Recent progress on in-situ chemical oxidation for the remediation of petroleum contaminated soil and groundwater.

Accidental oil leaks and spills can often result in severe soil and groundwater pollution. In situ chemical oxidation (ISCO) is a powerful and efficient remediation technology. In this review, the applications and recent advances of three commonly applied in-situ oxidants (hydrogen peroxide, persulfate, and permanganate), and the gap in remediation efficiency between lab-scale and field-scale applications is critically assessed. Feasible improvements for these measures, especially solutions for the 'rebound effect', are discussed. The removal efficiencies reported in 108 research articles related to petroleum-contaminated soil and groundwater were analyzed. The average remediation efficiency of groundwater (82.7%) by the three oxidants was higher than that of soil (65.8%). A number of factors, including non-aqueous phase liquids, adsorption effect, the aging process of contaminants, low-permeability zones, and vapor migration resulted in a decrease in the remediation efficiency and caused the residual contaminants to rebound from 19.1% of the original content to 57.7%. However, the average remediation efficiency of ISCO can be increased from 40.9% to 75.5% when combined with other techniques. In the future, improving the utilization efficiency of reactive species and enhancing the contact efficiency between oxidants and petroleum contaminants will be worthy of attention. Multi-technical combinations, such as the ISCO coupled with phase-transfer, viscosity control, controlled release or natural attenuation, can be effective methods to solve the rebound problem.

Investigating the composition characteristics of dissolved and particulate/colloidal organic matter in effluent-dominated stream using fluorescence spectroscopy combined with multivariable analysis.

Fluorescence excitation-emission matrix (EEM) spectroscopy combined with principal component analysis (PCA) and parallel factor analysis (PARAFAC) were used to investigate the compositional characteristics of dissolved and particulate/colloidal organic matter and its correlations with nitrogen, phosphorus, and heavy metals in an effluent-dominated stream, Northern China. The results showed that dissolved organic matter (DOM) was comprised of fulvic-like, humic-like, and protein-like components in the water samples, and fulvic-like substances were the main fraction of DOM among them. Particulate/colloidal organic matter (PcOM) consisted of fulvic-like and protein-like matter. Fulvic-like substances existed in the larger molecular form in PcOM, and they comprised a large amount of nitrogen and polar functional groups. On the other hand, protein-like components in PcOM were low in benzene ring and bound to heavy metals. It could be concluded that nitrogen, phosphorus, and heavy metals in effluent had an effect on the compositional characteristics of natural DOM and PcOM, which may deepen our understanding about the environmental behaviors of organic matter in effluent.

[Research on the threshold of Chl-a in Lake Taihu based on microcystins].

Water samples were collected in Lake Taihu from June to October in 2013 in order to investigate the threshold of chlorophyll a (Chl-a). The concentrations of three microcystins isomers (MC-LR, MC-RR, MC-YR) were detected by means of solid phase extraction and high performance liquid chromatography-tandem mass spectrometry. The correlations between various MCs and eutrophication factors, for instance of total nitrogen (TN), total phosphorus (TP), chlorophyll a, permanganate index etc were analyzed. The threshold of Chl-a was studied based on the relationships between MC-LR, MCs and Chl-a. The results showed that Lake Taihu was severely polluted by MCs and its spatial distribution could be described as follows: the concentration in Meiliang Bay was the highest, followed by Gonghu Bay and Western Lake, and Lake Center; the least polluted areas were in Lake Xuhu and Southern Lake. The concentration of MC-LR was the highest among the 3 MCs. The correlation analysis indicated that MC-LR, MC-RR, MC-YR and MCs had very positive correlation with permanganate index, TN, TP and Chl-a (P < 0.01). The threshold value of Chl-a was 12.26 mg x m(-3) according to the standard thresholds of MC-LR and MCs in drinking water. The threshold value of Chl-a in Lake Taihu was very close to the standard in the State of North Carolina, which demonstrated that the threshold value provided in this study was reasonable.

[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.

[Analysis on the forms and release potential of nutrients in sediments from lakes in the West Jiangsu Province].

To probe the effect of nitrogen and phosphorus (P) in sediment on aqueous nutrient concentrations, forms of phosphorus, sediment water interface diffusion fluxes and phosphorus release and adsorption of 10 lakes in the west Jiangsu province were studied. Sediments were sequentially extracted by the modified Ruttenberg's method, and the result showed that inorganic phosphorus in sediments of the lakes was the major fraction of total phosphorus, but the proportion of bioavailable phosphorus was relatively low. Compared with the lakes in northern Jiangsu, the Fe-P was relatively high in sediments of lakes in southern Jiangsu. The diffusion fluxes of lakes were mainly based on NH4(+) -N diffusion in the west Jiangsu, and ions of most of lakes diffused from overlying water to sediment, NO3(-) -N diffused from sediment to overlying water in lakes except for Lake Hongze, Lake Shijiu and Lake Xuanwu. The condition leaning to acidic (pH < 4) or alkaline (pH > 10) was beneficial to phosphorus release, and except for Lake Xuanwu, the least amount of phosphorus released form sediment was higher in acidic condition than that in alkaline condition. The amount of phosphorus adsorption was increasing with temperature increase. Considering the phosphorus adsorption on native phosphorus polluted (NAP-polluted) sediments. All data of P adsorption on sediment samples collected from 7 lakes were fitted to the modified Langmuir model. And the values of the maximum adsorption capacity (Q(m)), phosphorus binding constant (k), native adsorbed exchangeable phosphorus (Q(NAP)), were subsequently obtained. The results showed that the adsorption amount of P in Lake Hongze and Lake Xuanwu was relatively low, which were liable to release P from sediments.

