共查询到20条相似文献,搜索用时 714 毫秒
1.
The following six pig slurries obtained after acidification and/or solid/liquid separation were used in the research: original
(S) and acidified (AS) pig slurry, nonacidified (LF) and acidified (ALF) pig slurry liquid fraction, and nonacidified (SF)
and acidified (ASF) pig slurry solid fraction. Laboratory incubations were performed to assess the effect of the application
of these slurries on N mineralization and CO 2 and N 2O emissions from a sandy soil. Acidification maintained higher NH 4
+-N contents in soil particularly in the ALF-treated soil where NH 4
+-N contents were two times higher than in LF-treated soil during the 55–171-day interval. At the end of the incubation (171 days),
32.9 and 24.2 mg N kg −1 dry soil were mineralized in the ASF- and SF-treated soils, respectively, but no mineralization occurred in LF- and S-treated
soils, although acidification decreased N immobilization in ALF- (−25.3 mg N kg −1 soil) and AS- (−12.7 mg N kg −1 soil) compared to LF- (−34.4 mg N kg −1 soil) and S-treated (−18.6 mg N kg −1 soil) soils, respectively. Most of the dissolved CO 2 was lost during the acidification process. More than 90% of the applied C in the LF-treated soil was lost during the incubation,
indicating a high availability of the added organic compounds. Nitrous oxide emissions occurred only after day 12 and at a
lower rate in soils treated with acidified than nonacidified slurries. However, during the first 61 days of incubation, 1,157 μg N
kg −1 soil was lost as N 2O in the AS-treated soil and only 937 in the S-treated soil. 相似文献
2.
This work aims to identify and characterize heavy metal contamination in a fluvial system from Cartagena–La Unión mining district
(SE Spain). In order to assess the dynamics of transport and the accumulation of heavy metals, sediments, surface water and
vegetation, samples along “El Avenque” stream were collected. The former direct dumps of wastes and the presence of tailing
ponds adjacent to the watercourse have contributed to the total contamination of the stream. Total Cd (103 mg kg −1), Cu (259 mg kg −1), Pb (26,786 mg kg −1) and Zn (9,312 mg kg −1) in sediments were above the limits of European legislation, being highest where tailing ponds are located. Bioavailable
metals were high (3.55 mg Cd kg −1, 6.45 mg Cu kg −1, 4,200 mg Pb kg −1 and 343 mg Zn kg −1) and followed the same trend than total contents. Metals in water were higher in sampling points close to ponds, exceeding
World Health Organization guidelines for water quality. There is a direct effect of solubilisation of sediment metals in water
with high contents of SO 42−, product of the oxidation of original sulphides. The mobility of metals varied significantly with shifts in pH. Downstream,
available and soluble metals concentrations decreased mainly due to precipitation by increments in pH. As a general pattern,
no metal was bioaccumulated by any tested plant. Thus, native vegetation has adopted physiological mechanisms not to accumulate
metals. This information allows the understanding of the effect of mining activities on stream contamination, enforcing the
immediate intervention to reduce risks related to metals’ mobility. 相似文献
3.
Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching,
denitrification, and nitrous oxide (N 2O) emission. A laboratory incubation experiment was conducted for 84 days under controlled conditions (24°C and moisture content
55% of water-holding capacity) to study the influence of sugarcane, maize, sorghum, cotton and lucerne residues, and mineral
N addition, on N mineralization–immobilization and N 2O emission. Residues were added at the rate of 3 t C ha −1 to soil with, and without, 150 kg urea N ha −1. The addition of sugarcane, maize, and sorghum residues without N fertilizer resulted in a significant immobilization of
soil N. Amended soil had significantly ( P < 0.05) lower NO 3−–N, which reached minimum values of 2.8 mg N kg −1 for sugarcane (at day 28), 10.3 mg N kg −1 for maize (day 7), and 5.9 mg N kg −1 for sorghum (day 7), compared to 22.7 mg N kg −1 for the unamended soil (day 7). During 84 days of incubation, the total mineral N in the residues + N treatments were decreased
by 45 mg N kg −1 in sugarcane, 34 mg kg −1 in maize, 29 mg kg −1 in sorghum, and 16 mg kg −1 in cotton amended soil compared to soil + N fertilizer, although soil NO 3−–N increased by 7 mg kg −1 in lucerne amended soil. The addition of residues also significantly increased amended soil microbial biomass C and N. Maximum
emissions of N 2O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the
cumulative N 2O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N 2O emission was significantly and positively correlated with NO 3−–N ( r = 0.92, P < 0.01) and total mineral N ( r = 0.93, P < 0.01) after 84 days of incubation, and had a weak but significant positive correlation with cumulative CO 2 in the first 3 and 5 days of incubation ( r = 0.59, P < 0.05). 相似文献
4.
