Danau Kualitas Air Danau Memahamai information kualitas air danau dan interpretasi data Byron Shaw, Lowell Klessig, Christine Mechenich
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Outline • Danau • Kualitas Air Danau – Fisik – Perkembangan danau
• Pencemaran Air Danau • Monitoring Air Danau
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Danau Akumulasi air dari presipitasi,sungai, run off, dan air tanah. Macam Danau alam 1. Tanpa ada aliran keluar (seepage) 2. Mengalir ke sungai (air tanah) 3. Mengalir ke sungai (drainase) Danau buatan Dam bendungan air sungai 1/26/2016
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SEEPAGE LAKE – Air danau alam berasal dari presipitasi, runoff dan air tanah. Tidak mengalir ke sungai (outlet)
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GROUNDWATER DRAINAGE LAKE – Air danau alam berasal dari air tanah, presipitasi, dan runoff. Ada aliran sungai (outlet).
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DRAINAGE LAKE – Air danau berasal dari sungai, air tanah, presipitasi, runoff, dan mengalir ke sungai.
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IMPOUNDMENT – danau buatan (Dam) membendung sungai. Air mengalir melalui air sungai (outflow).
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Kualitas air danau Karakteristik air setiap danau: • berlainan; fisik, kimia, dan biologis ; • kimia setiap hari berubah; • biologis, spt. alge berubah menurut musim
Perubahan kualitas air karena o o o o o 1/26/2016
runoff air tanah, presipitasi, temperatur energi sinar matahari. 8
Lanjutan slide 8 Contoh,penurunan oksigen (DO) berakibat: • kematian ikan, populasi ikan berkurang • meningkatkan air menjadi lebih jernih • populasi ikan berkurang, zooplankton bertambah banyak, populasi alge berkurang, terjadi perubahan kualitas air
•Dokumen ini membahas karakteristik fisik dan kimia berbagai jenis danau termasuk: • status nutrient ( kondisi tropik) dan hujan asam; • akumulasi metal beracun pada ikan dan dasar perubahan kualitas air • beberapa istilah riset kualitas air danau (limnology). 1/26/2016
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Karakteristik Fisik Permukaan air danau mempengaruhi kualitas air: Permukaan air rendah menekan kehidupan ikan meningkatkan jumlah kesuburan tanaman air Permukaan air tinggi, nutrient bertambah dari runoff banjir menyapu lapiran tanah. erosi tanah pantai. Parameter fisik: kejernihan, warna, turbidity
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Kejernihan Air Jernih bukan karakteristik kimia Indikator terkait karakteristik kimia dan fisik Komponen kejernihan air: – Warna (padatan/bahan terlarut (dissolved ) – Turbidity (bahan suspended :alge,pasir/ silt. Populasi alge merupakan komponen terbanyak dan bervariasi
Pengukuran kejernihan air: Secchi disc
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Pengukuran Secchi disc piringan d 8-inch; warna hitam putih; terikat dengan tali panjang 50-100 m; dimasukan ke dalam air sampai tidak terlihat; ditarik sampai terlihat piringan hitam putih mengukur kedalaman air dan kejernihan Pengukuran rata-rata kedalaman pada: kondisi tenang, angin dan sinar jam 10-14; kondisi angin dan teduh; Kedua kondisi mempengaruhi hasil pengukuran
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Lanjutan sliden 12 Secchi disc mengukur :
–populasi alge tinggi dan rendah –nutrient dari tahun ke tahun – perubahan kejernihan air jangka panjang. Kejernihan
Kedalaman
Sangat jelek
2
Jelek
5
Sedang
7
Baaik
10
Sangat baik
20
Excellent
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Danau berwarna ? menunjukkan adanya larutan kimia organik,jenis&jumlah penetrasi sinar matahari berkurang pertumbuhan tanaman air/weed dan alge Banyak danau memiliki karakteristik alam, berwarna: karena adanya asam humic and tannic dari dekomposisi materi tanaman pada watershed. Warna coklat berasal dari buangan bogs ke danau . Sebelum /selama dekomposisi alge berubah menjadi hijau, coklat, dan merah. 1/26/2016
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Lanjutan slide 14 Warna air mempengaruhi ukuran Secchi disc. Warna air 0-40 units 40-100 units >100 units
Rendah Sedang Tinggi
Turbidity (kekeruhan) Parameter lain mengukut kejernihan” disebabkan lebih banyak butiran komponen organik yang. Ini berakibat sinar matahari terhalang kedalam air dan pertumbuhan tanaman air. 1/26/2016
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Lanjutan slide 15 Alge : – alamiah penting, tetapi kalau – terlalu banyak menjadi masalah.
Kejernihan air menunjukkan: – kualitas air danau: – adanya alge.
