[Effects of Vermicomposting on Compost Quality and Heavy Metals：A Meta-analysis].

In order to comprehensively evaluate the effects of vermicomposting on compost quality and the conversion of heavy metals under different control conditions, 109 studies were reviewed. The effects of earthworm species, pre-compost time, ventilation methods, initial C/N, initial pH, and initial moisture of the raw materials on compost quality and the heavy metal toxicity were quantitatively discussed during the vermicomposting process through Meta-analysis. The results showed that the six subgroups of factors all showed obvious influences on the compost quality and heavy metal toxicity. After vermicomposting, the contents of NO3--N (116.2%), TN (29.1%), TP (31.2%), and TK (15.0%) were significantly increased, whereas NH4+-N (-14.8%) and C/N (-36.3%) were significantly decreased. Meanwhile, the total amount of Cu and Cr of the final compost and their bioavailability were significantly reduced. Considering the influences of grouping factors on compost quality and heavy metals, it is recommended to adjust the initial moisture of pile materials to 70%-80%, C/N to 30-85, and pH to 6-7 and to conduct pre-composting for 0-15 d; additionally, vermicomposting should be naturally placed when the composting is aimed at promoting the compost quality. If the main purpose is to weaken the perniciousness of heavy metals in the raw material, it is recommended to adjust the initial moisture of the material to 50%-60%, C/N to less than 30, and pH to 7-8; to conduct no pre-compost; regularly turn the piles; and use the earthworm Eudrilus eugeniae for vermicomposting.

[Concentration Characteristics and Source Analysis of PM2.5 During Wintertime in Zhengzhou-Xinxiang].

To study the pollution characteristics, sources, and transportation process of PM2.5 and its chemical compositions in the Zhengzhou-Xinxiang region, PM2.5 samples were collected using a middle volume sampler, in Zhengzhou and Xinxiang urban areas for 30 consecutive days during the winter of 2016. The mass concentration of PM2.5 was measured gravimetrically. 17 trace metals were determined by inductively coupled plasma-mass spectrometry (ICP-MS), and 7 water-soluble ions were determined by ion chromatography. The enrichment factor (EF) method and principal component analysis were employed to determine the source apportionment. The results showed that the daily mean PM2.5 mass concentration during the winter sampling period of 2016 in Xinxiang and Zhengzhou was 223.87 µg·m-3 and 226.67 µg·m-3, respectively, which indicated that pollution levels were relatively high in both cities. The concentration of three macro elements (Al, Ca, and Fe) accounted for 50% of the total metal elements in both cities, while the heavy metals concentration was higher in Xinxiang than in Zhengzhou. The EFs of Cd, Ag, and Pb in Xinxiang were far higher than 1000, while only Cd was higher than 1000 in Zhengzhou. NO3-, SO42-, and NH4+ were the main ions in the two cities. They exceeded 94% of total water-soluble ions and existed in the forms of (NH4)2SO4 and NH4NO3. The principle component analysis showed that the main contributors to PM2.5 were a mixture of biomass combustion and secondary aerosol in Xinxiang, and a mixture of coal combustion and traffic emissions in Zhengzhou, accounting for 34.94% and 33.99% of total PM2.5 emissions, respectively.

A novel method for sewage sludge composting using bamboo charcoal as a separating material.

Traditional composting processes must be conducted with a bulking agent to ensure adequate air space for aeration. The bulking agent and composting materials are always completely mixed. A novel layered structure was introduced in sewage sludge composting, in which no bulking agent was used and bamboo charcoal was used as a separating material. Three lab-scale composting reactors (A: sawdust and sludge; B: bamboo charcoal and sludge; and C: sawdust, bamboo charcoal, and sludge) were continuously operated for 29 days. Several physicochemical parameters were investigated to evaluate the feasibility of layered composting with bamboo charcoal. The results indicated that the maximum temperatures during the thermophilic stage in treatments A, B, and C were 51.4, 50.9, and 51 °C, respectively. Layered composting with bamboo charcoal decreased the pH of the thermophilic stage from 8.98 in A to 8.75 in C, and delayed the peaks by about 120 h. The degradation rates of dissolve organic carbon (DOC) and dissolved nitrogen (DN) were 75 and 71.5% in treatment B, respectively, which were significantly higher than those of control group A (60 and 59.1%, respectively). The total NH3 emissions of treatment C (2127.8 mg) were significantly lower than those of A (2522.8 mg). Our results suggested that layered composting using bamboo charcoal as a separating material could be an alternative strategy to the traditional composting method. Moreover, layered composting combined with sawdust could effectively reduce NH3 emissions and N loss.