Surface sediments (0–5 cm) were analysed to provide information on levels, spatial trends and sources of the 16 USEPA polycyclic
aromatic hydrocarbons (PAH), 15 polychlorinated biphenyls (PCBs) and trace metals (copper, chromium, mercury, nickel and zinc)
in channel and wetland habitats of Pialassa Baiona lagoon (Italy). The highest levels of PAHs, PCBs and Hg (3,032–87,150,
n.d.–3,908 and 1.3–191 mg kg −1) were mainly found at channel habitats close to industrial sources. Pyrogenic PAH inputs were significant, with a predominance
of four-ring PAHs and combustion-related PAHs in both channel and wetland habitats. Among PCB congeners, chlorination class
profiles show that penta- and hexachlorinated PCBs are the most prevalent homologues accounting for approximately 33% and
47% of the total PCB concentrations in channel sediments. Total toxicity equivalent factors (TEQs) of potentially carcinogenic
PAHs varied from 348 to 7,879 μg kg −1 and from 4.3 to 235 μg kg −1 in channel and wetland sediments; calculated TEQs for dioxin-like PCB congeners at channel habitats ranged from n.d. to 86.7 μg kg −1. Comparison of PAHs, PCBs and metal levels with Sediment Quality Guidelines suggests that more concern should be given to
the southern area of the lagoon for potential risks of carcinogenic PAHs, dioxin-like PCBs and mercury. 相似文献
5.
Purpose The purpose of the present study was to investigate the composition and structure of microbial communities in rhizosphere
soils in response to the presence of Aroclor 1242 with low (8 mg kg −1 soil) and high (16 mg kg −1 soil) concentrations in the hope to provide more information on potential dissipation of polychlorinated biphenyls (PCBs)
at contaminated sites. 相似文献
6.
Red lead (Pb 3O 4) has been used extensively in the past as an anti-corrosion paint for the protection of steel constructions. Prominent examples
being some of the 200,000 high-voltage pylons in Germany which have been treated with red lead anti-corrosion paints until
about 1970. Through weathering and maintenance work, paint compounds and particles are deposited on the soils beneath these
constructions. In the present study, six such “pylon soils” were investigated in order to characterize the plant availability
and plant uptake of Pb, Cd, and Zn. For comparison, three urban soils with similar levels of heavy metal contamination were
included. One phase extractions with 1 M NH 4NO 3, sequential extractions (seven steps), and extractions at different soil pH were used to evaluate the heavy metal binding
forms in the soil and availability to plants. Greenhouse experiments were conducted to determine heavy metal uptake by Lolium multiflorum and Lactuca sativa var. crispa in untreated and limed red lead paint contaminated soils. Concentrations of Pb and Zn in the pylon soils were elevated with
maximum values of 783 mg Pb kg −1 and 635 Zn mg kg −1 while the soil Cd content was similar to nearby reference soils. The pylon soils were characterized by exceptionally high
proportions of NH 4NO 3-extractable Pb reaching up to 17% of total Pb. Even if the relatively low pH of the soils is considered (pH 4.3–4.9), this
appears to be a specific feature of the red lead contamination since similarly contaminated urban soils have to be acidified
to pH 2.5 to achieve a similarly high Pb extractability. The Pb content in L. multiflorum shoots reached maximum values of 73 mg kg −1 after a cultivation time of 4 weeks in pylon soil. Lime amendment reduced the plant uptake of Pb and Zn significantly by
up to 91%. But L. sativa var. crispa cultivated on soils limed to neutral pH still contained critical Pb concentrations (up to 0.6 mg kg −1 fresh weight). Possible mechanisms for the exceptionally high plant availability of soil Pb derived from red lead paint are
discussed. 相似文献
7.