Chlorophyll a –Mengkur algae pada setiap danau
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Kondisi Danau
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Lanjutan slide Kondisi danau 3 kategori, berdasar nutrient dan tingkat kejernihan . Oligotrophic : jernih, dalam, taa weeds, taa algae blooms, indah, nutrients rendah, mengukung kehidupan ikan, food chain terpelihara . Eutrophic: tinggi nutrients, mendukung kehidupan organisme besar. Weedy ,sering algae blooms, mendukung kehidupan populasi ikan besr, rentan kekurangan O2 . Kecil dangkal, kematian ikan, kurang variasi jenis ikan, Ikan preman ada disini 1/26/2016
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Lanjutan slide Mesotrophic : karakteristik antara fase oligotrophic and eutrophic stages. Pada musim panas devoid oxygen, hypolimnions limit cold water fish, karena siklus pospat dari sedimen.
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Lanjutan slide Proses penuaan danau,oligotrophic- eutrophic. Percepatan proses eutrophication:
polusi limbah pertanian, nutrients, limbah pupuk, limbah jalanan, limbah septic systems, and segala macam limbah masuk danau.
Daerah kurang nutrient, cenderung menjadi danau dystrophic dan bog sangat berwarna, asam, dan tidak produktif seperti danau eutrophic .
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Lanjutan slide Metode menghitung kondisi tropok danau: –kosentnrasi total pospat (pertumbuhan alge) –kosentrasi chlorophyll ( adanya alge ) –Secchi disc readings (indikator kejernihan air).
Kondisi tropik berkaitan dengan: – kosentrasi pospat rendah; – pertumbuah alge rendah(chlorophyll a); – Secchi disc nilai tinggi. 1/26/2016
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Contoh Kondisi tropik dnau di Wisconsin Lakes, pengukuran chlorophyll a, kejernihan, and nilai total pospat. Klas Danau
T-PO4 ug/l
Clorophyl a ug/l
Secchi Disc feet
Oligotrphic
3 10
2 5
12 8
Mesotropic
16 27
8 10
6 6
Eutropic
30 50
11 15
5 4
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Karakteristik Kimia Pospat • pertumbuhan tanaman air • nutrient untuk pertumbuhan alge dan rumput. • sumber dari kegiatan manusisa –limbah manusia dan hewan, –erosi tanah, –detergents, –sistem septik, dan –runoff from dari tanah pertanian dan perkebunan.
Analysis –Larutan reaktif popspat dilarutkan pada air membantu pertumbuhan tanaman air. – total pospat indikato status nutrient lebihs stabil dari reakti fpospat. 1/26/2016
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lanjutan slide Kosentrasi Pospat: larutan pospat dalam air diukur: –milligrams per liter (mg/l). –micrograms per liter (ug/l). One milligram per liter = one part per million (ppm). Convert: 30 ug/l = 0.03 mg/1); 0.5 mg/l = 500 ug/l); Microequivalents per liter (ueq/l) is also sometimes used, for alkalinity. It is calculated by dividing the equivalent weight of the compound by 1000 and then dividing that number into the milligrams per liter.
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Algae blooms: Pencegahan (summer): –Kosentrasi T-PO4 agar 10 ug/l atau < pada saat perubahan iklim. –Kosentrasi 10 ug/l micrograms per liter is equal to 10 parts per billion (ppb) or 0.01 milligrams per liter (mg/l). –Kosentrasi total pospat kurang dari 20 ug/l for danau and 30 ug/l for impoundments should be maintained to prevent nuisance algal blooms 1/26/2016
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Natural lakes and impoundments
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Lanjutan slide Phosphorus tidak mudah larut dalam air Membentuk partikel dengan Ca, Fe, Al Dalam air keras: dimana mineral batuan (limestone) dalam air, terbentuk CaCO3 dan mengendap dalam pada dasar air, kemudian menyerap pospat, dan mengurangi kosentrasi pospat spt halnya algae bloom is dissolved in the water, calcium carbonate precipitates and falls to the bottom,absorb phosphorus, reducing its overall concentration as well as algae growth. Aquatic plants with roots in the marl bottom still get phosphorus from sediments. Hard water lakes often have clear water, but may be weedy. Iron forms sediment particles that store phosphorus-but only if oxygen is present. When lakes lose oxygen iron and phosphorus again dissolve in water. Strong winds may mix iron and phosphorus with surface water. For this reason, algae blooms may still appear in lakes for many years even if1/26/2016 phosphorus inputs are controlled. 27
Nitrogen CHEMICAL PROPERTIES •important nutrient for plant and algae growth •Sources: –exceed 0.5 mg/l in rainfall, precipitation may be the main nitrogen source for seepage and some drainage lakes. –come from fertilizer –animal wastes on agricultural lands, –human waste from –sewage treatment plants or –septic systems, and –lawn fertilizers used on lakeshore property. –surface runoff –groundwater sources.
