Dep. Manajemen Sumberdaya PerairanFakultas Perikanan dan Ilmu Kelautan - IPB

ESSENTIAL NUTRIENT

Tucker, MR. 1999. Essential Plant Nutrients: their presence in North Carolina soils and role in plant nutrition

C

biomass-limiting nutrients: membatasi produksi biomass

rate-limiting nutrients: membatasi laju produktivitas primer

diffusive boundary layer

urea

• bakteri tertentu• blue-green algae

N2

NO3

NH4+

nitrogen also plays important roles in other water quality processes and may constitute a problem:

1. The oxidation of NH4 to NO3 during the nitrification process consumes oxygen and may contribute significantly to the oxygen depletion of a waterbody.

2. High concentrations of un-ionized NH3 can be toxic to aquatic life.

3. The common form of nitrogen in water is NO3, which itself is not toxic. However, bacteria in the intestinal tract of infants can convert nitrates to highly reactive NO2, which may cause the so-called “ blue baby ” syndrome and death from suffocation. There are strict regulations governing the amount of nitrate that can be present in drinking water.

nitrogen is not as often limiting to plant growth as phosphorus in many natural waters, especially in freshwaters. Thus, most of the eutrophica-tion management efforts are focused on phosphorus control.

Nitrogen di perairan terdapat dalam berbagai bentuk seperti:

Reaksi kesetimbangan amonia dan amonium:

1) NO3- (Nitrat)

2) NO2- (Nitrit)

3) gas N2 terlarut4) NH3 (Ammonia) – gas terlarut5) NH4

+ (ion Ammonium), dan 6) N organik kompleks – dlm jumlah besar

(org N)

1. N2 (g) + O2 (g) 2 NO (g)

2. 2 NO (g) + O2 (g) ----> 2 NO2 (g)

3. 3 NO2 + H2O ----> 2 H+ + 2 NO3- + NO

4. NH3 + H2O NH4OH NH4+ + OH-

Respirasi Nitrat (denitrifikasi):

5. 2NH4+ + 3O2 2NO2

- + 4H+ + 2H2O

6. 2 NO2- + O2 2 NO3

-

Nitrifikasi: melibatkan bakteri nitrifikasi• Nitrosomonas• Nitrobacter

Total Nitrogen (TN):

Total Kjeldhal Nitrogen (TKN):

Total Amonia Nitrogen (TAN) atau TA:

[ ] = konsentrasi (mol/L atau mg/L)

N-organik

total amonia

Ammonia Ammonia

Phenol dan hypochlorite (chlorox) bereaksi dalam kondisi larutan basa membentuk phenylquinone-monoimine yang selanjutnya akan bereaksi dengan ammonia membentuk indophenol yang berwarna biru. Kepekatan warna biru sebanding dengan kadar ammonia yang ada.

Phenol + NH3 + 3ClO- ‑‑‑‑> Indophenol + 2H2O + OH- + 3Cl-

(Hypochlorite) (biru)

kondisi alkalin/basaSemua amonia(NH3 & NH4

+)NH3

Ammonia - NAmmonia - N

Sig

id H

ariy

adi

Phenol + Hypochlorite ⇨ phenylquinone-monoimine + NH3 ⇨Indophenol (biru)

metoda Indophenol (=metoda phenate)metoda Indophenol (=metoda phenate)

( Utk sampel air dgn kesadahan < 400 mg/L dan berkadar NO2-N < 5 mg/L)

setiap set penentuan ammonia, harus selalu disertai dengan penentuan standar ammonia dan blanko Kadar ammonia yang terukur pada metoda ini adalah ammonia total yaitu terdiri dari NH3 dan NH4

-, karena pada larutan bersuasana basa kuat semua ammonia berada dlm bentuk NH3 TAN

Prosentase NH3 thd ammonia total (TAN) sangat dipengaruhi oleh:• pH

• temperatur • salinitas air payau & air laut

Sumber: Trussel (1972) in Boyd (1979)

Sig

idH

ari

yad

i

Total Ammonia Nitrogen

% NH3 = 100

1 + antilog (pKa – pH)

% un-ionized ammonia:

15 20 22 24 25 26 27 28 29 30

9,56 9,40 9,33 9,27 9,24 9,21 9,18 9,15 9,12 9,09

31 32

9,06 9,03

Temp (oC)

pKa

pKa = -log (Ka)

Ka : konstanta ionisasi

Amonia dan Amonium:

[ ] = konsentrasi (mol/L)

Konstanta kesetimbangan amonia Ke dipengaruhi oleh temperatur (T):

T dalam C pada 25 C

Proporsi amonium thd total amonia (TA):

Proporsi amonia thd total amonia (TA):

total amonia

Sig

idH

ari

yad

i –

20

11

Sig

idH

ari

yad

i –

20

11

Oligotroph Mesotroph Eutroph Hipertrophi

Total P (μg/l) 3.00 -17.7 (8.00)

11.0-95.6 (26.7)

16.2-386 (84.4)

750-1200

Total N (μg/l) 307-1630 (661)

361-1387 (753)

393-6100 (1875)

-

chl-a (μg/l) 0.30-4.50 (1.70)

3.0-11.0 (4.70)

2.70-78.0 (14.3)

100-150

Max chl-a (μg/l)

1.30-10.6 (4.20)

4.90-49.5 (16.1)

9.50-275 (42.6)

-

Secchi disk (m)

5.40-28.3 (9,90)

1.50-8.10 (4.20)

0.80-7.00 (2.45)

0.4-0.5

Di dalam sampel plankton, rasio atom = 106 C : 16 N : 1 P

N-P ratio sediaan nutrien bagi perkembangan algae

Normalnya Normalnya ⇨⇨16 atom N : 1 atom P7.2 mg/L N : 1 mg/L P

““Biologically available” Biologically available” NN = nitrat + nitrit + ammonia = nitrat + nitrit + ammonia

““Bio-available” Bio-available” PP = orthophosphate = orthophosphate

konsentrasi dari masing-masing N dan P tetap perlu diketahui

Bila N-P ratio < 7 ⇨N potensial sbg faktor pembatas

Bila N-P ratio > 8 ⇨P potensial sbg faktor pembatas

Redfield ratio (1963)

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