Yuesuo Yang

Phytoremediation of urban wastewater by model wetlands with ornamental hydrophytes

Phytoremediation offers a cost-effective, non-intrusive, and safe alternative to conventional cleanup techniques. In this study, we used ornamental hydrophytes plants as constructed wetlands to treat urban or rural domestic wastewater. Most ornamental hydrophytes adapted to the wastewater well, and were fairly efficient in scavenging BOD5 (biological oxygen demand 5 d), COD (chemical oxygen demand), TN (total nitrogen), TP (total phosphorus) and heavy metals (Cr, Pb, Cd) in the wastewater. However, the efficiency varied a lot for various species to different contaminants, Iris pseudacorus L. and Acorus gramineus Soland were good choices for treatment of composite-polluted urban wastewater. Some variation in the change of membrane peroxidation and endogenous protective system in responses to wastewater was found among six hydrophytes, which have a correlation with the efficiency of wastewater treatment. It may demonstrate that the developed antioxidative systems of I. pseudacorus and A. gramineus contributed much to their superiority. On the other hand, interaction of different components in the wastewater might have certain effects on phytoremediation.

Environmental impact of estrogens on human, animal and plant life: A critical review

BACKGROUND Since the inception of global industrialization, steroidal estrogens have become an emerging and serious concern. Worldwide, steroid estrogens including estrone, estradiol and estriol, pose serious threats to soil, plants, water resources and humans. Indeed, estrogens have gained notable attention in recent years, due to their rapidly increasing concentrations in soil and water all over the world. Concern has been expressed regarding the entry of estrogens into the human food chain which in turn relates to how plants take up and metabolism estrogens. OBJECTIVES In this review we explore the environmental fate of estrogens highlighting their release through effluent sources, their uptake, partitioning and physiological effects in the ecological system. We draw attention to the potential risk of intensive modern agriculture and waste disposal systems on estrogen release and their effects on human health. We also highlight their uptake and metabolism in plants. METHODS We use MEDLINE and other search data bases for estrogens in the environment from 2005 to the present, with the majority of our sources spanning the past five years. Published acceptable daily intake of estrogens (μg/L) and predicted no effect concentrations (μg/L) are listed from published sources and used as thresholds to discuss reported levels of estrogens in the aquatic and terrestrial environments. Global levels of estrogens from river sources and from Waste Water Treatment Facilities have been mapped, together with transport pathways of estrogens in plants. RESULTS Estrogens at polluting levels have been detected at sites close to waste water treatment facilities and in groundwater at various sites globally. Estrogens at pollutant levels have been linked with breast cancer in women and prostate cancer in men. Estrogens also perturb fish physiology and can affect reproductive development in both domestic and wild animals. Treatment of plants with steroid estrogen hormones or their precursors can affect root and shoot development, flowering and germination. However, estrogens can ameliorate the effects of other environmental stresses on the plant. CONCLUSIONS There is published evidence to establish a causal relationship between estrogens in the environment and breast cancer. However, there are serious gaps in our knowledge about estrogen levels in the environment and a call is required for a world wide effort to provide more data on many more samples sites. Of the data available, the synthetic estrogen, ethinyl estradiol, is more persistent in the environment than natural estrogens and may be a greater cause for environmental concern. Finally, we believe that there is an urgent requirement for inter-disciplinary studies of estrogens in order to better understand their ecological and environmental impact.

DNA mismatch repair related gene expression as potential biomarkers to assess cadmium exposure in Arabidopsis seedlings