Fixed NH 4+ (NH 4+
f) and fixation and defixation of NH 4+ in soils have been the subject of a number of investigations with conflicting results. The results vary because of differences
in methodology, soil type, mineralogical composition, and agro-climatic conditions. Most investigators have determined NH 4+
f using strong oxidizing agents (KOBr or KOH) to remove organic N and the remaining NH 4+
f does not necessarily reflect the fraction that is truly available to plants. The content of native NH 4+
f in different soils is related to parent material, texture, clay content, clay mineral composition, potassium status of the
soil and K saturation of the interlayers of 2:1 clay minerals, and moisture conditions. Evaluation of the literature shows
that the NH 4+
f-N content amounts to 10–90 mg kg −1 in coarse-textured soils (e.g., diluvial sand, red sandstone, granite), 60–270 mg kg −1 in medium-textured soils (loess, marsh, alluvial sediment, basalt) and 90–460 mg kg −1 in fine-textured soils (limestone, clay stone). Variable results on plant availability of NH 4+
f are mainly due to the fact that some investigators distinguished between native and recently fixed NH 4+ while others did not. Recently fixed NH 4+ is available to plants to a greater degree than the native NH 4+
f, and soil microflora play an important role in the defixation process. The temporal changes in the content of recently fixed
NH 4+ suggest that it is actively involved in N dynamics during a crop growth season. The amounts of NH 4+ defixed during a growing season varied greatly within the groups of silty (20–200 kg NH 4+-N ha −1 30 cm −1) as well as clayey (40–188 kg NH 4+-N ha −1 30 cm −1) soils. The pool of recently fixed NH 4+ may therefore be considered in fertilizer management programs for increasing N use efficiency and reducing N losses from
soils. 相似文献
8.
The objective of this study was to investigate the effects of adding different rates of diethylenetriamine pentaacetate (DTPA)
at different concentrations (0, 0.5, 1, and 5 mmol kg −1) and ethylenediamine disuccinate (EDDS) at 0, 5, 7.5, and 10 mmol kg −1 on the capacity of Brussels sprouts plants to take up Se from soils contaminated with 0, 5, 10, and 15 mg kg −1 NaSeO 4, under a greenhouse conditions. Results indicated that the application of DTPA and EDDS to Se-contaminated soils significantly
affect plant Se concentration, Se uptake, and dry matter yield of plants. Se concentration in the plant leaves, stems, and
roots increased with increase in DTPA and EDDS application doses, but total Se uptake increased from 0 to 1.0 and 7.5 mmol kg −1 DTPA and EDDS application doses, respectively, and decreased after those levels due to toxic Se concentration for plant.
Most plant available fractions and the carbonate, metal oxide, and organic matter-bound fractions increased linearly with
Se application. At all DTPA and EDDS application rates, the Se concentrations in the leaves were about two to three times
higher than those in the roots and about three to four times higher than those in the stems. This study suggests that the
above-ground organs like leaf and shoots of Brussels sprouts can effectively be used in the removal of Se from soils contaminated
with Se. Under the conditions in this experiment, Brussels sprouts were capable of removing 0.9–1.8 mg Se pot −1 when harvested at maturity without any chelating agent take into consideration one growing season per year. Based on the
data of present experiment, it would be necessary to approximately 57–67 growing seasons without EDDS and EDTA to remove all
total Se from polluted soil. Selenium removal can be further increased 12- to 20-fold with 7.5 mmol kg −1 EDDS and 1.0 mmol kg −1 DTPA application, respectively. 相似文献
9.
Modern agricultural systems have to provide enough micronutrient output to meet all the nutritional needs of people. Accordingly,
knowledge on micronutrient status in soil and crop edible tissues is necessary. This study was carried out to investigate
zinc (Zn), iron (Fe), manganese (Mn), and copper (Cu) concentration of calcareous paddy soil and the relative rice grain.
