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991.
Michelle Casey Chris Gennings W. Hans Carter Virginia C. Moser Jane Ellen Simmons 《Journal of Agricultural, Biological & Environmental Statistics》2004,9(3):339-361
An important environmental and regulatory issue is the protection of human health from potential adverse effects of cumulative exposure to multiple chemicals. Earlier literature suggested restricting inference to specific fixed-ratio rays of interest. Based on appropriate definitions of additivity, single chemical data are used to predict the relationship among the chemicals under the zero-interaction case. Parametric comparisons between the additivity model and the model fit along the fixed-ratio ray(s) are used to detect departure from additivity. Collection of data along reduced fixed-ratio rays, where subsets of chemicals of interest are removed from the mixture and the remaining compounds are at the same relative ratios as considered in the full ray, allow researchers to make inference about the effect of the removed chemicals. Methods for fitting simultaneous confidence bands about the difference between the best fitting model and the model predicted under additivity are developed to identify regions along the rays where significant interactions occur. This general approach is termed the “single chemicals required” (SCR) method of analysis. A second approach, termed “single chemicals not required” (SCNR) method of analysis, is based on underlying assumptions about the parameterization of the response surface. Under general assumptions, polynomial terms for models fit along fixed-ratio rays are associated with interaction terms. Consideration is given to the case where only data along the mixture rays are available. Tests of hypotheses, which consider interactions due to subsets of chemicals, are also developed. 相似文献
992.
Qiangqiang Rong Jingtao Liu Yanpeng Cai Zhaohua Lu Zhenzhen Zhao Wencong Yue Jiangbao Xia 《Journal of Soils and Sediments》2016,16(3):864-877
Purpose
As a useful comprehensive index for reflecting nutrient cycling in soils, nitrogen (N) and phosphorus (P) stoichiometry is subject to influences of many external environmental and biological factors. Studies on such influences were limited, and the influential mechanism remains unclear. The purpose of this research is to investigate soil N and P stoichiometric variations and analyze “fertile island” effects of Tamarix chinensis Lour. (T. chinensis) in the coastal wetland of Laizhou Bay in China.Materials and methods
Soil samples beneath clusters and communities of T. chinensis were collected respectively in July 2012. Amounts of ammonium, nitrate, and available phosphorus in the soil samples were measured through the corresponding standard methods for material measuring.Results and discussion
In general, there were significant vertical variations in soil N and P stoichiometry beneath clusters and communities of T. chinensis. A downtrend was observed for N and P contents with the increase in soil depth. On the contrary, the N/P ratio revealed a trend of going up first and then dropping off along with the increase of the soil depth. Comparatively, the horizontal variations in the soil N and P stoichiometry beneath a single cluster of T. chinensis were greater in the topsoil than those in the subsoil. The N and P contents gradually decreased from the canopy center to the outside. On the contrary, an opposite trend was found for the N/P ratio. For the horizontal variations beneath T. chinensis communities, there were no significant differences for either N and P contents or N/P ratios.Conclusions
Similar to the ecosystems in arid and semi-arid areas, vegetations in many semi-humid areas could also form fertile islands and exert significant influences on the soil nutrient cycle. The formation of fertile islands beneath a single cluster of T. chinensis could have significant influence on soil N and P stoichiometry. Under the influence of fertile islands beneath T. chinensis, the limiting element of the biogeochemical processes in the coastal wetland of Laizhou Bay might change from N to P. However, the influences of fertile island effects on soil N and P stoichiometry beneath T. chinensis communities were relatively small, illustrating that the influences of fertile island effects was not significant at the community level. Thus, the impacts of environmental factors on soil N and P stoichiometry might be greater than that of the fertile island effects in the wetland on a larger scale.993.
