Jianyang Guo

Anthropogenic input of polycyclic aromatic hydrocarbons into five lakes in Western China

The temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was examined in dated sediments from five lakes in Western China. The surficial concentrations of seven carcinogenic PAHs (BaA, Chyr, BbF, BkF, BaP, DBA and INP, hereafter denoted as PAH7) were highly site-specific. The SigmaPAH7 concentrations generally increased from the deep layers to surface sediments. The temporal trends of SigmaPAH7 concentrations were clearly different from those reported in developed countries. From 1950s to 1980s, which PAHs started to decrease in developed countries, is the right period that PAHs started to increase rapidly in Western China. The fluxes and mass inventories suggest that the PAH7 input over the past three decades was much more rapidly than it was before the 1980s. Source identification indicates that the PAHs were primarily from biomass burning and domestic coal combustion, and increasing vehicular and/or industrial coal combustion emission was also found.

Characterization of Organic Phosphorus in Lake Sediments by Sequential Fractionation and Enzymatic Hydrolysis

The role of sediment-bound organic phosphorus (Po) on lake eutrophication was studied using sequential extraction and enzymatic hydrolysis by collecting sediments from Dianchi Lake, China. Bioavailable Po species including labile monoester P, diester P, and phytate-like P were identified in the sequential extractions by H2O, NaHCO3, and NaOH. For the H2O-Po, 36.7% (average) was labile monoester P, 14.8% was diester P, and 69.9% was phytate-like P. In NaHCO3-Po, 19.9% was labile monoester P, 17.5% was diester P, and 58.8% was phytate-like P. For NaOH-Po, 25.6% was labile monoester P, 7.9% was diester P, and 35.9% was phytate-like P. Labile monoester P was active to support growth of algae to form blooms. Diester P mainly distributed in labile H2O and NaHCO3 fractions was readily available to cyanobacteria. Phytate-like P represents a major portion of the Po in the NaOH fractions, also in the more labile H2O and NaHCO3 fractions. Based on results of sequential extraction of Po and enzymatic hydrolysis, lability and bioavailability was in decreasing order as follows: H2O-Po > NaHCO3-Po > NaOH-Po, and bioavailable Po accounted for only 12.1-27.2% of total Po in sediments. These results suggest that the biogeochemical cycle of bioavailable Po might play an important role in maintaining the eutrophic status of lakes.

Organochlorine pesticides in seafood products from Southern China and health risk assessment

Seafood consumption is an important route of human exposure to organic contaminants. Residual levels of organochlorine pesticides (OCPs), including DDTs, hexachlorocyclohexanes (HCHs), heptachlor, aldrin, alpha-endosulfan, beta-endosulfan, dieldrin, endrin, endrin aldehyde, endrin ketone, methoxychlor, endosulfan sulfate, and heptachlor epoxide, were determined in a wide variety of seafood products collected from 11 coastal cities in southern China in June and October 2005. The results indicated that OCPs were predominated by DDTs and HCHs. The concentrations of other OCP components generally were low and were detectable in a small number of seafood samples only, probably reflective of the generally low levels of these OCPs in the study region and low bioaccumulation potentials in the species under investigation. Risk assessment against various standards clearly showed that seafood products were highly contaminated by DDTs and may pose health threat to local residents and the consumers all over the world. Furthermore, other OCP components, such as dieldrin and heptachlor, also impose lifetime cancer risk, especially to residents of coastal regions who often consume more seafood than those living inland. Therefore, continual monitoring of OCPs in various environment compartments, including biota and abiota, urgently is needed to mitigate effectively the impact of OCPs, particularly DDTs, on human health and the ecological environment.

Ultraviolet absorbance titration for determining stability constants of humic substances with Cu(II) and Hg(II)

We describe an ultraviolet (UV) absorbance titration method that can be used to determine complexing capacities (C(L)) and conditional stability constants (logK) of humic substances (HSs) with metal ions such as Cu(II) and Hg(II). Two fulvic acids (FA) and one humic acid (HA) were used for this study. UV absorbance of HSs gradually increased with the addition of Cu(II) or Hg(II) after blank correction, and these increases followed the theoretical 1:1 (ligand:metal ion) binding model. The results from the absorbance titration calculation for HSs with Cu(II) and Hg(II) compared well with those from fluorescence quenching titration. The titration of the model compound l-tyrosine with Cu(II) proved the validity of this method, and the K and C(L) were within 2.3% and 7.4% of the fluorescence quenching titration. The results suggest that the UV absorbance titration can be used to study the binding capacities of HSs and/or dissolved organic matter (DOM) with trace metals. The advantages and disadvantages of the absorbance titration method were also discussed.

Historical trends of concentrations, source contributions and toxicities for PAHs in dated sediment cores from five lakes in western China.

In this work, sixteen U.S. EPA priority PAH compounds in the dated sediment cores were detected from five lakes in western China. In most lakes, the concentrations of the total PAHs (ΣPAHs) increased from the deep layers to the surface sediments. Two source categories, i.e. vehicular emission and biomass & domestic coal combustion were identified by Unmix, a factor analysis receptor model to explore the source contributions of PAHs in the dated sediments. The source apportionment results showed that biomass & domestic coal combustion contributed larger proportion of PAHs in the five lakes. The toxicities of PAHs in the dated sediments, assessed by BaP equivalent (BaPE) values showed that the BaPE increased gradually from the deep layers to the surface sediments in most lakes. For the first effort, the contribution of each source to BaPE was apportioned by Unmix-BaPE method, and the result indicated that the vehicular emission posed the highest toxic risk. The percentage contribution of vehicular emission for PAHs and BaPE also increased from the deep layers to the surface sediments, while biomass & domestic coal combustion exhibited the opposite tendency.