Rice crops (straw, hull, and grain) and associated surface soils (0–25 cm) were collected from 136 fields and analyzed for
total and diethylene triamine pentaacetic acid (DTPA) available Zn, Fe, Mn, and Cu. The DTPA-Zn concentration in more than
50% of paddy soils was less than its critical deficiency concentration (2 mg kg −1), while the concentrations of DTPA Fe, Mn, and Cu were sufficient. The grain Zn concentration of more than 54% of the rice
samples was less than 20 mg kg −1. About 55% and 49% of the rice samples were deficient in Mn and Cu, respectively, while the Fe concentration in rice grains
was sufficient. A significant negative correlation was found between the CaCO 3 content and soil DTPA-extractable Zn, Fe, Mn, and Cu. There were significant relationships between the total soil phosphorus
and DTPA-extractable micronutrient concentrations. By considering the average daily rice consumption of 110 g per capita,
the Zn, Fe, Mn, and Cu intake from rice consumption was estimated to be 2.4, 7.7, 1.6, and 0.7 mg for adults, respectively. 相似文献
10.
Purpose The effects of the addition of an acidic fertilizer solution and/or slaked lime (5.5 g Ca(OH) 2 kg −1) on a slightly acidic shooting range soil (pH 6.1, % organic carbon 5.4) with moderate metal (e.g., 620 mg kg −1 Pb) and metalloid (17 mg kg −1 Sb) concentrations on metal and Sb solubility and plant accumulation were investigated. 相似文献
11.
The interactive impacts of arbuscular mycorrhizal fungi (AMF, Glomus intraradices) and earthworms ( Aporrectodea trapezoides) on maize ( Zea mays L.) growth and nutrient uptake were studied under near natural conditions with pots buried in the soil of a maize field.
Treatments included maize plants inoculated vs. not inoculated with AMF, treated or not treated with earthworms, at low (25 mg kg −1) or high (175 mg kg −1) P fertilization rate. Wheat straw was added as feed for earthworms. Root colonization, mycorrhiza structure, plant biomass
and N and P contents of shoots and roots, soil available P and NO 3−–N concentrations, and soil microbial biomass C and N were measured at harvest. Results indicated that mycorrhizal colonization
increased markedly in maize inoculated with AMF especially at low P rate, which was further enhanced by the addition of earthworms.
AMF and earthworms interactively increased maize shoot and root biomass as well as N and P uptake but decreased soil NO 3−–N and available P concentrations at harvest. Earthworm and AMF interaction also increased soil microbial biomass C, which
probably improved root N and P contents and indirectly increased the shoot N and P uptake. At low P rate, soil N mobilization
by earthworms might have reduced potential N competition by arbuscular mycorrhizal hyphae, resulting in greater plant shoot
and root biomass. Earthworms and AMF interactively enhanced soil N and P availability, leading to greater nutrient uptake
and plant growth. 相似文献
12.
Laboratory incubation study showed that iron pyrites retarded nitrification of urea-derived ammonium (NH 4
+), the effect being greatest at the highest level (10000 mg kg –1 soil). Nitrification inhibition with 10000 mg pyrite kg –1 soil, at the end of 30 days, was 40.3% compared to 55.9% for dicyandiamide (DCD). The inhibitory effect with lower rates
of pyrite (100–500 mg kg –1) lasted only up to 9 days. Urea+pyrite treatment was also found to have higher exchangeable NH 4
+-N compared to urea alone. DCD-amended soils had the highest NH 4
+-N content throughout. Pyrite-treated soils had about 7–86% lower ammonia volatilization losses than urea alone. Total NH 3 loss was the most with urea+DCD (7.9% of applied N), about 9% more than with urea alone.
Received: 11 November 1995 相似文献
13.