Purpose
The variation in soil microbial community patterns is primarily influenced by ecological processes associated with spatial distance and environmental heterogeneities. However, the relative importance of these processes in determining the patterns of soil microbial biodiversity in different successional forests remains unclear.Materials and methods
Based on the species data from denaturing gradient gel electrophoresis (DGGE) analysis, we described the composition and beta diversity of ammonia-oxidizing archaea (AOA) community, an important functional microbial group in regulating nitrogen cycle, in a middle-succeed stand (60 years of secondary succession) and an undisturbed native stand in a subtropical forest in southern China. The composition pattern was examined using a multi-response permutation procedure (MRPP), and the beta diversity was described using the Sørensen index. The relative influence of edaphic, vegetational, spatial, and topographical factors on AOA composition and beta diversity was assessed by variation partitioning and multiple regression on distance matrices (MRM), respectively.Results and discussion
We did not find any stand-specific patterns in AOA community composition in the two stands; however, the influential variables were different between the two stands; 7.3 and 4.5 % of the total variation in AOA community composition could be explained by edaphic (i.e., available potassium and total phosphorus) and spatial variables, respectively, in the middle-succeed stand, while 3.7 and 2.8 % of the variation were explained by spatial variable and available phosphorus, respectively, in the native stand. Soil total phosphorus influenced the beta diversity of AOA community most in the middle-succeed stand, while genetic distance of tree species was found to be the most important factor in driving the beta diversity pattern in the native stand.Conclusions
Soil nutrients influenced the beta diversity of AOA community in the middle-succeed stand more than that in the native stand, while vegetation is more important in the native stand. The substantial unexplained variations were possibly due to the effects of other unmeasured variables. Nevertheless, dispersal process is more important in controlling AOA community composition in the native stand, while processes associated with environmental heterogeneities are more important in the middle-succeed stand in this subtropical forest.994.
Stéphane Mombo Yann Foucault Frédéric Deola Irène Gaillard Sylvaine Goix Muhammad Shahid Eva Schreck Antoine Pierart Camille Dumat 《Journal of Soils and Sediments》2016,16(4):1214-1224
Purpose
At the global scale, gardening activities are often performed in urban areas with a historical background of pollution. In this study, a participatory program was developed with citizens concerned by gardening activities near a 50-year-old regulated lead recycling company, with the aim of co-constructing the tools for the assessment and management of potential sanitary risks induced by historic pollution with persistent (eco) toxic metals: lead and cadmium.Materials and methods
Soils and vegetables (lettuce, leek, celery, carrot, chard, pumpkin, and celeriac) samples were collected from four kitchen gardens neighboring a 50-year-old secondary lead smelter. Both total and in vitro human bioaccessible metal concentrations in the cultivated plants were measured in relation to soil characteristics.Results and discussion
The results showed that the soils of these gardens were slightly contaminated by metals (Pb, 77 to 236 mg kg?1; and Cd, 0.5 to 1 mg kg?1) in comparison with the natural geologic background. However, significant pollution of vegetables can occur especially with lead (Pb up to 9.8 mg kg?1 in lettuce) and certainly as a result of direct foliar transfer. The washing of plants before consumption is therefore recommended in the context of atmospheric fallout of ultrafine particles enriched with metals.Conclusions
Metal bioaccessibility measure integrates the influence of metal type, plant type, and soil physico-chemical properties. Based on the results, it is proposed that human bioaccessible fraction of metals may also be currently taken into account as well as total metal quantities and bioaccumulation factors in risk assessment studies performed in gardens. Overall, this study has led to reflections and functional recommendations aimed at reducing human exposure and to finally developing sustainable gardening practices.995.
Mohammad Wahsha Mandana Nadimi-Goki Claudio Bini 《Journal of Soils and Sediments》2016,16(4):1300-1305
Purpose
The present paper concerns the distribution and mobility of heavy metals (Cu, Pb, Zn and Fe) in the soils of some abandoned mine sites in Italy and their transfer to wild flora.Materials and methods
Soils and plants were sampled from mixed sulphide mine dumps in different parts of Italy, and the concentrations of heavy metals were determined.Results and discussion
The phytoremediation ability of Salix species (Salix eleagnos, Salix purpurea and Salix caprea), Taraxacum officinale and P?lantago major for heavy metals and, in particular, zinc was estimated. The results showed that soils affected by mining activities presented total Zn, Cu, Pb and Fe concentrations above the internationally recommended permissible limits. A highly significant correlation occurred between metal concentrations in soils.Conclusions
The obtained results confirmed the environmental effects of mine waste; exploring wild flora ability to absorb metals, besides metal exploitation, proved a useful tool for planning possible remediation projects.996.