In the current study, Arabidopsis seedlings were hydroponically grown on MS media containing cadmium (Cd) of 0-2.0 mg L(-1) for 60 h of treatment. Gene expression profiles were used to relate exposure to Cd with some altered biological responses and/or specific growth effects. RT-PCR analysis was used to quantitate mRNA expression for seven genes known to be involved in DNA mismatch repair (MMR) system and cell division. Results indicated that Cd concentrations of 0.25-2.0 mg L(-1) cause increased total soluble protein levels in shoots of Arabidopsis seedlings in an inverted U-shaped dose-response manner. Exposure to 0.25 and 0.5 mg L(-1) of Cd dramatically induced expression of four genes (i.e. proliferating cell nuclear antigen 2 (atPCNA 2), MutL1 homolog (atMLH1), MutS 2 homolog (atMSH2) and atMSH3) and five genes (i.e. atPCNA1,2, atMLH1 and atMSH2,7), respectively, in shoots of Arabidopsis seedlings; Exposure to 1.0 mg L(-1) of Cd significantly elevated expression of only two genes (atMSH6,7), but caused prominent inhibition in expression of three genes (atPCNA2, atMLH1 and atMSH3) in shoots of Arabidopsis seedlings. The expression alterations of the above genes were independent of any biological effects such as survival, fresh weight and chlorophyll level of shoots. However, shoots of Arabidopsis seedlings exposed to 2.0 mg L(-1) of Cd exhibited statistically prominent repression in expression of these seven genes, and showed incipient reduction of fresh weight and chlorophyll level. This research provides data concerning sensitivity of expression profiles of atMLH1, atMSH2,3,6,7 and atPCNA1,2 genes in Arabidopsis seedlings to Cd exposure, as well as the potential use of these gene expression patterns as representative molecular biomarkers indicative of Cd exposure and related biological effects.

Surface clogging process modeling of suspended solids during urban stormwater aquifer recharge

Aquifer recharge, which uses urban stormwater, is an effective technique to control the negative effects of groundwater over-exploitation, while clogging problems in infiltration systems remain the key restricting factor in broadening its practice. Quantitative understanding of the clogging process is still very poor. A laboratory study was conducted to understand surface physical clogging processes, with the primary aim of developing a model for predicting suspended solid clogging processes before aquifer recharge projects start. The experiments investigated the clogging characteristics of different suspended solid sizes in recharge water by using a series of one-dimensional fine quartz sand columns. The results showed that the smaller the suspended particles in recharge water, the farther the distance of movement and the larger the scope of clogging in porous media. Clogging extents in fine sand were 1 cm, for suspended particle size ranging from 0.075 to 0.0385 mm, and 2 cm, for particles less than 0.0385 mm. In addition, clogging development occurred more rapidly for smaller suspended solid particles. It took 48, 42, and 36 hr respectively, for large-, medium-, and small-sized particles to reach pre-determined clogging standards. An empirical formula and iteration model for the surface clogging evolution process were derived. The verification results obtained from stormwater recharge into fine sand demonstrated that the model could reflect the real laws of the surface clogging process.

Interplay of natural organic matter with flow rate and particle size on colloid transport: experimentation, visualization, and modeling

The investigation on factors that affect the impact of natural organic matter (NOM) on colloid transport in complex hydraulic flow systems remains incomplete. Using our previously established approach, the interplay of flow rate and particle size on the NOM effect was quantified, using flow rates of 1 and 2 mL/min and particle sizes of 50 and 200 nm to represent small nanoparticles (1-100 nm) and large non-nano-microspheres (100-1000 nm) in the low-flow groundwater environment. Latex particles, Suwannee River humic acid (SRHA), and iron oxide-coated sand were used as model particles, NOM, and the aquifer medium, respectively. The quantitative results show NOM blocked more sites for large particles at a high flow rate: 1 μg of SRHA blocked 5.95 × 10(9) microsphere deposition sites at 2 mL/min but only 7.38 × 10(8) nanoparticle deposition sites at 1 mL/min. The particle size effect dominated over the flow rate, and the overall effect of the two is antagonistic. Granule-scale visualization of the particle packing on the NOM-presented sand surface corroborates the quantification results, revealing a more dispersed status of large particles at a high flow rate. We interpret this phenomenon as a polydispersivity effect resulting from the differential size of the particles and NOM: high flow and a high particle size enlarge the ratio of particle-blocked to NOM-blocked areas and thus the NOM blockage. To our knowledge, this is the first model-assisted quantification on the interplay of NOM, flow rate, and particle size on colloid transport. These findings are significant for nanorisk assessment and nanoremediation practices.

