[Effects of biochars produced from different sources on arsenic adsorption and desorption in soil].

By using OECD Guideline 106 batch equilibrium method, this paper studied the characteristics of As (V) adsorption and desorption in brown soil as affected by the biochars produced from dairy manure, pine needle, and corn straw. When the addition amount of the biochars was 0.5%, the maximum adsorption amount of As (V) was decreased in the order of dairy manure biochar > pine needle biochar > corn straw biochar, which was related to the basic characteristics of the biochars. The adsorption isotherm of As (V) could be well fitted by Langmuir model (R2 = 0.997). In comparing with CK, both the adsorption capacity (lgKf = 1.99-2.10) and the adsorption intensity (1/N = 0.413-0.449) of As (V) were low, and the main adsorption mechanism was physical adsorption. The desorption rate of As (V) (14.5%-18.7%) was decreased in the order of dairy manure biochar > pine needle biochar > corn straw biochar. The addition of the biochars decreased the adsorption of As (V) by brown soil, which could induce the increase of the bioavailability of As, and strengthen the toxicity of As in soil.

[Dynamics of degradation of oxytetracycline of pig and chicken manures in soil and mechanism investigation].

Simulated indoor incubation experiment was carried out to explore the degradation dynamics of oxytetracycline (OTC) from different manures and the mechanisms were investigated as well. The results suggested that manures accelerated OTC entering soil and degrading period, and resembled the L-type curves. Both degradation rate and degradation percentage were significantly different for different antibiotics with different concentration (P < 0.05). At day 180, the OTC degradation percentage of chicken feces was higher than that of pig feces, and the highest degradation percentage reached to 85.4% and 92.3% respectively. The half-lives of chicken and pig manures were 26.98 d, 31.32 d respectively. Degradation percentage was negatively correlated with the amount of manures used and positively correlated with incubation time (v = A + Blnt, r > 0.96). At day 50, the photo-degradation and micro-degradation accounted for 20.03% and 3.16% of total reduction. 25.05% decreased in photo degradation and 2.50% increased in microbiological degradation. It is indicated that the degradation effects to OTC from pig manures was superior to chicken manures, photo decomposing played an important role in the process of degradation and indigenous soil microorganisms only had a little effect on it. With the extension of incubation time, microbiological decomposing became better, but photo decomposing became weaker.

[DDTs and HCHs residues in soils around Guanting Reservoir and related environmental risk assessment].

Surface soil samples around Guanting Reservoir ranging from 2-10 km were measured for pesticide residues (HCHs and DDTs) concentrations in 2009. Occurrences and related environmental risk were analyzed; furthermore, GIS and geostatistical techniques were applied to analyze the spatial variation of organochlorine pesticides. The results show that concentrations of HCHs in soils range from n.d. to 14.97 ng x g(-1) with a mean value of 0.73 ng x g(-1), and DDTs range from n.d. to 64.91 ng x g(-1) with a mean value of 6.46 ng x g(-1). According to the isomers of HCHs and metabolites of DDTs, HCHs and DDTs residues in soils were primarily from historical use. The land use showed great effect on the degradation of HCHs and DDTs, with the residual level sequence of orchard >> crop land > barren land. Based on kriging interpolation, the spatial distribution of HCHs and DDTs around Guanting Reservoir was observed. Spatial variability indicated how HCHs and DDTs had been applied and distributed in the past. Compared with those in other national or international regions, the concentrations of HCHs and DDTs in soils around Guanting Reservoir were very low.

[Dynamic changes of nitrogen forms in livestock manure during composting and relevant evaluation indices of compost maturity].

In this paper, the dynamic changes of nitrogen (N) forms in different livestock manures were investigated during composting, and the relevant N evaluation indices of compost maturity were approached. The results indicated that during composting, the total nitrogen (TN) concentration in dairy cattle manure increased first and became steady then, but in other five test manures, it decreased first and became steady then. For all test manures, their hydrolizable nitrogen (HN) decreased after an initial increase, NH4(+)-N decreased first and became steady then, while NO3(-)-N had a persistent increase. Among the N indices of compost maturity, HN/TN and NH4(+)-N/TN could be selected as the adaptable parameters to evaluate the maturity, while NO3(-)-N/TN could be only used as a universal one. According to the required standard of compost maturity based on the comprehensive index GI (seed germination index), i.e., GI > 0.50, it was suggested that for the livestock manures except young pig manure, the basic requirements of their compost maturity were HN/TN < 20.77%, NH4(+)-N/TN < 10.06%, and NO3(-)-N/TN > 0.38%.