Abstract
The use of sewage sludge and effluent as a source of nutrients and water for crop production is increasing worldwide. A study was conducted in 2001 at Pension farm (near Harare) to determine the effect of long term (>30 yrs) application of sewage sludge and effluent on Zn and Cu accumulation in top soil, uptake of these metals by lettuce (Lactuca sativa L.) and mustard rape (Brassica juncea L.), and dry matter yield. Application of sewage sludge/effluent significantly (p<0.001) increased total Zn (13.7-1563.9 mg kg(-1)) and Cu (2.5-133.3 mg kg(-1)) in the top soil (0-20 cm depth) compared to the control. Sewage sludge/effluent addition significantly (p<0.001) increased Zn uptake by both test crops, while Cu uptake was significant in the first crop of lettuce and the second crop of mustard rape. Based on the dietary patterns of poor urban households in Zimbabwe, the maximum possible intake of Cu will only constitute 40% the Maximum Daily Intake (MDI). The toxicological implications for Zn will however be more severe, exceeding the MDI by 77% through exposure by lettuce consumption and by 251% consumption of mustard rape. It was concluded that long-term addition of sewage sludge/effluent to soil at Pension farm had increased the concentration of Zn and Cu in top soil to levels that pose environmental concern. The consumption of leafy vegetables produced on these soils pose a health risk to poor communities that reside around the study site, especially children, through possible Zn toxicity.
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Claims 8
Claim · model-written summary
Sewage sludge/effluent application significantly increased total soil Zn relative to the control.
- Treatment
- sewage sludge/effluente1
- Outcome
- total Zne1
- Direction
- increasede1
- Value
- 13.7-1563.9 mg kg(-1)e1
- Qualifier
- top soil (0-20 cm depth)e1
- Comparator
- controle1
- Setting
- Pension farm (near Harare)e2
Not reportedTaxon
Verbatim
e1“Application of sewage sludge/effluent significantly (p<0.001) increased total Zn (13.7-1563.9 mg kg(-1)) and Cu (2.5-133.3 mg kg(-1)) in the top soil (0-20 cm depth) compared to the control”
e2“A study was conducted in 2001 at Pension farm (near Harare)”
Claim · model-written summary
Sewage sludge/effluent application significantly increased total soil Cu relative to the control.
- Treatment
- sewage sludge/effluente1
- Outcome
- Cue1
- Direction
- increasede1
- Value
- 2.5-133.3 mg kg(-1)e1
- Qualifier
- top soil (0-20 cm depth)e1
- Comparator
- controle1
- Setting
- Pension farm (near Harare)e2
Not reportedTaxon
Verbatim
e1“Application of sewage sludge/effluent significantly (p<0.001) increased total Zn (13.7-1563.9 mg kg(-1)) and Cu (2.5-133.3 mg kg(-1)) in the top soil (0-20 cm depth) compared to the control”
e2“A study was conducted in 2001 at Pension farm (near Harare)”
Claim · model-written summary
Sewage sludge/effluent addition increased Zn uptake by lettuce and mustard rape.
- Taxon
- lettuce (Lactuca sativa L.) and mustard rape (Brassica juncea L.)
Brassica juncea
Lactuca sativae4 - Treatment
- Sewage sludge/effluent additione3
- Outcome
- Zn uptakee3
- Direction
- increasede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“Sewage sludge/effluent addition significantly (p<0.001) increased Zn uptake by both test crops”
e4“uptake of these metals by lettuce (Lactuca sativa L.) and mustard rape (Brassica juncea L.)”
Claim · model-written summary
Cu uptake by lettuce in the first crop was significant under sewage sludge/effluent addition.
- Taxon
- lettuceLactuca sativae5
- Treatment
- Sewage sludge/effluent additione3
- Outcome
- Cu uptakee5
- Qualifier
- first crope5
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“Sewage sludge/effluent addition significantly (p<0.001) increased Zn uptake by both test crops”
e5“Cu uptake was significant in the first crop of lettuce and the second crop of mustard rape”
Claim · model-written summary
Cu uptake by mustard rape in the second crop was significant under sewage sludge/effluent addition.
- Taxon
- mustard rapee5
- Treatment
- Sewage sludge/effluent additione3
- Outcome
- Cu uptakee5
- Qualifier
- second crope5
Not reportedComparatorDirection
Verbatim
e3“Sewage sludge/effluent addition significantly (p<0.001) increased Zn uptake by both test crops”
e5“Cu uptake was significant in the first crop of lettuce and the second crop of mustard rape”
Claim · model-written summary
Zn exposure through lettuce consumption exceeds the MDI by 77%.
- Taxon
- lettuceLactuca sativae6
- Outcome
- exceeding the MDIe6
- Value
- 77%e6
- Qualifier
- toxicological implications for Zne6
- Comparator
- MDIe6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e6“The toxicological implications for Zn will however be more severe, exceeding the MDI by 77% through exposure by lettuce consumption and by 251% consumption of mustard rape”
Claim · model-written summary
Zn exposure through mustard rape consumption exceeds the MDI by 251%.
Verbatim
e6“The toxicological implications for Zn will however be more severe, exceeding the MDI by 77% through exposure by lettuce consumption and by 251% consumption of mustard rape”
Claim · model-written summary
The maximum possible Cu intake from these vegetables is about 40% of the Maximum Daily Intake.
Verbatim
t0“Leafy Vegetables”
e7“Based on the dietary patterns of poor urban households in Zimbabwe, the maximum possible intake of Cu will only constitute 40% the Maximum Daily Intake (MDI)”
The same questions in other papers
organic · nutrient: content · Brassica juncea (Indian mustard)Positive and negative results
3 in the opposite direction
- positive
- positive
- positive
organic · nutrient: content · Lactuca sativa (garden lettuce)Positive and negative results
6 papers in the same direction as this paper · 14 in the opposite direction
- positive
- positive
- positive
17 papers more in this group
See all 21 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.