Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 13 de 13
Filter
2.
Anticancer Res ; 31(6): 2291-5, 2011 Jun.
Article in English | MEDLINE | ID: mdl-21737654

ABSTRACT

AIM: To compare 5-year survival of patients with a single hepatocellular carcinoma≤3 cm randomly assigned to receive percutaneous ethanol injection or radiofrequency ablation. PATIENTS AND METHODS: A total of 285 patients (192 males, mean age 70 years), with a single hepatocellular carcinoma (mean diameter 2.2 cm) were randomly assigned to receive percutaneous ethanol injection (n=143) or radiofrequency ablation (n=142). The primary endpoint of the study was 5-year survival. RESULTS: Overall 143 patients underwent percutaneous ethanol injection and 128 radiofrequency ablation. In consideration of segmental location, in fact, 14 patients with 14 hepatocellular carcinomas could not be treated with established radiofrequency and were treated with percutaneous ethanol injection; these patients were not included in the survival evaluation. In the percutaneous ethanol injection and in the radiofrequency ablation groups, 3- and 5-year survival rates of 74% and 68%, and 78% and 68%, and 79% and 70% [corrected] respectively, were observed (p=n.s). In the percutaneous ethanol injection group, 3- and 5-year local recurrence rates were 9.4% and 12.8% respectively; in the radiofrequency group, the 3 and 5 years local recurrence rates were 7.8% and 11.7%, respectively (p=n.s.). The overall costs of percutaneous ethanol injection and radiofrequency ablation were 1359 Euros and 171.000 Euros, respectively (p<0.0001) CONCLUSION: Percutaneous ethanol injection and radiofrequency ablation conferred similar 5-year survival. Feasibility is not the same for both procedures. Percutaneous ethanol injection is much cheaper than radiofrequency ablation and should be considered whether in poor and rich countries.


Subject(s)
Carcinoma, Hepatocellular/complications , Carcinoma, Hepatocellular/therapy , Catheter Ablation/methods , Ethanol/administration & dosage , Liver Cirrhosis/complications , Liver Neoplasms/complications , Liver Neoplasms/therapy , Administration, Cutaneous , Aged , Carcinoma, Hepatocellular/drug therapy , Carcinoma, Hepatocellular/surgery , Catheter Ablation/adverse effects , Catheter Ablation/economics , Cost-Benefit Analysis , Drug Costs , Ethanol/adverse effects , Ethanol/economics , Feasibility Studies , Female , Humans , Liver Neoplasms/drug therapy , Liver Neoplasms/surgery , Male , Neoplasm Recurrence, Local/pathology , Survival Rate
3.
In Vivo ; 23(6): 1027-30, 2009.
Article in English | MEDLINE | ID: mdl-20023251

ABSTRACT

BACKGROUND: Amoebic liver abscess (ALA) is the most common extraintestinal complication of colonic amebiasis. In recent decades its incidence in developed European countries has significantly increased because of travel and immigration of individuals from highly endemic areas. We report our 29-year experience in echo-guided percutaneous needle/catheter drainage (EPND/EPCD) of ALA. PATIENTS AND METHODS: From May 1979 to November 2007, 68 ALA corresponding to 56 patients were diagnosed at our Department. All patients were treated with a metronidazole plus EPND/EPCD approach. RESULTS: The majority of the cases did not need more than two echo-guided punctures. Two patients, both male immigrants (HIV-negative), had unmodified lesions after two EPNDs: catheter drainage was performed. A quick worsening of their clinical conditions and onset of neurological symptoms occurred; in both patients, computed tomography (CT) revealed a brain abscess. Intravenous medical therapy was started, but both died 4 and 3 days, respectively, after the onset of neurological symptoms (overall mortality rate: 3.57%). CONCLUSION: The unfavorable outcome of two cases is a rare example of failure of percutaneous therapy of ALA. Mortality is a possible event even in a non-endemic area such as Italy. More observational data are needed to confirm the possibility of a new epidemiological trend.