The steel-making slag (SMS), a by-product of steel manufacturing process with an alkaline pH (11–12) and high amount of iron
(Fe) and calcium (Ca) oxides, was used to reduce arsenic (As) phytoextractability. The by-product was selected as an alternative
to commercial Fe oxides, which can decrease plant uptake, but they are expensive if used as amendments of contaminated arable
soils. SMS was applied at rates 0, 2, 4, and 8 Mg ha −1 to an As (1 N HCl-extractable As 25 mg kg −1) contaminated soil prepared by mixing non-contaminated soil and mine tailings and cropped to radish ( Raphanus sativa L.) seeding. Calcium hydroxide (Ca(OH) 2), a common liming material in Korea, was applied at the same rates for comparison. Steel-making slag more effectively suppressed
radish As uptake and increased yield than Ca(OH) 2 due to stronger As immobilization because it significantly increased extractable Fe concentration and decreased extractable
As. The SMS-treated soil showed an apparent increase in As chemisorbed by Fe and Al oxides and hydroxides of surface soil,
As associated at the Fe and Al oxides and hydroxides of internal surfaces of soil aggregates, and Ca-associated As. The steel-making
slag can be a good soil amendment to suppress As phytoextractability and improve nutrient balance in As-contaminated soil. 相似文献
14.
The effect of reduced tillage (RT) on nitrous oxide (N 2O) emissions of soils from fields with root crops under a temperate climate was studied. Three silt loam fields under RT agriculture
were compared with their respective conventional tillage (CT) field with comparable crop rotation and manure application.
Undisturbed soil samples taken in September 2005 and February 2006 were incubated under laboratory conditions for 10 days.
The N 2O emission of soils taken in September 2005 varied from 50 to 1,095 μg N kg −1 dry soil. The N 2O emissions of soils from the RT fields taken in September 2005 were statistically ( P < 0.05) higher or comparable than the N 2O emissions from their respective CT soil. The N 2O emission of soils taken in February 2006 varied from 0 to 233 μg N kg −1 dry soil. The N 2O emissions of soils from the RT fields taken in February 2006 tended to be higher than the N 2O emissions from their respective CT soil. A positive and significant Pearson correlation of the N 2O–N emissions with nitrate nitrogen (NO 3
−–N) content in the soil was found ( P < 0.01). Leaving the straw on the field, a typical feature of RT, decreased NO 3
−–N content of the soil and reduced N 2O emissions from RT soils. 相似文献
15.
The abandonment of cultivated wetland soil increased the contents of light fraction organic matter (LFOM), heavy fraction
organic matter (HFOM) and soil organic matter (SOM). The LFOM and HFOM content increased to 13.3 g kg −1 and 62.4 g kg −1 after 5 years whereas they were 8.4 and 47.9 g kg −1 after 9 years of cropping, respectively. Fourteen years after abandonment, HFOM content increased to 104.3 g kg −1. LFOM was positively correlated with HFOM ( p < 0.001). A Langmuir equation was used to calculate the highest HFOM value. The value for the natural wetland soil was closed
to this theoretical value (140.8 g kg −1). After 14 years of abandonment, the HFOM maximum (HFOM Max) value was lower than the equilibrium value suggesting that a further increase in HFOM can occur after abandonment. Assuming
a linear accumulation (3.87 Mg C ha −1yr −1), it would take approximately 24 years after the abandonment to reach the HFOM Max value. 相似文献
16.
Seasonal drought in tropical agroecosystems may affect C and N mineralization of organic residues. To understand this effect,
C and N mineralization dynamics in three tropical soils (Af, An 1, and An 2) amended with haricot bean (HB; Phaseolus vulgaris L.) and pigeon pea (PP; Cajanus cajan L.) residues (each at 5 mg g −1 dry soil) at two contrasting soil moisture contents (pF2.5 and pF3.9) were investigated under laboratory incubation for 100–135 days.