•Nitrogen exists in several forms – nitrate (NO3-) plus nitrite (NO2-), –anunonium (NH4+), and –organic plus ammonium (Kjeldahl nitrogen). –Total nitrogen is calculated by adding nitrate and nitrite to Kjeldahl nitrogen. –Organic nitrogen is often referred to as biomass nitrogen. – does not occur naturally in soil minerals, – major component of all organic (plant and animal) matter. –Decomposing organic matter releases ammonia, which is converted to nitrate if oxygen is present. This conversion occurs more rapidly at higher water temperatures. –All inorganic forms of nitrogen (NO3-, NO2- and NH4+) can be used by aquatic plants and algae. –If these inorganic forms of nitrogen exceed 0.3 mg/l (as N) in spring, there is sufficient nitrogen to support summer algae blooms.
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Sources&cycling of nitrogen in a lake
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•Various ways nitrogen enters&cycles in a lake. •Sediments cause nitrogen to undergo a number of changes. •Nitrogen recycled back into overlying water at spring and fall turnover will often increase ammonia levels •Nitrogen can be lost from the lake to the atmosphere by denitrification •This only occurs if oxygen is depleted, nitrate converts back to nitrogen gas.
•Nitrogen (rather than phosphorus) limits algae growth.when the ratio of total nitrogen to total phosphorus is less than 10:1.(10:1 -15:1 transitional) lakes with values greater than 15:1 are considered phosphorus limited-algae growth •Low nitrogen levels do not guarantee limited algae growth in the same way low phosphorus levels do. •Nuisance blue-green algae blooms are often associated with lakes that have low nitrogen to phosphorus (N:P) ratios. •These algae use atmospheric nitrogen gas (N2) dissolved in lake waters as a nitrogen source; other more desirable types of algae and plants depend on the inorganic nitrate and ammonium forms of nitrogen. •Page - 11 •Larger plants also need nitrogen and may depend on spring runoff for septic systems to recharge the sediments with nitrogen. •Growth of Eurasian milfoil has been correlated with such fertilization of the sediment.
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Chloride •The presence of chloride (Cl-) indicates possible water pollution. •Chloride does not affect plant and algae growth •ot toxic to aquatic organisms •Chloride is not common in soils, rocks or minerals, except in areas with limestone deposits. •Sources: –septic systems (chloride 50 to 100 mg/l are common in septic tank effluent), –animal waste, –potash fertilizer (potash = potassium chloride), –and drainage from road-salting chemicals. –Increases in chloride, either seasonally or over time, can mean that one or more of these sources is affecting the lake.
•An increase in chloride from human or animal waste suggests that other nutrients are also entering the lake. Higher chloride concentrations from spring to fall may be the effect of lawn fertilizer runoff or septic systems during heavy use by summer residents. 1/26/2016
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Sulfate •related to the types of minerals found in the watershed and to acid rain • Industries and utilities that burn coal release sulfur compounds into the atmosphere that are carried into lakes by rainfall. •In water depleted of oxygen (anaerobic water), sulfate can be reduced to hydrogen sulfide (H2S). •Hydrogen sulfide gas smells like rotten eggs and is toxic to aquatic organisms. •The sulfide ion (S--) produced under these conditions can also affect the amount of metal ions in the lake since most metals, including iron and mercury, form insoluble sulfide precipitates. •High sulfate content , iron often exists in lower concentrations in lakes because it precipitates and settles out in sediments as iron sulfide.
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Sodium and potassium •Natural levels of sodium&potassium ions in soil and water very low, •Their presence indicate lake pollution caused by human activities. •Sodium is often associated with chloride. •Sources: –road salt, –fertilizers, –and human and animal waste.
•Potassium commonly-used potash fertilizer, abundant in animal waste. •Soils retain sodium and potassium to a greater degree than chloride or nitrate; not as pollution indicators. •Increasing sodium and potassium values over time mean long-term effects caused by pollution. •Not toxic but indicate contamination from more damaging compounds.
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DISSOLVED GASES Three gases in the air are important to lake ecosystems : –oxygen, –carbon dioxide and –nitrogen
Factors determine the amount of gases in a lake: –wind mixing, brings watercontact with atmosphere –the biological activity that consumes or produces gases within a lake; and –gas composition of groundwater and surface water entering a lake. 1/26/2016
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Oxygen Gas paling penting – sebagian besar organisme air perlu O2 – Kelarutan tergantung dari t air. – semakin dingin air mengikat lebih banyak O2. – Air panas memisahkan gas oksigen – Efek oxygen pada t. Temperature Deg.C 0 5 10 15 20 25
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Deg.F 32 41 50 59 68 77
O2 solubility (mg/l) 15 13 11 10 9 8
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lanjutan slide 35 Kadar O dalam air danau terjadi karena reaksi air dan oksigen dalam atmosfer ( 21 % oxygen) terjadi terus. Kadar oksigen berbeda diberbagai lokasi karena percampuaran. Es menutup reaksi pencapuran atmosfeer dan air. Reaksi biologis memerlukan atau melepas oxygen. Oxygen dihasilkan oleh petumbuhan tanaman hijau.