Subject(s)
Liver Abscess, Amebic/epidemiology , Adult , Antiprotozoal Agents/therapeutic use , Brain Abscess/parasitology , Combined Modality Therapy , Drainage/methods , Female , Humans , Italy/epidemiology , Liver Abscess, Amebic/pathology , Liver Abscess, Amebic/therapy , Male , Metronidazole/therapeutic use , Therapeutic Irrigation/instrumentation , Therapeutic Irrigation/methods , Tomography, X-Ray Computed , Transients and Migrants , Ultrasonography, Interventional/methods
4.
J Ultrasound ; 12(1): 32-7, 2009 Mar.
Article in English | MEDLINE | ID: mdl-23396977

ABSTRACT

INTRODUCTION: We report our preliminary results of radiofrequency (RF) ablation of hepatocellular carcinoma (HCC) and neoplastic portal thrombus (NPT) in cirrhotic patients. METHODS: Ten patients (7 males and 3 females; mean age 68 yrs) with 10 HCC nodules (37-49 mm) extended into the main portal vein (MPV) underwent RF ablation. Diagnosis of NPT was achieved by fine-needle biopsy. RF ablation was performed firstly on the NPT and then on the HCC. RF ablation was considered successful when complete necrosis of the HCC and complete recanalization of the MPV were achieved. HCC necrosis was evaluated using contrast-enhanced CT. Recanalization of the portal vessels (PV) was analyzed using Color Doppler (CD). RF ablation was performed under ultrasonographic (US) guidance using a perfused electrode needle. RESULTS: Complete necrosis of the HCC with complete recanalization of the PV was observed in 7 patients (success rate: 70%). In the remaining 3, necrosis of the HCC ranged from 70% to 95%, and recanalization of the PV was not complete. No major complications occurred. In 2 cases, mild ascites and increased aspartate aminotransferase/alanine aminotransferase (AST/ALT) values were observed. The follow-up ranged from 4 to 24 months; 1 and 2-year survival rates were 77% and 77%, respectively. At the last follow-up, the 7 successful patients were alive and the portal system was still patent. The 3 unsuccessful patients died within 5 months due to progressive disease. CONCLUSION: RF ablation can destroy HCC and NPT achieving a high rate of efficacy and low rate of complications. However, to confirm these results a control group and a longer follow-up are required.

5.
Sci Total Environ ; 368(1): 19-29, 2006 Sep 01.
Article in English | MEDLINE | ID: mdl-16781764

ABSTRACT

The Brazilian Amazon has experienced considerable colonization in the last few decades. Family agriculture based on slash-and-burn enables millions of people to live in that region. However, the poor nutrient content of most Amazonian soils requires cation-rich ashes from the burning of the vegetation biomass for cultivation to be successful, which leads to forest ecosystem degradation, soil erosion and mercury contamination. While recent studies have suggested that mercury present in soils was transferred towards rivers upon deforestation, little is known about the dynamics between agricultural land-use and mercury leaching. In this context, the present study proposes an explanation that illustrates how agricultural land-use triggers mercury loss from soils. This explanation lies in the competition between base cations and mercury in soils which are characterized by a low adsorption capacity. Since these soils are naturally very poor in base cations, the burning of the forest biomass suddenly brings high quantities of base cations to soils, destabilizing the previous equilibrium amongst cations. Base cation enrichment triggers mobility in soil cations, rapidly dislocating mercury atoms. This conclusion comes from principal component analyses illustrating that agricultural land-use was associated with base cation enrichment and mercury depletion. The overall conclusions highlight a pernicious cycle: while soil nutrient enrichment actually occurs through biomass burning, although on a temporary basis, there is a loss in Hg content, which is leached to rivers, entering the aquatic chain, and posing a potential health threat to local populations. Data presented here reflects three decades of deforestation activities, but little is known about the long-term impact of such a disequilibrium. These findings may have repercussions on our understanding of the complex dynamics of deforestation and agriculture worldwide.