Removal of antimony from antimony mine flotation wastewater by electrocoagulation with aluminum electrodes

Antimony (Sb) has received increasing environmental concerns due to its potential toxic and carcinogenic properties. In the present work, the electrocoagulation technique was used to treat the flotation wastewater from a heavy antimony polluted area, and the mechanism of removing Sb was also investigated. The study focused on the effect of operation parameters such as current density, initial pH and standing time on the Sb removal efficiency. Antimony concentration of below 1 mg/L in the treated wastewater was achieved, which meets the emission standards established by State Department of Environmental Protection and State Administration of China for Quality Supervision and Inspection and Quarantine of China.

Interaction between carbamazepine and humic substances: a fluorescence spectroscopy study.

Carbamazepine is a popular drug that has been detected in natural environments, but little is known about its biogeochemical cycling, influencing factors, and eco-environmental effects in aquatic ecosystems. Interaction between carbamazepine and humic substances, including fulvic and humic acids, was studied using three-dimensional excitation-emission matrix fluorescence spectroscopy and synchronous-scan fluorescence spectroscopy. The intrinsic fluorescence of humic substances was quenched on the addition of carbamazepine, and static quenching was the primary mechanism. The binding parameters on their interaction, including the conditional binding constants (log K) and binding capacities (C(L)), were estimated by the Ryan-Weber nonlinear theory equation. Log K ranged from 3.41 to 5.04 L/mol at 25 degrees C and pH 7.0. The influence of pH on the complexation and the competition between carbamazepine and Cu(II) for fluorescence-binding sites also were discussed. The present results would be helpful in understanding the fate and biogeochemical cycling of other pharmaceuticals and personal care products in aquatic ecosystems.

Sedimentary record of polycyclic aromatic hydrocarbons in Lake Erhai, Southwest China.

The temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was investigated in a sediment core from Lake Erhai in Southwest China using gas-chromatography/mass spectrometry (GC/MS) method. The total organic carbon (TOC) normalized total PAHs concentrations (sum of US Environmental Protection Agency proposed 16 priority PAHs) ranged from 31.9 to 269 microg/g dry weight (dw), and were characterized by a slowly increasing stage in the deeper sediments and a sharp increasing stage in the upper sediments. The PAHs in the sediments were dominated by low molecular weight (LMW) PAHs, suggesting that the primary source of PAHs was low- and moderate temperature combustion processes. However, both the significant increase in high molecular weight (HMW) PAHs in the upper sediments and the vertical profile of diagnostic ratios pointed out a change in the sources of PAHs from low-temperature combustion to high-temperature combustion. The ecotoxicological assessment based on consensus-based sediment quality guidelines implied that potential adverse biological impacts were possible for benzo(ghi)perylenelene and most LMW PAHs. In addition, the total BaP equivalent quotient of seven carcinogenic polycyclic aromatic hydrocarbons (BaA, CHr, BbF, BkF, BaP, DBA and INP) was 106.1 ng/g, according to the toxic equivalency factors. Although there was no great biological impact associated with the HMW PAHs, great attention should be paid to these PAH components based on their rapid increase in the upper sediments.

Polybrominated diphenyl ethers and decabromodiphenylethane in sediments from twelve lakes in China.

Sediment cores from 12 Chinese lakes were analyzed to investigate the historical inputs of polybrominated diphenyl ethers (PBDEs) and decabromodiphenylethane (DBDPE) during the past few decades. Concentrations of ΣPBDE(1) (sum of tri- to hepta-BDEs), ΣPBDE(2) (sum of nona- to deca-BDEs) and DBDPE in the surface sediments were 0.02-0.29 ng g(-1), 0.46-46.6 ng g(-1) and 1.02-3.64 ng g(-1), respectively. The temporal trends of PBDEs and DBDPE followed a general increase from the bottom to the surface. The calculated fluxes for ΣPBDE(1), ΣPBDE(2) and DBDPE were 0.001-0.09, 0.03-4.24, and 0.05-0.31 ng cm(-2) yr(-1), and the inventories were 0.09-7.86, 0.91-461, and 3.83-24.6 ng cm(-2), respectively. The urbanization and industrialization are highly related to the contamination of PBDEs and DBDPE in sediments. The DBDPE input in recent years was still lower than ΣPBDE(2) but the temporal trends indicated that the contamination would increase with the increasing usage of DBDPE in the future.

Sedimentary record of polycyclic aromatic hydrocarbons and DDTs in Dianchi Lake, an urban lake in Southwest China

Unique time trends of polycyclic aromatic hydrocarbons (PAHs) and dichlorodiphenyltrichloroethanes (DDTs) were found in a dated sediment core from Dianchi Lake (DC), an urban lake in Southwest China. The temporal trend of PAHs in DC was not only different from those in Chinas coastline and remote lakes of China, but also different from those in more developed countries. Identification of sources suggested that PAHs in DC originated primarily from domestic combustion of coal and biomass. However, a change of source from low- and moderate-temperature combustion to high-temperature combustion processes was observed. Different from those in Chinas coastline and some developed countries, the temporal trend of DDTs in DC mirrored the historical usage of DDTs in China, with erosion of soils and surface runoff from its drainage area the most likely routes of DDT introduction to the lake. Rapid urbanization and industrialization in its catchment, effective interception of point-source pollution, and changes in sources of energy during the last few decades have significantly influenced the vertical profiles of PAHs in DC.