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lanjutan slide 35 Tanaman menggunakan CO2 dan menghasilkan gula/ten aga , menggunakan sinar matahari sebagai sumber energi. Chlorophyll, pigmen hijau pada atanaman menyerap sinar matahari terjadi proses fotosintesis menghasilkan oxygen
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Fotosintesis dan Respirasi
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Lanjutan slide Fotosintesis – siang hari dan sinar matahari menembus kedalaman air. – tergantung adanya tanaman air, nutrient, dan temperatur. – t tinggi mempercepat proses .
Respirasi tanaman dan hewan menggunakan oxygen dan memecah gula menjadi energi – proses sebaliknya fotosintesis – pembakaran minyak atau bahan organik lain beruap reaksi kimia respirasi, melepas carbon dioxide (CO2) ke amosfeer. –
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Lanjutan slide •Kombinasi kedua reaksi menentuka kadar O2 dan CO2 di danau menurut waktu dan kedalaman berbeda. •Siang hari,permukaan air O2,berlebih supersaturation •Malam hari /pagi mulai fotosintesis O2 rendah. •Bagian dalam tidak tembus sinar matahari, hanya terjadi respirasi. • Danau hypolimnic sering kurang oxygen. • Danau dengan banyak tanaman dan hewan kegiatan biologis lebih banyak dibandingkan yang tidak. 1/26/2016
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Status O2 dan Nutrient pada danau mesotrophic and eutrophic •Low O2:the hypolimnion, fish must live in the epilimnion and metalimnion. •Fish (trout): need high O2 and cool water disappear from such lakes. •Winter oxygen depletion (winterkill): four inches of snow cover the lake, which prevents sunlight from reaching the water. All photosynthesis stops and plants begin to die and decompose. Oxygen loss depends on amount of plant, algae and animal matter that decays. •Drought increases the chance of winterkill by reducing the volume of water in the lake. •The water quality standard in "warm water" lakes and streams is 5 mg/l. This is the minimum amount of oxygen needed for fish to survive and grow. •The standard for trout waters is 7 mg/l. • A smart angler would know that the lake contains no trout and that it would be silly to fish for walleye in the deep holes in late summer. 1/26/2016
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Fotosintesis dan Respirasi
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Gas Lain Gas dalam air: Kondisi anaerobic conditions: hydrogen sulfide (H2S); methane gas (CH4);
Gas berasal dari sediments, "swamp gases," hydrogen sulfide and methane terlihat sebagai busa air pada sedimen,dangkal,dan comberan Gas H2S berbau telur busuk dan beracun bagi ikan 1/26/2016
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Sistem Carbonate Siste karbonat merupakan: •Kimia kejadian alam yang mempengaruhi dasar prfoduktifitas biologis, •Menetukan sifat dan kemampuan pengaruh keasaman air danau, dan •Mengatur kelarutan banyak bahan kimia toksik. M empengaruhi perubahan konstan pada kegiatan biologis, pada • perubahan temperature, • sinar matahari, and • gelombang yang aneh.
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pH-acidity Indek keasaman air danau: pH komponen penting sistem karbonat kosentrasi ion hydrogen (H+) terkait jumlah ion hydrogen dalam air. pH rendah lebih banyak ion hydrogen,lebih asam dpd pH tinggi. pH 7 netral. Air pH 7 mempunyuai jumlah ion H+ sama dengan ion (OH-) Air distillasi tanpa carbon dioxide mempunyai pH 7.
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Persamaan
•pH ranges from 4.5 in some acid lakes to 8.4 in hard water •For every 1.0 pH unit, the hydrogen ion concentration changes tenfold. •A lake with a pH of 6 is ten times more acid (ten times as much H+) than a lake with a pH of 7. •Water with a pH 5 has 100 times as many hydrogen ions (H+) as pH 7. •Lakes with a pH of 8 have one-tenth as many hydrogen ions as water with a pH of 7. •The measure of the hydrogen ion (acid) concentration in water is called pH. •A pH 7 neutral. Values above 7 are alkaline or basic. Those below 7 are acidic. A change of 1 pH unit is a tenfold change in acid level. Iron may also be found in high levels in acidic water. 1/26/2016
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pH meter
pH rendah tidak selalu berbahaya kehidupan ikan, Logam berat ada dalam air pH rendah penting. Kosentrasi aluminum, zinc and mercury meningkat bila ada pada sedimen air dan tanah watershed.
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