Subject(s)
Conservation of Natural Resources , Mercury/analysis , Soil Pollutants/analysis , Agriculture , Brazil , Cations/analysis , Environmental Monitoring , Trees
6.
Suppl Tumori ; 4(3): S46-7, 2005.
Article in Italian | MEDLINE | ID: mdl-16437896

ABSTRACT

The primitive tumors of the liver are relatively rare in the Western countries (around the 0.7% of all the neoplasms) while they present more elevated incidence in Africa and in the South Asian East. While the hepatocellular carcinoma rises up in the 50-70% of the cases in livers cirrosis, this correlation is not valid for the form of carcinoma to departure from the learned intra and extra biliar. The etiology of the intrahepatic colangiocarcinoma (CC) stays unknown. They have stayed observe, on the other hand, of the conditions sometimes correlated to the development of the CC (Carolí morbs, ulcerative colitis, asbestosis). The CC usually rises up from the epithelial cells of surface that delimit the biliary ducts, although different studies suggest that these tumors can also originate from the learned smaller biliary ducts, from the hepatic cysts of the policistic illness and from the complexes of von Meyenburg. The low incidence of the CC, the clinical atypical debut, the not facility of a precise diagnosis have aroused our interest so that the present job wants to be a modest scientific contribution to this type of pathology.


Subject(s)
Bile Duct Neoplasms , Bile Ducts, Intrahepatic , Cholangiocarcinoma , Adult , Bile Duct Neoplasms/diagnosis , Bile Duct Neoplasms/surgery , Cholangiocarcinoma/diagnosis , Cholangiocarcinoma/surgery , Female , Humans
7.
Abdom Imaging ; 28(5): 602-8, 2003.
Article in English | MEDLINE | ID: mdl-14628859

ABSTRACT

BACKGROUND: We evaluated the efficacy of abdominal ultrasound (US) and fine-needle aspiration biopsy (FNAB) in the diagnosis of disseminated mycobacteriosis (DM) in acquired immunodeficiency syndrome (AIDS). METHODS: Twelve AIDS patients (nine male, three female; age range, 22-43 years) with DM underwent abdominal US within 2 days after admission with 3.5- to 5-MHz convex probes and a 7.5-MHz linear probe. All patients underwent FNAB of one or two enlarged abdominal lymph nodes. Eight patients underwent FNAB of the spleen. The aspirated specimens were stained with acid fast for quick examination and cultured for isolation of mycobacteria. RESULTS: Abdominal US showed enlarged, hypoechoic, round or oval, abdominal lymph nodes (diameter, 10-35 mm; mean, 18 mm) in all patients; splenomegaly (spleen diameter, 14-22 cm; mean, 16.8 mm) in all patients; numerous splenic abscesses (diameter, 3-20 mm) in nine patients; hepatomegaly (right hepatic lobe thickness, 14.5-17 cm) in all patients; small intestinal wall thickening in five patients (maximum bowel wall thickness, 7-15 mm); mild to moderate ascites in six patients; pleural effusion in four patients; bilateral enlargement of the kidneys with hyperechogenicity of the cortex in three patients; and a retroperitoneal tubercular abscess in one patient. No complication occurred after FNAB of lymph nodes and spleens. Fast-acid stain of spleen and/or lymph node FNAB specimens allowed early diagnosis of mycobacteriosis in 12 of 12 cases (100%). Cultures of lymph node aspirates grew mycobacteria in six of 12 patients (50%). Spleen aspirates grew mycobacteria in nine of nine patients (100%). Blood cultures were positive in four of 12 patients (33%). Mycobacterium tuberculosis was diagnosed in six patients and M. avium in five. CONCLUSION: Abdominal US features can suggest DM in AIDS patients. Spleen and/or lymph node FNAB indicated the specific diagnosis in 100% of patients.


