Water quality criteria and ecological risk assessment for ammonia in the Shaying River Basin, China.

Current Chinese surface water environmental quality standard GB3838-2002 for ammonia fails to take water quality factors and native organism distributions in different basins into consideration. In this study, ammonia toxicity tests were performed using three aquatic organisms native to the Shaying River Basin (China). Published ammonia toxicity data with pH and temperature, and toxicity data acquired in this study were used to establish water quality criteria. The final criterion maximum concentration (CMC) and criterion continuous concentration (CCC) for the Shaying River Basin were 5.09 and 1.36 (mg total ammonia nitrogen (TAN))/L (pH 7 and 20 °C), respectively. In addition, based on the corresponding relationship between ammonia toxicity and temperature and pH, the ecological risk assessment of ammonia was conducted in different seasons for the Shaying River using a tiered approach of both hazard quotient (HQ) and the joint probability (JPC) methods. Two methods gave consistent results: the ecological risks of ammonia to aquatic species in the Shaying River Basin were severe and the risk could be ranked as wet season > flat season > dry season. It is therefore indicating that monitoring, evaluation, and early warning of ammonia pollution need to be taken to prevent and control the risks posed by ammonia pollution, especially for wet season (because of high temperatures and pH) or flat season (because of high pH values). We hope the present work could provide valuable information to manage and control ammonia pollution in the Shaying River Basin.

[Sources and Ecological Risk Assessment of Polycyclic Aromatic Hydrocarbons in the Jiaxing River Network].

In order to study the pollution source and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the Jiaxing river network, PAHs were analyzed by GC-MS. The results show that with the influence of rainfall and surface runoff in the wet season, the types and mass concentrations of PAHs in the river network of Jiaxing differ from the dry season. Ten and 16 priority PAHs were detected in the dry season and wet season, respectively. The average mass concentration of PAHs in the dry season was 143.83ng·L-1 and 73.47ng·L-1 in the wet season. The range of mass concentration of PAHs in the dry and wet season was 77.32-283.76ng·L-1 and 13.05-133.02ng·L-1, respectively, and 2-ring and 3-ring PAHs accounted for 79.18% in the dry season and 73.60% in the wet season. PAHs pollution in the river network of Jiaxing was at a low level compared with the domestic and foreign areas. The isomer ratio and principal component analysis found that the PAHs in the Jiaxing river network mainly come from urban non-point source pollution, combustion source, and traffic pollution in the dry season and wet season. The results of the Kalf risk entropy method show that in the dry season, naphthalene(Nap), acenaphthylene(Acy), acenaphthene(Ace), fluorene(Flu), phenanthrene(Phe), anthracene(Ant), fluoranthene(Fla), pyrene(Pyr), and benzo(a)anthracene(BaA) are at moderate ecological risk. In the wet season, Nap, Acy, Flu, Phe, Fla, Pyr, BaA, benzo(b)fluoranthene(BbF), benzo(k)fluoranthene(BkF), benzo(a)pyrene(BaP), indeno(1,2,3-cd)pyrene(InP), and benzo(g,h,i)perylene(BghiP) are at moderate ecological risk. In the dry season, ∑PAHs are at moderate ecological risk, and low in the wet season. On the whole, PAHs pollution in the Jiaxing river network presents moderate ecological risk levels, and measures to reduce the ecological risk of PAHs in the river network should be taken by the Departments concerned.

Deriving water quality criteria for China for the organophosphorus pesticides dichlorvos and malathion.

Organophosphorus pesticides are effective, cheap, and used extensively but can harm aquatic organism and human health. Here, water quality criteria (WQCs) for dichlorvos (DDVP) and malathion (MAL) were derived. Nine aquatic organisms native to China were used in toxicity tests. Published toxicity data for aquatic organisms native and non-native to China were also analyzed. DDVP and MAL WQCs were derived using (log-normal model) species sensitivity distributions. Species sensitivity distribution curves indicated native and non-native species have different sensitivities to DDVP. The sensitivities of native and non-native species to MAL were not different because non-native species data for fewer than eight genera were available, so further research is required. The results indicated that native species need to be considered when deriving WQCs. The criteria maximum concentration (CMC) and criteria continuous concentration (CCC) were 1.33 and 0.132 µg/L, respectively, for DDVP, and 0.100 and 0.008 µg/L, respectively, for MAL. The CMCs for DDVP and MAL derived using ETX 2.0 software and species sensitivity ranks were different from the CMCs obtained using the SSD method because of parameter uncertainties. The DDVP and MAL WQCs were significantly lower than Chinese surface water quality standard thresholds. The results provide basic data for revising these thresholds.

