Baixing Yan

Speciation of Cu and Zn during composting of pig manure amended with rock phosphate

Pig manure usually contains a large amount of metals, especially Cu and Zn, which may limit its land application. Rock phosphate has been shown to be effective for immobilizing toxic metals in toxic metals contaminated soils. The aim of this study work was to investigate the effect of rock phosphate on the speciation of Cu and Zn during co-composting of pig manure with rice straw. The results showed that composting process and rock phosphate addition significantly affected the changes of metal species. During co-composting, the exchangeable and reducible fractions of Cu were transformed to organic and residue fractions, thus the bioavailable Cu fractions were decreased. The rock phosphate addition enhanced the metal transformation depending on the level of rock phosphate amendment. Zinc was found in the exchangeable and reducible fractions in the compost. The bioavailable Zn fraction changed a little during the composting process. The composting process converted the exchangeable Zn fraction into reducible fraction. Addition of an appropriate amount (5.0%) of rock phosphate could advance the conversion. Rock phosphate could reduce metal availability through adsorption and complexation of the metal ions on inorganic components. The increase in pH and organic matter degradation could be responsible for the reduction in exchangeable and bioavailable Cu fractions and exchangeable Zn fraction in rock phosphate amended compost.

Changes in Phosphorus Fractions and Nitrogen Forms During Composting of Pig Manure with Rice Straw

Abstract The study was conducted to reveal P fractions and N forms changing characters during composting of pig manure with rice straw. During composting, the NH 4 + -N concentration decreased and reached at a relatively low value ( −1 ) in the final compost, while the NO 3 − -N concentration increased. Total N losses mainly occurred during thermophilic phase due to the high temperature, the high NH 4 + -N concentration and the increase of pH value. Labile inorganic P was dominated in the pig manure and initial compost mixture. During composting, the proportion of labile inorganic P of total extracted P decreased, while the proportion of Fe+Al-bound P, Ca+Mg-bound P and residual P increased. The evolutions of the proportion of labile inorganic P, Fe+Al-bound P and Ca+Mg-bound P were well correlated with the changes of pH value, organic matter and C/N ratio. Therefore, composting could increase the concentration of N and P and decrease the presence of NH 4 + -N and labile P fractions which might cause environmental issues following land application.

Temporal variability of iron concentrations and fractions in wetland waters in Sanjiang Plain, Northeast China.

Chemical forms, reactivities and transformation of iron fractions in marshy waters were investigated with cross-flow filtration technique to study the iron environmental behavior. Iron fractions were divided into four parts: acid-labile iron (pre-acidification of unfiltered marshy water samples, > 0.7 microm), high-molecular-weight iron (0.7-0.05 microm), medium-molecular-weight iron (0.05-0.01 microm), and low-molecular-weight iron (< 0.01 microm). The cross-flow filtration suggested that iron primarily exist in both the > 0.7 microm and < 0.01 microm size fractions in marshy waters. Rainfall is the key for rain-fed wetland to determine fate of iron by changing the aquatic biochemical conditions. By monitoring the variation of iron concentrations and fractions over three years, it was found that dissolved iron and acid-labile iron concentrations exhibit a large variation extent under different annual rainfalls from 2006 to 2008. The seasonal variation for iron species proved that the surface temperature could control some conversion reactions of iron in marshy waters. Low-molecular-weight iron would convert to acid-labile iron gradually with temperature decreasing. The photochemical reactions of iron fractions, especially low-molecular-weight iron had occurred under solar irradiation. The relative proportion of low-molecular-weight in total dissolved iron ranging from 28.3% to 43.2% were found during the day time, which proved that the observed decreasing concentration of acid lability iron was caused by its degradation to low molecular weight iron.

Estimating Soil Erosion in Northeast China Using 137Cs and 210Pbex

Abstract Evaluation of soil erosion in agricultural fields is valuable to develop conservation practices for reducing agricultural nonpoint source pollution. Soil erosion rates were quantified using the fallout radionuclide tracer technique in Mojiagou Basin located on the outskirts of Changchun in Northeast China. The calculated soil erosion rates in the study area were 1.99 and 1.85 mm year −1 using 137 Cs and excess 210 Pb ( 210 Pb ex ) measurements, respectively. Both fallout radionuclides showed a similar tendency at downslope sites. All measured sites have experienced net erosion during the past 50 to 100 years. 137 Cs and 210 Pb ex measurements were useful to quantify soil erosion rates on field and small basin scales. At this rate of erosion, the current fertile topsoil layer would be entirely removed within 70 years.