Subject(s)
AIDS-Related Opportunistic Infections/diagnostic imaging , Mycobacterium avium-intracellulare Infection/diagnostic imaging , Peritonitis, Tuberculous/diagnostic imaging , Tuberculosis, Gastrointestinal/diagnostic imaging , Tuberculosis, Hepatic/diagnostic imaging , Tuberculosis, Lymph Node/diagnostic imaging , Tuberculosis, Splenic/diagnostic imaging , AIDS-Related Opportunistic Infections/microbiology , Adult , Biopsy, Needle , Female , Humans , Male , Peritonitis, Tuberculous/microbiology , Tuberculosis, Gastrointestinal/microbiology , Tuberculosis, Hepatic/microbiology , Tuberculosis, Lymph Node/microbiology , Tuberculosis, Splenic/microbiology , Ultrasonography
8.
J Ultrasound Med ; 20(7): 729-38, 2001 Jul.
Article in English | MEDLINE | ID: mdl-11444731

ABSTRACT

OBJECTIVE: To report an 11-year experience of treatment of hydatid liver cysts with double percutaneous aspiration and injection of alcohol. METHODS: Of the 129 patients with 174 hydatid liver cysts admitted to our department between January 1988 and January 1999, 79 patients with 119 vital hydatid liver cysts were selected for double percutaneous aspiration and injection of alcohol. Under ultrasonographic guidance, cystic cavities were first drained through fine needles, and then 95% sterile ethanol was injected and left in situ. The same procedure was repeated 3 days later without reaspiration of the injected alcohol. General anesthesia without endotracheal intubation was performed in 21 selected cases. RESULTS: Double percutaneous aspiration and injection of alcohol was completed in 78 patients with 118 hydatid liver cysts. In 1 case the procedure could not be accomplished because of an intracystic hemorrhage. A total of 254 punctures were performed, and the ethanol injected per session ranged between 12 and 250 mL. The mean hospital stay was 2.9 days (range, 2-7 days). The overall median follow-up was 48 months (range, 6-122 months). At the last ultrasonographic examination, 45.8% of the treated hydatid liver cysts had a solid pattern, 47.4% were no longer appreciable, and 6.8% had a minimal liquid component. Intracystic relapse occurred in 5% of the patients. In no case were any new cysts observed either in different hepatic segments or in any extrahepatic location. The morbidity rate was 9%, and 1 death occurred (mortality rate, 1.3%). CONCLUSIONS: Over a long period, double percutaneous aspiration and injection of alcohol proved to be a substantially safe, effective, and low-cost procedure for hydatid liver cyst treatment.


Subject(s)
Alcohols/administration & dosage , Echinococcosis, Hepatic/therapy , Suction/methods , Adolescent , Adult , Aged , Aged, 80 and over , Alcohols/therapeutic use , Cysts/classification , Cysts/diagnostic imaging , Cysts/drug therapy , Echinococcosis, Hepatic/diagnostic imaging , Female , Follow-Up Studies , Humans , Injections, Intralesional , Male , Middle Aged , Ultrasonography
9.
J Ultrasound Med ; 20(11): 1189-95, 2001 Nov.
Article in English | MEDLINE | ID: mdl-11758024