Feng-He Wang Bin Zhao Fan Zhang Jay Gao Hao-Tian Hao Shengtian Zhang 《Journal of Soils and Sediments》2016,16(2):371-381
Purpose
The main objectives of the study were to (1) develop a one-step facile procedure for synthesizing a new chemical amendment agent with three chelating groups for solidifying multiple heavy metals, called sixthio guanidine acid (SGA), using guanidine hydrochloride and carbon disulfide as raw reactants and (2) assess its biodegradability, solidification effectiveness, and leachability in remedying soils contaminated with multiple heavy metals of various concentrations compared with other traditional amendment agents.Materials and methods
Polluted soil samples were collected near a metalliferous mining site of Qixiashan in the southeast of Nanjing, China. Their concentrations were determined at 22.15–320 mg kg?1 for As, 3.30–29.31 mg kg?1 for Cd, 115.66–158.65 mg kg?1 for Ni, 165.04–1677.06 mg kg?1 for Pb, and 355.6–2426.91 mg kg?1 for Zn. Biodegradability of SGA was assessed in accordance with GB/T 21831-2008 and OECD-301D. Total concentration of heavy metals was determined according to ISO11466:1995. A modified three-step sequential Community Bureau of Reference (BCR) extraction procedure was used to examine speciation of heavy metals in the soil sample, and concentrations of heavy metals were measured by using inductively coupling plasma optical emission spectrometry (ICP-OES). Leachate extraction tests were carried out before and after the soil sample was solidified with different amendments in accordance with HJ/T 557-2009.Results and discussion
It is found that the optimal conditions for SGA synthesis are a molar ratio of 4:1, a reaction temperature of 40 °C, and a reaction time of 2 h. Under such conditions, SGA yield is achieved as high as 91.5 %. The bioavailability and mobility of As, Cd, Ni, Pb, and Zn in highly contaminated soils can be reduced via using SGA. Our results indicate that SGA is nonbiodegradative and much more effective than other traditional chemical amendment agents in that it is highly effective in comprehensively solidifying As, Cd, Ni, and Pb.Conclusions
SGA has the potential for comprehensive in situ remediation of soils contaminated with several heavy metal elements of various concentration levels, and such findings may be used as a guide to design new chemical amendment agents for rehabilitating soils contaminated with heavy metals.997.
Wenming Ma Zhongwu Li Keyi Ding Bin Huang Xiaodong Nie Yinmei Lu Haibin Xiao Guangming Zeng 《Journal of Soils and Sediments》2016,16(6):1705-1717
Purpose
This study aims to explore the dynamics of the factors influencing soil organic carbon (SOC) sequestration and stability at erosion and deposition sites.Materials and methods
Thermal properties and dissolved aromatic carbon concentration along with Al, Fe concentration and soil specific surface area (SSA) were studied to 1 meter depth at two contrasting sites.Results and discussion
Fe, Al concentrations and SSA size increased with depth and were negatively correlated with SOC concentration at the erosion site (P?<?0.05), while at the deposition site, these values decreased with increasing depth and were positively correlated with SOC concentration (P?<?0.05). TG mass loss showed that SOC components in the two contrasting sites were similar, but the soils in deposition site contained a larger proportion of labile organic carbon and smaller quantities of stable organic carbon compared to the erosion site. SOC stability increased with soil depth at the erosion site. However, it was slightly variable in the depositional zone. Changes in SUVA254 spectroscopy values indicated that aromatic moieties of DOC at the erosion site were more concentrated in the superficial soil layer (0–20 cm), but at the deposition site they changed little with depth and the SUVA254 values less than those at the erosion site.Conclusions
Though large amounts of SOC accumulated in the deposition site, SOC may be vulnerable to severe losses if environmental conditions become more favorable for mineralization in the future due to accretion of more labile carbon. Deep soil layers at the erosion site (>30 cm deep) had a large carbon sink potential.998.