[Effects of Acidic Materials on the N Transformations During the Composting of Pig Manure and Wheat Straw].

Understanding the effects of acidic materials on the N transformations becomes of critical importance to choose the additives with preserving nitrogen during the manure composting. A 40 d static composting experiment was conducted in the laboratory to explore the effects of acidic materials on changes of temperature, pH, EC (electrical conductivity), GI (germination index), N compounds and TOC (total organic carbon) during the composting of pig manure and wheat straw.Three acidic materials were selected as the additives, including phosphate fertilizer (P), rotten apples (A) and vinegar (V). The results showed that the duration with temperature higher than 50℃ in four treatments all exceeded ten days and reached the health standard of high temperature composting. The addition of phosphate fertilizer delayed the time of the pile entering into the high temperature stage, decreased the pH, and increased the EC during the whole composting. On a mass basis, 53.1%, 36.2%, 46.5% and 41.5% of original amount of N in CK, P, A and V were lost during the first 16 d, but there was still 20% N loss during 16-24 d in P and V treatments. The NH3-N loss accounted for 26.0%, 11.8%, 21.5% and 20.2% of the N loss. The addition of acidic materials effectively reduced the N loss and the emissions of NH3, and the phosphate fertilizer showed the best effect. In the end of composting, the GI all exceeded 80%, and met maturity requirements.

[Changes of Soil Organic Carbon and Its Influencing Factors of Apple Orchards and Black Locusts in the Small Watershed of Loess Plateau, China].

Orchard and black locust are two typical plants for comprehensive control in the small watershed of land uses in Loess area. The analysis of soil carbon sequestration function changes of growing two plants is important to gain a deep understanding of soil carbon cycle process and its influencing factors of terrestrial ecosystems under the condition of small watershed comprehensive control. The experiment was conducted in the Changwu State Key Agro-Ecological Station, Shanxi, China. SOC, TN, fine root biomass and litter amount were determined at different age apple orchards and black locusts on the slope land of Wangdonggou watershed to study the variation characteristics of soil organic carbon and its influencing factors under two measurements. The results showed that: (1) SOC and TN contents in apple orchards significantly decreased with the increased age, whereas those in black locust showed an increased tendency with the age increased. Compared with the adjacent cropland,the SOC and TN contents in year 3, year 8, year 12 and year 18 apple orchards were decreased 3. 26%, 10. 54%, 18. 08%, 22. 55% and - 8. 08%, - 0. 48%, 4. 97%, 16. 91%, respectively. However,SOC and TN contents increased 5. 31%, 32. 36%, 44. 13% and 2. 49%, 15. 75%, 24. 22%, in year 12, year 18 and year 25 black locusts, respectively. (2) The fine root biomass in year 3, year 8, year 12, and year 18 apple orchards were about 25. 97% 66. 23%, 85. 71% and 96. 10% of the adjacent cropland, respectively; and the litter amounts were all 0 g . m-2. However, compared with adjacent cropland, The fine root biomass in year 12, year 18 and year 25 black locusts were increased 23. 53%, 79. 41%, 157. 35%, respectively; and the litter input rates were 194, 298 , 433 g . (m2 . a) -1, respectively. (3) The difference of organic matter input was the major factor which drove the variability of soil carbon sequestration function of apple orchard and black locust ecosystems.

[Effects of Nitrogen Fertilization on Soil Respiration and Temperature Sensitivity in Spring Maize Field in Semi-Arid Regions on Loess Plateau].