ABSTRACT

OBJECTIVE: To describe echo color Doppler features of mumps epididymo-orchitis in postpubertal boys and men. METHODS: Color Doppler ultrasonographic examinations of the scrotum in 12 patients (14-34 years old) with serologically proven mumps and symptomatic epididymo-orchitis (pain and scrotal swelling) were compared with color Doppler ultrasonographic examinations of the scrotum in 10 healthy control subjects. RESULTS: Clinically evident testicular involvement was bilateral in 1 patient and unilateral in 11 patients (9 left- and 2 right-sided). Four (33.3%) of 12 patients had swelling and a heterogeneous echo texture of the epididymis and hydrocele. Two (16.7%) of 12 patients had swelling of both the epididymis and didymus of the involved side, with a heterogeneous echo texture of the didymus due to hypoechoic, irregularly shaped, confluent intraparenchymal areas. Two (16.7%) of 12 patients had only unilateral mild hydrocele and no testicular abnormalities. In 4 (33.3%) of 12 cases, B-mode ultrasonographic examination did not show any testicular abnormalities or hydrocele. Hydrocele was anechoic in 4 cases and multiseptated in 4. In 12 (100%) of 12 patients, color Doppler and power Doppler ultrasonography showed hypervascularity in the parenchyma of the affected testicle. In 11 patients, spectral Doppler examination of the arteries at the testicular hilum showed a significantly lower mean +/- SD resistive index (0.54 +/- 0.03; range, 0.48-0.57) on the inflamed side compared with the opposite unaffected side (mean, 0.66 +/- 0.04; range, 0.71-0.60) (P < .001). In the patient with bilateral involvement, the mean resistive index values in the right and left testicular arteries were 0.57 and 0.55, respectively. The mean resistive index of the 13 inflamed testicles (0.54 +/- 0.03; range, 0.48-0.57) was significantly different from the mean resistive index values of the right (0.68 +/- 0.03) and left (0.67 +/- 0.04) testicular arteries in healthy control subjects (P < .001). The mean resistive index in the 11 unaffected testicles in our patients (0.66 +/- 0.04; range, 0.71-0.60) was not significantly different from the mean resistive index in healthy control subjects. CONCLUSION. Ultrasonographic findings in mumps orchitis are not specific. Echo color Doppler examination is more sensitive than ultrasonography alone for revealing testicular inflammation.


Subject(s)
Epididymitis/diagnostic imaging , Mumps/complications , Orchitis/diagnostic imaging , Ultrasonography, Doppler, Color , Adolescent , Adult , Case-Control Studies , Epididymitis/etiology , Humans , Male , Orchitis/etiology , Prospective Studies , Scrotum/diagnostic imaging , Sensitivity and Specificity , Testis/blood supply
10.
Radiol Med ; 99(4): 264-9, 2000 Apr.
Article in Italian | MEDLINE | ID: mdl-10884827

ABSTRACT

PURPOSE: The literature studies about interstitial laser photocoagulation of liver tumors mainly deal with the treatment of liver metastasis in patients with normal liver function. We report our personal experience with interstitial laser photocoagulation in patients with liver tumors (mostly cirrhotics with hepatocellular carcinoma). Our aim was to evaluate the short term efficacy of percutaneous interstitial laser photocoagulation in inducing focal ablation of liver tumors and the possible complications in patients with normal and impaired liver function. MATERIAL AND METHODS: Sixty-six patients (52-80 years; 42 men), 47 with 51 hepatocellular carcinoma nodules (diameter = 1.6-6.6 cm; mean 3.1 cm) on cirrhosis (18 in Child-Pugh A class, 24 in B e 5 in C class) and 19 patients with single liver metastasis (17 from colon, 2 from lung carcinoma; diameter = 3.9 cm; mean: 4.5 cm) underwent interstitial laser photocoagulation under ultrasound guidance. Depending on tumor size up to four needles were inserted in the tumor and multiple laser illuminations were performed: in nodules < or = 2 cm a single optical fiber and a single needle insertion were used, in nodules > 2 < 3 cm, 2-3 fibers were used with a single laser illumination, in nodules > 3 < 4 cm, 4 fibers were inserted and two laser illuminations were performed in the same session after 1.5 cm withdrawal of all fibers in the tumor, in nodules > 4 cm 2 sessions with 2 laser illuminations per session were performed. Necrosis of the nodules was evaluated with triphasic Helical CT 7 days after treatment. Patients with incomplete necrosis at CT were treated with additional interstitial laser photocoagulation sessions to attain complete necrosis. RESULTS: Fifty-eight patients underwent a single interstitial laser photocoagulation session, 7 patients 2 session and 1 patient 3 sessions. The range of administered energy per patient was 1200-32,000 Joules (mean: 6700 J). CT showed complete necrosis of 47 nodules in 43 patients with hepatocellular carcinoma and in 15/18 patients with metastasis. Three Child C class patients with mild ascites and hyperbilirubinemia before procedure (nodules O: 1.9, 3.5 and 5.8 cm) dropped out of CT follow-up because of severe liver function impairment with increased ascites and hyperbilirubinemia, associated with transient ileum paraliticus in 1 case. One of these patients died two months after treatment. Two patients with metastasis dropped out of treatment because of complications occurred after the interstitial laser photocoagulation session (1 ileum paraliticus, 1 gastric hemorrhage) and another one refused to continue the treatment.