Fluorescent characteristic and compositional change of dissolved organic matter and its effect on heavy metal distribution in composting leachates.

Composting leachates were collected to investigate the fluorescent characteristic and compositional change of dissolved organic matter (DOM) and the effects of the DOM and nutrients on heavy metal distribution during a leachate combination treatment process. Excitation-emission matrix (EEM) fluorescence spectra showed that, with the progress of the treatment units, the content of fulvic-like, humic-like, and protein-like substances gradually decreased. One fulvic-like component (C1), three humic-like components (C2, C3, and C4), and three protein-like components (C5, C6, and C7) were identified in the leachate DOM by parallel factor analysis. Anaerobic-aerobic processes removed a large fraction of the tyrosine-like component (C7) and tryptophan-like component (C6) and a small amount of humic-like component (C2), while the membrane bioreactor showed a good removal effect on protein-like component. The ultra-filtration membrane treatment had a removal effect on fulvic-like and humic-like component and other recalcitrant compounds, while the reverse osmosis treatment had a good removal effect on both humic-like and protein-like components. Correlation analysis indicated that Mn and Cr were primarily associated with protein-like components and nutrients in the composting leachates. Ni and Pb were bound to fulvic-like, humic-like, and protein-like components, Co and Zn interacted with inorganic nitrogen and total phosphorus, and Cd only interacted with inorganic nitrogen.

Effects of algal bloom formation, outbreak, and extinction on heavy metal fractionation in the surficial sediments of Chaohu Lake.

The effects of algal bloom (AB) on the physicochemical and biochemical properties of water and sediment in lakes have been widely studied. However, limited attention has been directed toward the effects of the processes of AB formation, outbreak, and extinction on heavy metal fractionation in sediment. In this study, water and sediment samples were collected from the AB and free algal bloom (FAB) regions of Chaohu Lake from May to September in 2012. The chemical fractionation of seven heavy metals (Cd, Cr, Cu, Mn, Ni, Fe, and Pb) in sediment was determined by using a modified three-step sequential procedure. Evident processes of AB formation, outbreak, and extinction were observed in the AB region, but not in the FAB region. The TN and TP concentrations in water and sediment in the AB region were significantly higher than those in the FAB region. The water DO concentration was higher in the AB region than that in the FAB region before the early stage of the AB outbreak, but an opposite trend was observed in the stages that followed. Metal fractionation in sediment showed that except for Mn and Cu, the majority of metals were in the residual fraction regardless of the AB process. The AB process slightly altered the concentrations of metal fractions, except for reducible Fe and oxidizable Cu. The result showed that AB formation, outbreak, and extinction slightly affected heavy metal fractionation in sediment though water properties were significantly different among AB processes.

Detection of Copper (II) and Cadmium (II) binding to dissolved organic matter from macrophyte decomposition by fluorescence excitation-emission matrix spectra combined with parallel factor analysis.

Fluorescence excitation-emission matrix (EEM) spectra coupled with parallel factor analysis (PARAFAC) was used to characterize dissolved organic matter (DOM) derived from macrophyte decomposition, and to study its complexation with Cu (II) and Cd (II). Both the protein-like and the humic-like components showed a marked quenching effect by Cu (II). Negligible quenching effects were found for Cd (II) by components 1, 5 and 6. The stability constants and the fraction of the binding fluorophores for humic-like components and Cu (II) can be influenced by macrophyte decomposition of various weight gradients in aquatic plants. Macrophyte decomposition within the scope of the appropriate aquatic phytomass can maximize the stability constant of DOM-metal complexes. A large amount of organic matter was introduced into the aquatic environment by macrophyte decomposition, suggesting that the potential risk of DOM as a carrier of heavy metal contamination in macrophytic lakes should not be ignored.

[Canonical correspondence analysis between phytoplankton community and environmental factors in macrophtic lakes of the middle and lower reaches of Yangtze River].

The phytoplankton communities in 4 macrophtic lakes (Longgan Lake, Liangzi Lake, Futou Lake and Baoan Lake) in Middle-Lower Yangtze Plain were investigated in September 2011, and 7 phylum and 231 species of phytoplankton were detected in the waters. The results indicated that phytoplankton was mainly composed of Cyanophyta, Bacillariophyta and Chlorophyta. The four lakes were mesotrophic. And the main phytoplankton was Phormidium foveolarum, Synedra ulna, Phormidium tenu and Tribonema minus. The relationships between the distribution of phytoplankton and environmental factors in each sampling site were studies by canonical correspondence analysis. The results demonstrated that pH and Total phosphorus are the key factors for the distribution of phytoplankton communities in 4 typical macrophtic lakes in Middle-Lower Yangtze Plain.