Understanding the effects of nitrogen fertilization on soil respiration rate and its temperature sensitivity (Q10) is of critical importance to predict the variability of soil respiration in cropland. A field experiment was established in a rain-fed spring maize cropland (Zea mays L. ) in the State Key Agro-Ecological Experimental Station in the Loess Plateau in Changwu County, Shaanxi Province, China. The experiment comprised of two treatments: no N-fertilizer application ( CK) and N-fertilizer application with 160 kg N · hm(-2) (N). Soil respiration rate, soil temperature, soil moisture, yields, aboveground biomass and root biomass were measured in two continuous spring maize growing seasons from April 2013 to September 2014. The cumulative soil CO2 emissions were increased by 35% in 2013 and 54% in 2014 in N treatment as compared to CK treatment. Though nitrogen fertilization significantly increased the cumulative soil CO2 emissions (P < 0.05), it did decrease evidently the temperature sensitivity of soil respiration (P < 0.05) . The Q10 values in N treatment were decreased by 27% and 17% compared with CK treatment in 2013 and 2014, respectively. Nitrogen fertilization significantly increased the maize yields, aboveground biomass and root biomass (P < 0.05). Root biomasses in N treatment were 32% and 123% greater than those in CK treatment of 2013 and 2014, respectively. Nitrogen fertilization had no marked influence on soil temperature or moisture. Root biomass was a critical biotical factor for variation of soil respiration under nitrogen fertilization.

[Variation characteristic in soil respiration of apple orchard and its biotic and abiotic influencing factors].

To evaluate the orchard variability of soil respiration and the response of soil respiration to its influencing factors is helpful for a deep understanding about the effects of converting cropland to apple orchard. A field experiment was conducted in the Changwu State Key Agro-Ecological Station. Soil respiration, soil temperature, soil moisture and roots biomasses were periodically measured in a mature apple orchard during 2011 and 2012. Soil respiration decreased as the distance from the trunk increased. The cumulative soil respiration in the 0.5 m-distance from the trunk was 20% and 31% higher than that in the 2 m-distance from the trunk, respectively in 2011 and 2012. The temperature sensitivity of soil respiration (Q10) was relatively lower in the 2 m-distance than that in the 0. 5 m-distance in both years. Soil temperature and soil moisture were slightly higher in the 2 m-distance, but there was no significant difference between the 2 m-distance and the 0. 5 m-distance. Soil respiration and soil temperature showed a significant exponential relationship, but there was no positive correlation between soil moisture and soil respiration. Soil temperature changes can explain seasonal variation of soil respiration well, but it could not explain its spatial variability. Root density was an important factor for the spatial variability of soil respiration and Q15. Variation of soil respiration coefficient was 23% -31%. Therefore, the distance from the trunk should be considered when estimating orchards soil respiration.

[Effects of grape seed addition in swine manure-wheat straw composting on the compost microbial community and carbon and nitrogen contents].

Taking substrates swine manure and wheat straw (fresh mass ratio 10.5:1) as the control (PMW), a composting experiment was conducted in a self-made aerated static composting bin to study the effects of adding 8% grape seed (treatment PMW + G) on the succession of microbial community and the transformation of carbon and nitrogen in the substrates during the composting. Seven samples were collected from each treatment, according to the temperature of the compost during the 30 d composting period. The microbial population and physiological groups were determined, and the NH4(+)-N, NO3(-)-N, organic N, and organic C concentrations in the compost were measured. Grape seed addition induced a slight increase of bacterial count and a significant increase of actinomycetes count, but decreased the fungal count significantly. Grape seed addition also decreased the ratio of bacteria to actinomycetes and the counts of ammonifiers and denitrifiers, but increased the counts of nitrifiers, N-fixing bacteria, and cellulose-decomposing microorganisms. The contents of NH4(+)-N and organic C decreased, while that of NO3(-)-N increased obviously. The NO3(-)-N content in the compost was positively correlated with the actinomycetes count. During composting, the compost temperature in treatment PMW + G increased more rapidly, and remained steady in thermophilic phase, while the water content changed little, which provided a stable and higher population of actinomycetes and nitrifiers in thermophilic phase, being beneficial to the increase of compost nitrate N.