Subject(s)
Carcinoma, Hepatocellular/surgery , Laser Coagulation/methods , Liver Neoplasms/surgery , Liver/surgery , Postoperative Complications/epidemiology , Ultrasonography, Interventional , Aged , Aged, 80 and over , Biopsy, Needle , Carcinoma, Hepatocellular/diagnostic imaging , Carcinoma, Hepatocellular/physiopathology , Female , Humans , Laser Coagulation/instrumentation , Liver/diagnostic imaging , Liver/pathology , Liver/physiopathology , Liver Neoplasms/diagnostic imaging , Liver Neoplasms/physiopathology , Liver Neoplasms/secondary , Male , Middle Aged , Time Factors , Tomography, X-Ray Computed , Treatment Outcome
11.
Eur J Ultrasound ; 11(3): 181-8, 2000 Jun.
Article in English | MEDLINE | ID: mdl-10874193

ABSTRACT

OBJECTIVE: To evaluate the efficacy and complications of interstitial laser photocoagulation (ILP) under ultrasound (US) guidance as a technique for focal ablation of liver tumors in patients with normal and impaired hepatic function. PATIENTS AND METHODS: A total of 104 patients, 77 with 85 nodules of hepatocellular carcinoma on cirrhosis (29 in Child-Pugh A class, 43 in B e 5 in C class) and 27 patients with hepatic metastases (25 from colon, two from lung carcinoma) underwent ILP under US guidance. Depending on tumor size up to four needles were inserted in the tumor and multiple laser illuminations were performed in one or multiple sessions. Necrosis of the nodules was evaluated with triphasic contrast-enhanced CT. RESULTS: Ninety-four patients underwent a single ILP session and nine patients two sessions. CT showed complete necrosis in 70 out of 85 HCC nodules in 65 treated patients and in 24 out of 31 patients with metastases. Three Child C class patients dropped out the control of efficacy by CT because of severe liver failure associated in one case with transient paralytic ileum. One of these patients died 2 months after treatment. Two patients with metastasis dropped the completion of the treatment because of complication occurred after the ILP session (one paralytic ileum, one gastric haemorrage). CONCLUSIONS: ILP under US guidance is effective in inducing complete necrosis in small and large liver tumors. Nevertheless, ILP can cause severe derangement of liver function in patients with advanced cirrhosis.


Subject(s)
Laser Coagulation , Liver Neoplasms/surgery , Ultrasonography, Interventional , Aged , Aged, 80 and over , Carcinoma, Hepatocellular/diagnostic imaging , Carcinoma, Hepatocellular/surgery , Female , Humans , Liver Neoplasms/diagnostic imaging , Liver Neoplasms/secondary , Male , Middle Aged , Tomography, X-Ray Computed
12.
Radiol Med ; 99(6): 461-4, 2000 Jun.
Article in Italian | MEDLINE | ID: mdl-11262824