The legume residues markedly enhanced the net cumulative CO 2–C flux and its rate throughout the incubation period. The cumulative CO 2–C fluxes and their rates were lower at pF3.9 than at pF2.5 with control soils and also relatively lower with HB-treated than
PP-treated soil samples. After 100 days of incubation, 32–42% of the amended C of residues was recovered as CO 2–C. In one of the three soils (An 1), the results revealed that the decomposition of the recalcitrant fraction was more inhibited by drought stress than easily
degradable fraction, suggesting further studies of moisture stress and litter quality interactions. Significantly ( p < 0.05) greater NH 4+–N and NO 3−–N were produced with PP-treated (C/N ratio, 20.4) than HB-treated (C/N ratio, 40.6) soil samples. Greater net N mineralization
or lower immobilization was displayed at pF2.5 than at pF3.9 with all soil samples. Strikingly, N was immobilized equivocally
in both NH 4+–N and NO 3−–N forms, challenging the paradigm that ammonium is the preferred N source for microorganisms. The results strongly exhibited
altered C/N stoichiometry due to drought stress substantially affecting the active microbial functional groups, fungi being
dominant over bacteria. Interestingly, the results showed that legume residues can be potential fertilizer sources for nutrient-depleted
tropical soils. In addition, application of plant residue can help to counter the N loss caused by leaching. It can also synchronize
crop N uptake and N release from soil by utilizing microbes as an ephemeral nutrient pool during the early crop growth period. 相似文献
17.
PurposeIdentification of phosphorus (P) species is essential to understand the transformation and availability of P in soil. However, P species as affected by land use change along with fertilization has received little attention in a sub-alpine humid soil of Tibet plateau. Materials and methodsIn this study, we investigated the changes in P species using Hedley sequential fractionation and liquid-state 31P-NMR spectroscopy in soils under meadow (M) and under cropland with (CF) or without (CNF) long-term fertilization for 26 years in a sub-alpine cold-humid region in Qinghai–Tibet plateau. Results and discussionLand-use change and long-term fertilization affected the status and fractions of P. A strong mineralization of organic P (OP) was induced by losing protection of soil organic matter (SOM) and Fe and Al oxides during land-use change and resulted in an increase of orthophosphate (from 56.49 mg kg?1 in M soils to 130.07 mg kg?1 in CNF soils) and great decreases of orthophosphate diesters (diester-P, from 23.35 mg kg?1 in M soils to 10.68 mg kg?1 in CNF soils) and monoesters (from 336.04 mg kg?1 in M soils to 73.26 mg kg?1 in CNF soils). Long-term fertilization boosted P supply but failed to reclaim soil diester-P (from 10.68 mg kg?1 in CNF soils to 7.79 mg kg?1 in CF soils). This may be due to the fragile protection from the combination of SOM with diester-P when long-term fertilization had only improved SOM in a slight extent. ConclusionsThese results suggest that SOM plays an important role in the soil P cycling and prevents OP mineralization and losses from soil. It is recommended that optimization of soil nutrient management integrated with SOM was required to improve the P use efficiency for the development of sustainable agriculture. 相似文献
18.
Incidental losses of dissolved reactive phosphorus (DRP) to a surface waterbody originate from direct losses during land application
of fertilizer, or where a rainfall event occurs immediately thereafter. Another source is the soil. One way of immobilising
DRP in runoff before discharge to a surface waterbody, is to amend soil within the edge of field area with a high phosphorus
(P) sequestration material. One such amendment is iron ochre, a by-product of acid mine drainage. Batch experiments utilising
two grassland soils at two depths (topsoil and sub-soil), six ochre amendment rates (0, 0.15, 1.5, 7.5, 15 and 30 g kg −1 mass per dry weight of soil) and five P concentrations (0, 5, 10, 20 and 40 mg L −1) were carried out. A proportional equation, which incorporated P sources and losses, was developed and used to form a statistical
model. Back calculation identified optimal rates of ochre amendment to soil to ameliorate a specific DRP concentration in
runoff. Ochre amendment of soils (with no further P inputs) was effective at decreasing DRP concentrations to acceptable levels.
A rate of 30 g ochre kg −1 soil was needed to decrease DRP concentrations to acceptable levels for P inputs of ≤10 mg L −1, which represents the vast majority of cases in grassland runoff experiments. However, although very quick and sustained
metal release above environmental limits occurred, which makes it unfeasible for use as a soil amendment to control P release
to a waterbody, the methodology developed within this paper may be used to test the effectiveness and feasibility of other
amendments. 相似文献
19.