[Allelopathic effect of Nelumbo nucifera stem and leaf tissue extract on the growth of Microcystis aeruginosa and Scenedesmus quadricanda].

Effects of Nelumbo nucifera stem and leaf tissue extract on the growth of Microcystis aeruginosa and Scenedesmus quadricanda were studied to verify its potential in entriphication control. Five concentrations of Nelumbo nucifera stem and leaf tissue extract were chosen to compare their inhibitory effects on the growth of Microcystis aeruginosa and Scenedesmus quadricanda. The result showed that the leaf extract inhibited the algae bloom more effectively than the stem extract on the whole. When the leaf extract normality was 25 g x L(-1), the highest inhibition rate of Microcystis aeruginosa and Scenedesmus quadricanda was 71.33% and 78.14%, respectively, while for the stem extract, the values were 49.78% and 52.14%. Propanamide was found in both the stem and leaf tissue extracts of Nelumbo nucifera by GC-MS analysis, with concentrations of 1.1 mg x L(-1) and 0.2 mg x L(-1), respectively. The EC50 values of the two kinds of algae were calculated by the probability method.

[Strategies of nutrients control in lakes based on ecoregions of lakes in China].

In order to better reduce lake eutrophication, based on five ecoregions of lakes, the relationships of total nitrogen (TN), total phosphorus (TP), and TN/TP ratio with chlorophyll-a (Chl-a) in 100 lakes were discussed, furthermore, strategies of nutrient control were proposed respectively. Results showed that among the five ecoregions, the lake eutrophication level was the lowest in Dongbei ecoregion and the highest in Huabei ecoregion, but the eutrophication level in lakes of all the five ecoregions is increasing in recent years. Algal growth in lakes of Dongbei and Huabei ecoregions was limited by phosphorus, while it was simultaneously limited by nitogen and phosphorus in lakes of other three ecoregions (Zhongdongbu, Yungui and Mengxin). In lakes with TN/TP < 10, significant correlation between Chl-a concentration and TN was found in lakes of the five ecoregions except for Huabei ecoregion, and significant correlation between Chl-a concentration and TP was found in lakes of Dongbei and Mengxin ecoregions. In lakes with TN/TP > 17, significant correlation between Chl-a concentration and TP was found in lakes of the five ecoregions except for Mengxin ecoregion, and significant correlation between Chl-a concentration and TN was found in lakes of Zhongdongbu, Yungui and Mengxin ecoregions. In lakes with 10 < TN/TP < 17, no significant correlation between Chl-a and TN (or TP) was found in lakes of all ecoregions except for Zhongdongbu ecoregion where Chl-a concentration was significantly affected by TN. As for strategies of nutrient control and reduction in the five ecoregions, lakes of Huabei ecoregion should adopt TP control in priority, and in Dongbei ecoregion, TP and TN should be controlled simultaneously in lakes with TN/TP < 10, while other lakes should focus on TP control. Lakes in other three ecoregions (Zhongdongbu, Mengxin and Yungui) should control TP and TN simultaneously.

[Speciation and vertical distribution of heavy metals in sediments of Baiyangdian Lake].

In order to find out the heavy metal concentrations and their potential ecological risks on sediments in Baiyangdian Lake, 0-14 cm surface sediments had been collected by the no-disturbance-gravity sampler at seven representative sampling points of Baiyangdian Lake. Optimized BCR sequential extraction procedure was used to carry out the analysis of heavy metal forms in the surface sediments. The heavy metal contents of different forms and in different depths were determined. The relationship between different forms of heavy metal and total organic carbon (TOC) in the sediments was analyzed. The geo-accumulation index (Igeo) was employed to evaluate the extent of heavy metal contamination. The results demonstrated that Co, Fe, Mn, Pb, Zn were mainly in residual form, acid soluble form, Fe-Mn oxide and organic matter bound forms respectively. The tendency of organic bound form of heavy metals and TOC of sediments was greater than the others. The concentration of Co, Pb, Zn decreased with the increase of sediment depth, with the maximal concentration was between 0-2 cm, while the concentration of Mn was the minimal between 6-8 cm and the maximal was at 14 cm. Baiyangdian sediments were not contaminated as a whole by Co, Mn, apart from medium pollution in the entrance of the Fuhe River. The other regions were lightly polluted by Zn and Pb.

[Rapid determination of chemical components in interstitial water of lake sediments using near-infrared spectroscopy].