ABSTRACT

PURPOSE: To assess the yield of US in the study of salivary glands and other organs involved in post-pubertal mumps. PATIENTS AND METHODS: We examined 68 patients with serologically proven post-pubertal mumps (age range 14-34 years). All patients were symptomatic, with fever and salivary gland swelling in 25 cases, marked hyperamylasemia in 32, epigastric pain in 9, unilateral scrotal swelling and/or pain in 19 cases and acute bronchitis in 1 case. All patients underwent US of salivary glands, neck lymph nodes, abdomen and scrotum with 48 hours of admission. RESULTS: Salivary glands: Parotid and submandibular glands showed normal echotexture in all patients. The parotid glands also showed multiple hypeoechoic intraparenchymal lymph nodes which were, ovoid or rounded, with smooth margins and a central hyperechoic area, with diameter ranging 3-14 mm (mean 5.4). No intraparenchymal lymph nodes were observed in submandibular glands. Neck: All patients had enlarged submandibular lymph nodes (maximum diameter ranging 5-22 mm; mean 11 mm); swelling was always bilateral and it was symmetric in 19/68 patients (30%) versus asymmetric because of prevailing right side involvement (more numerous and bigger nodes) in the other 47/68 cases (70%). All lymph nodes showed a benign pattern, with an ovoid or elongated shape, homogeneous hypoechoic echotexture and a hyperechoic hilum. Abdomen: The pancreas showed normal volume and normal parenchymal echotexture in all patients. Liver and spleen were always normal. Testes: US showed mild unilateral hydrocele in 10 cases, hydrocele and unilateral swelling of epidymis in 5 cases, hydrocele and swelling of both epidymis and didymis with inhomogeneous echotexture because of intraparenchymal hypeoechoic areas in 2 cases. There were no US changes in 2 cases. CONCLUSIONS: US of the salivary glands shows a specific pattern in post-pubertal mumps which has never been reported for other salivary gland diseases. In contrast US signs in other organs are not specific.


Subject(s)
Parotitis/complications , Parotitis/diagnostic imaging , Adolescent , Adult , Age Factors , Female , Humans , Male , Parotitis/epidemiology , Prospective Studies , Ultrasonography
13.
Sci Total Environ ; 223(1): 1-24, 1998 Nov 03.
Article in English | MEDLINE | ID: mdl-9850600

ABSTRACT

In an oxisol-spodosol system developed on the terrestrial surface of the lower Tapajós Valley, the determination of total mercury (Hg), organic carbon (C), iron and aluminum oxy-hydroxide (Fe(cdb) and Al(cdb)) concentrations in the surface soil horizons are used to characterise the geochemical processes controlling the accumulation of Hg in soils under natural vegetation cover and in deforested and cultivated sites. Oxisols from the plateau have homogeneous and relatively high background Hg contents and burdens constituting an important natural reservoir of Hg for the region (90-210 ng/g dry wt. and 19-33 mg/m2 for the first 20 cm). The Fe(cdb) and Al(cdb) contents associated with the fine fraction (< 63 microns) of the soil suggest that oxy-hydroxides and, particularly Al-substituted Fe oxy-hydroxides, control the Hg concentrations observed in all of the soils of the study region. Consequently, the geochemistry of these minerals along the slopes governs the accumulation or the release of the Hg according to the natural evolution of the soil cover and/or following the degradation of soils by erosion after deforestation and cultivation. These observations have important implications for the interpretation of Hg contamination patterns observed in Amazonian aquatic systems that could be linked to different drainage sources of Hg from the terrestrial surface. The sandification and podzolisation that is characteristic of the evolution of numerous pedological systems in the equatorial Amazon could be responsible for exportation of the naturally accumulated Hg, as for other metals, by acidic complexation and migration to the black waters of the Amazon. In the central Amazon region, as a result of the fragility of the soil cover, deforestation and cultivation, affecting principally the superficial soil, promote the selective erosion of fine particles enriched in oxides and Hg. The erosion of soil could be responsible for an important release of Hg, transported in particulate form by drainage waters.


Subject(s)
Mercury/analysis , Soil Pollutants/analysis , Aluminum/chemistry , Brazil , Ecosystem , Geologic Sediments , Hydroxides , Iron/chemistry , Mercury/chemistry
SELECTION OF CITATIONS
SEARCH DETAIL
...