NUTRIENT LIMITATION AND WETLAND BOTANICAL DIVERSITY IN NORTHEAST CHINA: CAN FERTILIZATION INFLUENCE ON SPECIES RICHNESS?

The effect of fertilization on species richness was investigated in wetland ecosystems in northeast China. Plant nitrogen-to-phosphorus ratios (N/P) were used to assess nutrient limitation. A freshwater wetland Carex lasiocarpa community was grown at 12 nutrient treatments (4 N treatments, 4 P treatments, and 4 N + P treatments) and 1 control. Plant nutrient concentrations, soil pH, and species richness were determined after two growing seasons. Fertilization induced changes in plant N/P and soil pH. The marsh wetland plants species richness responded differently to nutrients and soil pH. The relationship between species richness and plant N/P ratios was unimodal. Plant species richness was maximal when the N/P ratio approached 9.5, because availability of nutrient supply was balanced when the plant N/P ratios were close to 9.5. The species richness decreased slightly with N/P < 9.5 and N/P > 9.5. Both N and P availability influenced species richness. P fertilization increased species richness in the N treatment. Species richness increased from 4.3 to 5.6 with P input in the treatment using 4 g m−2 year−1 of N and from 3.3 to 6.0 with increasing P input in the treatment using 40 g m−2 year−1 of N. N fertilization also increased species richness in the P treatment. Species richness increased from 4.3 to 5.6 with increasing N input in the treatment using 1.2 g m−2 year−1 of P and from 4.6 to 6.0 with increasing N input in the treatment using 19.2 g m−2 year−1 of P. However, P input resulted in plant N/P ratio deviation from the optimal value, thus species richness decreased in the wetland. P may be a severe constraint of species richness in the wetland. There was a significantly positive liner relationship between soil pH and species richness. Species have different nutrient requirements and exploit nutrients with varying efficiency, which induce changes of soil pH. By univariate analysis of variance, the unique effect of soil pH accounted for most of the explained variation in species richness. The species richness variance explained jointly by N/P ratios and soil pH was 28.0%.

Risk assessment of heavy metals contamination in sediment and aquatic animals in downstream waters affected by historical gold extraction in Northeast China

ABSTRACT To assess the risk of heavy metals contamination on the aquatic ecosystem in downstream waters of a gold field in Northeast China, samples of sediment, fish, shrimp, and mussels were collected to determine heavy metals concentrations. According to Igeo, more attention should be given to Hg, Pb, and Cu pollution in sediment of Weisha River. For aquatic animals, the greatest contents of Hg, Cu, and Pb were found in samples collected from Weisha River, while the maximum values of Zn, Cd, and Cr were found in Hongshi Reservoir, Banmiao River, and Songhua Lake, respectively. The Hg and Pb contents in fish were found in the order of predatory fish > omnivorous fish > herbivorous fish, although for other metals no significant difference was observed among the three trophic levels. The contents of metals in Oriental river prawn and Chinese pond mussel were greater than that in fish, except for Pb. The Target Hazard Quotient and Hazard Index of metals showed that the Carnivorous and Omnivorous fish from Songhua Lake and Hongshi Reservoir, as well as all fish from Banmiao River and Weisha River, were not suitable for consuming in the view of the combined risk of all metals.

An innovative wood-chip-framework substrate used as slow-release carbon source to treat high-strength nitrogen wastewater

Removal of nitrogen in wastewater before discharge into receiving water courses is an important consideration in treatment systems. However, nitrogen removal efficiency is usually limited due to the low carbon/nitrogen (C/N) ratio. A common solution is to add external carbon sources, but amount of liquid is difficult to determine. Therefore, a combined wood-chip-framework substrate (with wood, slag and gravel) as a slow-release carbon source was constructed in baffled subsurface-flow constructed wetlands to overcome the problem. Results show that the removal rate of ammonia nitrogen (NH4+-N), total nitrogen (TN) and chemical oxygen demand (COD) could reach 37.5%-85%, 57.4%-86%, 32.4%-78%, respectively, indicating the combined substrate could diffuse sufficient oxygen for the nitrification process (slag and gravel zone) and provide carbon source for denitrification process (wood-chip zone). The nitrification and denitrification were determined according to the location of slag/gravel and wood-chip, respectively. Nitrogen removal was efficient at the steady phase before a shock loading using slag-wood-gravel combined substrate because of nitrification-denitrification process, while nitrogen removal was efficient under a shock loading with wood-slag-gravel combined substrate because of ANAMMOX process. This study provides a new idea for wetland treatment of high-strength nitrogen wastewater.