The near infrared reflectance spectra (NIRS) of interstitial water samples of lake sediments in Chaohu lake were determined by near-infrared reflectance spectrometry. The respective near NIRS calibration models for predicting total nitrogen (TN), total organic carbon (TOC), phosphorus ( PO3(3-)), ammonia nitrogen(NH3-N) and silicate (SiO3-) were built using partial least squares (PLS) algorithm with two spectral pretreatment tools including, wavelet compression combining orthogonal signal correction (OSC) and orthogonal signal correction (OSC) combining wavelet compression. The correlation coefficients between measured values and predicted values in calibration set for TN, NH3-N, PO3(3-), TOC and SiO3(3-) were 0.975, 0.989, 0.937, 0.862 and 0.888, respectively. RMSEC (root mean square error of the calibration) for TN, NH3-N, PO3(3-), TOC and SiO3- were 0.353, 0.238, 0.031 3, 2.005 and 2.674 mg x L(-1), respectively. The correlation coefficients between measured values and predicted values in validation set for TN, NH3-N, PO3(3-), TOC and SiO3- were 0.912, 0.918, 0.773, 0.337 and 0. 856, respectively. RMSEP(root mean square error of the prediction)for TN, NH3-N, PO3(3-), TOC and SiO3- were 1.424, 0.945, 0.081, 7.866 and 4.273 mg x L(-1), respectively.

[Phosphate transform of composting with pre-mixing insoluble phosphate using high temperature dissolved phosphorus microbes inoculation].

In order to enhance the available phosphorus (P) of compost production, the experimental design of composting included three treatments was conducted. The treatments were: Control (CK) with no dissolved phosphate microbes inoculation, no rock phosphate mixing; CP with no dissolved phosphate microbes inoculation, rock phosphate mixing; CMP with dissolved phosphate microbes inoculation, rock phosphate mixing. At different composting phases, the samples were taken for the determination of phosphorus forms. Compared to CK, organic P, dissolved P and rapidly available P of CP increase by 2 049.8, 264.2, 954.0 mg/kg at final stage of composting, respectively; while that of CMP increase by 4 188.6, 648.7, 3 576.4 mg/kg, respectively. The increase of organic P, dissolved P and rapidly available P in CMP is 2.04, 2.46, 3.75 times as that of CP, respectively. The results indicated dissolved phosphate microbes inoculation composting with pre-mixing rock phosphate would accelerate transform efficiency of insoluble phosphate, increase the available P of compost production.

[Effect of using three stages inoculation controlled by temperature on organic matter transformation during composting process].

In order to accelerate composting efficiency, municipal solid wastes (MSW) composting was conducted using three stages inoculation controlled by temperature (TSCT). At different composting phases, the samples were taken for the determination of organic matter transformation. Compared to routine inoculation method (CK), total organic carbon (TOC), dissolved organic matter (DOM) of TSCT decrease by 6.37%, 6.57%; and humic substance (HS), humic acid (HA), and humification index (HI) of TSCT increase by 8.61%, 16.75%, 18.40% at 336 hours of composting, respectively. Elemental analysis indicates C/H, O/C of HA molecule in CK increase by 8.33%, 6.25%; and those of TSCT increase by 18.33%, 11.48% at final stage of composting, respectively. These results all lead to the similar conclusion that TSCT would accelerate humification degree, and increase the efficiency of composting.

[Phosphorus adsorption and regeneration of electric arc furnace steel slag as wetland medium].

The long-term phosphorus (P) adsorption and retention capacities of electric arc furnace (EAF) steel slag materials derived from one batch and a 278-d column experiments with a synthetic P solution were compared. The investigations of the regeneration of the P adsorption capacity by water level decrease was conducted. It was revealed column experiment on a long-term basis can determine P saturation of EAF accurately. And the results can be used for realistic estimations of constructed wetland systems (CWS) longevity. EAF slag showed a high afinity for P, reaching a saturation value of 1.65 g/kg. Regeneration experiment of the P adsorbing capacity by this material showed that, after 4 weeks of water level decrease, EAF steel slag was able to increase its initial P adsorption capacity to 2.65 g/kg. A sequential P fractionation experiment was performed to quantify the proportion of P bound to mineral compounds in EAF. From the most loosely bound to the most strongly bound P fraction, P1 was associated with resin extractable (13%), Fe extractable (0.5 mol/L Na2CO3, 39%), Al extractable (0.1 mol/L NaOH, 21%), Ca extractable (1 mol/L HCl, 13%), and Ca in a stable residual pool (concentrated hot HCl, 14%). X-ray fluorescence analyses of EAF steel slag chemical composition revealed that the continuous application of a P solution resulted in 300% and 170% increases in K2O and P2O5, respectively. Al2O3 and FeO increased by 8%, while the portion of CaO remained unchanged. The investigated properties (P retention potential, regeneration of P adsorption, P fractionation) provide useful data about the suitability of slag material as a media for longterm P removal and dry-wet operation can improve P retention capacity of EAF to prolong the longevity of full-scale CWS.