Catchment-scale vulnerability assessment of groundwater pollution from diffuse sources using the DRASTIC method: a case study

Abstract The catchment-scale groundwater vulnerability assessment that delineates zones representing different levels of groundwater susceptibility to contaminants from diffuse agricultural sources has become an important element in groundwater pollution prevention for the implementation of the EU Water Framework Directive (WFD). This paper evaluates the DRASTIC method using an ArcGIS platform for assessing groundwater vulnerability in the Upper Bann catchment, Northern Ireland. Groundwater vulnerability maps of both general pollutants and pesticides in the study area were generated by using data on the factors depth to water, net recharge, aquifer media, soil media, topography, impact of vadose zone, and hydraulic conductivity, as defined in DRASTIC. The mountain areas in the study area have “high” (in 4.5% of the study area) or “moderate” (in 25.5%) vulnerability for general pollutants due to high rainfall, net recharge and soil permeability. However, by considering the diffuse agricultural sources, the mountain areas are actually at low groundwater pollution risk. The results of overlaying the maps of land use and the groundwater vulnerability are closer to the reality. This study shows that the DRASTIC method is helpful for guiding the prevention practices of groundwater pollution at the catchment scale in the UK. Citation Yang, Y. S. & Wang, L. (2010) Catchment scale vulnerability assessment of groundwater pollution from diffuse sources using the DRASTIC method: a case study. Hydrol. Sci. J. 55(7), 1206–1216.

Hydrogeo-chemical impacts of air sparging remediation on a semi-confined aquifer: Evidences from field monitoring and modeling

Air sparging (AS) was explored for remediation of a petroleum contaminated semi-confined groundwater system in NE China. Physical, hydro-chemical and hydraulic behaviors in subsurface environment during AS were investigated with support of modeling to understand the hydrogeo-chemical impacts of AS on the aquifer. The responses of groundwater, dissolved oxygen and temperature indicated that the radius of influence of AS was up to 8-9 m, and a 3D boundary of the zone of influence (ZOI) was accordingly obtained with volume of 362 m(3). Water mounding unlike normal observations was featured by continuous up-lift and blocked dissipation. AS induced water displacement was calculated showing no obvious spreading of contaminant plume under this AS condition. Slug tests were employed before and after AS to reveal that the physical perturbation led to sharp increase in permeability and porosity. Modeling indicated that the regional groundwater flow field was not affected by AS except the physical perturbation in ZOI. Hydro-chemically increase of pH and Eh, and reduction of TDS, electrical conductivity and bicarbonate were observed in ZOI during AS. PHREEQC modeling inferred that these chemical phenomena were induced by the inorganic carbon transfer during air mixing.

Microbial community variation and functions to excess sludge reduction in a novel gravel contact oxidation reactor

Excess biomass produced within the degradation processes of organic pollutants is creating environmental challenges. The gravel contact oxidation reactor (GCOR) filled with crushed stone globular aggregates as carriers, has been demonstrated capable of reducing the excess sludge effectively in some pilot and small-scale engineering studies. In order to evaluate the variation and structure of the microbial community and their functions to excess sludge reduction in GCOR, a conventional activated sludge reactor (ASR) was studied as a comparison. The 16S rDNA library of the universal bacteria was constructed, Shannons diversity index (H) and Species evenness (E) were calculated with distance-based operational taxonomic unit and richness (DOTUR) for microbial diversity. Real-time quantity PCR and optical microscope were used for absolute bacterial DNA concentration and eukarya identification, respectively. Meanwhile, the suspended solid index in GCOR and ASR was detected for assessing the excess sludge production. The results indicated that the most abundant bacteria in GCOR were those related to the beta-Proteobacteria group, then gamma-Proteobacteria and to Cytophaga-Flexibacter-Bacteriode (CFB). In the ASR samples major bacteria were in the closest match with gamma-Proteobacteria, then beta-Proteobacteria and CFB. Shannons index (H) was higher (3.41) for diversity of bacteria extracted from the carrier samples in GCOR than that (2.71) from the sludge sample in ASR. Species evenness (E) for the isolates from GCOR and ASR samples was 0.97 and 0.96, respectively. Comparison of the universal bacteria population in GCOR and ASR shows that the total bacterial DNA concentration on the GCOR carriers were 8.98 x 10(5) microg/ microl, twice that in ASR of 4.67 x 10(5) microg/ microl under normal operation of two reactors. But the MLSS in GCOR was only 4.5mg/L, 25 times less than that in ASR of 115.4 mg/L. The most representative eukarya were protozoa both in GCOR (15 no. per 20 ml) and in ASR (15 no. per 20 ml); the next abundant group was attachment plants 10 no. per 20 ml in GCOR and 4 no. per 20 ml in ASR, respectively. Rotifers and copepoda belonging to metazoan were only present in GCOR (8 no. per 20 ml for both rotifers and copepoda). The microbial diversity and population difference both in the GCOR carriers and ASR sludge indicated that the diverse microbes, a large amount of biomass forming longer microbial food chains attached on the carriers may be the main functions for the excess sludge reduction in GCOR.