[Regional heterogeneity of lake eutrophication effects in China].

Although biomass of algae (Chl-a) were in variant levels between different lake regions in China under the same nutrients conditions, it demonstrated that efficiencies of TN/TP used by algae had regional differences. In order to clarify the differences, curve estimation in SPSS was used to analyze the linear relationship between Ig Chl-a and Ig TN/lg TP. The slopes of these linear equations were identified as the efficiencies of TN/TP used by algae. The slopes of linear equations from Mengxin Plateau, Yungui Plateau, Northeast Mountain-Plain, lower reach of Yangtze River Plain and North Plain were 1.002, 0.817, 0.761, 0.545, 0.250, orderly. The efficiencies of TN used by algae ranged from the highest to the lowest were lower reach of Yangtze River Plain, Yungui Plateau, North Plain, Northeast Mountain-Plain, Mengxin Plateau, and the slopes of linear equations were 1.401, 1.058, 0.447, 0.239, 0. 099, respectively. Consequently, in Northeast Mountain-Plain, Mengxin Plateau the efficiencies of TP used by algae were higher than those of TN, and in Yangtze River Plain, Yungui Plateau, North Plain, the efficiencies of TN used by algae were higher than those of TP. On the other hand, in order to describe the effects of algae on transparency in different lakes, the relationships between Chl-a and SD were analyzed. The results showed that in Yungui Plateau the effect of algae on transparency was the most obvious as the variation of SD explained by Chl-a was the highest, and Northeast Mountain-Plain, Mengxin Plateau and North Plain followed. However, in lower reach of Yangtze River Plain, the relationship between Chl-a and SD was not significant.

[Effects of land management measures on nutrients emission].

The SWAT model, coupled with a GIS, was applied to simulate the effects of fertilizer application, contour planting and returning land for farming to forestry on nutrients discharges. The results showed that when nitrogen fertilizer of agricultural land increased from 630 to 955 kg/hm2, and phosphorus fertilizer increased from 200 to 300 kg/hm2, nitrogen and phosphorus nutrient emissions have shown a growing trend. Nitrate nitrogen loads reached to 3 776.59 kg which increased 19.7% and the rate of changes was the largest. The change rate of inorganic phosphorus was the smallest which increased only 2.7%. The impact of emission loads on nitrogen and phosphorus was the smallest if contour planting was adopted. When slope farmland which slope is greater than 25% all returned land for farming to forestry, the emission loads of various forms of nitrogen and phosphorus decreased, organic phosphorus decreased 16.3% among them. Organic nitrogen, ammonia nitrogen and inorganic phosphorus compared with before returning land for farming to forestry, decreased 22.7%, 25.4% and 27.9% respectively. In small basin of Zhangjiachong, returning farmlands to forests and reducing the amount of chemical fertilizer on the slope farmlands which slopes are larger than 25% have played a prominent role.

[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.

[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.

[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.

[Characteristics of melting and solidification process of fly ash from refuse incinerator].

This study was conducted to investigate the migration patterns of main compositions of the fly ash from refuse incinerator during melting and solidification process. The experiment was performed in a high temperature melting furnace with temperature controlled. X-ray fluorescence spectroscopy (XRF) and X-ray diffractometer (XRD) were used to analyzed the fly ash treated. The parameters investigated included main compositional contents, phase constituents, alkalinity, vaporation rate, volume reduction rate. The results show: (1) During the melting and solidification process, the contents of CaO, Al2O3, and SiO2 in fly ash increased as the temperature went up, but element Cl and S decreased from initial 20.59%, 10.74% to final 0.15%, 0.22%, respectively. This suggests that higher amount of Cl and S in original fly ash could lead to more vaporation in the form of chloride and calcium salfate in the process, which was further verified by XRD analyzing result. (2) The alkalinity decreased as melting temperature increased, but tended to be stable and maintained around 0.95 after temperature reached flowing temperature. (3) The decomposition and vaporation of the salts in the fly ash mainly occurred in the temperatures between 1150 degrees C and 1260 degrees C, which was approximately 100 degrees C lower than melting temperature.