James F. Douglass Mark Radosevich Olli H. Tuovinen 《Journal of Soils and Sediments》2016,16(9):2263-2274
Purpose
The purpose of this study was to determine the first-order rate constants and half-lives of aerobic and anaerobic biomineralization of atrazine in soil samples from an agricultural farm site that had been previously used for mixing pesticide formulations and washing application equipment. Atrazine catabolic genes and atrazine-degrading bacteria in the soil samples were analyzed by molecular methods.Materials and methods
Biomineralization of atrazine was measured in soil samples with a [U-ring-14C]-atrazine biometer technique in soil samples. Enrichment cultures growing with atrazine were derived from soil samples and they were analyzed for bacterial diversity by constructing 16S rDNA clone libraries and sequencing. Bacterial isolates were also obtained and they were screened for atrazine catabolic genes.Results and discussion
The soils contained active atrazine-metabolizing microbial communities and both aerobic and anaerobic biomineralization of [U-ring-14C]-atrazine to 14CO2 was demonstrated. In contrast to aerobic incubations, anaerobic biometers displayed considerable differences in the kinetics of atrazine mineralization between duplicates. Sequence analysis of 16S rDNA clone libraries constructed from the enrichment cultures revealed a preponderance of Variovorax spp. (51 %) and Schlesneria (16 %). Analysis of 16S rRNA gene sequences from pure cultures (n?=?12) isolated from enrichment cultures yielded almost exclusively Arthrobacter spp. (83 %; 10/12 isolates). PCR screening of pure culture isolates for atrazine catabolic genes detected atzB, atzC, trzD, trzN, and possibly atzA. The presence of a complete metabolic pathway was not demonstrated by the amplification of catabolic genes among these isolates.Conclusions
The soils contained active atrazine-metabolizing microbial communities. The anaerobic biometer data showed variable response of atrazine biomineralization to external electron acceptor conditions. Partial pathways are inevitable in soil microbial communities, with metabolites linking into other catabolic and assimilative pathways of carbon and nitrogen. There was no evidence for the complete set of functional genes of the known pathways of atrazine biomineralization among the isolates.999.
Bożena Dębska Jacek Długosz Anna Piotrowska-Długosz Magdalena Banach-Szott 《Journal of Soils and Sediments》2016,16(10):2335-2343
Purpose
The application of bio-fertilizers is one of the management practices that can help to maintain or increase the content of organic matter (OM) and improve soil fertility in arable soils. While some results have been obtained in relation to the influence of bio-fertilizers on organic matter content, less in known about the fractional composition of humus.Materials and methods
The aim of this study was to determine the effects of the bio-fertilizer UGmax on soil total organic carbon (TOC), dissolved organic carbon (DOC), and the fractional composition of organic matter (C of humic acids (CHAs), C of fulvic acids (CFAs), and C in humins) in the humus horizon of an arable field. Measurements were taken in 2005 before the application of UGmax and in 2008, 3 years after its application, which was done in 2005, 2006, and 2007. Forty soil samples were taken in 2005 (the control year without UGmax), while 20 samples were taken after UGmax treatment and 20 from the control in 2008. Samples were always collected after the plants were harvested.Results and discussion
After the 3-year period of the experiment, the TOC content was 6.3 % higher in plots on which UGmax was applied in comparison to the control, while the DOC content was 0.19 percentage points lower after 3 years of bio-fertilizer use as compared to the initial year of the experiment. The contribution of DOC to TOC decreased significantly after the application of UGmax in comparison with the control. The content of CFAs and its contribution in the TOC pools in soil without UGmax was higher at the end of the experiment compared to the beginning, while there was an inverse relationship in the soil with the bio-fertilizer. In comparison with the control, organic matter in the soil treated with UGmax had a higher content of C of humic acids, C in humins, and higher CHAs/CFAs ratio.Conclusions
We conclude that the use of a bio-fertilizer that increases the stable fractions of organic matter provides evidence of an increase in the soil OM stability. In turn, the contribution of the organic matter fractions that are more resistant to decomposition is crucial for increasing soil carbon sequestration.1000.