Cadmium stress alters gene expression of DNA mismatch repair related genes in Arabidopsis seedlings

Cadmium (Cd) is a non essential element, and is a widespread environmental pollutant. Exposure to Cd can result in a variety of adverse health effects in plant and humans. In the current study, Arabidopsis seedlings were used as a bio-indicator of Cd pollution. Seedlings were grown on MS media containing 0-6.0 mg L(-1) Cd for 18 days, and the gene expression patterns were used to link increased Cd exposure with progressive biological effects. Reduction of total soluble protein content in shoots of the Arabidopsis seedlings occurred with increase in Cd concentrations. For the gene expression patterns, seven genes known to be involved in cell division and DNA mismatch repair (MMR) system were investigated by semi-quantitative RT-PCR, and normalized using 18S rRNA gene expression. Expression of the proliferating cell nuclear antigen 2 (atPCNA 2), MutS 3 homolog (atMSH 3) and MutL1 homolog (atMLH1) genes in shoots of Arabidopsis was strongly induced by exposure to 0.75 mg L(-1) Cd, but were repressed by other Cd concentrations whereas exposure to 0.75-6 mg L(-1) of Cd resulted in a decreased expression of atPCNA1, atMSH 2, 6 and 7 genes independently of any observable biological effects, including survival, fresh weight and chlorophyll level of shoots. This work demonstrated that specific gene expression changes could serve as useful molecular biomarkers indicative of Cd exposure and related biological effects.

Cadmium-induced genomic instability in Arabidopsis: Molecular toxicological biomarkers for early diagnosis of cadmium stress.

Microsatellite instability (MSI) analysis, random-amplified polymorphic DNA (RAPD), and methylation-sensitive arbitrarily primed PCR (MSAP-PCR) are methods to evaluate the toxicity of environmental pollutants in stress-treated plants and human cancer cells. Here, we evaluate these techniques to screen for genetic and epigenetic alterations of Arabidopsis plantlets exposed to 0-5.0 mg L(-1) cadmium (Cd) for 15 d. There was a substantial increase in RAPD polymorphism of 24.5, and in genomic methylation polymorphism of 30.5-34.5 at CpG and of 14.5-20 at CHG sites under Cd stress of 5.0 mg L(-1) by RAPD and of 0.25-5.0 mg L(-1) by MSAP-PCR, respectively. However, only a tiny increase of 1.5 loci by RAPD occurred under Cd stress of 4.0 mg L(-1), and an additional high dose (8.0 mg L(-1)) resulted in one repeat by MSI analysis. MSAP-PCR detected the most significant epigenetic modifications in plantlets exposed to Cd stress, and the patterns of hypermethylation and polymorphisms were consistent with inverted U-shaped dose responses. The presence of genomic methylation polymorphism in Cd-treated seedlings, prior to the onset of RAPD polymorphism, MSI and obvious growth effects, suggests that these altered DNA methylation loci are the most sensitive biomarkers for early diagnosis and risk assessment of genotoxic effects of Cd pollution in ecotoxicology.