Flux characteristics of total dissolved iron and its species during extreme rainfall event in the midstream of the Heilongjiang River

The occurrence of extreme rainfall events and associated flooding has been enhanced due to climate changes, and is thought to influence the flux of total dissolved iron (TDI) in rivers considerably. Since TDI is a controlling factor in primary productivity in marine ecosystems, alteration of riverine TDI input to the ocean may lead to climate change via its effect on biological productivity. During an extreme rainfall event that arose in northeastern China in 2013, water samples were collected in the midstream of the Heilongjiang River to analyze the concentration and species of TDI as well as other basic parameters. The speciation of TDI was surveyed by filtration and ultrafiltration methods. Compared with data monitored from 2007 to 2012, the concentration of TDI increased significantly during this event, with an average concentration of 1.11 mg/L, and the estimated TDI flux reached 1.2×10(5) tons, equaling the average annual TDI flux level. Species analysis revealed that low-molecular-weight complexed iron was the dominant species, and the impulse of TDI flux could probably be attributed to the hydrological connection to riparian wetlands and iron-rich terrestrial runoff. Moreover, dissolved organic matter played a key role in the flux, species and bioavailability of TDI. In addition, there is a possibility that the rising TDI flux could further influence the transport and cycling of nutrients and related ecological processes in the river, estuary coupled with the coastal ecosystems, which merits closer attention in the future.

Accumulation of Lead, Zinc, and Copper in Scalp Hair of Residents in a Long-Term Irrigation Area Downstream of the Second Songhua River, Northeast China

ABSTRACT In the present study, lead, zinc, and copper concentrations in scalp hair of 120 residents in a long-term irrigation area in downstream of the Second Songhua River were determined. The correlation between metals in hair and the subject descriptors (i.e., age, gender, height, weight, smoking, and drinking habits) was determined, and the metals’ contents in the commonly consumed foods and the local environment were also analyzed. The mean concentrations of Pb, Zn, and Cu in residents’ scalp hair were 85.9 ± 51.1, 174.0 ± 31.1, and 6.7 ± 4.4 μg/g, respectively. Drinking habits influenced Pb contents significantly; the highest Pb concentrations were found in hair of residents who drink frequently, followed by those who drink occasionally and those who never drink. However, for Zn and Cu, no significant influence was found. There was no significant correlation between metal contents and age, gender, or smoking habits (p > .05). However, a significant positive correlation (p < .01) was observed between Zn contents in hair and height. In general, the concentrations of metals in most of the food and the local environments meet Chinas or other standards. However, it is still necessary to pay attention to Pb pollution in the study area for public health.

Snowmelt Runoff: A New Focus of Urban Nonpoint Source Pollution

Irregular precipitation associated with global climate change had been causing various problems in urban regions. Besides the runoff due to rainfall in summer, the snowmelt runoff in early spring could also play an important role in deteriorating the water quality of the receiving waters. Due to global climate change, the snowfall has increased gradually in individual regions, and snowstorms occur more frequently, which leads to an enhancement of snowmelt runoff flow during the melting seasons. What is more, rivers just awaking from freezing cosntitute a frail ecosystem, with poor self-purification capacity, however, the urban snowmelt runoff could carry diverse pollutants accumulated during the winter, such as coal and/or gas combustion products, snowmelting agents, automotive exhaust and so on, which seriously threaten the receiving water quality. Nevertheless, most of the research focused on the rainfall runoff in rainy seasons, and the study on snowmelt runoff is still a neglected field in many countries and regions. In conclusion, due to the considerable water quantity and the worrisome water quality, snowmelt runoff in urban regions with large impervious surface areas should be listed among the important targets in urban nonpoint source pollution management and control.