7-14min retention time. The method achieved good repeatability and reproducibility with relative standard deviations lower than9.5%for all target EDCs in all the samples. The overall recoveries for spiked water and solid samples ranged from83.51to105.74%and74.30to105.04%, respecitively. The limits of detection ranged from0.10to2.30ng/L for water samples, and from0.15to2.90ng/g dry weight (dw) for sediment and sludge samples. The improved method was successfully applied to the analysis of phenolic EDCs in water and surface sediment and inflow samples collected from the Dianchi Lake and STPs, respectively. The developed method is a promising approach for the analysis of phenolic EDCs in environmental samples.(2) Pollution characteristics of the phenolic EDCs in water and surface sediment samples collected from Dianchi Lake were investigated. The results showed that the concentrations of the phenolic EDCs in water and surface sediment in Caohai section were396.58-1338.74ng/L and888.85-1322.45ng/g dw, while from103.89-686.59ng/L and59.08～230.94ng/g dw in Waihai section, respectively. In the wet season, the average concentration of the total phenolic EDCs in water and surface sediment in Caohai section was2.84and9.44times of that in Waihai section, respectively; in the dry season, the average concentration in Caohai section was2.28and7.45times compared with Waihai section, respectively. Caohai section was the major receiving area of the domestic sewage and industrial wastewater discharged from the main urban area of Kunming City in the past decades. NP2EO, NP1EO and BPA were the three dominant compounds in the lake, which accounted for more than90%of the total six phenolic EDCs. The concentration of phenolic EDCs in the center and west of Waihai section were lower than that in north, northeast and south areas which adjacent to the urban city. Compared with other lakes, the concentrations of phenolic EDCs in the Waihai section of Dianchi Lake were at their medium-low level, however, the concentrations in the Caohai section were very high, which could pose a potential risk to aquatic organisms.(3) Pollution characteristics of phenolic EDCs in the eight sediment cores in Dianchi Lake were illuminated. In the sediment cores in north and west of Dianchi Lake, the distribution of phenolic EDCs from the surface to the bottom is like "S" shape, while the concentrations of phenolic EDCs decreased in those from the east, southeast and south. With the depth increasing, from surface sediment to20cm, the concentration of phenolic EDCs showed obvious downtrend. The concentrations of phenolic EDCs in surface sediment of C1and C2were about1.9～6.0times than those of C3～C7, while the concentrations of25cm beneath the surface layer were roughly equivalent to those in surface sediment of C3-C6, indicating the developmental process of Kunming City around the east part of Dianchi Lake. The concentration of phenolic EDCs from the bottom to the surface in the sediment cores of C7and C8increased obviously, suggesting that with the development of Jinning County, the pollution load of Dianchi Lake was likely to increase. NP1EO, NP2EO and BPA were identified as the three predominant phenolic EDCs. Therefore, total organic carbon could play an important role in the distribution, fate and behavior of phenolic EDCs in those sediment cores.(4) Twenty-one main inflow rivers and one natural outflow river were studied to clarify the pollution characteristics of phenolic EDCs. The results showed that the concentrations of the total phenolic EDCs in water and surface sediment were from248.13to4650.39ng/L and from113.30to3575.80ng/g dw, respectively. The composition of phenolic EDCs in the rivers were the same as those in Dianchi, NP2EO, NP1EO and BPA are the main compounds. The Xin River, Yunliang River, Chuanfang River, Cailian River, Jinjia River, Zhengda River and Daqing River, running through the main urban area of Kunming City, were seriously contaminated by phenolic EDCs. The concentration level in those rivers could pose potential environmental risks. In2010, the amount of phenolic EDCs discharged into Caohai section of Dianchi Lake by inflow rivers was156.33kg, while Waihai section was313.76kg, and discharging from Haikou river was212.41kg. Compared with other regions and countries, the concentration level of4-NP and4-t-OP in the rivers around Dianchi Lake was lower, while NP2EO, NP1EO and BPA were at their moderate levels. Pollution characteristics of phenolic EDCs along the Panlong River, from Songhuaba reservoir to Dianchi Lake, were discussed. The concentrations of phenolic EDCs were low in the upstream of Panlong River, while midstream of which were seriously polluted; the pollution of middle and lower reaches was relieved; however, the concentrations of phenolic EDCs in downstream were increased significantly.(5) On the basis of the eight STPs of the main urban area of Kunming City, the pollution characteristics of phenolic EDCs were investigated. The concentrations of the total phenolic EDCs in the influent samples collected from the STPs were from2038.82to5066.14ng/L, in effluent samples from420.28to1535.89ng/L, and in sludge samples from1209.67to9464.87ng/g dw. The removal efficiencies of the total phenolic EDCs were from32.34%to88.88%.3AMBR and A2/O processes could eliminate the phenolic EDCs effectively, while Oxidation ditch and ICEAS processes were inferior to that of the former. Degradation was the main pathway to remove phenolic EDCs from STPs. The amount of phenolic EDCs discharged into the eight STPs was3770.92g/d, and24.43%of that was discharged into the water environment.