[Study on dynamic spectral characteristics of humic acid in municipal solid wastes composting].

In the present study, the compost consisted of residual MSW with metal, plastic and glass removed. The composting process was assisted using industrial technology. During the composting, humic acid (HA) was extracted and purified. The spectroscopic characteristics of the HA were determined by using UV, FTIR, and fluorescence spectroscopy. During the composting process, the HA fluorescence spectra exhibited a sharp reduction in relative fluorescence intensity at the short wavelength region, and the primary peak shifted from 335 nm at the initial stage to 458 nm at the final stage of composting, thereby approaching the main peak at 460-480 nm for HA in soil. The FTIR spectra exhibited a reduction in polysaccharides and aliphatic components, and a relative increase in aromatic components; while the HA UV spectra revealed an increase in conjugation and the degree of humification. However, compared with the E4 /E6 value and the spectroscopic characteristics of HA in soil, the HA in the MSW compost has a relatively low molecular weight, a simpler structure and a relatively low degree of aromatic condensation, which also implies that the HA in compost is highly active.

[Relationship between the nitrogen removal and oxygen demand in constructed wetlands].

A simplified model of sequential N transformations and sink was applied to investigate the relationship between the nitrogen removal and oxygen demand to verify the validity of full nitrification-denitrification mechanism in a newly-built multi-stages constructed wetlands. Average net rates of N mineralization ranged from 0.01 to 0.28 g x (m2 x d)(-1), nitrification from 0.50 to 1.54 g x (m2 x d)(-1), denitrification from 0.41 to 1.13 g x (m2 x d)(-1)(3.4% approximately 35.4% of measured N removal in different stage) and plant assimilation from 0.07 to 0.26 g x (m2 x d)(-1) in the five tanks. Nitrification and denitrification occurred concurrently with BOD removal, even in the first stage receiving the higher-strength wastewater. Surprisingly, net areal nitrification rates, was correlated with BOD removal rates positively. Nitrification rates were also correlated linearly with average NH4+-N concentrations in the cascade tanks. The nitrogenous oxygen demand (NOD) required to support full nitrification of ammonia and mineralized Org-N in the wetland was in the upper range of that expected to be able to be supplied through surface and plant-mediated oxygen transfer. Some potential alternative nitrogen removal pathways with reduced overall oxygen requirements that have relevance to constructed wetlands were discussed.

[Phosphorus characteristics in leachate from soils irrigated with livestock wastewater].

Phosphorus fractions could enter water body from surface runoff and leachate due to excessive irrigation of centralized farm wastewater. Organic P is more mobile than inorganic P in the soil profile and represents a significant proportion of P present in leachate from irrigated farm soils. A set of parallel experiments were conducted to compare the characteristics of organic phosphorus in leachate. The experiment was established in a complete randomized block design with nine replicates. The plots received different combinations of P fertilizer and different rates of pig slurry, i. e. 100, 200,300, 400 t x (hm2 x a)(-1), accordingly, the phosphorus was added to the plots was 6.2, 12.4, 19.2, 24.8 kg x (hm2 x a)(-1), respectively. Leachate was collected over a year period and analyzed for different P fractions. Physico-chemical fractionation of P in leachate indicated that the majority of the P loss from the irrigated soil occurred in unreactive particulate (77% - 90%) P forms. 31P nuclear magnetic resonance analysis of eight leachate samples indicated that unreactive P was mainly comprised of monoester and diester forms of organic P. The presence of phosphomonoesterase and phosphodiesterase activity in leachate resulted in hydrolysis of 9% - 29% of total unreactive P (TUP), indicating that some of the monoesters and diesters can be eventually hydrolyzed into inorganic P forms during P transport. To the treatment P45 + F200, enzyme hydrolysis showed that 33% of the TUP was present as labile monoester P (LMP), followed by 17% as inositol hexakisphosphate (IHP) and 9% as diesters (phospholipids and nucleic acids). The results suggest that LMP, IHP and diesters are an important component of organic P leaching from the irrigated soil. The identification of these organic P forms will improve our understanding of the mechanisms responsible for their release from soils, so that specific mitigation strategies can be implemented at the P source.