In this study, the effects of 1 h aeration, nitrogen gas N 2(g) sparging (15 and 30 min) and increasing ferric ions (Fe +3) as FeSO 4 (10, 20 and 50 mg L −1) and Fe 3O 4 nanoparticles (1, 2 and 4 g L −1) concentrations on three less hydrophobic and three more hydrophobic polycyclic aromatic hydrocarbons (PAHs) and toxicity
removals from a petrochemical industry in Izmir (Turkey) were investigated in a sonicator with a power of 650 W and an ultrasound
frequency of 35 kHz; 1 h aeration increased the yields in benzo[ b]fluoranthene, benzo[ k]fluoranthene and benzo[ a]pyrene PAHs (less hydrophobic) from 62% to 67% to around 95–97% after 150 min sonication at 60°C. However, 1 h aeration did
not contribute to the yields of more hydrophobic PAHs (indeno[1,2,3- cd]pyrene, dibenz[ a, h]anthracene, benzo[ g, h, i]perylene). The maximum yields were obtained at acidic and alkaline pH for more and less hydrophobic PAHs, respectively, after
60 and 120 min sonication at 30°C; 30 min N 2(g) sparging, 50 mg L −1 Fe +3 increased the yields of less hydropobic PAHs after 150 min sonication at 60°C. Two milligrams per liter of Fe 3O 4 nanoparticles increased both less (87–88%) and more (96–98%) hydrophobic PAH yields. The Daphnia magna acute toxicity test showed that the toxicity decreased significantly with an hour aeration, 30 min N 2(g) sparging, 50 mg L −1 Fe +3 and 2 g L −1 Fe 3O 4 nanoparticles at 60°C after 120 and 150 min sonications. Vibrio fischeri was found to be more resistant to the sonicated samples than D. magna. Significant correlations were found between the physicochemical properties of sonicated PAHs and acute toxicities both organisms. 相似文献
20.
Copper-based fungicides have been applied in apple orchards for a long time, which has resulted in increasing soil Cu concentration. However, the microbial and enzyme properties of the orchard soils remain poorly understood. This study aimed to evaluate the effect of long-term application of Cu-based fungicides on soil microbial (microbial biomass carbon (C mic), C mineralization, and specific respiration rate) and enzyme (urease, acid phosphatase, and invertase activities) properties in apple orchards. Soil samples studied were collected from apple orchards 5, 15, 20, 30, and 45 years old, and one adjacent forest soil as for reference. The mean Cu concentrations of orchard soils significantly increased with increasing orchard ages ranging from 21.8 to 141 mg kg −1, and the CaCl 2-extractable soil Cu concentrations varied from 0.00 to 4.26 mg kg −1. The soil mean C mic values varied from 43.6 to 116 mg kg −1 in the orchard soils, and were lower than the value of the reference soil (144 mg kg −1). The ratio of soil C mic to total organic C (C org) increased from 8.10 to 18.3 mg C mic g −1 C org with decreasing orchard ages, and was 26.1 mg C mic g −1 C org for the reference soil. A significant correlation was observed between total- or CaCl 2-extractable soil Cu and soil C mic or C mic/C org, suggesting that the soil Cu was responsible for the significant reductions in C mic and C mic/C org. The three enzyme activity assays also showed the similar phenomena, and declined with the increasing orchard ages. The mean soil C mineralization rates were elevated from 110 to 150 mg CO 2-C kg −1 soil d −1 compared with the reference soil (80 mg CO 2-C kg −1 soil d −1), and the mean specific respiration rate of the reference soil (0.63 mg CO 2-C mg −1 biomass C d −1) was significantly smaller than the orchard soils from 1.19 to 3.55 mg CO 2-C mg −1 biomass C d −1. The soil C mineralization rate and the specific respiration rate can be well explained by the CaCl 2-extractable soil Cu. Thus, the long-term application of copper-based fungicides has shown adverse effects on soil microbial and enzyme properties. 相似文献
|